Aldyen Donnelly: Denmark’s overlooked District Heating network

I recently entered into a dialogue with a Canadian business journalist about lessons Canada can learn from European energy and environmental market regulations.

My principal point is that while many Canadian academics and environmentalists misrepresent, often quite unintentionally, the impacts of post-1990 European energy tax and cap and trade measures, they appear to have missed the VERY important positive story of District Heating in Europe. I think this is largely because the lion’s share of European District Heating Infrastructure was fully developed by 1985 and has nothing to do with post-Rio/UNFCCC decision-making.  

One of the key resulting failures is that we are now planning to shut down and decommission coal-fired power plants that are rarely retired in Europe. In Europe, the same plants are worked through three phases rather than simply shut down. In phase one, they make only electricity. In phase two they co-generate steam (which, in Europe, is usually condensed into hot water to supply a District Heating network) as well as producing electricity. In phase three (after 45+ years of operation), they cut back their electricity production and continue to make steam to supply District Heating.

An aged coal-fired power generating unit might operate at an efficiency rate as low as 30%—meaning the energy value of its power output equates to 30% of the energy value of the fuel fed into the generating plant. Fossil and or biofuels are combusted to make steam, which is then pushed through turbines or other processes to make electricity.  

The average GHGs per MWh of electricity output is usually in the 1.1 to 1.3 TCO2e/MWh net output range. But the aged boilers often make steam/hot at 85% efficiency.  

On average, 10,000 pounds of steam converts to hot water that displaces about 1 MWh-equivalent of electricity or natural gas demand. When we take away the step of converting the steam into electricity, and directly use the steam or condensed steam to supply district heating, the GHGs per MWh of useful heating value delivered to customers can range anywhere between 0.4 and 0.8 GHGs per displaced MWh-equivalent of electricity or natural gas demand.  

Using aged boilers to supply heat into the district heating network can be a very cost-effective transition in a GHG reduction strategy. The key is the distance of the boilers from the homes, commercial offices and industry that can use the steam/hot water.

Denmark has been able to develop hot water recovery, transmission and recycling systems at a retail cost to Danish consumers in the CAD$0.06/ to CAD$0.10/displaced MWh retail price range. This is significantly less than the CAD$0.46/MWh average price for electricity that is currently charged Danish households.

The Danes have found that they can pay off capital and operating costs in a network that carries hot water as far as 55 kilometers from steam/heat sources to retail customers.  Steam is more efficient than hot water over short distances; hot water is more efficient than steam over longer distances.

Note that the Danish District Heating network was almost fully developed by 1985, when Danish retail (taxes included) power prices were still below CAD$0.12/MWh.

The reporter was on his way to Copenhagen and decided, as a result of our conversations, to set up meetings with Danish administrators and operators of the Danish District Heating network, which currently supplies hot water and displaces 60% of the nation’s previous electricity and natural gas demand to heat space and hot water.

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