Environmental Engineering Reference
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remains - wind power is difficult to predict well in advance, and long-term bilateral
contracting for wind power will rely on a balancing mechanism or generators that
will enter into short-term bilateral arrangements a few hours in advance of real
time. The best option for wind power - the balancing mechanism or a bilateral
arrangement - will depend on the details of the market.
7.6
Benefits
The obvious benefit of wind energy is that it displaces fossil-fuel generation.
Ideally, this would be coal-fired generation, which produces 0.915 kg of CO
2
per
MWh. Unfortunately, coal is the most plentiful and cheapest fossil fuel, and tends
therefore to provide base load - see Figure 5.2. Wind generation is more likely to
displace mid-merit regulating plant, typically gas-fired CCGT. CCGT produces
less than half the CO
2
of coal, around 0.405 kg per MWh (Weedy
et al.
, 2012).
Proponents of coal-fired generation aim to solve the emissions problem with carbon
capture and storage. The cost of this technology is difficult to estimate, as no large-
scale demonstration has been constructed to date (2013). The cost is likely to be
substantial.
An alternative approach is to adopt a carbon tax that would reverse the posi-
tions of coal and gas in the merit order (Helm, 2012). Not only would this reduce
CO
2
in itself, it would also put wind and coal in direct competition, and enhance the
ability of wind energy to reduce emissions.
Wind energy provides a second significant benefit. When wind power is
plentiful, the most expensive online plant is displaced. The system marginal price
(SMP) decreases as a result. The major determinant of SMP is the underlying
demand. However, within a narrow range of demand the effect of wind power on
SMP may be seen. Figure 7.3 shows SMP for the Irish system (Eirgrid/ESB)
smp
Linear (smp)
70
60
50
40
30
20
10
0
0
200
400
600
800
1,000
1,200
1,400
1,600
Wind power (MW)
Figure 7.3
Variation of SMP with wind for a system load of 2,500 MW in 2012
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