Thirsty power plants: the water footprint of generating electricity
To generate electricity, power plants use huge amounts of water. In Europe and the United States, generating electricity is accountable for 40% of the total water withdrawal. PhD candidate Industrial Ecology Yi Jin devoted his research to the water footprint of power plants and the impact on the environment. By researching the water footprint, he hopes to create more awareness and suggests alternatives. Yi Jin will receive his doctorate on 26 June.
Jin started his research into energy systems already during his master at the University of Petroleum in China. ‘Back there, it also included the water use for other energy sources such as oil and gas. After three years of research, we found that electricity is the most water intensive type of energy. So I focused my further research on electricity.’
Huge amounts of water
To generate non-renewable electricity, fossil fuels such as coal or gas or nuclear energy are burned. This releases heat, which is then converted into electricity. ‘In that process, large amounts of water are needed. In particular for the cooling of the power plant. As the majority of the world’s electricity is generated in this way, we are talking about enormous amounts of water. Studies in Europe and the US show that around 40% of all water withdrawal is for electricity production.’
40% of all water withdrawal in US and Europe for electricity production
Europe, United States and China
Most of research into the water use of electricity is done in Europe and US. In many other countries, researches have no idea how much water is used. ‘As China is the largest electricity-generating country in the world, we wanted to look into that. During our research we found that around 10% of China’s total withdrawal of water, is for electricity power production. Compared to the US and Europe, the proportion is not as high, but the problem is that there is a geographical mismatch between water resources and electricity power plants in China.’
The two biggest water resources in China are the Yellow River and the Yangzi River. ‘Most of China’s power plants are based around these two rivers. For the western regions, there is less water so they use a cooling system that doesn’t need a constant supply of water.’
Three ways to cool power plants
There are three ways to cool power plants. With a once through cooling systems (OTC), the cooling system takes water directly from the river. After using it, the water gets dumped back into the river. The opposite is a closed- loop cooling system where the water is stored in a water tower and used multiple times. A third option is cooling through the use of air.
‘Difficult to say which cooling system is better’
‘All these systems have their disadvantages and advantages,’ Jin says. ‘We look at two concepts to compare: water withdrawal and water consumption. That first one is the amount of water that the powerplants withdraws from the river or water source. The water consumption is the amount of water disappeared or evaporated through the utilization. The closed loop withdraws less water at first, but as a lot of water evaporates, it consumes a lot more in the end. Air cooling has the least impact on nature. But as air temperatures can differ a lot, it is way less efficient and stable.’
Finding a good solution
So which of these systems are better? That’s difficult to say, according to Jin. ‘And it also depends on the condition of the local water resources. The OTC system consumes less water, but has a larger impact on the local biodiversity. Even though there are rules in Europe and the US for the temperature of the discharged water, it still has an impact on the (fresh water) species and the ecosystem.’
So the best solution is to find renewable energy sources such as wind- and sunpower, Jin concludes. ‘Now at least 67% of all electricity is generated by power plants. That needs to change. Hopefully this research is a way towards more awareness.’ Another solution would be to use other energy types. ‘Now we use fresh water instead of reclaimed- or seawater for cooling. The government in China is encouraging costal powerplants research into. But right now, the cost for the purification of the water is too high and we don’t have much technology to do so.’
Teacher in a Chinese university
After receiving his PhD, Jin will go back to China to start teaching at a university. ‘I got some offers from the University of Beijing and from my hometown Jiangsu. The choice is not easy as I have to consider not only the offer of the university, but also the living conditions and the distance from my family.’
But one thing he does know for sure. ‘I want to continue my research in this field, especially focused on the loss of biodiversity in freshwater due to China’s electricity generation.’
Text: Inge van Dijck