The limits to renewable energy
Written by Hugh Sharman   
Sunday, 18 December 2011

Martin Livermore of the Scientific Alliance writes....

This week, the Scientific Alliance was very pleased to publish a report on renewable energy, jointly with the Adam Smith Institute. Entitled Renewable Energy – Vision or Mirage?, this sets out to review available renewable energy technologies and analyse what contribution they could realistically make to a secure and affordable future energy supply. It focuses on the UK, but the essential messages are relevant anywhere.

Our main conclusion is that wind power (which is the only technology which could be deployed on a large enough scale to have a chance of meeting the UK government’s ambitious targets) cannot fulfil the expectations which policymakers have for it.renewables_report_cover.1.png

The primary objective of the present UK and EU energy policy is to reduce fossil fuel use, and hence also carbon dioxide emissions. This is in an attempt to fulfil the EU 20-20-15 targets: a 20% reduction in carbon dioxide emissions and 15% of energy from renewables by 2020. Because, in practice, most of the renewables would be used to generate electricity rather than be used for transport or heating – which together represent about two thirds of our fossil fuel use – the target actually requires a very large switch away from coal and gas in this sector. The challenge is immense.

In principle, the use of ‘free’ wind energy is a good idea, but in practice it can deliver less than we might think. The primary problem with wind, as with other renewable energy sources, is that it is intermittent. Although windy and calm days can be forecast reasonably reliably, the wind rarely blows steadily. Since wind turbine output follows a cube law, a doubling of wind speed leads to an eight-fold increase in electricity output (and vice versa). Even when these variations are smoothed out across large arrays of turbines and wind farms spread across wide areas, the power delivered to the grid varies considerably over short timescales.

To an extent, the electricity grid can cope with that, although the problem gets more difficult as penetration of renewables increases. However, there are periods when the wind hardly blows, and each year we experience some of these at times of high demand, particularly in winter evenings. The worst situation is to have a stable area of high pressure over the country. In winter, this leads to calm, very cold conditions, while in summer it is equally calm, but very hot. In the UK, peak demand comes in winter but, in countries further south, there will also be increased demand for air-conditioning during summer heat waves. In both cases, power would have to come from sources other than wind.

The opposite problem can also occur. If the wind is blowing too strongly (above about 50mph), turbines must be shut down to avoid damage. This is exactly what happened last week in Scotland and northern England. According to a Sunday Times report (Storm shutdown is blow to future of wind turbines), wind farm output on Thursday 8 December fell from 2GW to 708MW between 9am and noon.

Unless consumers are prepared to tolerate an intermittent supply of electricity, fossil fuel generating plant – largely relatively inefficient open-cycle gas turbines – has to be left idling in order to ramp up its output quickly and balance the grid. The result is that wind farms save less fossil fuel overall than their output would suggest. Experience from Ireland, which already has a higher proportion of wind energy capacity than the UK, shows that installing new capacity produces diminishing returns in terms of fuel savings; beyond a certain point, erecting more wind turbines saves no more gas or coal and merely adds cost and insecurity to the system.
But despite the additional costs and inefficiencies which wind energy brings, there are moves afoot to install still more. The European commission has published its ‘energy roadmap 2050’ (EU commissioner calls for negotiation of new renewable energy targets). According to the report, “It says a high renewables energy mix - with as much as 97 per cent of the EU's electricity consumption met by renewable energy, including 49 per cent wind power in 2050 - would have the same ‘overall energy system costs’ as any other decarbonisation or business as usual scenario.” Our report suggests that a high degree of wishful thinking lies behind this.
Also, the think tank Reform Scotland has issued a report (Powering Scotland) which endorses the Scottish executives ambition to generate the equivalent of all its electricity needs from renewable resources and even suggests that there could be an income stream of £2bn a year from exporting renewable electricity. The experience of Denmark suggests this is quite unrealistic: the country generates 20% of its electricity from wind farms, but half of that is exported to neighbouring countries at low spot prices because it is produced at the wrong time.

Our aim has been to open up the debate on this contentious issue. Rather than sleepwalk into a future energy system which is expensive, unreliable and saves little in the way of emissions, it is time to look at the evidence of what actually works. As technologies develop, the situation will undoubtedly change, but for now a reliable, affordable, low-carbon electricity grid has to rely much more on a mix of efficient nuclear and combined cycle gas turbine generation.

This is the last Scientific Alliance newsletter of 2011. I wish all readers a peaceful and happy Christmas and healthy and prosperous New Year. The next newsletter will come out in early January.

 

You need to login to comment on this article.