Economic analysis for the selection of low temperature solar thermal utility systems

Abstract

• Methodology for the design and selection of low temperature solar thermal systems. • FPC, CPC and PTC technologies are analysed. • Selection based on the present value of the life cycle savings. • The PTC technology gives the largest life cycle savings. The supply of low temperature heat to a process plant can be accomplished using different types of solar thermal technology such as Flat Plate Collectors (FPC), Compound Parabolic Collectors (CPC) or Parabolic Trough Collectors (PTC). These technologies differ in the surface area required, the initial investment cost and the number of hours in the day they can provide the required heat duty to replace the use of fossil fuel. Out of these technologies, the PTC proves to be the most convenient in the lifetime horizon despite the large initial costs either for low or for medium temperature applications. This is demonstrated using the net present value of the life cycle energy savings. It is shown that for a process with a heat duty of 700 kW, supply temperature of 130 °C and assuming the lowest solar radiation, the PTC requires a surface area of 3191.76 m 2 giving a life cycle energy saving of 1967089.32 USD and a payback of 3 years. For a case with 400 kW and supply temperature of 70 °C, the PTC remains the best option with a surface area of 1768.42 m 2 and a life cycle energy saving of 1085939.35 USD and a payback of 4 years.