A perspective on the potential role of renewable gas in a smart energy island system Eoin P. Ahern a, b, c , Paul Deane a, c , Tobias Persson d , Brian  O Gallach  oir a, c , Jerry D. Murphy a, b, c, * a Environmental Research Institute, University College Cork, Ireland b Science Foundation Ireland (SFI), Marine Renewable Energy Ireland (MaREI) Centre, Ireland c School of Engineering, University College Cork, Ireland d Energiforsk AB e Swedish Energy Research Centre, Sweden article info Article history: Received 22 August 2014 Accepted 21 January 2015 Available online 11 February 2015 Keywords: Biogas Carbon capture Electricity storage Transport biofuel Power to Gas Demand driven biogas abstract 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 CO 2 . Cheap electricity is essential for a financially sustainable P2G system. Using a PLEXOS model it was determined that deploying 50 MW e of P2G capacity on the 2030 Irish electrical grid may reduce absolute levels of curtailed wind by 5% compared to the base case. CO 2 capture is expensive. The cheapest method of sourcing CO 2 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 CO 2 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. © 2015 Elsevier Ltd. All rights reserved. 1. Introduction 1.1. The challenge of increasing levels of renewable electricity 1.1.1. Renewable electricity capacity as a proportion of demand For many countries, particularly those in Western Europe, wind is expected to play a very significant role in meeting their renew- able electricity targets. Fig. 1 shows expected installed wind ca- pacity as a proportion of minimum demand in summer 2020. Even with interconnection, Ireland and Spain will, at times, have in excess of 100% of demand available from wind, meaning curtail- ment will be required. Looking to 2030 and beyond, renewables will play an increasingly large role in energy systems globally, creating serious technical challenges. Ireland is located on the Atlantic coast of Europe and presents a very interesting case study, as it is an island grid with very high levels of wind penetration. The Republic of Ireland, in 2030 is ex- pected to have approximately 6800 MW e of installed variable renewable capacity (dominated by wind) representing approxi- mately 50% of installed capacity. 1.1.2. Dispatch and curtailment In 2012, the total wind energy generated on the island of Ireland was 18.51 PJ. Dispatch-down of wind energy was 0.40 PJ, repre- senting 2.1% of total available wind energy [2]. The main factors which determine the level of curtailment are the amount of installed wind capacity and the instantaneous limit for system non- synchronous penetration (SNSP) allowed on the grid [3]. SNSP is defined as wind generation þ HVDC imports system demand þ HVDC exports : (1) all units in MW e . * Corresponding author. Environmental Research Institute, University College Cork, Ireland. E-mail address: jerry.murphy@ucc.ie (J.D. Murphy). Contents lists available at ScienceDirect Renewable Energy journal homepage: www.elsevier.com/locate/renene http://dx.doi.org/10.1016/j.renene.2015.01.048 0960-1481/© 2015 Elsevier Ltd. All rights reserved. Renewable Energy 78 (2015) 648e656