Four new green ways to heat homes

“The original meaning of the word Glasgow is ‘the green place’, so it’s apt that the city is hosting COP26.

“During the climate conference, the Scottish Government ran events to demonstrate how it plans to meet net zero. The events have largely focused on how we can reduce the amount of carbon emitted when we heat our homes. There were some seriously exciting innovations on display that may well pave the way for larger scale rollouts.

“And let’s hope they do, because the UK’s 30 million homes currently account for more than 21% of our total carbon emissions. Decarbonising domestic heating is a major part of reaching net zero for us all.

“Here are my top four favourite innovations from Scotland that show how we can create greener ways to heat our homes.”

We hear most often about air source or ground source heat pumps, but have you ever heard of a water source heat pump? In Glasgow, a renewable energy company is heating multiple buildings at once through a district heating network, and it’s all powered by the River Clyde.

The Clyde may not be the warmest river in the world, but that’s not a problem because heat pumps work well in sub-zero temperatures.

What is important though is having a stable and reliable heat source. Knowing this provides some certainty about how much electricity is needed to run the pump and extract the heat. The Clyde provides exactly that.

Based at Queen’s Quay on the south side of Glasgow, this area used to build cruise ships and now houses one of the UK’s first river source heat pumps, with pipes running under the Clyde.

Where there’s muck, there’s heat, as Scottish Water is now proving. They’ve been trialling heat pumps that use the sewer system as a heat source. They extract heat from wastewater and then transfer it into clean water, where the temperature is raised and then used to heat buildings. This provides a reliable and stable heat source, which can be fed into a heat pump or a heat network.

They have established four trial sites to test the pumps. One of the sites is in Dalmarnock, in the east of Glasgow. It’s connected to a heat network, where lower costs for heating could help reduce fuel poverty.

There’s an astonishing potential for generating heat from abandoned mine shafts in the UK, with nine out of 10 major cities built above mines. Many of these are old coal mines that were once contributing to climate change. In the future, they could be at the forefront of decarbonisation.

In Scotland, there are thousands of mines around the Central Belt, which sits in the middle of the country and includes cities like Edinburgh and Glasgow. These mines offer stable temperatures all year round, with the deepest shafts getting up to the high 20s degrees centigrade at the bottom. Old mineshafts are flooded, and heat exchangers are used to extract heat from the water.

Estimates reckon that heat from mines has the potential to provide up to a third of Scotland’s heating needs. At the moment, high upfront costs mean that geothermal power can struggle to compete with gas, but there are some projects already underway in Scotland and elsewhere in the UK.

A team from University of Strathclyde has a geological observatory in the Cuningar Loop of east Glasgow that is aiming to provide evidence that will further de-risk projects looking to bring costs down in the future.

One of the key challenges that the transition to low carbon heat poses is how we store heat. We need more heat when it’s cold in the winter, and less of it in the summer. As we electrify heat by installing more systems like heat pumps, we will have more electricity available at times of high renewable generation, and sometimes less – for example, on a calm, cloudy day. Smoothing out these peaks and troughs in supply and demand is important – reducing the need for more power stations and infrastructure – and making sure we have heat when we need it.

In people’s homes, thermal batteries can help store heat for hot water or heating systems. Scottish company Sunamp has developed a compact thermal battery, which is smaller than a hot water tank, and so potentially could be effective in constrained spaces.

Larger versions could provide flexibility to district heat networks – storing heat when electricity is cheap and using heat from the thermal battery when costs are high to keep the costs of the heat network lower.