Fuel cells and electrolysers in future energy systems - VBN

4 Conclusion
SOFC can improve the fuel efficiency in future renewable energy systems by replacing gas turbines. Large
central FC‐CHP plants based on hybrid SOFC gas turbines create marginally larger fuel savings than smaller
local SOFC‐based CHP plants; however, both technologies are able to improve fuel efficiency compared to gas
turbines. In renewable energy systems, local SOFCs are very important, as they can increase fuel efficiency
significantly compared to single cycle gas turbines. On the other hand, large FC‐CHPs compete with combined
cycle gas turbines, which are not significantly less efficient. If the efficiency and cost targets for SOFC are met,
they can improve fuel efficiency and generate lower long‐term production costs than gas turbines.
The expansion of CHP plant capacity can improve fuel efficiency and serve as the first step on the path
towards integrated renewable energy systems. The expansion of CHP with central FC‐CHP may be limited, as
this requires large connected rural areas. In renewable energy systems, CHP can reduce costs and increase
fuel efficiency. In such case, Local FC‐CHPs have better fuel efficiencies and a higher feasibility than Micro FC‐
CHPs. Electrolysers may contribute to the integration of excess electricity. Fuel consumption, however, may
increase if connected to Micro FC‐CHP, because a fixed demand must be met and excess electricity
production cannot always cover the electricity demand. In the most efficient integrated renewable energy
systems, electrolysers are less important, since other technologies are able to integrate most of the
fluctuating renewable energy. However, in 100 per cent renewable energy systems, electrolysers may be
important in terms of replacing other fuels.
Both efficiencies and costs are uncertain for technologies which are still at the development stage. However,
the SOFCs have the potential for reducing the dependence on fuels in future energy systems. Local 5‐40 MW
size SOFC FC‐CHPs that can improve the efficiency of SCGT distributed CHP plants are particularly important,
as is the development of SOFC to operate with the fluctuation of renewable energy instead of as base load
plants.
References
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[2] European Environment Agency, "EN20 Combined Heat and Power (CHP)," European Environment
Agency, Copenhagen,2007.
[3] Eurostat, "Share of Combined Heat and Power generation (CHP); Share of renewable energy, including
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[4] B. V. Mathiesen and M. P. Nielsen, "The nature of fuel cells," Final draft, ready for submission,
Sept.2008.
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