Power-to-Gas from curtailed RES electricity in Spain: potential and applications

Power-to-Gas (PtG) consists in electrochemical conversion of electricity into gaseous compounds, connecting electricity and gas infrastructures. The potential of PtG applications from curtailed electricity from wind and solar photovoltaic plants in the Spanish electricity sector is studied. The curtailed electricity data is obtained by the elaboration of the P48 dispatch program correction published by the Spanish TSO. Subsequently, electrolysis (alkaline and PEM), fuel-cell (alkaline, PEM and r-SOC) and methanation (catalytic Sabatier reactor) systems are sized in a cascading approach and the levelised costs of the final products (H2, electricity and CH4) are evaluated via a Techno-Economic Analysis. Also, an optimization of the Levelised Cost Of Hydrogen (LCOH) in function of the electrolyser capacity (kW) has been performed through a dynamic simulation in TRNSYS. Techno-Economic results show that hydrogen production (ALK or PEM) from wind curtailment is already competitive today (3.57-5.52 €/kgH2), together with its re-electrification (ALK or r-SOC) for self-consumption (around 0.2 €/kWhe). Other PtG pathways from wind curtailment such as re-electrification (ALK or r-SOC 0.22-0.25 €/kWhe) in the ancillary market and CNG from ALK (192.14 €/MWhSNG,HHV) are not far from competitiveness respect to their reference market price (0.15 €/kWhe and 172.41 €/MWhSNG,HHV respectively). Levelised costs of other wind coupled pathways (PEM fuel cell, CNG from PEM and CH4 injection) and all PV coupled configurations still need substantial support. Dynamic simulations show that under variable operating conditions the LCOH increases by 60-80% but the optimal electrolyser size is reduced by 20-30%.