Apart from using existing fossil fuels and fuel substitutes made from organic matter we have the option of obtaining some of our power requirements from natural energy sources. The chief natural energy sources are wind, water and sunshine or solar energy. These power sources have been with mankind since the dawn of time. They are both free and plentiful. Unlike the fossil fuels, they are not a finite commodity. Our forefathers used them to some extent, particularly for vessel propulsion, but in our greed and our haste we have maximized utilization of the irreplaceable fossil fuels, and have in this century, largely ignored the vast potential offered us by benign nature1.
Wind power has been used for milleniums to propel vessels and still is so used today though chiefly for pleasure craft. Many fishing boats of the small scale artisanal sector are still powered by wind however, and in S.E. Asia these craft are numbered in the hundreds of thousands. Indonesia alone has about a quarter million sail-powered fishing vessels. Perhaps if we calculated propulsion at around 2 hp per sailing vessel, we might find that the total wind energy use of the fishing fleets of the Indo-Pacific is much greater than the total mechanical energy used, even today.
1 Hayes, D. Energy for Development: Third World Options. Worldwatch Paper 15. U.S.A., December 1977.
Without any fuel shortage at all it would be impossible even at the most optimistic growth rates, to mechanize all the fishing craft in the Indo-Pacific. Now that fossil fuels are scarce and likely to escalate rapidly in price, the possibilities of further mechanization are even more remote, unless substantial amounts of biofuels are produced. So we might well consider using wind power to maximum advantage.
Some suggestions for improved use of wind power on sail and auxiliary sail-powered vessels are provided in the section on boat design.
Wind power can also be used on land to drive machinery. The two applications of most interest to fishing ports or fishing villages are the use of windmills to generate electricity and to drive water pumps. Windmills have been used for centuries to grind corn and to pump water. They declined in use the past 50 years although many lighter higher speed units were installed in farms particularly in the Americas.
In very recent years a resurgence of interest in windmill technology has produced a whole new range of designs to maximize windmill efficiency. Generally speaking these designs fall into two categories:
Low-cost and simple slow speed units for village use, mostly for pumping water; and
Ultra-efficient high speed designs chiefly for electricity generation.
The low-cost units mostly utilize cloth sails, usually four, six or eight of which are attached to bamboo or metal rods braced with stays and guys of rope or wire. Using hardwood bearings and steel frame supports such windmills cost around $600 to $800 each fully installed and fitted with pumps and piping. They can pump from 1,000 to 4,000 liters of water per hour to a 3-meter head in wind speeds of 10 to 25 kilometers per hour1.
Another type of low-cost windmill is the Savonius rotor invented by a Finnish engineer in the 1920's. It is made by cutting oil drums in half, down the middle, and welding them together slightly overlapped to form an S-shaped vertical axis rotor. This type of windmill does not have to be oriented towards the wind direction. It is mounted on a rugby goalpost shaped frame which is stayed to the ground. In winds of 10 to 20 kph the Savonius rotor can deliver from 400 to 2,000 liters per hour to a head of 3 meters. Including the cost of materials, pump, welding and labour, it is probably slightly cheaper than the sail-powered unit2.
1 Fraenkel, P. Food from Windmills. London, Intermediate Technology Group, 1976.
2 Brace Research Institute. How to Construct a Cheap Wind Machine for Pumping Water. Quebec, McGill Univ., 1979.
LOW COST WINDMILLS
For pumping water
More efficient manufactured windmills for producing electrical power are available in a variety of designs. Most of them are designed to operate in all weathers. At present they cost around $1,000 per kilowatt installed power capacity, and are available in sizes ranging from 0.5 to 30.0 kilowatts. They use propeller blades rather than windmill vanes as such. The largest windmill generator to date is one constructed by Tvindskolen in Jutland, Denmark which drives a 2,000 KW generator. 500 KW of this power is used as ‘clean’ electricity, and the balance is used to heat water1.
Two problems involved in the design of these windmills are relating blade design to windspeed, and developing efficient low-speed alternators. There have been several breakthroughs in technology and design by groups working on those problems and we may soon see even more efficient and cheaper units on the market. For fishing stations in remote areas with reasonably steady winds, they offer a modest but regular supply of low-cost electricity2.
Even at current prices the wind-powered generator compares favourably with the diesel-powered generator. The following rough calculation gives an indication of costs over a 5-year period.
|Diesel Generator||Wind Generator|
|Output||10–20 KW||10–20 KW|
|Cost, complete and installed||$ 9,000||$ 23,000|
|Diesel fuel *||45,000||-|
|Maintenance at $1,000 per year||5,000||5,000|
|Cost over 5 years||59,000||28,000|
|Power cost per kw/hr||$0.20 to $0.40||$0.10 to $0.20|
* At $0.375 per liter for 5 years at 8 liters per hour, 3,000 hoursa year; assuming an increase over the 5 years from $0.175 to $0.575per liter, i.e. less than the percentage increases over the lastfive years. At the time of writing, diesel fuel is already cost-ing $0.225 in some countries.
1 Hinrichsen, D. in Natural Energy and Living, No. 4. London, NEA, 1978.
2 McGuigan, D. Small Scale Wind Power. Dorchester, Prism Press, 1978.
There are three water power sources that may be applicable to fishing ports and fishing villages. Water movement can be converted into mechanical or electrical power from rivers, tidal streams and wave action. River and waterfall mills are an old and long established type of hydro-power. The modern hydro-electric power station has developed from that. Some of these dams are colossal in size and may cause widespread ecological disruption, but many small dams have little interference with nature. Certain countries like Scotland have been able to effect rural electrification largely by small hydro-electric installations. Some of these units drive generators as small as 10 KW on a 40-meter head. The Chinese have in recent years installed 60,000 water turbines with an average output of 35 KW per station. This amounts to over 2 million kilowatts of power, all from small rivers and streams.
For even smaller power requirements, a Scottish firm has developed a low-cost turbine which will develop 1.5 KW given a 5-meter head. The design is so simple the turbine could be installed by any competent handyman1.
1 Perlite Water Turbine, in How to Use Natural Energy. London, NEA, 1978.
To determine the potential of any stream for electricity generation one needs to know the head or vertical height of the fall (which may extend over a longer horizontal distance) and the flow or velocity of the stream. The formula then is:
where H = head in meters; and
Q = flow in liters per second
The answer obtained should be reduced by an efficiency factor of 20 per cent for turbines and 35 per cent for water wheels. A further power loss might be encountered with the belts or gear box 1.
The new low cost Perlite 1.5 kW water turbine
Tidal power has long been regarded as a potential source of tremendous power but as yet in only very few cases have we been able to tap this power and that at great capital cost. There are many straits or firths where tidal streams of over 5 knots are found close to shore. These could be harnessed to drive massive generators but for small scale fisheries the power requirements are modest and a small generating unit would suffice. The easiest way to harness tidal power for small generators (10–100 KW) would be to have them driven by paddle wheels fitted to a series of floating barges or pontoons. The barges could be moored to anchored buoys so that they could swing either way with the tide. One disadvantage to tidal power is that it declines, stops and changes direction every six hours or so. A tidal-electric system would need to have sufficient storage capacity to provide power through the 2 or 3 hour ‘turn of tide’ period. For the other 3 or 4 hours there would be more than adequate flow.
1 McGuigan, D. Water Power, in How to Use Natural Energy. London, NEA, 1978.
Tidal streams have high power densities. A current of 2 meters per second (7.2 kilometers per hour) has a power density of 4.4 KW per square meter. Experiments have been carried out in the river Thames using 4-blade rotors one meter in diameter. It has been estimated that simple low-cost applications in slow moving rivers such as the Nile, Euphrates, Niger and Indus, could generate 0.5 KW for each square meter utilized. These small units have the advantage that they could be added to, section by section, over the years to increase the overall power supply1.
Wave power has attracted much interest in recent years. Most of the systems designed to date are large investment ones involving a whole series of anchored flexible rafts. Pairs of double-acting hydraulic cylinders act like pumps to power hydraulic motors driving generators. Power is transmitted to land by submersible cables. One large raft-rig might produce two megawatts of power. As they rely on constant wave action these rafts would not be so useful in the tropics as in the northern and southern latitudes.
Several new designs of equipment to tap wave and tidal power are currently under research. Most of them are too capital-intensive to consider for village use. Some involve air turbines propelled by the force of wave action underneath2. These may be usefully applied to lighting navigation buoys and fish shelters or payaos.
The countries of the Indo-Pacific region are blest with an abundance of pure free solar energy. The solar radiation can be converted into heat or into electricity. Most solar energy systems fall into one of these two categories. Within these two areas of technology there exists a great range of equipment varying from ultra-simple units suitable for use in the most remote and backward villages, to complex and sophisticated systems such as those used in communications satellites.
Solar heat is applied for a wide range of purposes. It can be used in desalination, in fish drying and fish cooking, and even in refrigeration. Solar fish driers are discussed in more detail in the section on fish processing. Desalination units or solar stills can produce fresh water from seawater. The volumes obtained are small, but then so also is the capital cost involved. The Brace Research Institute of Canada has done considerable work in this field and has produced workable solar still designs which can be constructed almost wholly from cheap locally available materials3. The stills are made up of 20–50 meter lengths of 2 meters width. Each square meter of still area will produce from 2.0 to 3.5 liters of fresh water per day. They cost about $15 per square meter to construct and this gives us a price of around $6 per liter per day installed price. Three 50-meter stills should provide a total of nearly 1,000 liters of potable water per day. This could be a great boon to fishing communities on islands which have no surface water available.
1 Musgrove, P. Windmills Could Come in with the Tide. New Scientist, 15 February 1979.
2 BHRA Fluid Engineering. Wave and Tidal Energy. Cranfield, Bedford, U.K., 1978.
3 Brace Research Institute, How to Make a Solar Still, D.I.Y., L1, 1973.
Solar radiation can be used to pre-heat water for canning or bottling plants, thus reducing their overall power requirements. Australian studies and experience indicate that over 50% of the heat requirements of food processing plants could be obtained with existing technology. In most plants there is no significant water usage above 150°C and over 70% of hot water is used at temperatures under 100°C. Solar heat could supply much of this1. Solar heaters can also be made in simple village units for boiling water or for cooking ovens. This could be a great asset in villages where firewood or charcoal is in short supply. There are several types of heat collectors and reflectors available. Many are of a type that can be constructed out of simple and readily available materials. For more efficient systems manufacturers offer low, mid and high temperature collectors and absorber plates. Flat plate collectors are most common. Their efficiency depends on many factors including material, insulation, number of glazings, air temperature, wind velocity, absorber surface property and, of course, amount of solar energy. Some examples are shown in Figure 11.
1 McVeigh, J.C. Sun Power. Pergamon Press, 1977.
Refrigerators and even small ice plants can be solar-powered. Most of us have used a canvas water bag at some time. The water in the bag is cooled as minute amounts evaporate through the canvas. That is a simple example of more direct solar cooling. Most solar cooling systems use the sun's radiant heat indirectly in a process called “absorption refrigeration”. These systems use ammonia or lithium bromide and water as absorbents and refrigerants. In much simpler units, solar heat can drive a refrigerator designed to operate on gas or kerosene.
An Israeli company, Ormat Turbines, Ltd. developed a 6-ton per day solar-powered ice plant. The ice plant is driven by electrical power generated by a turbine driven by steam heat. The heat is extracted from a solar pond of 10,000 m2. In 1978 the price of such a plant was $35,800 per ton per day installed capacity. That was about 8 times the cost of a conventional plant. The major cost item was the solar pond. However, even at today's fuel prices the additional capital cost might be retrieved within 10 years, and no doubt further research will bring less expensive units to the market1.
1 Fyson, J. The Use of Solar Energy for Ice Production. FAO, FII, 1979.
Electricity can be generated by solar energy using photo-voltaic cells (see Figure 13) each of which produces a minute amount of electrical current. Thousands of these cells can be connected together in one large system to produce considerable amounts of power. The American Skylab unit generated some 20 KW from its solar panels. The major constraint to widespread use of solar cells is their cost but this has been greatly reduced in recent years and it is expected that in a very short time they will be competitive with other systems of electricity generation. (See graph). Significant technical breakthroughs in silicon cell design and manufacture have already been made.
SILICON PHOTOVOLTAIC CELLS
Which convert solar energy into electricity
from Merritt, R. and Gage, T. Energy Primer 1978 Portola Institute
Dell Publishing Company
While solar-produced electricity may be a viable alternative or supplementary source of power for fishing stations, it will not, anymore than other natural sources, provide sufficient amounts to permit consumption at current extravagant levels. It has to be integrated with other power sources in villages or complexes which have been designed to take maximum advantage of natural or passive systems. For instance, buildings must be designed to permit natural ventilation and cooling, energy wasteful machines or activities must be reduced or eliminated, and proper insulation used wherever possible to minimize heat loss on iced fish. With careful thought the power requirements of a small fish plant or depot can be reduced to a minimum. The following table gives consumption rates for different items of equipment.
|Battery charger||40 watts||Deep freezer||500 watts|
|Electric cooker||8,000 watts||Deep freezer||1,000 watts|
|60 W light bulb||60 watts||Small refrigerator||200 watts|
|60 W strip light||60 watts||Large refrigerator||400 watts|
|Radio||40 watts||Water heater||1,500 watts|
To find the total consumption of electrical equipment one simply multiplies the rating by the number of units (e.g. light bulbs) and by the number of hours operation. As the above figures are in watts, divide by a thousand to get kilowatt/hours. A solar unit generating 5 KW for 10 hours a day would provide 10,000 kilowatt hours of power given 200 days of sunshine a year.