Optimal integration of Rankine cycles in concentrated solar power plant

International audience An optimization method derived from the finite size/time thermodynamics is extended for irreversible engine cycle. Combining equivalent cycle concept and thermodynamics of irreversible processes allows solving analytically the problem of optimal integration formerly defined by Chambadal and Novikov. For given source and sink temperatures, and given output power, optimal operating conditions is searched for minimizing the investment cost. Equivalent cycle concept is first detailed. It leads to express two thermodynamic constraints (energy and exergy balances) according to the equivalent temperatures characterizing the equivalent cycle and the so-called exergy conductances. The cost function is also expressed according to these exergy conductances. Applying the KKT conditions gives the optimal equivalent temperatures and optimal conductances, and thence the optimal exchanger areas and actual operating temperatures for the optimal cycle. The method is then applied to the optimal design of a concentrated solar power plant under study at 2iE (International Institute for Water and Environmental Engineering, Ouagadougou, Burkina Faso). For CSP design, this method only requires 3 parameters: the direct normal irradiance, the concentration factor and the cold sink temperature. From these three parameters, a water steam system is designed.