Environmental Engineering Reference
In-Depth Information
Figure 3.17
CEGB simulation study of large penetration. (From Grubb, M.J.,
IEE Proceedings C
, V.
138
(2), March 1991, reproduced with permission of IET)
penetrations [9, 10]. To illustrate the challenges, an extreme example from one such study is
reproduced here. Figure 3.17 shows the output that would have been expected from 25 GW
of dispersed wind capacity (middle graph) and 10 GW of tidal (lower graph) alongside the
demand over a period of one month. In this example 30 and 13% of the consumer energy
would be supplied from wind and tidal respectively. The wind power varies less rapidly than
demand, tidal more rapidly. Figure 3.18 shows the effect of subtracting the output from wind
and tidal power from the demand, leaving a residual load (dashed curve) to be met by a con-
ventional thermal plant.
More recently [18, 19], studies have considered the possibility of meeting the entire
demand from a mix of renewables. Figure 3.19 taken from Streater's work [18] shows hour
by hour variations in the time variable renewables. Penetration levels of such a high magni-
tude result in periods when the available power from the RE sources exceeds demand. Even
before this stage is reached, for reasons of system reliability, the RE sources would have to
be curtailed. Table 3.2 shows the capacities of the different renewables installed and their
penetration, defi ned as the output divided by the total load (i.e. ignoring any curtailment.) It
is also apparent that for the year in question a defi cit occurs between weeks 15 to 18 and
weeks 44 to 52. In principal the shortfall could be made up from biomass based
generation.
Denmark and less so, Germany generate a high percentage of their total electricity needs
from wind power and are planning further capacity. A recent study from Elkraft, a Danish
system operator, asserts that a wind penetration up to 50% is technically and economically
feasible. This is based on an increase of installed capacity of 3.1 GW in 2005 to 5 GW in
2025 and a substantial expansion of the Danish grid. The study claims that even with this
