The efficiency, benefits of heat pumps
It is often said that if we give up fossil fuels, we will take society back to the stone age. With our family’s pursuit of decarbonisation, nothing could be further from the truth.
The technologies we’ve adopted to replace fossil fuels, from photovoltaic cells, to lithium batteries, are among the greatest advancements of modern science. Yet, when it comes to applying the laws of physics, none of these compares to the principle of the heat pump.
Heat pumps are familiar in our daily life — who doesn’t have a refrigerator? And yet they are an application of science that comes close to actual magic. They work on the principle of phase change.
Ice melting is an example of a phase change — solid to liquid, liquid to gas, and back again. The phase change happens because of the addition of heat, or the absence of heat. For instance, when the sun shines, water evaporates. When the water vapour rises to a cool layer of the atmosphere, it condenses, and falls as rain.
Each phase has a corresponding pressure range. The molecules of ice are pressed so hard together that you can skate on it. Water is liquid enough we can swim through it. And water vapour is so lacking in density it floats as clouds.
The magic happens because pressure and temperature are locked together by physics. If you add heat to water, it will evaporate to a less dense state. But you can also evaporate water by creating a vacuum, and it will be forced to absorb heat. This heat transfer leaves cold surfaces behind, which is how a refrigerator becomes cold even on a hot day.
Heat pumps use refrigerants to accomplish this cycle of evaporation and condensation, and essentially transfer heat from one space to another. In the case of your fridge, it transfers heat into your kitchen, which is why the back of the appliance is hot. For an air conditioning unit, it transfers heat out of your house, and into the open air.
Heat pumps can also transfer heat from outside, into your house. There are many types, from ground source heat pumps, often called “geothermal”, to air source heat pumps.
They can run in either direction, to cool your house, or heat it, depending on the season. The only energy input is electricity.
Heating a poorly-insulated home with electric baseboards can be very expensive.Electric baseboards work on the principle that electricity passing through a poor conductor encounters resistance, and this resistance generates heat. Electric cooktops, and electric hot water tanks, work on the same principle.
In contrast, a heat pump using the same electricity to drive an evaporator /condenser, can generate 2 – 3 times as much heat. This is why they are often described as 200300% efficient.
Because of this efficiency, heat pumps can provide as much heat as natural gas, for the same cost. And all without creating carbon emissions.
The efficiency of heat pumps is so good, Fortis will give you money to put them in your house. A range of rebates are available for home heating heat pumps, as well as heat pump water heaters.
We’re hoping to take advantage of them this summer, and get rid of the last two fossil fuel burning appliances in our house.
Much like ice cream on a hot summer day, pulling heat out of cold winter air seems to defy physics. In fact, it is physics in action.
Chris Allen is an architect and father of three teenagers. He lives in Penticton in a small house with a big yard. Email: info@landformadb.com
Website: www.landformadb.com