There are a limited number of ways that we can reduce our ecological footprint. We can do what we do more efficiently, using and wasting less of the planet’s resources. We can abstain from ecologically demanding activities – for example, by travelling less and eating less meat. And if there were fewer people, particularly those who lead affluent lifestyles, then the demands made on the planet’s resources would be greatly reduced. But the march of progress is not usually associated with us voluntarily going without those things that make life more pleasant, and population control is a sensitive subject. So we are left with getting more out of the resources we consume in the processes of energy generation and distribution, agriculture, waste management, transportation and manufacturing. ‘Cleantech’ products, which embody new scientific approaches to solving ecological problems that also boost productivity, can help achieve this goal while providing competitive returns on investment. In this article I shall focus on the technologies most likely to fulfil the cleantech promise in the area of electricity generation.
Energy is at the heart of the human story. From the dawn of human life until the mid-eighteenth century, we were limited by having to derive almost all our energy from animal power. Camels turned the oil presses, oxen ploughed the fields and oarsmen powered the galleys. But with the advent of the Industrial Revolution this constraint suddenly disappeared. One kilogram of coal contains the energy equivalent of 13 horses; there is the same amount of energy in 650 grams of oil and in just 43 micrograms of uranium (a microgram is one millionth of a gram). The global population, having grown slowly over hundreds of thousands of years to about 750 million by 1750, has since leapt almost tenfold on the back of the power available from these revolutionary new energy sources, and many of us now enjoy lifestyles unimaginable even 50 years ago. But in the past 250 years the burning of fossil fuels and cement production have released approximately 329 billion tons of CO2 into the atmosphere, with 50 per cent of this figure being accounted for in the past 30 years. Global annual emissions are still increasing, and there is now virtually incontrovertible evidence that this is altering the earth’s climate in ways which pose serious threats to many ecosystems on which human and other forms of life depend. The race, therefore, is on to find viable alternatives.
Energy sources are either fossil fuels (coal, gas and oil), renewables (wind, solar, hydro, geothermal, biomass, wave and tide), or nuclear (fusion and fission). In addition, there are two generation/consumption configurations: large-scale centralised electricity generation delivered through an extensive distribution network – the ‘grid’; or local generation, usually relatively small-scale and delivered directly to consumers. The latter, known as ‘microgeneration’, is often associated with combined heat and power (CHP) systems which use the heat produced alongside electricity to deliver hot water and heating to local businesses and homes instead of wasting it – in a typical utility-scale generating station, as much as 50 per cent of the energy input is lost in this way and almost a further 10 per cent is lost in the grid.
Estimates indicate that meeting the current 40GW of average electricity demand in the UK would require either about 30 power stations (fuelled by coal, gas, oil or nuclear power), land-based wind turbines covering an area the size of Wales, a solar photovoltaic (PV) panel the size of Cheshire, or an area slightly larger than Scotland entirely devoted to growing biomass for conversion into fuel. Furthermore, given the intermittent nature of renewable energy sources, if sufficient electricity is to be generated to meet demand throughout the day, every day, then it is impossible to contemplate an energy mix that does not include large power stations. In light of this reality, it is important to bear in mind that only nuclear power stations are not powered by fossil fuels, and that, despite much ill-informed comment, nuclear power has the best safety record of all modern forms of electricity generation.
Nuclear is part of the future
Nuclear power comes in two flavours: fission and fusion. Fission, the splitting of heavy atoms of nuclear fuel (usually uranium), releases vast amounts of energy and is the basis of the atomic bomb and civil nuclear power. Meanwhile fusion, the combining of light atomic nuclei to form a heavier nucleus, releases many times more energy than fission. Fusion is the basis of the hydrogen bomb, but the process has yet to be tamed for civil power generation purposes. (ITER, an international project based in France, is building a prototype fission generator expected to come on stream in 2018.) Negative perceptions persist about nuclear power both because of the highly toxic radio-active waste they produce, albeit in very small quantities, and because of the risk of rogue states using civil nuclear facilities to pursue military ends. These problems are being addressed by international projects to develop a new generation of nuclear power systems – the so-called Generation IV reactors which aim to improve safety, reduce waste, use existing nuclear waste as a fuel, guard against proliferation and greatly increase energy efficiency. However, these reactors are not expected to be in production before 2030.
A novel approach to nuclear is being pursued by TerraPower. Championed by Bill Gates, TerraPower’s Travelling-Wave Reactor (TWR) is now at an advanced design stage and looking for its first practical application. The key distinguishing feature of the TWR is that it runs on depleted uranium, the waste product from existing nuclear reactors, of which there is an almost inexhaustible supply. The reaction is set off by a small amount of enriched uranium, after which the TWR runs for the rest of its operational life (60-100 years) on nuclear waste preloaded into a sealed container. Benefits include the reactor not having to be refuelled or have its waste removed until the end of its 60 to 100 year life, and a partial resolution to the problem of high-level nuclear waste disposal through the conversion of existing stockpiles into a valuable new resource. The TWR’s inventors calculate that the 700,000 tonnes of depleted uranium waste already stockpiled in the US would, through the use of their reactor, provide a 3000-year energy reserve (worth some $100 trillion) for the country.
A major attraction of solar PV is that it is easily scalable to small applications. In the UK, with interest rates currently low and the recent introduction of government subsidies and feed-in tariffs (whereby surplus power generation is sold back to the national grid), a better return can be obtained from installing solar power on your house than leaving the money in the bank. Current commercial solar PV technologies are capable of converting 20 per cent of light energy into electricity, but this conversion rate is constantly being increased through new technologies – Sharp recently unveiled a product with 35.8 per cent efficiency.
Although solar technology has been around for many years, it is only now that its efficiency has been developed sufficiently to make it economically viable. One disadvantage of solar PV, however, is that in the winter, when electricity demand is at its highest, the amount of light and therefore the amount of power generated is at its lowest.
Giant wind turbines are now commonplace in many rural and offshore areas. The power output of a wind turbine is proportional to the square of the wingspan – 10-metre blades produce 100 times as much power as one metre blades, hence the trend towards ever larger wind turbines, which are much more visually intrusive on the environment. Aside from the emissions associated with the manufacture and installation of turbines, wind power produces no greenhouse gas emissions. Most wind power installations are in remote locations and these installations are subject to the same transmission losses as other generation systems which distribute power through the national grid.
There are many other innovative energy systems being planned, including the SuperSmart Grid (SSG), which envisages vast amounts of electricity being generated from solar PV cells in North Africa and distributed across Europe via a new direct current transmission system that greatly reduces transmission losses. A complex layer of computer intelligence would constantly monitor energy production and consumption so as to maximise efficiency. The SSG could have a major impact in reducing emissions, but is still some way from being realised. Nonetheless this and other technological innovations might be vital to decreasing the amount of energy that is wasted as it moves through our distribution networks.
Cleantech products are rapidly evolving, and there are already many economically viable options for consumers, large and small, to reduce their impact on the environment. These products offer great hope for the future but it is most unlikely that, on a global scale, technology alone will reduce emissions to a safe level. Lifestyle changes and a smaller population remain the elephants in the room.