The challenge: renewables alone don’t guarantee resilience

With the pressing need to transition to a low carbon economy, planning and preparing for energy resilience[i] is becoming increasingly important in an energy system consisting of a significant proportion of decentralised renewable energy sources and a decarbonised power system.

On their own, renewable energy systems provide little resilience since the power output from renewable sources is intermittent and cannot be easily controlled. Energy storage systems have been identified as a physical means to achieving resilience.

The idea: utilising smart batteries to benefit communities

The quick response of domestic storage technologies such as home batteries (having discharge time in milliseconds) means that they can rapidly respond to disruptions in electricity supply such as brownouts (intentional or unintentional drops in supply voltage) and blackouts (total power outage).

When integrated with decentralised renewable energy sources, domestic storage can potentially increase self-consumption of the generated power which means demand from the grid during peak periods can also be reduced.

Against this context, Project ERIC (Energy Resources for Integrated Communities) was funded by Innovate UK (2015-2017) to demonstrate how smart battery technology could help a community in Oxford get more direct benefit from solar PV and reduce their impact on the local electricity network, ultimately making it possible to install more renewable power generation locally.

82 homes in Oxford: how the research was conducted

Researchers from the Low Carbon Building Research Group of Oxford Brookes University empirically evaluated the outcomes of the project which deployed smart batteries (internet enabled and controllable) and solar PVs across a cluster of 82 dwellings in a community in East Oxford.

The evaluation approach comprised dwelling and household surveys, along with high frequency monitoring of household electricity consumption, solar PV generation, battery charge and discharge data.

Key finding 1: smart batteries increased self-consumption 6% on average

Solar PV systems were found to have performed well generating on average 5.5-6kWh/day in the summer, equating to 51% self-consumption before storage. However peak generation did not match peak consumption, demonstrating the need for battery technology.

The smart batteries were found to increase self-consumption of PV electricity and offset grid demand through discharge of stored PV electricity at an average of 6%, depending on the size of the PV system, surplus PV electricity available and size of the battery.

Key finding 2: community aggregation reduced peak demand as much as 8%

Electricity usage was found to vary widely making a strong case for community scale energy management. Aggregating solar generation and storage at a community level showed that peak grid electricity demand between 17:00 and 19:00 was reduced by 8% through the use of smart batteries across 74 dwellings.

Key finding 3: Don’t forget data connectivity

Interestingly, data communications was found to be a challenge. This issue of connectivity should not be underestimated, particularly with vulnerable and elderly tenants who are typically less likely to have an internet connection.

A promising “store and trade” future – and it won’t need a solar panel on every home

In the future, aggregating and controlling domestic storage in clusters could provide additional benefit in the form of increased self-consumption and dispatchable stored energy for grid services.

A local energy sharing and trading scheme could be developed, wherein not all dwellings would need to have solar PV systems, but rather have internet enabled batteries that could be monitored and controlled virtually. This could help improve the business case and economics of both solar PV and home batteries.

Further details about the study are described in the recently published paper.

[i] Resilience is defined as the capacity to recover quickly from difficulties.