High-temperature solar energy utilization after 15 years R&D: kick-off for the third generation of technologies

Abstract

Today we look back on 15 years of international research and development of solar tower, parabolic trough and parabolic dish technologies. Many countries have contributed to this effort. The market is growing. Some 300 MW e from solar thermal parabolic trough power plants are being fed into electric grids and doing peaking/intermediate load duty under commercial conditions. It is reported that several hundred additional megawatts are under contract or being planned. Approxomately 3–5 billion DM have been spent worldwide on R&D. Only the parabolic trouh power plants have managed to get beyond the R&D stage. Here the accumulated experience is about 1000MW e ×a (1989) power plant operating years. Solar tower and parabolic dish technologies still have to demonstrate their market readiness or are not yet at the pilot project stage. A consortium of European and USA companies is preparing an air-colled 30 MW e solar tower power plant, PHOEBUS, for Jordan. The foundations are being laid for high-temperature solar chemistry. Fifteen years after the initiation of research activities, the international community of scientists and engineers at work on solar thermal energy conversion needs a nwe perspective for the next 15 years in order to avoid technological gaps. There are even more incentives for this work than before: ♭ Over five billion people live on earth; six billion are likely in 2000. The population doubles in only 30 years now! All need to be fed and clothed, all of them need a roof over their head. Since by far the majority lives in or near the highly insolated parts of the world, solar energy utilization is a natural choice. ♭ Investments for energy supply are a significant economic factor. In 1986 they amounted to 320 billion US$ (not including countries with centrally planned economies), which is equivalent to 11% of the world's capital investments. In the future, the greatest demand for energy supply projects will be in the developing countries, most of which are located in the earth's sun belt. For these countries the World Bank estimates a need for annual power plant investments of over 100 billion US$ for the next 20 years. At present about 20 billion US$/a is being invested by the energy utilities, by development banks, and as a result of bilateral agreements. This leaves a balance of over 50 billion US$ for which new financing has to be found. ♭ The use of solar energy contributes only very marginaly, if at all, to environmental damage. Solar energy does not require energy raw materials and as a consequence does not prodcue any associated pollutants. Those aspects of solar energy technologies having effects on teh environment, such as land area, material and eneryg intensities, are becoming less and less relevant because of progress in R&D. ♭ By contrast, the finite nature of the fossil energy raw materials and their irreversible for quasi-irreversible damage to the environment are becoming ever more obvious. The atmosphere is burdened with 22.5 × 10 9 tons of anthropogenic CO 2 annually (198). There is no containment technology yet nor is an economically applicable one likely. Research and development for the third generation of solar thermal high-temperature technologies has to be started and carried out with perseverance, in international cooperation. It is hoped that the International Energy Agency (IEA) can once again provide the necessary protective climate. Examples for future projects are: ♭ lightweigth membrane heliostats, troughs and dishes; ♭ industrialized solarized prime movers in the several hundred kilowatt to a few hundred megawatt range; ♭ receiver-reactors for dishes; ♭ thermal/latent heat storage for intermediate-load duty solar thermal plants; ♭ advanced air-cooled or direct particle absorption receivers; ♭ direct solar water vaporization receivers/loops. This paper views the state-of-the-art of high-temperature solar thermal energy conversion, raises questions about the relevant future technologies, outlines appropriate organizational and management structures, and estimates the financial requirements and the time scale.