Thermoelectric and Co-Generation Technologies

Authored by: Alexander V. Dimitrov

Introduction to Energy Technologies for Efficient Power Generation

Print publication date:  February  2017
Online publication date:  April  2017

Print ISBN: 9781498796446
eBook ISBN: 9781315156170
Adobe ISBN:

10.1201/9781315156170-3

 

Abstract

This chapter discusses some energy-conversion technologies where heat is directly converted into electricity or is a previously created product by energy conversions. We shall analyze the following technologies:

Conversion of solar radiation into electricity (so-called “internal ionization”)

Seebeck technology applied in thermos-couples (so-called “thermoelectric current”)

Schonbein/Grove technology with oxidation control

Rankine cycle technology

Brayton cycle technology

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Thermoelectric and Co-Generation Technologies

This chapter discusses some energy-conversion technologies where heat is directly converted into electricity or is a previously created product by energy conversions. We shall analyze the following technologies:

  • Conversion of solar radiation into electricity (so-called “internal ionization”)
  • Seebeck technology applied in thermos-couples (so-called “thermoelectric current”)
  • Schonbein/Grove technology with oxidation control
  • Rankine cycle technology
  • Brayton cycle technology

Historically, static electricity* was known since medieval times and much earlier (Thales described some static electricity effects in the seventh century bc). By mid-16th century however no one in Europe distinguished electricity from magnetism. This was done by Gerolamo Cardano (1501–1576) in his treatise, thus stimulating the interest of other European researchers in the phenomenon and laying the foundations of electric generator design. Following the invention activity in the field, we may outline two methods of heat-electricity conversion:

  • Direct method (DTEG-direct thermoelectric generation)
  • Indirect method (InDTEG)

Technologies using internal ionization and barrier semiconductor layers resulted from the first method, including photovoltaic cells which operate using radiation of hot bodies (the Sun especially), as well as thermoelectric converters exploiting the Seebeck effect for direct conversion of heat into electricity. Other technologies of the same type are those applied in fuel cells (FCs),§ where electricity is generated during a controlled process of oxidation of gaseous hydrocarbon fuels, such as natural gas, syngas, hydrogen, etc.

Currently, the second group of technologies (InDTEG) dominates in all industrial installations for central generation of electricity in electric power stations. Their characteristic feature is the performance of a cascade of intermediate energy conversions (see Section 1.1.6). For instance, burning (uncontrollable oxidation) generates heat as a first step. Then the heat is converted into mechanical energy of the kinematic chains of internal or external heat engines, which are aggregated to the electric generators. Finally, the generators convert the available kinetic energy of the rotating or translating electric induction devices* into electricity.

Some modifications of InDTEG are the so-called nuclear and solar technologies which convert radiation (resulting from the nuclear decay of processed uranium or coming from the Sun) into heat carried by superheated steam, and the heat is finally converted into electricity.

3.1  Direct Thermoelectric Technologies

3.1.1  Internal Ionization of Bodies and Photovoltaic Cells

To clarify the mechanisms of internal ionization of bodies one must remember the principle of operation of Einstein atomic oscillators in a crystal lattices (see in Figure 1.2), considering the zone theory of atom and molecule structure. Accordingly, the electrons of each atom occupy different orbits (energy orbitals). Their passage from one to another orbital would be possible if only the electron receives or releases discrete portions of energy called quanta. The number of electrons in an orbital around the atomic nucleus is also limited (not more than two electrons in the first orbital, not more that eight electrons in the second one, and then not more than 18, 32, 50, etc. electrons). The last and remotest energy orbital is called valence band, and it is not filled with electrons.

Electrons may leave their orbits, break free from their atoms and exist independently (move within the interatomic space) forming an electron gas. To start a free motion, valence band electrons should overcome the energy barrier of the “banned zone” (the last energy hole between the quantum orbitals, which the electrons should “jump over” prior to their complete emancipation from the atoms). The process of the electron's “jumpover” the banned zone and shift to the free zone is known as “lattice internal ionization,” since atomic nuclei are converted into positive ions (anions). A “hole or vacancy” is formed as a replacement of an electron (it behaves as a positive charge—positron).

Solids, being medium where energy conversions take place, can be classified into three groups, depending on the “width” of the banned zone and on the possibilities of “jump over”

  • Insulators (additional energy exceeding 5 eV are needed to overcome the energy gap of the banned zone)
  • Semiconductors (the banned zone is narrow Eg < 5 eV)
  • Conductors (the electrons of the valence band pass freely to the free area, since no banned zone exists in the valence band and in the free area—both energy orbitals merge)

Semiconductors are the most interesting for devices converting energy. The energy barrier of their banned zone is easily overcome using “natural” energy carriers, that is, solar radiation photons or those emitted by bodies heated in a combustion chamber (CC). Their energy is proportional to the fourth degree of temperature—T4 (the law of Stefan–Boltzmann). This is clear from the comparison between Table 3.1 and Figure 3.1.

Examples of overcoming the banned zone.

Figure 3.1   Examples of overcoming the banned zone.

Table 3.1   Width of Banned Zone for Different Semiconductors in еV

Substance

Si

Ga

Sn

GaAs

InSb

HgSe

InP

GaP

ZnSe

Width of the banned zone, eV

1.107

0.67

0.08

1.35

0.165

0.3

1.27

2.24

2.58

The energy-converting medium specified in Table 3.1 belongs to the group of semiconductors with narrow “banned” zones. It is seen that they have very low energy barriers of the banned zone varying in the range 0.08–2.58 eV. On the other hand, Figure 3.1 illustrates the energy of the “solar” photons and their ability to displace electrons from the valence band depending on the wave number of the carrying orbitals.

It is seen in the figure that orbitals with wavelength within ranges 350 < λPh < 760 nm possess the largest number of photons, and hence—the greatest energy charge. They form the visible part of the solar spectrum. Photon energy charge is within limits 1.7 < ePh < 3.1 eV. The energy is sufficient (see Table 3.1) for valence electrons move over the banned zone and leave as a cloud of free electrons. At the same time, the atomic lattice of the body is ionized within the area which the photon stream falls on (part of the body external surface).

Although the phenomenon was already known in the first half of the 19th century, inventors did not manage to design a direct converter of solar energy into electricity. The first photosensitive element was developed 130 years ago, and it became clear that the direction of research was correct. Yet, the research “break through” was made during the 1950s using the so-called “n–p”—silicon semiconductors which were the first devices to successfully convert solar energy into electricity.

What is the construction of a silicon semiconductor and how does it operate under solar photon radiation?

Figure 3.2a–c presents as an illustration three structures of atomic lattices built on a silicon basis. The difference between them is evident when comparing the first structure to the second and the third ones. It is seen that when an atom from the natural configuration of the silicon lattice is replaced by an atom with higher valence (phosphorus from group V, for instance) an extra valence is left within the lattice (an extra atom). A similar result occurs when replacing an atom from a lower atomic group (as in Figure 3.2c—Boron from group III). Then, an atom abandons the crystal structure leaving a so-called “hole or vacancy.” It is assumed that bodies with such an atomic structure should be called bodies with “n” and “p” electric conductivity, due to electron excess and shortage.

Photovoltaic structures: (a) silicon lattice (IVth group); (b) Si “n-layer”; (c) Si “p-layer”; (d) cross section of a photovoltaic “n–p” cell; (e) Fuller cell (Si–Si); (f) cell with different bases (Cu

Figure 3.2   Photovoltaic structures: (a) silicon lattice (IVth group); (b) Si “n-layer”; (c) Si “p-layer”; (d) cross section of a photovoltaic “n–p” cell; (e) Fuller cell (Si–Si); (f) cell with different bases (Cu2S/CdS); (g) Shottky cell (1930)—thin barrier (“n” Cu2x/“p”CuO or “n”Si/“p” Si) with a thin metal layer.

Two very thin “n” and “p” layers are arranged along the direction of supply of a modern photovoltaic cell* (see Figure 3.2d) with solar energy (photons from the visible and infrared regions of the spectrum). So far, a number of “n–p” combinations have been designed using various chemical elements—some of them are shown in Figure 3.2e–g.*

How do the two “n” and “p” layers operate jointly under direct solar radiation? Solar photons penetrate both semiconductor layers “bombarding” the electrons of their valence bands.

If the photon energy absorbed by the electrons is larger than the energy threshold of the banned zone, they leave the atoms of the layer and start moving in the free conducting zone (if the energy is not sufficient to overcome the energy barrier of the banned zone the electrons stay within the orbital surrounding the atomic nucleus. They send back the received photons in an arbitrary direction and give birth to phonons through which energy dissipates as heat). Some electrons in the “p layer” move to the “n layer,” creating significant electron deficit in the “p” layer and significantly increasing the positive potential of the “p layer.” At the same time, electron excess occurs in the “n layer” and its negative electric potential increases (the crystal lattices of both layers are internally ionized).

If both layers are connected to instruments via closed circuit (see in Figure 3.2d), electromotive force (emf) arises under the potential difference and electric current flows. The electrons leave the “n layer” and return to the “p layer” through the closed external circuit where they recombine with lattice anions. The process does not damp since the solar photons leave vacancies in other lattice atomic structures. Since the voltage at the cell exit under normal conditions (Te = 293 К and ISolar = 1000 W/m2) is very low (1.36 V), cells are assembled in solar panels consisting of 25–36 individual cells with total power of up to 230 W (see Figure 3.3b). On the other hand, solar panels are assembled in series with output voltage of 400 V called “strings.” The electric energy generated is usable after conversion (DC→AC) of its parameters by means of electronic devices called inverters. The converted parameters should correspond to those of the final users.

Photovoltaic structures: (a) cell with output voltage 1.36 V; (b) panel—32.6/92.0 V.

Figure 3.3   Photovoltaic structures: (a) cell with output voltage 1.36 V; (b) panel—32.6/92.0 V.

The efficiency of the existing laboratory prototypes of multilayers photovoltaic cells is good—37%–43%, but just 8%–15% of the incident solar energy is converted into electricity by means of the commercial PV cells. The rest energy spontaneously dissipates in the surroundings as heat.

Solar internal ionization is a phenomenon where two different (co-generation) energy forms are obtained—electrical and thermal (see Dimitrov, 2015). Recently, a tendency to integrate the solar cells with thermal panels (“n–p” plus thermoabsorption hydraulic system), called hybrid panels has occurred. This is expected to yield better operational conditions both for the electric/thermal system with total conversion efficiency in the range 71%–82%, especially in winter.

Regarding the geography of Southern Germany, electricity of 8.0 kWh per day can be produced by a photovoltaic cell with 2 m2 surface (cell productivity for Southern Europe is about 10.0–12.0 kWh per day). If such a cell is integrated with the building envelope, its energy efficiency will rise due to co-generation.

Prices of photovoltaic systems were about $6000/kW in 2005, while now they are less than $2500/kW 2500. The prime cost of 1 kWh generated by a photovoltaic system was $0.76/kW in 2005. Yet, it is now significantly lower, and it is expected to drop to $0.17/kWh in 2030. This will make the photovoltaic technologies fully competitive with thermoelectric technologies, especially in small (household) applications. Until then however, they should be treated with special care by officials due to their friendliness to environment and compatibility with the central systems for energy generation and distribution.

3.1.2  Thermoelectric Technology of Seebeck

The German physicist Thomas Seebeck (1770–1831) found in 1821 that when two thermo/electro conducting materials with different conductivities were formed together, a voltage difference (ΔV) occurred between their free ends—Figure 3.4a (at present, the combination is known as a thermocouple). At the same time, Seebeck established that the value of the electro-potential difference (ΔV) depends on the temperature of the environment where the thermocouple is located.

Seebeck effect: (a) demonstration; (b) thermoelectric circuit: 1—copper rod (n-type); 2—constantan rod (p-type); 3—contact weld; 4—galvanometer.

Figure 3.4   Seebeck effect: (a) demonstration; (b) thermoelectric circuit: 1—copper rod (n-type); 2—constantan rod (p-type); 3—contact weld; 4—galvanometer.

In 1823 Seebeck showed that if two thermocouples were serially connected, electric current ran through their wires upon immersion in warm (T1) and cold (T2) physical medium (energy sources), respectively (Figure 3.4b).

He found that emf occurring in the circuit was directly proportional to the temperature difference ΔT = (T1 − T2), i.e.,

that is, if ΔT ↑, then emf ↑, and vice versa.

The relation between temperature difference dT and the electric potential difference dV in deferential form reads as follows:

The above relationship is known as the Seebeck equation.

It is found that the proportionality coefficient (SAB), named after Seebeck, depends on the thermocouple materials. It has been proved that the value of the Seebeck coefficient (SAB) is proportional to the coefficients of thermal and electrical conductivities (λ and Ω)

Although that the link Z (Z = SAB/(λΩ)0.5) has a clear mathematical structure, it is a complex physical quantity depending on the capability of metal crystal lattices to react to external thermal impacts—this is the lattice capability to interact with infrared photons whose carrying wavelength exceeds 860 nm. The results in Figure 3.5 for the values of the functional Z = SAB/(λΩ)0.5 show that semiconductors are materials most appropriate to realize Seebeck technology.

Optimization of the complex Z = S

Figure 3.5   Optimization of the complex Z = SAB/(λΩ)0.5 for different materials.

After Thomas Seebeck, Jean Peltier in 1834 and William Thomson (Lord Kelvin) in 1854 obtained similar results. They studied different heat convertors of the “n–p,” type, Bi2Te3 or Cu-GeSi for instance, thus finding inverse thermoelectric effects.* Initially, the thermoelectric effect of Thomas Seebeck was explained by the different conductivity of the couple materials. Later, it became clear that this was a new phenomenon called “internal ionization,” while can be explained by the zone theory.

Now, 200 years later, it is clear that the Seebeck effect is due to the thermocouple specific atomic structure and its capability to undergo different internal ionization under the impact of photons radiated by heat sources. The processes observed and described by Seebeck can be explained as follows (Figure 3.4).

The copper rod being an “n”—type conductor conducts heat according to Kaganov's mechanism. Copper is a metal belonging to group II of Mendeleev's table. It has two electrons in its valence band, and its banned zone merges into a free zone. Electrons are released from the atomic nuclei of the crystal lattice spontaneously and under low temperature. When a contact with the hot source is realized, the atoms of the contact area get excited and internally “ionized” under the effect of long wavelength photons. Besides, the atoms of the valence band pass over the banned zone (it is very narrow for Cu) and form a gas of free electrons belonging to the crystal lattice of the contact area between the thermocouple and the hot source. The quantity and concentration of the free electrons depends on the hot source temperature T1. Simultaneously, the second contact thermocouple at the other end of the circuit is immersed in the cold source which temperature is T2. Due to the low temperature, electron concentration of the free electron gas is significantly lower, since the process of internal ionization is less intensive.

Since both ends of the copper rods (“n” type) are connected by a cable, the electrons of the “hot” end flow to the “cold” end (see in Figure 3.4b). If there is no second cable, equilibrium will take place after the equalization of the electron concentration at the two rod ends, and the electric current will be blocked.

Regardless of the transfer of “n” electric charges through the copper cable, similar processes* run in the other two rods manufactured from semiconductors with “p” conductivity (see Figure 3.4b). Yet, holes (vacancies) are emitted to the areas of contact with the heat sources. The difference is that more holes will concentrate around the cold body than around the hot body. Those holes have diffused through the weld and have been directed to the “n” zone.

If only rods with “p” conductivity are connected in an external circuit (the “n” rods circuit remains open) equalization of charges carried by the holes will take place. That “p” electric current will be directed from the cold to the hot source, and it will die out after the equalization of the holes concentrations of the two rods.

If a fully closed electric circuit is present, continuous motion of electric charges in both directions will take place: “n” charges will move from the cold to the hot body, and “p” charges will move in opposite direction. The process will not damp since the internal ionization in the two contact areas would take place with different intensity that would guarantee a continuous electric driving force.

A number of attempts to create thermoelectric converters or heat generators of electricity have been made since Seebeck's discovery (1823). The efficiency of those converters is assessed via a conversion coefficient reading

where
  • ηCarnot = (1−(T2/T1)) Carnot coefficient
  • ηrel = M−1/M + (T2/T1) coefficient of relative efficiency resulting from the irreversible losses
  • .

For a long time, the coefficient of relative efficiency ηrel was too low (ηrel< ≈ <0.002). Hence, those thermoelectric converters were only used as temperature sensors in measuring instruments. The reason for their low efficiency was the large internal Joule work done during electric current flow through the converter and its contact “n–p” area.

Recently, thanks to the pioneering works of A.F. Jeffe, an almost two order of magnitude increase of the coefficient of relative efficiency has been attained, where ηrel ≈ 0.28.

The total theoretical conversion coefficient ηth of the instrument for T2/T1 = 0.79 (corresponding to Tr = 107°C and Tc = 27°C) will be 6%.* Yet, if the thermal–electric convertor operates at a higher temperature difference, ηth may reach values of 14%–20%.

Those impressive results were obtained by optimization of a profit function of the form Z = α2Ω/λ, where Ω and λ are the coefficients of material electrical and thermal conductivity, and α is an exponential function. As a result of a number of theoretical and experimental studies, it was proved that most appropriate are alloys able to provide large specific concentration of electrons in the contact “n–p” area (

)—see in Figure 3.5.

A typical thermoelectric energy generator employing the Seebeck effect is built according to the scheme in Figure 3.6. It is used for the recuperation of waste heat of combustion products, exhausted by heat engines, CCs, electric transformers, cooking stoves, illuminating systems, foul air released by air conditioners etc. The heat is harnessed in the generation of electricity for private needs. Recuperator 1 in Figure 3.6 is located in an environment where waste heat (hot source (HS)) is released, receiving heat flux with intensity qin.

Thermoelectric energy generator: 1—recuperator (hot source); 2—semiconductor type “n”; 3—semiconductor type “p”; 4—inverter; 5a and 5b—users; 6—conductor of electricity; 7—surfaces releasing heat to the old source (radiators).

Figure 3.6   Thermoelectric energy generator: 1—recuperator (hot source); 2—semiconductor type “n”; 3—semiconductor type “p”; 4—inverter; 5a and 5b—users; 6—conductor of electricity; 7—surfaces releasing heat to the old source (radiators).

The remote ends of the two semiconductors contact the cold zone (cold source (CS)) via radiators 7 releasing heat flux qout. The resulting electric driving force generates electric current running through the electric circuit consisting of cables 6 and 6a, inverter 4 and various switched-on users–LED 5a, ventilators 5b, etc.

The second interesting application of thermoelectric convertors concerns the operation of the inverse process discovered by Peltier/Thompson, where electrical energy is converted into heat and frost. Really, when electric current flows in the electric circuit of the convertor, a temperature difference occurs between the radiator and the recuperator which can be used for the air conditioning of small volumes or individual workplaces.

3.1.3  Thermoelectric Technology for Oxidation Control in FCs (Technology of Schonbein/Grove)

FCs are power equipment where the controlled oxidation of gaseous fuel (hydrogen, natural gas, methane, syngas, propane, hydrocarbons, etc.) is carried out. As a result of the process running in a catalytic environment, electric energy* is also generated besides heat and water (which is newly generated chemical product). Currently, a large variety of FCs exists, and part of them are manufactured and marketed on a large scale. Despite the different scheme of their classification, the thermal processes use a classification that considers the value of the temperature of reaction operation. According to that classification, the FCs are divided into two groups

  • “Low-temperature” FCs where the operational temperature is lower than 250°C
  • “High-temperature” FCs

In what follows, we shall consider that bothof these classifications.

The group of “low-temperature” FCs usually includes: cells with a polymer membranes (PEM), alkaline fuel cells (AFC), and phosphorus-acidic cells (PAFC). The gaseous fuel used (often hydrogen or natural gas) is injected at high pressure through the intake aperture 1 in Figure 3.7. Meanwhile, pure atmospheric air (containing 21% oxygen) is injected as an oxidizer through the second intake aperture 3. The following exothermal chemical reaction runs in a classical low-temperature FC, where pure oxygen is used

3.1
while free electrons are also produced and accumulated at one terminal, named the negative terminal. They are controllably directed by Coulomb’s* force through the external copper conductor (see Figure 3.7) to end users as an electrical current.

FC components: (a) scheme of a FC; (b) inside view of SOFC: 1—fuel supply line; 2—anode (N-terminal); 3—air duct; 4—cathode (P-terminal); 5—electrolyte (conducting medium); 6—external conductor; 7—accumulator (or inverter); 8—lectric motor.

Figure 3.7   FC components: (a) scheme of a FC; (b) inside view of SOFC: 1—fuel supply line; 2—anode (N-terminal); 3—air duct; 4—cathode (P-terminal); 5—electrolyte (conducting medium); 6—external conductor; 7—accumulator (or inverter); 8—lectric motor.

Fuel and oxidizer are separated from one another by an electrolyte (solid or liquid electroconducting medium). Zirconium oxide (porous ceramics), hard polymers of alkaline/acidic solutions are successfully used as electrolytes.

When a solid electrolyte 5 is used in a FC, its facial surfaces 2 and 4 adjacent to the fuel feeding pipes 1 and 3 are coated by a catalyst and transformed into electrical charges terminals (electrodes). When the electrolyte is liquid (phosphorus acid or alkaline solutions, for example), the two fuel feeding pipes serve as electrodes, and they are immersed in the electrolyte, being previously coated by a catalyst.

The FC is a typical representative of an open and noninsulated TDS with three degrees of freedom doing chemical, thermal, and electric work. The process runs as follows. The compound necessary for the chemical reaction is fed continuously at pressure through the fuel and air feed pipes 1 and 3. The hydrogen molecules dissociate into anions H(+) and electrons e(−) (the catalyst facilitates migration of the hydrogen ions into the electrolyte, only, and displays large electric resistance with respect to the free electrons). Hence, hydrogen anions are subjected to potential and electric repulsive forces, and they start moving within the electrolyte. Meanwhile, the oxygen atoms join themselves as free electrons at the P-terminal and are converted in negative ions. This produces a shortage of electrons at the positive terminal (electrode)—see Figure 3.7a. Unless electron deficiency is overcome, the described processes will slow down. If a copper conductor is connected between the P- and N-terminals, the electrons shortage will be removed by the flow of electric current between the two electrodes. The electrons released by the hydrogen atoms continue their motion along an external circuit as electric current which is supplied to the connected electric appliances 7 and 8—Figure 3.7 to do the needed work. The final electron destination is the cathode 4 where electrons combine with the newly arrived oxygen molecules to transform them into cations.

The hydrogen ions are directed toward the oxygen ions (located at the other side of the electrolyte), for which they have chemical affinity. Carriers of the electric current in the electrolyte of a low-temperature FC are the hydrogen anions H(+). They diffuse through the electrolyte reaching the cathode where they combine with the “waiting” oxygen cations –O(−). The internal electric circuit closes when two hydrogen anions combine with one oxygen cation to form a molecule of water. The chemical reaction (3.1) describes the process. It is continuous when the FC is continuously supplied with fuel and oxygen, while products of oxidation and co-generation are used. Note that oxidation is an exothermal reaction producing hot water or steam, while co-generation produces electricity.

While low-temperature FCs produce hot water, mostly, the high temperature ones produce hot water or superheated steam, since their operational temperature reaches values of up to 950°C. The group of high-temperature FCs includes those with solid-oxide electrolytes (SOFC) and electrolytes composed of molten carbonate FC (MCFC). Both FC types are not sensitive to impurities and CO that might be present in the fuel. Hence, they successfully operate using natural or synthetic gas, methane, and propane. If fuel contains an impurity, it poisons (contaminates) catalysts (Pl, graphene, cobalt and cobalt oxide, etc.) which cease to be effective.

The maximal electric driving force of a FC single module, generated as a potential difference between the electrodes, is small (about 1.2 V). Yet if 10 modules are assembled in a serial group (see Figure 3.7), an output voltage is generated. It is commensurable with that of the lead–zinc batteries. The final output voltage of the FC used in systems of energy supply known as “energy servers” is 400 V, while the nominal consumed power is 100 kW.

The theoretical conversion coefficient of a FC is calculated as

or ηth = 85%. The following notations are used:
  • LTotal—total work done in a TDS (the sum of electrical and thermal engines done per unit mass oxidizer [per 1 kmol oxygen]). It is calculated as a difference between the values of the Gibbs free potential (LTotal = 56.6899 kcal/gm-mole per unit mass)
  • No—Avogadro number (6.025 × 1026)
  • n is the number of electrons absorbed by the oxygen molecules to produce 1 gm-mole H2O
  • e0 = 1.062 × 10−19 eV—energy of a single electron
  • ΔH0 is fuel enthalpy (the quantity of energy released under controlled fuel oxidation—ΔH0 = 68.3174 kcal/gm-mole for hydrogen)

The real conversion coefficient of a FC during cogeneration, however, rarely exceeds 75%.

Low-temperature FCs are efficient and durable under steady applications. Yet, one should avoid the use of hydrogen produced by natural gas reforming, since it contains carbon monoxide which contaminates the catalysts. It is recommended that hydrogen be used that is produced by electrolysis. Reformed alcohol, methanol, or ethanol can also be used.*

Phosphoric-acid FCs having power within the range 100–200 kW are used for building applications. Under co-generation FCs their thermal to electrical outputs are in proportion as 40/36. Their conversion coefficient attains values of up to 76%. A typical FC arrangement includes a preprocessor (reformer), which produces hydrogen from the fuel, a stack where electrochemical processes are in operation and an inverter (power conditioner) which transforms the DC current into AC current. Most FCs include also an interconnector (a device that synchronizes the parameters of the output current with those of the grid—ASHRAE 2001; ASME Standard PTC 50).

FCs with molten carbonates generate power of 100 kW–10 MW, while those using solid oxides 100–200 kW. Their operational temperature is 650°C, and cogeneration efficiency reaches 70%. They are not “choosey” with respect to fuel purity, and they become more and more popular in thermoelectric projects.

3.2  Indirect Thermoelectric Technologies

The group of indirect technologies includes those capable of converting the generated heat into kinetic energy of mechanical bodies. Then, as shown in Figure 3.8, the mechanical energy is converted into electricity via electromagnetic induction.*

Indirect thermoelectric technology.

Figure 3.8   Indirect thermoelectric technology.

Figure 3.8 shows that there are four technologies of heat generation ordered with respect to their market share—uncontrolled oxidation (combustion), fission of the atomic nucleus, solar and geothermal heating. Following the above order, we shall discuss in what follows the two most popular thermoelectric technologies:

  • Rankine's steam-turbine technology of
  • Brayton's gas-turbine technology of

The two technologies are similar to each other. The difference between them is insignificant at first glance and concerns the type of the used working body, that is, Rankine technology uses fluids (water, chlorofluorocarbons, lithium–bromide mixes, etc.) which undergo phase transformations, while Brayton technology uses combustion gases exhausted during the burning of the primary energy carrier. In fact, there are significant differences concerning technological equipment and efficiency

  1. Rankine technology realizes energy transfer between the heat generator (boiler) and the thermal engine (steam turbine) using smaller amounts of fluid mass. The energy is “encoded” in a “liquid–gaseous phase” transformation (i.e., transformation of a liquid into superheated steam as shown in Figure 3.9. To close the cycle however after steam exhaust, one needs to perform inverse steam conversion (forced condensation) in a special device called condenser. In Brayton technology, heat is transferred by combustion products directly to the thermal engine (gas turbine). To transfer energy amount comparable to that of the Rankine technology, one should use more amounts of flue gases. This decreases the technology efficiency to a certain extent. Yet, the necessity of condensing the working fluid falls away and the inevitable heat losses along the whole technological circuit are avoided—note that they are significant in pure electrification technologies, amounting to 50%–60%. The condenser as a component of the system is also removed.
  2. The second essential difference between the two technologies is that between their temperature ranges of operation. In Rankine technology, the temperature of the superheated steam is Tn ≈ 550–600 K, while that of the condenser is about 353–408 K. This yields a relatively low conversion coefficient

Steam-turbine technology of Rankine: T—steam turbine; G—electrical generator; Ec—economizer; HWDS—heat exchanger of the system for hot water domestic supply; P—feed pump (a) ideal cycle of Rankine; (b) recuperation cycle along the line of the steam processed via the economizer; (c) as in (b), but with heat exchanger for domestic hot water supply; (d) diagram of the ideal process; (e) diagram of the recuperation process (

Figure 3.9   Steam-turbine technology of Rankine: T—steam turbine; G—electrical generator; Ec—economizer; HWDS—heat exchanger of the system for hot water domestic supply; P—feed pump (a) ideal cycle of Rankine; (b) recuperation cycle along the line of the steam processed via the economizer; (c) as in (b), but with heat exchanger for domestic hot water supply; (d) diagram of the ideal process; (e) diagram of the recuperation process (Points: 1, A, 2, and B in the schemes correspond to those in the state diagram of the working fluid).

The real conversion coefficient of this technology does not exceed 38%.

As for Brayton technology, energy transfer takes place at significantly larger temperature differences. For instance, if the temperature of the combustion products is T1 = 1573 κ (see Figure 2.25), while that of the exhaust gases drops to the temperature of the surroundings (T2 = 300 К), the efficiency of the thermoelectric technology increases significantly, since ηCarnot ∼ 81%, and the real value of the conversion coefficients approaches 65%.

A disadvantage of Brayton technology is the necessity to use only high-temperature resistant materials for the manufacture of the technological equipment (molybdenum and nickel steels, titanium alloys, ceramics, and metal powders). This significantly increases the amount of the initial investment. On the other hand, it is known that if there is a market that is hungry for the products of modern metal science, product prices go down significantly. There are a number of examples in this respect, and the development of the energy sector in the next quarter century seems promising. That optimism is verified by the invention of new and more efficient materials (see for instance the products of nanotechnology).

3.2.1  Steam-Turbine Technology of J. Rankine

Historically, Rankine* technology has been a special service to modern electrification, and there are two technology types. The first one is that of electricity generation without recuperation of the waste heat (Figure 3.9a). The second one is co-generational steam-turbine technology for the simultaneous generation of electricity and heat in the so-called “central-heating” or public thermal electric power stations (Figure 3.9b).

Regarding the first type, heat q1 generated by burning of primary energy carriers—fuel (coal, wood, oil derivatives, etc.), is supplied to the working fluid right in the CC. There, the working body changes its aggregate state and (usually water) evaporates isobarically along the line “B–B1–1′–1.” Thus, the first stage of the Rankine cycle (isobaric expansion) is completed at point “1” by preheating of the working fluid into superheated steam with temperature T1—see Figure 3.9d).

To start the second stage (adiabatic expansion) the working fluid is expired into the steam turbine where it releases its internal energy to do mechanical work:

.

It overcomes the friction moments in the turbine and generator bearings, as well as the electric resistance moments. Under adiabatic expansion, the temperature of the working fluid drops from T1 to TA.

The above equality shows that the mechanical work done by the steam turbine depends on the difference between temperatures T1 and TA, and the larger the temperature difference the more efficient the process. When the steam used in the turbine attains temperature TA, it is introduced into the condenser where it is again condensed under isobaric conditions (pA = const) releasing heat to the cold surroundings (the atmospheric air). The temperature of the working fluid remains constant T2 = TA. Thus, completing the third stage of the Rankine cycle, the fluid returns to its initial state—liquid. Heat released during condensation dissipates in the atmosphere (used as a cold body). This is a serious disadvantage of the technology.

The fourth (closing) stage of the Rankine cycle is adiabatic pumping from point 2 to point B (pressure rises from p2 to pB), where the feed pump pushes the working fluid in the boiler for the new evaporation process and cycle repetition. As seen in Figure 3.9a, the steam turbine is coupled with an electric generator where the kinetic energy of rotation of the working wheel and the generator rotor is converted into electrical energy via electric induction.

Rankine technology is energetically imperfect, since it “suffers” huge energy losses in the condenser (55%) and during the release of hot flue gases (12%). However, it was improved in the course of more than a century.* Initially, heat of the consumed steam (after the first section of the turbine—Figure 3.9b) was used by the economizer of the steam boiler.

Next, a heat exchanger was incorporated as a heater which increased the efficiency of the steam-turbine technology.

Steam needed for the operation of the heat exchanger is deflected after the second section of the steam turbine (see Figure 3.9c). Thus, energy co-generation is possible. In installations designed following such a scheme, about 50% of the primary energy is spent for heat generation for households, 12% is spent for the generation of electricity (co-generation), and the losses in the condenser are 20%, only. The total regeneration coefficient of the Rankine steam-turbine technology may attain 60%–65% (this is its proven maximal efficiency).

There are three more versions of the Rankine steam-turbine technology, in addition to the one already described. They are based on the use of solar radiation, Earth core energy, and the energy of thermonuclear reactions. We shall describe them in what follows, since they outline new prospects of effective development of the Rankine cycle.

Figure 3.10 shows a scheme of a solar thermal electric power station operating with Rankine technology. Heat is generated using the “optical concentration of solar radiation,” which reaches high density of solar energy flux directed to the solar receiver (position 3a in Figure 3.10a). It exceeds by 30–40 times the nominal density.

Solar thermal technology for the generation of electricity, arrangement of the technological equipment of the station. (a) parabolic reflectors; (b) linear Fresnel reflectors; (c) Heliostatic tower (3c) with tracing reflectors (2c): 1—solar absorber field; 2a—parabolic reflectors; 2b—reflector bands; 2c—reflector mirrors; 3a—movable solar receiver; 3b—stationary solar receiver; 3c—reversible solar receiver “Heliostatic tower”; 4—steam generator; 5—thermal storage and exchanger; 6—circulation pumps; 7—feed pump; 8—steam turbine; 9—electric generator; 10—condenser.

Figure 3.10   Solar thermal technology for the generation of electricity, arrangement of the technological equipment of the station. (a) parabolic reflectors; (b) linear Fresnel reflectors; (c) Heliostatic tower (3c) with tracing reflectors (2c): 1—solar absorber field; 2a—parabolic reflectors; 2b—reflector bands; 2c—reflector mirrors; 3a—movable solar receiver; 3b—stationary solar receiver; 3c—reversible solar receiver “Heliostatic tower”; 4—steam generator; 5—thermal storage and exchanger; 6—circulation pumps; 7—feed pump; 8—steam turbine; 9—electric generator; 10—condenser.

The working medium of the first loop (water solutions of sodium and potassium salts or high carbohydrates—pentane, sextane, etc.) is heated to 640 K passing through the solar field 1, without changing its physical state. All receivers of the solar field are linked in parallel. The heated fluid passes through the steam generator 4 and storage 5 (see Figure 3.10), giving its energy to the heat carrier of the secondary loop. Then, undergoing the pressure increase by the circulation pump 6, it enters the pipe system of the solar field to be heated again and repeat the cycle. The second loop consists of the steam generator 4, steam turbine 8, condenser 10, circulation pump 7, and accumulator 5, and the working fluid is water steam.

During the operation the processes are similar to those found in the classical steam-turbine technology—see Figure 3.9. The difference is in that the classical boiler (steam boiler) is replaced by a steam generator 4, which is a highly efficient heat exchanger of the “water/steam” type. Another difference is that instead of an economizer, the heating exchange coils of the accumulator 5 are used here. Following the requirements of Rankine technology, those formal differences do not affect process efficiency. The incorporated electric generator 9 converts steam potential energy (at temperature 450–500 К) into electricity via turbine rotation. The conversion efficiency of Rankine solar thermal technology can range up to nearly 30% (usually exceeding the efficiency of the photovoltaic solar technologies by good measure) and outruns the conversion coefficient of PV systems.* Considering the 2008 cost of 1 kWh power generated by solar concentrators cost ($ 0.20), as well as the prospects of cost decrease during the next 10 years, the technology may gain ground in Mediterranean countries, including Europe.

The second important application of the Rankine cycle is the steam-turbine technology for generation of electricity. It utilizes the geothermal energy of the Earth core using the method “hot dry rocks—HDR”—see Figure 3.11.

Geothermal technology (dry hot rocks) for the generation of electricity: 1—evaporator of the heat pump; 2—heat pump; 3—steam turbine; 4—electric generator; 5—condenser; 6—feed pump; 7—condenser of the heat pump; 8—pressurizing pump; 9—HDR; 10—sucking compressor.

Figure 3.11   Geothermal technology (dry hot rocks) for the generation of electricity: 1—evaporator of the heat pump; 2—heat pump; 3—steam turbine; 4—electric generator; 5—condenser; 6—feed pump; 7—condenser of the heat pump; 8—pressurizing pump; 9—HDR; 10—sucking compressor.

A refrigerating agent is the working fluid in this case, boiling at low temperature (water–ammonia solution, for instance). The pressurizing pump 8 injects deep into the ground the liquid (body) to reach the so-called “dry hot rocks” 9. There, it evaporates and the superheated steam is sucked by the compressor 10 and pressurized into the reservoir-evaporator 1. Devices 1, 8, 9, and 10 participate in the primary loop of the geothermal installation. That loop takes heat out of the hot rocks and transports it to the heat pump 2. Its operation is hydro dynamically independent of that of the rest two loops. Yet, it determines their energy efficiency.

The heat pump 2 forms the second loop which is also hydro dynamically independent. The pump takes the energy of phase transition of the working fluid via its evaporator 1, where the working body condenses and liquefies for secondary usage. The heat pump is calculated such as to operate in “steam/steam” regime. It increases the temperature of the Rankine loop's working body in condenser 7 of the HP and it is evaporated. The steam boiler here is replaced by the condenser section 7 of the heat pump producing steam for the operation of turbine 3. Since, water successfully is evaporated in device 7, thermal energy is transferred to the steam turbine, which is coupled with an electrical alternator in the third loop of the system. Used steam is condensed in the condenser 5 (a component of the Rankine equipment), while the feed pump 6 pressurizes it back into the heat exchanging tubes of the HP condenser 7 to be again evaporated, thus maintaining the cycle performance.

The total conversion coefficient* of geothermal stations reaches 95% and electricity cost is about $0.15/kWh (seldom—$0.05/kWh). At present, it is twice higher than that of wind electric power stations and only three times higher than that of electricity generated by coal-burning thermoelectric power stations. The technology is absolutely clean and renewable, leaving minimal traces in the environment. However, its greatest advantage is that the needed heat is freely and readily available—at a depth of 3 km, only.

Last but not least, Rankine technology is applied in nuclear power stations (NPSs). The main problems of the nuclear technologies are how to guarantee environmental protection, safe and healthy working conditions, and reliable and safe facility operations. So-called “multi loop” systems are used for the sake of safety, where the risk of outflow of radioactive materials is reduced. Figure 3.12 shows two schemes of arranging the technological equipment—with two and three loops. Note that the increase of the number of internal loops (from 1 to 2) yields significant increase of the reliability and thermal inertia of the system. Besides, all components of the internal loop, which are in direct or indirect contact with the reactor (for instance, circulation pumps 7 and 9, steam-generator heat exchangers 2 and 10 and automation components), are inaccessible thanks to biological protection 8. It is the second important feature of this technology. In fact, reactor biological protection is guaranteed by an insulating layer of massive concrete covered by lead, steel, or aluminum sheets. Thus, it is impermeable to all radioactive products. The remaining units are the same as those of the Rankine technology. They are similarly arranged in an external loop consisting of steam turbine 3, condenser 5, and feed pump 6.

Steam-turbine NPS–multi loop schemes of NPS. (a) Two-loop; (b) Three-loop: 1—reactor; 2 and 10—steam generators; 3—steam turbine; 4—electric generator; 5—condenser; 6—feed pump; 7 and 9—circulation pumps; 8—biological protection.

Figure 3.12   Steam-turbine NPS–multi loop schemes of NPS. (a) Two-loop; (b) Three-loop: 1—reactor; 2 and 10—steam generators; 3—steam turbine; 4—electric generator; 5—condenser; 6—feed pump; 7 and 9—circulation pumps; 8—biological protection.

The enormous energy inertia of the nuclear reactors intensified by the thermal inertia of the other two loops makes the NPSs difficult to be centrally regulated. Hence, they are used to support the stationary season loadings of the electric supply system, only, forming the system base. All other non-nuclear energy sources can be used as either seasonal or 24-hours energy reserves. Soon, they will play an important role in the conclusion of local energy contracts after the activation of a regional (e.g., Black Sea coast) energy stock market.

Hence, despite its low efficiency, the Rankine technology of electricity generation or co-generation can be employed anywhere where phase transformation of the working fluid is to be performed. Included are atomic reactors that operate using light water, solar thermal systems, or systems for the utilization of highly potential energy waste from industrial technologies.*

The Rankine cycle was replaced in transport in the 20s by other engine technologies and recently—by hybrid technologies (see Section 3.3). Exceptions are only cases where nuclear technologies are applied—submarines or space rockets, for instance.

Based on those specific technologies, nuclear reactors maintain favorable chances of being used as future energy reactors and co-generators for domestic and industrial applications, while their overall dimensions would drastically decrease.

Table 3.2 gives a list of nuclear reactors with power less than 50 MWe, that are in the process of implementation or already in operation, but not for military and transport usage, thus confirming the tendency to miniaturize nuclear reactors with nuclear fission. They are part of modern heat generators operating after Rankine's or Brayton's schemes.

Table 3.2   List of Nuclear Reactors with Capacity Smaller than 50 MWe

No

Type

MWt/MWe

Designer

Cooling System

COP (%)

1

GEN4 Energy

70/25

Hyperrion

HPG

36

2

KLT-40S

150/35

OKBM

PWR, 4c.l.

23

3

NuScale

160/50

NuScale&F

Integral PWR

31

4

SSTAR

45/20

LL&LANL

Carbon dioxide

44

5

Toshiba 4s

30/10

Westing H.

Sodium cooling

33

6

MRX

50/30

JAERI

PWR

60

7

Unitherm

20/5

RDIPE

PWR

25

8

Shelf

28/6

NIKIET

PWR

21

9

Triga

164/64

General A.

PRW

39

10

Smart Dunedin

30/6

Dunedin ES

20

11

Sealer

8/3

Royal IT

Lead CR

37

12

CEFR

65/20

China

Sodium cooling

31

13

Rapid-L

5/0.2

JAERI

Molten Sodium

4

3.2.1.1  Tendency to Miniaturize the Overall Dimensions and Power of Nuclear Reactors

Nuclear reactors operating with “fast neutrons” of nuclear fusion, a “Tokamak” class, might be usable for energy generation, but not until the second half of the present century.

In the last 10–15 years, worldwide leading nuclear research institutes and companies designed over 30 reactors with power not exceeding 50 MWe (see column 3 in Table 3.2), which operate with “fast neutrons,” yet generated by nuclear fission. The characteristic feature of most of them is that the “energy extraction” from the reactor core is carried out by phase-converting coolants following Rankine's thermodynamic cycle (with coefficients of heat-electricity conversion in the range of 4%–60%—column 6 of Table 3.2). Besides water, easily melting metals such as lead, lithium or sodium, for instance, are also used as coolants.

In fact, small nuclear reactors were used in energy generation even in the 20th century. The smallest, with power of 12 MWe, was installed in the “Bilbino” NPS, Chukotka, Russia, as far back as 40 years ago. That reactor known by its acronym EG-6 is of water-graphite type (LWGR). Another emblematic example is the reactor BN-20, operating in the town of Tueali, China, with power of 25 MWe and 65 MWt, respectively.

At present, the least powerful reactor is integrated with the nuclear co-generator Rapid-L, designed in Japan by JAERI (1999–2001), with power of 0.2 MWe and 5 MWt, respectively, followed by the reactor incorporated in the co-generator Sealer with power 3 MWe and 8 MWt designed by the Royal Institute of Technology of Stockholm.

Rapid-L is an energy co-generator (6:0.2 MWt/e), using liquid metals as coolants, such as lithium Li6 (Tmelt = 1063°C); sodium (Tmelt = 882°C) or potassium (Tmelt = 757°C). Lithium is also used as a filter of neutrons, emitted in the course of the nuclear reaction. The circulation of the liquid metal within the cooling system is realized by electromagnetic pumps.

The Rapid-L reactor is in operation without human intervention for a long period of time (10 years). Uranium–nitrate mix is used as fuel, in proportions 2:3, while a revolving mechanism is currently employed to replace cassettes with discharged fuel.

Figure 3.13 shows a general scheme of the co-generator Rapid-L. It is seen that the reactor core 1 is separated from the electrogenerator 3 by a two-loop cooling system, consisting of a heat exchanger 5 and a system for the circulation of liquid sodium comprising an electromagnetic pump 8, circulation lines 7, and a tank 9.

Scheme of the nuclear co-generator Rapid-L of JAERI with power 5.0/0.2 MWt/e: 1—integrated fuel assembly; 2—reactor; 3—power conversion segment; 4—heat exchanger (for heat supply); 5—heat exchanger (sodium heat pipe); 6—LRM, release mechanism; 7—sodium circulation lines; 8—electromagnetic pump; 9—sodium tank.

Figure 3.13   Scheme of the nuclear co-generator Rapid-L of JAERI with power 5.0/0.2 MWt/e: 1—integrated fuel assembly; 2—reactor; 3—power conversion segment; 4—heat exchanger (for heat supply); 5—heat exchanger (sodium heat pipe); 6—LRM, release mechanism; 7—sodium circulation lines; 8—electromagnetic pump; 9—sodium tank.

Besides the two-loop system thus designed to cool the reactor, the high reliability of Rapid-L is alsoguaranteed by a scheme for automatic regulation, consisting of four subsystems

  • LEM—for control of the liquid metal
  • LRM—for automatic start of the reactor
  • LEM and LIM—for current automatic control of the reactor (LEM—for feedback control and LIM—for end control)

The overall dimensions of Rapid-L are 2 m diameter and 6.5 m height, while its weight is 7700 kg. The efficiency for heat conversion into electricity is 4%, which makes the device suitable for operation in a cold climate. Initially, it was designed to operate in space, while the compact structure makes it suitable for use in domestic energetics with thermal loads multiply exceeding the electric ones. The Rapid-L co-generator is installed underground, in a shaft under the border of the building it served, while the earth layer over it serves as a biological barrier against radiation.

The second compact micro reactor included in our survey is the Swedish co-generator Sealer (see Figure 3.14). It is designed to operate with an efficiency coefficient (EC) of 31% and nominal heat and electric power of 8.0/3.0 MWt/e, respectively (see Table 3.2). A mix of uranium dichloride (UO2) and enriched uranium (U) in proportion 4:1 is used as fuel. Cooling is carried out by a liquidized metal (lead, with melting temperature TMelt = 450°C).

Scheme of the nuclear microreactor “Sealer” of the Royal Institute of Technology of Stockholm with power 8.0/3.0 MWt/e: 1—core; 2—supporters; 3—heat exchanging structure.

Figure 3.14   Scheme of the nuclear microreactor “Sealer” of the Royal Institute of Technology of Stockholm with power 8.0/3.0 MWt/e: 1—core; 2—supporters; 3—heat exchanging structure.

The dimensions of the “miniature” Sealer reactor (capsule diameter Φc = 2.75 m and height—H = 5.9 m) enable one to incorporate it either in stationary or in transported systems. The value of the EC is 38%.

Nuclear devices operating with fast neutrons may be summarized as having the following tendencies:

  1. Conversion into micro co-generators. Yet, the expected capacity for domestic users of 0.03–0.05 MW has not been attained
  2. Pursuit of increasing the temperature of electricity generation (about 600–700°C) and use of coolants with thermal capacity larger than that of water (for instance, liquid metals such as potassium, sodium, and lead)
  3. Attaining more compact overall dimensions applicable in urbanized areas. Pursuit of higher reliability and more safety
  4. Increase of reactor energy efficiency during thermoelectric conversion employing more efficient thermodynamic cycles—Brayton's cycle for instance

3.2.1.2  Alchemic Future of the Thermal Technologies Used for Domestic and Industrial Needs?

Modern* interest to the secrets of alchemic “transmutation” of metals was aroused in 1989 after one or two centuries standstill, when M. Fleischmann and S. Pons from the University of Utah published their experimental finds (Fleischmann and Pons, 1989). They set forth a description of the successful conversion of nickel (Ni) into copper (Cu) under relatively low temperature. The transmutation reaction was strongly exothermal which impressed researchers. The released heat exceeded several times that of the chemical reactions. The explanation of this phenomenon involved the design of a new nuclear reaction of the atomic nuclei corresponding to copper (Cu) where the excess nuclear energy is released into the reactor core and converted into heat.

In modern physicochemistry, that process is known as cold fusion (cold nuclear synthesis [CNS]), while the devices where it takes place are called low-energy nuclear reactors (LENR). The cold fusion runs without emission of radioactive particles or radioactive co-products, since it takes place under the effect of so-called “slow neutrons.”* Hence, it is expected that such various “alchemic transmutations” would well fall into place in future thermal technologies for domestic and industrial needs.

During the last two decades after the publication of the paper of Fleischmann and Pons, many innovation companies and single inventors were inspired and motivated by the idea of implementing the CNS in the design and building of heat generators, boilers, or water heaters. One of them was the Italian inventor Andrea Rossi (Rossi, 2015). His fluid heater is of module type with power of the individual module amounting to 10 kW, while the package described in Cook and Rossi (2015), consists of 100 modules. It is under a 10-month acceptance test since the beginning of 2015, displaying the efficiency in the range 6 < EC < 30.

Figure 3.15a shows a scheme of one of the modules of eCat, which is shaped as a rectangular arm with dimensions 0.3 × 0.3 × 0.08 m consisting of a horizontal and a vertical section. The heater is periodically charged (every 6 months) with fuel consisting of 50% nickel, 20% lithium, and 30% lithium–aluminum hydrate. In addition, the module is charged with hydrogen and cooled with water. Water intake and exhaust temperatures and water outflow are measured (see Figure 3.15a). Rossi (2015) explains the high efficiency of the device via the following mechanism: “…A proton from a hydrogen atom enters, by the quantum tunneling effect, into a nucleus of Li-7 (i.e., a lithium nucleus of atomic weight 7), forming a nucleus of Be-8 (i.e., a beryllium nucleus of atomic weight 8), which then decays in a few seconds into two alpha particles (helium nuclei)….” The, excess energy of fracture of the interatomic bonds is released during the process flowing into the reactor. An axonometric view of a module package with power of 1 MWt is shown to the right of the scheme of eCat fluid heater—Figure 3.15b). It consists of 100 parallel-linked components undergoing 1-year trial operation (Cook and Rossi, 2015). Other inventors as for instance the Russian physicist A. Parkhomov (2014) designed and built analogs of Rossi's device but operating under different temperatures.

Fluid heater eCat of A. Rossi: (a) structure of heating module with power 10 kWt; (b) heating package with power 1 MWt, composed by 100 modules: 1—reactor; 2—water tank; 3—hydrogen tank; 4—vertical pipe; 5—control block.

Figure 3.15   Fluid heater eCat of A. Rossi: (a) structure of heating module with power 10 kWt; (b) heating package with power 1 MWt, composed by 100 modules: 1—reactor; 2—water tank; 3—hydrogen tank; 4—vertical pipe; 5—control block.

Generalizing the studies on the development of low-temperature nuclear reactors, we should note that pursuant to NASA studies the global energy consumption of modern civilization can be covered by only 1% of nickel produced worldwide.

3.2.2  Brayton Gas-Turbine Technology

This technology engages the direct Brayton cycle to eliminate the disadvantages of the Rankine cycle using the energy of the direct combustion of hydrocarbon fuels more effectively. This is the third modern application of the Brayton cycle, after gas turbine and jet engines. Formally, the technology arrangement was similar to that of the steam turbine.* Heat-converting equipment consists of water phase transformations including condenser, condensing reservoir, and feed pump, since fuel gases released in the CC operate as a working fluid. Figure 3.16a shows an arrangement of the devices realizing the gas-turbine cycle of Brayton, as well as the p–v diagram of the respective processes. The new element of the technological scheme is the turbo-compressor C for air compression performed prior to combustion (could be one stage or multistage of compression). The processes are similar to those running in the gas-turbine engine (see Section 2.3), and the efficiency of the gas-turbine cycle is assessed as

Gas-turbine technology of Brayton: C—compressor; CC—combustion heat exchanger. (a) Ideal cycle without utilization; (b) cycle including heating of the combustion products, utilization; (c) p–V diagram of the ideal cycle without utilization; and (d) p–V diagram of the cycle with the combustion products utilization.

Figure 3.16   Gas-turbine technology of Brayton: C—compressor; CC—combustion heat exchanger. (a) Ideal cycle without utilization; (b) cycle including heating of the combustion products, utilization; (c) p–V diagram of the ideal cycle without utilization; and (d) p–V diagram of the cycle with the combustion products utilization.

The first installations* of gas turbine had a separate CC from the remainder engine and operated at relatively low temperature, with small temperature difference and resulting low efficiency. The technology was improved in the 1970s in three ways

  • Increase of the temperature of the intake gases (1700 K) and increase of the conversion efficiency with co-generation—up to 80%–85%
  • Arrangement of all components (compressor, gas turbine, and CC) in a common casing or block—see Figure 3.16 (as is in the gas-turbine engine)
  • Expanding the range of available power (at present, the minimal power of gas microturbines is 3–6 kWe, while the maximal power approaches 600 MWe)

High-temperature resistant nickel and cobalt steels are used for gas microturbine manufacture. Nowadays, so-called “single crystal” technologies are also applied and the thermal schemes have improved. For instance, heat of the flue gases is recuperated and used for additional heating of the fresh but already compressed air, prior to its injection into the CC (Figure 3.16b). Other even more complicated schemes include additional combustion products heated by injection of additional fuel to increase gas temperature at the entrance of the turbine second section—see Figure 3.16c.

To increase efficiency, the air compressor should also be improved. Since the compressor is combined to the gas turbine (thermal engine), intercooling of the compressed air is performed (between section 1 and section 2) in order to decrease the operational power (see Section 2.5.3 discussing isothermal compression).

In conclusion, note that the gas-turbine technology for co-generation of electrical and thermal energy is applicable not only in industries where large power is needed but also in individual buildings (apartments, houses, etc.).

This is an essential advantage. Moreover, gas microturbine generators for individual use are compact and have dimensions of a washing machine or a refrigerator (see Figures 3.17 and 3.18). They are easily installed, their price is affordable, and the co-generation conversion coefficient is significant (over 80%). Yet, the availability of gas supply is operational condition sine qua non for those devices.

View of a micro gas turbine aggregate: 1—electrical generator; 2—output shaft; 3—disc clutch; 4—housing with bearing box; 5—air intake; 6—compressor; 7—CC; 8—gas turbine; 9—water shirt; 10—exhaust of combustion products.

Figure 3.17   View of a micro gas turbine aggregate: 1—electrical generator; 2—output shaft; 3—disc clutch; 4—housing with bearing box; 5—air intake; 6—compressor; 7—CC; 8—gas turbine; 9—water shirt; 10—exhaust of combustion products.

Micro gas co-generator: 1—heater; 2—micro turbine; 3—electrical generation output; 4—exchanger.

Figure 3.18   Micro gas co-generator: 1—heater; 2—micro turbine; 3—electrical generation output; 4—exchanger.

3.3  Employment of Thermoelectric and Co-Generation Technologies in the Design of Vehicle Hybrid Gears

Historically, the development of thermal, thermomechanical, and thermoelectric technologies stimulated and motivated innovations in transport. For instance, only 15 years after James Watt designed the steam thermal engine, it was mounted on the first steam car,* locomotive, and ship. Similar attempts were made in aviation, too, but the idea was not developed because of the lack of appropriate materials. The dependence of technology effectiveness on this interrelation was confirmed in time by the invention of internal combustion engines.

Today, however, prices of primary energy carriers are rising, and public control over hydrogen and nitrogen oxides emissions of car engines has intensified. Hence, new types of driving systems (so-called “hybrid drives”) are offered on the market, combining two types of power engines—thermal and electric. The task is to increase the efficiency of all land vehicles.

Hybrid drives have an almost age-old history. The pioneer in the field was the young car designer and manufacturer Ferdinand Porsche. In 1898 he designed and sold about 300 pieces of his famous hybrid car popular as the “Lohner–Porsche” model. Hybrid cars became a real market hit during the last century as a result of the continuous rise of fuel prices and the “rebate incentive programs” of the EU and the USA. The relatively low cost and good reliability made them attractive for millions of customers all over the world (almost 5.2 × 106 hybrid cars were sold in 2015 year). While hybrid cars engage more and more markets and gain more prestige, the market share of their “senior” brothers—hybrid locomotives, has shown very slow rate in the last 4–5 years. Yet, the present decade awaits their market “explosion.” These expectations are confirmed by the investment activity of the major companies in locomotive design, such as General Electric Transportation, Alstom, Siemens, Vosslon Loco, etc. They all have production capacity for basic hybrid components (high density accumulators, powerful inventors, highly efficient motor-generator aggregates, and reversible electric motors). The fact that the Canadian company Railpower, specializing in the manufacture of hybrid locomotives known as Green Goat, sold 32 pieces in 2005 (14 pieces just in the last quarter) and tripled their sales in 2006, is in support of the growing interest in those machines. According to the Pike Research report (Hurst, 2010) the hybrid locomotive could achieve a CAGR* of 19.4%, with annual unit sales up to 109 locomotives by 2020.

The manufacture of hybrid locomotives is considered to have started as far back as 1917 when Hermann Lemp's prototype of called AGEIR was assembled by General Electric (patented in 1913), but it was only a sample (see Figure 3.19). Since the first machine, several dozen types of hybrid locomotives were designed in North America and Europe during the last century.

Evolution of hybrid locomotives: (a) prototype of the hybrid locomotive

Figure 3.19   Evolution of hybrid locomotives: (a) prototype of the hybrid locomotive AGEIR of Hermann Lemp; (b) FT demonstration model #103 of general motors; (c) Germany's Deutsche Bahn AG; (d) SNCF Class B 81500 electro-diesel. 1—radiators; 2—electric motor; 3—thermal engine; 4—electric generator; 5—crew cabin; 6—fuel reservoir; 7—water reservoir; 8—air compressor.

As for transport operators–users of hybrid locomotives (with two engines), the introduction of these machines is a precondition for the economy of a significant amount of energy, avoidance of legal fines for carbon dioxide pollution, and improvement of the quality of transport. Economy of the primary energy carrier in hybrid drives is realized by recuperation of the extra power of thermal engines operating under nonsteady regimes that arise on hilly railway terrains (during train ascent or descent, at train pull up or departure, under engine floating, etc.). These are railway sections with speed restrictions depending on the number of train stations, railroad length, train type (passenger, fast, express, or freight), etc.

As is known, each speed change by 1 km/h (within the range 50 ≤ w ≤ 100 km/h) yields energy overconsumption varying by ±1%/km s−1. An impressive amount of primary fuel is lost in engine floating and at train pull up (about 1000 t/year when idling and 200 t/year for starting diesel fuel). A single rolling locomotive overconsumes significant amounts of primary energy carrier, and power estimation is about 1.4 × 106 kWh/year (1 kg/km diesel fuel and 5 kWh/km electric power). Last but not least, the large over consumption of fuel is due to the inability of the crew to economically drive the locomotive on hilly terrain (this is the human factor as a regulator of the engine power).

The idea of the hybrid drive is based on effective usage of the primary energy carriers (oil derivatives, biodiesel, ethanol, methanol, methane, natural gas or syngas, hydrogen, or electricity) via energy recuperation and regeneration. We consider here two schemes of the “hybrid model of energy consumption,” following the energy transfer to the shafts of the driving carts: a parallel scheme and a serial scheme.

3.3.1  Parallel Hybrid Scheme

At least two different engines are used here: thermal and electric. They are mechanically coupled, and the drive is due to the sum of their output tractions. The characteristic feature of that scheme is that even at the start of machine operation, the energy flux is divided into two autonomous parallel fluxes (Figure 3.20)

  • The first one is directed through the thermal engine 1 to the shaft of the traction carts 5.
  • The second energy flux is realized by a three-phase electricity generator 2 which is mechanically coupled with the thermal engine. Generator capacity is 10%–15%. The generation of electrical energy increases the efficiency of the thermal engine. Electricity is accumulated by the accumulator block 3 and then is used to drive the traction electric motor 4.

Arrangement of the energy fluxes in parallel driven locomotives: 1—basic traction motor (BTM); 2—electric generator; 3—accumulator block; 4—additional traction motor (ATM); 5—traction carts for the basic and additional motors; 6—resistor for dynamic pull up; 7—cart with the BTM (side view).

Figure 3.20   Arrangement of the energy fluxes in parallel driven locomotives: 1—basic traction motor (BTM); 2—electric generator; 3—accumulator block; 4—additional traction motor (ATM); 5—traction carts for the basic and additional motors; 6—resistor for dynamic pull up; 7—cart with the BTM (side view).

The thermal engine in this scheme is a basic traction motor whose power is found via an optimization procedure presented in what follows. (An engine operating after the diesel cycle is used as a thermal engine. Its efficiency amounts to 26%–28%). The additional electric motor is switched on when the mechanical system needs additional power (for instance, at train departure or ascent-see Table 3.2, column 5).

The diagram of the operational regimes of the equipment (including traction engines, generator, and accumulation system) during locomotive motion along a railway is also illustrated in Table 2.2. The table shows that the thermal engine operates continuously and under quasistatic loading. Assume that the engine has been correctly selected taking into account the specific loading applied.

Then, it can be exploited with minimal consumption of primary energy carriers and maximal efficiency. The table also shows that the system “generator–accumulator” (2–3) is designed to accumulate the extra mechanical energy generated by the thermal engine under all regimes, except for “departure.”

The additional electric motor in some locomotives not only “amplifies” traction of the thermal engine at loading “peaks”, but it can also operate jointly with the accumulator block 3 instead of using the resistor group 6 at dynamic pull up (columns 6 and 4 in Table 3.3).

Table 3.3   Diagram of the Operational Regimes of the Parallel Drive

Motion

Basic Traction Motor TM a

Generator

Accumulation

Additional Motor AM b

Regime of Generation

On flat terrain

+

+

×

×

Ascending a hill

+

+

+

×

Descending

+

+

↑↑

×

+

Departure

+

×

+

×

Intermediate pull up

+

+

↑↑

×

+

Notes:

a  TE—thermal engine (typical diesel engine).

b  EM—2 ÷ 4 asynchronous electric motors with wound rotor (frequency control), adapted for generator pull up and accumulation of the generated electricity in accumulators.

The generalized energy model of a parallel hybrid system is shown in Figure 3.21. A model of classical mono-engine drives is also shown for comparison.

Energy model of parallel hybrid drive of a locomotive. (a) Classical drivers. (b) Scheme parallel.

Figure 3.21   Energy model of parallel hybrid drive of a locomotive. (a) Classical drivers. (b) Scheme parallel.

The following equation of energy balance is used for parallel hybrids:

3.2
where EM is the amount of primary energy, necessary for the performance of mechanical work, ETE and ηTE are the consumed primary energy and the efficiency of the thermal engine, respectively, while EEM and ηEM are similar characteristics of the electric motor.

Introduce the ratio between the nominal powers of the thermal engine and the electric motor

as an argument of the parametric optimization to be further discussed. Then, the mechanical energy of Equation 3.2 will read
3.3
where τOp, h/year—operational time of the thermal engine and τInc, h/year—operational time of the electric motor. The expression derived will be used in our economic analysis.

The plots of the energy model of parallel hybrid drives in Figure 3.21 show that the expected energy efficiency amounts to 12%–15%, while during railway maneuver it can even reach 25%–30%. The expected economy of primary energy carriers suggests that hybrid locomotives will enter railway practice through the maneuvering equipment of large stations.

3.3.2  Serial Hybrid System (Serial Hybrids)

The energy distribution scheme for serial hybrid locomotives is shown in Figure 3.22. Two types of engines are also used in its physical realization—a thermal engine and an electric motor. Yet, they are not mechanically but energetically coupled.

Energy fluxes of locomotive serial hybrid drive: 1—on-board thermal engine; 2—on-board electric generator; 3—traction electric motors: 4—accumulator blocks; 5—gas micro-turbine; 6—on-board controller for inverter control of traction motors; 7—traction carts.

Figure 3.22   Energy fluxes of locomotive serial hybrid drive: 1—on-board thermal engine; 2—on-board electric generator; 3—traction electric motors: 4—accumulator blocks; 5—gas micro-turbine; 6—on-board controller for inverter control of traction motors; 7—traction carts.

The energy flux successively passes through the components shown in the scheme: initially through the thermal engine 1 (Figure 3.22), which is aggregated to the electric generator 2. The primary energy carrier is transformed into electrical energy within the engine-generator group. Exhaust gases with significant energy potential (about 60%) and high temperature and capacity are recuperated by a gas microturbine coupled to the electrogenerator 5. The expected conversion of the regenerated gas micro-turbo-aggregate, operating after Brayton cycle, is about 50%–60% of the energy potential of gases flowing out of the thermal engine.

The energy model of that hybrid system is shown in Figure 3.23. It is generally assumed that even without regeneration of the combustion products, energy economy due to the flexible control of the traction energy fluxes, only, will be equal to 18%–20% for railway locomotives. If an appropriate gas microturbine is present, the economy of primary energy carriers, compared to that of classical monovalence locomotives, will reach 40%–45%, and the total efficiency of hybrids will rise from 40% to 65%–70%.

Energy model of serial hybrid drive of locomotives.

Figure 3.23   Energy model of serial hybrid drive of locomotives.

The generated electricity is used for the supply of traction asynchronous motors 3 mounted on carts 7. Depending on the power needed, 2, 3, or 4 traction three-phase asynchronous motors with an autonomous frequency control are used, employing the control strategy of efficiency optimization. The diagram of the operational regime of the energy equipment (including traction motors, generator, and accumulation system) is also illustrated in Table 3.4.

Table 3.4   Diagram of the Operational Regimes of the Serial Drive

Motion

Main Engine TE a

Generator

Traction Motors and EM b

Generation Regime of EM

Accumulation

On plane terrain

+

+

++

×

↑↑

Ascending a hill

+

+

++++

×

Descending

+

+

×

++++

↑↑ ↑↑

Departure

+

+

+++

×

Intermediate pull up

+

+

×

++++

↑↑ ↑↑

Notes:

a  TE—thermal engine (typical diesel engine).

b  EM—2 ÷ 4 asynchronous electric motors with wound rotor (frequency control), adapted for generator pull up and accumulation of the generated electricity in accumulators.

As seen, the thermal engine and the aggregated electric generator operate continuously. Single traction electric motors are switched on only when mechanical energy is needed (all motors are switched on under extreme loading, only, and only half of them operate under nominal motion regime).

Traction motors switch over to generation regime at the time of descent (they operate as electrodynamic brakes but electric accumulators accumulate the generated energy).

Practically, locomotives with serial hybrid drives present a rather powerful electric power station on wheels (the power of the “evolution” locomotive, for instance, is 2387 kW*), moving with very high speed. The following balance energy equation holds for serial hybrids:

3.4
where EG and EAC are the generated and accumulated energy, respectively.

Using again the ratio βT/E, Equation 3.4 can be rewritten as

3.5

Considering that thermal engine efficiency ηTD is the ratio between the useful and the consumed energy, and it is identical to the so-called “real” efficiency set forth by

consumption of the primary energy carrier per hour (mass rate), needed for the performance of the economic analysis of a specific hybrid scheme, will take the form:
3.6
where ηE = ηTE is the real efficiency of the thermal engine; is indicative power; pIn is indicative pressure; nSt is stationary revolutions; is a drive complex comprising z cylinders, the working volume of the thermal engine Vh and the tact number Nt; is the lower heat generation capacity of the primary energy carrier (its typical value for liquid fuel is assumed to be ). We shall use these relations to estimate the economically profitable relation .

Serial hybrid schemes have the following advantages:

  1. The thermal engine operates under quasistatic and stable conditions, where maximal conversion coefficient of the electric generator is attained (a two-cycle engine operating within the diesel engine is preferred, typical for 900 tr/min). This generation group may be replaced in the future by a high-temperature FC.
  2. Traction asynchronous motors can be included in schemes for invertor control with respect to power and in those for energy recuperation at pull up.
  3. Consider the parameters and capacity of the exhausting gases and note their enormous “hidden” resource in increasing locomotive efficiency. Incorporation of gas microturbines for generation of electricity from combustion products and subsequent electricity accumulation can significantly optimize the use of primary energy resources.

3.3.3  Economical Aspects of the Hybrid Drives (Optimization of the Ratio between the Power of the Thermal Engine and That of the Electric Motor)

Today, transport operators are market subjects investing in transport comfort but accounting for to environment-friendliness too. They expect fast reimbursement of their investments and good dividends. Besides the ecological benefits due to the significant reduction of carbon and nitrogen emissions, hybrid technology for railway drives may have a direct economic impact reducing expenses for primary energy sources. The economy could measure up to 17%–20% for railway construction and up to 30%–35% for railway shunting.

The basic problem of the choice of a hybrid locomotive is the value of the ratio between the thermal and the electric power βT/E. The rational approach for the calculation of this quantity requires the use of economic methods and criteria. We propose here a method of finding the optimal power ratio βT/E, based on the dynamic method of assessing investment cash flows known as “net present value—NVC.” This method of optimization of the power ratio is based on an economical analysis. Its task is to find the sufficient hybrid (coupled) power needing minimal initial investments and allowing minimal expenses for primary energy.

A procedure observing the condition of minimal work for locomotive manufacture and operation is applied. Thus, a condition for the minimization of the discount “NVC” is set forth

3.7
where
  • are the single expenses KTD, KED, KG and KAB for the delivery of thermal engine, electric motor, generator, accumulators, and operating electronics, respectively. Traditionally, values Ki are determined by the capacity of the respective equipment. They can be expressed by the following generalized relation: Ki = Ci * Pi, i = TD, ED, G, AB. Coefficients CTD, $(Eu)/W; CED, $(Eu)/W; CG, $(Eu)/W, and (k, Ah/kW—transfer factor) can be found performing a marketing study of equipment costs or offers.
  • are expenses for current repairs, delivery of energy carriers, and staff salaries discounted at the instant of initial investment (amortization expenses for current repair T1 are not subject to discount since pursuant to the national accounting standards, they do not form a real cash flow).
  • is a discount coefficient of the types of future repairs expenses as compared to the initial cost ( , and rj is a risk norm, nj is a normative life cycle of the respective system of buildings). The risk norm is found via a model of assessing the capital assets (CAPM → rj = fr(rm − fr)β).

A practical approach to calculate the discount coefficients is to assume that the condition rj = i, is satisfied, where i is the level of official inflation (inflation index).

To find the profitable power ratio βT/E we should nullify the first derivative of the functional NVC = NVCT/E):

3.8
where
  • are the single expenses

Here,

is the discounted value of the primary energy carrier and are the discounted expenses for salaries of the locomotive team and auxiliary staff.

The average annual consumption of primary energy carrier mF, t/year is estimated based on the predicted amounts considering the hybrid scheme (Equations 3.2 and 3.3) and the specific terrain of the chosen route (a number of pull ups, waits and descents, other specific speed restrictions, etc.). The value of the energy carrier (vF, $(Eu)/t) is calculated accounting for the variable trend of the expected prices of the regional oil stock markets.

Finding the first derivative of the functional (3.8) with respect to βT/E and nullifying it, we obtain the following formula for the economically profitable power ratio:

3.9

The above formula for (βT/E)Opt illustrates the quadratic dependence between the nominal powers of the basic (thermal) engine and the additional (electric) motor, on one hand, and the market prices of the power equipment

, the discounted energy cost and the specific terrain conditions implicitly present in the derivative dmF/dβ, on the other hand. Note that dmF/dβ should be defined depending on the actual design requirements. Hence, the basic requirement to the delivery of hybrid locomotives should be the performance of a detailed economic analysis of their route of operation. This will guarantee a minimal time of investment reimbursement.

Hybrid drives used in railway, railway-maneuvering, or purely maneuvering locomotives combine the positive aspects of the thermal engine and the electric motor, namely

  • They admit flexible automatic regulation via digital systems and thus attain significantly more effective use of the primary energy carrier and significant energy economy by elimination of the human driving factor (the expected economy for railroad locomotives alone is about 17%–22%).
  • They guarantee steep slopes ascending (about 40%–45%) with nominal speed (up to 250 km/h) under optimization of traction and energy consumption. The new traction asynchronous motors with frequency control and efficiency of 95% save energy and provide high railway passability.
  • They possess higher relative power as compared to single source drives (diesel or electric ones).

The second positive quality of hybrid drives is the high autonomy of the transport operators and their rolling stock, and the devices do not admit deterioration of the central power supplied. At the same time, their maintenance and utilization are more complicated, making respective demands to the quality of training of railway and maintenance staff.

Finally, it is seen that the adoption of hybrid locomotives by local railway transport requires higher (by 20%–25%) initial investments. Note that powerful investors or the state itself can provide such funding.

3.4  Control Questions

  1. What is the difference between the direct and indirect technologies of generation of electricity?
  2. Specify the basic direct technologies.
  3. Can a body with wide banned zone be internally ionized? What does body internal ionization consist of?
  4. What is the structure of a photovoltaic cell?
  5. Specify the coefficient of conversion of the isomorphic photovoltaic cells. Specify that of polycrystalline photovoltaic cells.
  6. Which is the physical phenomenon that is the basis the Seebeck effect?
  7. Can one prepare “perpetuum mobile” using a single thermocouple?
  8. Specify the thermocouple components.
  9. How does a thermoelectric converter operate? In what area can it be applied?
  10. Which are the factors affecting the conversion coefficient of the Seebeck technology?
  11. What is the difference between the effects of Seebeck, Peltier, and Thompson?
  12. Where are the effects of Seebeck/Peltier applied? Specify an example.
  13. What is the difference between the spontaneous and controlled oxidation of energy carriers? How does the controlled oxidation proceed technologically?
  14. Which are the basic types of low-temperature FCs? What fuel do they operate with? Can they work using natural gas and methane?
  15. What is the maximal voltage generated by a FC? What is the electrical efficiency of low-temperature cells?
  16. How could one use low-temperature cells for the energy supply of buildings?
  17. What is the energy efficiency of low-temperature FCs under energy co-generation?
  18. Which FCs are high-temperature ones? Which are the carriers of energy through the electrolyte of solid-oxide and MCFCs?
  19. What fuels are used in high-temperature FCs? What is their electrical efficiency? What is their efficiency under the regime of co-generation?
  20. Specify the advantages and the disadvantages of low-temperature FCs.
  21. Give examples of the application of high-temperature FCs.
  22. What are the differences between technologies employing direct and indirect energy conversions?
  23. Which are the two most popular indirect technologies of electricity generation?
  24. Why has the Rankine technology developed prior to the industrial development of the gas-turbine technology?
  25. Which are the basic similarities between the steam-compressor and gas-compressor thermoelectric technologies?
  26. Specify the basic advantages of the Brayton thermoelectric technology.
  27. Why was Faraday's generator not applied industrially?
  28. Why did William Grove's technology, although its almost half-century popularity, give way to steam-turbine technology?
  29. How can a steam-turbine installation be adapted to operate under co-generation? What will be the rate of its efficiency increase?
  30. How can an old jet engine be used as a gas-turbine system for the generation of electricity?
  31. How can that engine be adapted to operate under co-generation?
  32. Consider a multistage compressor employed by the Brayton thermoelectric technology. How would intermediate air cooling affect energy efficiency? Why?
  33. Outline the areas of application of the Rankine technology, when heat is generated using renewable sources.
  34. Outline vehicles where steam-compressor technology is applicable.
  35. Give examples of co-generation in atomic power stations.
  36. What thermal technology would you use in the design of a plant for “daily waste utilization”?
  37. Propose a scheme of in-depth utilization of agricultural bio product waste.
  38. How could you arrange a project for energy supply of a farm?
  39. Where in transport could thermoelectric technologies be applied?
  40. What is the principal difference between a serial and a parallel hybrid scheme of vehicle drive?
  41. When does a parallel hybrid technology outrun a serial hybrid technology?
  42. How can efficiency of the serial hybrid technology be additionally increased?
  43. Specify a scheme of utilization of combustion products; exhaust the thermal engine of a hybrid drive.
  44. What are the restrictions imposed on the operation of combustion products potential from designer's point of view?

The term was introduced in 1600 by W. Gilbert (1544–1603).

The first electric generator was designed by A. Volta (1745–1827) in 1800, and it converted chemical work into electrical energy.

The photovoltaic cell operates according to the principle of internal ionization discovered by Becquerel (senior) in 1839. The first photovoltaic cells were manufactured in Bell Labs in 1954.

Oxidation in a catalytic environment was first described by the German physicist K. Schonbein (1938) but the first industrially applicable and commercialized technology for the generation of electricity was designed in 1842 by W. Grove (1811–1918).

The first electrostatic generator was designe by Otto von Guericke in 1650. The first patented one using electromagnetic induction for its operation was the single-pole disk generator of Michael Faraday (1831), while his industrial prototype was manufactured in 1832 by H. Picsius (1808–1835). However, those devices were not commercially realized.

Even technologies used in wind power stations or in hydroelectric power stations are InDTEG, since the initial energy is solar radiation which participates in the gigantic energy-conversion mechanisms of the Earth atmosphere (described in Chapter 3).

The cheapest cells are those of “amorphous Si.” Yet, they operate with the least efficiency (about 8%) under direct radiation. At the same time, they display affordable efficiency when operating in countries with moderate climate due to the specific climatic conditions (availability of large portion of diffusive radiation and variable temperature). More expensive cells are manufactured from monocrystal silicon (having 16% efficiency) and thin-layer polycrystal silicon (with 14%–15% efficiency). Their higher price makes them inappropriate for mass usage. The so-called “multilayer” cells display significantly larger efficiency (∼43%) in laboratory conditions.

The new photovoltaic cells are based on plastics, polymers, and bio ferments. These are cells manufactured from conducting plastics designed by A. Heeger (Nobel Prize winner 2000), cells manufactured from conducting polymers Olotrau of NSF, and chlorophyll cells of Gratzel cells.

Thermoelectric process is convertible. If two “n–p” contact couples are serially connected and switched to an external electric source, the electric current flowing is converted into heat (the cold body cools down—Peltier effect, and the hot body warms up—Thompson effect).

Kaganov's model called “two step model” is designed on the basis of e phenomenological mechanisms of interaction between phonons and electrons. It consists of two phases: heat transfer is realized via the directed motion of electrons of the free zone (without emf) during the first phase; the second phase consists of transfer of the kinetic energy of the moving electrons to the lattice atoms which start oscillating (generate phonons) with frequency ν depending on the temperature of their equilibrium state tl (static potential).

Here, the conductors are prepared from constantan (a copper–nickel alloy invented by E. Weston in 1887), where λ = 19.5 W/mK, and it is a semiconductor of “p” type.

The mean annual efficiency of an amorphous photovoltaic cell is about 8%.

FC are classical co-generators: the chemical work done under oxidation (burning) is converted into electric and thermal work. The real conversion coefficient of modern combustion is equal to 75%–80% under a co-generation regime.

French physicist C. A. de Coulomb (1736–1806).

In SOFC electricity carriers are the oxygen captions O(−), while in MCFC—the anions CO(+).

There are FCs which operate directly with alcohol (DAFC), but their power is low.

Individual PAFC generate power of up to 10 MW. In principle, their start is difficult (the electrolyte should be heated at every start since the phosphorus acid is solid below 40°C). They are very suitable for steady operational models.

M. Faraday (1791–1867) is considered to be the man who discovered electromagnetic induction in 1831, after having designed and published his single-pole generator (1832–1833). Yet, four years earlier (in 1827) the Hungarian engineer Anyos Jedlik (1800–1895) built a working electric generator but it was not officially recognized untill 1850.

They belong to the class of externally fired engine technologies where the combustion devices are physically insulated from the power devices—steam and gas turbines in this case.

A Scottish engineer, William John Macquorn Rankine, (1820–1872) who created in 1859 the steam engine theory, describing the engine operation via a state diagram. He introduced a number of thermodynamic terms.

Due to the low efficiency (∼20%), this technology consumes enormous quantity of primary energy carriers. It is the largest emitter of greenhouse gases yielding global warming.

The first power stations operating with gas turbines were built in the mid 20th century.

Known also as the solar thermal method, CSP (concentrated solar power) or TSS (trough solar system).

At present, about 3000 MW are installed worldwide, mainly in the USA—California and Nevada; about 100 MW in the EU—Grenada, Spain and 140 MW in the Negev desert. Investments amount to $7.14 × 106/MW.

This technology is also known as “The cycle of A. Kalina.

As is known from geology, the temperature of the Earth layer grows by 3°C per each 100 m depth. The so-called in-depth drilling of 3–5 km reaches the “hot” rocks, whose temperature is about 100–200°C (as in Basel, Switzerland, for instance).

The Rankine technology energy losses are balanced by the heat pump operation.

Drills are rather expensive and risky—the working fluid may be lost as was in Bad Vram, Stuttgart, for instance. The elimination of such problem costs about 2–4 million €. The whole investment amounts to 6.5 million €.

Waste from metallurgy, building or food industry.

Alchemy is an old practice originating from ancient Egypt (30–20 bc), having acquired a common context during the Late Middle Ages when attempts to “transmute” base metals into “noble” ones (particularly gold) were made. This term is used in the present book to generalize the studies in the field of low temperature nuclear synthesis (LTNS), where conducting metals (Ni, Pd, and others) are converted into chemical elements with higher molecular weight (Cu for instance) by hydrogen and deuterium absorption. These reactions are exothermal.

M. Fleischmann (1927–2012)—British chemist, born in Karlovy Vary, Czech Republic, premature announcement of the Cold Fusion process.

Nickel grid is used in the reactor, which filters a flux of deuterium (heavy nitrogen).

With power lower than 1.0 eV.

Due to Rossi's explicit denial to reveal the internal structure of the ECat heater, doubts about the correct measurement of the efficiency coefficient still remain.

A LENR technology, different from atom fission and fusion has been developed by NASA. The energy is generated at the interface between the nickel lattice and hydrogen atoms under the influence of an external force field oscillating at a frequency in the range 5 < f < 30 THz. This action ionizes hydrogen atoms, turning them into protons and stimulates a flow of slow (with low energy) neutrons. The nickel absorbs those neutrons instantly and goes into an unstable form. It regains its stability, becoming copper. The reaction is exothermic.

The first gas-turbine installation was designed by B. Bowery in 1939 in Noshal, Switzerland. The device power was 4 MW (NYSEG-Microturbine Demoot), and the conversion coefficient amounted to 18% only (its operational temperature however was within limits 537/277°C).

For instance, those in Noshal or those of Mitsubishi Heavy Industries (1940).

Over 15,000 patent applications are registered.

Invented in 1784 by William Murdoch (1754–1839).

Invented in 1800 by Richard Trevithic (1792–1882) and manufactured in 1803.

Patented in 1736 by Jonathan Hulls, built in 1763 by William Henry.

Compound annual unit growth rate.

In 1920, Baldwin Locomotive Works made a prototype of a “special” diesel-electric locomotive using electric components manufactured by Westinghouse Electric Company. The Kaufman Act prohibiting the use of steam locomotives was approved in the USA in 1923. This marked the end of the era of steam engines and the start of the era of diesel and diesel-electric locomotives. In 1929, the transport company Canadian National Railway became the first transport operator to use two diesel-electric locomotives manufactured by Westinghouse. In 1930, General Electric manufactured several small hybrid engines (the famous “44-tonner” hybrids) which were adopted by Burlington Railroad and Union Pacific in 1940 for passenger transport. Later, Southern Pacific was equipped with the two-valence (diesel-electric) locomotive EMD565 with power 4853 kW(6600 hp), as well as other improved models. The vehicles rolled along the Milwaukee Road (Santa Fe, California) till 1969–1970.

General Electrical Transportation—series Evolution, maximal road speed—177 km/h.

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