ORC schematics

ORC thermodynamic cycleA solar ORC engine uses an organic working fluid (e.g. a HFC or hydrocarbon-based refrigerant) instead of water/steam as in the conventional Rankine power-cycle. The thermal energy needed to evaporate the working fluid is provided by solar thermal collectors. The heat rejected during de-superheating and condensation may also be used for useful downstream processes such as water heating.

Modelling and optimization using UK climate data

Schematic of the modeled ORC

The performance of renewable energy (and particularly solar power) systems can vary significantly with location. In order to optimise the design of a solar combined heat and power (SCHP) system for the UK, a dynamic system model was constructed in MATLAB (Freeman et al. 2015). The model allows the various system configurations to be simulated under a realistic climate conditions. The results of the annual simulation are used to select an appropriate working fluid and evaporation temperature for the ORC engine.



Optimization for the selection of the working fluid 

Experimental system

An ORC rig was constructed in the CEP lab in order to characterise the performance of all system components over a wide range of operating conditions. Heat input is provided by an electrical oil heater, mimicking the thermal output of a solar thermal collector array installed on the roof of the Department.

Flow chart of experimental ORC system

full screen

 Relevant publications

Freeman, James, Klaus Hellgardt, and Christos N. Markides. "An assessment of solar-powered organic Rankine cycle systems for combined heating and power in UK domestic applications." Applied Energy 138 (2015): 605-620. (pdf)

Freeman, James, Klaus Hellgardt, and Christos N. Markides. "An Assessment of Solar–Thermal Collector Designs for Small-Scale Combined Heating and Power Applications in the United Kingdom." Heat Transfer Engineering 36.14-15 (2015): 1332-1347.