District heating is generally an environmentally friendly method of heating buildings. But need varies substantially during a 24-hour period, and to meet peak demand, many district heating producers are forced to fire up expensive, fossil-fuel back-up boilers.
But Johan Kensby, a Building Services Engineering researcher at Chalmers, has now demonstrated how to avoid this in a cost-effective way. In the first part of his doctoral project he observed that thermal energy can easily be stored in buildings, which creates good conditions for evening out the load on the district heating system (read more in Thermal energy storage in buildings makes district heating more climate-friendly
In the second part of his doctoral project he investigated how the use of district heating can be controlled in practice. Kensby conducted his research in collaboration with the company Göteborg Energi. Together their work included performing an extensive test with varying hourly prices to 19 residential properties. Each property had been equipped with a control system designed to heat the property as inexpensively as possible. As a result, the properties moved their use of thermal energy to the times with the lowest production costs and least environmental impact.
“This is a very cost-effective way of saving money and sparing the environment in district heating production. Indoor temperature sensors and connected control systems are becoming increasingly common in properties, so software is all that’s needed,” says Kensby.
In terms of environmental impact, Kensby has calculated that controlling 20 percent of the properties in the district heating network can reduce the use of fossil-fuel boilers for thermal energy by 25 percent.
“This is financially beneficial and benefits customers and the environment. We are now continuing to work on creating attractive offers for our customers based on Johan’s results,” says Ulf Hagman, Development Manager at Göteborg Energi.
The business model is as yet unwritten, but Johan Kensby thinks that the best method is for the energy company to provide the investment and heating control function and then share the financial gains with its customers in a suitable way. The challenge is to find a business model that distributes profits and risks fairly, while also being simple to communicate.
Kensby says that his collaboration with Göteborg Energi, where he has spent a lot time working on site, has been one of the most enjoyable aspects of his doctoral position.
“I’ve had the opportunity to work close to real conditions, and the results of my calculations have been used in practice on a large scale. There are also many inspiring people there.”
And Göteborg Energi appreciated his presence at their company.
“Johan is a very committed and skilled person, who has also contributed to our internal collaboration regarding these issues. Having a researcher here with us has given us close contact with Chalmers and access to Johan’s network, which we greatly appreciate,” says Hagman.
Johan Kensby will publicly defend his doctoral thesis on 12 May. He will subsequently work with systems development and digitalization in district heating through the Utilifeed company that he has helped to establish.
Text and photo: Ingela Roos