Ground source heating at Croome
As part of the recent re-servicing project in the house we have installed a new ground source heating system.
The ground source heat pump at Croome helps to reduce our reliance on fossil fuels. This eliminates journeys made by fuel delivery tankers, the risk of spillage and the emissions made by burning fossil fuels.
For every unit of electricity used by the system, we are getting around 4.5 units of heat out and into the house.
While this electricity is partly generated using fossil fuels, the emissions from a large power station are greatly reduced per unit, compared to those of our old oil boilers.
So how does it work?
Ground source heat pumps work by absorbing energy from the soil and transferring it into a building to heat it without the need of using fossil fuels.
At Croome we have a large ‘ground-loop’, a network of pipes approximately 6kms long, under an area of the south park. These pipes are filled with a mixture of water and antifreeze which absorbs the heat from the ground as it is circulated around the system. The average ground temperature in the United Kingdom during summer and winter is around 10 to 11 degrees Celcius.
The fluid is passed through a compressor that raises it to a higher temperature, which can then heat water for the heating and hot water circuits. The system works a bit like a domestic refrigerator in reverse.
The cooled ground-loop fluid passes back into the ground where it absorbs further energy in a continuous process as long as heating is required. At Croome the heat pump is housed in its own building at the back of the Red Wing.
How is the system controlled?
Unlike a domestic house where the heat is controlled by temperature sensors, within the house the heat supply in each room is controlled by a humidity sensor.
The entire system can be controlled from a ‘state of the art’ online control panel which can be accessed from a computer with a browser.
In a historic building humidity levels are much more important than actual heat levels; we cannot allow the fabric of the building or its contents to become either too dry or too damp, we aim to keep the building between 45 and 65 percent relative humidity (RH).
When the humidity reaches the National Trust set point, 58 percent RH, it turns the heating on in order to control the humidity inside the house keeping the building at the optimum level.