District Heating, the Secret to Denmark’s Success

Here in the US, when we think about reducing the use of fossil fuels, we think in terms of fancy renewable power technologies.  This was not where Denmark started its dramatic energy transformation back in the 1980s.

Here is the technology that is the backbone of Denmark’s energy system –


This is the Ballen Brundby district heating plant on Samsø Island.  And this is its fuel –


The Ballen Brundby plant heats the homes of about 300 families, businesses and institutions, entirely from straw and other agricultural biomass waste.  There are four district heating plants on Samsø and they provide about 60% of the heating on Samsø, all from renewable biomass fuel.  You can read more about Samsø’s remarkable renewable power journey in their report, Samsø – a Renewable Energy Island, 10 years of Development and Evaluation.

District heating was Denmark’s first response to the oil price shocks of the 1970s.  At that time, Denmark used oil as its primary heating fuel, as well as its main fuel for generating electricity.  Denmark used a lot of oil for heating, because Danish winters are long and cold.  The Danish government really didn’t have any fuel alternatives at that time, so the highest priority was to reduce consumption.  Here’s how the Danish Energy Agency describes it in the agency’s history of the shift to a wiser energy system:

Denmark chose early on to prioritise energy savings and a diversified energy supply, including use of renewable energy. A broad array of notable energy-policy initiatives were launched, including a focus on combined heat and electricity production, municipal heat planning and on establishing a more or less nation-wide natural gas grid. Furthermore, Denmark extensively improved the efficiency of the building mass, and launched support for renewable energy, research and development of new environmentally friendly energy technologies as well as ambitious use of green taxes.

The recycling of “waste” heat from industrial processes, district heating and rapid improvement in building insulation were Denmark’s first steps because they all involved proven technologies that would generate big savings in a relatively short time.  According to the Energy Agency’s report, district heating now provides more than 50% of the residential and commercial heat in Denmark.  While 17% of this heat still comes from natural gas, most is supplied by recycled industrial heat and biomass, as on Samsø.

Here is what Copenhagen’s system looks like:

screenshot-freshaireva us 2014-10-04 13-07-13In Denmark, district heating works in small rural towns and the biggest cities in the country.

While some urban district heating plants can be quite large, most are relatively small, because biomass fuel is expensive to transport and the plumbing required to send hot water for heat into homes and businesses usually has about a ten mile radius from a plant.  Both biomass and recycled heat provide significant income to local farmers and businesses, because they sell their heat to the district heating utilities.  Over time, district heating systems turn into networks as more and more producers of recycled heat feed heat into the system.

District heating involved a major infrastructure investment in new hot water pipes and pumps.  The first step in making this leap was to create a nationwide planning process to assess needs and to help local investors and governments plan their investments.  This planning “software” is a significant contributor to Denmark’s success, and contrasts sharply with the failure of energy policy and planning in the US.  I will deal with this subject in a later post.

So what does all this have to do with the electrical system?

In Copenhagen, I spoke with someone from DanskEnergi, the association of Danish power companies.  He pointed out two major contributions that district heating makes to Denmark’s electric operations: no peak loads and more flexibility for the remaining fossil fuel generating plants.

There is almost no electric heating in Denmark.  Although winters are colder there than in most of the US, there is no winter peak load phenomenon as there is in the US.  Last winter’s crisis in PJM is unthinkable in Denmark, because demand varies relatively little from winter to summer on the electric grid.

Denmark is pretty cool in the summer, so no residential customers have air conditioning.  The minimal air conditioning that is needed to cool large computer data centers is now being shifted to district cooling systems in major cities.  The cooling comes mainly from seawater, because most of Denmark’s major cities are located on water.  So Denmark has no summer peak either.

I asked the DanskEnergi official how Denmark’s remaining fossil fuel generating plants were managed when the country’s massive wind power system was running at full capacity.  In many countries, including Denmark, intermittent wind and solar power flood grid systems forcing coal and nuclear plants off the grid, or force them to accept negative prices, just so they can keep operating.  In Denmark, fossil generating plants (there are no nuke plants in Denmark) make money selling their recycled heat which cushions the economic impacts of high renewable penetration in the country’s energy markets.  Competition from wind power is still an issue for Denmark’s fossil fuel plants, but it is not the catastrophe that it is in countries without district heating.

In the US, grid managers such as PJM Interconnection, have to plan for large amounts of extra capacity just to cover peak loads that may only happen a few days a year.  This peaking capacity costs rate payers a lot of money.  In Denmark, there is no need for peaking capacity.

I wanted to cover district heating in this first Denmark post, because it is hard to understand the basics of Denmark’s energy system without understanding how important this development has been to reducing the country’s energy needs.  District heating doesn’t rely on fancy technology.  As you can see from the Ballen Brundby plant, there isn’t much to it: a furnace, some farm “waste,” a metal building and some plumbing.  And, of course, because all the ash is non-toxic, it is reapplied to farmers’ fields as fertilizer.  All of the potassium, phosphorus and other minerals in the straw ends up in the ash and can be completely recycled.

2 thoughts on “District Heating, the Secret to Denmark’s Success

  1. I appreciate the insights Bill but we have to remember the old “economies of scale” mantra and realize that what goes on the island is much smaller in scale and easier to deploy with all the resources available on a smaller populace. That said its great to see how Denmark prioritized the heating first as the cold weather there would suggest a greater need to benefit from saving on energy costs and providing warmth. I can’t wait to hear your next piece on one of the best places on earth to live.

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