Aerostat for Solar Power Generation

Abstract

One of the major issues in the use of ground based photovoltaic (PV) panels for the large scale collection of solar energy is the relatively low energy density. As a result a large area is required on the ground to achieve a significant production. This issue is compounded by the fact that the power output of the devices is strongly dependent on the latitude and weather conditions. At high latitudes the sun is relatively low on the horizon and a large part of the solar energy is absorbed by the atmosphere. Countries situated at high latitudes, with climates such as the UK, are therefore challenged in thei r exploitation of solar energy as the average number of Peak Solar Hours (P SH - numerically equal to the daily solar irradiation in kWh/m2) is relatively low. In Europe, typical annual average PSH values for horizontal surfaces range from about 2.5 h in northern England to 4.85 h in southern Spain (Markvart & Castaner, 2003). As, roughly speaking, the cost of the energy produced is inversely proportional to the average PSH, northern European countries are at a considerable economical disadvantage in the exploitation of solar energy with respect to other regions. On the other hand, areas with high ground solar irradiations (e.g. African deserts, see Kurokawa, 2004) are remote from most users and the losses over thousands of miles of cables and the political issues entailed in such a large project, severely reduce the economic advantages. A different approach to address most of the shortcomings of ground based solar energy production was proposed by Glaser et al., 1974 and his idea has captured the imagination of scientists up to this day. The basic concept was to collect solar energy using a large satellite orbiting the Earth. This satellite would be capable of capturing the full strength of the solar radiation continuously and transmit it to the ground using microwave radiation. The receiving station would then convert the microwave radiation into electric energy for widespread use. The original concept was revisited in the late 90’s (Mankins, 1997) in view of the considerable technological advances made since the 70’s and research work on this concept is still ongoing. However a mixture of techni cal issues (such as the losses in the energy conversions and transmission), safety concerns (regarding the microwave beam linking the satellite with the ground station) and cost have denied the practical implementation of this concept. The latter is a substantial hurdle as the development of Satellite Solar Power (SSP) cannot be carried out incrementally, in order to recover part of the initial cost during the development and use it to fund the following steps, but it requires substantial funding upfront (tens of billions of dollars according to Mankins, 1997) before there is any economical return.