Evaluation of some renewable energy technologies

Purpose. The study aims to outline and compare various renewable energy alternatives in view of the global warming crisis and depletion of fossil fuels which cause emissions of carbon dioxide. Carbon dioxide is a major source of pollution and is an absorbent for radiation. Methods. Literature surveys and analysis of benefits and drawbacks of the competing technologies should include the capital costs, running costs and carbon footprint. Liquid fuels have high energy to weight ratio compare to say solar panels or thermal absorbers, but what is neglected is the large refinery and other processing machinery behind the liquid fuel which is adding to the carbon footprint. Findings. Producer gas and bacterial engines are suggested as possible pollution reducing and cost effective methods for power generation. Coal, biomass, geothermal and hydroelectric have the lowest running cost, but carbon footprint cost is neglected. Solar chimneys, with low mechanical efficiency have low running costs, and no pollution. Modification of internal combustion engines to use producer gas and alcohol may reduce overall carbon footprint. Originality. Many researches focus on energy and mechanical efficiency. Bacterial engines have yet to be fully developed, and these are wonderful chemical factories but not understood in terms of classical thermodynamics. For all technologies, return on investment is more appropriate since capital costs are also included, which are neglected in mechanical efficiency calculations. Practical implications.Depletion of forest cover which acts as a greenhouse gas sink contributes to global warming. Worldwide, million of cars with internal combustion engines consuming petroleum, if converted to alternative fuels, can help in reducing the carbon gas emissions and ultimately to a slowdown in the global warming rate