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Tech made easy: let’s talk about heat pumps

Ground source, air source, water source – get the lowdown on this energy efficient way of heating


What we’re talking about: Ground source, air source and water source heat pumps

Why?  They can save you money, especially if you don’t have a gas supply

Did you know? The technology is over 160 years old

Gosh! I thought heat pumps were a recent invention… Yes, it is a bit surprising. They’ve become a popular renewable heat technology in the last decade or so but they were invented way back in the mid 1800s.

That’s amazing. How do they work? Quite simple really. Residual heat from the air, ground or water is absorbed at low temperature into a fluid. The fluid is then passed through a compressor which raises the temperature to between 20-30°C. This high temperature is then transferred to the heating and hot water circuits of a building.

So you get heat for free? You’re not using gas, oil, wood or some other fuel… Well yes and no. Heat pumps need electricity to operate, but so long as there’s more energy coming out than going in they make sense. And you could potentially generate the electricity you need using solar or hydro – if you want to pump up your green credentials even more.

We call the ratio of energy in vs energy out the ‘Coefficient of Performance’ or COP. For example, a COP of 3 would mean for every kW of heat energy going in, you get 3 out. So if you’re looking to buy a heat pump, the higher the COP number, the more efficient it will be.

Sounds great. Are heat pumps suitable for all types of business? They’re ideal if you’re looking at retrofitting your whole heating system. Or if you’re in an area with no natural gas supply and are currently using oil, electricity or an LPG boiler for your heating. They’re not so necessary if you already have a modern heating system and efficient gas boiler. It’s important that your property is fully insulated so that all the lovely heat that builds up doesn’t fly out the building.

How is the heat distributed throughout the buildings? We have radiators at the moment throughout our building. They work best with warm air or under floor heating systems because these require lower water temperatures. But they can be used with wet systems such as radiators.   The radiators should be on the large side because heat pumps tend to work at lower temperatures. So the more surface area the radiator has, the more heat you’ll get from it. It takes a while for the heat to build so heat pumps are good if you tend to heat your property for a long time instead of short bursts.

Sounds like heat pumps might struggle to give hot water.  Indeed! They’re not ideal for hot water because of the high temperature requirement. A solar thermal system would be a better bet.

A solar thermal what? Sorry, that’s a conversation for another day.

Air, ground, water… Can I choose which one to use? Tell me more about them. The clue is in the name, of course. And they each have their pros and cons. Air source heat pumps are relatively easy to install and you don’t need a big outdoor space, just somewhere that gets a little airflow. They also tend to be a little less expensive than the other options.

But? But they’re not as efficient as water or ground source heat pumps. In Scotland, air source pumps work well in the spring and autumn but not so well in winter when the air temperature drops.

I am wondering how much space is needed for a ground source or water source heat pump.  Ground source heat pumps are more effective year round but you need an outdoor space about as big as a tennis court to bury the coils in 1-1.5m trenches. Alternatively, you can drill a single borehole about 100 metres down, if the ground allows. Water source heat pumps are easier to install than ground and are the most efficient of the three technologies. You just lay them in a body of water, such as a lake or stream, and run insulated pipes to your property. The obvious drawback is that you need access to water.

It doesn’t sound like they’d be cheap. How much would I be looking at to buy a heat pump system? This is totally dependent on the size of system that you need and your heat requirements. Starting prices for small systems are around £8000 for an air source heat pump or around £10,000 for a ground or water source heat pump. If you’re replacing oil, electricity or LPG you’ll make annual savings on your energy bills ranging from hundreds to thousands of pounds. In addition, there’s the government’s Renewable Heat Incentive (RHI) scheme, which gives a tariff of 4.7p per kWh to businesses that install systems under 100kW. The Scottish Government SME Loan is unsecured, with 5% interest for renewable technology. Our advisors will help you with the full loan process.

Sounds reasonable. Something to bear in mind is that the bigger the system, the more electricity it will need to operate it. So if you decide to go for a large system, you may need to upgrade your electricity system.

And how long do heat pumps last? Do they require a lot of maintenance? Maintenance is pretty minimal. An engineer service every three years should be enough. Maybe a yearly check for leaves in the filters and any encroaching roots. Typically, they should last 15-20 years. That compares well with traditional boilers, which only have a ten-year life span.

I’m assuming I wouldn’t be the first business to install a heat pump? No, quite a few have made the plunge. You can read case studies from small to medium sized businesses on the Green Network for Business. They include a caravan park, a village hall, a hostel and a city office.

Is there anything else I should know? If you’re thinking about installing a heat pump, we can help. Call us on 0808 808 2268 or email enquiries@resourceefficientscotland.com. We can help you go through all the options, calculate what size and type of system would be best and if there’d be any associated costs like insulation needs or new radiators. And we’ll do all this for free.

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