Dr. Paddy Finn:

I acknowledge the disparity in figures in demand response participation in the market. The source we used is published market data from a subsidiary of the Single Electricity Market Operator, SEMO. It is up to date to the end of February.

On the relationship between demand response and energy storage on the system, we all accept that a mosaic of solutions will get us to 2030. It is about finding the correct blend of solutions in terms of providing best economic value for the electricity customer and minimal impact on natural resources and on carbon emissions. There is little that demand response can do that storage cannot do but, with some of those characteristics, demand response presents a more economic and lower carbon form of delivery.

We spoke about high-speed systems services, which are sub-second responses to a frequency event in the power system that occurs when a power station or wind farm trips off the grid. The volume of that high-speed service is procured on the assumption that it will be the largest in-feed on the system, that is, the largest generator or connector that will trip at any point. That is typically 500 MW to 700 MW. In reality, 90% of power stations on the grid are less than 100 MW, so 90% of frequency events will be of 100 MW or less. The remaining 400 MW, which apply in only one tenth of events, play to the strength of demand response. Battery systems and other energy storage systems are good at providing constant frequency regulation and dealing with the little and often. If you use demand response all the time and impact participating customers all day every day, you end up with a shrinking pool of customers. If they are reserved for large events and used one tenth of the time, they can deal with four fifths of the magnitude of the events. That is the most economically balanced blend of storage systems and demand responses.