'Renewable' energy technologies
can't hack it in the market place

This article considers the so-called 'renewable' energy sources with a view to assessing their potential impact on the markets for fossil fuels, especially coal. Any assessment of the potential for the 'renewables' requires an understanding of the nature of energy, the sources available for its use, the ways in which its sources can be considered to be'renewable', and the ability of each'renewable' energy source to compete with the so-called non-renewable sources of energy. There are very many types of potential'renewables', and it is essential to consider the nature of all and each of them if their present and potential competitiveness is to be assessed.

The nature of energy

Every schoolboy knows that energy is the ability to do work. It is useful when it is flowing from one place to another because its flow can make things change. And work is anything which changes. Energy flows from regions where it is in high concentration to regions where its concentration is lower. For example, heat flows from hot to cold areas, and water runs downhill not up. The flow of energy can be reversed in localised regions; for example, water can be heated to make steam. But the net effect of a system which concentrates energy in one place is to increase the overall distribution of energy (scientists call this'increasing entropy').

The natural flow of energy from a high concentration to a lower concentration may be utilised to conduct work, and this is demonstrated by all energy systems from log fires to nuclear power stations. All usable energy comes from the'big bang' which most scientists believe initiated the universe. All energy flows are stages in the process from that event to the time when energy will be uniformly distributed throughout the universe and then everything will cease. Scientists call this ultimate end of everything'the heat death of the universe'. This will be billions of years in the future so we need not worry about it. But it is important. The original state of higher energy concentration can never be replaced: it is lost for ever. In absolute terms,'renewable' energy is impossible.

The nature of fuels

Fuels are stores of energy. They accumulate the energy of a small energy flow so the collected energy can be released as a large flow. This is like a dam which blocks a small river. The unrestricted flow of the river may move grains of sand beneath the water, but it can do little else. Sudden release of the water collected behind the dam can move large boulders.

Fuels are commodities. They can be stored, transported and used when and where required. Energy flows are not commodities. They cannot be stored, transported and used when and where required. For example, wind, sunlight and electric current are not commodities. They cannot be stored in significant amounts and must be used at existing distribution systems when they flow. But electric charge can be a commodity, as torch battery sellers can testify. The so-called'renewable' energy sources have two basic types:

• Some'renewable' energy sources have fuels. But these fuels are only used at a rate less than the rate at which a natural energy flow generates the fuel.

• Some'renewable' energy sources do not have fuels. They only tap-in to natural energy flows.

Both these types have severely limited uses. They are like the small river which has no dam.

Available sources of energy

There are three available sources for the energy in fuels. They are

• the energy flowing from the sun,

• the residual energy from the formation of the solar system, and

• the residual energy which was concentrated in ancient — now dead — stars.

All these three sources of energy are used and have been suggested for provision of 'renewable' energy. Energy flowing from the sun consists of radiations and particles. To date, only sunlight and solar heat have been utilised as energy sources by man. Residual energy from the formation of the solar system is observed in the power of the tides and geothermal forces. Indeed, it can be argued that the Earth and Moon system is still forming because these processes still continue. Processes which initiated during the lives of ancient stars have generated radioactive substances notably uranium. Amounts of these substances were part of the material which accreted to form the Earth, and they may be utilised as fuel in nuclear power plants.

Types of'Renewable' energy systems

There are ten basic 'renewable' energy systems for power generation, and most of them have a variety of possible methods some of which have been developed. They are:

• 'renewable' nuclear power,

• 'renewable' fossil fuelled power,

• wind power,

• wave power,

• tidal power,

• direct solar power,

• geothermal power,

• hydro-power,

• bio-mass power, and

• thermal gradient power.

It is worth noting that some of these systems have existed since long before the large-scale use of fossil fuels. They lost favour when it was recognised that fossil fuels could provide much larger — and so more useful — flows of energy. The Industrial Revolution then resulted.

'Renewable' nuclear power

Most existing fission reactor nuclear plant are not renewable energy systems. However, breeder reactors can moderate substances to generate as much fuel as they use, so they are a potential renewable energy source. The substances to be moderated are put in the reactor and this exposes them to radiations which convert them to radioactive nuclear power station fuel.

It is not clear why this renewable energy technology would be desired. When fast breeder reactors were conceived it was thought that uranium was scarce, but uranium is now known to be more common than copper. There is sufficient uranium to meet human needs for centuries. It is probable that fission reactors will be replaced by nuclear fusion plant long before there is a shortage of uranium. Fusion plant would not use uranium; they would use hydrogen which could be extracted from water. Also, the fuel produced by breeder reactors is plutonium which is capable of misuse for nuclear weapons production. Japan continues to try to perfect a nuclear breeder reactor, but research into breeder reactors has been abandoned by other countries with nuclear power industries.

'Renewable' fossil fuels

Peat is the only fossil fuel which could be used as a 'renewable'. Coal, oil, natural gas and peat continue to be formed by natural biological and geological processes, but these processes are very slow and most take geological ages. Fossil fuels would be 'renewable' energy if their uses were reduced to rates which equalled their formation. This is only possible for peat. Fossil fuels are the most effective use of solar power. They represent the remains of energy collected by living things over long times (geological ages) and large areas then compressed into small volumes. This high collection efficiency makes fossil fuels the most economic form of solar power.

Fuels are commodities and it is reasonable to consider their reserves and resources. Reserves are the amounts which can be obtained at economic cost. Resources are the amounts which could be obtained using available or imagined technology. The world has oil and gas with reserves and resources of about 50 years and 100 years, respectively, at current production rates. Demand for them continues to grow, so their reserves are likely to increase to match their resources and their prices will increase. The world's coal reserves and resources are about 300 years and 1000 years, respectively, at current production rates. Oil and gas can be made from coal, and this will become progressively more economic as oil and gas prices rise. This means that there is no reason to constrain fossil fuel usage. Nobody can know what the world will be like in 300 years time.

300 years ago land transport relied on horses which consumed grass, hay and oats. Modern transport systems are not limited by the availability of grass. It would be foolish to constrain the use of fossil fuels because they may become scarce at some time after the year 2300.

Wind power

Wind is the movement of air. The energy in wind is solar energy collected over very large areas of the surface of the planet. But air has low density, so the concentration of the energy is small and very high wind velocities are required to provide high energy flow. Wind power has been used for centuries. Wind energy powered most of the world's shipping for thousands of years and wind power could assist modern shipping by use of automated sails: Japan has conducted several studies of this.

Primitive wind turbines powered pumps (notably in the Netherlands and England) and mills throughout Europe for centuries. Since the 1970s, the use of modern wind turbines has become popular for electricity generation in some places. This is especially true in parts of the USA. Reasons for this are entirely political. The low energy concentration in wind requires use of very many turbines with associated very high capital and maintenance costs. Also, the output of the turbines depends on the weather and, therefore, cannot be predicted with accuracy for more than a few days in advance.

Wind turbines generate electricity which is not a commodity. It cannot be stored in significant amounts and must be used at its existing distribution system when generated. It is not possible for wind turbines to produce electricity as cheaply as coal-fired electricity. The high capital and maintenance costs of each turbine provide only the small return it can obtain by extracting the little energy which is carried by normal winds. Hurricanes, cyclones and tropical storms do carry large amounts of energy but they are rare. A turbine designed to collect energy from tropical storms would rarely operate, and a turbine designed to collect energy efficiently from ordinary winds would be damaged if it tried to operate in a tropical storm.

Additionally, wind turbines have significant environmental costs. Some people dislike their appearance, but this is a matter of aesthetic opinion. More importantly, they provide serious noise pollution down-wind. An efficient wind turbine blade removes much energy from the air. For this reason, a rotating blade generates pulses of reduced pressure in the air flowing behind the turbine which are heard as loud, throbbing noise. This may not matter in isolated hilltops in California, but a wind turbine was shut-down by a law court in the South West of England because its unbearable noise was directed at a local farmhouse.

Winds are stronger and more constant at sea than on land, and the noise pollution from wind turbines would not be a problem at sea. But large ocean waves would be likely to displace the turbines from their moorings unless the turbines' mountings were very expensive.

Wave power

Ocean waves are also solar energy collected over very large areas. The density of water is much more than that of air so waves carry a lot of energy. This is why wind turbines could be dislodged by strong waves. It also means that wave energy collectors are potentially more efficient than wind energy collectors. Several methods are being developed for collecting energy from waves. They have potential for generating economic power along the west coasts of Europe, the US and Africa.

The first large-scale wave energy generator was called the Osprey and was installed off the west coast of the UK during August 1995. It was intended to provide 2 MW from the waves and another 1.5 MW from a wind turbine mounted on its top. The wind turbine was added as an afterthought: the high cost of foundations for a wind turbine at sea were free because the wave generator was to be the foundations.

The Osprey's wave generator consisted of a hollow box open at its bottom with a tube from its lid extending high into the air. It was intended that each passing wave would raise the water level in the box and thus push air out the tube. Then, when the wave had passed, the water level would fall in the box and suck air back down the tube. The energy of the rising and falling water would be conveyed to the air movement squirted and sucked rapidly through the tube, and wind turbines mounted in the tube were to extract the energy from these air movements. These turbines would usually work at near their optimum efficiency because the tube would constrict the air flowing to and from the box. Small waves would make small changes in water depth but this would provide fast air movement through the tube. Large waves would make large changes in water depth but the constriction would inhibit too fast movement of air through the tube.

Several variants of the Osprey concept have been suggested in the past, and some other wave power systems have been assessed, notably the 'Salter ducks'. These 'ducks' are one version of floats which oscillate about a fixed rod as each wave passes, and the oscillations are used to generate power. Another assessed system uses an array of floats connected by flexible couplings. These arrays are called 'wave mats' which flex as waves pass beneath them, and their flexing is used to generate power. But the Osprey was the first attempt at large scale power generation from waves. Unfortunately, the Osprey sank during its installation.

The Osprey's failure at its initial attempt demonstrates the difficulty of resisting the power of the sea in order to utilise that power. The Osprey was designed by Applied Research and Technology (ART), and ART's Managing Director, Allan Thomson, had expected that the Osprey would not move even if struck by a "100 year wave". It sank in relatively calm weather. Other difficulties of wave power are its dependence on appropriate weather for "good" waves, potential effects on nearby coasts, and risk of accident.

The reliance on weather provides difficulty in accurate prediction of future power generation. But this does not prevent such systems having use. For example, they could be used to power desalination plants in remote coastal areas: the purified water can be stored. Removal of energy from waves means that less wave energy would be received at the coasts. This could affect the coastal ecologies and the distribution of sediments along the shores. Unintended release of a floating generator (or set of generators) from its moorings could induce a disaster.

Tidal power

Waves are not the only sea movements which have potential to provide usable energy. The tides also move a lot of water. Tidal power has not been utilised in any substantial amount. Tides do move immense amounts of energy around the Earth. But the Earth is a big place, so the tidal energy flow is small at any point on the Earth.

Sensible utilisation of tidal energy requires that the energy of very large amounts of moving water must be collected. The collection consists of sampling changes in gravitational potential energy provided by the tidal rise in the level of sea surface. Either the raised water must be constrained so its later downward flow can do mechanical work, or a heavy weight must be lifted by the raised water so its later fall can do mechanical work. This requires use of very large barrages to contain the moved water or enormous floats to raise the heavy weight. Both these methods have very high capital and maintenance costs. The energy they would produce would be much more expensive than coal-fired or nuclear power stations, for example.

The world's largest tidal power station is at La Rance on the Brittany coast of France. It has operated since it was constructed in 1966 and generates 550 GWh of electricity each year. It is an experimental installation and so the very, very high costs of its electricity cannot be directly compared to the costs of commercial power stations. But studies using this tidal barrage indicate that tidal power would cost at least three times more than coal-fired electricity.

Extreme environmentalists claim that the high cost of tidal power is worth paying because tidal power removes the need to use fossil fuels. But using tidal barrages and tidal floats would be environmentally disastrous. The barrages would destroy the coastal ecologies in and near the areas of the constrained water. A float would have ecological effects on nearby shores, and the potential effects of an escape of a float from its moorings are too awful to contemplate.

Direct solar power

Solar energy which reaches the surface of the Earth is very diffuse. It must be collected over very large areas or large times to be useful. And it heats and lights the ground. Removal of significant amounts of solar energy from one place to use it in another could have unpleasant climatic effects. Only small amounts of direct solar energy can be collected without need for another energy source to replace the collected heat and light. This limits the ability of direct solar collectors to provide usable electricity generation in many places. Local ice-age would be worse than global warming. For example, using direct solar energy collectors to replace a 2 GW coal-fired power station in the UK would cover 23 per cent of the UK with the collectors. A 2 GW coal-fired power station is typical for the UK where there are 19 of them in use. However, local cooling may be a desired objective in some hot climates.

Three basic technologies exist for direct solar collection. They are photovoltaic cells, solar boilers, and heat ponds. Photovoltaic cells convert solar power directly to electricity. They are often used to power communication satellites and pocket calculators. Their production costs are very high, but materials developments are reducing these costs. However, there are no foreseeable circumstances where developments of photovoltaic cells could be used for economic electricity generation at a significant large scale because of the high capital costs.

An additional problem with photovoltaic cells is that they generate electricity when the sun shines and not at night. And electricity is not a commodity. Solar boilers consist of arrays of mirrors which concentrate the heat of the sun's rays onto a container of a fluid, usually water. The boiled fluid can then be used to power a turbine. Many experimental arrangements of these systems exist. They have high capital cost and require much maintenance. It is just possible that such a system may be profitable in very hot regions of the world which do not have indigenous fuels.

The Weizmann Institute in Israel is developing an especially interesting solar boiler system. This system uses solar heat to make a fuel. Its array of focusing mirrors can create temperatures of 2000 degrees Centigrade — which is hotter than the flame in a PF power station — but it normally operates at 1000 degrees Centigrade. The heat is not used to boil a fluid but to cause a chemical reaction. Methane is reacted with steam or carbon dioxide in the presence of a catalyst. This reaction absorbs the heat and creates a mixture of hydrogen and carbon monoxide gases which can be stored. This mixture is a fuel which can be stored, pressurised and transported. Another catalytic reaction converts the gases back to their original form, and this releases the collected solar heat when it is needed. Israel Dostrovsky is in charge of the project which is now testing a 0.5 MW demonstration unit. He says that he is negotiating to have a 10 MW unit built, but he cannot yet say where.

Heat ponds consist of pools of water in tanks with dark coloured (usually black) bottoms inside transparent covers which prevent evaporation. The water absorbs much solar heat. In very hot regions of the world this can generate usable heat to assist power generation. In much of the US and Europe, heat ponds which cover roofs can be a useful method to increase the amount of solar heat absorbed by buildings and thus reduce other heating requirements.

The problem of low solar flux at the Earth's surface has been addressed by several proposals. They all utilise mirrors in space. The simplest systems would focus additional solar energy at solar boilers on the ground. The others focus the energy on satellites which convert it to high-energy radio waves which can be directed at receivers on the ground. All these suggested systems would have tremendous risk. Failure to sustain focus on the ground targets could provide a disaster on an unprecedented scale.

Passive solar power is much more useful. Indeed, everybody uses it all the time for heat and light: it is the solar energy which falls on us. The efficient use of passive solar could be improved, especially in buildings. For example, thick walls can absorb solar heat during hot days and release it during cold nights. This is an example of efficient energy use. Not wasting energy could make significant reductions in the demand for electricity. The environmental group Greenpeace estimates that nearly a quarter of Europe's electricity demand could be removed if energy were not wasted.

Geothermal energy

Some places have a surfeit of energy. They include Iceland which has an abundance of geothermal power and obtains most of its energy from geothermal sources. Geothermal energy is heat from beneath the ground. Where it is possible, it is very economic. Few sites exist where additional geothermal power can be obtained. This has led to some studies attempting to utilise "hot rocks", for example in Cornwall, UK. All such studies have failed (which is not surprising). There is no possibility that new technologies will extend the potential for geothermal energy in the foreseeable future. In centuries to come it may be possible to utilise heat directly from the molten layers of the Earth's mantle, but no potential methods for this exist.

Hydro-power

Hydro-electricity is also very economic for large scale power generation, and so it is also used where appropriate. It relies on the collection of rain, and so it is a form of solar energy collected by evaporation of water over very large areas. Very small-scale hydro-electricity is useful for producing domestic energy in individual dwellings of isolated communities in developing countries. The charity 'Intermediate Technology Development Group' has perfected systems for this and is supplying them.

Artificial hydro-electricity is also used and is called "pumped storage". Electricity is used to pump water up hill when there is little demand for the generated power. The water is then allowed to flow back and generate electricity when there is high demand for it. This overcomes some of the problems caused by the fact that electricity is not a commodity.

Bio-mass energy

Like wind power, bio-mass is an ancient idea which has recently again found favour. Simply, bio-mass consists of utilising biological wastes or harvesting crops for use, as — or conversion to — a fuel. Cattle and camel dung are still burned as fuels in many poor villages. Coppicing and charcoal manufacture were standard forms of bio-mass usage throughout much of Europe for centuries. The burning of dung is not commercially viable for large-scale power generation. But there are disposal costs for human faeces, and some cities are finding it economic to burn sewage then to use some of the resulting energy for power generation.

Harvested bio-mass is a renewable energy source when the amount of harvested crop is not more than the grown crop. The harvesting of wood for fuel in much of the third world is not a renewable source because the harvest is depleting the stock of trees. The European Commission has advocated use of bio-mass as an alternative to paying farmers for producing nothing under the 'Set-Aside' scheme of the Common Agricultural Policy (EEC Commission, ref. P/91/67, 25.9.91). However, on its own this would be very uneconomic.

Renewable bio-mass collects solar energy over a small area and one growing season. Energy is consumed by harvesting and transporting the bio-mass to its point of use. There is a net loss if the farming and transport consume as much energy as use of the bio-mass provides. This sets a limit on the area where the bio-mass can be profitably grown in any one place. It is not possible for bio-mass on its own to compete with coal nor nuclear power which are fuels which contain high concentrations of energy.

The Set-Aside Scheme does provide a special case for bio-mass in the EU. The large capital cost of a power station cannot be justified for the returns from use of bio-mass. But crops grown very near to an operating power station could be a small amount of cheap fuel. Hence, a power station could increase its profitability if it could substitute bio-mass for some of its fuel at the height of the harvest season. The fluidised bed combustion (FBC) technologies, air blown gasification combined cycle (ABGC), and the liquid solvent extraction (LSE) process have sufficient fuel flexibility to do this. The economics of one of these systems would be improved by substitution of the small amount of bio-mass which was cheaper than its coal feed.

Other forms of bio-mass include synthetic chloroplasts with accelerated growth to improve yields, and production of methanol from plants for transport fuels. Simple calculations of the solar energy collection at the Earth's surface demonstrate that none of these developments can be economic.

Power from thermal gradients

In 1975 Philip Carson in the US suggested giant towers to make cheap electricity from falling air. He suggested that a hollow tube at least 1 kilometre long should be stood on its end to form a tower. Then, tonnes of sea water should be pumped up it and sprayed into its top. The water would evaporate and thus cool the air. Cold air falls, and the cooled air would fall down the tube at 60 kilometres per hour. Wind turbines mounted at the bottom of the tube could then produce a large, controllable amount of constant electricity. In theory, Carson Towers (sometimes called "energy towers") could supply all the world's electricity needs several times over. And the electricity would be very cheap, costing about a third of the cost of coal-fired electricity. Laboratory studies show that they should work.

The Technion Institute in Haifa has produced detailed designs for construction of a 50 MW prototype Carson Tower which would only be 200 meters tall. But this would only demonstrate the principles. Proving the economics of the process would require construction of a Carson Tower which is at least 900 meters tall, and that would cost at least US$650 million. Nobody is yet willing to make that gamble.

Air is not the only fluid which can have temperature gradients. It has often been observed that the oceans are much colder below the thermocline than at their surfaces. This provides potential for a significant energy flow with large capability for electricity generation. No method for use of this principle has yet been developed for large economic electricity generation, but the ocean thermal energy conversion (OTEC) device is a step towards it. The Japanese have built several OTEC units of between 50 and 100 kW output for experimental purposes. Each OTEC unit works just like a refrigerator and uses two heat exchangers containing ammonia. Warm water from the surface is supplied to one heat exchanger and this evaporates the ammonia.

The expanded gaseous ammonia then passes through turbines to generate electricity. Meanwhile, cold water is pumped from below the thermocline and is supplied to the other heat exchanger which condenses the ammonia, so the cycle can continue. A similar system has recently been suggested to utilise the temperature gradient between the warm water of sea surface and the cold air of the stratosphere. It is not possible for developments of the OTEC system to provide electricity as cheaply as coal-fired power stations.

Most used energy is lost to thermal gradients generated by electrical resistance of power equipment and distribution systems. These losses could be removed by development of 'room-temperature superconductor' materials. Such materials are likely to be perfected in the next 50 years and their adoption could reduce the need for electricity generation by at least 70 per cent.

Useful renewables

The above considerations indicate that it is not possible for renewable energy systems to provide significant displacement of fossil fuels at economic cost. The only renewable energy sources which are economic and useful at large scale are geothermal power, managed peat, wave power, hydro-electricity, and some forms of bio-mass. Each of these has some economic uses, and each has particular advantages in its niche. But several uneconomic renewables are being subsidised by governments and this is reducing coal's major market; electricity generation. Several countries are providing these subsidies to 'renewables' because this is said to assist 'sustainable development'. The media in several developed countries are promoting 'sustainable development' as a desirable idea for energy. And, several governments committed themselves to it at the 'Rio Summit' in 1992.

The subsidies can be opposed. They are very expensive and so economically damaging. Worst of all, their objective is the pointless 'sustainable development' which — if achieved — would return mankind to the Stone Age.

Coal will be available at economic cost for at least the next 300 years. In the far distant future it may be possible for some not-yet-developed cheap energy systems to replace fossil fuels. These methods include geothermal energy from the Earth's core, Carson Towers and thermal gradients across the oceanic thermocline. But that is a long time ahead. By then the need for electricity is likely to have been transformed by nuclear fusion power and superconducting systems for electricity transmission and use.

*Richard S. Courtney is Technical Editor, CoalTrans International,
42 Rutherwyke, Epsom, Surrey, KT17 2NB, England,
UK Tel. +44 (0) 181 786 8202,
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