As China converts to clean energy, households

image: Princeton researchers evaluated several clean heating options in China and found that air-to-air heat pumps provide the most benefits in terms of climate, air quality, health and economy .
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Credit: Egan Jimenez, Princeton University

Many Chinese households still depend on small charcoal stoves for heating, causing air pollution that is harmful to health. To address these issues, the Chinese government in 2017 launched a five-year “Clean Heating Plan” with the goal of shifting 70% of northern coal households to cleaner heating options.

As the plan reaches its final year, a new study by researchers at Princeton University offers policy directions: increase the use of heat pumps in rural households. Of the options studied, researchers found that air-to-air heat pumps provide the most benefits for air quality, health, and climate.

Heat pumps run on electricity and are more energy efficient than electric resistance heaters, coal stoves or gas heaters. They are cheaper to operate in the long run, but come with higher upfront costs, which could be a barrier to their adoption.

Additional grants and incentives could help, the researchers said, especially in poor and extremely cold rural areas. Labeling heaters with their annual energy demand and operating costs – similar to the US “Energy Star” program – can also encourage homeowners to install these high efficiency appliances.

The study, published in Sustainability of nature, is the first of its kind to provide an integrated analysis of alternative heating options and their costs in northern China.

“China has a goal of carbon neutrality by 2060 and is committed to a successful effort to reduce air pollution. We have found that replacing coal stoves in urban and rural homes with clean heaters dramatically improves air quality in northern China during winter while reducing premature deaths, ”said Denise Mauzerall, Professor in civil and environmental engineering and international affairs. “While all clean heaters reduce emissions of air pollutants, some increase carbon emissions. We have found that heat pumps offer the most significant reductions in air pollutant and carbon emissions, and that these reductions will increase as the power grid moves further away from coal and non-fossil electricity. .

Mauzerall led the study with co-lead authors Mi Zhou, postdoctoral research associate; and Hongxun Liu, associate researcher (currently associate professor at Xi’an Jiaotong University); as well as Liqun Peng, a doctorate. candidate for the Science, Technology and Environmental Policy program – all of which are part of her group based at the Center for Energy and Environmental Policy Research at the Princeton School of Public and International Affairs. Other authors include Yue Qin and Lin Zhang, both of Peking University, and Dan Chen of the Meteorological Administration of China.

Given that China plans to be carbon neutral by 2060, “decarbonizing” its power grid – or the system that supplies electricity – is essential. One way to do this is to move away from coal and shift to more non-fossil fuel.

The research team evaluated alternative heating options under three low-carbon electricity grid scenarios: the 2015 data, in which coal supplied 68% of China’s electricity grid, and two projections from 2030 – one in which the coal only fed 35% of the grid and a projection in which the grid is carbon-free.

They then looked at four clean heating options in these scenarios: electric air-to-air heat pumps, natural gas heaters, electric resistance heaters, and clean coal stoves (using improved coal stoves). with treated charcoal). They determined what would happen if households in northern China switched from coal stoves to one of these alternatives, taking into account initial and operational expenses.

Researchers have found that all clean heating options produce air quality and health benefits, but carbon emissions vary widely depending on the heating and fuel choice. They found a substantial increase in carbon dioxide emissions when electric resistance heaters are fed with electricity generated mainly from coal, as was the case in China in 2015, to a substantial decrease when heat pumps aerothermal heaters are used with a carbon-free network.

Electric resistance heaters can incur carbon penalties, and their operating costs are highly dependent on the price of electricity and subsidies. Therefore, the researchers recommended them only as a backup heater for heat pumps when the temperatures are extremely low, making the heat pumps inefficient.

Clean coal with improved stoves is inexpensive to purchase and operate, but their emissions are variable and likely to be quite high if dirty coal is used. Their temporary use, by households that currently do not have access to electric or gas heating, would reduce emissions compared to the use of traditional charcoal stoves. That said, a uniform national standard for clean coal is needed to ensure emission reductions, the researchers said.

While gas heaters have the greatest short-term benefits, building the necessary gas infrastructure is expensive and can block longer-term use of fossil fuels. Electric heat pumps will move the residential sector away from fossil fuels as the electricity grid shifts over time from coal-fired power to renewable and nuclear power.

Of all the scenarios analyzed, the use of heat pumps with a carbon-free electricity grid offered the greatest benefits for air quality, health and carbon reductions.

The study has certain limitations. Researchers were limited to 2015 data for the baseline emission scenario. Since the plan was announced in 2017, China has taken steps to reduce emissions, so the environmental and health benefits reported in the study are likely lower now. Additionally, the analysis does not examine indoor air pollution or any variation between households such as house size, building energy efficiency, and indoor temperature preference, some of which will be included in future. work of the Mauzerall group.

“A major contribution of this work is the inclusion of a comprehensive cost analysis of alternative heaters for all northern provinces,” said Mauzerall. “Although the initial costs of heat pumps are generously subsidized in wealthy provinces like Beijing, policies that reduce the investment costs of heat pumps in poorer provinces are needed, especially for rural areas in the poorest provinces. extremely cold regions. “

The document, “Environmental Benefits and Domestic Costs of Clean Heating Options in Northern China,” was published on December 23 in Sustainability of nature. It has been financially supported by Princeton University, the Ma Huateng Foundation Grant to the Princeton School of Public and International Affairs, the National Natural Science Foundation of China, and the China Scholarship Council.

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