水時代－人類美好未來

技術專家傾向於關注最珍貴或技術上最有用的自然資源和商品，例如黃金、稀土或鋰。然而，每天需要大量簡單得多的資源來維持我們的文明：淡水。

Investors and technologists tend to focus on the most precious or technically useful natural resources and commodities, such as gold, rare earth, or lithium. However, a much simpler resource is needed in massive amounts daily to sustain our civilization: fresh water.

投資者和技術專家傾向於關注最珍貴或技術上最有用的自然資源和商品，例如黃金、稀土或鋰。然而，每天需要大量簡單得多的資源來維持我們的文明：淡水。

While it literally falls from the sky in most of the world, its availability is still under severe pressure in modern civilization, as we consume much of it for industry, agriculture, and human needs.

雖然它在世界大部分地區實際上是從天上掉下來的，但在現代文明中，它的可用性仍然面臨著巨大的壓力，因為我們將其大部分用於工業、農業和人類需求。

Only 3% of the world’s water is usable fresh water, with 97% being saline (saline groundwater and seawater). Of this freshwater, 69% is held in glacier and polar ice caps, 30% is groundwater, and only 1% is surface water.

世界上只有 3% 的水是可用的淡水，97% 是鹹水（含鹽地下水和海水）。其中 69% 的淡水存在於冰川和極地冰蓋中，30% 是地下水，只有 1% 是地表水。

Source: USGS

資料來源：美國地質調查局

As a result, in many places, the only available water source is saline. Desalination is possible but requires a tremendous amount of energy. Until now, it has often been done with fossil fuels, as most desalination techniques are energy-intensive and require constant and stable energy inputs.

因此，在許多地方，唯一可用的水源是鹽水。海水淡化是可能的，但需要大量的能源。到目前為止，海水淡化通常使用化石燃料來完成，因為大多數海水淡化技術都是能源密集的，需要持續穩定的能源輸入。

This could change, thanks to a new method developed by MIT engineers and published in Nature Water under the title “Direct-drive photovoltaic electrodialysis via flow-commanded current control.”

這種情況可能會改變，這要歸功於麻省理工學院工程師開發的一種新方法，並以「透過流量命令電流控制進行直接驅動光伏電滲析」為題發表在《自然水》上。

Solar Desalination

太陽能海水淡化

At first glance, solar power seems to be the most logical energy source for powering desalination operations. Not only is it provided for free by the Sun, but it is also generally abundant in dry regions like deserts, which often need desalination the most.

乍一看，太陽能似乎是為海水淡化作業提供動力的最合理的能源。它不僅由太陽免費提供，而且在沙漠等乾燥地區通常也很豐富，這些地區通常最需要海水淡化。

With solar power becoming cheaper by the day, it will likely continue to grow as an energy source, as we covered in our article “The Solar Age—A Bright Future To Mankind.”

隨著太陽能變得越來越便宜，它作為一種能源可能會繼續增長，正如我們在《太陽能時代——人類光明的未來》一文中所討論的那樣。

There is still one problem – solar energy is only produced when the sun shines. This means that to operate efficiently, most solar-power-only desalination operations would need to be coupled to a battery system, increasing costs.

還有一個問題──太陽能只有在陽光照射時才會產生。這意味著為了有效率地運行，大多數僅使用太陽能的海水淡化作業需要與電池系統結合，從而增加了成本。

This is especially problematic for current desalination techniques, like reverse osmosis, which needs stable conditions and a stable energy supply to be efficient. This is because it requires constant pressure on the osmosis membranes.

這對於目前的海水淡化技術（例如逆滲透）來說尤其成問題，因為該技術需要穩定的條件和穩定的能源供應才能有效。這是因為它需要滲透膜上有恆定的壓力。

This precludes any small-scale desalination and any low-cost methods, at least as long as energy storage is still expensive. This might change, as we discussed in “The Future Of Energy Storage—Utility-Scale Batteries Tech”; still, it could be better to also adapt to the natural fluctuation of solar power, including very short-term ones like clouds passing by.

這排除了任何小規模海水淡化和任何低成本方法，至少在能源儲存仍然昂貴的情況下。正如我們在「儲能的未來——公用事業規模電池技術」中討論的那樣，這種情況可能會改變；儘管如此，最好也能適應太陽能的自然波動，包括非常短期的波動，例如雲層經過。

Flexible Batch Electrodialysis

靈活的間歇式電滲析

The MIT researchers favored this approach. They studied electrodialysis, an alternative method to reverse osmosis for desalination. Electrodialysis uses an electric field to draw out salt ions as water is pumped through a stack of ion-exchange membranes.

麻省理工學院的研究人員贊成這種方法。他們研究了電滲析，這是一種逆滲透海水淡化的替代方法。當水被泵送通過一堆離子交換膜時，電滲析利用電場提取鹽離子。

Source: Nature Water

來源：自然水

For their new design, they created a model-based control system connected to sensors in all parts of the system. It predicted the optimal rate at which to pump water and the voltage that should be applied to maximize the amount of salt drawn out of the water.

對於他們的新設計，他們創建了一個基於模型的控制系統，連接到系統所有部分的感測器。它預測了抽水的最佳速率以及為最大限度地從水中提取鹽量而應施加的電壓。

By doing so, the desalination operation could fluctuate according to the solar power produced in real-time.

透過這樣做，海水淡化操作可以根據即時產生的太陽能而波動。

Source: Nature Water

來源：自然水

On average, the system directly used 77 percent of the available electrical energy produced by the solar panels, which the team estimated was 91 percent more than traditionally designed solar-powered electrodialysis systems.

平均而言，該系統直接使用了太陽能電池板產生的 77% 的可用電能，該團隊估計這比傳統設計的太陽能電滲析系統多出 91%。

Further Improvement

進一步改進

The almost doubled rate of solar power utilization compared to previous electrodialysis systems could still be improved with more regular optimization & automation:

與以前的電滲析系統相比，太陽能利用率幾乎翻了一番，但仍可透過更定期的優化和自動化來提高：

We could only calculate every three minutes, and in that time, a cloud could literally come by and block the sun.

我們只能每三分鐘計算一次，在那段時間裡，一朵雲其實可以遮住太陽。

The system could be saying, ‘I need to run at this high power.’ But some of that power has suddenly dropped because there’s now less sunlight. So, we had to make up that power with extra batteries.”

系統可能會說：“我需要以如此高的功率運行。”但由於現在陽光減少，部分電力突然下降。因此，我們必須用額外的電池來補充電力。

Amos Winter – Director of the K. Lisa Yang Global Engineering and Research (GEAR) Center at MIT

Amos Winter – 麻省理工學院 K. Lisa Yang 全球工程與研究 (GEAR) 中心主任

This was a proof-of-concept work and will be turned into a commercial design soon, as the team will be launching a company based on their technology in the coming months.

這是一項概念驗證工作，很快就會轉變為商業設計，因為團隊將在未來幾個月內基於他們的技術推出一家公司。

This research project was also supported in-kind (provided material for free) by Veolia Water Technologies and Solutions (VIE.PA) and Xylem Goulds (XYL -1.17%).

研究計畫也得到了威立雅水務技術與解決方案公司 (VIE.PA) 和 Xylem Goulds (XYL -1.17%) 的實體支持（免費提供資料）。

Not Just Seawater

不只是海水

The research team focused on the desalination of brackish groundwater found underground in New Mexico. As many dry area population centers are far from the sea, this can be an important water source currently unavailable due to its salt content.

研究小組專注於新墨西哥州地下發現的鹹水地下水的淡化。由於許多乾旱地區的人口中心遠離大海，由於其含鹽量，這可能是目前無法獲得的重要水源。

“The majority of the population actually lives far enough from the coast, that seawater desalination could never reach them. They consequently rely heavily on groundwater, especially in remote, low-income regions. And unfortunately, this groundwater is becoming more and more saline due to climate change.”

「大多數人口實際上生活在距離海岸足夠遠的地方，海水淡化永遠無法到達他們的身邊。因此，他們嚴重依賴地下水，特別是在偏遠、低收入地區。不幸的是，由於氣候變化，地下水的含鹽量越來越高。

Jonathan Bessette – MIT PhD student in mechanical engineering

Jonathan Bessette – 麻省理工學院機械工程博士生

The research model was already able to provide enough fresh water

研究模型已經能夠提供足夠的淡水