Recently, Wei He, an associate professor at King's College London, and his collaborators have developed a new type of highly flexible electrodialysis technology, which improves the application efficiency of solar desalination technology and alleviates the impact of solar intermittent power generation characteristics on technical performance and economy.
图 | 贺唯（来源：贺唯）
As a new type of "energy storage" desalination technology, the electrodialysis technology developed this time can efficiently convert intermittent solar energy into purified drinking water like energy storage technology.
In this way, the energy supply can be decoupled from the energy consumption of drinking water production, and the water demand of residents in specific areas can be met.
It can also provide a sustainable drinking water solution for remote rural areas that lack a stable grid supply.
At the same time, compared to traditional desalination technologies that rely on grid power or expensive battery energy storage systems, this research aims to convert solar energy directly into drinking water through "energy storage" desalination technology, thereby eliminating the dependence on battery energy storage.
Since the cost of water storage is much lower than the cost of battery storage, this technology can improve the economics of solar desalination technology while improving energy efficiency.
日前，相关论文以《低成本太阳能海水淡化用的灵活批量电渗析》（Flexible batch electrodialysis for low-cost solar-powered brackish water desalination）为题发在 Nature Water[1]。
Wei He is the first author and co-correspondent, and Professor Amos G. Winter V of the Massachusetts Institute of Technology serves as co-correspondent.
图 | 相关论文（来源：Nature Water）
Specifically, this electrodialysis technology is expected to be used in the following scenarios:
First, it is used for drinking water supply in remote areas.
As mentioned earlier, this technology is particularly suitable for remote areas where the grid is unstable or not yet covered due to its ability to convert solar energy directly into desalinated water.
By then, residents in these areas will have direct access to safe drinking water from underground saline sources, improving the supply of drinking water.
Second, it is used for agricultural irrigation.
In water-stressed agricultural areas, the technology can be used to provide fresh water for irrigation.
Especially in areas with a lot of saline-alkali soils, the use of electrodialysis technology to desalinate water can effectively reduce soil salinity, thereby improving the yield and quality of crops.
Third, it is used for industrial salt-rich wastewater recycling.
Many industrial processes, such as food processing, produce large quantities of salt-rich wastewater. In the recycling and treatment of salt-rich wastewater, electrodialysis technology can significantly improve its efficiency.
Fourth, it is used for lithium extraction from salt lakes.
Electrodialysis can efficiently extract lithium ions from salt lakes and integrate the lithium extraction process with new energy sources such as solar energy, thereby converting solar energy (including curtailment) into high-value lithium materials, and then extracting lithium ions in a low-emission, high-quality manner.
（来源：Nature Water）
Some 1.7 billion people live in water-stressed areas
According to reports, this study is based on the severe background of global water scarcity, especially focusing on the challenge of drinking water shortage in rural areas of developing countries.
Today, more than 2 billion people around the world depend on groundwater as a source of drinking water, but about 1.7 billion people live in water-stressed areas.
Due to salinization caused by natural and human factors, the quality of groundwater is gradually deteriorating, resulting in many water sources becoming salty or salty, and unsuitable for direct drinking.
Despite the use of conventional seawater/brackish water desalination techniques, fresh water can be extracted efficiently. However, its widespread reliance on grid power and infrastructure limits its use in remote areas.
Especially in remote areas of many developing countries, such as India, the grid is either not covered or the grid is cut off. In addition, most of the electricity comes from coal-fired power plants, resulting in high carbon emissions.
However, these areas often have abundant sunshine, so distributed solar desalination technology can be a sustainable and universal solution to the problem of water scarcity in remote areas.
According to reports, this research originated from a project of He Wei's collaborator, Amos G. Winter V of the Massachusetts Institute of Technology in the United States.
Previously, the latter had worked with India's Tata on a series of research projects on water scarcity for drinking water and agricultural irrigation.
Later, MIT professor Tonio Buonassisi joined the project.
As a result, the technical route for desalination of underground salt water and drip irrigation for agriculture using solar energy has been established, which is expected to expand the use of water resources and reduce water consumption.
At the same time, the economic advantages of using photovoltaic-electrodialysis technology for solar desalination are also clarified. It was at this time that He Wei joined the above project.
In order to further reduce the cost of photovoltaic-electrodialysis technology, they established the design theory of photovoltaic-electrodialysis technology by using first principles, and optimized the design of photovoltaic-electrodialysis technology system based on this theory.
（来源：Nature Water）
In 2017, the first prototype system was built and tested in a village called Chelluru, India.
In doing so, they not only validated the theory of photovoltaic-electrodialysis technology models and system design, but also gained insight into the specifications and cost considerations of saltwater desalination systems in rural India.
They found that although the cost of photovoltaic-electrodialysis technology is lower than that of solar reverse osmosis (PV-RO) systems. However, compared with grid-driven reverse osmosis (on-grid RO) systems, the cost advantages are not outstanding enough.
The fact that on-grid RO systems have been commercialized in rural India suggests that PV-electrodialysis technology has not yet reached an acceptable cost in the market, or that it is not yet possible to form a local business model for a saltwater desalination system.
Although the cost of the first prototype system has not yet reached the level of commercialization, the field test in India not only confirmed their design theory, but also provided valuable field information.
Based on this information, the research group further innovated the electrodialysis technology and proposed a more flexible electrodialysis technology that can flexibly adjust the water yield according to the changes in solar energy supply.
随后，他们在印度微咸水地下水国家海水淡化研究设施（Brackish Groundwater National Desalination Research Facility）上，建造了新的原型系统。
And use the relevant test platform to monitor and evaluate the technology more accurately.
The test results show that the energy efficiency of the system has been significantly improved, and 77% of the available solar energy has been directly utilized. This is 91% higher than traditional systems and 92% less battery dependence.
When these field test results were combined with the team's understanding of village-scale desalination projects in India, they found a 22% reduction in water costs, which makes the technology comparable to the on-grid RO systems that are currently widely used.
（来源：Nature Water）
During the field trip to India, when the first prototype system was being tested, something happened that made He Wei feel very "against common sense".
During the test, the entire system was powered by solar photovoltaic panels. However, the lights at the experimental site are connected to the grid and will only automatically connect to the solar system when the power is cut off, and will make a "beep" sound when switching.
This makes them feel grid outages more frequently. Especially at night, it is often only their "family" that is lit up.
"The intermittency of new energy, which was once criticized, has become a reliable source of power here, while the power grid, which is supposed to be stable in many countries, has become a veritable intermittent energy source. He said.
This experience strengthened his and his collaborators' understanding of the new energy source, which is that although the sun is a distributed energy source, it can significantly improve the stability of energy supply in remote areas.
In the next step, they plan to expand the application of flexible electrodialysis technology beyond saltwater desalination.
Considering the versatility and efficiency of electrodialysis technology, its potential applications in different fields can undoubtedly bring significant positive impacts, such as agricultural irrigation, lithium extraction from salt lakes, and the use of liquid alkali to capture carbon dioxide.
The new energy industry chain is mainly concentrated in China, and we look forward to cooperating with domestic units
It is also reported that as a native of Xi'an, although he does not live in a city near the sea. However, it was during his studies in Xi'an that He Wei began to learn about seawater/salt water desalination technology.
He graduated from Xi'an Jiaotong University with a bachelor's degree and a master's degree, and received his Ph.D. from Queen Mary, University of London.
He said: "Although I felt a little lost when I applied for the college entrance examination, I may have been affected by environmental reports since I was a child, and I have a vision for the future: new energy will become a key technology in the future. ”
Guided by this belief, he chose Xi'an Jiaotong University to major in energy and power engineering.
During his graduate studies, he participated in a research project on water treatment funded by a company, where he was first introduced to seawater and brackish water desalination technology, and began to explore how to obtain fresh water from brine more efficiently from an energy perspective.
After coming to the UK to study for a PhD, he further studied the integration mechanism and application of seawater desalination technology and a variety of new energy sources.
During his postdoctoral fellowship at the Massachusetts Institute of Technology, he shifted his research focus to solar electrodialysis.
"It was my research in this area that led me to a Research Fellowship grant from the Royal Academy of Engineering and to begin my research career as an independent PI. It said.
As a key hard technology, energy technology covers a large number of hardware and software research and development in the context of intelligence and digitalization.
Especially in the process of technology industrialization, hardware development inevitably needs to rely on the support of the industrial chain and supply chain.
At present, the new energy industry chain is mainly concentrated in China, and he is full of great interest in exploring and establishing new energy industry transformation opportunities, including new electrodialysis technology. At the same time, we are also looking forward to cooperation with domestic universities and enterprises. He said.
Resources:
1.He, W., Le Henaff, AC., Amrose, S.et al. Flexible batch electrodialysis for low-cost solar-powered brackish water desalination. Nat Water (2024). https://doi.org/10.1038/s44221-024-00213-w
Typesetting: Luo Yi