Renewable energy

 
 

                

 

RENEWABLE ENERGY

"...the perception that 'real energy men don't do renewables' is changing."

Although nuclear power does not release CO2 in producing electricity, it is not a renewable source of energy. Even on medium timescales it does not represent any kind of answer to the problem of climate change:

  • When all the overt and hidden subsidies are taken into account, nuclear power is much more expensive than any other source of power, including renewable sources. At present, the nuclear industry is not required to insure fully against the costs of claims for damages from a Chernobyl-style accident. Full insurance against such costs would completely demolish any economic case for nuclear power.
  • No solution has yet been found to the problem of disposing of dangerous nuclear waste, much of which will remain dangerous for many thousands of years.
  • Nuclear reactors and nuclear reprocessing plants are inviting targets for terrorists.
  • The technology for nuclear power has much in common with the technology needed for the production of nuclear weapons. This "Janus-like character of nuclear energy" (Kofi Annan) adds to the problem of reducing the number of nuclear weapons in the world or preventing their proliferation.
  • Significant amounts of CO2 are released in the construction of nuclear power stations and in the processes of mining for nuclear fuel, processing that fuel, transporting it and processing nuclear waste.

If we are to reduce the threats of climate change, renewable forms of energy are the only option. Fortunately, these forms of energy have much more potential than is commonly supposed and can certainly meet our needs, with surplus to spare.

The rest of this web page summarises the current capability and potential of several renewable sources of energy.

No source of power is totally free of environment problems. However, the problems associated with the technologies described below are very much less than those associated with our current sources of power.

Concentrating solar power

Enormous quantities of energy fall as sunlight on the world’s hot deserts and ‘concentrating solar power’ is a proven technology for tapping in to this vast flow of energy (see, for example, www.eere.energy.gov/solar/csp.html). In one of the simplest of several variations, mirrors focus sunlight on to a tank of water at the top of a tower. This raises steam that can be used to generate electricity in the conventional way. Any solar power plant of that kind may, of course, be replicated many times.

Many of the world’s hot deserts are in countries that are relatively poor so we may suppose that concentrating solar power could be a particularly welcome new source of income.

The heat from concentrating solar power plants can be stored in melted salt or other substance so that, when the sun goes down, the power plant can continue to generate electricity right through the night.

Electricity from concentrating solar power plants may be transmitted directly to where it is needed but conduction losses put a practical limit on distances. However, solar electricity can be used to generate hydrogen by the electrolysis of water and then hydrogen can be transported by tanker or pipeline to where it is needed.

An interesting possibility is to transport solar energy, or store it, as finely powdered metal (iron, aluminium etc) or boron (see an article from the New Scientist). Instead of ‘the hydrogen economy’ we should, perhaps, be aiming for ‘the powdered boron economy’!

Another interesting possibility is to take advantage of the fact that the land under the mirrors of a solar plant is protected from the harshness of direct tropical sunlight but should receive the right amount of indirect light for growing plants—a potential horticultural bonus. An obvious problem is that plants need water and that is not plentiful in hot deserts. But sea water can be desalinated using sunlight and this may provide the fresh water that is needed.

Iran claims that it needs nuclear technology as a source of electrical power but Europe and the USA are suspicious that the technology could also support the building of nuclear weapons. However, Iran has a rich source of energy in the sunlight falling on its deserts. Europe and the USA could call the bluff of the Iranians by offering to build enough concentrating solar power plants in the Iranian desert to supply all of the country’s needs (perhaps with wind power to make up any shortfall during the Iranian winter). Even if the bluff were accepted, it would be a cheap way to buy peace of mind about Iran’s possible development of nuclear weapons.

Wind power

Modern wind turbines are now a relatively mature technology that exploit an inexhaustible, pollution-free source of energy. Wind farms are already economic and are likely to become more so in the future as designs improve and as economic weightings against CO2-emitting sources of power are increased.

The amount of exploitable wind power is massive. It is quite untrue to say, as opponents of wind farms often do, that wind energy is inadequate to meet our needs (see myths).

Wave Power

Although there is a lot of energy in waves, it has proved less easy to capture than energy from wind. From Salters Ducks onwards, a variety of systems have been designed but, for a variety of reasons, none of them have led to widespread adoption or exploitation. One of the difficulties is that wave devices can be smashed in storms or by occasional waves that are much larger than average. Making a device strong enough to withstand extreme conditions adds substantially to the cost.

One of the most promising devices is Pelamis. This 'sea snake' is a large girth tube divided into hinged sections that floats on the sea and is anchored so that it can rise and fall with the tide (thus overcoming one of the difficulties with devices that are fixed rigidly to the land). As waves pass, the tube flexes at its hinges and this flexion drives hydraulic rams inside the tube and these drive electric generators. Since the snake moves with the waves, it is less prone to damage by extreme conditions than structures that are fixed rigidly to the land.

Each 'snake' generates about 750 kw (about the same as one of the smaller large-scale wind turbines) and large numbers of them can be anchored as a 'wave farm', not easily seen from the land and thus less open to the objection that they spoil the view.

A full-size prototype has been developed and it has successfully delivered electricity to the grid. At the time of writing, a commercial order has been received for delivery to Portugal.

Tidal lagoons

A relatively new and promising idea is to exploit the energy in tides by building one or more lagoons in shallow water and generating electricity by means of turbines from the flow of tidal water into each lagoon when the tide rises and then out again when the tide falls.

An advantage of this kind of renewable power is that it is entirely predictable. And if three lagoons are built together, computerised management of the turbines can ensure continuous generation of electricity.

Possible disadvantages include the effect of a tidal lagoon on local currents and consequent erosion of the shoreline, and possible damage from quarrying if rock is needed to supplement material from the sea bed that is used to build each lagoon.

Tidal Electric Ltd estimate that the Unit price (for 1 kWhr) would be in the range 2.0 - 2.5 pence. This compares very favourably with the price estimates in the Government's Performance and Innovation Unit report 2002 which studied a range of renewable, fossil fuel and nuclear technologies (See Summary of Key Findings, Annex 6. www.number-10.gov.uk/su/energy/20.html).

Further information on tidal lagoons can be obtained from Friends of the EarthThe Guardian and a UK Government report.

Tidal streams

Another promising idea is to extract energy from the powerful tidal currents that exist in many places around our shores. The simplest idea is to install a device that is rather like an underwater wind turbine. Other ideas that have been tested are fins, rather like aeroplane wings, that are mounted on arms in such a way that they can oscillate in a tidal current.

It has been estimated that 7% of the UK's electricity requirements could be met in this way.

Further information may be obtained from a report by Black & Veatch.

Microgeneration

There is increasing interest now in the potential of microgeneration, meaning the generation of electricity by small-scale systems in individual houses or larger buildings.

Microgeneration can entail the use of any combination of:

  • Small wind turbines.
  • Photovoltaic panels.
  • Combined heat and power - the generation of electricity by small-scale generators and the use of waste heat for space heating and water heating.
  • Small-scale hydro-electric generators.