Intermittency and periodicity in net-zero renewable energy systems with storage

The reducing cost of solar and wind energy together with the UK commitments to net-zero emissions will mean that UK energy systems for 2050 and similarly those in many other countries will be dominated by variable renewable supplies. Electricity systems are expected to be very reliable but renewable energy is inherently intermittent. We explore energy storage as a solution to this problem, considering the physics of the system to gain understanding of its needs, rather than using its economics, which may lead to less adequate designs. The scale and the periodic nature of the energy storage problem are crucial to system design. There are very different physical needs for storing energy for: days, weeks and years. Therefore a range of storage technologies with their differing characteristic will be required for these different periods. A UK energy system with three types of storage is modelled to both dimension and schedule these stores in light of the physical features and the cost parameters of potential storage technologies. The scale of the UK's energy storage need is large - more than a thousand times that of current storage systems - potentially increasing the energy costs of a 2050 energy system based largely on solar and wind, by a significant amount. Though the UK is considered as an example, the methods could be used for any country that is planning an energy system with a majority of variable renewables and a net-zero carbon target.