Until very recently, energy supply of the world has been treated as being nearly inexhaustible. Nowadays about 90 percent of the energy used is obtained from non-renewable resources: oil, natural gas, coal and uranium. These resources are being used up at an alarming rate. To meet our demands we are now searching for new sources of energy. One of these new sources of energy is solar energy which will assume increasing importance. It is free but means must be developed to use it economically. Research is actively under way to reduce the storage cost of this low intensity energy and for the design of economical systems. The purpose of this Institute is to provide an international forum for the dissemination of information on solar energy utilization: fundamentals and applications in industry. This meeting is primarily a high level teaching activity. The subject is treated in considerable depth by lecturers eminent in their field. The other participants include scientists, engineers, and senior graduate students who themselves are involved in a similar research and who wish to learn more about current developments, as well as scientists from other areas who are planning to research on solar energy. The lectures are supplemented by informal discussions designed to encourage the free and critical exchange of ideas. A limited number of contributions are also included. This volume contains both basic and applied information contributed during the Institute. The editors appreciate the cooperation of Martinus Nijhoff Publishezsin making the proceedings widely available.

Energy Storage not only plays an important role in conservinq the energy but also improves the performance and reliability of a wide range of energy systems. Energy storagp. leads to saving of premium fuels and makes the system morA cost effective by reducing the wastage of energy. In most systems there is a mismatch between the energy supply and energy demand. The energy storage can even out this imbalance and thereby help in savings of capital costs. Enerqy storage is all the more important where the enerqy source is intermittent such as Solar Energy. The use of jntermittent energy sources is likely to grow. If more and more solar energy is to be used for domestic and industrial applications then energy storage is very crucial. If no storage is used in solar energy systems then the major part of the energy demand will be met by the back-up or auxiliary energy and therefore the so called annual solar load fract]on will be very low. In case of solar energy, both short term and long term energy storage systems can be used whjch can adjust the phase difference between solar energy supply and energy demand and can match seasonal demands to the solar availability respectively. Thermal energy storage can lead to capital cost savings, fuel savjngs, and fuel substitution in many application areas. Developing an optimum thermal storaqe system is as important an area of research as developinq an alternative source of energy.

Several hundred technically acceptable PCMs were identified in Volume I of this set, and some of their thermodynamic and physical properties were present. Out of these, practical considerations have reduced the list to a few commercial PCMs for solar energy thermal storage heating and cooling applications. In Volume II these PCMs and their technology and discussed.