Research Record: Diversifying Heat Sources in China’s Urban District Heating Systems Will Reduce Risk of Carbon Lock-In

Authors: Denise L. Mauzerall (Princeton), Shangwei Liu (Princeton), Yang Guo (Princeton), Fabian Wagner (International Institute for Applied Systems Analysis), Hongxun Liu (Xi’an Jiaotong University), Ryna Yiyun Cui (University of Maryland, College Park)

Title: Diversifying heat sources in China’s urban district heating systems will reduce risk of carbon lock-in(external link)

Journal: Nature Energy

The Big Picture
Since its implementation in 2017, China’s clean-heating policy has considerably improved air quality across the country. However, the share of non-fossil energy sources in China’s urban district heating systems remains low. Denise L. Mauzerall, the William S. Tod Professor of Civil and Environmental Engineering and Public and International Affairs, was part of a study that examined how the diversification and decarbonization of heat sources for district heating systems will be crucial for China to reach its carbon neutrality goal by 2060.

In China, district heating systems are widely used to distribute heat across cities via insulated pipes from central locations — similar to Princeton University’s ground source heat pump(external link). These systems can integrate diverse heating sources; however, in China central heating systems rely primarily on excess heat from coal power plants to provide district heat and opportunities to decarbonize the systems have been largely untapped. In 2020, fossil fuels accounted for 90% of global district heating, particularly in the two largest markets of China and Russia. District heating currently represents 4% of global CO2 emissions, with a significant contribution arising from China and, to a lesser extent, Russia and Europe.

The Findings
Coal powered district heating makes it difficult to retire coal power plants as alternative sources of heat must be found to replace what those power plants no longer provide.  Mauzerall and her co-researchers compiled an infrastructure database of over 1,000 power and industrial plants in northern China and examined  hypothetical investment scenarios related to cost and emissions including: a high-coal scenario that relies heavily on the construction of new coal-fired combined heat and power (CHP) plants and a low-coal scenario that assumes the full implementation of clean heating policies and the extensive integration of industrial waste and ground-source heat.

Under the high-coal scenario, CHP power plants would cumulatively lock in almost 19,000 terra-watt hours of coal-fired electricity and produce about 30 gigatons — or 30 billion metric tons — of carbon dioxide emissions from 2020 to 2060.

Under the low-coal scenario, electric technologies, including waste heat recovery with electric heat pumps and air/ground-source heat pumps, can avoid the construction of new CHP plants and reduce carbon emissions by about one-quarter between 2020 and 2030.

The Implications
For China to succeed in peaking carbon emissions as planned by 2030, it will be critical to reduce emissions from district heating.  Meeting China’s 2060 carbon neutrality goal will require extraordinary efforts immediately to expand low-carbon heat sources so that CHP plants contribute only one-third of total district heating by 2030.  Continued use of these plants for district heating will require that coal power plants continue to operate, hence “locking-in” their carbon emissions into the future.

“Strategic low-carbon district heating technologies will be needed for China to peak carbon emissions by 2030 and reach carbon neutrality by 2060,” Mauzerall said. “Our findings indicate the importance of the government’s recent proposals to decarbonize district heating. These efforts should be immediately prioritized to avoid long-term carbon lock-in.”