United Nations Environment Programme

District energy: a tried-and-tested answer to modern urban energy problems

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The concentration of buildings in cities means solutions can integrate multiple sectors, such as heating homes with underground heat or using cold water from rivers to cool whole neighborhoods

In homes and workplaces, schools and hospitals, technologies such as boilers and air-conditioners consume vast amounts of energy. Indeed, half the energy buildings use is for heating and cooling and most of this comes from fossil fuels, burned in buildings’ individual boilers and in power plants on the outskirts of our cities. Citizens, cities and countries are starting to take real action to move away from this status quo to more sustainable solutions, and this monumental shift is cutting greenhouse gas emissions, cleaning our air, saving money and reducing energy imports.

Consuming 70 per cent of global energy and as managers of local infrastructure, cities provide the ideal opportunity to develop innovative and sustainable solutions to heating and cooling. The concentration of buildings in cities means solutions can integrate multiple sectors, such as heating homes with underground heat or using cold water from rivers to cool whole neighbourhoods, as seen in cities ranging from Copenhagen and London to Tokyo and Seoul. The citizens of these cities are the first to benefit: less fossil fuels means cleaner air, steady heating prices and an easier fight against fuel poverty. Sustainable cooling cuts electricity demand from air conditioning during the hottest times of the day, increasing energy security for millions by reducing rolling blackouts and costly electricity infrastructure upgrades.

Many cities are prioritizing modern district energy as the integrated solution needed for sustainable heating and cooling. District energy systems consist of a network of underground insulated pipes that pump hot or cold water to multiple buildings in a district, neighborhood or city. Some systems just connect a few buildings, while others connect thousands of buildings and homes across a city. The result is the same: by providing heating and cooling to multiple buildings, district energy systems are able to use far larger sources of heating and cooling than can be connected to just one building. Such sources include: waste heat from industry or power stations; solar thermal; heat from groundwater and sewage; and free cooling from lakes, rivers or seas.

For cities, these larger sources of heating and cooling are greener and cheaper and make them more energy independent. In addition, district energy systems take advantage of surplus wind or solar power or surplus heat in the summer – at the lowest cost compared to other energy storage options. This energy can be integrated to balance variable renewable power through conversion to heat and stored for use seasonally (using soil or water) or during peak demand. Neighbourhoods, cities and countries are increasingly making district energy the cornerstone of their strategies to achieve 100 percent renewable energy targets.

Paris is one example of what can be achieved. The City of Light has developed Europe’s first and largest district cooling network, using the river Seine that divides the city in two for cooling. The Paris district heating company uses geothermal, excess heat from sewage and industry, as well as waste-to-energy in order to serve the equivalent of 500,000 households, including all hospitals, as well as 50 per cent of all social housing and public buildings, such as the Louvre Museum. There are plans to use 60 per cent renewable or recovered energy in the network by 2020.

The city turned to district energy as a core strategy to mitigate pollution from coal in the 1920s. Today it is putting Paris on the pathway to a 75 per cent reduction in CO2 emissions by 2050. In addition to providing cheaper and more renewable heating and cooling, district energy provides €10 million in fees and dividends to the city and has estimated annual benefits of €19.5 million.
Similarly Gothenburg in Sweden utilized district energy to reduce air pollution from burning oil for heating in the 1970s. Today the city’s district heating system uses 80 per cent renewables and waste heat, eliminating sulphur dioxide emissions, cutting nitrogen oxides by more than 90 per cent and halving emissions of carbon dioxide.

These are just two of the 45 examples from UN Environment’s flagship report District Energy in Cities – Unlocking the Potential of Energy Efficiency and Renewable Energy, which sets out the best practice technology applications, policy and business models needed for cities to implement sustainable heating and cooling.

“Through 150 interviews across 45 low-carbon cities, district energy systems emerged as a best practice approach in scaling up renewable energy and energy efficiency,” notes the report author, Lily Riahi. “Cities worldwide, in countries as diverse as China, Canada, the US, South Korea, Singapore, Colombia, Russia, the EU, Saudi Arabia, the UAE and Japan are using modern district energy to reduce energy consumption for heating and cooling of urban buildings by 30 – 50 per cent and to achieve ambitious targets for renewable energy, CO2 and clean air.”

“Switching to modern district energy requires innovative local planning that integrates energy and land-use, and coordination across multiple city sectors such as energy, transport, housing, waste collection and wastewater treatment. Because it’s new to many cities it takes time and many local governments worldwide do not have the capacity, accounting tools, or a clear mandate from their national governments to intervene in the sector,” Riahi said.

In response to these barriers, UN Environment’s District Energy in Cities Initiative is supporting local and national governments worldwide to strengthen policy and planning frameworks that will enable accelerated investment in modern district energy systems.

“Cities are turning to this Initiative to help them scale district energy and achieve multiple benefits such as waste reduction, local jobs, climate mitigation and power grid resilience. The benefits of district energy are aligned with many of the Sustainable Development Goals, such as improved health and wellbeing, which district energy delivers through real action on air quality,” according to Djaheezah Subratty, head of the Policy Unit of the Energy, Climate and Technology branch at UN Environment.

For example, in Bosnia and Herzegovina, air pollution is an invisible killer, resulting in 44,000 years of life lost every year and costing 21.5 per cent of national GDP. One of the main culprits for this air pollution is local heating using heavy fuel oil. The Initiative is working with the city of Banja Luka to expand and modernize its district heating network. This will cut fossil fuel consumption by 27 per cent, improving local air quality and saving 20,000 tons of carbon dioxide and €4.5 million in fuel expenditure each year.

China, Chile and Serbia have prioritized modern district energy at the national and city level as a solution to local air pollution, while the refrigeration emission reductions from district energy also make it a priority in Colombia.

The Initiative has built a partnership of almost 40 organizations including technology providers, utilities, financial institutions, academia, international organizations, city networks, NGOs and champion cities to raise awareness and transfer policy best practice worldwide.

“Although in commercial use for decades, district energy has remained relatively unknown to many decision makers. Countering misconceptions, while communicating the benefits and limitations of district energy will help them feel more comfortable exploring this technology approach,” says Subratty.

Indeed, district energy has been quietly building momentum and credibility over time. Today the US, EU and recently the G20 have signalled how essential it is to delivering clean air and decarbonization targets. District energy is also included as a key planning and infrastructure solution in the draft New Urban Agenda for Habitat III. Now the transfer and exchange of best practice, and the visionary leadership of local governments will be required to realize the full benefits and potential of district energy and create the sustainable cities of tomorrow.