How Do Heat Pumps Work?

What is cold? 

Zero degrees centigrade 0oC is normally considered as cold as it is the point water turns to ice. How can you take heat from something, literally, freezing cold? The human body is usually 37oC and a pleasant day is 30oC. So, it seems right, zero is cold. 

According to the boffins, in this galaxy, temperatures range from plus 6,000oC on the sun’s surface down to parts of space close to minus 273oC. This is known as absolute zero and is measured as zero degrees Kelvin(0oK).

For our purposes, anything warmer than -273o has some heat stored within it and our job is to get it out and use it as a green form of energy. The point to be grasped is, there is a lot of stored heat in objects, we consider to be cold. 

This heat extraction is carried out by heat pumps which take heat from air, from water in rivers or ponds or under the ground’s surface by boreholes or trenches. This heat is delivered to wherever you want it. We consider heat pumps to be green because they harness a renewable form of energy and getting this working requires a lot less energy than is extracted. 

Many people explain heat pumps by comparing them to refrigerators – in reverse. This analogy is more useful to people who already understand how refrigerators work and may well not need the explanation. However, everyone has witnessed warmish objects becoming colder after being placed inside a refrigerator. They become colder because the heat in the object is sucked out and dispelled. To avoid overheating, the refrigerator is ventilated and the heat dispersed. If it had started as a colder object placed in a unit and heat taken and recycled to wherever it is needed, then this by definition is a heat pump. 

To install a heat pump as part of your heating system does not mean you must understand all the intricacies of how it works in the same way you do not need to be a mechanic to drive a car. The basic ins and outs of various engines gives you an overview and if you decide to go for electric battery power over petrol or diesel engines, you understand why you made the choice. 

The same thinking applies to heat pumps. They are all described by what they do. How do they take their power and where do they send it to? They may take heat from air and distribute it by water through radiators or extract heat from air and distribute it through grilles. These systems are described as air to air or air to water. Alternatively, they may take heat from a ground source and distribute it through air or water. This is termed water to air or water to water. 

What is co-efficient of performance (CoP)? 

The CoP is the measure of return of efficiency of the overall system. You will be looking for the lowest spend or the highest amount of energy for the least amount of initial electricity. Which system configuration gives you the greatest return?

You will probably instinctively sense how you want it distributed or what you feel comfortable with (air or water) and you will want the most efficient access to the source. You should seek professional advice from a consultant or design and install contractor but understanding the basics does help. 

A point to consider is how we power the heat pump. To extract heat, we need electrical power and is this power generated by green methods? The green credentials of this electricity is determined by the origin of the generating fuel. Often, we use non-green power to extract green power. Unless you are self-sufficient and off-grid there is not much you can do as an individual on this front.

When you determine what the options are between initial outgoing costs, ongoing costs and your level of return your decisions are made easier. 

I am not sure we got anywhere near answering the question of the naming of number 11, or why it is windy at the local park but we can’t have everything. 

Why not give Fitzpatrick Team a call to help with your commercial build?