Fuel cells and electrolysers in future energy systems - VBN

Comparative energy system analysis of individual
house heating in future renewable energy systems
Abstract
Brian Vad Mathiesen* 1 , Henrik Lund 2 , Frede Hvelplund 3 and Poul Alberg Østergaard 4
Department of Development and Planning,
Aalborg University, Fibigerstræde 13, DK‐9220 Aalborg, Denmark,
e−mail: 1 bvm@plan.aau.dk, 2 lund@plan.aau.dk, 3 hvelplund@plan.aau.dk, 4 poul@plan.aau.dk
Individual house heating and the integration of renewable energy are key issues when addressing global
warming. One future technology which could address this is fuel cell (FC) micro combined heat and power
(CHP) operated on natural gas, biogas or hydrogen. Here, this system is compared to the conventional tech‐
nologies: heat pumps (HP), natural gas and wood pellet boilers. They are analysed hour‐by‐hour in renewable
energy systems with and without large amounts of district heating CHP plants. As FC systems are often con‐
nected to the utilisation of excess electricity, both systems have a wind power share of 50 per cent. HP has
the lowest fuel consumption, CO2 emissions and socio‐economic costs. Natural gas and biogas micro FC‐CHP
are more efficient than wood boilers; however, they use approx. the same amount of fuel as gas boilers and
have higher costs. Electrolysers with micro FC‐CHP are rather inefficient and economically unfeasible. If the
aim is to reduce CO2 emissions it can be recommended to increase the use of HP, replace boilers and use the
fuels in CHP plants instead. In the case of Denmark, however, the current tax system encourages the use of
boilers and hinders the use of HP. A two‐stage tax reform is introduced taking into account fuel efficiency and
“opportunity costs” of using scarce biomass and fossil fuels in inefficient boilers instead of CHP plants.
Keywords – distributed generation, micro CHP, fuel cells, electrolysers, hydrogen, heat pumps, wind power,
renewable energy planning, CO2 abatement measures, energy storage
1 Introduction
The heating demand of Danish dwellings accounts for 24 per cent of the total Danish primary energy supply.
42 per cent is covered by fuel‐efficient district heating and 23 per cent by renewable energy; mainly wood but
also heat pumps and solar thermal systems. The remaining 35 per cent of the supply is covered by individual
oil and gas boilers or electric heating [1;2]. Hence, there is still a considerable potential for fossil fuel savings
in the heating of Danish dwellings.
In addition, electricity is increasingly produced by non‐dispatchable technologies, such as wind turbines or
local CHP plants supplying heat to district heating grids. In 2006, wind turbines accounted for 17 per cent of
the Danish electricity demand, slightly less than the 18 per cent of the previous two years [1].
FCs operated on hydrogen are often seen as one of the potential bridges closing the gap created by a world‐
wide further expansion of wind power and other intermittent renewable energy sources. FCs are also seen as
the means of integrating renewable energy sources into the heating of individual dwellings. Schenk et al [3]
find that hydrogen is beneficial at large penetrations of wind power in the Netherlands; while Segura et al [4]
define hydrogen systems as back‐up systems for large‐scale wind farms, though the modest efficiency of
* Corresponding author. Tel.: +45 9940 7218; fax: +45 9815 3788; E‐mail address: bvm@plan.aau.dk (B. V. Mathiesen).
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