Overall methodology and work performed
An overall decomposition-based methodology (figure "overall_methodology") has been proposed (D2.2) to provide a rational techno-economic evaluation of the W2G plants. WP1 (steps 1-2) defined critical boundary conditions for the optimization problem by investigating the theoretical grid-flexibility needs and waste availability. WP2 (step 3-6) investigated the concept realization and plant design, and defined case studies, and evaluated their economic feasibility, represented by plant CAPEX threshold, i.e. the maximum-possible plant CAPEX levelized to the reference stack (defined as a stack with 64*80 cm2 active cell area). WP3 (step 7) identifies economically potential business cases and the conditions preferred, based on potential case studies from WP2, and the upscaling strategy and technological bottlenecks.
Results
Grid-flexibility needs 2030 (figure "w2g_flexibility_needs"): The selected renewable energy sources (RES) dominated zones, i.e. DK-DK1, DK-DK2 and IT-SUD, all showed significant theoretical grid flexibility needs. Capacity wise, three RES dominated zones has significant UP and DOWN regulation needs, reaching several to even tens of GW level; while energy wise, the three zones present annual excess electricity of 5-7 TWh.
Waste availability 2030 (figure "w2g_biomass_availability"): Total energy of theoretical grid flexibility needs is at the same magnitude of the energy of local available waste and biomass. Since actual W2G contribution will be much less than the theoretical grid flexibility needs, local waste & biomass is sufficient to drive W2G for grid services.
Optimal plant design (figure "w2g_plant_design"): A set of optimal designs with trade-off performances were obtained. High efficiency has been enabled for all modes: 42-60% (PowGen), 60-75% (PowSto) and 37-53% (PowNeu). PowGen &PowSto efficiencies are much higher than state-of-the-art biomass-to-power (30%) and biomass-to-methane (65%). PowNeu mode is an efficient productive alternative of non-productive stand-by.
Economic feasibility (figure "w2g_economic_feasibility"): Economic feasibility of case studies can be enhanced by increased annual PowGen&PowSto hours of the plants installed. Feasible business cases are found with annual PowGen&PowSto operation of over 3500 hours and a stack CAPEX of less than 1600 €/kWe-SOFC, even given the current economic circumstances (grid-balancing price 40 €/MWh, SNG price 0.8 €/kg). The plant size preferred is with biomass feed of up to a few hundreds of MWth (equivalent to PowGen power up to 100 MWe, PowSto power up to a few hundreds of MWe).
Dissemination and exploitation:
- A publishable and sharable brochure with easy and concise results has been prepared as a media for all partners to advance the results exploitation.
- DG Ener, FCHJU and biomass community: Promote stage-wise component and system development towards modular system design approach enabling smooth mode switch for flexible plant operation and sufficient characterization of system dynamic response.
- Major EU TSOs and EU electrical grid community: Promote pioneer evaluation of technical feasibility of using separate SOFC and SOEC systems for grid-balancing service. Determine the types of grid-balancing services and the priority of using biomass for grid-balancing service.
- Biomass community and policy maker: whether W2G concept could be a better option of biomass utilization among various ways of using them. Potential subsidy for W2G concept.
- Solid-oxide technology community: Promote the awareness of the need of several tens of MW SOFC system as an important scenario of technology development. Increase the interest in technology scale-up for MW level above, and to enhance more robust stacks.
