This book reviews recent advanced research work in the area of flat plate collectors, solar distillation, greenhouse technology for crop drying and production and solar electric/ thermal (PV/T) systems. The basic working principle, energy balances, thermal modelling, energy and economic analysis will be discussed. An instantaneous and overall efficiency of each solar thermal and electric system are also discussed and their results compared for economic analysis. Basic knowledge of availability of solar radiation is discussed in the beginning. Life cycle cost analysis, which includes initial investment, operating cost, interest rate, salvage value and annual power output, has been considered. An energy pay back time (EPBT) for solar electric/ thermal (PV/T) system has been evaluated by evaluating embodied energy during production of solar cell, PV module and balance of system (BOS) and useful both electric and thermal energy. Thermal energy from PV module can be in the form of sensible heat either for water or for air heating system.