CRS and biomass hybrid power plants performance
The LCOE for the CRS base case is 0.23 €/kWh and the best base case LCOE is the WWTP (+)-MK 801 digester with 0.08 €/kWh. For biomass integration into the air cycle of a CRS, the lower LCOE options are the hybridization of a 4 MWe CRS using an atmospheric volumetric receiver with biogas from a WWTP or with natural gas (LCOE of 0.15 €/kWh), with landfill gas (LCOE of 0.16 €/kWh) or with wood residues gasification (LCOE of 0.17 €/kWh). Different results would be obtained for the hybrid systems if different CRS technologies are used. Because the Portuguese bonus feed-in tariff is calculated for each renewable energy technology, some of these power plant configurations have negative economical turnovers. The hybrid power plant investment with best payback period is the hybridization with an anaerobic digester, using sludge from a waste-water treatment plant. This power plant returns the investment in 13 years (sludge collection and transport assumed without cost), presenting also the best net present value (15 million euro). However, for the 4 MWe scale, WWTP or landfill biogas would only be possible close to large cities (few limit cases) with centralized plants capable of generating sufficient quantities of sludge or MSW. A different biomass CRS hybridization technology (which can be applied in a larger number of cases) that presents favourable LCOE is the gasifier working on wood residues (WG#CRS#1 - LCOE of 0.17 €/kWh), which can reduce the biomass consumption by 11,000 tons per year compared to the base case, making biomass gasification economically viable to operate under the Portuguese scenario, despite having a low attractiveness, with an IRR of 5.5% and an NPV of 3.3 million euro.