Fuel cells and electrolysers in future energy systems - VBN

In Denmark, a current wind power capacity of 3,149 MW is installed at 5,200 different locations, which is able
to supply approx. 20 per cent of the electricity demand [11;12]. Another 2,200 MW is small CHP plants or
industrial production at more than 700 different locations, of which more than 650 are smaller than 10 MW
[12]. In addition, the energy supply system also includes 17 central power plants (PP) and CHP plants with a
total capacity of 7,968 MW [13]. This current energy supply status is the result of a transition from a classical
centralised system with very few and large PP to a distributed system, over the last 20 years [14]. In Fig. 1, the
development of the installed capacities is illustrated and the diminishing fraction of central plants is clear.
The development towards an even more distributed generation system is expected to continue. In 2012, the
total wind power installed is planned to be 4,124 MW, as offshore wind power is planned to increase from
423 MW in 2008 to 1,223 MW in 2012 and onshore wind power is planned to increase by 175 MW in the
same period.
MWe
18,000
16,000
14,000
12,000
10,000
8,000
6,000
4,000
2,000
0
Development in Danish generation capacity
1987 1992 1997 2007 2012
Fig. 1, Capacities of technologies in the Danish energy system from
1987 until 2007 and in the anticipated scenario in 2012.
30
Offshore wind
Onshore wind
Private producers
Decentral CHP
Central PP/CHP
In 2007, electric peak load was 4,981 MW in the summer and 6,124 MW in the winter. Minimum demand was
2,303 MW in the summer and 2,868 MW in the winter. Both in winter and summer time, it is hence possible
for the distributed generation to cover the electricity demand.
The Danish electricity system consists of a western and an eastern system, of which the western system by far
has the largest stock of wind turbines and distributed local CHP. The 400 kV transmission grid is illustrated in
fig. 2. Data available from the Danish TSO (Transmission System Operator) Energinet.dk reveals that, in 2007,
more than 300 hours could have been supplied solely by distributed generation in the western part; however,
partly due to ancillary service restrictions and partly due to exports, this was not the case. During these hours,
central PP generated 1,022 MW on average and had a minimum production of 560 MW [15]. During the
whole year, the minimum production from central PP was 446 MW in the western part. In the eastern part,
distributed generation was not able to meet the total demand at any hour; however, this is likely to change
with the upcoming erection of wind turbines planned until 2012. In the eastern system, the minimum produc‐
tion from central PP was 185 MW during 2007. In addition to domestic generation equipment, both the east‐
ern and western system has strong interconnections abroad, which are utilised for load balancing.
While the transition from a classic system with few producers to a system very much influenced by distributed
generation has occurred, the control system has changed from an old‐style technical‐operational system to a
market‐based system with producers and consumers placing bids on a market.