“Technological advances will reduce the need to build conventional new power stations” commented Nicola Shaw, the Executive director of the National Grid, recently.
This would seem to be a challenging statement in the light of the National Grid’s own Future Energy Scenarios showing an increase in the demand for electricity and a decrease in gas driven by the electrification of heating – driven by widespread use of heat pumps. How can increases in demand for electric heating match with a reduction in the need for new power stations?
Nicola Shaw comments that demand shifting can come about through the smart use of electrical appliances – e.g. for households to run washing machines at cheaper times of the day and for the ability to choose when to run appliances. This is all very well for appliances that people can choose when to run, but what about heating and hot water? 9000 people died last winter in England and Wales as a result of living in a cold home; An investigation by panorama suggested as many as one in ten pensioners cannot afford to heat their homes properly.
Heat pumps generally reduce electricity demand by a third for a given amount of heat produced. Obviously they have to run when people need heat, like a gas boiler, and so heat pumps on their own, would not have the capability to shift demand. To shift demand, heat pumps must be used in combination with energy storage. Further, that storage capacity must be ‘charged’ at times when heat is not needed, or the heat pump must be sized to be able to charge a store, while also delivering heat.
Minus7 has a hybrid system in which heat pumps are combined with thermal stores and a solar endothermic collector (the roof of the building). The collector harvests solar energy in the form of heat, which boosts the amount of energy available to the heat pump improving the heat pumps efficiency. On sunny days, the solar energy gained can heat the property directly with no need of the heat pump.
A typical dwelling uses a maximum of 60kWth per day in the winter, or approximately 2.5kWth per hour. To make a material difference to demand load shifting, then we need to be able to move demand by more than 2 hours i.e. we need around 7.5kWth of thermal storage, available ‘instantly’. The Minus7 thermal stores have a capacity of 9kWth per dwelling.
With the addition of PV and electricity storage (i.e. batteries) of around 5kWe per property, there is the potential to provide a complete heat and power service to a portfolio of residential properties with minimal requirement for grid electricity. We note that during the winter, there is not enough solar energy to power the properties and grid electricity will be required. For the remainder of the year, the properties could run with no impact on the grid. In fact, given the volume of the thermal and electrical storage in the properties, they could absorb surplus energy from the grid on sunny windy days.
Nicola Shaw is absolutely right that smart technologies will remove the need for additional power generation. In fact Minus7 could remove the majority of residential demand from the grid altogether – without the need for new power stations.
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