A perspective on the potential role of renewable gas in a smart energy island system

This paper examines the potential role for Power to Gas (P2G) as applied to an island energy system with high levels of renewable electricity penetration. P2G systems require both a supply of green electricity and a source of CO2. Cheap electricity is essential for a financially sustainable P2G system. Using a PLEXOS model it was determined that deploying 50 MWe of P2G capacity on the 2030 Irish electrical grid may reduce absolute levels of curtailed wind by 5% compared to the base case. CO2 capture is expensive. The cheapest method of sourcing CO2 for a P2G system is to employ a methanation process whereby biogas from anaerobic digestion is mixed with hydrogen from surplus electricity. Anaerobic digestion in Ireland has a potential to produce biomethane to a level of 10.2% of energy in transport (19.2 PJ/a). The potential CO2 resource from anaerobic digestion could allow for a further 8.9% of energy in transport (16.6 PJ/a) from P2G production. An optimal model is proposed including for co-location of a biogas system with a P2G system. The model includes for demand-driven biogas concepts allowing electrical grid balancing and the supply of gaseous transportation fuel. Biofuel obligation certificates allows for a financially viable industry.