Hydro-Power: The Use of Water as an Alternative Source of Energy

By Charles Simeons

Hydro-Power: The Use of Water as an Alternative Source of Energy deals with the use of water as an alternative source of energy. The principles of the technology involved in the extraction of energy from water for use in some other form are discussed, and some of the projects that are being undertaken in a number of countries are described. Comprised of 12 chapters, this book begins with an overview of global energy consumption and projections for energy demand, along with electricity generation using hydraulic resources and developments in the use of hydroelectric power. The next chapter focuses on the principle of wave power as an energy source, with emphasis on how power can be derived from the slow oscillation of the waves; the economics of wave power; structural design of wave energy converters; and mooring considerations. Subsequent chapters explore national wave power programs in countries such as the United Kingdom, Japan, South Africa, Egypt, Mauritius, Norway, Sweden, and the United States; tidal power and hydrogen; and energy storage and hydroelectric schemes in Europe. The final chapter assesses the environmental impact of hydroelectric power. This monograph will be a useful resource for experts and policymakers in the field of energy as well as those with little knowledge of the potential contribution that water can make to the world's energy needs.

• Language: English
• Publisher: Elsevier Science
• Release date: Apr 24, 2014
• ISBN: 9781483145617

Book preview

trends.

1

Water and the Energy Gap

Publisher Summary

This chapter provides an overview of water and the energy gap. Energy consumption runs in conjunction with the level of the gross domestic product. To reduce the import dependency on conventional energy sources such as oil, natural gas, and coal, there is a critical need for alternative strategies that are economical in the use of nonrenewable resources, have the least impact on the balance of payments, and are least harmful to the environment. This means promoting research and development of such alternative sources of supply as nuclear fusion, solar energy, geothermal energy, or the recovery, reuse, and recycling of all existing energy and materials. Water as a source of energy is a useful, although expensive, contribution. Water available under the right conditions offers considerable potential. Water management projects, however, involve consideration of a number of factors—legal and political, technological, environmental, and social impact. Hydroelectric energy was given a considerable boost with the advent of alternating current and its associated technology, which made transmission of electrical energy economical. The main benefit of hydropower is that it is inflation-proof. As with oil or coal-fired generation, the cost of building will rise, but with water, the fuel remains available as before. As this process continues and the cost of recovery of coal and oil continues to rise, the gap becomes reduced and an increasing number of hydro projects become a reality.

INTRODUCTION

Two thirds of world energy demand is accounted for by the United States, Japan and Western Europe: oil features prominently. Because of this dependence upon oil by these blocks, prices for oil and gas in 1973 were forced up. Consumption then fell.

In the following year published figures for world energy consumption showed it to be running at around 5600 mtoe. By 1975, the United Nations Organisations Statistics, published in 1976, showed that consumption had fallen still further, to 4060 mtoe. This was accounted for in part by conservation measures, but also as a result of industrial stagnation.

Today, the industrial world runs predominantly on oil, followed by natural gas and coal. Waterpower and nuclear energy contribute only a small part to the total demand. Proven reserves of oil and gas, recoverable through the use of current technology, are sufficient to meet world needs until 1990, and possibly beyond, although future discoveries may be sufficient to enable both to be used well beyond that date. Coal reserves are likely to be sufficient for a further hundred years. However, these reserves are not found where they are needed, but scattered world wide as well as being difficult to recover, in many instances. The problems associated with coal recovery are described in Coal: Its role in tomorrow’s technology.

Those in need of oil generally have to import while the countries possessing the reserves usually have very little need – that is until their manufacturing capabilities become developed.

It is not surprising therefore that alternative strategies are being pursued by countries world wide, since nations are interdependent and in need of international collaboration on an unprecedented scale. However, this type of exercise requires adequate backing – finance, labour resources and ingenuity – with a common objective, all brought together in a way rarely experienced except in times of war. The International Energy Agency and the European Community Commission are such vehicles.

While these organisations tend to work in international & EEC spheres, they often co-operate so avoiding duplication of effort.

ENERGY CONSUMPTION AND PROJECTIONS

Experience has shown that energy consumption runs parallel with the level of the Gross Domestic Product. This will place a theoretical strain on the large energy consuming countries. An indication of the trends can be seen from projections made, by the Cavendish Laboratory, Cambridge, England, of energy demand growth rates for world regions employing assumptions for economic growth as the basis - using high and low levels, as shown in Table 1.

TABLE 1

Projected Energy Demand Growth Rates for World Regions

WOCA shown in Table 1 represents the world outside the communist area.

These projects for potential energy supply to 1985 take into account the unexpected surplus capacity for oil production during this period which might well inhibit the growth of alternatives. From 1985 to 2000 a fast expansion is assumed for both coal and nuclear energy although rates of expansion are constrained by the lead times necessary for developing the industries.

By comparison actual figures for the European Communities show in land consumption of primary energy, for each source, to be as listed in Table 2.

TABLE 2

Six Months Primary Energy Consumption Comparison 1977/8 for the Community

It is interesting to note from Table 2 that despite an overall increase in consumption of 1.3%, that derived from hydro-electric and geothermal sources fell by 16.3%. What the figures do not show, however, is that 90% of all coal burned was used in three countries only: the United Kingdom account for 53%, Germany 28% and France 13%. In 1977 coal, a prime candidate for the generation of electricity, was roughly in balance, in terms of internal consumption, in U.K., France and Belgium, while in Germany, despite a fall off in production of some 10% below capacity, a surplus resulted. Overall production within the community was down 4%.

With coal surplus to needs, it is not surprising that further attempts to increase generation of electricity from sources, other than nuclear energy, is not a top priority in Europe.

However, while the Community objective of a 40% dependence upon imports target by 1985 is clearly not attainable, it is now hoped that a 50% figure will be achieved, as shown in Table 3.

TABLE 3

Energy Dependence – European Community

The figure shown for 1985 in Table 3 is made up of the mean of a number of forecasts. By this time, however, the nuclear programme will not be sufficiently advanced to make a marked contribution to total energy needs.

Reduced Import Dependence

Import dependence is a problem facing most of the non communist world. It is not therefore surprising that steps are being taken to reduce consumption and at the same time replace, if only in part, those sources which are non renewable or in restricted supply.

The fundamental need is to develop those alternative strategies which

– are the most economical in the use of non-renewable resources

– have least impact upon the balance of payments

– are least harmful to the environment

This means promoting research and development of alternative sources of supply: nuclear fusion, solar energy, geothermal energy or the recovery, re-use and recycling of every kind of energy and materials. Water as a source of energy is a useful, although expensive, contribution.

Parallel with this objective is a vital need to reduce the rate at which demand for energy is growing and then to reduce the absolute level of demand itself, sector by sector.

Taking the field of transport as an example, it should be remembered that in the United States 25% of all energy used gas in transportation. In the U.S., 96% of all energy used is derived from oil much of which – 60% – is imported. Figures for Europe although lower, stand at 14% and 95% respectively. The solution to making savings in transport may lie in the development of electric vehicles.

The part which water can play in the generation of electricity is probably understood by most people. The use of wave and tidal power receive a considerable amount of publicity and are known too.

However, the production of hydrogen for use as an energy carrier is not so well appreciated or the need for the use of hydrogen in the process of upgrading low Btu gas.

The traditional method of production of electricity by hydrogeneration is more extensive than may appear at first sight, as can be seen from Table 4.

TABLE 4

Electrical Energy 1976 Including Hydro Sources

Figures shown in Table 4 show that the countries with greatest capacity for electricity from hydro-electric sources are:

Clearly water available under the right conditions offers a very considerable potential. The countries listed above obtain their electricity by conventional means. By contrast those with the greatest tidal potential feature fairly low in the ratings at present, namely:

The exception is Canada which already enjoys 60% hydro capacity.

The remaining chapters set out to examine that potential by countries for energy derived from water.

First the technology will be discussed and examined in principle for Wave Power, Tidal, the generation of Hydrogen, Storage and finally conventional hydro-electric. This will be followed by a report upon current development among those countries which responded to the appeal for information.

But first a review of resources, development to date and factors affecting development will be examined.

HYDRAULIC RESOURCES

Some 23% of the world’s electricity is at present derived from Hydraulic Energy. It is a renewable resource; it is reliable and flexible and therefore forms part of any general water resource programme.

For this reason, when a hydroelectric development, of whatever size, is envisaged, the initial planning stage must take into consideration all water resource needs and the way in which they are to be met. Hydroelectric development must not be considered in isolation from the general requirements of the community.

Water supply in many parts of the world is a controlling factor in human and commercial activity. This is being appreciated to an increasing degree in many parts of the world where management and control of river basins are seen as the logical way of using and conserving water resources.

This method of approach has been introduced in Britain where England and Wales are divided into ten authorities, France with six bassins and Belgium with its three areas of control. The United States, because of its size and considerable State Autonomy, looks on partly with envy and partly in a spirit of doubt as to whether river basin control is applicable there. Other countries not plagued with pollution from modern industrial processes, are moving fast to river water quality control including that of harnessing of the power potential.

Tidal Barrages and Wave Power introduce new problems. While wave power is very local in effect and unlikely to cause hazard, other than near shipping lanes, tidal barrages come into quite a different category, making their impact upon a whole range of factors which affect the quality of life. These include:-

– movements of shipping

– tidal patterns and levels

– local nuisance during construction

– erosion of the coast line

Where rivers are shared jointly by bordering states as in the case of the Rhine, running from Switzerland through Germany, skirting France and passing through the Netherlands to the sea, river management is vital. It isn’t surprising therefore that in the early 70’s it was said that as the Rhine passed through Rotterdam, it brought with it annually 1000 tons of mercury, 250 tons of arsenic and 100 tons of cadmium. Joint action is now setting about to put this right – over a period.

Equally, without adequate management a crisis in water supply could equal that which is threatened in energy, the tip of the ice-berg becoming clear from experience in both fields over the past few years.

It is interesting to note that the United Nations Environmental Programme includes the drawing up of a policy for water management in developing countries.

Development should proceed on a broad front, the plan making sure that a full economic return is obtained from any energy contribution which can be made. The benefits may include irrigation and combining navigational needs with power generation such as in the Danube and St. Lawrence developments.

Such projects involve the consideration of a number of factors:

– Legal and political

– Technological

– Environmental

– Social impact

Legal and political considerations

Reference has been made to joint enterprises or international developments, where arrangements have been reached which have been clearly for the mutual benefit of the countries involved.

These co-operative projects include:

Such arrangements show clearly that whatever the legal problems, they can be overcome. Even so, they shouldn’t be underestimated because legal rights to water vary from area to area. Some have property rights under prior established rights as may be found in irrigation areas. Some have riparian rights while others vary from little to no legal framework.

To overcome these, schemes must be well thought out and planned. They must also be seen to meet the needs of the people. This means careful environmental impact studies, benefits and costing.

Technological considerations

Remote control technology has now made small and more isolated plants economic. The technology of the use of water for hydrological generation of electricity is of particular importance. This applies not just to the structure and means of energy conversion, but also the means of conveyance which with modern high voltage transmission systems make the transmission of electricity over long distances, a comparatively simple problem. Work at present being undertaken by the European Communities in their Energy R&D Programme devotes considerable resources to this end. It features prominently too in other national programmes and will contribute considerably to the feasibility of remote hydroelectric projects.

Materials, design and manufacture of equipment also play a major part in the rate of progress. Small hydroelectric generating units as used in wave power experiments, will assist in design, efficiency and standardisation of components resulting in simpler operation.

New ideas will lead to innovations such as the bulb turbine and the straight flow turbine with rim type generator. Further changes stemming from technological advances include the slant-axis turbine generator which is particularly suitable for medium to small size unit installation. A necessary benefit from this concept is a reduction in costs, following from reduced structural demands including excavation. Further progress can be expected as research advances.

Environmental considerations

One of the main impacts upon the local environment is the type of structure or container used for storage. Usually there is a visual change which many oppose, but under certain circumstances it may bring with it unexpected spin off, such as flood prevention. The effects upon wild life and fish must be considered along with possible benefits of irrigation where fresh water is involved.

On the other hand, large areas of water add to the recreational amenities in parts of the world, such as the United States, which otherwise are devoid of water for sporting activities.

Social Aspects

The immediate impact upon the amenities of the area must depend upon the size and nature of the development. A major barrage such as that proposed for the river Severn must involve considerable inconvenience at the time of construction. However, this will disappear once the project is completed, when the main effect will depend upon the changes in the pattern of the tides and the diversion of water from one area to another with all that this entails.

Inland, a large reservoir development could cause the uprooting of a complete village and the loss of acres of farm land.

Smaller activities incorporating wave power will make very little impact other than to bring facilities to the area, not previously available on a permanent basis.

These types of problems indicate the need for very full study of the situation and particularly good communication with the local people.

DEVELOPMENT TO DATE

From early days, since the introduction of the water wheel, the most extensive use of energy has been that derived from water. Changes in design brought increased size and efficiency until the point was reached in the nineteenth century when the main limitation to the mechanical transmission of power was the availability of a site within easy reach of a river or other source of power derived from water. But the introduction of the steam engine made the need less pressing.

Hydroelectric energy was given a considerable boost with the advent of alternating current and its associated technology which made transmission of electrical energy an economic proposition.

One of the early projects before the war came with the Hoover Dam project in the United States involving a 1.3 million Kilowatt system. This was followed in the 1950’s & 1960’s by thermal power generation plants to supplement the vast hydroelectric schemes of the Columbia River Basin in the United States.

Figure 1, shows diagramatically the relationship world wide between total electrical generating capacity relative to that from hydroelectric sources – taken from the United Nations Compilation of World Energy Supplies.

Fig. 1 Relationship total electrical generation to that from hydroelectric sources – world wide

The early years – up to the immediate post war period – shown in Fig. 1, have been interpolated from an assumed nil position in 1920.

World Energy Conference Survey of Energy Resources

The 1976 Conference found there to be a total potential of about 2.2 million megawatts of installed and installable generating capacity from hydraulic sources, with a potential annual energy production of 9.7 million megawatt hours. This is equivalent to 1.97 billion t.o.e. burned to generate the same amount of electricity.

Table 5 indicates the total potential for separate national groupings and the percentage of the total which each represents.

TABLE 5

World Hydraulic Resources in Terms of Total Installed and Potential Capacity – in Megawatts

The output expressed in Table 5 is based upon a 50% capacity factor. These figures compare with the current hydro-electric capacity estimated at around 372,000 megawatts with an annual output of just under 6 million T.J. equivalent to about 16 per cent of the total reported installed and potentially installable projects. By 2020 it is considered that this figure will rise to about 80% according to a former chairman of the U.S. National Committee World Energy Conference.

Figure 2 indicates in diagrammatic form the various stages reached by each grouping.

Fig. 2 Stages of development of world hydraulic resources

Table 6 expresses the same installations under four groupings.

TABLE 6

World Hydraulic Resources by Global Groupings

Table 6 illustrates the same stages of progress as those in Fig. 3, but by global instead of national groupings.

Fig. 3 World hydraulic resources development by groupings

Factors Affecting Development

The cost of this programme to achieve 80% capacity by 2020 has been put at an annual figure of 33 billion U.S. dollars at 1976 prices. This sum is already out of date as a result of the combined effect of inflation and the fall in the dollar over the past three years.

Cost will clearly be a prime factor: this hasn’t been helped by the changes already mentioned involving the problem of raising such vast sums.

However, the comparative cost of different sources of energy are under continual change. Rising costs and changes in demand for resources in short supply, such as oil, natural gas and coal, command a flexibility in approach when economic comparisons with various energy sources are made. As the cost of fuel for power generated by conventional means increases, so the economic advantages of hydroelectric developments increase and become more obvious.

Analysts need to look to forward projections instead of conforming to current trends.

The main benefit of hydro power is that it is inflation proof. As with oil or coal fired generation, the cost of building will rise but with water the fuel remains available as before. As this process continues and the cost of recovery of coal and oil continue to rise, so the gap becomes reduced and an increasing number of hydro projects a reality.

Power from Tidal Barrages and Wave power although operating in countries such as France, requires a very considerable amount of research and money which while appearing to be uneconomic today, could by the early years of the 2000’s offer considerable attraction as oil and gas become more expensive, difficult to recover, or even unavailable.

2

Wave Power

Publisher Summary

This chapter discusses the development of wave power and its generation, conversion, and transmission. Wave power is a form of wind power because waves are caused by wind. Conveniently, the sea forms a very large reservoir or storage center to contain the inertia of water. Over the years, many devices to extract energy, such as converging channels, flaps, floats, and ramps, have been patented, but most of them failed because they did not operate on the principle that the vertical and horizontal components of wave motion must be harnessed together. There are numerous ways in which power can be derived from the slow oscillation of the waves. One such way is by converting the motion of the waves into unidirectional high-pressure water pulses by means of a reversing pump. The safe and efficient way to design wave energy systems demands (1) accurate prediction of wave-induced motions and loads, mooring forces, extreme loads, and likely fatigue damages; (2) evaluation of structural response, which may include destructive testing; and (3) simulated structural designs. Wave power has the benefit of low running costs but the extent to which maintenance involving high labor costs could offset the benefits of free fuel remains to be seen.

Although patents for wave power devices go back as far as the early 19th century, no serious attempt has previously been made to recover energy from this vast potential source.

Wave power is a form of wind power since waves result from the effect of the wind. Conveniently, the sea forms a very large reservoir or storage centre for the inertia of the water to be contained for very limited periods and so reduce the effect of changes in wind speed and between one place and another.

Over the years, many devices have been patented with the object of extracting energy from the waves. These include converging channels, flaps, floats and ramps, but many have failed because they did not operate on the principle that the vertical and horizontal components of wave motion must be harnessed together. This is due to the fact that each particle of water moves at a constant speed in a circle.

The effectiveness of a float or other device depends upon its shape and the manner in which the load is applied. A fixed body will prevent waves from developing behind, the waves being reflected almost totally after impact. However, if free movement is permitted with the waves, the previous reflection no longer occurs, a wave being transmitted behind the float. In neither case will power be extracted. The approaching waves must be absorbed coupled with the absence of any wave behind the device if power is to be recovered.

The principle is illustrated in Fig. 4.

Fig. 4 A rocking boom proposed by Mr. S.H. Salter of the Edinburgh University, Scotland.

For the power to be absorbed efficiently from a wave in a device such as Fig. 4 the float must have a front surface which moves with the water of the oncoming wave and a back surface that does not disturb the water behind. The device illustrated in Fig. 4, is one that meets these criteria. The float rocks about an axis through 0. The lower front surface consists of a cylinder pivoted at 0 merging into a plane which inclines at about 15 degrees to the vertical in still water.

Masuda in Japan have been developing an air pressure ring buoy for small scale use. The principle is shown in Fig. 5.

Fig. 5 Air Pressure Ring Buoy for Small Scale Use

The buoy is divided into a large number of air chambers which are open at the bottom and from which air is displaced rhythimically by the wave action. The air is rectified by flap valves and used to produce power through a low pressure air turbine.

Some idea can be gained from the top diagram in Fig. 5, as to the size, which under North Atlantic conditions might necessitate a ring buoy of up to 300m diameter.

The idea arose when Masuda the inventor was investigating floating breakwaters in Japan. It was found that the wave height could be attenuated, considerably, if the breakwater was in the form of an inverted box and the wave motion inside the box was made to work on air by forcing it in and out of orifices in the top of the box.

Capacity of the Seas as a Source of Energy

The capacity of the seas to act as a source of energy depends upon the winds. Those winds prevailing across the North Atlantic are favourable towards Britain in that they are directed in that direction creating a deep ocean swell.

Long ocean waves are, generally speaking, being created as a result of the wind which blows over the ocean resulting in an almost continuous and inexhaustible source of energy.

The total available energy within U.K. territorial waters has been estimated by the Central Electricity Generating Board to be in excess of double present installed capacity. Fortuitously, the seasonal peak matches electrical demand. During this period it has been estimated that for one per cent of the time seas are too boisterous, while for a similar period, during summer, there are times of calm not conducive to power generation. Safeguards would be necessary both as to excessive force of the sea, which could damage systems, and adequate storage to ensure continuity of supply.

Similar conditions will obviously apply to other parts of the world.

Conversion and Transmission

There are numerous ways in which power can be derived from the slow oscillation of the waves. One means is to consider converting the motion of the waves, into uni-directional high-pressure water pulses by means of a reversing pump. Slater, whose proposal has already been mentioned, has suggested a spline pumping in an arc. Pumped water has a number of attractions which include the facility that it can level out variations almost instantaneously as part of a storage system. On a large scale it should be possible to average out interference between different groups of waves. Storage tanks at sea or using water pumped ashore could be used.

One not inconsiderable problem is the means by which the power generated is to be brought ashore. This could be achieved through the use of a flexible submarine type cable, or alternatively water might be pumped at high pressure from floats at sea with the electricity then being generated on land.

Use at Sea of wave generated electricity, offers considerable possibilities and at the same time removing the need for shore connections. Marker or warning buoys or distress devices, clearly offer considerable scope for this type of exercise, while off-shore hydrogen production is on the cards.

Uranium separation from sea water could offer a number of advantages since pumped sea water could be used in a combined operation. At the same time, if the operation were begun well out to sea and allowed to drift back, power could be generated and uranium separated without the problems associated with the removal of large volumes of water close to the shore.

Recovery of uranium in this fashion could change, very considerably, attitudes towards nuclear thinking and lessen the need for fast-breeder reactors and hence reduce the demand for foolproof methods of security and disposal before too great a distance is covered down the plutonium route.

The Economics of Wave Power

Initial reactions, based upon a simple system, are that costs would be greatly in excess of nuclear costs. A single beam arrangement would be far more expensive, while a series of smaller units probably necessary to provide a broad enough front would be much cheaper. They could be joined together.

Perhaps comfort should be taken from the general experience that mass production reduces costs considerably.

However, work is proceeding on a broad international front because it is realised that although at present it forms only a very secondary line of defence in the energy source battle, wave power can make a very real contribution in the right place at the right time.

Structural Design of Wave Energy Converters

The safe and efficient design of wave energy systems demand a number of responses. These include:

– accurate prediction of:

wave induced motions and loads

mooring forces

extreme loads

likely fatigue damages

– evaluation of structural response which may include destructive testing.

– simulated structural designs – reliability and minimum life expectation.

While computer models, based upon analytical methods for ships and offshore structures, are available for linear analysis of movement and loads in regular and irregular waves, their limitations must not be overlooked. For these reasons much must depend upon the experimental data being obtained in many parts of the world both in experimental tanks and full scale experiments. Countries involved include:

Australia

Canada

China

Egypt

Finland

Japan

Mauritius

Norway

South Africa

Sweden

United Kingdom

United States

U.S.S.R.

Individual programmes of many of these countries will be discussed in Chapter 3.

The preparation of detailed structural designs will require application of established design procedures and data for steel and concrete structures, not very far removed from the requirements for ships, offshore and coastal structures. Some modification for wave energy converters will be needed. Additional tests of an intermediate stage will be