NUCLEAR ELECTRICITY
(Seventh edition, 2003)

CHAPTER 2

ELECTRICITY TODAY AND TOMORROW

2.1 Electricity demand

Electricity demand in an industrial society arises from a number of sources, including:

Industry
- some running on 24-hour basis.
- some working 8-10 hours per weekday.

Commerce
- most working 10-15 hours per weekday.

Public transport
- running during day and evening,

Homes
- heating or cooling mostly during day and evening.
- cooking morning and evening.
- off-peak water and space heating, especially during the night (in some systems).

It is clear from the above that electricity demand fluctuates throughout every 24-hour period as well as through the week, and also seasonally. It also varies from place to place and from country to country depending on the mix of demand, the climate, and other factors. A daily load curve for an electricity system is shown in Figure 2. From this it can be seen that there is a base load of about 60% of the maximum load for a weekday. This load curve is typical for developed countries.

The base-load demand for reliable, continuous supply of large amounts of electricity is the key factor in any system. The main investment of any electric utility is to meet that kind of demand.

As well as the daily and weekly variations in demand there are gradual changes occurring in the pattern of electricity demand from year to year. In projecting demand patterns a decade or more into the future, planners must take note of such factors as:

• The changing pattern of seasonal peak demands; for example as summer air conditioning becomes more common.
• The impact of increased electrification of public transport.
• The possible electrification of private transport, either directly or through the use of hydrogen (produced by electrolysis) in fuel cells. The effect on supply systems of increasing use of solar water heating with electrical boosting during periods of adverse weather.
• The effect of incentives to increase off-peak electricity demands for water and space heating.
• The practical effect of energy conservation measures such as insulation and more energy-efficient building design.
• The role of small-scale renewable energy sources providing electricity when they can.
• Any increase in other dispersed electricity generation.
• Industry needs and how they are changing.
• Improvements in the ability to transmit electricity long distances; e.g. fifty years ago 600 km was the maximum distance for efficient transmission, in the 1960s new technologies enabled transmission over 2000 km, and today it is greater still.

Some of these factors will affect total electricity consumption, while others will influence the relative importance of base-load demand. Production economics will require that as much of the electricity as possible is supplied from base-load generating plant, while allowing scope for occasional input from any renewable generating capacity linked to the system.

FIGURE 3
Load curve of the Victorian electricity system

Load curve of the Victorian electricity system through one winter weekday in June 1996 showing the relative contributions of base, intermediate and peak-load plant duty. The shape of such a curve will vary markedly according to the kind of demand. Here, the peaks reflect domestic demand related to a normal working day, with household hot water systems evident overnight.

Note that the base-load here is about 4100 MWe, and while total capacity must allow for at least 50% more than this, most of the difference can be supplied by large intermediate-load gas-fired plant or by adjusting the output of the base-load plant. The peak loads are typically supplied by hydro and gas turbines. Under the new wholesale electricity market, power stations bid into the market and compete for their energy to be despatched, so the economic factors evident from Figure 3 tend to determine the sources of supply at any particular moment.
Source: VPX.

2.2 Electricity supply

Because of the large fluctuations in demand over the course of the day, it is normal to have several types of power stations broadly categorised as base-load, intermediate-load and peak-load stations.

The base-load stations are usually steam driven and run more or less continuously at near rated power output. Coal and nuclear power are the main energy sources used.

Intermediate-load and peak-load stations must be capable of being brought on line and shut down quickly once or twice daily. A variety of techniques are used for intermediate and peak-load generation, including gas turbines, gas- and oil-fired steam boilers and hydro-electric generation.

Peak-load equipment tends to be characterised by low capital cost, and relatively high fuel cost is not a great problem.

Base-load plant is designed to minimise fuel cost, and the relatively high capital cost can be written off over the large amounts of electricity produced continuously over many years.

Lowest overall power costs to the consumer are obtained when the peak-load increment is very small and a steady base-load utilises all of the available generating capacity fairly constantly. Any practical system has to allow for some of the plant being unserviceable or under maintenance for part of the time. Installed capacity should therefore be about 20% more than maximum load in a system.

Base-load plants in Victoria, for example, make up over half of the system's total generating capacity, and produce more than 85 percent of the total electrical energy (Figure 3). Almost one third of the system's capacity can broadly be classified as intermediate-load plant, supplying power throughout the working day and evening. The balance is peak-load in the strict sense, supplying a short term energy reserve during high loading periods of the day or in emergencies. Victoria is fairly typical of other systems in developed countries in these respects.

The capital cost of peak-load equipment such as gas turbines is about half that of base-load coal-fired plant, and in addition it can be installed much more quickly. However, the fuel cost is relatively high compared with coal in a base-load station, per unit of power generated. Modern combined cycle gas turbine facilities, which have efficiencies substantially greater than that of coal-fired plants, reduce the difference.

Pumped water storage, using available base-load capacity overnight and on weekends, may be developed where topography permits, as an alternative to peak-load thermal power stations*. The capital cost may even be as low as oil- or gas-fired stations, and such installations will have the effect of increasing the extent to which base-load equipment can contribute to total load through the week.

* See also later part of 2.5.

In future the base-load contribution may be increased by using the surplus power in non-peak periods to make hydrogen - see later section.

A further means of increasing the utilisation of base-load plant is enabling it to follow the load to some extent, by varying the output.

As in other industries, there are economies of scale. Larger steam units result in reduced capital cost per kilowatt capacity, especially for base-load equipment. This means that location is sometimes determined as much by the supply of cooling water as by the fuel source. However, large power station units require a large electrical transmission grid and overall generating system to enable them to be operated effectively. hence there are many situations where the economic virtues of small-scale gas-fired generating plants are put forward.

2.3 Fuels for electricity generation today

This book considers principally the question of electricity generation in the major industrialised and densely-populated areas of North America, east Asia and Europe. In these countries electricity generation takes about 40% or more of the primary energy supply. An increasing constraint on choosing the fuel for this is the carbon emissions involved.

Australia is fortunate in having large easily-mined deposits of coal close to the major urban centres in the eastern states. It has been possible to site the major power stations close to those coal deposits and thus eliminate much of the cost and inconvenience of moving large tonnages of a bulky material. Energy losses in electricity transmission are also relatively low.

Canada has ample hydro and/or fossil fuel resources in most areas. However, these resources were largely exploited in the province of Ontario by the mid 1970s. Since that time nuclear power has been the main source of Ontario's electricity.

However, densely populated areas of the world such as Japan and many parts of Europe and North America are not as fortunate in the relative locations of coal supply and electricity demand. Also the high density of population and industrialisation has limited the attractiveness of coal not only from a cost but also an environmental point of view (see chapter 6).

Therefore the desirable criteria for a fuel for base-load electricity generation in highly populated and industrialised nations may be represented thus:

• It should be relatively cheap, giving low-cost power.
• Unless it can be supplied from a source very close to the power station it should ideally be a concentrated source of energy, which can therefore be economically transported and readily stockpiled.
• It should have regard to the scarcity of the resource and alternative valued applications (such as burning directly, or chemical feedstock)..
• Wastes should be manageable, so that they produces a minimum of pollution and environmental disturbance, including long-term global warming effect.
• It must be safe both in routine operation and regarding possible accident scenarios.

National energy strategies will vary according to the indigenous resources of each country, the economics of importing fuels (or electricity), the amount of industrialisation and the security of supply.

An energy-rich country such as the USA has a variety of options. However, even in parts of the USA, transporting large quantities of coal long distances adds significantly to costs. Furthermore, the day when coal is in major demand for conversion to other fuels and materials is probably not far off.

Japan lacks indigenous energy resources and relies almost entirely on imports. Oil was once the most convenient fuel import and the country depended on it for a large proportion of its energy needs, including electricity generation. Coal is increasingly being used for this purpose, but the cost of transport per unit of energy is much greater. Nuclear fuel has the advantage that so little is required and transport costs are negligible. Also, strategic stockpiles can easily be accumulated and variations in the price of the fuel have less impact than with coal or gas.

Figure 4 shows how electricity is produced in some countries and Europe. In all countries the demand for electric power is increasing steadily (mostly 3-4% p.a.). The diagram shows that coal provides a lot of the primary energy input for electricity in the USA and Europe, but much less in Japan and Canada. Europe, USA, Japan and South Korea have about one fifth to one third of their electrical power currently being generated from nuclear reactors.

Of most significance from a world resources perspective is that a substantial amount of the fuel used in each country for generating electricity still consists of increasingly scarce and hence rather precious oil. This is most obvious and acute in Japan and Russia, though both have markedly reduced their dependence on oil for electricity in the last 25 years, and both plan to increase the proportion of their electricity generated from nuclear energy. In Russia's case this is explicitly to maximise gas exports to Europe. Both Russia and UK show a high dependence on gas.

Figure 4.

Figure 5

Source: World Energy Council 1993. Projection to 2020 is Reference Case (total: 13.4 Gtoe, compared with Modified Reference 16.0 Gtoe. High Growth 17.2 Gtoe and Ecologically-driven 11.3 Gtoe cases). See also Figure 1 re total energy mix.

2.4 Provision for Future Base-Load Electricity

In considering the future beyond the year 2010 there are a couple of practical matters which cannot be overlooked. One is the time scale. A commitment today regarding a large base-load generating plant means that plant should be commissioned in five to ten years time. It can then be expected to have an operating life of up to 60 years. Thus today's investment decisions regarding electric plant cannot change the overall pattern of a country's generating system for at least two or three decades - Britain's nuclear investments of the 1950s took two decades to achieve more than a mere ten percent of UK electric power being generated in this way.

Even combined cycle gas turbines (CCGT), which can be put into service in less than two years from date of order, and which are increasingly popular, cannot make a substantial short term change to the overall energy supply situation. If we are considering new technologies not yet commercially engineered, the lead time is longer, perhaps by another two of three decades. It also follows that much of the technology in use today will inevitably be in use for several more decades; it cannot be quickly abandoned.

The other practical matter relates to size. In some things small is appropriate and, given low labour costs, also efficient. In mining fuels and generating electric power however, the economic constraints involved generally dictate that operations and plant be as large as practicable. Where the scale is reduced, the unit costs inexorably increase. With conventional types of plant, large scale installations are inevitable in urbanised and industrialised nations, where large electricity demands are concentrated in small areas of the country.

These practical matters of long lead-time and large-scale installations point to the need for careful assessment of future trends in electricity use to ensure that tomorrow's supply systems will effectively cope with tomorrow's electrical demand.

Furthermore, the technology used must be matched to the task. The big question facing planners is that of selecting the most appropriate means of generating base-load electricity for a particular region at a particular time in the future. What are the options?

Conservation:
One possibility may be to use less energy by practising rigorous conservation, principally through increased energy efficiency in use. This approach can be "retrofitted" to many applications in developed countries, and can be applied to new installations in all countries. If the USA, the UK and Japan could each use less electricity such a strategy might, by itself, eventually eliminate the oil-fired component in two of these countries and markedly reduce it in the third. Energy conservation in general is discussed in section 1.5. However, such conservation has a greater effect on total energy use than on actual electricity, and an increased proportion of electricity in the overall energy mix is often a prime means of conservation.

Oil:
In 2000 oil provided 8% of all electricity, though this is much less than a decade earlier. However, it is still used for base-load power generation in some countries such as Japan (Figure 4). But oil is uniquely important as the source of very portable and energy-rich petroleum products used for mobile transport. Both oil and gas have important uses in the petrochemical industry as feedstock for the manufacture of plastics, fertilisers and pharmaceutical products. Burning oil for base-load electricity generation where other fuels are economically available is questionable. In Australia and Canada oil is used for power generation in areas remote from natural gas resources and coalfields, in relatively small installations.

Natural Gas:
Gas today plays a major and steadily-increasing role in power generation (17.3% of world electricity in 2000). While gas prices have been low and gas turbines relatively cheap and quickly built, it has been a most attractive fuel. It has the distinction of giving rise to less carbon dioxide than coal, and hence is favoured by some to displace coal for base-load power.

Natural gas is a superbly useful resource. It can be drawn from the earth, easily and economically transported via large pipe lines, then cheaply reticulated to small-scale points of use where it can be used as a fuel very efficiently (up to 90% at end use, allowing for flue losses). It can be liquefied for shipping overseas (for example as LNG to Japan and Korea). It is also a valuable chemical feedstock for manufacturing.

This means that large-scale use of it for generating electricity, where less versatile alternatives are readily available, raises ethical questions, particularly relating to intergenerational equity. In short, our grandchildren may later wish that the current "dash for gas" had been more restrained, and had left more gas for them. There is in any case the question of whether natural gas's great value as a direct fuel means that its price is likely to rise in the medium-term future to the extent that it will be much less competitive for base-load electricity.

Coal:
Of the fuels for base-load electricity generation, coal is at present the most important

Coal plays the major role in most countries and has done so for many years, currently providing 39% of the world's electricity. Modern coal-fired power stations are more efficient than in the past, and at extra cost some of the environmental effects of burning high-sulphur coals can be eliminated, even if the global warming effect due to the production of massive amounts of carbon dioxide cannot (see Chapter 6).

Coal from large open cut mines is fairly cheaply obtained, but the costs of transport over long distances can make it less attractive than alternatives. If large quantities of coal are mined in one locality and shipped across a continent or overseas (for example, from Australia or Canada to Japan or Europe), its handling and transport imposes costs and involves the consumption of further energy.

Also, like oil and gas, coal has important uses other than as a fuel. Carbon, even in steaming coal, is needed in large quantities for metal smelting, for future conversion to gas and liquid fuels, and for other purposes. Although reserves are large, conservation will become increasingly important.

Uranium:
The only other fuel which is a present option for base-load electricity is uranium. While large amounts of ore may be mined and treated, two or three 200-litre drums of uranium oxide (U₃0₈) concentrate leaving the mine contain enough energy to keep large cities supplied with power for a day, so it is relatively very portable. It also has some environmental advantages (see Chapter 6). Its detractors sometimes emphasise that compared with coal, nuclear power still has too many unsolved problems. However, it is now almost fifty years since the first commercial reactor came on line, and sixty years since nuclear fission (see Chapter 3) was first controlled.

In that time some 10,500 reactor-years of operating experience have been acquired with commercial reactors, and about the same from similar (but smaller) reactors in naval use.

Today there are some 440 nuclear power reactors in operation in 31 countries, including several developing nations. They provide about 16% of the world's total electricity.

More nuclear power stations are actively under construction. Electricity authorities in many countries are satisfied with the reliability, safety and economic performance of nuclear power relative to coal or oil (see also 2.6 and Chapter 6). Thus, in many countries at least one third of their electricity is generated by nuclear power. France generates three quarters of its electricity from nuclear power and is the world's largest electricity exporter. Table 5 gives an indication of the different kinds of nuclear power reactors currently being used for electricity generation.

CANDU nuclear power plants offer greater uranium resource utilisation than other available thermal nuclear reactors, and can operate on a variety of low fissile content fuels including spent fuel from other kinds of reactors. In the longer term fast neutron reactors (see 4.4) have the potential for vastly increasing the electric power yield from known uranium reserves.

Apart from military weapons and naval propulsion, uranium has no significant uses other than for electricity generation and for making medical and industrial isotopes. At least 95% of the world's uranium production today goes into electricity generation (the balance to naval propulsion and isotope production).

The potential of nuclear power for electricity generation, using uranium as a fuel, is principally applicable to developed nations which have large blocks of electricity demand. Today's nuclear power stations tend to be built in sizes from 500 megawatts electrical (MWe) to about 1300 MWe, anything smaller currently being less attractive economically. However, there are some developing nations which have moderate-sized electricity production and distribution systems and/or the need for co-generating (for example, electricity and potable water production). These are able economically to use reactors in the 100 MWe size range where expensive oil-fired generation is the main alternative.

Nuclear Fusion:
Commercial nuclear fusion is still only a future hope. As well as looking for ways to harness incident sunlight, people have for a long time dreamed of taming the process which generates that light and heat - bringing the sun right down to earth. The process concerned is called nuclear fusion (as distinct from fission, see Chapter 3). The favoured method for achieving controlled fusion involves joining the nuclei of deuterium and tritium atoms (heavy isotopes of hydrogen) together at very high temperatures - about 100 million degrees Celsius. No method of sustaining such temperatures under stable conditions has yet been demonstrated. However, research continues, particularly in USA, Japan, Europe and Russia, and perhaps some time in the next half century heat from fusion will be harnessed to generate electricity. Fusion technology would be best suited to large-scale base-load applications such as supplying cities and industrial regions.

The deuterium fuel is relatively abundant in sea water, but tritium is derived either from lithium, or produced in heavy water-moderated reactors. Almost limitless energy would be available if the deuterium-deuterium reaction could be achieved, but this requires much higher temperatures than the deuterium-tritium process. Controlled fusion of ordinary hydrogen nuclei as occurs in the sun seems unlikely ever to be achieved on earth, as the conditions required are even more extreme. The big advantage of all these reactions is that only small quantities of radioactive wastes are expected. Disadvantages include projected high cost, the high radioactivity created in structural components of the plant, the cost of producing tritium gas and the hazard of handling it.

See also paper on Nuclear Fusion Power.

2.5 Renewable energy sources

Technology to utilise the forces of nature for doing work to supply human needs is as old as the first sailing ship. There is a fundamental attractiveness about harnessing such forces in an age which is very conscious of the environmental effects of burning fossil fuels.

Sun, wind, waves, rivers, tides and the heat from radioactive decay in the earth's mantle as well as biomass are all abundant and ongoing, hence the term "renewables". Only one, the power of falling water in rivers, has been significantly tapped for electricity so far, though wind may one day catch up. Solar energyıs main human application has been in agriculture and forestry, via photosynthesis, and increasingly it is harnessed for heat. Biomass (eg sugar cane residue) is burned where it can be utilised. The others are little used today.

Turning to the use of renewable energy sources for electricity, there are immediate challenges in actually harnessing them. Apart from photovoltaic (PV) systems, the question is how to make them turn dynamos to generate the electricity. If it is heat which is harnessed, this is via a steam generating system.

If the fundamental opportunity of renewables is their abundance and relatively widespread occurrence, the fundamental problem, especially for electricity supply, is their variable and diffuse nature*.

* The exception is geothermal, which is not widely accessible.

This means either that there must be reliable duplicate sources of electricity, or some means of electricity storage on a large scale. Apart from pumped-storage hydro systems (see p4), no such means exist at present and nor are any in sight.

For a stand-alone system the energy storage problem remains paramount. If linking to a grid, the question of duplicate sources arises. For large-scale and especially base-load electricity generation there is little scope for harnessing the sun.

Solar energy:
"Solar not nuclear" has been a catch-cry of both anti-nuclear environmental groups and many technological optimists, particularly as advances in direct solar heating continued to be made. Certainly we can expect to see more roof area occupied by some kind of solar collectors in the future, as their price comes down and we adapt our energy usage to utilise better what is available from this source.

However, for electricity generation solar power has limited potential, as it is too diffuse* and too intermittent. First, solar input is interrupted by night and by cloud cover, which means that solar electric generation inevitably has a low capacity factor, typically less than 15%. Also, there is a low intensity of incoming radiation and converting this to high-grade electricity is still relatively inefficient (12 - 16 percent), though it has been the subject of much research over several decades. * In Australia on a sunny day up to 1 kW/m² falls on a surface maintained at right angles to the sun's rays. In Canada much less than this is received through much of the year, for instance in winter most of Canada averages less than 1 kWh per day (on horizontal surface).

Two methods of converting the sun's radiant energy to electricity are the focus of attention. The better known method utilises sunlight acting on photovoltaic cells to produce electricity. Solar photovoltaic (PV) has application on satellites and for certain earthbound signalling and communication equipment, such as remote area telecommunications equipment in Australia. Sales of solar PV modules are increasing strongly as their efficiency increases and price falls (now c $4000/kW). But the cost per unit of electricity still rules out ordinary use.

For a stand-alone system some means must be employed to store the collected energy during hours of darkness or cloud - either as electricity in batteries, or in some other form such as hydrogen (produced by electrolysis of water). In either case, an extra stage of energy conversion is involved with consequent energy losses, thus lowering overall net efficiency, and greatly increasing capital costs.

Several experimental PV power plants mostly of 300 - 500 kW capacity are connected to electricity grids in Europe and USA. Japan has 150 MWe installed. A large solar PV plant was planned for Crete. Research continues into ways to make the actual solar collecting cells less expensive and more efficient. Other major research is investigating economic ways to store the energy which is collected from the sunıs rays during the day.

A solar thermal power plant has a system of mirrors to concentrate the sunlight on to an absorber, the energy then being used to drive turbines. The concentrator is usually a parabolic mirror trough oriented north-south, which tracks the sunıs path through the day. The absorber is located at the focal point and converts the solar radiation to heat (about 400°C) which is transferred into a fluid such as synthetic oil. The fluid drives a conventional turbine and generator. Several such installations in modules of 80 MW are now operating. Each module requires about 50 hectares of land and needs very precise engineering and control. These plants are supplemented by a gas-fired boiler which generates about a quarter of the overall power output and keeps them warm overnight. Over 350 MWe capacity worldwide has supplied about 80% of the total solar electricity so far.

The main role of solar energy in the future will be that of direct heating. Much of our energy need is for heat below 60°C - eg. in hot water systems. A lot more, particularly in industry, is for heat in the range 60 - 110°C. Together these may account for a significant proportion of primary energy use in industrialised nations. The first need can readily be supplied by solar power much of the time in some places, and the second application commercially is probably not far off. Such uses will diminish slightly electricity demand and the consumption of fossil fuels, particularly if coupled with energy conservation measures such as insulation.

With adequate insulation, heat pumps utilising the conventional refrigeration cycle can be used to warm and cool buildings, with very little energy input other than from the sun. Eventually, up to ten percent of total primary energy in industrialised countries may be supplied by direct solar thermal techniques, and to some extent this will substitute for base-load electrical energy.

Wind energy:
Small-scale wind turbines have been used for household electricity generation in conjunction with battery storage over many decades in remote areas. Generator units of up to 2 MWe are now functioning in several countries. The power output is a function of the cube of the wind speed, so such turbines require a wind in the range 3 to 25 metres/second (11 - 90 km/hr). In practice relatively few areas have significant prevailing winds. Like solar, wind power requires alternative power sources to cope with calmer periods.

However, there are now many thousands of wind turbines operating in various parts of the world, with a total capacity of over 25,000 MWe. This has been the most rapidly-growing means of electricity generation at the turn of the century and provides a valuable complement to large-scale base-load power stations. Denmark gets over 10% of its electricity from wind. The most economical and practical size of commercial wind turbines is now up to 2 MWe, grouped into wind farms up to 200 MWe. Most turbines operate at about 25% load factor over the course of a year, but some reach 30%.

Rivers:
Hydro-electric power, using the potential energy of rivers, now supplies 17.5% of world electricity (60% in Canada, 9% in Australia). Apart from a few countries with an abundance of it, hydro capacity is normally applied to peak-load demand, because it is so readily stopped and started. It is not a major option for the future in the developed countries because most major sites in these countries having potential for harnessing gravity in this way are either being exploited already or are unavailable for other reasons such as environmental considerations.

The chief advantage of hydro systems is their capacity to handle seasonal (as well as daily) high peak loads. In practice the utilisation of stored water is sometimes complicated by demands for irrigation which may occur out of phase with peak electrical demands.

Geothermal:
Where hot underground steam can be tapped and brought to the surface it may be used to generate electricity. Such geothermal sources have potential in certain parts of the world such as New Zealand, USA, Philippines and Italy. Some 6000 MWe of capacity is operating. There are also prospects in certain other areas for pumping water underground to very hot regions of the earthıs crust and using the steam thus produced for electricity generation.

Tides:
Harnessing the tides in a bay or estuary has been achieved in France (since 1966) and Russia, and could be achieved in certain other areas where there is a large tidal range. The trapped water can be used to turn turbines as it is released through the tidal barrage in either direction. Worldwide this technology appears to have little potential, largely due to environmental constraints.

However, placing free-standing turbines in major coastal tidal streams appears to have much greater potential.

Waves:
Harnessing power from wave motion is a possibility which might yield much more energy than tides. The feasibility of this has been investigated, particularly in the UK. Generators either coupled to floating devices or turned by air displaced by waves in a hollow concrete structure would produce electricity for delivery to shore. Numerous practical problems have frustrated progress.

Relating renewables to base-load electricity demand:
Sun, wind, tides and waves cannot be controlled to provide directly either continuous base-load power, or peak-load power when it is needed.

For the reasons discussed, they cannot be controlled to provide directly either continuous base-load power, or peak-load power when it is needed. In practical terms they are therefore limited to some 10-20% of the capacity of an electricity grid, and cannot directly be applied as economic substitutes for coal or nuclear power, however important they may become in particular areas with favourable conditions. Nevertheless, such technologies will to some extent contribute to the worldıs energy future, even if they are unsuitable for carrying the main burden of supply.

If there were some way that large amounts of electricity from intermittent producers such as solar and wind could be stored efficiently, the contribution of these technologies to supplying base-load energy demand would be much greater. Already in some places pumped storage is used to even out the daily generating load by pumping water to a high storage dam during off-peak hours and weekends, using the excess base-load capacity from coal or nuclear sources. During peak hours this water can be used for hydro-electric generation. Relatively few places have scope for pumped storage dams close to where the power is needed, and overall efficiency is low. Means of storing large amounts of electricity as such in giant batteries or by other means have not been developed.

There is some scope for reversing the whole way we look at power supply, in its 24-hour, 7-day cycle, using peak load equipment simply to meet the daily peaks. Todayıs peak-load equipment could be used to some extent to provide infill capacity in a system relying heavily on renewables. The peak capacity would complement large-scale solar thermal and wind generation, providing power when they were unable to. Improved ability to predict the intermittent availability of wind enables better use of this resource. In Germany it is now possible to predict wind generation output with 90% certainty 24 hours ahead. This means that it is possible to deploy other plant more effectively so that the economic value of that wind contribution is greatly increased.

However, any substantial use of solar or wind for electricity in a grid means that there must be allowance for 100% back-up with hydro or fossil fuel capacity. This gives rise to very high generating costs by present standards, but in some places it may be the shape of the future.

The Hydrogen Economy
Hydrogen is widely seen as a possible fuel for transport, if certain problems can be overcome economically. It may be used in conventional internal combustion engines, or in fuel cells which convert chemical energy directly to electricity without normal burning.

Making hydrogen requires either reforming natural gas (methane) with steam, or the electrolysis of water. The former process has carbon dioxide as a by-product, which exacerbates (or at least does not improve) greenhouse gas emissions relative to present technology. With electrolysis, the greenhouse burden depends on the source of the power, and both intermittent renewables and nuclear energy are considered here.

With intermittent renewables such as solar and wind, matching the output to grid demand is very difficult, and beyond about 20% of the total supply, apparently impossible. But if these sources are used for electricity to make hydrogen, then they can be utilised fully whenever they are available, opportunistically. Broadly speaking it does not matter when they cut in or out, the hydrogen is simply stored and used as required.

A quite different rationale applies to using nuclear energy for hydrogen. Here the plant would be run continuously at full capacity, with perhaps all the output being supplied to the grid in peak periods and any not needed to meet civil demand being used to make hydrogen at other times. This would mean maximum efficiency for the nuclear power plants, and that hydrogen was made opportunistically when it suited the grid manager.

About 50 kWh is required to produce a kilogram of hydrogen by electrolysis, so the cost of the electricity clearly is crucial.

See also paper on The Hydrogen Economy.

Environmental aspects of renewables:
Renewable energy sources have a completely different set of environmental costs and benefits to fossil fuel or nuclear generating capacity. On the positive side they emit no carbon dioxide or other air pollutants (beyond some decay products from new hydro-electric reservoirs), but because they are harnessing relatively low-intensity energy, their Œfootprintı - the area taken up by them - is necessarily much larger.

Whether a country such as Australia could accept the environmental impact of another Snowy Mountains hydro scheme (providing some 3.5% of the countryıs electricity plus irrigation) is doubtful. Whether large areas near cities dedicated to solar collectors will be acceptable, if such proposals are ever made, remains to be seen. Beyond utilizing roofs, 1000 MWe of solar capacity would require at least 20 square kilometres of collectors, shading a lot of country.

In Europe, wind turbines have not endeared themselves to neighbours on aesthetic, noise or nature conservation grounds, and this has arrested their deployment in UK. At the same time, European non-fossil fuel obligations have led the establishment of major offshore wind forms and the prospect of more.

However, much environmental impact can be reduced. Fixed solar collectors can double as noise barriers along highways, roof-tops are available already, and there are places where wind turbines would not obtrude unduly.

2.6 Coal and Uranium Compared

The only major fuel options for large-scale energy conversion to base-load electricity over the next several decades are coal and uranium.

Gas is an option in some places in the short term, but its great value as a direct fuel and the likelihood of significant price increases in the long term put the spotlight back on to coal and uranium. Choices between these alternatives will probably continue to depend principally on the final cost of electric power (including environmental costs), which varies significantly from site to site.

Some general comparisons between coal and uranium as the principal fuels for base-load electricity generation are discussed in this section. Other comparisons which are principally environmental or related to health, ie external costs, are discussed in more detail in Chapter 6.

Different quantities of materials are involved with energy conversion to electricity, starting with coal and uranium. In either case the amount of electricity considered is 8000 kWh, a conservative estimate of the amount required by one person in a developed country for one year.*

* The average consumption in industrialised countries is about 9000 kWh/yr (World Energy Council, 2000). Australian consumption is 9020 kWh /person /year, or perhaps about 10% less after allowing for energy in aluminium and similar exports. Canadian consumption is 15,635 kWh/person/year, EU consumption is 5913 kWh/person/year and in the USA it is 12,640 kWh /person /year (OECD/IEA Electricity Information 2002).

Figure 6: Fuel & waste comparison

Using uranium as the fuel:
Between 30 kg and 70 kg of uranium ore from a typical Australian or Canadian mine is needed to produce a handful (230 grams) of uranium oxide concentrate. The uranium in this concentrate, is referred to as "natural uranium" and contains about 0.7% U-235, the fissile isotope of uranium. Natural uranium is used to fuel CANDU reactors in Canada and around the world. In countries operating light water reactors (PWRs and BWRs) the natural uranium is enriched in its U-235 isotope to yield about 30 grams of enriched uranium fuel (3.5% U-235, see 4.2).

Irradiated fuel from CANDU reactors contains very little fissile material and is treated as waste. Irradiated fuel from light water reactors does contain a significant quantity of fissile material and, in some countries, it is reprocessed to recover this. When light water reactor fuel is reprocessed, about 20 ml of liquid high-level waste remains. This then can be incorporated into less than one cubic centimetre (6 g) of pyrex glass - about the size of a large coin, and is highly radioactive. Other wastes are also produced, but they are of much less significance - see 5.1.

Using coal as the fuel:
About three tonnes of high quality black coal (or 3.5 t of average black coal or 9 t of brown coal) can be fed into a power station to generate the same amount of electricity. This leaves a certain amount of ash, varying from a couple of barrow loads to half a tonne, depending on the particular coal used. Eight tonnes of carbon dioxide, which at atmospheric temperature and pressure would fill three full-sized Olympic pools (50m x 15m x 2m), is produced. Depending on the coal, some sulfur dioxide (SO₂) is also produced. A common type of US coal might contain 2-3 percent sulfur, in which case possibly a hundred kilograms of sulfur dioxide would require costly removal, or would add to the acid rain problems well known in the northern hemisphere. The environmental effects of these gaseous by-products of coal-fired electricity generation are considered in more detail in 6.1 and 6.2, and the costs of SO₂ removal are mentioned below. (Australian and Canadian coal generally contains less than one percent sulfur).

Years ago, most coal-fired power plants emitted more radioactivity than any nuclear plants of similar size! This was due to trace quantities of radioactive materials (eg up to 17ppm U+Th in Australia and Canada) in the coal. With modern equipment this radioactivity is mostly retained with the fly ash and is buried with it.

2.7 Economic factors

As well as comparing the quantities of fuel and wastes involved, the relative costs of the two types of generating systems are important in considering options. This section focuses on the internal costs - those which need to be actually paid in the course of building and operating the plants. External costs are those which are actually incurred in relation to health and the environment but not paid directly by the electricity producer or consumer. These are large for fossil fuels, especially coal, and are considered further in chapter 6. Equivalent costs for nuclear energy, notably waste management & disposal and decommissioning old reactors, are internalised and paid for by the consumers of their electricity.

A nuclear power station costs a lot more than a gas-fired station and somewhat more than a coal-fired station to build. But the nuclear fuel, including enrichment if needed, costs much less than oil, gas or coal. Hence the overall expected cost for energy conversion to electricity can come out much the same for nuclear as for coal-fired plants. Table 4 quotes some comparisons for the projected costs of electricity compiled by the OECD and Figure 7 shows the actual costs over more than a decade in the USA, while Figure 8 shows the components of electricity cost for different means of generating it.

There are a number of US nuclear plants where capital costs blew out during construction and hence where any normal calculation of generating cost shows it to be very high. However, closing such plants would help neither owners nor customers, and in any case the criterion for running them is the cost of actual operation (O & M plus fuel - see Figure 7). On this basis they compare favourably with coal and are cheaper than gas. Fourteen of these older US reactors changed hands over 1998-2002 and the escalating prices indicated the favourable economics involved. Regarding investment in new capacity, the capital costs are a major factor, and these are included in Table 4 and Figure 8.

In an earlier version of Table 4, OECD figures for plants starting operation in 2000 showed the importance of having coal near its point of use and low in sulfur. Costs in the north eastern United States distinctly favoured nuclear, costs in the midwest marginally favoured nuclear, and in the west, coal was cheaper. Today, projected low gas prices are the main reason for nuclear being uncompetitive there. Having the location of electricity demand well removed from sources of cheap coal is the main reason for the steadily increasing use of nuclear power in many countries as compared with coal. The major uncertainties in all the figures of Table 4 are the projected prices of coal and gas and the capital costs of new nuclear plants.

TABLE 4.
Some comparative electricity generating cost projections for year 2005-2010

	nuclear	coal	gas
France	3.22	4.64	4.74
Russia	2.69	4.63	3.54
Japan	5.75	5.58	7.91
Korea	3.07	3.44	4.25
Spain	4.10	4.22	4.79
USA	3.33	2.48	2.33 - 2.71
Canada	2.47-2.96	2.92	3.00
China	2.54-3.08	3.18	-

US 1997 cents/kWh, Discount rate 5% for nuclear & coal, 30 year lifetime, 75% load factor.
Source: OECD/IEA NEA 1998, Projected Costs of Generating Electricity.

Actual electricity production costs in the USA (excluding capital) are shown in Figure 7. These are average figures including a lot of old coal and nuclear plant, and should be read with Figure 8.

Figure 7.

Source: NEI
Note: The above data refer to fuel plus operation and maintenance (O & M) costs only, they exclude capital since this varies greatly among utilities and states. Figures in Table 4 include capital, as does Figure 8.

Figure 8.
Components of electricity costs

For different fuel costs (fossil fuels) or lead time (nuclear plants). Assumes 5% discount rate, 30 year life and 70% load factor.
Note: The key factor for fossil fuels is the high or low cost of fuels (top portion of bars), whereas nuclear power has a low proportion of fuel cost in total electricity cost and the key factor is the short or long lead time in planning and construction, hence investment cost (bottom portion of bars). Increasing the load factor thus benefits nuclear more than coal, and both these more than oil or gas. Source: OECD 1992, Electricity Supply in OECD, annex 9.

An important aspect of nuclear electricity is its relationship with a country's international balance of payments position. As noted above and in Figure 8, nuclear power is very capital-intensive compared with systems based on fossil fuels, where the fuel costs are relatively much more significant. Therefore where the choice for a country such as Japan or France lies between importing large quantities of fuel or spending a lot of capital at home, the decision may well be taken simply on foreign exchange grounds. This was a factor in Canada, where fossil fuel supplies are located in the west of the country. Eastern Canada, in the absence of nuclear, would rely heavily on imported coal. Development of nuclear power in such situations has the effect of stimulating local industries which build the plant and at the same time of minimising long-term commitments to buying fuels abroad. Overseas purchasing commitments for the life of a new coal-fired plant in Japan, for example, would be subject to price rises and could become a more serious drain on foreign currency reserves than with less costly uranium.

Uranium has the advantage of being a highly concentrated source of energy which is therefore easily and cheaply transportable, the quantities needed being very much less than for coal or oil. One kilogram of natural uranium yields about twenty thousand times as much energy as the same amount of coal (see Table 3). In addition the fuel cost contribution to the overall cost of electricity produced is relatively small, which means that even a large fuel price escalation will have relatively little effect.*

* A doubling of the 1997 U₃O₈ price would increase the fuel cost for a light water reactor by 30% and the electricity cost by about 7%.

However as the long term global environmental consequences of consuming fossil fuels, especially coal, create additional concern, the environmental advantages of nuclear power are also receiving more attention (see 6.1).

Assigning carbon values, or imposing carbon taxes, on fossil fuel electricity generation changes the economic situation relative to nuclear energy. For instance, carbon values of $37 per tonne for typical coal, or $29 per tonne for brown coal, will increase the electricity cost from those sources by one cent per kilowatt hour while leaving nuclear electricity costs unaffected.

Energy cost

It has already been noted that the capital cost of a nuclear power plant is higher than that of a coal plant. The "energy cost" may also be higher, that is, the amount of energy invested in materials and fuel preparation. This is particularly the case for light water reactors where the energy required to enrich the fuel is substantial. The energy capital used for construction and initial fuel charge of a light water reactor is equivalent to about 1.5 percent of a reactor's lifetime output, and fuelling it accounts for less than one percent of its output (or up to 4% in a worst case scenario, using least-efficient diffusion enrichment, see section 3.4).

Basis: 1000 MWe PWR, 70% capacity after commercial operation. (source: ERDA 76/1)
NB. in the light of current data (see UIC briefing paper # 57) this is unduly conservative, and the energy payback time is about six months rather than the 15 months here.

Although coal and uranium appear to compete for base-load electricity generation, most developed nations fortunate enough to have the option see a role for both.

As a general rule countries without cheap coal or plentiful gas tend to favour nuclear power as the lower cost option. In a few countries (such as Australia, where coal reserves and production potential far outweigh domestic needs) the use of coal for electricity generation is favoured over nuclear. However, in a world perspective, the need for both is evident, and as electricity demand increases along with concern regarding possible global warming, a corresponding increase in the priority of nuclear power for base-load electricity seems inevitable.

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