This research project deals with the development of a methodology to analyse and design photovoltaic-based power systems. A microcomputer-based interactive photovoltaic (PV) performance analysis package has been developed. This package can be used for screening analysis of various sites, module characteristics and system configurations. Basic elements of this package include: ( i) resource assessment; ( ii) site analysis; (iii) technology assessment; (iv) optimization and choice of system configurations; and (v) life-cycle cost analysis. The resource assessment part of the package is used to estimate the hourly, daily and monthly global horizontal, fixed tilt and one-axis tracking insolation for any site under cloudless sky condition. Site elevation, latitude, longititude and Julian date information are used for this purpose. This insolation level determines the upper limit of possible irradiance at the site under consideration. This value can be adjusted on the basis of climatic conditions (e.g., occurrences of cloudy days and rainfall) prevailing in the area. The site analysis deals with the site's economic and environmental evaluation. The parameters involved in these evaluations are the total land area, the effective area of the site, the area of forest destroyed, the loss of use of the site, the total number of people who are affected by the project, the number of people who benefit from the project, and the purchase price of the site. The technology assessment part of the package deals with the process of creating electricity from solar energy. The D.C. power output of the array is determined by using the global irradiation, the manufacturer-supplied efficiency and dimensions of the module, and the total area of the array. The A.C. power can also be evaluated depending on the power conditioning unit (PCU) efficiency. The optimization and the choice of the system configuration part of the package is used for determining the most optimum use of the candidate site in terms of land availability, land cost and the best possible mix of various PV modules for optimizing the cost of the PV energy within the existing constraints. Finally a life-cycle cost analysis is performed which includes cost of operation, cleaning, maintenance, spare parts, tilting, module, module support, inverter, charge controller, backup system and energy storage. It also takes into consideration the lifetime of the inverter, charge controller, the module, the backup system and the energy storage system. This package has been applied to analyse the performance of various PV modules in two locations. One of the biggest advantages of this package is that it is based on TURBO PASCAL language and runs on the IBM-PC and compatible microcomputers. Thus it is very portable from one operating environment to another, and users can be trained in its application quite easily. / M.S.