Hugh Sharman, Bryan Leyland and Martin Livermore December 2012

Transcription

1 Renewable Energy: A short guide Hugh Sharman, Bryan Leyland and Martin Livermore December 2012

2 About the authors Hugh Sharman is the Principal of Incoteco (Denmark) ApS, an energy consulting and brokering company, and cofounder of DimWatt.eu, a web-based campaign for energy security. Bryan Leyland is a New Zealand-based Consulting Engineer specialising in hydropower, power systems and markets. Martin Livermore is the Director of the Scientific Alliance and science communications consultant and commentator. Foreword The Adam Smith Institute and Scientific Alliance recently published a report Renewable Energy: Vision or Mirage? which set out to analyse the real potential contribution of the various renewable energy technologies either commercially available or under development. This was an evidence-based summary of the situation for renewable electricity generation, with a focus on the situation in the UK, but with data and conclusions more generally applicable. This paper provides a more succinct summary of the key findings and messages, updated where necessary, with some discussion of alternatives to the current targets and policies. Readers who want more detail are encouraged to refer to the original report.

3 Executive summary Wind and solar are the only sources of renewable electricity that could be deployed on a large enough scale to make any significant contribution to government targets for emissions reduction. Wave and tidal power are still far from being a commercial reality. Despite falls in capital costs, it is not economic to invest in wind or solar power without public subsidy. Onshore wind is the least expensive option and the one which, despite considerable public opposition, both UK and Scottish governments have made the most attractive for potential investors. However low the capital cost may become, the intermittency and lack of predictability of wind energy means that base load electricity must continue to be supplied from conventional or nuclear power stations. Other plant mainly gas-fired has to be kept running inefficiently on standby to supply the grid when wind farms cannot deliver. At other times, wind farms generate too much electricity when it is not needed. This either has to be sold on the export spot market at low prices or the operator has to be paid to shut the wind turbines down. Because of the need to combine renewable energy with conventional generation, reductions in carbon dioxide emissions from the electricity generating sector are lower than expected. Claims to the contrary are not based on hard evidence. Although the intermittency of renewables could in theory be accommodated using large-scale energy storage capable of operating for several days at a time, there is no practical system likely to be commercialised for the foreseeable future. Pumped hydro schemes are the best available option but their capacity is measured in hours rather than days. Continued expansion of wind farms, whether on- or off-shore, will lead to a less secure and more expensive energy supply, which will further disadvantage UK industry and push more consumers into fuel poverty. A secure, affordable electricity supply could be most effectively combined with the achievement of medium term goals for emissions reduction by investing in a combination of new nuclear power stations and efficient combined cycle gas turbines. Page 1

4 Introduction: energy security and climate change policy Modern societies are entirely dependent on a secure, reliable and affordable energy supply. Until recently, this has generally been provided mainly via a mix of fossil fuels coal and gas and nuclear. The balance between these has been set by a combination of price and government policy. In countries with appropriate geography, significant amounts of (renewable) hydropower are generated; Norway is the prime example in Europe. The other main sources of renewable energy which have been used more widely are wind and solar. Although superficially attractive as free and sustainable sources, in practice they have a number of basic problems. In particular, they are intermittent, unreliable and costly. In an unrigged market, there would be no reason to invest in them. But rational, market-based decisions have now been trumped by climate change policy. EU member states with the UK firmly in the vanguard have committed themselves to large reductions in carbon dioxide emissions (even although mankind is only responsible for some 2% of global CO 2 emissions): 20% (from a 1990 baseline) by 2020, with 15% of energy derived from renewable sources. Electricity generation carries the main burden of this and wind and solar power are being deployed on a large scale to attempt to meet these targets. The net result is that inefficient and inappropriate generating technologies are being promoted, with the price being paid by consumers in the form of higher electricity bills. Energy storage In theory, the problem of intermittency of supply could be overcome by storing energy. But the storage capacity needed is vast, and the only large-scale option currently available is to generate hydroelectricity on demand is short term pumped storage.. Proposals to use a future large-scale national fleet of electric vehicles as a distributed storage system may seem superficially attractive but we are still decades away from electric vehicles becoming mainstream, if ever. The remaining alternative is to use excess electricity to electrolyse water and store the resulting hydrogen, to be used to generate electricity using fuel cells when needed. This again is fraught with difficulties. Hydrogen needs a large amount of energy both to produce and then compress or liquefy. It is extremely difficult to retain in tanks, and fuel cells themselves are still some way from being sufficiently cost effective and efficient. Energy storage cannot be a solution to the intermittency problem for the foreseeable future. Page 2

5 Wind power Wind turbines are the generating system of choice for both the UK and Scottish governments. This is understandable in an island nation exposed to the prevailing southwesterly wind but, just because wind turbines are available does not mean that installing them is necessarily a wise idea. There are a number of factors which need to be considered. 1. Capacity factor Wind power is not available on demand, and its variability means that its capacity factor (the percentage of rated capacity actually produced) is not only lower but unpredictable. The average capacity factor for UK offshore wind is 28% and for onshore, 24%. Many of the windiest sites have already been built on, and further wind farms are likely to have even lower capacity factors. This means that a wind farm rated at 10 MW produces anything from 0 to 10 MW depending on the wind conditions. Although it is technically capable of producing over 85 GWh of electricity over a year, the actual output is likely to total not much more than 20 GWh. We may be told that such an installation can supply enough electricity for about 1800 homes (with an average consumption of 48,000 KWh), but in practice the output would only be enough for only 450 over a typical year. 2. Intermittency Coal, gas and nuclear stations can produce a known, reliable amount of energy when needed; the energy they produce is said to be dispatchable. Wind energy is not dispatchable, and output can vary between zero and 100% over a range of timescales. Not only do turbines not turn when the weather is calm, but they have to be shut down when wind speeds are much above 50mph to prevent serious damage. Back-up, dispatchable power plants must always be available to supply demand and balance the grid as wind output fluctuates. Winter peak power demand often coincides with very large, slow-moving anticyclones, which bring extremely cold weather and cover most of NW Europe. Summer anticyclones coincide with peak cooling loads. 3. Emissions reduction The primary purpose of the push for renewable energy is to reduce carbon dioxide emissions by displacing fossil fuels. In actual fact, conventional stations have to be held on standby to supply the grid when wind farms cannot. Figures from Ireland, which has a larger percentage of its generating capacity as wind farms than does the UK, show that, as the amount of wind energy supplied increases, then the savings in carbon dioxide emissions decline. There comes a point where additional wind energy produces no further savings. In Denmark, despite the large number of wind farms, no coal-fired power stations have been closed. Page 3

6 4. Visual impact Since they are erected in areas of open countryside, often on hills, wind turbines present a real visual intrusion and many planning applications are vigorously opposed by local residents. The situation is made worse by a trend towards installing larger, more efficient turbines. Many applications are rejected at the planning stage, although this local decision making is also often overridden on appeal to central government. The obvious response is to build more wind farms offshore, but costs are even higher and installation and maintenance problems much greater. Wind turbines have an estimated service life of only 20 years and, once they become weakened by metal fatigue, the entire assembly has to be scrapped. If the subsidies on which wind turbines depend are no longer available at the end of their relatively short life, they will not be replaced. Their only legacy will therefore be abandoned bases, redundant power lines, lost jobs, wasted capital and needlessly damaged landscapes. 5. Cost Onshore wind is the least expensive of the renewable energy technologies. However, it still receives significant subsidies via feed-in tariffs, and few new turbines would be erected without this incentive. Landowners can receive a significant income for the life of the wind farm, while their neighbours suffer and contribute via higher electricity prices, despite local sweeteners being handed out by wind energy companies. It is little wonder that the high rewards on offer have triggered an upsurge in wind farm applications. Not only are operators able to recover their initial investment within six years, they can then look forward to a further twenty years guaranteed income from government backed figures. Even if the subsidies are dropped, existing operators have legally enforceable contracts. Offshore wind is considerably more expensive, both because of the cost of erecting the pylons on the sea bed and also because of the need to lay underwater cables to bring the supply to land. Consequently they command double the subsidy of land turbines. All wind energy should also carry the cost of conventional generating capacity needed as backup, but this is not how the official figures are calculated. 6. Credibility of government targets To achieve its targets for 2020, the government hopes that onshore wind power can be expanded from 4GW to something between 11 and 14GW, while offshore wind expands from 1.5GW to between 11 and 19GW (assuming a 35% capacity factor). The target for installed wind power is thus something between 22 and 33GW. Few experts believe that such ambitious targets are physically or financially achievable. For example, nearly 5 turbines must be installed each working day, starting now, and then all the way through to 2020, in order to achieve the target for offshore wind energy. Page 4

7 The Scottish government intends the country to generate the equivalent of 100% of its electricity from renewables, with an interim target of 50% by 2015; a much more ambitious target even than Denmark. The power generated by wind (for the only other source of renewable energy in Scotland is hydro, contributing less than 10% of total capacity) will rarely, if ever, be in balance with demand. In Denmark in 2009, 20% of the electricity generated was from wind farms, but only 10% of electricity consumption was from wind. Denmark has a network of interconnector cables with neighbouring countries (Norway, Sweden and Germany) and so effectively forms part of a regional grid. The 20% of electricity generated from wind farms in Denmark is, in reality, a much smaller proportion of a multinational electricity grid. As the output of wind farms rises, the spot price of electricity drops. Denmark is therefore exporting at least half of its expensive wind energy at a loss and importing an equivalent amount of Norwegian hydro power or Swedish or German coal or nuclear power when spot prices are higher. Scotland will have even larger net inflows and outflows of electricity, which will be completely outside its control. Solar There are only modest ambitions for the use of solar power in the UK, given its high cost and low efficiency at such a high latitude. The main purpose of government providing subsidies seems to be to provide very visible renewable electricity micro-generating units in a way which receives few public objections. In economic terms they make no sense at all. There are two types of solar power. The first, and more familiar, is photovoltaic, using arrays of cells that convert sunlight directly into electricity. The second uses sunlight to heat a liquid that boils and drives a turbine, which is even more inefficient than photovoltaic. Solar is the most expensive source of renewable energy yet commercialised and would only be used in very special circumstances without some form of financial incentive. In the UK, the chosen method is to pay a (high and guaranteed) feed-in tariff for every unit of electricity generated, whether it is sent to the grid or used at source. Without these subsidies, the grid-connected solar energy industry would not exist. As a result of them, solar power is being developed in countries in northern latitudes where the sunshine is less intense and skies are often cloudy. Typical capacity factors in desert areas are about 21%, but in high latitudes they can be 10% or less. In addition, they produce no energy on cold winter evenings, when demand is at its peak. Page 5

8 Biomass Large amounts of biomass (currently mainly cereal grains and edible oils) are turned into biofuels for road vehicles. This has a distorting effect on world markets and has only a small effect on carbon dioxide emissions once land use changes have been taken into account. Despite this, EU politicians are still tied to targets for 2020 and beyond. Biomass for electricity generation or heating is superficially more attractive, since the feedstock is agricultural by-products or forestry waste. However, while this may make sense on a local scale, biomass has a lower energy density than fossil fuels and transport charges therefore increases its cost for large scale use considerably. Drax and other large generating stations now use large amounts of wood chips, but this is simply to achieve their renewables obligation. The UK cannot supply enough to meet demand, but importing the majority of it still makes sense to the operator because of the subsidy available. Other renewables Hydro power: At the end of May, 2010, the UK had 78 hydropower plants (excluding microhydro), mostly located in Scotland, delivering 1,420MW in total. Hydro power can be a useful part of the mix where the geography is right, but cannot deliver electricity reliably during dry periods. In the UK, there is essentially no scope for further expansion. Wave power: There are no commercially operating wave power stations in the UK, although the country hosts the European Marine Energy Centre in Orkney. A fundamental problem with wave power is that any device that recovers energy from the waves needs to be able to survive a very large storm (and do so repeatedly). This means that it must be designed for the most extreme conditions likely to be encountered, while generating a useful amount of electricity over the year when operating at much lower levels of wave power. Although development will certainly continue, there is little prospect of any workable, commercial technology appearing for the foreseeable future. Tidal power: Vast quantities of water are moved in a regular and predictable way, and particular geographies can concentrate the flows into regions of high potential. Tidal power comes in two forms: schemes that use a barrage and those that rely on tidal currents. There are few barrage schemes in existence. In the UK, over the last 70 years, an enormous amount of effort has been put into schemes for a Severn barrage. A major drawback is that the station would generate for only about eight hours out of 24, operating only when the tide is ebbing, twice a day. The latest version of the scheme, currently estimated to cost 30 bn, adds little firm capacity to the system and would require a large amount of expensive backup generation. There are a number of tidal flow schemes mooted, particularly in the Pentland Forth and Alderney, but there are few suitable sites and both cost and intermittency remain problems. Page 6

9 Renewable energy technologies: the competition For the UK, the previous reliance on coal has been transformed into dependency on gas, while the significant contribution of nuclear (peaking at about a quarter of total supply) will decline rapidly over the coming decade as existing stations are closed. This capacity has to be replaced, but the big question is with what. The following remain proven, viable technologies: Combined Cycle Gas Turbines, which are efficient, cheap and quick to build. However, the dash for gas towards the end of last century has already resulted in a strong reliance on a single fuel from geo-politically sensitive areas. More recently, as US experience has shown, exploiting shale gas reserves has the potential to reduce regional gas prices considerably. Gas will be a major part of the energy mix for the foreseeable future, but at an unknown cost. Nuclear reactors. Nuclear fission has been shown to be a reliable, safe and secure power source. In addition, the stringent limits on exposure to radiation are unnecessarily low and add considerably to construction and operational costs. Nuclear power is also the only generation technology capable of providing a reliable base load with essentially zero carbon dioxide emissions. New generation pressurised water and boiling water reactors are being built, and further developments of fast breeder technology could turn nuclear waste into a valuable source of fuel. Modern coal-fired power plants also remain a reliable and cost-effective option, although carbon pricing puts them at risk. The EU response has been to encourage Carbon Capture and Storage technology, whereby CO 2 is removed from the flue gases, compressed and injected into depleted oil fields or onto the deep sea floor. But this is an expensive option, has not been proven on a large enough scale and is energy-intensive, requiring even more coal and gas to be extracted. With the present state of technology, the best way to maintain a secure and affordable electricity supply while reducing carbon dioxide emissions is to invest in a new and expanded fleet of nuclear stations for base load plus efficient gas turbines to deliver the balance. Local use of renewable energy small-scale hydro, anaerobic digesters or biomass burners would make sense in particular circumstances, but large-scale deployment of wind or solar power without large scale energy storage is not a sustainable option. Page 7