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Photovoltaics on Rooftops:
Economically Feasible by the Year 2010
Charles E.I. Yousif
Last May, 25 students from James Madison University, Virginia, U.S.A. came to Malta to study and work on different projects that are of interest to the Institute for Energy Technology of the University of Malta. This programme of studies is a fruit of collaboration between the Institute and the College of Integrated Science and Technology of James Madison University, which has started in 1997.
One of the projects that were conducted this year, was that of the economic viability of building rooftop solar photovoltaic grid-connected systems in Malta. A solar photovoltaic system mainly comprises of solar cells that convert light into electricity and an inverter that transforms it to alternating current, which can then be fed into the national electricity grid. The generated electricity could be used immediately or sold to the electricity utility. In both cases, this would contribute towards lowering the electricity bill of the consumer.
By placing solar systems on rooftops, one avoids the use of land that is scarce and expensive. Moreover, the roofs in Malta are flat, which implies that the systems can be placed in such a way as to maximize their output.
Photovoltaic applications in Malta have so far been considered on a research level and for demonstration purposes only. The first and only rooftop grid-connected photovoltaic system in Malta is situated at the Institute for Energy Technology, Marsaxlokk. Between October 1996 and June 1999, this small system has produced 4200 units of electricity, which reduced the Institute’s electricity bill by 45%. This has also avoided burning 340 gallons of fuel oil at the power station, to produce an equivalent amount of electricity for end-use. Moreover, the use of this system has saved the environment 5220 kg of carbon dioxide, 86 kg of sulphur oxides, 5.5 kg of nitrogen oxides and 1.5 kg of particulate matter.
Besides the technical studies, the widespread applications of solar photovoltaic systems requires an analysis of the economic and social viability, as well as an energy dissemination plan that implements incentives to accelerate the use of such technology in Malta, both now and in the future.
Hence, this project was devised to analyse the life cycle costing of different photovoltaic grid connected systems for residential and commercial buildings and correlate the system size with the electricity price, the payback period and the required rooftop areas. Charts were produced to help predict future costs of different systems and to provide answers to frequently asked questions. A proposal has also been made for introducing regulations and guidelines for grid-connection. Such a move would be necessary before grid-connection would be allowed on a wide scale.
Two types of solar cells were considered, namely the traditional more efficient crystalline silicon solar cells that have a lifetime of more than 20 years and the less efficient but cheaper amorphous thin-film cells, that have a lifetime of about 10 years. Moreover, tracking systems that follow the sun throughout the day were also evaluated, as opposed to stationary flat plate systems.
Photovoltaic Applications, feasible by the year 2010:
Some of the results obtained indicate that solar electric systems could be economically feasible, when installed in the year 2010 and beyond. As the size of the system grows, the payback period decreases due to economies of scale. It is worth noticing that while amorphous thin-film cells tend to pay back faster, their lifetime is only about half of that of crystalline silicon cells. This implies that even though the initial price for a thin-film system could be lower, the net profit at the end of the system life would be lower. More importantly, this implies that unless the present technology of amorphous silicon advances dramatically, it will not be able to compete with the more traditional crystalline silicon cells.
Though photovoltaics may not currently have a good payback period, this does not imply that they should not be implemented today. PV works regardless of the economic effects, and is a viable energy supplement. By building systems today, the knowledge and experience gained from their operation can be applied to improve future use. Additionally, many things in which people invest their money today never pay back. For example, automobiles do not pay back, but that does not make them any less of a necessity or prevent people from purchasing them. Photovoltaics may become necessary in the future, and this would cause the economics of a system to become a secondary factor in deciding whether or not to purchase one.
As Malta strives to become a member in the European Union, regulations pertaining to energy generation and distribution in Malta will have to be changed to reflect the policies of the European Union, which would include generation of electricity from renewable sources of energy. On the other hand, regulations and standards will have to be set to safeguard the systems, the owners and the utility power lines. To date there are no regulations regarding independent power producers (IPP) in Malta neither there are any guidelines as to the standard methods for grid-connection. Some points that could be included in the regulations and guidelines have been tackled and a document has been prepared. Four main areas were mentioned namely, grid-connection and safety, technical considerations, protective equipment and system maintenance.
What About the Power Stations?
The report has highlighted three important points that need to be raised on the side of oil fired power plants.
· Rooftop decentralised photovoltaic systems as opposed to large photovoltaic plants, have the advantage of reducing variations at the power plants, which may be caused by overcast skies. A passing cloud over parts of the island would only affect that portion of the island while the other more sunny regions are able to produce power in the meantime.
There will be no loss of jobs in the power stations, due to the implementation of solar energy. The addition of PV cells on rooftops would only account for a maximum of about 15% of the overall electricity generation, due to limited areas of rooftops available. On the contrary, Enemalta would have the extra job of certifying and networking these systems to its grid.
· Using photovoltaics reduces peak loads caused by air-conditioning during summer, thus helping to relieve the load on the power station and improve the power factor of the grid.
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Why Should People Change?
According to the report, there is an urgency to shift to a “solar culture”. The international market of oil is very unstable due to price changes and political considerations. This possibility alone should make the use of renewable energy applications a necessity, thus shifting the economic considerations to a secondary level of importance.
In this case, a solar photovoltaic system that could supply more than half of the electricity needs of a family of four would cost Lm 3,500 today and would occupy 10 m˛ of roof area. It is worth mentioning that in order to promote the use of photovoltaic systems, a campaign on solar water heaters becomes a necessity. It is five times more efficient to heat water directly rather than converting solar radiation to electricity and then to heat.
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