Wind energy storage technologies - Wind Power Generation and Wind Turbine Design - page 692

Hydrogen is passed over the anode (negative) and oxygen is passed over the cath-
ode (positive), causing hydrogen ions and electrons to form at the anode. The elec-
trons fl ow through an external circuit to produce electricity, whilst the hydrogen ions
pass from the anode to the cathode. Here the hydrogen ions combine with oxygen to
produce water. The energy produced by the various types of cells depends on the
operation temperature, the type of FC, and the catalyst used (see Table 2). FCs do not
produce any pollutants and have no moving parts. Therefore, theoretically it should
be possible to obtain a reliability of 99.9999% in ideal conditions [30].

4.9.4.1 Cost of FC
All FCs cost between

8000/kW which is very high, but typical of
an emerging technology [2]. These costs are expected to reduce as the technology
ages and commercialization matures.

€ 500/kW and €

4.9.4.2 Future of FC
Immediate objectives for FCs include harnessing the waste heat more effectively to
improve co-generation effi ciency and also, combining FCs with electrolysers as a sin-
gle unit. The advantage being lower capital costs although resulting in lower effi ciency
and increased corrosion [2]. FCs are a relatively new technology with high capital costs.
However, with characteristics such as no moving parts, no emissions, lightweight,
versatility and reliability, this is defi nitely a technology with a lot of future potential.

4.9.5 Disadvantages of HESS
The primary disadvantage with hydrogen is the huge losses due to the number of
energy conversions required. Typically in a system that has high wind energy pen-
etrations, by the time that hydrogen is actually being used for its fi nal purpose it has
gone through the following processes with corresponding effi ciencies: ( 1 ) hydrogen
is created by electrolysis - 85% effi cient, (2) the hydrogen is stored - 65-70% effi -
cient, (3) hydrogen is consumed in a FC car, power plant, or CHP unit - effi ciency
of 40-80%. This results in an overall effi ciency ranging from 22 to 48%. In addi-
tion, this process assumes only one storage stage within the life of the hydrogen
where as typically more than one storage stage would be necessary, i.e. stored
when created, and stored at the location of use. Therefore, by implementing a
“hydrogen economy”, the effi ciency of the system is very low that could result in
very high energy costs and very poor utilization of limited resources such as wind
or biomass. In summary, although the HESS offers huge fl exibility, this fl exibility
is detrimental to the overall energy system effi ciency.

4.9.6 Future of HESS
The use of hydrogen within the transport and electricity generation industries is
expected to grow rapidly as electrolysis, storage techniques, and FCs become more
commercially available. There are very ambitious hydrogen programs in the EU,
USA and Japan, indicating increasing interest in hydrogen technology. Iceland is
attempting to become the fi rst 'hydrogen country' in the world by producing hydro-
gen from surplus renewable energy and converting its transport infrastructure from
fossil fuels to hydrogen. In Norway, Statkraft plans to connect an electrolysis unit