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Photovoltaics: What, Where, Who......!!!!!
Charles E. I. Yousif
What......is Photovoltaics:
Photovoltaic is a word that combines light (photo) with electricity (volta), and it implies the direct conversion of sunlight into electricity. It is usually abbreviated as PV. This conversion can be achieved by using solar cells which are mainly made up of a semiconductor mixed with certain impurities. The photovoltaic effect was first reported in 1839 by the French Scientist, Becquerel. However, the first practical solar cell was manufactured by Bell Laboratories in the U.S.A., which was used as an electric power source in spacecrafts. Nowadays, commercially-available cells are usually made of silicon, connected together and sealed in glass to form a plate, known as a solar module. The power output from one solar module ranges from a few Watts to over 100 W each. Such PV modules are used all over the world to supply electricity in remote areas. They have found a niche market in providing power to many electric products such as watches, electric torches and calulators and more recently, in cladding of buildings, where the modules could replace traditional building materials and at the same time produce electricity for the building, thus reducing its electricity bill.
Solar PV modules are sometimes mistaken for solar collectors that are used in solar water heaters. A commercial solar module is mainly made up of thin wafers of silicon solar cells connected together. On the other hand, a solar collector is made up of a number of copper or stainless steel pipes, painted with a special black coating, connected at top and bottom with larger header pipes, insulated all around, covered with a glass plate on top and encased in a box. It is important to note that it is economically and technically wise to heat water using this solar collector rather than to produce electricity first from the solar PV module and then use an electric element for heating water.
Where......are we?
In Malta, different solar PV systems were first installed and tested at the Institute for Energy Technology, University of Malta, Marsaxlokk. The Institute has lately been investigating the performance of a roof-top grid-tied photovoltaic system. Such a system mainly consists of solar PV modules placed on the roof of a building and an inverter that converts and amplifies the d.c. electricity produced to the required a.c. output. The electricity could be directly utilised at the point of generation or exported to the grid. In cases when the electricity produced is not enough, power can be imported from the grid.
The Institute believes that such systems will eventually become another option to supplement the electricity demand in Malta. The reasons behind this vision are infinite, however, it is enough to mention the fact that Malta is an island with no natural resources except the sun and the wind, that remain un-exploited so far. The cost of electricity has now been raised to reflect more its true cost of generation on the island and it could become more expensive in the future, to cover the social costs of electricity generation as well. Social costs include the side effects of producing electricity such as air and sea pollution, noise pollution and health hazards to human beings, damages to flora and fauna,.negative effects on stones used in buildings and historical sites.
In order to be able to implement the right technology in the right place and time, technical testing of such systems had to be carried out well in advance. The Institute had started testing 5 years ago and so far we have come up with valuable results that are specifically suitable for the Maltese climate. Once the energy legislation is modified to allow grid-connection in Malta, the Institute will be the first to offer its practical know-how for the good of all citizens.
The first photovoltaic system to be tested was a stand-alone system with battery storage (1993-1995). Tests were carried out for 2 years in accordance with the European Union Standards set by the Joint Research Centre - Ispra Establishement. This system was mainly made up of 20 solar modules, placed on one of the roofs at the University of Malta, a bank of batteries that were charged by the solar electricity and a set of 25 lights, which were lit up every night. Such systems are only relevant for remote sites where the cost of extending the grid is too expensive or for stand-alone applications such as street lighting, where the high cost of trenching and laying of cables renders this option as cost effective.
A more relevant application that suites Malta is grid-connection, as explained above. Such a system is also being tested at the Institute and the results of its first year of operation shows that for an area of approximately 10 m² of solar PV modules placed on the roof, one expects to produce at least 1400 units of electricity annually, which could cut down on the electricity bill of a normal house by up to 40%, depending on consumption. Such a system would cost Lm 3500 but it should further decrease with higher demand.
Who......benefits?
Besides the benefit that the individual gets of lowering one’s electricity bill, de-centralised roof-top PV systems help create a sense of electricity conservation, since it would be in the interest of the individual to make maximum use of the generated solar electricity. Moreover, as one becomes more aware of the value of electricity, more efficient electric appliances will be preffered, resulting in a better quality of products in the local market.
In order to produce enough solar electricity to cater for 5% of the total national electricity consumption based on 1996 figures, one would require 47,815 m² of solar modules. This area can be satisfied if there are 4781 house-holds who are ready to install a 10 m² PV system on their roofs. This would also reduce the carbon dioxide emmissions by 66940 tonnes/annum and save at least 28690 tonnes of fuel oil every year, costing roughly Lm 2 million maltese pounds.
If every house in Malta would one day adopts such a grid-connected system, the result would be a huge amount of savings to the individual and to the country which will obviously translate into a better quality of life for everyone. Testing of the PV system will be concluded in June 1998, after which a final report would give sure guidance to the proper installation and expected output of such systems in Malta.
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