Sustainable Energy .... What's that all about?

 

Sustainable energy is about using energy wisely and using energy generated from clean sources and clean technologies. Wise energy use is the first step to ensuring we have sustainable energy for present and future generations.

Being efficient with our energy will reduce our household and business energy bills, reduce the amount of energy we need to produce in the first place and cut energy related greenhouse pollution.

So sustainable energy is not just about using renewable energy, perhaps its not even about renewable energy as we explain further below, its about using energy wisely and introducing energy efficiency measures.

Until the last ten or twenty years sustainable energy was thought of simply in terms of availability relative to the rate of use. Today, in the context of the ethical framework of sustainable development, other aspects are equally important. These include environmental effects and the question of wastes, even if they have no environmental effect. Safety is also an issue, as well as the broad and indefinite aspect of maximising the options available to future generations.

There are many who see no realistic alternative to pushing Sustainable Development criteria into the front line of energy policy. In the light of concerns about global warming due to human enhancement of the greenhouse effect, there is clearly growing concern about how we address energy needs on a sustainable basis.

 

Energy demand

A number of factors are indisputable. The world's population will continue to grow for several decades at least. Energy demand is likely to increase even faster, and the proportion supplied by electricity will also grow faster still. However, opinions diverge as to whether the electricity demand will continue to be served predominantly by extensive grid systems, or whether there will be a strong trend to distributed generation (close to the points of use). That is an important policy question itself, but either way, it will not obviate the need for more large-scale grid-supplied power especially in urbanised areas over the next several decades. Much demand is for continuous, reliable supply, and this qualitative consideration will continue to dominate.

The key question is how we generate that electricity. Today, worldwide, 64% comes from fossil fuels, 16% from nuclear fission and 19% from hydro, with very little from other renewable's. There is no prospect that we can do without any of these.

 

Sources of energy

Harnessing renewable energy such as wind and solar is an appropriate first consideration in sustainable development, because apart from constructing the plant, there is no depletion of mineral resources and no direct air or water pollution. In contrast to the situation even a few decades ago, we now have the technology to access wind on a significant scale, for electricity.

Wind is the fastest-growing source of electricity in many countries, albeit from a low base, and there is a lot of scope for further expansion. While it has been exciting to see the rapid expansion of wind turbines in many countries, capacity is seldom more than 30% utilised over the course of a year, which testifies to the unreliability of the source and the fact that it does not and cannot match the pattern of demand. The rapid expansion of wind farms is helped considerably by generous government grants and subsidies.

Apart from renewable's, it is a question of what is most abundant and least polluting. Today, to a degree almost unimaginable even 25 years ago, there is an abundance of many energy sources in the ground. Coal and uranium (not to mention thorium) are available and unlikely to be depleted this century. Uranium is even available from sea water at costs which would have little impact on electricity prices. In any case the resource can be multiplied 60- to one hundred-fold by adopting the kind of technology which our postwar forebears thought would be necessary by now - fast neutron reactors used as breeders.

 

The criteria for any acceptable energy supply will continue to be cost and safety, as well as environmental considerations. Addressing environmental effects usually has cost implications, as the current greenhouse debate makes clear. Supplying low cost electricity with acceptable safety and low environmental impact will depend substantially on harnessing and deploying reasonably sophisticated technology. This includes both large-scale and small-scale nuclear energy plants, which can be harnessed directly to industrial processes such as hydrogen production or desalination, as well as their traditional role in generating electricity.

 

Energy resources

There is abundant coal in many parts of the world, but with the constraints imposed by concern about global warming, it is likely that these will increasingly be seen as chemical feedstock and their large-scale use for electricity production will be scaled down. Current proposals for "clean coal" technologies may change this outlook. The main technology involves using the coal to make hydrogen from water by a two-stage gasification process, then burying the carbon dioxide and burning the hydrogen. Elements of the technology are proven but the challenge is to bring the cost of this down sufficiently to compete with nuclear power.

Natural gas is also reasonably abundant but is so valuable for direct use after being reticulated to the point where heat is required, and as a chemical feedstock, that its large-scale use for power generation makes little sense and is arguably unsustainable. Fuel for nuclear power is abundant, and if well-proven but currently uneconomic fast breeder technology is used, or thorium becomes a nuclear fuel, the supply is almost limitless.

 

The Hydrogen economy

Hydrogen is expected to come into great demand as a transport fuel which does not contribute to global warming. It may be used in fuel cells to produce electricity or directly in internal combustion motors. Fuel cells are at an early stage of technological development and still require substantial, research and development input, although they will be an important technology in the future.

Hydrogen may be provided by steam reforming of natural gas (in which case CO 2 has to be taken into account), by thermonuclear processes, or by electrolysis of water. Some new types of nuclear reactor such as high-temperature gas cooled reactors, operating at around 950-1000°C have the potential for producing hydrogen from water by thermo chemical means, without using natural gas.

Large-scale use of electrolysis would mean a considerable increase in electricity demand. (However, this need not be continuous base-load supply, as hydrogen can be accumulated and stored, and solar or wind generation may well serve the purpose.)

 

Wastes

Wastes ­ both those produced and those avoided, are a major concern in any consideration of sustainable development. Burning fossil fuels produces primarily carbon dioxide as waste, which is inevitably dumped into the atmosphere. With black coal, approximately one tonne of carbon dioxide results from every thousand kilowatt hours generated. Natural gas contributes about half as much as coal from actual combustion, and also some (including methane leakage) from its distribution. Oil and gas burned in transport adds to the global total. As yet, there is no satisfactory way to avoid or dispose of the greenhouse gases which result from fossil fuel combustion.