The prison service, overseen by the Ministry of Justice, is supporting a wider programme to decarbonise the prison estate and reduce CO2 emissions across ageing public sector infrastructure.
At HMP Eastwood Park in South Gloucestershire, Aermec systems are being deployed as part of the latest stage in this transformation, aligned with UK government net zero targets.
The project focuses on two prison blocks originally built in the 1960s, which together accommodate up to 400 women aged 18 and over. The upgrade works are designed to reduce energy consumption, lower carbon emissions, and improve overall building efficiency and thermal performance in a complex, continuously operating environment.
A £3 million investment is funding the replacement of outdated gas boilers with Aermec heat pump technology, supported by a wider package of building fabric and systems upgrades. Prisons present particularly challenging energy profiles due to constant occupancy, high heating demand, and strict operational requirements.
Alongside the heat pump installation, the works include enhanced roof and cavity wall insulation to reduce heat loss, replacement of existing windows with new double-glazed units, upgrades to the pumping and distribution systems, and a modernised building management system (BMS) to improve control and operational efficiency.
At the core of the solution are four reversible air source heat pumps (ASHPs) manufactured by Aermec, using R32 refrigerant with a global warming potential (GWP) of 675. Acoustic attenuation measures have also been incorporated to reduce operational noise levels within the secure site.
Although the ASHPs are capable of both heating and cooling, they are configured for heating-only operation. They form part of a cascade system, delivering water at a maximum of 45°C into an intermediate loop. This loop feeds Aermec water-water heat pump (WWB) units, which extract additional heat and further increase the water temperature.
The WWB units then provide high-temperature water up to 80°C for space heating and domestic hot water services including showers, cleaning and other ancillary uses. The system is designed to maintain delivery temperatures in the region of 78-80°C to support legacy heating requirements and high-demand loads.
Deployment is split across the site, with four WWB units serving one larger block with higher demand, and three units serving a smaller building with reduced heating requirements.
The Aermec WWB 900 units are designed specifically for irreversible (heating-only) applications and are optimised for high efficiency under both full and partial load conditions. Key design features include high-performance compressors, plate heat exchangers engineered for low pressure drop, and dual independent refrigeration circuits to ensure operational resilience and continuity during maintenance or component downtime.
