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Heat Exchange Systems (Heat Pumps)
Heat exchange systems cover a range of different technologies that work on one idea, take heat from the earth, bodies of water, or straight from the air, raise its temperature, and use it to heat your home. There is then no need to have a boiler which relies on fossil fuels.
The most common question is how much a year this would save you compared to your current heating system. An actual estimate is hard to produce since it relies on so many factors; however a good way to judge a system is by the Coefficient of Performance or CoP. A heat pump has a CoP of about 4 or 5 meaning for every 1 kilowatt of energy you put into the heat pump, you get 4 or 5 kilowatts of free energy out. In contrast a standard boiler will only give you a CoP of about 0.9.
How it works:
A heat pump is a simple concept. Air is taken from an external source and compressed. The compression causes the temperature to rise; a popular analogy is the bicycle pump. Put your finger over the end of the pump, then push the handle to compress the air, you will find that the air inside is now warm. Once the temperature has been increased, the heat is siphoned off uses such as under-floor heating. Since the air has now had the heat extracted, it is sent around the loop again to repeat the process. Although the method of extracting heat can vary, the rest of the process is very much the same.
Ground Source Heat Pump:
A Ground Source Heat Pump (G.S.H.P) begins with pipe work buried in the soil. This sounds like a peculiar approach at first, but at 1 meter deep, the soil temperature in the U.K is about 12°C (54°F) all year round. This pipe work can be laid in a horizontal loop or vertically through the use of a borehole. Each method has its advantages.
A horizontal loop is cheap and easy to install although bear in mind that nothing can be built on top of this, and you have to be careful when planting trees as the roots may also interfere with the pipe work.The vertical option consists primarily of a borehole sunk to a suitable depth. The required length of pipe work can be split over several holes. The main advantage of this method is the space that is saved.
Air Source Heat Pump:
An Air Source Heat Pump (A.S.H.P) doesn't rely on pipe work in the ground to operate, it extracts its heat directly from the air. Because of this, when siting the unit itself, there needs to be clear space surrounding it to provide the required air flow.
The main doubt people have when it comes to the air source heat pump is its ability to work in our cool climate. Surprisingly the heat pump will operate in temperatures as low as -20°C (-4°F). Should the heat pump detect that it is starting to freeze; it will use some of the extracted heat on itself and automatically defrost itself. Understandably since the temperature outside can vary so much, the CoP is estimated to be slightly lower
Exhaust Air Heat Pump:
This heat exchange system isn't as widespread as the other mentioned types, but it it just as effective. Instead of extracting heat from an external source, the exhaust air heat pump (E.A.H.P) extracts heat from inside the dwelling. These kinds of units are more suited towards smaller houses and apartments.
Benefits
- Heat pumps are green technologies, they reduce your carbon footprint since the only power that's needed is for the pumps
- Long life spans: Since the only moving parts for a heat pump is the pump itself, not much can go wrong, the average lifespan of a system is about 25 years. These aren't predicted lifespans either; countries such as Iceland and Sweden have been using these technologies for decades.
- A heat pump will increase the resale value of your home
- Best of all, there are government grants available to help with the cost of buying and installing these green technologies.
Drawbacks
- The drawbacks of a heat pump rely mostly on the system you are intending to use. For the ground source, the installation prohibits anything to be placed over the pipework, meaning you're restricted to a lawn. For air source, the CoP tends to vary depending on the conditions.
- Ground source heat pumps are expensive. Although the price is falling all the time, an installation can cost in the tens of thousands of pounds.
- The overall efficiency rests with the person occupying the dwelling. Manufacturers are finding that if the customer hasn't fully understood how to operate the unit once installed, then the actual benefits of having a heat pump can be reduced.
Heat Exchange systems are a great alternative to the more common boilers and will only continue to become more common as the government tighten the rules on carbon dioxide emissions and in turn, the cost of these units will decrease. More information on heat pump technology can be found on the Energy Saving Trust website. They also provide detailed information on grants that are available.
