Dynamic optimization and thermo-economic assessment of a solar parabolic trough combined heat and power system with thermal storage: A case study

Abstract

The solar-driven combined heat and power system provides an efficient and green approach for the energy demand in remote areas. In this study, a two-tank molten salt thermal storage system is coupled with solar parabolic trough collectors and feeds an organic Rankine unit that produces electricity and heating. Specially, the organic Rankine unit can operate in off-design conditions following the end-user electricity load demand. The configuration of the complete system is parametrically investigated and dynamically optimized aiming to identify the operating conditions for which the net present value is maximized. The optimal arrangement for Lhasa is found to be a 1175-m2 solar parabolic trough field and two 50-m3 molten salt storage tanks. The monthly results show that this optimal case is able to run uninterruptedly the whole month in November and December with a 100% monthly electricity supply reliability rate. Furthermore, the application of this system for typical cities in western China is optimized and compared. The best economical location for the apparatus is in Ejinaqi, with a maximum net present value of 1471 thousand dollars, of which carbon reduction benefit account for 8.8%, and the payback period is only 5.4 years. Moreover, the yearly energy efficiency, exergy efficiency, electricity supply reliability rate and solar abandonment rate for optimal case of Ejinaqi are 55.0%, 20.2%, 93.9% and 25.4%, respectively. The study demonstrates that the proposed apparatus can be a promising option to provide energy for remote areas faced with poorly power grid.