Making money at low temperatures

“Our goal should be to invest in lowering the return temperature in the district heating network. There is a lot of money to be made from this, but there is no quick fix, it requires systematic work,” says Cilla Dahlberg Larsson at FVB, who has extensive experience with helping customers lower return temperature.

FVB has long worked with collecting temperature data and has temperature statistics for Swedish district heating systems all the way back to the 1970s. More than 200 systems are currently included in the statistics, which are updated every year. 

In the mid-1990s, Cilla Dahlberg Larsson and Sven Werner created an Excel model to calculate the economic system benefit of a reduced temperature level in Borås’ district heating system. The methodology has since been developed and has been used by FVB to calculate potential benefits in about 40 district heating systems. The ideal – with today’s technology – is to have a flow temperature of 68 degrees Celsius and a return temperature of 34 degrees Celsius as annual averages, but this assumes that the entire district heating system is flawless.

Major variation

Over time, the flow temperatures are largely unchanged, while the return temperatures are falling slowly. There is also major variation in flow and return temperatures between different district heating systems.

Cilla Dahlberg Larsson is a little frustrated that not more companies are investing in reducing return temperatures. 

“There are major economic and environmental gains to be made here, but despite this, it is something many energy companies deprioritize. I think it’s high time they rethink this and invest in this work,” says Cilla Dahlberg Larsson.

Systematic work

This is work that is often overlooked, despite the fact that it is very important. Energy companies can earn an average of 0.5–1 SEK per MWh and degree by lowering the temperature level in the network. This is from lower distribution losses and better conditions for, e.g., flue gas condensation. How much money can be saved largely depends on the type of fuel and heat production.

A few years ago, Cilla Dahlberg Larsson, together with her former colleague Stefan Petersson, investigated whether flow rates could lead to lower return temperatures. It could – in certain cases, but it was not a pattern that was repeated everywhere.

“This shows that there is no simple solution to lowering the return temperature, it requires commitment and systematic work to improve poor facilities. Monetary incentives are not enough.” 

To successfully lower the return temperature, Cilla Dahlberg Larsson recommends that energy companies: 

  • Work systematically to correct defects. 
  • Follow up on the worst facilities and focus primarily on improving those. 
  • Make sure to detect defects quickly, which is done in the measured value system. 

For more information:
Cilla Dahlberg Larsson, 031-10 60 86

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