Reduced / Sequestered
(To Implement Solution)
In district heating and cooling (DHC) systems, a central plant channels hot and/or cool water via a network of underground pipes to many buildings. Heat exchangers and heat pumps separate buildings from the distribution network, so that heating and cooling are centralized while thermostats remain independent. Rather than having small boilers and chilling units whir away at each structure, DHC provides thermal energy collectively—and more efficiently.
Copenhagen, Denmark, is the global standout in DHC. It now meets 98 percent of heating demand with the world’s largest district system, fueled with waste heat from coal-fired power plants and waste-to-energy plants. (In the coming years, biomass will replace all coal use.) Since 2010, Copenhagen has also tapped the waters of the Øresund Strait for district cooling.
Compared to individual heating and cooling systems, Tokyo’s district system cuts energy use and carbon dioxide emissions in half—a powerful example of DHC’s potential. Although a tried and tested technology, it is still new and unfamiliar in many parts of the world, and high up-front costs and system complexity continue to be obstacles. Municipal governments play the most essential role in taking this solution to scale.
By replacing existing stand-alone water- and space-heating systems, district heating can reduce carbon dioxide emissions by 6.3–9.9 gigatons by 2050 and save US$1.6–2.4 trillion in energy costs (setup costs would be US$227–337 billion). Our analysis estimates that currently, less than 2 percent of delivered building heat is supplied with renewable district heating systems. While natural gas is currently the most prevalent fuel source for district heating facilities, we model the impact only of renewable sources such as geothermal and biomass energy that will become more prevalent over time, and an availability analysis shows that there is much room to grow.
Note: August 2021 corrections appear in boldface.