HC 517 The Economics of Wind Power

Memorandum submitted by W R B Bowie (WIND 59)

Wind power saves little or no CO2 and other Green House Gases

The fundamental argument in favour of wind power is that despite its very high cost, it produces less CO2 etc. than conventional power plants. This is, however, completely incorrect. Wind saves little or no CO2.

Wind is an intermittent source of power that cannot be ‘turned on’ when required like conventional sources of power. ERCOT of Texas says that they only consider wind power as reliable source of supply for about 8.7% of its name plate capacity. The E.On wind report of 2005 is more pessimistic saying studies show,

"Wind energy currently contributes to the secure production capacity of the system by providing 8% of its installed capacity" and also that this guaranteed supply will, "fall continuously to around 4%" as winds share of the generating capacity rises up to 2020. As an example at 17.30 on 7th Dec 2010 the UK wind fleet of 5200 MW produced just 300 MW; a load factor of 5.8%. At the same time both Germany and Denmark had lower load factors; 3% % 4%

When plotted in a graph the rises and falls of wind’s capacity looks like a comb! Rapid shifts in power are quite unsuited to the user’s requirements. Because of the erratic nature of wind power, almost without exception, the wind power providers E.On, Centrica, Scottish Power etc say that it is essential that wind has ‘back-up’ from conventional sources of power that can rapidly be turned on & off, to match fluctuations in the wind . Whilst they are agreed ‘back-up is needed, there is some latitude in the estimates of the minimum ‘back-up’ needed. Dr Paul Golby CEO of E.On UK, says 90% whilst Mr Rupert Steele of Scottish Power says, "Thirty Gigawatts of wind maybe requires twenty-five GW of backup"

As a consequence of the need for power to match demand, ‘back-up’ plants are run start/stop to match the wind’s fluctuations. We might like use hydro, but UK has insufficient hydro resources, so the ‘back-up’ is probably a fossil fuel plant; usually gas. An open cycle gas turbine [OCGT] is effectively a jet engine, and a combined cycle gas turbine [CCGT] is this jet engine in which the heat from the combustion is collected and used to make steam to drive a secondary generator. The CCGT produces about 0.4 of a ton of CO2 per MWh. This is 50% more efficient than the OCGT that may produce same amount of power but uses more fuel and this results in about 0.6 ton of CO2 per MWh. When CCGT machines are used to ‘back-up’ wind power the gas plants are switched on & off [to match the wind] often do not reach a sufficient temperature to make steam and thus operate as if they were OCGT plants. Knowing this some powers suppliers just use OCGT as ‘back-up’ to wind.

Since the wind turbines only operate at about 25% of their rated or name-plate capacity* the ‘back-up’ has to supply the remainder, of 75%. Since, as shown above, a gas turbine operating stop/start produces approx. 0.6T/MWh the average is [75% x .6=] 0.45ton per MWh. This is more CO2 [and SO2, Nox etc] than would have been produced by an efficient CCGT working full time; 0.4ton per MWh. On the attached sheet I have shown this together with the costs of generating electricity by wind power. My sheet paraphrases the situation but detailed studies showing little or no saving in CO2 etc as a result of wind power have been produced by Prof G Hughes of Edinburgh University ["Why is wind power so expensive?"]. A Dutch study by Udo, de Groot and le Pair comes to similar conclusions as does the BENTEK report for Colorado and Texas,

My sheet also shows the cost of wind power vis à vis a CCGT plant. The result is that the cost of wind power is at least double the cost of power from CCGT. Other UK studies, such as those by the RAE or Mott MacDonald have similar results, as do studies from the USA. Other conventional types of electrical generation e.g. coal &nuclear result in similar costs per MWh to cost from gas. A very thorough Paper produced by Mr Colin Gibson formerly Power Network Director with the National Grid in Oct last year shows an even larger discrepancy between the cost of power form conventional sources and wind [ x3 onshore & x4 offshore]. See IESIS Glasgow.G2 9DS.

Since wind power does nothing to reduce CO2 and GHG emissions and costs at least twice as much as other sources of power, what on earth are we using it for? Why damage industrial competitiveness and put millions into fuel poverty for no benefit to climate?

William R B Bowie

C.Eng, BSc, MICE, FCIHT. The Old Iron Mill, Ironmills Road, Dalkeith EH22 1JP

If my experience working on several power stations is of interest I should be happy to testify.

June 2012

* See Report for John Muir Trust covering period Nov 2008 to Dec 2010 where capacity was 24.08%

		CCGT		Wind		Wind
				Offshore		Onshore
				e.g. London Array		e.g. Clyde
Capital Cost per MW		£600,000		£3,000,000		£1,400,000
Additional cabling/MW say		£0		£200,000		£100,000
		£600,000		£3,200,000		£1,500,000
Load Factor / Capacity		80%		30%		27%
Life Expectancy years		25		18		20
Lifetime Power Produced MWh	8760	175,200		47,304		47,304
Plant Cost per kWh in pence		0.34		6.76		3.17
OH and Maintenance say		0.34		2.00		1.00
Gas at 2.1p/kWh at 60% Efficiency [EEP]	2.1	3.50		0.00		0.00
Back-up cost ¾ of CCGT cost	0.75	0.00		3.14		3.14
Cost in pence per kWh		4.18		11.90		7.31
Carbon Tax if applicable		0.36		0.27		0.27
Cost per kWh in pence		4.54		12.17		7.58
Renewable Options Certificate till 2014	say			-8.40		-4.20
Wind Cost less ROC's				3.77		3.38
Comparitive Costs Wind to Gas		1.00		2.68		1.67
Wind mix offshore share	75%				2.43
CO2 from CCGT plant ton/MWh	0.40	0.40
CO2 OCGT plant run as back-up ton/MWh	0.60	0.00		0.45		0.45
CO2 from Peat medium scenario 17,127 ton [REF]	25%	0.00		0.00		0.09
CO2 from sea grass		0.00		?		0.00
Total emissions		0.40		0.45		0.54
Scotland's CO2 Emissions t/MWh in 2002	0.3573	>		>>		>>>
Cost per kWh in pence with gas price X	4.5	16.8		21.36		16.8
N.B. 1 Scotland and the UK's emissions/MWh are low because of the share of nuclear power
If nuclear is repaced by wind [with its 'back-up'] more not less GHG's will be produced
N.B.2 Wind is intermittent and wind-power fluctuates; as often as 100 times/day.
Under such conditions a CCGT back-up plant does not get hot enough to make steam.
Thus the CCGT plant runs less efficiently as a Open Cycle Gas Turbine.[OCCT]
This means about 50% more fuel per MWh and thus 50% more CO2 per MWh.
N.B.3 Back-up from conventional power plants is essential to accommodate for wind
fluctuations and thus provide a steady reliable source of electricity. UK wind can
vary 100 MW in five minutes
N.B. 4 As the UK does not have the potential for much additional hydro [1 or 2 MW]
the 'back-up' is likely to be fossil fuel; say gas fired, plants. Since the average
output of UK wind turbines was just 24.08% of the name-plate capacity [*JMT]
75.92% must be supplied by the 'back-up' so if the gas price goes up the cost
of the 'back-up' will also increase. The gross cost of wind will vary with the
price of gas! Gas would have to increase > 4 fold before the cost of on-shore
wind is comparable with power from a CCGT plant. {& >9 fold for off-shore]
[*JMT] = Report for John Muir Trust covering period Nov 2008 to Dec 2010