Systems that depend highly on renewables need to balance this intermittency of energy source in several ways. These are:
- Demand side response (effectively compensating customers for reduced supply) which brings few technical issues in the UK.
- Importing from interconnectors which are well established in the UK.
- Smart grid technologies which bring the opportunity to achieve higher degrees of flexibility but may also introduce a risk to system balancing if not properly coordinated.
- Large scale energy storage which presents considerable uncertainty.
Frequently commentators suggest that the response to the problem of intermittency in renewable generation is energy storage. However, there is no storage system that can address grid scale shortages of power. For the avoidance of doubt; there is no battery, nor is there the prospect of such a battery, that could compensate for prolonged (few hours) simultaneous drop in intermittent renewable generation at one or two major offshore wind farms.
Large amounts of storage might be achieved by aggregating a very large number of small storage volumes (electric vehicle batteries and user owned batteries), but to do this, we need to implement a very sophisticated Smart Grid and development of a ‘market’ mechanism to compensate owners.
A system that depends on large energy storage to maintain a consistent power supply has a high degree of technical risk.The Net Zero scenario and reports put to the government do not fully understand the storage requirements of the system. Proven energy storage systems such as pumped storage hydro require suitable sites, which are not easy to find. Other large-scale physical systems (flywheels, dropping weights and compressed air caverns) could potentially be used as storage, but they haven’t been fully developed yet. When we produce hydrogen from electrolysis, this can act as an energy store, but its efficiency as power-to-power round trip is low.
As we said above, no currently available battery technology is capable of grid scale storage, and neither do we have the prospect of such a battery.
Balancing the interdependencies between power generation, heat, transport, and industry, in a wider integrated system needs a guiding mind and coordinating body, otherwise known as an Energy System Architect.