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With the increasing demand for energy throughout the world, the environment around us is getting severely affected. The conventional energy sources (coal, oil and gas) are unfortunately the biggest polluters of the environment. The aforementioned energy sources emit greenhouse gases like carbon dioxide and methane, which are responsible for global warming and ozone layer depletion. The only feasible answer to this problem is to reduce the use of the conventional energy sources and focus more on other energy sources. The renewable energy sources (solar, wind and hydro) have been present in nature, but the technology to harvest these energies have always been relatively expensive until recently. The biggest advantage of using renewable energy sources is the fact that these energy sources will never run out and they also do not pollute the environment as their more conventional counterparts. With more research being conducted into better ways of storing the power trapped from the renewable energy sources and the relative difficulty of obtaining the ever-depleting conventional energy sources, the future for renewable energy sources definitely looks better than at any time in the past

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Almost all the domestic water in Brazil is heated with an electrical heater directly by the end consumer. A typical heater has an effect of 5 400 W and when the whole population takes a shower in the evening it causes big peaks in the electrical grid. This consumption peaks could be reduced by simple and cheap solar collector system. Different system technologies and the most important parts of a solar collector system are described in the technical background. In Lajeado almost every system is a self-circulated system because of the simplicity and the lower costs. Solar cooling as an alternative to the vapor compressor chillers has been studied. The cooling demand is biggest when the sun shines; this makes the sun perfect as a source to cooling. The ab- and adsorption chillers as a method in the future have been discussed in this paper; however it has only been studied briefly because small scale chillers using the technology can not be found on the market yet. A number of different systems have been dimensioned after the existing conditions of Lajeado, the town where the project has been carried out in. Prizes and costs for both installation and materials come from the local solar collector supplier. With this as a background; several systems for various hot water demands has been dimensioned and costs and repayment time been calculated. A study of all the systems shows that, if the hot water demand increases and the systems get bigger, the profitability grows and the repayment time becomes shorter, down to three years. In almost every case the repayment time was under eight years, which makes solar heating attractive and the profit is good for the southern Brazil.

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Transparent semiconducting oxide films of ITO have been deposited using screen printing techniques for fabricating heterostructure solar cells. The ITO material used is a readymade combination of organometallic compounds of indium and tin, dissolved in a suitable organic vehicle to make a screenprintable ink or paste. The paste is then printed onto substrates in the desired configurations. The effect of various firing temperatures, from 450°C to 650 °c, on the film properties were observed. The sheet resistances, Ra, changed as the firing temperature varied. Ra values could be decreased by annealing the films in an inert gas or in vacuum conditions. An annealing temperature of 300°C seemed to be optimum for annealing the ITO films. This decreased the sheet resistance by a factor of more than ten. The lowest sheet resistance of the ITO films was about 290 n/sq, measured during annealing under vacuum conditions at a temperature of 300 °C. This gradually increased up to about 1 Kn/sq after the film was aged for a few days in a laboratory atmosphere. The solar cell structures of ITO/p-Si and ITO/Sn/p-Si were made in this research. The first structure suffered from an excessive oxide interfacial layer thickness and it was abandoned. The second structure was then made to overcome the problems resulting from the interfacial oxide. The Sn layer was produced by using evaporation prior to the screen printing of ITO. The thickness of the Sn layer was about 100 nm. After evaporation, screen printing methods were used to complete the heterostructure solar cell. The best typical values of these cells are, open circuit voltage, V~= 0.360 Volt, short circuit current density, Jsc= 16.4 mA/cm2 with fill factor, FF = 0.34 and efficiency, 1) = 2.5% under 80 mW/cm2 simulated illumination, where this illumination is equivalent to air mass 2, (AM2).

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