District heating is getting cooler

For nearly 150 years, Londoners have felt a warm breeze coming from the ventilation shafts of the Underground. The engines and braking action of Tube trains produce this excess heat, which escapes into the atmosphere.

From the winter of 2017, however, a new project headed by Ramboll will capture the waste heat from a Northern Line shaft at City Road in Islington and use heat pumps to ‘upgrade’ the heat from 18-28 degrees Celsius to approximately 80 degrees.

Expanding the network to include this pioneering, low-carbon heat source will enable another 500 homes to be connected to the central London district heating system, raising the number from the current 850 to 1,350.

The Islington project is just one of many signs that district heating is making its global breakthrough as a technology that is both carbon-cutting and cost-effective.

“The possible market for district heating is huge,” says Sven Werner, Professor of Energy Technology at Halmstad University in Sweden and one of the world’s leading experts on district heating and cooling.

According to the ‘Heat Roadmap Europe’, a study conducted by researchers at Halmstad University, Aalborg University and the consultancy firm Ecofys, the EU countries can save at least EUR 100 billion annually – and cut carbon dramatically – by making district heating and cooling a key factor in the EU’s Energy and Climate Framework 2030. Recognising the inherent economic and environmental advantages, the EU’s new Energy Efficiency Directive requires all EU member states to conduct a comprehensive assessment of the national potential of district heating and cooling by December 2015.

“Many European cities have already adopted plans for using district heating systems to combat climate change. But only 12% of the buildings in Europe are supplied with district heating,” says Sven Werner.

District heating traces back to the hot water-heated baths and greenhouses of ancient Rome, but the modern version came to Europe from the USA at the end of the 19th century, when Frederiksberg, a part of Copenhagen, needed somewhere to dump the waste from its 75,000 inhabitants. To solve the problem, in 1902 Frederiksberg built Europe’s first district heating plant, which produced not only heat but also electricity based on waste.

However, district heating remained a minor heat source until the oil price quadrupled in 1973-74. Denmark was among the many Western countries whose energy production depended almost exclusively on imported oil, so people shivered in their homes, factories were forced to shutdown temporarily and driving was banned on Sundays.

After the crisis Denmark therefore vowed to wean itself off oil imports, determined to improve its energy security.

Fast-forward to 2015 and district heating networks are now supplying heat to a massive 64% of Danish households. And the plants also produce electricity, making them much more efficient than standard power stations.

Other Northern European countries have the same heat production potential as Denmark: A report commissioned by the Greater London Authorities has found that enough heat is wasted in London to meet 70% of the city’s heating needs. Capturing this heat and delivering it to the heat network would dramatically improve fuel bills, fuel poverty, fuel security and carbon emissions.

Crispin Matson, Country Manager of Ramboll Energy UK, agrees. He points out that using heat pumps in the Islington project for secondary heat source utilisation is more carbon efficient than gas-fired combined heat and power (CHP), the usual heat source in the UK’s district energy schemes.

“We believe that the use of large-scale heat connected in this way to urban district heating systems will play a major part in decarbonising the UK’s heating energy,” says Crispin Matson. Energy Services Manager Lucy Padfield from Islington Borough Council praises the project’s innovative nature. “It combines the use of large-scale heat pumps from low-grade heat sources with a district heating scheme that serves both new and existing homes and council facilities,” Lucy Padfield points out.

Germany is another country with a big district heating potential. And Danish companies are also beginning to win their first major contracts in the U.S.

The U.S. relies primarily on steam heating, which can be costly to operate and maintain, as well as being a potential safety hazard. Looking for an alternative, Bridgeport, located 100 km northeast of New York City, is now implementing a low-temperature heating and cooling system that uses waste heat from various CHP plants. The project, for which Ramboll is the lead designer, will not only provide cost-effective heat to Bridgeport but also reduce 70% of the city’s greenhouse gas emissions, amounting to 13,000 tonnes a year.

Another U.S. first-mover on district heating is the Ivy League university Dartmouth. Ramboll has conducted a renewable energy study for the school, highlighting the benefits of switching the existing steam system to modern hot water.

Professor Sven Werner sees the North American potential for district heating as even bigger than the European.

“But how to exploit the great potential in Europe and the USA is also a political issue,” he says.

Written by Michael Rothenborg.