terrestrial photovoltaics yield about 1 kilowatt while a rectenna would deliver 5.5 kilowatts. This is a factor of 5.5 in favor of WPT on a land usage basis. Wind has proven itself as a viable renewable source of electricity provided you have a baseload generation capability and transmission network in place. The Altmont Wind Farm in Northern California has experienced over a 40 % reduction in power generated over the last two years due to changes in the weather patterns. Biomass in three different forms is being used to provide energy. The first is the most direct and is the harvesting of wood for cooking purposes. In 1992 in South Africa alone more than 10 million trees were cut down in order to provide fuelwood. In more arid areas not only are trees being harvested but also brush with the result that the land is de-nuded and gradually turns into desert. The environmental consequences of this approach are well known. However what is not well appreciated is that once a desert, especially a large one, is created the changed environmental parameters, albedo, soil moisture, thermal convection and wind patterns etc. are such that the system becomes stable as a desert and to change a stable condition requires a great deal of effort and energy over a long time. The next most direct method of utilizing biomass is the burning of dung and/or harvesting roots. Both of these deprive the soil of nutrients. While the use of dung or buffalo chips as they are know in the US, have a long history and provide, for cities in India at least, a sanitary way of waste disposal it is only recently that the effects of this practice on crop production have been well understood by researchers. Without an alternative source of energy and an education program, this practice will not change and soil fertility will continue to decline. Growing roots for cooking not only robs the soil of nutrients but also result in disturbing the soil, which promotes loss of soil moisture. Finally there is the production of alcohol by fermentation. Both Brazil and the US as well as other countries have used alcohol as an alternative to gasoline. In Brazil it is used directly as fuel in modified cars where as in the US it is blended. Advocates often over look the implications of wide spread expansion. In Brazil they are leading to the burning of the rain forests in order to come up with the land on which to grow feed stock for the fermentation vats. In the US the process has in the short run provided an outlet for surplus corn corps. The long range question is how much land shall be devoted to food and how much to fuel. In countries where there is already a food shortage and poor soils the growing of vegetable matter for brewing alcohol is probably not a viable option. Several conclusions can be drawn about renewables when the scenarios are pushed to a logical end. Renewable methods of generating electricity offer cost avoidance if a nation has a well established, robust grid for supplying baseload power and absorbing power from alternate sources. Some renewables such as photovoltaics fill a viable need for power for irrigation pumps in remote locations. However the installation of TPV has resulted in making the extension of transmission lines uneconomical thus limiting the potential for further improvement in the quality of life.
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