How Does a Resilience Energy Cell Affect Local Grid Imports, Renewable Curtailment And System Balancing?

Sammanfattning

The integration of variable renewable generation into rural distribution networks creates structural mismatches between local generation and demand, resulting in curtailment of surplus electricity and continued reliance on grid imports. The Resilience Energy Cell (REC) concept addresses this challenge by combining ground-mounted photovoltaics with biogas-derived biogenic CO₂, electrolysis, methanation, seasonal synthetic natural gas (SNG) storage, and combined heat and power (CHP) within a geographically bounded community. This thesis evaluates the technical performance of a REC in the Bavarian municipality of Vohenstrauß through energy system simulation in HOMER Pro, using locally derived data on installed PV capacity (16,084 kWp), biogas capacity (2,340 kW), and hourly demand and generation profiles for the reference year 2025. Three scenarios are compared: a baseline without flexibility assets, a REC with a 1,500 kW electrolyser at current installed PV capacity, and a design-scale REC with 50,000 kWp PV and a 6,000 kW electrolyser. The REC scenario with a 1500 kW electrolyser reduces renewable curtailment by 59.5% but increases annual grid imports by 11.0%, reflecting a substitution effect in which the electrolyser captures PV generation that would otherwise have served the local load, intensified by the 19.3% round-trip efficiency of the Power-to-Gas-to-power chain. When recoverable waste heat from the electrolyser, methanation, and CHP stages is accounted for, the total system efficiency of the Power-to-Gas chain rises from the electricity-only round-trip value of 19.3% to approximately 93.6%, reframing the REC as a near-complete energy converter rather than a poor round-trip electricity converter. The REC scenario at design scale, in which surplus exceeds the electrolyser intake by a wide margin, reduces grid imports by 23.9%, achieves a self-sufficiency ratio of 50.5%, and delivers the lowest levelised cost of electricity ($0.055/kWh) and CO₂ emissions (2,559 t/yr) of all three configurations. The results identify a renewable-surplus threshold below which REC deployment increases rather than decreases grid dependence. For Vohenstrauß, reaching design-scale performance requires either substantial PV expansion or the addition of wind generation, with the latter option historically constrained by the Bavarian policies. Component sizing must therefore be derived from site-specific surplus profiles rather than generic REC design specifications. The thesis concludes that the REC concept is technically sound, but its viability is fundamentally bounded by local renewable surplus availability, with direct SNG injection into the existing gas distribution network identified as a more efficient end-use pathway for heat decarbonisation.