As the UK increases its use of wind power, the power grid will come under growing pressure to balance the load, as E&T discovers.
Today, the UK is committed to European Union targets to deliver 35 per cent of electricity from renewables by 2020.
Starting from a base of around 5 per cent, this is an ambitious target with a good many ramifications. Perhaps the greatest of all is over how many gigawatts the UK's electricity grid can reasonably integrate, given most of the 35 per cent will have to be intermittent wind power.
So far, the debate has been fairly academic because the UK still only has 3.2GW of wind turbines working at around a 25 per cent load factor. Load-balancing a shortfall of up to 800MW - a near-negligible 2 per cent of average demand - when the UK can draw on a theoretical 75GW of power stations is no big deal.
That all changes massively if future projections are to be believed. According to a recent scenario by the National Grid, there will be 19.4GW of offshore wind and 12.9GW of onshore wind, delivering 98TWh in 2020.
Not everyone believes that such targets are achievable - far from it. But the debate on load-balancing wind has come a long way since 2003. The leading authority on intermittency and wind at the time was David Milborrow, and his views shaped prevailing opinion on the matter.
At the time, he had been funded to participate in studies by the European Commission, two by the DTI and one by the Cabinet Office, and had been studying the integration of wind energy into the electricity networks since 1988.
In a submission to the House of Lords Science and Technology Committee, he estimated that for the UK to reach the 10 per cent 2010 target, 12,000MW of wind would require around 700MW of extra reserve plant. However, it would also displace around 3,300MW of thermal plant.
The British Wind Energy Association's own briefing sheet 'Wind Power and Intermittency: The Facts' cites David Milborrow frequently, and he is now a technical consultant for the association. Its view is generally that "operating power systems is all about managing risks and what matters is the overall risk", which as they see it is pretty low because "there is, as far as we are aware, no evidence that demonstrates that windless days regularly coincide with peak demands on the UK electricity network".
Even the National Grid itself are pretty sanguine about load-balancing wind. This is odd, when some question whether they have the resources to connect the transmissions of up to 30GW of offshore and onshore wind generation by 2020.
Some people speculate whether with £16bn of net debt on their balance sheet, National Grid cannot afford to keep going to the debt markets and keep raising more capital at exorbitant 'credit crunch' prices and continue to make the investments everyone expects of it. It is all too possible that it will be forced to curtail its investment programme to repair the balance sheet and focus instead on making grid investments in America.
Load balancing sceptics
Perhaps the most sceptical towards load-balancing wind though are the Renewable Energy Foundation (REF) and the Energy Intensive Users Group (EIUG).
According to a report published in September 2008, 'UK Electricity System at Severe Risk 2010 to 2020', the plant balancing demands of large quantities of wind power would require two additional developments;
First, development of high-voltage interconnections with Norway, Germany, the Netherlands and France to permit trading of wind power surpluses and deficits, and to add power capacity. Second, deployment of widely distributed onshore electricity storage of all types.
The report also makes the salient point that National Grid and the Distribution Network Operators are legally prevented by the regulator from owning commercial storage, as this would constitute generation plant and competition for the existing electricity providers. Storage has to be the answer (see storage, right) but no one is yet building it and this regulation may have to be looked at again.
Jeremy Nicholson of the EIUG, meanwhile, pulls no punches on the load-balancing optimists, saying, "Wind energy is fundamentally insecure. It is delusional to the point of recklessness to assume it will ever meet 30 per cent of UK electricity consumption with an acceptable level of reliability. As events this winter have demonstrated, we are prone to periods of low wind speeds across the whole of the British Isles when the output from all our wind turbines combined is close to zero for days at a time, so nearly all of its generating capacity needs to be backed up by fossil fuelled power stations. The more wind we have on the system the greater the problem will be. For the wind lobby to fail to acknowledge this is intellectually dishonest."
When all is said and done, we have to be honest and admit that no one really knows precisely what the safe limit of gigawatts of wind power connected to our national grid is until we actually reach the moment of danger leading to blackouts. The best way ahead may be to create a notional limit - say 12GW, to be reviewed annually - and demand energy storage and/or additional inter-connections with Europe after that point for any additional wind turbines. But all that requires a new energy policy, a new investment framework and a realistic vision from our politicians which thus far, is not on the table.
That's why, regrettably, the UK seems destined to continue along this dangerously experimental path and just might be sleep-walking into a load-balancing crisis.
Dan Lewis is research director of the Economic Research Council [new window].