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| − | =Solar Photovoltaic Energy - Technical Brief=
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| − | Photovoltaic (PV) is a technology that converts sunlight directly into electricity. It was first observed in 1839 by the French scientist Becquerel who detected that when light was directed onto one side of a simple battery cell, the current generated could be increased. In the late 1950s, the space programme provided the impetus for the development of crystalline silicon solar cells; the first commercial production of PV modules for terrestrial applications began in 1953 with the introduction of automated PV production plants.
| + | Extensive immunisation programmes are in progress throughout the developing world in the fight against the common communicable diseases. To be effective these programmes must provide immunisation services to rural areas. |
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| − | Today, PV systems have an important use in areas remote from an electricity grid where they provide power for water pumping, lighting, vaccine refrigeration, electrified livestock fencing, telecommunications and many other applications. With the global demand to reduce carbon dioxide emissions, PV technology is also gaining popularity as a mainstream form of electricity generation. Some tens of thousands of systems are currently in use yet this number is insignificant compared to the vast potential that exists for PV as an energy source.
| + | Solar radiation tends to be high in climates that have great needs for cooling, a great deal of effort has been directed to develop solar powered refrigerators. Although some solar absorption (thermal) refrigerators have been developed only solar photovoltaic (electric) refrigerators have so far proved reliable. |
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| − | Photovoltaic modules provide an independent, reliable electrical power source at the point of use, making it particularly suited to remote locations. PV systems are technically viable and, with the recent reduction in production costs and increase in conversion efficiencies, can be economically feasible for many applications.
| + | Solar photovoltaic power for refrigerators has great potential for lower running costs, greater reliability and a longer working life than kerosene refrigerators or diesel generators, which have been generally used in remote areas. Over the past five years, at least 3000 photovoltaic medical refrigerators have been installed. |
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| − | [[Image:Photovoltaic01.jpg]]<br /> Figure 1: Array of PV Panels<br />
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| − | © Smail Khennas/Practical Action
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| − | </blockquote>
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| − | <br /> The use of PV electricity in developing countries
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| − | The majority of the world's developing countries is found within the tropics and hence have ample sources of solar insolation (the total energy per unit area received from the sun). The tropical regions also benefit from having a small seasonal variation of solar insolation, even during the rainy season, which means that, unlike northern industrial countries, solar energy can be harnessed economically throughout the year.
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| − | Currently, there is a fairly high uptake of solar technology in developing countries. The chart below (Figure 2) shows the status of the PV technology worldwide.
| + | ==The need== |
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| − | <center>
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| − | [[Image:Photovoltaic02.jpg]]<br /> Figure 2: PV module use by region
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| − | </center></div>
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| − | ==Technical== | |
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| − | The nature and availability of solar radiation | + | All vaccines have to be kept within a limited temperature range throughout transportation and storage. The provision of refrigeration for this, known as the Vaccine 'Cold Chain', is a major logistical undertaking in areas where electricity supplies are non-existent or erratic. The performance of refrigerators fuelled by kerosene and bottled gas is often inadequate. Diesel powered systems frequently suffer fuel supply problems. Solar power is therefore of great importance to health care. |
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| − | Solar radiation arrives on the surface of the earth at a maximum power density of approximately 1 kilowatt per metre squared (kWm<sup>-2</sup>). The actual usable radiation component varies depending on geographical location, cloud cover, hours of sunlight each day, etc. In reality, the solar flux density (same as power density) varies between 250 and 2500 kilowatt hours per metre squared per year (kWhm<sup>-2</sup> per year). As might be expected the total solar radiation is highest at the equator, especially in sunny, desert areas.
| + | </div> |
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| − | Solar radiation arrives at the earth's outer atmosphere in the form of a direct beam. This light is then partially scattered by cloud, smog, dust or other atmospheric phenomenon (see Figure 3 below). We therefore receive solar radiation either as ''direct'' radiation or scattered or ''diffuse'' radiation, the ratio depending on the atmospheric conditions. Both direct and diffuse components of radiation are useful, the only distinction between the two being that diffuse radiation cannot be concentrated for use.
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| − | <center>
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| − | [[Image:Photovoltaic03.gif]]<br /> Figure 3: Direct and Diffuse Solar Radiation
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| − | </center>
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| − | The geometry of earth, sun and collector panel
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| − | The earth revolves around the sun with its axis tilted at an angle of 23.5 degrees. It is this tilt that gives rise to the seasons. The strength of solar flux density is dependent upon the angle at which it strikes the earth's surface, and so, as this angle changes during the yearly cycle, so the solar insolation changes. Thus, in northern countries, in the depths of winter, the sun will be low in the sky to the south, or may not even be seen at all in arctic regions. The radiation strikes the earth's surface obliquely and solar gain (solar yield) is low. If we are using a solar photovoltaic panel to capture the sun's energy then the orientation of this panel is also critical to the amount of energy we will capture. The relationship is complex and only with sophisticated tracking systems can the maximum energy be extracted for any given location.
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| − | The PV cell, modules and arrays
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| − | When light falls on the active surface, the electrons in a solar cell become energised, in proportion to the intensity and spectral distribution (wavelength distribution) of the light. When their energy level exceeds a certain point a potential difference is established across the cell. This is then capable of driving a current through an external load.
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| − | All modern, commercial PV devices use silicon as the base material, mainly as monocrystalline or multi-crystalline cells, but more recently also in amorphous form. Other materials such as copper indium diselenide and cadmium telluride are being developed with the aim of reducing costs and improving efficiencies. A mono-crystalline silicon cell is made from a thin wafer of a high purity silicon crystal, doped with a minute quantity of boron. Phosphorus is diffused into the active surface of the wafer. At the front electrical contact is made by a metallic grid; at the back contact usually covers the whole surface. An antireflective coating is applied to the front surface. Typical cell size is about 15 cms diameter. The process of producing efficient solar cells is costly due to the use of expensive pure silicon and the energy consumed, but as materials technology improves costs are slowly dropping making PV technology more attractive.
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| − | [p04.jpg [[Image:Photovoltaic04.jpg]]]<br /> Figure 4: PV price trends
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| − | </center>
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| − | Cost has been the major barrier to the widespread uptake of PV technology. Cost of PV modules is usually given in terms of Peak Watt (Wp), which is the power rating of the panel at peak conditions - that is at 1kWm<sup>-2</sup> irradiance at 25°C.
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| − | Solar cells are interconnected in series and in parallel to achieve the desired operating voltage and current. They are then protected by encapsulation between glass and a tough resin back. This is held together by a stainless steel or aluminium frame to form a ''module''. These modules, usually comprised of about 30 PV cells, form the basic building block of a ''solar array''. Modules may be connected in series or parallel to increase the voltage and current, and thus achieve the required solar array characteristics that will match the load. Typical module size is 50Wp and produces direct current electricity at 12V (for battery charging for example).
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| − | Commercially available modules fall into three types based on the solar cells used.<br />
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| − | • ''Mono-crystalline cell modules.'' The highest cell efficiencies of around 15% are obtained with these modules. The cells are cut from a mono-crystalline silicon crystal.
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| − | • ''Multi-crystalline cell modules''. The cell manufacturing process is lower in cost but cell efficiencies of only around 12% are achieved. A multi-crystalline cell is cut from a cast ingot of multi-crystalline silicon and is generally square in shape.
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| − | • ''Amorphous silicon modules.'' These are made from thin films of amorphous silicon where efficiency is much lower (6-9%) but the process uses less material. The potential for cost reduction is greatest for this type and much work has been carried out in recent years to develop amorphous silicon technology. Unlike monocrystalline and multi-crystalline cells, with amorphous silicon there is some degradation of power over time.
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| − | </blockquote> | |
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| − | <br /> An array can vary from one or two modules with an output of 10W or less, to a vast bank of several kilowatts or even megawatts.<br />
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| − | <blockquote>
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| − | • ''Flat plate arrays'', which are held fixed at a tilted angle and face towards the equator, are most common. The angle of tilt should be approximately equal to the angle of latitude for the site. A steeper angle increases the output in winter; a shallower angle - more output in summer. It should be at least 10 degrees to allow for rain runoff.
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| − | • ''Tracking arrays'' follow the path of the sun during the day and thus theoretically capture more sun. However, the increased complexity and cost of the equipment rarely makes it worthwhile.
| + | ==Relative merits of using photovoltaic refrigerators== |
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| − | • ''Mobile (portable) arrays'' can be of use if the equipment being operated is required in different locations such as with some lighting systems or small irrigation pumping systems.
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| − | </blockquote></div>
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| − | ==Solar PV systems== | |
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| − | PV systems are most commonly used for stand-alone applications. They can be used to drive a load directly; water pumping is a good example - water is pumped during the hours of sunlight and stored for use; or a battery can be used to store power for use for lighting during the evening. If a battery charging system is used then electronic control apparatus will be needed to monitor the system. All the components other than the PV module are referred to as the balance-of-system (BOS) components. Below, in Figure 5, three possible configurations of stand-alone PV system are shown. Such systems can often be bought as kits and installed by semi-skilled labour. (Source: The Power Guide, ITDG Publishing 1994)
| + | Compared to kerosene or bottled gas fuelled refrigerators, photovoltaic systems have the following advantages: |
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| − | For correct sizing of PV systems, the user needs to estimate the demand on the system, as well as acquiring information about the solar insolation in the area (approximations can be made if no data is readily available). It is normally assumed that for each Wp of rated power the module should provide 0.85watt hours of energy for each kWhm<sup>-2</sup> per day of insolation (Hulscher 1994). Therefore if we consider a module rated at 200 Wp and the insolation for our site is 5 kWhm<sup>-2</sup> per day (typical value for tropical regions), then our system will produce 850Wh per day (that is 200 x 0.85 x 5 = 850).
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| − | Some systems use lenses or mirrors to concentrate direct solar radiation onto smaller areas of solar cells. As the power output is directly proportional to the solar power directed onto the PV cell, this method is useful for reducing the area required for collection. The cost of the concentrators, however, often offset the cost of savings made on reducing the size of the module.
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| − | <center>
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| − | [[Image:Photovoltaic06.gif]]<br /> Figure 5: Common configurations of PV systems
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| − | </center>
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| − | Some benefits of photovoltaics<br />
| + | '''Improved vaccine storage facilities as a result of:'''<br /> |
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| − | • No fuel requirements - In remote areas diesel or kerosene fuel supplies are erratic and often very expensive. The recurrent costs of operating and maintaining PV systems are small. | + | • elimination of fuel supply problems<br /> • elimination of fuel quality problems<br /> • greater refrigerator reliability<br /> • better refrigerator performance (and temperature control). |
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| − | • Modular design - A solar array comprises individual PV modules, which can be connected to meet a particular demand. | |
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| − | • Reliability of PV modules - This has been shown to be significantly higher than that of diesel generators.
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| − | • Easy to maintain - Operation and routine maintenance requirements are simple.
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| − | • Long life - With no moving parts and all delicate surfaces protected, modules can be expected to provide power for 15 years or more. | |
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| − | • National economic benefits - Reliance on imported fuels such as coal and oil is reduced. | |
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| − | • Environmentally benign - There is no pollution through the use of a PV system - nor is there any heat or noise generated which could cause local discomfort. PV systems bring great improvements in the domestic environment when they replace other forms of lighting - kerosene lamps, for example.
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| | </blockquote> | | </blockquote> |
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| − | <br /> PV applications in lesser developed countries | + | <br />'''Reduced running costs as a result of:'''<br /> |
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| − | ''1. Rural electrification''<br /> | |
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| − | • lighting and power supplies for remote building (mosques, churches, temples etc farms, schools, mountain refuge huts) - low wattage fluorescent lighting is recommended | + | • elimination of kerosene fuel costs<br /> • elimination of kerosene transportation costs<br /> • reduced vaccine losses<br /> • lower refrigerator maintenance costs<br /> • reduced needs for back-up refrigerators where there are fuel supply or repair problems. |
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| − | • power supplies for remote villages
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| − | • street lighting
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| − | • individual house systems
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| − | • battery charging
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| − | • mini grids
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| − | </blockquote><center> | |
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| − | [[Image:Photovoltaic07.jpg]]<br /> Figure 6: PV can be used to power water pumping systems<br />
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| − | </center><blockquote> | |
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| − | © Practical Action
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| | </blockquote> | | </blockquote> |
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| − | <br />''2. Water pumping and treatment systems''<br /> | + | <br />'''Cold chain management benefits due to:'''<br /> |
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| − | • pumping for drinking water<br /> • pumping for irrigation<br /> • dewatering and drainage<br /> • ice production<br /> • saltwater desalination systems<br /> • water purification | + | • longer equipment life (photovoltaic array 15 years, battery 5 years refrigerator 10 years)<br /> • reduced logistical problems arising from non-availability of working refrigerators<br /> • reduced logistical problems arising from lower vaccine losses. |
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| | </blockquote> | | </blockquote> |
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| − | <br />''3. Health care systems''<br /> | + | <br /> The above operational advantages of introducing solar refrigerators into the cold chain indicate that solar refrigerators can provide a more sustainable vaccine cold chain. |
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| − | <blockquote>
| + | It should be noted however, that as each system is site specific, more time is necessary for planning and implementing a project with solar refrigerators. |
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| − | • lighting in rural clinics<br /> • UHF transceivers between health centres<br /> • vaccine refrigeration<br /> • ice pack freezing for vaccine carriers<br /> • sterilises<br /> • blood storage refrigerators
| + | User training demands are also higher since a new technology is being introduced. |
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| − | </blockquote><center> | + | </div> |
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| − | [p08.gif [[Image:Photovoltaic08.gif]]]<br /> Figure 7: PV is frequently used to power vaccine refrigeration in remote health centres
| + | ==Comparative costs== |
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| − | </center> | + | <div class="booktext"> |
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| − | ''4. Communications''<br />
| + | A true comparison of solar refrigerators and comparable kerosene and bottled gas fuelled refrigerators can only be made through a life-cycle cost analysis. |
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| − | <blockquote>
| + | A solar photovoltaic refrigerator cabinet only is likely to cost around US $1300 - 2600 (with the complete system costing around US $3000 - 5000) and will cost more to install than a kerosene unit. A kerosene refrigerator will cost only US $650 - 1300 but will use 0.5 - 1.4 litres of fuel per day, require frequent maintenance and have a shorter life. In general, life-cycle costs are approximately the same for solar and kerosene refrigerators, but because of their greater reliability and resultant savings in wasted vaccine, solar refrigerators are the preferred option. |
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| − | • radio repeaters<br /> • remote TV and radio receivers<br /> • remote weather measuring<br /> • mobile radios<br /> • rural telephone kiosks<br /> • data acquisition and transmission (for example, river levels and seismographs)
| + | </div> |
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| − | </blockquote>
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| − | <br />''5. Transport aids''<br />
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| − | • road sign lighting<br /> • railway crossings and signals<br /> • hazard and warning lights<br /> • navigation buoys<br /> • road markers
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| − | </blockquote>
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| − | <br />''6. Security systems''<br />
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| − | • security lighting<br /> • remote alarm system<br /> • electric fences
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| − | </blockquote>
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| − | <br />''7. Miscellaneous''<br />
| + | ==The technology== |
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| − | <blockquote>
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| − | • ventilation systems<br /> • calculators<br /> • pumping and automated feeding systems on fish farms<br /> • solar water heater circulation pumps<br /> • boat/ship power<br /> • vehicle battery trickle chargers<br /> • earthquake monitoring systems<br /> • emergency power for disaster relief
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| − | </blockquote></div>
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| − | ==Other issues== | |
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| − | Manufacture in developing countries
| + | '''Refrigerator''' |
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| − | PV technology is sophisticated and the manufacturing plant is expensive. There is little scope for local manufacture in rural areas of developing countries, although some BOS components such as frameworks for mounting PV modules can be made in small workshops and will save on expensive transportation costs. There are however, large-scale manufacturers of PV modules working in developing countries. In India, for example, Central Electronics of Ghaziabad is not only the nation's largest PV producer, but are the fifth largest producer of monocrystalline silicon solar cells in the world (D.V. Gupta cited in Garg et al, 1997). There are over 60 companies in India alone producing solar cells, modules and systems.
| + | Photovoltaic refrigerators operate on the same principle as normal compression refrigerators but incorporate low voltage (12 or 24v) dc compressors and motors, rather than mains voltage ac types. A photovoltaic refrigerator has higher levels of insulation around the storage compartments to maximise energy efficiency, a battery bank for electricity storage, a battery charge regulator and a controller which converts the power from the battery to a form required by the compressor motor. |
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| − | Dissemination
| + | A typical refrigerator layout is as shown below (Figure 1). Most refrigerators include a freezer compartment for ice pack freezing. Other systems have separate units to provide solely for refrigeration or freezing. Available sizes range between 10 and 85 litres of vaccine storage capacity with ice production rates of up to 6.4 kg per 24 hours. |
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| − | <div align="left"> | + | <center> |
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| − | {| border="1" cellpadding="5"
| + | [[Image:Refrigeration_Vaccines_1.gif]]<br /> Figure 1: A typical refrigerator layout |
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| − | There is a vast scope for and potential for the use of PV technology in India. There are still over 90,000 villages in the country to be electrified. Recognising the importance of PV technology in the Indian context, the Government has been implementing a comprehensive programme covering R & D, demonstration, commercialisation and utilisation for more than 15 years.
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| − | Among the elements of the action plan are the following aims:<br />
| + | </center> |
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| + | '''Batteries''' |
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| − | • deployment of 400,000 solar lanterns as a substitute for kerosene lanterns<br /> • rural electrification through PV systems covering 400 villages/hamlets<br /> • a special programme on water pumping systems<br /> • intensified R & D on technologies which can lead to a reduction in cost<br /> • commercialisation of PV systems for various applications by giving a market orientation to the programme and promoting manufacturing and related activities
| + | The battery most commonly used is the lead acid type, long life, deep cycle batteries are preferred. A capacity to run the refrigerator for five days without sun is recommended. |
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| − | </blockquote>
| + | '''Charge regulator''' |
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| − | <br /> As a result of these measures India is among the leading countries in the world in the development and use of PV technology.
| + | The charge regulator maintains the power supply within the current and voltage range tolerated by the refrigerator and prevents overcharge of the battery. Some models include an audible alarm or warning light to signal when battery voltage becomes low. Lightning surge protection must be provided for tropical areas. |
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| − | </div><blockquote>
| + | '''Array and support structure''' |
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| − | Source: E.V.R. Sastry, cited in Garg et al, 1997.
| + | The solar array can be for roof or ground mounting. The array size for a refrigeration system is calculated to meet the power requirements of the system, given the solar irradiance data for the proposed site. The typical requirement is 150 - 200 Wp of photovoltaic modules. |
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| − | </blockquote>
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| − | <br /> Hybrid systems
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| − | Solar PV systems can be used in conjunction with other energy technologies to provide an integrated, flexible system for remote power generation. These systems are referred to as hybrid systems. Common configurations of hybrid systems could include a solar PV array, wind generator and diesel generator set which would allow generation in all weather conditions. Such systems need careful planning.
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| − | Solar lanterns
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| − | A recent innovation in solar technology is the solar lantern. Originally designed for the outdoor leisure market in western countries, this simple lantern with a small PV module (5-10 watts) is extremely appropriate to use in rural areas of developing countries for replacing kerosene lamps. Cost is still a barrier, as is the potential for local manufacture, but there is enormous scope for widespread dissemination of a simple, robust solar lantern.
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| − | Micro grids or stand-alone
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| − | Solar PV technology is presently best suited to stand-alone applications but can also be used for providing power for small grid systems, with centralised power generation. As the cost of PV cell production drops, their use for medium scale electricity production is being adopted more widely. There is also scope for large-scale electricity production for such applications as peak power provision.
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| | </div> | | </div> |
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| − | ==Resources and references== | + | ==Performance== |
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| − | H.P. Garg, D. Gouri, and R. Gupta: Renewable Energy Technologies. Indian Institute of technology and the British High Commission, 1997.
| + | The energy consumption of a photovoltaic vaccine refrigerator is typically 400 - 800 watt-hours per 24 hours for a 100-litre refrigerator without icepack freezing and at +32°C ambient temperature. At +43°C ambient temperature and freezing 2kg of ice packs per 24 hours the energy consumption of the same refrigerator would rise to about 900 - 1900 watt-hours per 24 hours. It is very important not to overload a solar refrigerator as this increases energy consumption considerably. |
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| − | S. Karekezi and T. Ranja: Renewable Energy Technologies in Africa. AFREPREN/SEI/Zed Books, 1997.
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| − | T.B. Johansson, H. Kelly, A.K.N. Reddy and R.H. Williams: Renewable Energy - Sources for fuels and electricity. Island Press, 1993.
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| − | J. Twidell and T. Weir: Renewable Energy Resources. E & F.N. Spon, 1990.
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| − | W. Hulscher and P. Fraenkel: The Power Guide - An international catalogue of small-scale energy equipment. ITDG Publishing, 1994.
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| − | A. Derrick, C. Francis and V. Bokalders: Solar Photovoltaic Products - A guide for development workers. IT Publications and IT Power, 1991.
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| − | J.P. Louineau, M. Dicko, P. Fraenkel, R. Barlow and V. Bokalders: Rural Lighting - A guide for development workers. IT Publications and The Stockholm Environment Institute, 1994.
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| − | S. Roberts: Solar Electricity - A practical guide to designing and installing photovoltaic systems. Prentice Hall, 1991.
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| − | G. Foley: Photovoltaic Applications in Rural Areas of the Developing World. World Bank, 1995.
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| − | A. Cabraal, M. Cosgrave-Davies and L. Schaeffer: Best Practices for Photovoltaic Household Electrification Programs. World Bank, 1996. | + | A good vaccine refrigerator should be able to maintain correct internal temperatures for at least ten hours in the event of being disconnected from the battery and solar array. |
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| | </div> | | </div> |
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| − | ==Internet addresses== | + | ==Costs== |
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| − | Solarbuzz Inc.<br />http://www.solarbuzz.com
| + | The output of a photovoltaic array will vary according to the location at which it is to be installed and the refrigerator energy consumption will depend on local climate. Therefore the size of the solar array, the battery storage capacity and hence the system cost will vary depending on location. Typical system costs are in the range of US $3,500 - 7500 excluding transport and installation. |
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| − | British Photovoltaic<br /> Association http://www.pv-uk.org.uk
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| − | International Centre for Application of Solar Energy<br />http://www.case.gov.au
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| − | International Energy Agency Photovoltaic Power Systems Programme<br />http://www.iea-pvps.org/
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| − | Ekomation Solar Energy Consultants, Netherlands<br />http://www.pvportal.com
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| − | Home Power Magazine<br />http://www.homepower.com/
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| − | U.S. National Centre for Photovoltaics<br />http://www.nrel.gov/ncpv
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| − | Centre for Renewable Energy and Sustainable Technology<br />http://www.solstice.crest.org
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| − | Independent site operated by ECOFYS BV, Utrecht, Netherlands<br />http://www.mysolar.com
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| − | ISES's World-wide Information System for Renewable Energy<br />http://www.wire.ises.org
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| | </div> | | </div> |
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| − | ==Manufacturers/Suppliers of photovoltaic products== | + | ==Products available== |
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| − | Note: This is a selective list of suppliers and does not imply endorsement by Practical Action.
| + | The Department of Vaccines and Biologicals of the World Health Organisation, in its Immunisation Systems Series publishes, every two years, a document entitled 'Product Information Sheets'. This catalogues equipment that has undergone tests to verify their performance is of a standard acceptable to the World Health Organisation (WHO) and United Nations Children Fund (UNICEF). The document may be obtained from: The V & B Document Centre, Department of Vaccine and Biologicals, World Health Organisation, CH-1211 Geneva 27, Switzerland. (Website: http://www.who.int/vaccines-documents, email: [mailto:vaccines@who.int vaccines@who.int]) |
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| − | Solar systems
| + | '''Suppliers''' |
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| − | Siemens Bangladesh,<br /> Jiban Bian Tower, 12<sup>th</sup> Floor, 10 Dikusha<br /> Commercial Area, Dhaka 1000, Bangladesh<br /> Tel: +880 2 956 3734<br /> Fax: +880 2 956 3740<br /> Email: [mailto:sblpower@bangla.net sblpower@bangla.net]
| + | Note: This is a selective list of suppliers and does not imply Practical Action endorsement or promotion. |
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| − | Animatics Ltd.,<br /> Haile Selassie Avenue, P.O. Box 72011, Nairobi, Kenya<br /> Tel: +254 2 210 300<br /> Fax: +254 2 210 315
| + | BP Solar Ltd., PO Box 191, Chertsey Road,<br /> Sunbury-on-Thames, Middlesex TW16 7XA,<br /> United Kingdom<br /> Tel: +44 1932 779 543<br /> Fax: +44 1932 762 686 |
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| − | Lotus Energy Pvt. Ltd.,<br /> Bhatbhateni Dhunge Dhara, P.O. Box 9219, Kathmandu, Nepal<br /> Tel: +977 1 418 203<br /> Fax: +977 1 412 924<br /> Email: [mailto:info@lotusenergy.com info@lotusenergy.com]<br /> Web: http://www.lotusenergy.com
| + | Dulas Ltd., Dyfi Eco Park, Machynlleth, Powys<br /> SY20 8SX, U.K.<br /> Telephone: +44 1654 705 000<br /> Fax: +44 1654 703 000 |
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| − | CIME Commercial S.A.,<br /> Av. Libertadores # 757, San Isidro, Lima 27, Peru<br /> Tel: +511 222 6083<br /> Fax: +511 222 6330
| + | Comesse Soudure SA, 88390 Chaumousey,<br /> France<br /> Tel: +33 3 2966 8548<br /> Fax: +33 3 2966 8094<br /><u>Note</u><nowiki>: The unit supplied is solar thermal and</nowiki><br /> not solar photovoltaic |
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| − | Link Intertrade (Private) Ltd.,<br /> 385C Old Kotte Road, Rajagiriya, Sri Lanka<br /> Tel: +94 1 873 211-2<br /> Fax: +94 1 867 952<br /> Email: [mailto:intertrade@link.lk intertrade@link.lk]
| + | Electrolux (Luxembourg) SARL, 14 op der Hei,<br /> L-9808 Hosingen, Luxembourg<br /> Telephone: +352 920 731<br /> Fax: +352 920 731 300 |
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| − | Solarman Co.,<br /> P.O. Box 11545, Khartoum, Sudan<br /> Tel: +249 11 472 337<br /> Fax: +249 11 473 138<br /> Email: [mailto:solarman29@hotmail.com solarman29@hotmail.com]
| + | NAPS Norway A/S, Strandvein 50, N-1366<br /> Lysaker, Norway<br /> Tel: +47 67 112 550<br /> Fax: +47 67 112 545 |
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| − | Alternative Technologies Pvt. Ltd.,<br /> 3 Canald Road, Graniteside, Harare, Mash Cent, Zimbabwe<br /> Tel: +263 4 781 972-7<br /> Fax: +263 4 775 264<br /> Email: [mailto:snakes@zambezi.net snakes@zambezi.net]
| + | Solamatics (Pvt) Ltd., 31 Edison Road,<br /> Graniteside, Harare, Zimbabwe<br /> Tel: +263 4 749 930<br /> Fax: +263 4 771 212 |
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| − | Kenital Solar Energy,<br /> Ngong Road, P.O. Box 19764, Nairobi, Kenya<br /> Tel: +254 2 715 960<br /> Fax: +254 2 718 959<br /> Email: [mailto:info@kenital.com info@kenital.com]<br /> Web: http://www.kenital.com
| + | TATA BP Solar India Ltd., Plot No. 78,<br /> Electronic City, Hosur Road,<br /> Bangalore 561 229, India<br /> Tel: +91 80 852 1016<br /> Fax: +91 80 852 0116 |
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| − | Wisdom Light Group (P) Ltd.,<br /> Gha/2, 178 Siphal-Kalopul, GPO Box 6921, Kathmandu, Nepal<br /> Tel: +977 1 483 154/5<br /> Fax: +977 1 482 154<br /> Email: [mailto:info@wisdomlight.com.np info@wisdomlight.com.np]<br /> Web: http://www.wisdomlight.com.np
| + | Norcoast Refrigeration Co, 50 Grigor Street,<br /> Caloundra, Queensland 4551, Australia<br /> Tel: +61 7 9491 1849<br /> Fax: +61 7 5491 7627<br /> Website: http://www.norcoast.com.au |
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| − | Ferreyros,<br /> Av. Industrial 675-Lima, Peru<br /> Tel: +511 336 7070<br /> Fax: +511 336 8331<br /> Web: http://www.ferreyros.com.pe
| + | Sun Frost, PO Box 1101, 824 St Ste # 7,<br /> Arcata, California 95518, USA<br /> Tel: +1 707 822 9095<br /> Fax: +1 707 822 6213 |
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| − | Solar Power & Light Co. Ltd.,<br /> 10 Havelock Place, Colombo 5, Sri Lanka<br /> Tel: +94 1 688 730<br /> Fax: +94 1 686 307
| + | '''Practical Action, The Schumacher Centre for Technology & Development'''<br />'''Bourton Hall, Bourton-on-Dunsmore, Rugby, Warwickshire CV23 9QZ, UK'''<br />'''Tel: +44 (0)1926 634400 Fax: +44 (0)1926 634401 E-mail: [mailto:infoserv@practicalaction.org.uk infoserv@practicalaction.org.uk] Web: http://www.practicalaction.org''' |
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| − | U.T.E. Group of Companies,<br /> P.O. Box 2074, Khartoum, Sudan<br /> Tel: +249 11 70147<br /> Fax: +249 11 70147
| + | '''Intermediate Technology Development Group Ltd Patron HRH - The Prince of Wales, KG, KT, GCB'''<br />'''Company Rag. No 871954, England Rag. Charity No 247257 VAT No 241 5154 92''' |
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| − | Solamatics,<br /> 31 Edison Crescent, Graniteside, P.O. Box 2851, Harare, Zimbabwe<br /> Tel: +263 4 749 930<br /> Fax: +263 4 771 212<br /> Email: [mailto:mikem@mcdiarmid.co.zw mikem@mcdiarmid.co.zw]
| + | </div> |
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| − | Solar modules
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| − | Shell Solar<br /> Postbus 3049, 5700 JC, Helmond, Netherlands<br /> Tel: +31 492 50 86 08<br /> Fax: +31 492 50 86 00<br /> Email: [mailto:info@shellsolar.nl info@shellsolar.nl]<br /> Web: http://www.shellsolar.com
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| − | Sharp Photovoltaics Div<br /> 282-1 Hajikami, Shinjo-cho, Kita-Katsuragigun,<br /> Nara Prefecture 639-2198, Japan<br /> Tel: +81 745 63 3579<br /> Fax: +81 745 62 8253<br /> Email: [mailto:webmaster@sharp.co.jp webmaster@sharp.co.jp]<br /> Web: http://www.sharp.co.jp
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| − | BP Solar Headquarters<br /> 989 Corporate Drive, Linthicum, Maryland, MD 21090, USA<br /> Tel: +1 410 981 0240<br /> Email:<br /> Web: http://www.bpsolar.com
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| − | Bharat Heavy Electricals Ltd. (BHEL)<br /> Jeevan Tara Building, 5 Sansad Marg, New<br /> Delhi, 110001, India<br /> Tel: +91 11 334 7331<br /> Fax: +91 11 334 2769<br /> Email: [mailto:bhelsanchar@vsnl.com bhelsanchar@vsnl.com]<br /> Web: http://www.bhel.com
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| − | Angewandte Solar Energie (ASE) GmbH (now RWE Solutions)<br /> Industriestrasse 13, Alzenau, Germany D63755<br /> Tel: +49 (0)6023 91 1712<br /> Fax: +49 (0)6023 91 1700<br /> Email: [mailto:asesales@ase.tessag.com asesales@ase.tessag.com]<br /> Web: http://www.ase-international.com
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| − | Photowatt International SA (Part of Matrix Solar Technologies Inc.)<br /> 33 rue St. Honore, Z.I. Champfleuri,<br /> 38300 Bourgoin Jallieu, France<br /> Tel: +33 (0)474 93 80 20<br /> Fax: +33 (0)474 93 80 40<br /> Email: [mailto:marketing@photowatt.com marketing@photowatt.com]<br /> Web: http://www.matrixsolar.com
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| − | Central Electronics Ltd. (CEL)<br /> 4 Industrial Area, Sahibabad, Uttar Pradesh 201010, India.<br /> Tel: +91 120 4771941, 4771910<br /> Fax: +91 120 4771843<br /> Email: [mailto:cel@celsolar.com cel@celsolar.com]<br /> Web: http://www.celsolar.com
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| − | '''Practical Action, The Schumacher Centre for Technology & Development'''<br />'''Bourton Hall, Bourton-on-Dunsmore, Rugby, Warwickshire CV23 9QZ, UK'''<br />'''Tel: +44 (0)1926 634400 Fax: +44(0)1926 634401'''<br />'''E-mail: [mailto:Infoserv@practicalaction.org.uk Infoserv@practicalaction.org.uk] Web: http://www.practicalaction.org'''
| + | [javascript:openWindow2('/collect/gtzinti/static/feedback.htm',750,600) Please provide your feedback] |
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| − | '''Intermediate Technology Development Group Ltd Patron HRH -'''<br />'''The Prince of Wales, KG, KT, GCB'''<br />'''Company Reg. No 871954, England Reg. Charity No 247257 VAT No 241 5154 92'''<br />
| + | <span class="langmeniuactiv"> English </span><nowiki>|</nowiki>[gsdl?e=d-00gtzinti---000--1-0--010---4----0--0-10l--1en-5000---50-about-0---01131-0011T7%2eCNJnXc0a8012f0000057844f1611d-0utfZz-8-0-0&cl=CL2.1.5&d=Js7742e&az=A>=2&gc=&ihs=0&l=fr&az=A&p=about French ]<nowiki>|</nowiki>[gsdl?e=d-00gtzinti---000--1-0--010---4----0--0-10l--1en-5000---50-about-0---01131-0011T7%2eCNJnXc0a8012f0000057844f1611d-0utfZz-8-0-0&cl=CL2.1.5&d=Js7742e&az=A>=2&gc=&ihs=0&l=es&az=A&p=about Spanish ] |
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PRACTICAL ACTION
Technology challenging poverty
Introduction
Extensive immunisation programmes are in progress throughout the developing world in the fight against the common communicable diseases. To be effective these programmes must provide immunisation services to rural areas.
Solar radiation tends to be high in climates that have great needs for cooling, a great deal of effort has been directed to develop solar powered refrigerators. Although some solar absorption (thermal) refrigerators have been developed only solar photovoltaic (electric) refrigerators have so far proved reliable.
Solar photovoltaic power for refrigerators has great potential for lower running costs, greater reliability and a longer working life than kerosene refrigerators or diesel generators, which have been generally used in remote areas. Over the past five years, at least 3000 photovoltaic medical refrigerators have been installed.
The need
All vaccines have to be kept within a limited temperature range throughout transportation and storage. The provision of refrigeration for this, known as the Vaccine 'Cold Chain', is a major logistical undertaking in areas where electricity supplies are non-existent or erratic. The performance of refrigerators fuelled by kerosene and bottled gas is often inadequate. Diesel powered systems frequently suffer fuel supply problems. Solar power is therefore of great importance to health care.
Relative merits of using photovoltaic refrigerators
Compared to kerosene or bottled gas fuelled refrigerators, photovoltaic systems have the following advantages:
Improved vaccine storage facilities as a result of:
• elimination of fuel supply problems
• elimination of fuel quality problems
• greater refrigerator reliability
• better refrigerator performance (and temperature control).
Reduced running costs as a result of:
• elimination of kerosene fuel costs
• elimination of kerosene transportation costs
• reduced vaccine losses
• lower refrigerator maintenance costs
• reduced needs for back-up refrigerators where there are fuel supply or repair problems.
Cold chain management benefits due to:
• longer equipment life (photovoltaic array 15 years, battery 5 years refrigerator 10 years)
• reduced logistical problems arising from non-availability of working refrigerators
• reduced logistical problems arising from lower vaccine losses.
The above operational advantages of introducing solar refrigerators into the cold chain indicate that solar refrigerators can provide a more sustainable vaccine cold chain.
It should be noted however, that as each system is site specific, more time is necessary for planning and implementing a project with solar refrigerators.
User training demands are also higher since a new technology is being introduced.
Comparative costs
A true comparison of solar refrigerators and comparable kerosene and bottled gas fuelled refrigerators can only be made through a life-cycle cost analysis.
A solar photovoltaic refrigerator cabinet only is likely to cost around US $1300 - 2600 (with the complete system costing around US $3000 - 5000) and will cost more to install than a kerosene unit. A kerosene refrigerator will cost only US $650 - 1300 but will use 0.5 - 1.4 litres of fuel per day, require frequent maintenance and have a shorter life. In general, life-cycle costs are approximately the same for solar and kerosene refrigerators, but because of their greater reliability and resultant savings in wasted vaccine, solar refrigerators are the preferred option.
The technology
Refrigerator
Photovoltaic refrigerators operate on the same principle as normal compression refrigerators but incorporate low voltage (12 or 24v) dc compressors and motors, rather than mains voltage ac types. A photovoltaic refrigerator has higher levels of insulation around the storage compartments to maximise energy efficiency, a battery bank for electricity storage, a battery charge regulator and a controller which converts the power from the battery to a form required by the compressor motor.
A typical refrigerator layout is as shown below (Figure 1). Most refrigerators include a freezer compartment for ice pack freezing. Other systems have separate units to provide solely for refrigeration or freezing. Available sizes range between 10 and 85 litres of vaccine storage capacity with ice production rates of up to 6.4 kg per 24 hours.
Figure 1: A typical refrigerator layout
Batteries
The battery most commonly used is the lead acid type, long life, deep cycle batteries are preferred. A capacity to run the refrigerator for five days without sun is recommended.
Charge regulator
The charge regulator maintains the power supply within the current and voltage range tolerated by the refrigerator and prevents overcharge of the battery. Some models include an audible alarm or warning light to signal when battery voltage becomes low. Lightning surge protection must be provided for tropical areas.
Array and support structure
The solar array can be for roof or ground mounting. The array size for a refrigeration system is calculated to meet the power requirements of the system, given the solar irradiance data for the proposed site. The typical requirement is 150 - 200 Wp of photovoltaic modules.
Performance
The energy consumption of a photovoltaic vaccine refrigerator is typically 400 - 800 watt-hours per 24 hours for a 100-litre refrigerator without icepack freezing and at +32°C ambient temperature. At +43°C ambient temperature and freezing 2kg of ice packs per 24 hours the energy consumption of the same refrigerator would rise to about 900 - 1900 watt-hours per 24 hours. It is very important not to overload a solar refrigerator as this increases energy consumption considerably.
A good vaccine refrigerator should be able to maintain correct internal temperatures for at least ten hours in the event of being disconnected from the battery and solar array.
Costs
The output of a photovoltaic array will vary according to the location at which it is to be installed and the refrigerator energy consumption will depend on local climate. Therefore the size of the solar array, the battery storage capacity and hence the system cost will vary depending on location. Typical system costs are in the range of US $3,500 - 7500 excluding transport and installation.
Products available
The Department of Vaccines and Biologicals of the World Health Organisation, in its Immunisation Systems Series publishes, every two years, a document entitled 'Product Information Sheets'. This catalogues equipment that has undergone tests to verify their performance is of a standard acceptable to the World Health Organisation (WHO) and United Nations Children Fund (UNICEF). The document may be obtained from: The V & B Document Centre, Department of Vaccine and Biologicals, World Health Organisation, CH-1211 Geneva 27, Switzerland. (Website: http://www.who.int/vaccines-documents, email: vaccines@who.int)
Suppliers
Note: This is a selective list of suppliers and does not imply Practical Action endorsement or promotion.
BP Solar Ltd., PO Box 191, Chertsey Road,
Sunbury-on-Thames, Middlesex TW16 7XA,
United Kingdom
Tel: +44 1932 779 543
Fax: +44 1932 762 686
Dulas Ltd., Dyfi Eco Park, Machynlleth, Powys
SY20 8SX, U.K.
Telephone: +44 1654 705 000
Fax: +44 1654 703 000
Comesse Soudure SA, 88390 Chaumousey,
France
Tel: +33 3 2966 8548
Fax: +33 3 2966 8094
Note: The unit supplied is solar thermal and
not solar photovoltaic
Electrolux (Luxembourg) SARL, 14 op der Hei,
L-9808 Hosingen, Luxembourg
Telephone: +352 920 731
Fax: +352 920 731 300
NAPS Norway A/S, Strandvein 50, N-1366
Lysaker, Norway
Tel: +47 67 112 550
Fax: +47 67 112 545
Solamatics (Pvt) Ltd., 31 Edison Road,
Graniteside, Harare, Zimbabwe
Tel: +263 4 749 930
Fax: +263 4 771 212
TATA BP Solar India Ltd., Plot No. 78,
Electronic City, Hosur Road,
Bangalore 561 229, India
Tel: +91 80 852 1016
Fax: +91 80 852 0116
Norcoast Refrigeration Co, 50 Grigor Street,
Caloundra, Queensland 4551, Australia
Tel: +61 7 9491 1849
Fax: +61 7 5491 7627
Website: http://www.norcoast.com.au
Sun Frost, PO Box 1101, 824 St Ste # 7,
Arcata, California 95518, USA
Tel: +1 707 822 9095
Fax: +1 707 822 6213
Practical Action, The Schumacher Centre for Technology & Development
Bourton Hall, Bourton-on-Dunsmore, Rugby, Warwickshire CV23 9QZ, UK
Tel: +44 (0)1926 634400 Fax: +44 (0)1926 634401 E-mail: infoserv@practicalaction.org.uk Web: http://www.practicalaction.org
Intermediate Technology Development Group Ltd Patron HRH - The Prince of Wales, KG, KT, GCB
Company Rag. No 871954, England Rag. Charity No 247257 VAT No 241 5154 92
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English |[gsdl?e=d-00gtzinti---000--1-0--010---4----0--0-10l--1en-5000---50-about-0---01131-0011T7%2eCNJnXc0a8012f0000057844f1611d-0utfZz-8-0-0&cl=CL2.1.5&d=Js7742e&az=A>=2&gc=&ihs=0&l=fr&az=A&p=about French ]|[gsdl?e=d-00gtzinti---000--1-0--010---4----0--0-10l--1en-5000---50-about-0---01131-0011T7%2eCNJnXc0a8012f0000057844f1611d-0utfZz-8-0-0&cl=CL2.1.5&d=Js7742e&az=A>=2&gc=&ihs=0&l=es&az=A&p=about Spanish ]
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