Integrating renewable energy sources with the UK electricity grid through interconnection or energy storage systems

Abstract

This thesis considers the generation and demand challenges of a 100% renewable UK electricity grid and how this can be addressed with interconnection or energy storage. Hourly demand and electricity generation profiles for a year have been constructed: Business as Usual with a yearly demand of 540TWh and Green Plus (rapid uptake of energy efficiency and green measures) with a demand of 390TWh. In addition, two extra scenarios based on the above have been considered with electrification of heating (air source heat pumps) and transportation. The resultant hourly imbalances have been used to calculate the interconnection and energy storage requirements. The calculated interconnector capacity required was found to be 60GW at a cost of GBP 58 billion for the BAU scenario. Energy storage capacity requirements vary depending on the selected technology. Rated capacity was estimated to be 14GW with storage capacity of 3TWh for pumped storage, 11GW and 2.3TWh for liquid air, and 65GW and 13.6TWh for hydrogen storage, at a cost of GBP 65, GBP 76 and GBP 45 billion respectively. This thesis indicates that storing hydrogen in underground caverns would offer the cheapest solution. However, whilst these technological solutions can address generation and demand imbalance in a fully renewable electricity grid, there remain barriers to each technology.

A further technological solution is to exploit the use of electric heat pumps for domestic heating and hot water, as well as the moderate uptake of electric vehicles. It is proposed that these technologies are used on a local scale to help integrate the additional renewable electricity generated within a pre-determined zone of the electricity network. Analysis has been carried out to determine the constraints in the UK network where renewable electricity generation is greater than local electricity demand. From this, consideration has been made to understand the real impact distributed energy storage in the form of heat pumps and electric vehicles could have. Results show that depending on the demand scenario and location on the network, there is the potential to accommodate up to 50% of the excess electricity generated.

Lastly, analysis was conducted on a hybrid technological solution which combines interconnector and energy storage capacity in order to ensure that demand is met year round. This analysis indicates that an optimal combination of a 37GW interconnector plus 11GW of hydrogen (cavern) storage at a cost of GBP 42 billion for the BAU scenario is possible. Likewise, for the GP scenario a 24GW interconnector plus 8.5GW of hydrogen (cavern) storage at a cost of GBP 28 billion was found to be optimal. This analysis shows that a hybrid solution provides a lower cost option than installing either one of the solutions separately.

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ORCID for Patrick James: orcid.org/0000-0002-2694-7054

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