Utilising excess power: the case of electrofuels for transport

Book chapter, 2014

If the production of electricity at a given moment in time is higher than demand we may talk about excess electricity.1 It is possible to store excess electricity and storage solutions might be essential for achieving very high renewable energy shares in the energy system. The most common purpose for storing electricity is of course to convert the stored energy back to electricity when needed. Currently there are not many mature alternatives for seasonal energy storage. Pumped hydro, hydrogen and compressed air are facing challenges with geographical distribution and ecological footprint, technical limitations or low density.2 Another option is to convert electricity into an energy carrier that can be used for other purposes, and not just as a medium for electricity storage. One possibility is to use periods of excess electricity for the production of carbon-based synthetic fuels, so called electrofuels,3 that can be used for various purposes, e.g. for heating, as a transportation fuel or in the chemical industry for the production of plastics, textiles, medicine and fertilizers. One challenge, common to all energy storage technologies, is to be economically viable in spite of the fact that excess, or low priced, electricity will likely be available only a fraction of the time. This chapter aims to explore the challenges and opportunities of using electrofuels to utilise excess electricity. Production processes are described and costs are estimated to underpin a discussion on what is required to make electrofuels competitive with gasoline.