Heat Pumps: one answer to global warming is right under our feet

An amusing story relates how Thales of Miletoes, the 6^th century BC Greek Philosopher said by some to be the father of science, fell into a well one night while observing the night sky. He had been so intent in observing the heavens that he failed to watch where he was walking. The attractive servant-girl, who answered his cries for help, mockingly asked him how he expected to know anything about the stars when he didn’t even know what was on earth under his own feet.

Thales’ mishap reminded me of a situation faced by the ACR industry today. We are so intent on ozone depleting and green house gases that we don’t notice positive environmental opportunities closer at hand. For well over a decade now, we have been made aware of the negative impact that the use of certain refrigerants have on the environment. Climate change is the greatest environmental challenge facing the world today and we are right to want to reduce our contribution to the causes. Global warming and rising fuel costs are also demanding a profound change in the way we generate and use energy and it is easy to see why the focus of our mind set has become one of ‘phase-outs’, ‘restrictions’ and ‘reduction’. We and others, view our activities as part of the problem.

However, an alterative view has never been far away. More than a hundred and fifty years ago, our own Lord Kelvin presented to the Glasgow Philosophical Society his idea for a double-piston machine that could both heat and cool air for domestic purposes, in other words a kind of heat pump, essentially the refrigeration cycle used today, and so needs no further introduction here. At the time, there wasn’t an energy shortage and it was not until considerably later that the heating and energy efficiency potential of his work was re-visited. Whereas a boiler releases heat, a heat pump transfers heat; it absorbs it at low temperature and releases it at a higher level.

Fortunately, we don’t have to have Kelvin’s knowledge of thermodynamics to appreciate the advantages of a heat pump although an understanding of energy is helpful. We all have an intuitive feel for what is meant by ‘energy’. However, of all the concepts of physics, it is easier to talk about its manifestations such as heat, and driving energy, e.g., electricity. We know that energy is something that we have to pay for if we want to get something done. If we want to drive to work, we have to pay for the petrol, if we switch on the light we have to pay for the electricity and if we heat the house we may have to pay for the gas, coal or oil that contains energy which is released as heat during combustion in a boiler.The huge advantage that a heat pump has when compared to an ordinary boiler, is that the out put is greater than 1. The amount of efficient usable energy at a higher temperature is great than the amount of driving energy necessary to keep the process going. In other words, a heat pump delivers more than 100% of the equivalent heat input supplied to drive it. In practise they actually typically deliver 400 times the equivalent heat input.

In environmental and energy terms, the potential attraction of heat pumps doesn’t end there. If a natural refrigerant, such as CO2 is used, and the electricity for the drive motors is from a renewable source, we have a product that makes an even greater reduction in carbon emissions. It makes use of an inexhaustible, freely available heat source to supply more than it consumes. It is tried and tested technology with a system at its heart that it familiar to all of us.

Unfortunately, it seems that more consultants, engineers and building owners are aware of the negative aspects of ACR systems than have a thorough knowledge of heat pumps and heat recovery. Sadly, a blinkered approach to heating and cooling is all too common and we need to work to change this focus of the debate. Using the Thales tumble as a metaphor; it may not exactly be that the ACR industry is likely to fall down a well as it is being led there and pushed. Yet, like Thales, perhaps one solution lies literally all around us and in the ground under our feet.