Fuel cells and electrolysers in future energy systems - VBN

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PES excl. wind power (TWh) 290 280 270 260 250 240 230 220 210 Closed energy system Danish ref. 2030 - w. restrictions Danish ref. 2030 - SOFC w. restrictions Danish ref. 2030 - SOFC no restrictions 0 5 10 15 20 25 30 35 40 45 50 Wind power production (TWh) Figure 7-5: Primary energy consumption (PES) excl. wind power. 7.4 Assessment of fuel cells In the perspective of using fuel cells for integration of fluctuating renewable energy the SOFCs are the most promising. These cells have the advantage of significantly higher electricity efficiency than competing technologies and fuel flexibility. Fuel cells in general also have the advantage of fast regulation abilities combined with excellent part-load efficiencies. Additionally scaling the cells from W to kW to MW is possible and does not influence the efficiencies of the cells. The feasibility of the scaling however depends on the market at hand and the fuel cells characteristics. Wind integration can also be preformed with other types of fuel cells than the SOFCs such as PEMFC in micro-CHP. These however have the disadvantage that the efficiency is lower and require pure hydrogen. PEMFCs have advantages for mobile applications replacing internal combustion engines and batteries were feasible. For mobile applications the PEMFCs have the advantages that they can compete with internal combustion engines with fast start-up, fast regulation abilities and better efficiencies. In comparison with batteries fuel cells have the advantage that they have higher energy densities and can be refilled instantly, however the storage problems have yet to be solved. As storage and energy carriers methanol and ethanol are the most promising in regards to mass and volume. These can be used directly in SOFCs but have to be reformed for use in PEMFC. New technologies that can provide energy system flexibility, such as SOFCs, heat pumps and heat storage technologies are more important than storing electricity as hydrogen via electrolysis in energy systems with high amounts of wind [12]. Unnecessary energy conversions should be avoided. However in future energy systems with wind providing more than 50% of the electricity and with the best measures for improving flexibility have already been taken, making fuels via electrolysis is one of the alternatives to integrate more renewable energy. Creating the road map to a 100% renewable energy systems require difficult choices between balancing fluctuating renewable with hydrogen production or electric cars, and on the other hand using biomass and bio fuels [15]. Fuel cells can have an important role in these future energy systems. 7.5 Investment cost At the moment most types of fuel cells are at a development stage where only demonstration plants are being produced. The cost of fuel cells is still several thousand dollars pr. kW effect. Both PEMFC and SOFC, which are considered to be the most promising cells, are expected to be competitive with other competing technologies within the next 10 years. The goal for the US Department of Energy (DOE) is that the prices of stationary application for SOFCs should be Long term perspective for balancing fluctuating renewable energy sources: 8 Fuel cells for balancing fluctuating renewable energy sources
400$/kW before 2015 also for SOFC systems combined with gas turbines. The system should have 40.000 hours of durability. Reaching these cost reduction estimates require that the obstacles outlined above are dealt with. The cost for stationary SOFCs may prove closer to 1.000 $/kW [16]. If the durability can be lower the costs can also be lower and SOFCs are also considered for mobile application. For PEMFC for transportation the goal for DOE in 2015 is 30$/kW in 2015 with a durability of 5.000 hours [17]. The costs for other applications and for the other mentioned fuel cells are expected to be higher, though these may have other advantages [1]. It should also be mentioned that the maintenance cost can prove to be rather high in comparison with other technologies, especially concerning fuel cells for stationary appliances. The fuel cells them selves require little daily attention and can in principle be run automatically. However the stacks of cells in stationary appliances have to be changed periodically because of celldegradation. Today this is connected to rather high cost because of the ceramics used. As these get thinner or replaced by other materials in future third generation metal-supported cells the maintenance costs may be reduced. For PEMFC the main problems concerning cost may not be the cells themselves, but the storage and reforming systems. For SOFCs the infrastructure and storage problems and cost are significantly lower because of the internal reforming of hydrocarbons. When using the PEMFCs for mobile or stationary appliances the cost for new infrastructure and for reforming of fuels into hydrogen have to be added. 7.6 Environmental impacts The environmental impacts of a fuel cell in operation are minute in comparison with other technologies. The global warming potential and emissions of CO2 is directly linked to the fuel used in the cells. When using fossil fuels such as natural gas in SOFCs the CO2 emissions pr. kWh are however lower than the traditional gas turbines, because of higher efficiencies. Other emissions such as sulphur, NOx and CO are expected to be very low, because of the fuel pre-treatment, higher efficiencies and direct chemical conversion. Sulpher has to be removed from the fuels so SOx is not a problem like it is in combustion technologies. The sulphur emissions are virtually nonexistent. The NOx emissions are also significantly lower and these emissions are connected only to the catalytic burner using unused fuel from the fuel cell for heat in the fuel supply system. The emission of CO is rather low for all cells, as it is used as a fuel in the higher temperature cells, and is poison and hence removed for the low temperature cells. There may be emissions of unused hydrocarbons, but this can be reduced in the system design. No non methane volatile organic compounds or NMVOC and particles are emitted from the cells. Also the cells are very quiet with almost no sound in operation. Apart from the environmental impacts and resource consumptions in the operation of fuel cells impacts in a life cycle perspective is also important to investigate. Here one of the two most promising fuel cells, the SOFC, is investigated in a life cycle perspective. The primary energy consumption for the production the fuel cell is used as an indicator of the environmental impacts and resource consumptions. The development within the field of SOFCs has commenced from first generation electrolyte-supported cells, to second generation anode-supported cells. These are less costly to produce and also have less internal resistance [10]. The third generation metalsupported cells are now being developed and will continue on this course, making the cells more efficient. In Figure 3-1 the distribution of primary energy consumption for the production of materials and manufacturing of a first generation cell and system is illustrated. The dataset used in Figure 3-1 Long term perspective for balancing fluctuating renewable energy sources: Fuel cells for balancing fluctuating renewable energy sources 9
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Fuel cells and electrolysers in fut
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Tilegnet mine forældre Karl Kristi
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Abstract Efficient fuel cells and e
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Dansk resumé Effektive brændselsc
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Contents ABSTRACT .................
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Appendices I. B. V. Mathiesen and M
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In this dissertation, fuel cells an
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Nomenclature Power generation and r
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Fuel cells and electrolysers have t
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In December 2006, a plan for how an
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a) Fuel 107 units b) Fuel 87 units
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In the current energy system, elect
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2 The energy system analysis method
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taxes. Output consists of annual en
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3 Reference systems and the design
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the IDA 2030 system, and, in an upd
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gies to improve the integration of
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Fuel cells AFC PEMFC PAFC MCFC SOFC
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PEMFCs are characterised by a rathe
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tion time in portable devices [25].
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Except when pure hydrogen is used,
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they supply. In transport applicati
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Thus, when in operation, all types
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CHP, and under four ancillary servi
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Grid‐stabilising plants 30 per ce
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In the IDA 2030 energy system, a sh
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PES excl. wind power (TWh) PES excl
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6 Applications of solid oxide fuel
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tion of power plants and improve th
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hydrogen Central and Local FC‐CHP
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The combinations of seven different
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when fuel prices are high, especial
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6.4 Socio‐economic consequences I
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7 Individual household heating syst
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kW/kW‐average 3 2 1 0 Heat Demand
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Fig. 19, Annual fuel consumption of
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Fuel (TWh/year) 14 12 10 8 6 4 2 0
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M. EUR/year 800 700 600 500 400 300
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Fuel (TWh/year) 18 16 14 12 10 8 6
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d) Compared with other fossil fuel
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systems are installed, such low tax
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given heat production. A system is
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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
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[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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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
Page 225 and 226: Fig. 4, Annual fuel consumption of
Page 227 and 228: enables a heat supply for at least
Page 229 and 230: The COP of both HP systems have to
Page 231 and 232: operated simultaneously; that the C
Page 233 and 234: The HP systems analysed for 300,000
Page 235 and 236: M. EUR/year 1,300 1,100 900 700 500
Page 237: [11] B. V. Mathiesen and H. Lund, "
Page 241 and 242: Comparative analyses of seven techn
Page 243 and 244: energy system analysed. Outputs are
Page 245 and 246: illustrates the excess electricity
Page 247 and 248: Input: DEA 2030 (market) 123 Refere
Page 249 and 250: Wind power Fuel Power plant CHP Boi
Page 251 and 252: of driving at full capacity. The di
Page 253 and 254: Open energy system, 25 TWh annual w
Page 255 and 256: Marginal PES excl. wind (TWh) 0,0 -
Page 257 and 258: educes excess production and fuel s
Page 259 and 260: M€/TWh fuel saved 120 100 80 60 4
Page 261 and 262: [8] M. Little, M. Thomson, and D. I
Page 263: [37] Danish Energy Authority, Elkra
Page 267 and 268: Long term perspective for balancing
Page 269 and 270: Contents 1 Technology Description .
Page 271 and 272: 7.2.1 Fuel cell types In Table 7-2
Page 273 and 274: In the SOFCs the electrolyte allows
Page 275: In the same energy system SOFC CHP
Page 279 and 280: unning temperature is lowered to 55
Page 281: [12] B. V. Mathiesen and H. Lund, "
Page 285 and 286: Abstract Integrated transport and r
Page 287 and 288: phase. The detailed energy system a
Page 289 and 290: The increase in the international a
Page 291 and 292: 2030, this results in 28.56 PJ net
Page 293 and 294: ate to 6 per cent. The result is th
Page 295: Appendix IX 171
Page 298 and 299: 2 The design of 100% renewable ener
Page 300 and 301: 4 documentation of the model can be
Page 302 and 303: 6 1.000 900 800 700 600 500 400 300
Page 304 and 305: 8 combined in order to reach the ta
Page 307 and 308: Uncertainties related to the identi
Page 309 and 310: tion of one marginal technology is
Page 311 and 312: policies for changes and a projecti
Page 313 and 314: The policy from 1996 [24] built on
Page 315 and 316: tial LCA studies should include sev
Page 317 and 318: 6 Case study of the affected electr
Page 319 and 320: adding waste to the BAU energy syst
Page 321 and 322: fected; thus, reinvestments are aff
Page 323 and 324: Appendix A LCA‐Study Miljømæssi
Page 325: LCA‐Study LCA of Danish fish prod
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[16] G. Finnveden, J. Johansson, P.
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[46] N. Mattsson, T. Unger, and T.
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