Sign Up for Newsletters

  • Mae'r tîm @PrifysgolBangor a @PrifysgolAbertawe yn bwriadu cynnal rhagor o waith gyda'r sector morol Cymru mewn project newydd SEACAMS2.

The National Trust is exploring the possibility of heating Plas Newydd using a marine source heat pump.


Business: Plas Newydd, National Trust

SEACAMS contact: Mike Roberts


Project Background

Most people think renewable energy from the sea involves harnessing the tides or building offshore wind farms. A fresh concept, to explore the use of the sea as a direct heat source, has been proposed by the National Trust.

Anyone swimming in the sea in late summer will testify that the sea is warm. Sea water, like any water, has the ability to retain heat for a long period of time. It takes a lot of heat to warm it or indeed cool it.  This begs the question could this ability to retain heat allow us to extract it to heat large coastal properties?

Plas Newydd is a large 18th Century country house on the banks of the Menai Strait. Previously a holiday home for the 1st Marques of Anglesey, it is now a visitor attraction and museum cared for by the National Trust. An oil-fired heating system is currently used to warm this 2000 square metre property making it the largest single consumer of oil in the National Trust.

The National Trust

The National Trust is a charity, founded in 1895, with the aims of saving Britain’s heritage and open spaces. By 2015, the National Trust in Wales is aiming to generate 60 % of its energy needs from renewable energy sources. The charity has already installed a range of renewable energy technologies, such as biomass boilers, air and ground source heat pumps, PV panels and hydro-electric systems. Across Wales, the installation of PV panels at 7 properties has recently been completed, but further renewable energy technology installations are underway. To follow the National Trusts progress with renewable energy developments, you can read Keith Jones’ (the National Trusts Environmental Advisor for Wales) blog at

Heat pumps

Using the ground as a source of heat is an already established renewable energy technology in homes. Known as a ground source heat pump, this technology operates on the principle that the sun warms the ground to a constant 12oC. This heat can be captured by burying a series of pipes in the ground filled with a fluid that will absorb the heat. The fluid is passed through a compressor that raises it to a higher temperature. The heat can be extracted and used to heat water that, in turn, heats the house. The cooled fluid passes back through the pipes in the ground to repeat the process. The technique works as there is a net return of energy. For every one unit of energy needed to power the system, 4 units of energy are generated.

The length of pipe that needs to be buried for a ground source heat pump depends on the size of the property: a domestic home typically needs about 1000 metres. A property like Plas Newydd, which is much larger than the typical home, would require extensive excavations to bury the required length of piping. Using the sea, with its tidal currents and ability to retain heat, could help reduce the length of piping needed and therefore minimise the effect on the historic landscape of the property and the installation costs. Implementing a marine source heat pump will also reduce the National Trust’s carbon footprint and their operating costs.

Exploring the use of a marine source heat pump in the Menai Strait

The first steps in exploring the feasibility of using a marine source heat pump are now being taken. We need to understand the practicalities of extracting heat from the sea, and the short and long term effects that may have on the marine environment. We want to be sure that the impact of the heat pump, both in terms of installation and operation, will not have a detrimental impact on marine life. Conversely, we also need to be sure that marine life will not have any detrimental effect on the operating efficiency of the system.

Surveys by the SEACAMS team are now underway to examine the physical and biological environment the system would operate in. We have deployed an ADCP (Acoustic Doppler Current Profiler) to measure current speeds through the Menai Strait, conducted sea bed surveys to examine biological activity and multibeam surveys to map the sea floor. Numerical models will now be built to look at how the pump system could impact the marine environment.

The marine source heat pump.

Bathymetry of part of the Menai Strait.