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close this bookBlending of New and Traditional Technologies - Case Studies (ILO - WEP, 1984, 312 p.)
close this folderIII. Optoelectronics
View the documentA. Laser techniques

A. Laser techniques

21. Use of laser for irradiation of silkworms (China). In the Anhui province of China, laser has been introduced by the Institute of Biology of the Chinese Academy of Sciences to irradiate silkworms. The new breeds are of higher quality: they also economise feed. The cocoon shell increases by 1.58 per cent, increasing the output value per sheet of silkworm egg paper by 3.5 per cent while the output value of mulberry leaves goes up by 13.16 per cent and the length of natural silk increases by 150 metres.17

22. Laser processing machines (Japan). The major advantages of laser processing machines are: (i) they can operate with high precision; and (ii) each machine can perform several tasks such as cutting, welding, drilling and heat treatment through adjustment of the duration of laser application. In addition they do not require a high level of skill to operate and they are economical.

In Japan laser applications include the laser-light scalpel used in medicine and laser machines used in industry for cutting, welding, drilling and measuring. A Japanese Government subsidised project undertaken by the Electro Technical Laboratory in Tsulcuba Science City aims at developing laser machines of up to 20 kW output.18

23. Use of optical fibres in telecommunications (France). The French Post Telephone Telegraph (PTT) has launched a large programme for utilising fibre optics for all medium and long haul transmission links. To date optical fibres have been used to link post offices in Paris. A 100 km transmission link with repeaters every 20-30 km is planned between LeMans and La Fleche and Anger in the west of France. The TAT 8 transatlantic cable is to be inaugurated in 1988. Optical fibre transmissions have several advantages over conventional copper cables. Their technical advantages include low signal attenuation, total immunity to electromagnetic and radiofrequency interference and unwanted tampering with or tapping of transmitted information, very high band width for simultaneous transmission of speech data, text, still and moving pictures, compactness, ease of installation and maintenance, safety of use (no risk of sparking, electrocution or overheating) and high speed of data transmission. Economically, they have been shown to be cheaper for links of above 200 mg and prices are expected to drop rapidly in the future.

24. Optical fibres in telecommunications (United States). Washington and New York are now connected by optical glass fibres. The lasers that transmit the signals flash at 90 million times a second. At that rate the whole contents of the Encyclopaedia Britannica can be transmitted over a single pair of fibres in one minute.19

25. Fibre optic systems (Japan). Over 400 optical fibre systems were installed in Japan between 1978 and 1980. In 1982, the major users included the iron and steel industry, the automobile industry and in monitoring railroad and highway traffic.

In the Fukuyama iron and steel works, fibre-optic transmission is required for in-house data transmission. This has eliminated interference from power cables supplying power to the plant. By 1981, the fibre optic transmission system had a cable length of 16 kilometres.20

26. Photovoltaic power supply in Hammam Biadha Sud (Tunisia). In February 1983 National Aeronautics and Space Administration (NASA) Lewis Research Centre installed four stand-alone photovoltaic systems in Tunisia. One such system was at a village (Hammam Biadha Sud) 150 km from Tunis.

In this village a central photovoltaic power system provides power to three sectors (domestic, commercial and public) of the village.

In the commercial sector two stores and a mill, a hairdresser, a coffee shop require up to 5 kWh of electricity per day. The domestic sector consists of 22 homes provided with 37 kWh daily to power refrigerators, lights and television sets. In the public sector 20 kWh is used daily to supply a clinic, a mosque, a cultural centre, a school and street lights. The array sub-system also consists of storage batteries and an inverter for d.c./a.c. conversion. With an inverter efficiency of 80 per cent, 119 kWh of electricity is produced per day in July and 65 kWh per day in December.

The second system is a farmhouse system serving the need of a residence remote to Hammam Biadha. The large three-family dwelling has a demand of 1.5 kWh. This system consists of a solar array, a conditioning and control sub-system, a battery sub-system and a 120 DC/230 V AC, 50 HZ inverter. Daily load is 6 kWh in July and 3 kWh in December (again assuming 80 per cent inverter efficiency).

The third and fourth photovoltaic systems in Hammam Biadha supplies pumps of two drip irrigation systems. One feeds water to a one hectare greenhouse where vegetables are grown while the other irrigates a one-hectare fruit orchard. Each system requires up to 750 cubic metres of water a day.21

27. Las Barrancas solar village (Mexico). This project is a part of the bigger project entitled “Sonntlan” which is one of the several projects developed by the Government of Mexico and the Federal Republic of Germany. It consists in an integrated use of solar energy for providing desalinated water, electricity, ice and cold space to the Pacific community of fishermen of Los Barrancas village in the Northwest of Mexico. The objectives of the project are: (a) to demonstrate the benefits from the use of solar energy; (b) to evaluate the performance and reliablility of the installed equipment in real working conditions; (c) to analyse the technical, social and economic feasibility of the solar system for replication in other parts of Mexico, and (d) to improve the living standards of the rural inhabitants.

The integral solar system installed in the village consists of a “service area in which solar and wind energy are transformed into useable forms...” The radiant solar energy is transformed into thermal energy by means of flat-plate collectors and photovoltaic cells. The flat-plate collectors heat water which is used to produce ice which is then used to preserve sea products during transport. Hot water is also used for heating brine in a multi-stage flash seawater desalination plant and in a fish-processing plant. The electric energy generated by the photovoltaic cells is normally used for driving motors in the absorption type refrigeration unit. A photovoltaic generator also provides energy for a radiotelephone system which links the village with the national telephone network.22

28. Photovoltaic power supply to Schuchuli village (United States). A 3.5 kWp, 120 voH photovoltaic array was installed in a Papago Indian reservation in southern Arizona. The 100 inhabitants are provided with electric power for water pumping, lighting, refrigeration, services and village housekeeping. Direct current (DC) systems are used to reduce losses, costs and the additional complexities of DC/AC converters. A battery of 2,380 amp-hr capacity is incorporated to provide power at night. The control system includes automatic switches to disconnect part of the solar array to prevent overcharging of the batteries and automatic load shedding to prevent excessive discharging of the batteries.23

29. Solar-power TV sets (Niger). In 1968, an experimental solar panel was installed near Niamey to power the education TX sets at a nearby school. It is reported that by 1973, about 800 students in 22 classes were receiving instructions through solar-powered television sets. It is forecast that by 1985, over 80 per cent of the population would be covered by solar-powered educational programmes.

30. Photovoltaic cells (Colombia). In Colombia, the use of solar cells for power generation was first considered in 1978 when TELECOM, the National Telecommunications Company, with the technical assistance of the Solar Energy Group of the National University, started a programme to provide 5,000 villages with radiotelephones. The system consists of solar cells panels, a battery, a control unit, and a power conditioner. TELECOM has bought 2,950 systems for a total of 114 kW peak. It is considered to be one of the largest programmes in the world which uses solar generators for rural telecommunications.24

31. Photovoltaic power supply to mosques (Egypt). In an agreement with the German Federal Ministry for Research and Technology, the Egyptian Electricity Authority has embarked on the installation of photovoltaic systems. The first such system provides power to operate the public address system in the Mit Abu El-Koum village mosque. The total power supplied is 368 W and the unit is equipped with a 48 volt storage battery. The other photovoltaic units are to be used for: water pumping and storage, water desalination, water purification, irrigation, a spray plant, a sea bury, hazard beacon, colour television, food cooling and storage and water electrolysis. The total installed power will be approximately 11 kW.25

32. Reverse osmosis water desalination plant (Mexico). Solar Reverse Osmosis (SORO) is an experimental project undertaken by the Federal Republic of Germany and the Government of Mexico. The project comprises design, construction and testing of a photovoltaic-powered brackish water desalination unit which was installed in 1980. The objectives of the project are:

- to evaluate the transformation of solar energy into electricity which is capable of making a reverse osmosis desalination unit work continuously during the daytime;

- to evaluate the ability of these combined systems to provide potable water on the basis of an independent source of energy. Evaluation of the project will concentrate on the plant performance, number and causes of failures, equipment lifetime, water quality and economic feasibility.26

33. Photovoltaic-powered irrigation (United States). In Mead, Nebraska an irrigation system operated by photovoltaic array was set up in a project sponsored by the Department of Energy. For its first two years of operation failure rate of the system was two per cent and important statistical information on such aspects as sorting and cleaning have been obtained.27

34. Photovoltaic systems (Mali). At least five photovoltaic systems have been installed in Mali with French assistance. These are used primarily for pumping water to rural areas. A 16 kWp system installed in a hospital provides power for water pumping, refrigeration of pharmaceuticals, lighting and cooling of operating rooms.