Allocating electricity production from a hybrid fossil-renewable power plant among its multi primary resources

• We propose two methods to allocate the power produced in hybrid facilities among the different input resources they consume.
• The methods identify what share of the power produced in a solar-fossil hybrid facility can be considered renewable.
• One allocation method is statically based on prescribed reference efficiencies of non-hybrid power production.
• The other allocation method is adaptive and self-tuned to the local energy scenario.
• Differences between the two methods become important as hybridization gains large fractions of the local energy scenario.

The interest in hybrid power production facilities, based on the integration of renewable resources and conventional fossil fuels, is rapidly rising. The question of what fraction of the electricity produced in such facilities is to be considered as produced from the renewable resources is still being debated. We show that the conventional Fossil-Centered-Solar-Share method and the Exergy-based method lead to unfair allocations that may result in unfair access to subsidies granted to renewable electricity. We propose a more balanced Single-Resource-Separate-Production-Reference (SRSPR) allocation method based on prescribed reference partial primary energy factors chosen by some authority to represent reference efficiencies of non-hybrid power production from the same renewable and fossil resources used by the hybrid facility. We then show that as hybridization gains higher fractions of the local energy market, the SRSPR method may still result in somewhat unfair allocations leading to local market distortions. To overcome this drawback, we formulate a more consistent Self-Tuned-Average-Local-Productions-Reference (STALPR) allocation method whereby the electricity allocation fractions are based on the average partial primary energy factors of the actual energy portfolio of the local area that includes the hybrid plant itself. Results are illustrated with reference to a solar-integrated combined cycle facility.