CHOICES Energy Centre in Owen Square Park in Bristol is a valuable example of where a public park serves as a community energy generator. The heating scheme, funded by DECC, won a Regen Green Energy award. It captures and stores heat inside the park and delivers it to public and private customers around the park using a micro-grid.

Owen Square Park is located in Easton, an inner-city area of Bristol. The park adjoins to Easton Community Centre and a local Mosque to the west as well as terrace houses to the north. To the south-west it is bounded by the Bristol and Bath Railway Path. Owen Square Park offers several sports facilities, for example a playground and games court, which are well used by the local community. The site itself is owned by King George V Trust but managed by Bristol City Council.

Since 2016 the CHOICES Energy Centre has been located in the park hosting a hybrid air/ground heat pump. An array of 12 boreholes, each at 150m depth, is situated under the Owen Square Park as well as a 'private wire' power network to distribute locally generated solar PV electricity to the CHOICES Energy Centre to offset the electricity consumption of the heat pumps.

The Energy Centre is a pilot site to demonstrate the potential for creating small-scale, modular combined heat and power schemes which can be run by local community-based organisations, in this case Owen Square Community Energy co-op. The energy scheme uses surplus locally generated solar PV electricity in summer to power an air source heat pump for charging an interseasonal borehole-based thermal energy store. This creates higher borehole temperatures which increase the efficiency of heating in winter. The capacity of the district heat network is rated at 140kW and provides heating for two buildings, the Easton Community Centre and its annex.

The use of this hybrid and active recharging technology provides multiple system efficiencies. Firstly, the solar PV output is optimised. Secondly, heat pump efficiencies are optimised by charging the borehole field with heat in summer. And finally, the air source heat pumps run on green electricity which may otherwise cause power quality issues on the local feeder or even reverse flows onto the Medium Voltage network. The system is also tuned to optimise the use pattern of the heating system against the time of use tariffs across the day by avoiding expensive evening peak periods.

One of the key lessons learned from the project was the need to carefully research all the stakeholders involved and ensure that there is a well-planned programme of community engagement. Parks are often considered to be cherished public spaces and it was critical to bring all local community groups on-side well in advance, given the disruption to the park while the works were undertaken. Therefore, the engagement period needs to be factored into the project plan with sufficient time allocated to its delivery. It can help to provide commitments to improving the quality of the park and its facilities as part of the project. The CHOICES team for example created a replacement set of steps in the park and the Energy Centre, as a long-term legacy. Site specific graffiti art was also commissioned by local artist Zoe Power, referring to special character of Owen Square Park.

The CHOICES Energy Centre began full operations in December 2016. A key part of the implementation of the project was the installation of comprehensive performance metering and monitoring to support subsequent assessment of the efficiency and heat cost of the system. Subsequent performance assessment has shown the summer efficiency of charging the ground source array is nearly 6 to 1, meaning 1kWh of PV electricity can supply 6kWh of heat to warm the ground. With the value of surplus PV electricity being about 6p/kWh this puts the cost of “summer recharge“ at about 1p per kWh. In winter the system is typically delivering heat to buildings with an ambient outdoor temperature of 7C and using a 55C flow temperature and in these conditions the system efficiency is 3.7 to 1. For the financial year 2019-2020 the final cost of heat for customers from the system is 5.69p/kWh.

Project team
Cepro: Project lead, integration of solar PV, monitoring
ICAX: Energy centre design and construction, and interseasonal storage
Eunomia: Business case analysis
Bath University: investigation of potential for algorithm control of predictive storage

Read the Owen Square Case Study

Supported as one of the Rethinking Parks prototyping projects, ParkPower is a data-driven approach, working at a Scotland-wide scale, to identify the parks with most potential to support green energy infrastructure. It will be showcasing the range of energy opportunities in parks and exploring the potential to generate income and savings from and for our greenspaces.

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