The potential of renewables

In general, renewables are quicker to build than nuclear plants, they are cheaper, they provide greater security, and they have none of the headaches of nuclear power.

There is no question that renewables can meet world demands for energy (not just electricity), and anticipated future demands (see below). Here is some of the evidence:

  • A network of land-based 2.5-megawatt (MW) turbines restricted to nonforested, ice-free, nonurban areas operating at as little as 20% of their rated capacity could supply more than 40 times current worldwide consumption of electricity and more than 5 times total global use of energy in all forms. There is additional potential in offshore wind farms. See Global potential for wind-generated electricity (PDF, 1.9 MB, Xi Lua, Michael B. McElroya, and Juha Kiviluomac, Proceedings of the National Academy of Sciences of the United States of America, June 22, 2009, doi: 10.1073/pnas.0904101106). 
These articles review research showing that there are more than enough renewable sources of power to meet all of the world’s energy needs, not just electricity. In the scenario described in the Scientific American article, wind supplies 51 percent of the demand worldwide, provided by 3.8 million large wind turbines (each rated at five megawatts). Although that quantity may sound enormous, it is interesting to note that the world manufactures 73 million cars and light trucks every year. An interesting conclusion of this research is that, because there would be much less wastage of energy in a renewables scenario, total world demand for power in 2030 would be 11.5 terawatts, using renewables, compared with 16.9 terawatts if we were to stick with conventional sources of energy. See also the interactive presentation about this research: Powering a green planet: sustainable energy, made interactive (Scientific American, November 2009) and Review of solutions to global warming, air pollution, and energy security with Supplementary information.
  • Using the proven technology of concentrating solar power (CSP), less than 1% of the world's deserts could produce as much electricity as the world is using. Less than 5% of the world's deserts could produce electricity equivalent to the world's total energy demand. Using low-loss HVDC transmission lines, it is feasible and economic to transmit electricity for 3000 km or more. It has been calculated that 90% of the world's population lives within 2700 km of a desert (see The Desertec Foundation and Desertec-UK). These calculations, which are quite conservative, are based on research from the German Aerospace Centre (DLR). Although it would be possible to obtain all the world's energy from deserts, there are several reasons why Europe and the UK (and other regions and countries) should use a variety of renewable sources of power, as described in the TRANS-CSP report from the DLR (which may be downloaded via links from http://www.trec-uk.org.uk/reports.htm ).

  • Photovoltaics (PV) could generate about 266 TWh/yr in the UK - about 66% of the UK's present electricity demand. See Renewable energy and combined heat and power resources in the UK (PDF, 600KB, Tyndall Centre, 2002). PV is quick and simple to install. However, that estimate is certainly an under-estimate because it focuses on PV on buildings and excludes the very considerable potential of ground-based installations on brownfield sites and PV in association with roads and railways.

  • The government's own plans for the growth in renewables and energy conservation can ensure adequate generating capacity in the UK until at least the mid 2020s. See Implications of the UK meeting its 2020 renewable energy target (PDF, 734 KB, Pöyry Energy (Oxford) Ltd for WWF-UK and Greenpeace-UK, August 2008).

Negawatts

It is often cheaper to save power than to generate it. In that connection, it has been estimated that 73% of global energy use could be saved by practically achievable design changes to 'passive systems' (eg ensuring that buildings are well insulated). This reduction could be increased by further efficiency improvements in 'conversion devices' (engines, generators etc). See Reducing energy demand: what are the practical limits? (report by Jonathan M. Cullen, Julian M. Allwood, and Edward H. Borgstein of the Department of Engineering, University of Cambridge, 2011-01-12); see also Study: EU energy demand can be cut by two thirds (BMU, 2012-11-19).

Security of energy supplies

The variability of sources such as wind power is much less of an issue than is sometimes suggested, as described in Managing Variability (PDF, 402 KB, a report by independent consultant David Milborrow commissioned by Greenpeace, WWF, RSPB, Friends of the Earth, July 2009)Electricity transmission networks in the UK are already designed to cope with variability arising from the failure of power stations and from variations in consumer demand, and that, for a small additional cost, wind power could provide up to 40% of the UK's electricity. Further increases in the level of wind penetration are feasible and do not rely on the introduction of new technology.

Contrary to what is often suggested, all sources of electricity are intermittent because all kinds of generators can and do fail:

  • When a nuclear power station fails, it is particularly disruptive because it removes a relatively large amount of capacity from the grid and it normally does so quite suddenly and often without much warning. By contrast variations in wind power are much more gradual and there is normally several hours warning. The disruptive effect when a nuclear power station fails is described in Exclusive: Will wind farms pick up the tab for new nuclear? (Business Green, 2010-08-24) and in Renewable energy providers to help bear cost of new UK nuclear reactors (The Guardian, 2013-03-27).  The expected increase in the number of nuclear power stations in the UK will mean that the annual cost of providing so-called Large Loss Response will rise from £160m a year to £319m. But the costs will be shared equally across all electricity providers. Naturally, the renewable generators are not pleased about this.
  • A significant part of the rise in the UK's emissions in 2010 has been due to the unreliability of nuclear power stations. "The biggest reactor in the country, Sizewell B, was offline for six months, meaning more coal and gas had to be burned to fill the electricity gap, pumping more climate-warming gases into the air. Other reactors had problems too in 2010 and more recently events as varied as a rogue school of jellyfish and winter tornadoes have closed atomic energy plants." (from Leaping UK carbon emissions deliver two red-hot lessons (The Guardian, 2012-02-07).

Keeping generating plants on ‘spinning reserve’ in case other generating plants fail is a wasteful ‘last century’ practice. Now, there is a range of techniques for matching supplies of electricity to variable demands. These include:

  • Large-scale 'HVDC' transmission grids, smoothing out variations in supply and demand across a wide area.

  • Renewable sources of electricity that can provide 'power on demand': enhanced geothermal systems (EGS), hydropower, thermal power stations fired with biofuels, tidal lagoons with pumped storage, and concentrating solar power with heat storage and backup sources of heat.

  • Vehicle-to-grid technologies, providing storage from electric and hybrid vehicles.

  • Storage of power via pumped storage, compressed air, hydrogen and more.

  • A variety of methods for managing demand.

  • Provision of spare capacity, such as gas power stations, fired with biogas.

  • Methods for predicting variations in supply and demand.

It is sometimes said that nuclear power is needed to provide ‘base load’ because wind and solar power are variable. But the inflexibility of nuclear power makes it an embarrassment on the grid:

  • In matching supplies of electricity to variable demands, power engineers do not need 'base load', they need 'power on demand' -- the ability to respond flexibly to peaks and troughs in demand. Nuclear power lacks that flexibility. Much more useful are renewables that can provide that kind of flexibility (see above).

  • As mentioned above, nuclear power stations can and do fail and special provision is needed to safeguard against the effects of those failures.

A demonstration of the way that renewables can provide a reliable and responsive source of electrical power is the “Combined Power Plant” which links and controls 36 wind, solar, biomass and hydropower installations spread throughout Germany. It has proved to be just as reliable and powerful as a conventional large-scale power station.

Research at the University of Delaware has shown that a mix of offshore and onshore wind, along with contributions from solar power, could provide reliable and cost-effective power flow during all but a handful of days in a hypothetical four-year period under study.

There are now many reports showing how renewables can be provide robust, reliable, and responsive supplies of electricity, without nuclear power. Details, with download links are on www.mng.org.uk/gh/scenarios.htm.

Providing a backstop against contingencies

It is sometimes said that a problem could arise if there was a flat calm over the UK during the winter when the demand for electricity is high. There are three main answers to this:

  • If the UK were to rely exclusively on wind power, this might be true. But there is a range of other renewables that will keep working regardless of whether the wind is blowing or not.
  • There is a wide range of techniques for matching supplies of electricity with constantly-varying demands for electricity (above) and these should keep the lights on even in extreme scenarios.
  • If the Government wishes to guard against the most extreme conditions, it can maintain a strategic reserve of gas-fired plants which are still serviceable but near the ends of their working lives, together with a strategic reserve of fuel to power them. These would provide much more flexibility than nuclear plants with a much lower capital cost. Since they would only be used occasionally, their running costs would be low. The fuel for those gas-fired plants could be ordinary 'fossil' gas but greener alternatives would be biogas, biomethane, or hydrogen generated by the electrolysis of water, using spare capacity at times when there is an excess of wind power or other renewable sources of power.

Terrorism and proliferation of nuclear weapons

Nuclear power scores badly in two other aspects of security: terrorism and the proliferation of nuclear weapons. Nuclear plants and trains and ships carrying nuclear fuel or nuclear waste are vulnerable to attack by terrorists. And because of the "Janus-like character of nuclear energy" (Kofi Annan), nuclear power facilitates the proliferation of nuclear weapons.

Contrary to what has sometimes been suggested, nuclear power is not a "home grown" source of power in the UK -- because all uranium fuel is imported.

Links

Cost

It is widely assumed that decarbonising the world's economies will be much more expensive than business-as-usual. But there is growing body of evidence to the contrary:

There is now overwhelming evidence from a variety of sources that nuclear power is one of the most expensive ways of generating electricity. Without the subsidies that it enjoys, nuclear power would be entirely uncompetitive.

Speed

In general, renewable sources of power are quicker to build than nuclear power stations. For example, Germany installed 3.8 GW of PV solar panels in 2009 and 8.8 GW in 2010. Allowing for differences in capacity factors, the PV installed in 2009 would produce about 50% of the output of a 1 GW nuclear power station and the PV installed in 2010 would produce more electricity than such a power station. By contrast, any one nuclear power station normally take at least 7 years to build.

In the last few years up to 2010, wind power around the world has been growing at about 25% per year. If that compound rate of growth were to be maintained, then given that the present installed capacity is 159 GW and allowing for a capacity factor of about 33%, it would take only about 24 years for wind power to meet anticipated world demand for energy in 2030 of 11.5 TW (see notes on the Jacobson and Delucchi article, above).

Future developments

Electrification of road and rail transport in the UK would add to the UK's demand for electricity but not as much as one might think:

  • In terms of energy, about 50% more electricity would be needed (see Appendix 8 of "Energy UK", PDF, 378 KB). The reason it is not more is that electric vehicles are very much more efficient than vehicles powered by the internal combustion engines. Much of the energy that we are using now for overland transport is simply wasted.

  • In practice, the additional amount of generating capacity that will be required is likely to be less than 50%. This is for two reasons:

    • It is likely that much of the charging of electric vehicles will be done at night when there is likely to be a lot of spare capacity from sources such as wind power. To that extent, it does not add to the generating capacity that would be required.

    • The electrification of road transport will facilitate the introduction of grid-to-vehicle technologies allowing two-way flows of electricity between vehicles that are on charge and the transmission grid. This, with other techniques for balancing the grid, will help to keep demands for electricity in balance with supplies, thus helping to minimise the amount of spare capacity that is required.

It seems likely that, in the future, there will be increasing use of electrically-driven heat pumps to provide space heating in buildings. But, with good insulation of buildings and the use of technologies such as inter-seasonal heat transfer, residual needs for the heating of buildings should be small. A report from the University of Cambridge shows that, using existing techniques, worldwide use of energy may be cut by at least 70%.

Limits?

In "Estimating maximum global land surface wind power extractability and associated climatic consequences" (Earth System Dynamics, 2, 1-12, 2011, doi:10.5194/esd-2-1-2011), Axel Kleidon and co-workers argue that the maximum amount of wind power that can be generated by land-based wind turbines is, at 18–68 TW, less than some other estimates. And they suggest that "some climatic effects at maximum wind power extraction are similar in magnitude to those associated with a doubling of atmospheric CO2." However, it appears that, below 10 TW, there is little cause for concern.

In "A path to sustainable energy by 2030" (see above), Mark Jacobson and Mark Delucchi estimate that total world demand for energy (not just electricity) in 2030 will be 11.5 TW and in the scenario described in their research, it is envisaged that 51% of that (5.9 TW) would be met by wind power. Since this falls well short of 10 TW, where we might start to become concerned, it appears that the Jacobson and Delucchi scenario is still valid.

It appears that the arguments in the paper do not apply to the conversion of sunshine into electricity using photovoltaics (PV) and concentrating solar power (CSP).

News reports

News reports relating the potential of renewables are marked 'R' on our News page.

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Gerry Wolff,
5 Nov 2013 09:47