Water use in China’s thermoelectric power sector

New research from Oxford University’s Environmental Change Institute sheds light on China’s water-for-power nexus. Lead author, DPhil student Xiawei Liao, provides an overview of the challenges and trade-offs facing the Chinese energy sector.

Despite being historically managed in isolation, water and energy are two closely interlinked resources. For thermoelectric power plants, water is critical for power production, providing both steam and cooling. Water shortages have caused power curtailments at a number of thermoelectric power plants around the world (Byers et al., 2014), highlighting the critical nature of the water-for-energy nexus, and bringing it to the fore of science and policy debates.

In China, the relationship between water and electricity is a particularly pressing concern. The country is heavily reliant on thermoelectric power, with many plants drawing water from inland waterways vulnerable to water shortages. The vast majority these plants are coal-fired, with coal accounting for over 75% of China’s electricity production (National Statistics Bureau, 2014).

Cooling technology is the key determinant of a coal-fired power plant’s water intensity, defined as water use per unit of electricity produced (Macknick et al., 2012). Water use comprises both water withdrawal and consumption, with water consumption defined as water which is withdrawn from, but not returned to, water bodies (AQUASTAT, 1998).

There are three main types of cooling technology: open-loop, closed-loop and air cooling: the first dissipates heat using running water; the second by recirculating water; while third employs air circulation. Consumptive water use in an open-loop system is around 70–80% lower than a closed-loop cooling system, but the water withdrawal is around 30–60 times higher (WRI, 2015).

Our research, recently published in Global Environmental Change, first quantified the current water use of China’s coal-fired power plants, using plant-level data. We identified two major hot spots for surface water consumption: the Yellow River basin in eastern China, and the Yangtze River basin in southwestern China. Groundwater abstraction for power generation was outlawed in water-stressed Northern China in 2004, but continues to be heavily abstracted, particularly around the North China Plain (Huang-Huai-Hai basin). Reclaimed water is also used in water-scarce North Eastern China, but accounts for a smaller portion of water use overall. In 2014, Chinese coal-fired plants used 0.79 billion m3 of reclaimed water compared to 4.64 and 1.05 billion m3 for surface water and groundwater respectively.

consumption

Fig. 1 Water consumption of coal-fired power generation by source.

In order to avoid unsustainable future investments and technology lock-ins, our research also investigated future water use scenarios for China’s thermoelectric power sector.

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Fig.2 Annual fresh water withdrawal (left) and consumption (right) by China’s thermoelectric power sector under different scenarios (billion m3).

If no new policies are implemented, China’s demand for water-for-energy – both withdrawn and consumed – is projected to increase to over 280 and 16 billion m3 respectively by 2050; this greatly exceeds the current volumes of 65.2 and 4.64 billion m3 currently used.

Improving energy efficiency, or shifting energy infrastructure to renewable, or low-carbon sources offers scope to reduce water withdrawal by over 50%. Under high-renewable and low-carbon scenarios, concentrated solar power and inland nuclear power would replace coal-fired power as the primary fresh water users. Replacing open-loop with closed-loop cooling systems in the south, and closed-loop cooling systems in the north with air-cooled systems, has potential to cut the power sector’s water withdrawal significantly. However, it may increase water consumption, particularly in the east and central China. While water withdrawal poses less threat to water availability for downstream users, it may cause thermal pollution to the water bodies. Trade-offs between water withdrawal and consumption need to be made.

At a regional level, central and eastern China withdraw the great volume of water for power generation due to the prevalence of open-loop cooling systems. In 2011, China issued its ‘most stringent water policy’ – ‘3 Red Lines’ – setting targets for total water use on a national as well as a regional scale for 2015, 2020 and 2030. Qin et al. (2015) showed that the water use of China’s power sector is likely to exceed its allowances under the ‘3 Red Line’ policy in 2035 on a national scale. Furthermore, we find that the power sector’s water use in the east will exceed its regional quota under all scenarios, unless steps to change cooling technology are taken. The above-mentioned policy is also likely to be violated in central and north China if the business carries as usual.

rsz_comparison

Fig. 3 Comparison between regional water demands by power sector with water targets set by the ‘3 Red Lines’ policy in 2030. (W-Fresh water withdrawal in 2030; C-Fresh water consumption in 2030; B-Baseline Scenario; HE-High Efficiency Scenario; HR-High Renewable Scenario; LC-Low Carbon Scenario; TC-Technology Change Scenario; IWA-Industrial Water Allowed).

Finally, Chinese electricity generation, and associated water demand, both peak in winter when water availability is especially low. This increases the potential for conflict during this period. In the context of a changing climate, the tension between water demand for power generation is unlikely to decrease. Institutional change and improved policy coherence is required to meet this challenge. The old paradigm, where each sector operated independently, uninformed and unconcerned about its impacts on the others, is no longer sustainable. China must transition to a new paradigm – one embracing a ‘system-of-systems’ approach.

Xiawei Liao is a DPhil student at the Environmental Change Institute supervised by Prof Jim Hall and Prof Nick Ayre. You can find out more about this research in Liao, X., Hall, J.W., Eyre, N. Water use in China’s thermoelectric power sector, Global Environmental Change, Volume 41, November 2016, Pages 142-152.

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