District heating over 50 years, present and future

“FVB started in 1970, which means that the consulting business has been running for half a century. I myself started working with district heating in 1976, so my professional life with district heating has been almost as long. Such a long period of time gives rise to reflections about the past, present, and future,” says Sven Werner, Professor Emeritus in energy technology at Halmstad University.

1. My first reflection is that district heating technology has been largely intact for five decades. We have used central heat recovery, two pipes, and joint delivery to each building. The technical solution was developed when fuel oil dominated the heat supply in both district heating and building boilers. Oil was cheap until 1973 and you could easily create high temperatures in both radiators and district heating pipes. Both home installations and district heating technology have been characterized by this.

2. A second reflection is how quickly oil replacement was implemented. Many naysayers said it would take 20-25 years, but it only took eight years between 1982 and 1990 to reduce the share of oil in district heating’s heat supply from 72 percent to 7 percent. Oil replacement in the 1980s consisted of coal, industrial residual heat, and electricity for large electric boilers and heat pumps. Sweden created an electricity surplus when more nuclear power plants were built than was needed for the electricity supply. Biomass was introduced in the 1980s, but it was during the 1990s that it became established and was the dominant source of heat supplied from the district heating networks.

3. The third reflection is that district heating’s carbon emissions from fossil fuels have decreased by over 90 percent since 1970, which has prevented the negative effects from fossil fuel carbon. Admittedly, burning biomass causes carbon emissions, but they are part of the natural carbon cycle that has given the earth its current climate with a comfortable average temperature of 15 °C. This natural cycle is 15 times faster than the harmful fossil fuel carbon cycle that is now seriously jeopardizing the Earth’s future climate. The Swedish heating industry has now promised entirely fossil fuel-free district heating by 2030. Although this promise had been made for 2020 by the Swedish Parliament as early as 2009, that promise was forgotten on the way towards the goal.

The current situation for district heating is that it dominates the Swedish heating market for buildings with a market share of just over 50 percent, which is five times higher than in 1970. Oil-fired building boilers are almost extinct, whereas they accounted three fourths of the heat supply in 1970. Oil is no longer a competitor for district heating. The main competitor today is heat pumps, which account for one fourth of all heat to buildings. This is a healthy competition that helps to avoid less suitable heat pumps and district heating connections. On the other hand, the competition is impeded by the fact that district heating’s required rate of return is higher than the banks’ lending rates for heat pumps. District heating is part of the circular economy in that roughly 75 % of the heat supply is dominated by heat recovery from CHP plants, waste incineration, flue gas condensation, industrial residual heat, and large heat pumps.

4. A very important fourth reflection is that the role of district heating is anonymous in Sweden – its usefulness is not well known among users, customers, politicians, and other decision-makers. Few people know that district heating heats their homes. We are far behind Danish district heating, which admittedly has the highest prices in Europe but also has a much better reputation. The Swedish energy debate is characterized by issues other than district heating.

5. My fifth reflection is that there has been no major technological change in heat supply since 1970. Today, almost 90 percent of district heating originates in some form of combustion. Thus, no fundamental change in technology has occurred in heat supply and heat distribution over the last 50 years. This in itself is cause for concern about the future of Swedish district heating. History has many examples of industries disappearing from the market when they thought their technology would last forever. They were outcompeted by new technology that completely wiped out the old technology.

The future is always hard to predict. Forecasts will always be characterized by speculation, guesswork, and skewed expectations. The starting point for my exploration of the future is that right now a revision of the European reduction of fossil fuel carbon emissions for 2030 is being debated. The current goal is a reduction of 40 percent from 1990, but now a goal in the range of 55 to 65 percent is being debated. This means a higher level of ambition compared to the goal of 20 percent for 2020, which was met. This higher ambition will certainly result in a very turbulent heating market in Europe in the coming years. The big question then becomes how Swedish district heating will be affected by a dynamic European market.

6. The sixth reflection involves speculations about how district heating technology will change in Europe. Fossil fuel-fired CHP plants dominate the heat supply in Europe’s district heating systems. In many cities, contracts for heat deliveries from fossil fuel CHP plants have been terminated. Within just a few years, district heating systems must obtain a new heat supply, which usually consists of geothermal, solar heat, industrial residual heat, waste incineration, heat pumps, electricity from excess wind and to some extent biomass. But the proportion of biomass can never be as high as in Sweden, since the European land area does not have the proportion of forest biomass that exists in Sweden. This should lead to a lower proportion of incineration than in Sweden. A non-incineration heat supply becomes more efficient if lower temperatures are used in the district heating networks. Therefore, interest in fourth-generation district heating is higher in Europe than in Sweden. In our research, we have identified five different technological solutions within new heat distribution. The conclusion is that we will probably see technological shifts in both the supply and distribution within European district heating. The expansion in Europe will thus use other technology compared to what is currently being used in Swedish district heating.

7. My last and seventh reflection is about how Swedish biomass will be used in the future. There are many possible outcomes here, so I will limit my consideration to two extreme cases. In the first, about ten percent of the world’s fossil fuel consumption is used for non-incineration purposes, such as plastic production. The green carbon atoms in Swedish biomass could then become so sought after that they can no longer be used for their current purpose. When the incineration-generated heat supply decreases, other heat supplies must increase. The Swedish situation will become more similar to the European one, in which a new technology is needed.

The second extreme case is one where concentrated use of biomass in larger Swedish CHP plants may become suitable for capturing carbon dioxide from the natural carbon cycle. However, a new cash flow is required from a joint procurement function for carbon dioxide capture within Sweden or Europe. Heat from these CHP plants can then become competitive.

These seven thoughts reflect my experience of Swedish district heating. Of course, other experiences may give rise to other reflections. Finally, I wish FVB good luck for the next 50 years.

Mina sju reflektioner speglar min erfarenhet av svensk fjärrvärme. Andra erfarenheter kan naturligtvis ge upphov till andra reflektioner. Slutligen vill jag önska FVB lycka till under de kommande 50 åren.

Ytterligare information:
Sven Werner, 035-16 71 30


Sven Werner was employed at FVB during the years 1995–2007.

He is Professor Emeritus in energy technology and is affiliated with Halmstad University.

The photo shows Sven Werner in his extensive research library.

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