introduction
As the number of data centers increases, so does the demand for electricity. IT equipment consumes a lot of power, which can generate too much heat. Many data centers rely primarily on water to cool their infrastructure. Water is generally considered to be more abundant and cost-effective than electricity. In 2011, the Green Grid created the WUE(water usage effectiveness) metric to measure the sustainability of data centers in terms of water use and its relationship to energy consumption.
Why do we use wUE Metrics?
To understand the impact on the environment, data center operators take PUEs very seriously. Because the calculation of PUE does not involve water consumption, shifting the cooling burden from electricity to water can improve PUE. While this provides a way for data centers to reduce energy consumption, translating into lower environmental impact remains elusive. Many servers in hyperscale data centers require greater cooling capacity, which places a huge burden on local water resources. Given that data centers are often located in areas where water scarcity is likely in the future, WUE becomes a key metric. When combined with a PUE, WUE can provide a comprehensive overview of facility efficiency.
how to calculate WUE?
To calculate WUE, the formula is as follows:
For data centers with water-cooled air conditioning systems, water consumption mainly includes cooling water evaporation, cooling water drainage, humidification water for IT rooms, softening water for equipment, equipment maintenance water, and operation and maintenance water for the chiller system.
A lower WUE indicates a more efficient use of water in the data center. Water evaporation cooling scheme in refrigeration system can reduce the PUE value, but it also leads to the increase of water consumption, and there is a certain negative correlation between PUE and WUE.
low WUE does not solve all problems
It is estimated that the data center industry accounts for 1% of global electricity consumption (Jones 2018). On average, data centers use 1.8 liters of fresh water for every 1 KWH of IT power consumed (Shepherd et al., 2016,28). For comparison, it takes 57 liters of water to generate 1 KWH of electricity in the United States (Dieter et al. 2018,42). Traditionally, the SDGS have focused on energy rather than water, but this trend is changing.
Achieving the most sustainable data center cooling solution requires balancing the use of electricity and water. Cooling technology that does not use water at all (WUE 0) comes at the cost of electricity consumption and is therefore not the most sustainable solution. As technology evolves, the most sustainable solutions are those based on overall energy efficiency, water management and total cost of ownership. For example, if water is treated with an acid such as sulfuric acid, hydrochloric acid or ascorbic acid instead of additional water treatment equiment, the water can be reused multiple times, reducing the amount of additional water required.
"It's more important to consider the quality of the water being used. Is treated wastewater suitable for data centers to cool and flush our toilets or water our lawns? We have a one-time water infrastructure model that treats water to the highest quality and then uses that water for purposes that don't require potable water, such as cooling data centers." "Said Dr. Newsha K. Ajami, chief strategy and development officer for Research at the Berkeley Lab Earth and Environmental Sciences Area.
how can data centers plan for sustainable operations in a water-scarce future?
Big names like Microsoft and Google are now trying to pave the way for the data center industry to move toward renewable energy and more sustainable ways of working. Google is committed to using freshwater alternatives wherever possible, whether it's wastewater, industrial water, or seawater. So far, more than 25 percent of the company's data center campuses use recycled or non-potable water.
As for Microsoft, Noel Walsh, corporate vice president of cloud operations and innovation, blogged last year about how the company is currently looking for creative and innovative solutions for data center operations to help meet its sustainability goals. There has now been a commitment to reduce water use in data center operations by 95% by 2024, which means that all aspects of the business must be reviewed to reduce and eliminate water use. For example, a new approach to data center temperature management has now been introduced to help save about 5.7 billion liters of storage per year. In addition, research on liquid immersion cooling is being carried out to help achieve a water-free cooling future.
conclusion
Due to climate change and global population growth, fresh water will become scarcer in the future. Data centers built today will still be operating in 30 years. Data center operators must develop contingency plans to understand how to sustain operations without relying on water. Many data center companies have done an excellent job of improving sustainable practices within themselves and the industry as a whole. But they need to take a longer view of the challenges that the industry and the world will face in the coming years.