Pines Calyx is a purpose built low-carbon conference and events venue set in beautiful grounds in a stunning coastal location. It was originally constructed to Passivhaus standards of insulation and airtightness using rammed chalk sourced from the site as the main building material. It has been a long term objective of the Bay Trust, which owns and operates the building and grounds, to make the building truly carbon neutral by displacing its gas consumption and supplying its electricity on site.


We installed a 12 kW twin compressor heat pump to provide space heating and hot water. This sources its heat either from an open loop collector or from the solar thermal heat generated by a Photovoltaic Thermal (PVT) array.  Noting that the grounds are irrigated with ground water sourced from a borehole, we installed a valve which diverts the flow from the irrigation system through a heat exchanger in the building. The heat pump extracts approximately 5°C of heat from this flow before returning it back to the irrigation system.


We also mounted a 20 panel PVT array onto a purpose-built, faceted frame which follows the contours of the building. This has a rated output of 3.8 kWp and uses a SolarEdge SE3500 inverter with Power Optimiser boxes for each panel. The electricity generated by the array offsets mains electricity usage in the building, whist the heat it generates supplies the heat pump, supplementing the borehole.


The heat pump is integrated into the existing heating system, which is linked via a heat main to a gas boiler in another building on the same site. This connection has been retained to provide backup for the heat pump. It also allows for the possibility that the heat pump may be used serve other buildings on the same site in the future.