BBC discovers Heat Pumps
The BBC has discovered that modern technology can heat old houses and gives heat pumps a warm welcome.
Plas Newyyd, a National Trust property in Anglesey, will save £40,000 a year by switching to heat pumps instead of burning oil to keep itself warm. In this case the National Trust is using a marine source heat pump to transfer heat from the Menai Strait into the building.
For those, like Roger Harrabin, who express surprise that heat can be extracted from sea water, it is important to remember that the heat contained in any material is proportional to the temperature above absolute zero, rather than the freezing point of water.
A heat pump can concentrate heat by compressing refrigerant gases into a small volume and then transfer the heat into buildings to provide warmth via a heat exchanger. The refrigerant gas becomes cold when the pressure is released and this coldness can be exchanged with warmer water from the sea – and the cycle can be repeated continuously. The effect is that heat is transferred from the sea into the building.The BBC article makes some interesting points:
- Heat pumps are likely to become more common as the UK attempts to decarbonise its heating systems
- The use of heat pumps is growing as the government looks to subsidise low-carbon heat sources
- heat pumps will have a shorter payback for properties not connected to the gas grid
- air source heat pumps, which heat exchange with the air outside, are cheaper to install than ground source heat pumps, but they are at their least efficient on the coldest days. The sea is warmer than the air so a marine source heat pump is more efficient than an air source heat pump – because of the thermal inertia of the ocean from the previous summer.
The ground is also warmer than the air in winter, so a ground source heat pump is also more efficient than an air source heat pump – because of the thermal inertia of the ground from the previous summer.
It is possible to go one major step further in exploiting the thermal inertia of the immoveable thermal mass of the ground – by adding solar heat to the ground in summer in order to recycle the heat with a heat pump the following winter: Underground Thermal Energy Storage.
Heat pumps can play an important role in balancing supply and demand
The BBC article also observes that: "Heat pumps could also play an important role in balancing supply and demand in future energy systems. Electricity is difficult to store, but heat can be stored easily in the form of hot water."
In fact heat pumps will be able to play a far more significant part when it is understood that heat pumps can do much more than store a small amount of heat overnight in small hot water tanks: heat pumps play a significant part in interseasonal heat transfer systems when the ground itself can be used as a very large store of solar heat energy from summer to winter.