Wednesday, September 26, 2012

Economics of Gas vs Wind Power

It is often argued that wind power has one main failing, namely that it isn't available all of the time.

Because of this, it is argued, all wind power has to have backup capacity sitting in the background.

Now, there is a good deal of truth to this. Wind power spread over a geographical areas the size of the UK is significantly correlated and either backup generation or access to the European electricity grid is required to cope with this variability.

Against this we need to set the reality that their are many GW of medium scale diesel generating units used by utilities right across the country. In the UK only a portion of these can be called upon to be used by the grid, in France--with it's greater portion of inflexible nuclear generation--these units are required to be grid connected.

More to the point, we still have many GW of coal power generation in use. Even as we speak 19GW of coal power is in use.  These unit's must surely but put out of regular use but retained for the highest energy demand cold periods. If they are used for 2 weeks per year the carbon input would be negligible but the security of supply provided would be valuable.

Finally, i find it fascinating just how cheap gas power stations are. Recently 2GW of generating capacity was built for only £1Bn. If the numbers in this recent news story are correct wind power projects cost about £6000 per peak kW installed compared to £500 per peak kW  in the aforementioned gas power plant. In reality the situation is even worse as on an average annual basis wind power only provides around 40% of its maximum power.

Usually this is taken to mean that wind power is uneconomic and gas is cheap. In fact what is actually show by these numbers is that the economics are decided by capital costs and running costs, respectively. Onshore wind is likely to be cheaper than gas in overall terms in just a few years.

A comparison with energy efficient LED's is illuminating (no pun intended). LED's cost perhaps £6 each compared to regular halogen light bulbs which might cost £50 each. However, if you use the LED's 9hrs a day throughout the year--such as in a restaurant or shop--the energy savings will more than repay your capital expenditure. After that year you will be reaping a dividend of long term energy savings. Now, the same type of economics are at play with with and gas.


Finally, the costs of buying a light bulb and an LED is pretty much the same as just buying the LED: £6 vs £6.50. The same is true for building wind or wind and gas plants. The advantages of using wind are to be had when the wind is blowing (over 80% of the time at the average site) and when wind isn't blowing the gas technology can be plugged back in. The increased capital cost for backup gas is negligible.

Further Reading:

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Wednesday, September 19, 2012

New 2GW Gas Power Plant in Pembrokeshire

RWE Npower has just opened a new 2000MW CCGT Power Station in Pembrokshire (UK). I mentioned in a recent post that there is an ongoing consultation on a draft energy bill, their is also a great deal of controversy about the role that this bill will grant to gas power. This controversy is driven in significant part by the government's statutory climate change advisers the Committee on Climate Change who have highlighted the conflict between unabated gas and legally binding climate targets.

I was curious to find out the gC02/KWh figure for this new station as i was able to find plenty of claims about it's efficiency but no numbers! The tale just got curiouser and curiouser as i looked at their environmental impact assesment which states in section 5.3.5 that  the power station:

 "if operated at full capacity throughout the year, would emit approximately 5.8 million tones of co2".  
 Their are 8760 hours per year and the power plant produces 2000MW so at full capacity the power station would produce 17520GWh of electricity whilst emitting 5.8 million tones of co2. This works out at 302g/KWh.  This seems very good. However, in an Imperial College ICEPT Discussion Paper by Dr Robert Gross the following is to be found on p9:
"Currently the best achievable performance in a new CCGT would be around 56% efficient, implying around 360g/KWh, neglecting losses. Emissions as low as 300 g/KWh would require efficiency of 66%, well beyond what many believe to be the limits of current designs"
Some doubt is therefore cast upon this figure. The EIA doesn't provide a figure for the co2/kwh that this power plant is capable of. It does invite you to work this out yourself but if you do this and you interpret "operate at full capacity" to mean 24/7 operation you are apparently mislead. Some downtime may be assumed for maintenance but this is not stated.

Furthermore, the actual emissions per KWh will depend on the operating regime about which we are told nothing.

It is also notable that the gas used in LNG, imported at -140 degrees celsius and warmed up by aplication of sifnificant quantities of energy. This is dissapointing as some of this energy could have been used for district heating.

As a final thought, i find it interesting that the proposed Energy Performance Standard currently being considered is 450gC02/KWh. Considering the best technology might enable 300g/KWh: this is quite a gap.


Related Reading:

  1. New gas power station accounced by Energy Minister Stephen Crabb.
  2. Official power station website.
  3. Environmental Impact Assesment (EIA) by Marine Management Systems.
  4. ICEPT Discussion Paper on Gas and costs of wind power.

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Thursday, September 06, 2012

Reshuffle paves the way for Aviation expansion.

UK Climate Policy is in a unique situation in that the overall aim: emissions reductions of 80% by 2050 is already written into law. During times of economic difficulty when Growth is THE issue it is significant that policy out of political fasihion is given some support by a legally binding emissions reduction law.

Exactly how much the support UK Climate Change Act provides environmentalists with is about to be tested. Cabinet has just be reshuffled and Justine Greening the Transport Secretary with an anti-heathrow expansion position is on here way out while and old coal miner from the north of england is on his way in.


There is a lot of history in the battle over aviation and climate change (past blog coverage here). And it looks likely that this fight is back on. I wonder how much of this battle is going to be over planning concerns and how much is going to come down to the inherent incompatibility between airport expansion and the govornments legally binding emissions targets.

  1. Can The UK Fly More Without Breaking Climate Change Targets? (Guardian 6th Sep 2012)
  2. Boris Johnson's Heathrow warning after Justine Greening's move (BBC, 4th Sep 2012)



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