Bishop Hill RenewableUK get desperate
Aug 17, 2012 Energy: wind GWPF Greens Gordon Hughes' GWPF report on the costs of wind power contains the following claim:
Meeting the UK Government’s target for renewable generation in 2020 will require total wind capacity of 36 GW backed up by 13 GW of open cycle gas plants plus large complementary investments in transmission capacity – the Wind Scenario. The same electricity demand could be met from 21.5 GW of combined cycle gas plants with a capital cost of £13 billion – the Gas Scenario. Allowing for the shorter life of wind turbines, the comparative investment outlays would be about £120 billion for the Wind Scenario and a mere £13 for the Gas Scenario.
This seems clear to me. The capital cost - see the words there in the middle? -of wind energy is much higher than that of gas.
Now look at how BusinessGreen reports Hughes' work (the article is written by Maria McCaffery, the chief executive of RenewableUK (formerly the British Wind Energy Association):
Among the more absurd assertions put forward in this paper is the contention that wind energy is 10 times more expensive than gas, but his comparison is flawed. He fails to include the cost of gas itself and only includes the cost of building a gas-fired power station and the infrastructure to go with it. As most right minded people know, a gas-fired power station without any gas does not generate any electricity. Perhaps his calculations exclude the cost of gas because the costs of this fossil fuel are so difficult to predict and very volatile. The comparison is certainly not like-for-like and is very misleading.
I think we have established something about the integrity of Renewables UK.
Reader Comments (59)
@LC
http://en.wikipedia.org/wiki/CCGTThere are two kinds of gas plants, with very different efficiencies for converting the chemical energy of the fuel into electrical energy. Open-cycle gas turbines are basically a jet engine strapped down and connected to a generator -- cheap and rapidly throttled, but the hot exhaust means you're throwing away a lot of energy. Combined-cycle turbines have a gas turbine as the first stage, then run that exhaust through a boiler to feed a steam turbine -- more power from the same amount of gas, but more cost and slower to change power level. The 35% and 60% figures are in the ballpark.
I don't know where the 2p per kW-h figure comes from. Cost of the gas itself, pre-conversion into electricity?
Bill,
I understand the efficiency ratings for the different methods of production for electrical generation, but, as I understand it, the 2p figure represents the actual cost, on average, of producing a Kwh of electricity using gas. That being the case, the efficiency has already been factored in. The 2p figure came from BitBucket, so I don’t know where he got it from, but, if memory serves me well, it isn’t actually that far out. I looked into it about a year ago and I’m pretty sure the price then was around 1.7p per Kwh. So 2p now is probably close enough. Of course that figure might rise slightly in a scenario where gas generating has to kick in quickly to cover a sudden drop in wind.
@Bill, @Bit bucket.
In my rush to get my 2penneth in I did confuse KW and KW hrs. My appologies.
The 2p/KWhr is the current wholesale price of gas. (Sorry I lost the link)
A modern CCGT generator can acheive 60% efficiency. http://en.wikipedia.org/wiki/Baglan_Bay_power_station
I used 35% for OCGT. This is probably lower in practice if it is ramping up and down frequently.
For simplicity lets look at the cost of 1hr worth. BItBucket you are right, the need is for 21.5GW.
Senario 1. Only use CCGT. 60% efficient. Cost of 1KWhr = 2/0.6p = 3.33p
21.5GWhr = 7.17E5 = £717000
Senario 2. Back up for wind. 35% efficient 75% of 21.5GWhr. Cost 1KWhr = 0.75*2*21.5 = 4.29p
21.5GWhr = 9.21E5 = £921000
Wind with gas backup uses nearly 30% more gas than an efficient gas plant!!!!!!!!!!
It's late and my head is spinning. Someone help me out here . Can it really be that bad- windmills make us use 30% more gas???
Wind with gas backup uses nearly 30% more gas than an efficient gas plant!!!!!!!!!!
It's late and my head is spinning. Someone help me out here . Can it really be that bad- windmills make us use 30% more gas???
Aug 18, 2012 at 12:03 AM | auralay>>>>
Allowing for the known the inefficiencies of wind turbines I'm surprised that you're surprised by that!
Ok. As I seem not to have kept all the info I collected the last time I looked into this, I’ve spent a couple of hours googling and come up with the following:
The UK wholesale gas spot price on 17/08/12 was just short of 55p per therm. This gives a gas KWh price of 1.87p (so auralay’s price of 2p per gas KWh is essentially correct). Bear in mind that this is the spot price and that power suppliers most likely buy their gas at a better price in advance.
To produce a Kwh of electricity in a CCGT system, it takes, on average, just slightly over 2 KWh of gas (a therm of gas will generally produce around 14 KWh of electricity). So, on current UK spot prices, it will cost just short of 4p in gas to produce 1 KWh of electricity. So the price I quoted in my earlier comment of 1.7p for last year must be wrong. I think I must have got mixed up with the price of a gas KWh. Having said that though, the current UK wholesale price for electricity is just under 4.3p per KWh, which doesn’t appear to leave much room for profit. So maybe I’ve still got something wrong here.
Assuming for the moment that I’m correct though, this means that in our 21.5GW scenario, the all CCGT option would have an annual gas cost of slightly above £7.5billion at today’s prices.
The Wind plus CCGT backup option, based on the wind only providing an average of 25% capacity, would have an annual gas cost of £5.6billion. Added to that would be the gas cost for spinning reserve (I cant find a definitive figure for that, but it appears to be in the region of 30% of full power consumption) for when the wind actually blows and the gas cost for the times of ramping up when it doesn‘t, where, for a while at least, the CCGT acts more like OCGT with it’s associated drop in efficiency. For the sake of argument, I’ll be really, really conservative, err well on the side of underestimation and assume a figure of 15% of full power consumption for the total of those times. This adds a further almost £300million to the annual cost giving a total gas cost of around £5.9billion per annum.
If we then assume that the windmills will last twenty years (I know, I know, but let’s be generous), that amounts to £118billion at today’s prices. Add in the £120billion start-up costs and you get a grand total of £238billion.
For the CCGT option, the total gas cost at today’s prices will be £150billion. Add in the start-up costs of £13billion and you get a grand total of £163billion. A difference between the two options of £75billion.
If the recent Dutch report on wind power linked to by Albert Stienstra on another thread the other day: http://www.clepair.net/statlineanalyse201208.html is accurate, then the lifetime of the windmills is more likely to be 12 years rather than 20. On top of that, the same report shows that, when you take manufacturing and construction emissions into account, they save virtually no CO2 either. If the windmills only last 12 years then the Wind option cost becomes £191billion and the CCGT option cost becomes £103billion. A difference of £88billion.
I could well be wrong on all the above, so if any of the engineers here can come up with better figures, I’ll be only too happy to accept them :)
£107 billion (120 - 13) buys a lot of gas.
An all-CCGT or all-OCGT scenario probably isn't very realistic and represents the worst-case spread between running a closed cycle gas turbine at maximum efficiency compared to running an open cycle gas turbine at minimal efficiency. The numbers I calculated were simple extrapolation based on certain assumptions.
Disregarding the capital costs of either the all gas or all wind scenario, the all gas is going to require much less fuel to achieve the same base load than the all wind scenario hence will cost less to operate the gas turbine portion of the power generation.
The hitch lies in the closed versus open cycles and the relative efficiencies of each system. When looking at a back of the envelope calculation like I did, the critical assumptions are: 1) CCGT efficiency (quoted as 60% up thread), 2) OCGT efficiency (quoted as 35%), and 3) the percent of power that needs to be supplied by the backup gas turbine (75%).
The 60% number for CCGT efficiency means that only 60% of the energy released by burning natural gas is captured as electrical power. So for any given base load, we need to combust additional fuel to make up for the lost energy. The energy needed is the baseload energy divided by the efficiency.
E_CCGT = Base / Eff_CCGT
For the wind scenario, the open cycle generation will be needed whenever wind isn't delivering. The Duty_OCGT is said to be around 75%. So the fuel energy needed to feed the base load via OCGT is
E_OCGT = (Base * Duty_OCGT) / Eff_OCGT
Looking at the ratio of fuel energy needed for wind vs gas, divide E_OCGT by E_CCGT, which yields:
E_OCGT / E_CCGT = Duty_OCGT * Eff_CCGT / Eff_OCGT
Using the numbers upthread,
Duty_OCGT = 75%
Eff_CCGT = 60%
Eff_OCGT = 35%
results in a ratio of 1.29
Tweak all of these numbers 5% in favor of wind and you still burn more fuel using windmills...
Duty_OCGT = 80%
Eff_CCGT = 55%
Eff_OCGT = 40%
E_OCGT / E_CCGT = 1.1
Note that I wrote energy, but the analysis is the same for power as we're looking at the ratio
@Earle.
I agree with your first conclusion- you have come up with the same calculation I did but much more elegantly. Thank you.
When you "Tweak all of these numbers 5% in favor of wind ..." you changed windmills from 25% duty to 20%. To be "5% in favour"of wind this should be 30%.
Last calculation then is Duty_OCGT = 70% which calculates to E_OCGT / E_CCGT = 0.96.
I mention this to forstall unkind comments- I don't think (and I suspect you don't either) that the tweaked figures are remotely realistic.
Never forget what Steve Holliday the CEO of the National Grid has said
"The Era of constant electricity at home is ending,
The days of permanently available electricity may be coming to an end, the head of the power network said yesterday.
Families would have to get used to only using power when it was available, rather than constantly, said Steve Holliday, chief executive of National Grid. Mr Holliday was challenged over how the country would "keep the lights on" when it relied more on wind turbines as supplies of gas dwindled. Electricity provided by wind farms will increase six 'fold by 2020 but critics complain they only generate on windy days."
Mr. Holliday told Radio 4's Today programme that people would have to change behavior. "The Grid is going to be a very different system in 2020,2030” he said. "We keep thinking that we want it to be and provide power when we need it. It is going to be much smarter than that.
"We are going to change our own behavior and consume it when it is available cheaply."
Watch the bad news here.
http://raeng.tv/default.aspx?item=47
Here he admits that the service of constant power from the National Grid for households and industry will not be able to continue because of the use of renewable energy especially wind power.
And he seems to think that this vast retrograde step for homes and industry is in some way beneficial. He must have been sold totally on the CAGW message. Very sad for an engineer at the top of his profession.
Is no one listening ????