Fuel cells and electrolysers in future energy systems - VBN

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Fuel cells AFC PEMFC PAFC MCFC SOFC Name (electrolyte) Alkaline Polymer exchange membrane Catalyst Platinum Platinum 2 38 Immobilised phosphoric acid Immobilised molten carbon‐ ate Solid oxide conducting ceramic Platinum Nickel Perovskite 3 Operating temp. 40‐100 ºC 60‐200 ºC 180‐220 ºC 550‐700 ºC 500‐1000 ºC Fuel(s) Perfectly pure H2 Pure H2 or CH3OH Pure H2 H2, CO, NH3, hydrocarbons, alcohols H2, CO, NH3, hydrocarbons, alcohols Intolerant to Potential electric eff. % CO, CO2 CO, S, NH3 CO, S, NH3 S S 4 60 40‐55 45 60 60 Potential applications Mobile units space, military Mobile units, micro‐CHP Smaller CHP units Larger CHP units From large to micro‐CHP Table 1, Characteristics of the five main types of fuel cells and potential areas of use. [24‐37]. In all fuel cell types, the core consists of a cell with an electrolyte and two electrodes; the anode and the cathode. In Fig. 7, the reactions in different fuel cells are illustrated. Hydro‐ gen and oxygen are converted into water producing electricity and heat. The conversion of fuels takes places in a chemical process, in which the catalytic active electrodes convert the fuel into positive ions and oxygen into negative ions. The precise reactions depend on the type of fuel cell. The ions cross the electrolyte and form water and possibly CO2, depending on the fuel and the fuel cell. Only protons can cross the electrolyte while creating a voltage difference between the anode and the cathode in the cell; thus, the electrons cross to the anode section in an external circuit. The output is DC electricity from the flow of electrons from one side of the cell to another. [25] The advantages of lower temperature fuel cells are mainly related to the fact that they are compact, lightweight and have a quick start‐up and shut‐down potential. This, combined with the fact that the efficiency of the fuel cells cannot compete with other larger power‐ producing technologies, makes transport and mobile applications most promising. In these cases, fuel cells can compete with the efficiencies of existing technologies. They may poten‐ tially contribute to the supply as small‐scale micro‐CHP plants. For larger stationary applica‐ tions, other technologies have already today proven to have better efficiencies. Alkaline fuel cells (AFCs) are highly reliable, rather compact, and have low material costs; but no widespread commercial use is expected, because of the costs related to the exten‐ sive gas purification needs [25;26]. AFCs have been used for extraterrestrial applications, 2 May also consist of platinum in combination with ruthenium and molybdenum depending on the CO contents in the fuel. This is espe‐ cially the case of DMFC. In HT‐PEM, the catalyst is often pure platinum. 3 May contain nickel if the fuel is hydrocarbons, e.g. natural gas or methanol. 4 Potential efficiencies depend on the stack load. Total efficiency may be more than 90 per cent, but is dependent on the cooling system and the operation temperature. For AFC, the efficiency is dependent on the existence of perfectly pure hydrogen at the anode and pure oxygen at the cathode. For HT‐PEMFC, a 55 per cent net system efficiency has been achieved. For SOFC, the efficiency is dependent on the development of cell materials, anode gas recirculation and integrated steam reforming when using other fuels than hydrogen. In MCFC and SOFC, a 70‐75% electricity efficiency can be achieved, when combined with gas turbines and/or steam turbines.
e.g. the manned Apollo missions, which has no price issue, availability of pure oxygen prob‐ lems, and in which the excess water is useful for astronauts. The lifetime of AFCs is rather short and is not expected to increase with further research; thus, mainly mobile applica‐ tions should be considered. In recent years, research has shown that the purification needs may be lower than expected. Micro‐CHP based on AFC is also still being investigated [27]. Phosphoric acid fuel cells (PAFCs) are widely used today as emergency power and stand‐ alone units in hospitals, schools and hotels. They have been commercially available since 1992, but the costs of PAFCs are still about three times higher than those of other compa‐ rable alternatives. The main problems related to PAFCs are based on the fact that they are dependent on noble metals for the electrodes and the fact that their reported efficiencies are not considerably better than those of other technologies. [24‐26;38] The AFCs and the PAFCs are often considered the most developed fuel cells of the five types mentioned [28]. However, although variants of both types are still developed, it will hardly be possible to improve the two main challenges, namely the lifetime of AFCs and the cost level of PAFCs, respectively [25;27]. Fig. 7, Schemas of different fuel cell types 39
Page 1: Fuel cells and electrolysers in fut
Page 5 and 6: Tilegnet mine forældre Karl Kristi
Page 7 and 8: Abstract Efficient fuel cells and e
Page 9 and 10: Dansk resumé Effektive brændselsc
Page 11 and 12: Contents ABSTRACT .................
Page 13: Appendices I. B. V. Mathiesen and M
Page 16 and 17: In this dissertation, fuel cells an
Page 18 and 19: Nomenclature Power generation and r
Page 20 and 21: Fuel cells and electrolysers have t
Page 22 and 23: In December 2006, a plan for how an
Page 24 and 25: a) Fuel 107 units b) Fuel 87 units
Page 26 and 27: In the current energy system, elect
Page 29 and 30: 2 The energy system analysis method
Page 31 and 32: taxes. Output consists of annual en
Page 33 and 34: 3 Reference systems and the design
Page 35 and 36: the IDA 2030 system, and, in an upd
Page 37: gies to improve the integration of
Page 42 and 43: PEMFCs are characterised by a rathe
Page 44 and 45: tion time in portable devices [25].
Page 46 and 47: Except when pure hydrogen is used,
Page 48 and 49: they supply. In transport applicati
Page 50 and 51: Thus, when in operation, all types
Page 52 and 53: CHP, and under four ancillary servi
Page 54 and 55: Grid‐stabilising plants 30 per ce
Page 56 and 57: In the IDA 2030 energy system, a sh
Page 58 and 59: PES excl. wind power (TWh) PES excl
Page 61 and 62: 6 Applications of solid oxide fuel
Page 63 and 64: tion of power plants and improve th
Page 65 and 66: hydrogen Central and Local FC‐CHP
Page 67 and 68: The combinations of seven different
Page 69 and 70: when fuel prices are high, especial
Page 71 and 72: 6.4 Socio‐economic consequences I
Page 73 and 74: 7 Individual household heating syst
Page 75 and 76: kW/kW‐average 3 2 1 0 Heat Demand
Page 77 and 78: Fig. 19, Annual fuel consumption of
Page 79 and 80: Fuel (TWh/year) 14 12 10 8 6 4 2 0
Page 81 and 82: M. EUR/year 800 700 600 500 400 300
Page 83 and 84: Fuel (TWh/year) 18 16 14 12 10 8 6
Page 85 and 86: d) Compared with other fossil fuel
Page 87 and 88: systems are installed, such low tax
Page 89: given heat production. A system is
Page 92 and 93:
energy systems in the coming years,
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The second of the two types of ener
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Wind power Fuel Power plant CHP Boi
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has been used for identifying the n
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In Fig. 37, the effects of using th
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In the energy system analyses, HP p
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M€/TWh fuel saved 120 100 80 60 4
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For all alternatives, doubling the
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9 Life cycle screening of solid oxi
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chromium alloy used in the intercon
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In terms of primary energy consumpt
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ures on the path towards future 100
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plemented first. The socio‐econom
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socio‐economic calculations)," Da
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[40] M. C. Tucker, G. Y. Lau, C. P.
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[69] H. Lund, "Excess electricity d
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Appendix I 3
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2 Fuel cell types In most countries
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transport or smaller devices. DMFCs
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combined with the water management
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While interconnectors diffuse the g
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the systems are less sensitive to p
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Annex I. AFC Technology (2008‐pri
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Annex III. LT‐PEMFC Technology (2
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Annex V. MCFC Technology MCFC‐sys
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References [1] B. V. Mathiesen and
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[32] J. R. Selman, "Molten‐salt f
Page 150 and 151:
[64] L. Blum, H. P. Buchkremer, S.
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Abstract Solid oxide fuel cells and
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West Denmark Norway Germany 31 Swed
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2 Ancillary service requirements An
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have been identified. For SOFCs, me
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As a reference for the analyses, a
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• Wind turbines and locally dispa
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In the first ancillary service scen
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10 Acknowledgements This paper is p
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[34] M. C. Tucker, G. Y. Lau, C. P.
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Research Signpost 37/661 (2), Fort
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Energy system analysis of fuel cell
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Page 183 and 184:
Page 185 and 186:
Page 187 and 188:
Page 189:
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Solid oxide fuel cells in renewable
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now, the changes in the Danish ener
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In the next step, a market exchange
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Extensive investments have to be ma
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2.4 Costs of fuels, fuel handling,
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Input: BAU 2030 Electricity system
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potential for producing heat in FC
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cies do not increase due to larger
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In dry years, FC‐CHPs generate pr
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4 Conclusion SOFC can improve the f
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[23] Danish Energy Authority, "Frem
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Comparative energy system analysis
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2 Methodology In the methodology, t
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to fuel at households of 72 per cen
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listed in table 5 are from the Dani
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Fig. 4, Annual fuel consumption of
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enables a heat supply for at least
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The COP of both HP systems have to
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operated simultaneously; that the C
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The HP systems analysed for 300,000
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M. EUR/year 1,300 1,100 900 700 500
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[11] B. V. Mathiesen and H. Lund, "
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Comparative analyses of seven techn
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energy system analysed. Outputs are
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illustrates the excess electricity
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Input: DEA 2030 (market) 123 Refere
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Wind power Fuel Power plant CHP Boi
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of driving at full capacity. The di
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Open energy system, 25 TWh annual w
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Marginal PES excl. wind (TWh) 0,0 -
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educes excess production and fuel s
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M€/TWh fuel saved 120 100 80 60 4
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[8] M. Little, M. Thomson, and D. I
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[37] Danish Energy Authority, Elkra
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Long term perspective for balancing
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Contents 1 Technology Description .
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7.2.1 Fuel cell types In Table 7-2
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In the SOFCs the electrolyte allows
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In the same energy system SOFC CHP
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400$/kW before 2015 also for SOFC s
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unning temperature is lowered to 55
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[12] B. V. Mathiesen and H. Lund, "
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Abstract Integrated transport and r
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phase. The detailed energy system a
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The increase in the international a
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2030, this results in 28.56 PJ net
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ate to 6 per cent. The result is th
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Appendix IX 171
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2 The design of 100% renewable ener
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4 documentation of the model can be
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6 1.000 900 800 700 600 500 400 300
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8 combined in order to reach the ta
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Uncertainties related to the identi
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tion of one marginal technology is
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policies for changes and a projecti
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The policy from 1996 [24] built on
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tial LCA studies should include sev
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6 Case study of the affected electr
Page 319 and 320:
adding waste to the BAU energy syst
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fected; thus, reinvestments are aff
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Appendix A LCA‐Study Miljømæssi
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LCA‐Study LCA of Danish fish prod
Page 328 and 329:
[16] G. Finnveden, J. Johansson, P.
Page 330:
[46] N. Mattsson, T. Unger, and T.
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