Renewables and the grid: understanding intermittency

This paper reviews the key issues and fndings of the UK Energy Research Centre report on the costs and impacts of intermittent or variable renewable electricity-generating technologies. The relevant principles of managing electricity networks are examined and aspects that change when significant intermittent generation is added are analysed. The impacts and costs of intermittent generators can be quantificed only in the context of the characteristics of the system of which they form part. The principal reasons why these impacts differ from one system to another are examined and explained. The evidence for likely impacts and costs in the UK, at intermittent penetration levels up to 20% of total electricity supplied, is analysed. The two main categories of impact are on system balancing and system reliability, and costs are quantifed for these factors. Estimates are in the range of anadditional 23/MWh for system balancing and 35/MWh for system reliability.