太陽海淡新解

在全球淡水壓力持續升高、傳統海水淡化技術飽受高能耗與高鹵水排放爭議之際，美國羅徹斯特大學（University of Rochester）研究團隊提出一種新型太陽能海水淡化系統，試圖改寫淡化技術的成本與環境方程式。這套系統結合特殊黑化金屬表面、超親水導液結構與太陽熱蒸發機制，不僅能以陽光驅動海水轉化為淡水，還可在幾乎不產生液態廢鹵水的情況下，將鹽分與部分高價值礦物集中回收，展現出兼顧水資源供應、污染減量與資源循環的潛力。

A research team at the University of Rochester has developed a solar-powered desalination system that could offer a lower-energy and lower-waste alternative to conventional seawater treatment. By combining a laser-textured black metal surface with solar-thermal evaporation and a salt-separation design, the system can generate freshwater from real seawater while preventing salt buildup, eliminating liquid brine discharge and opening the door to mineral recovery from saline water streams.

目前主流海水淡化技術多仰賴反滲透（reverse osmosis）或熱蒸餾（thermal distillation）等路徑，雖已具備成熟商業化基礎，但也面臨兩大結構性限制。首先，系統通常需要大量電力或熱能支持，導致能源成本高昂，並使淡化廠的營運高度依賴電網與燃料供應。其次，淡化過程會產生高濃度鹵水（brine），若大量排回海洋，可能提高近岸海域鹽度、降低溶氧量，進一步衝擊海洋生態系統。對於缺水卻同時能源與環境承載能力有限的地區而言，這使傳統淡化技術在擴張時面臨越來越大的可持續性壓力。

The development comes as water scarcity intensifies globally and conventional desalination faces mounting scrutiny over its environmental footprint. Existing technologies, particularly reverse osmosis and thermal distillation, are effective at producing freshwater but are energy-intensive and generate concentrated brine that is often discharged back into marine environments. That waste stream can raise salinity levels and reduce oxygen content in coastal waters, creating ecological risks and increasing the long-term sustainability burden of large-scale desalination.

太陽能蒸發式海水淡化因而被視為替代方案之一，其核心概念是利用太陽熱將海水蒸發，再冷凝成淡水，以降低對外部能源的依賴。然而，這類系統長期面臨的瓶頸在於鹽類與礦物沉積。當水分蒸發後，鹽分會殘留於蒸發表面並逐漸堆積，進而堵塞孔隙、阻礙水分輸送並削弱蒸發效率。若使用真實海水而非實驗室中的單純鹽水，問題更為複雜，因為海水中還含有鈣、鎂等多種離子，容易形成更難清除的沉積層，最終使系統性能快速衰退。

Solar desalination has long been seen as a promising alternative because it uses sunlight rather than grid electricity or fossil fuels to evaporate water and then condense it into freshwater. However, one of the biggest technical barriers has been salt accumulation. As water evaporates, salts and minerals remain behind and gradually clog the evaporation surface, reducing efficiency and eventually halting the process. This problem becomes even more severe when treating real seawater, which contains a complex mix of dissolved minerals such as calcium and magnesium in addition to sodium chloride.

為解決這一難題，羅徹斯特大學團隊開發出一種經超快雷射處理的黑化金屬表面。該材料具備高度光吸收能力，可將絕大部分入射陽光轉化為熱能，同時表面又具有「超導液（superwicking）」特性，能迅速將海水均勻鋪展成薄層，提升蒸發效率。更關鍵的是，研究團隊將蒸發裝置分為主動蒸發區與被動鹽分收集區，藉由液體蒸發過程中的流動特性，引導鹽類從中心蒸發區向外緣遷移，使鹽分優先沉積在被動區域，而非堵塞核心蒸發表面。

To address this, the Rochester team engineered a black metal surface using ultrafast laser treatment. The resulting material has two key properties: it absorbs nearly all incoming sunlight and converts it into heat, and it is “superwicking,” meaning it can rapidly spread water into a thin film across the surface. This improves evaporation efficiency while also enabling more precise control over where dissolved salts accumulate.

The system is divided into an active evaporation region and a passive salt-collection region. As water evaporates, dissolved salts are driven outward and deposited in the passive zone instead of building up on the active surface. The design makes use of the so-called coffee-ring effect, in which particles migrate to the edge of a drying droplet. By exploiting this natural phenomenon, the system keeps the main evaporation area cleaner for longer and avoids one of the most persistent causes of solar desalination failure.

這套設計實際上利用了日常生活中常見的「咖啡環效應」（coffee ring effect）——液滴蒸發時，顆粒會往邊緣集中，形成外圈沉積。研究團隊將這一自然現象轉化為工程化控制機制，使蒸發表面得以維持較長時間潔淨運作，降低因結晶堵塞造成的效率損失。對海水淡化系統而言，這代表其有機會擺脫過去「效率高但容易積鹽失效」的技術困境，朝向更穩定的連續運轉邁進。

In tests using real seawater samples from the Pacific, Atlantic and Indian Oceans, the system maintained stable performance while producing freshwater and directing salts away from the evaporation surface. According to the researchers, the process does not rely on chemical activating agents, which could improve both its environmental profile and its economic feasibility compared with other advanced treatment systems.

研究團隊以來自太平洋、大西洋與印度洋的真實海水樣本進行測試，結果顯示該系統在不同海水成分條件下均能穩定產出淡水，並將鹽分有效導向被動區域收集，而非在主蒸發面形成致命堵塞。更重要的是，這一過程不需額外使用化學活化劑或強氧化藥劑，有助降低二次污染風險與後端處理成本。從工程放大的角度來看，這類「低化學投入、低維護負擔」的設計，對偏遠地區、島嶼型社區及水資源基礎設施不足的區域尤其具有吸引力。

One of the most commercially and environmentally significant aspects of the technology is its zero-liquid-discharge potential. Instead of producing concentrated liquid brine that must be disposed of, the system captures salts in solid form, making them easier to handle and potentially reusable. That changes the economics of desalination by reframing waste not merely as a disposal problem, but as a recoverable resource stream.

除了淡水生產，該技術另一項值得關注的突破，在於其「零液體排放」（zero-liquid-discharge）與礦物回收的雙重潛力。傳統海淡廠往往必須處理大量高濃度鹵水，而新系統則可將鹽類以固體形式回收，減少液態廢棄物排放。進一步來看，海水與鹽湖鹵水中並不只有氯化鈉，還含有鋰等對能源轉型至關重要的礦物。研究團隊在另一項相關研究中指出，若在材料表面加入特定奈米粒子，系統還能從鹽水中分離並回收鋰資源，於大鹽湖（Great Salt Lake）水樣測試中已展現一定回收效率。這使該技術的定位不再只是「製水設備」，而是可能升級為結合淡水供應、鹽分管理與關鍵礦物提取的多功能資源平台。

The implications may extend beyond water production. In related work, the research team showed that by integrating specialized nanoparticles into the surface, the same platform could selectively recover lithium from saline water sources such as the Great Salt Lake. That capability could be particularly relevant as demand for battery minerals continues to rise alongside electric vehicles and energy storage systems. If the technology can eventually combine freshwater production with mineral extraction at scale, it could become part of a broader circular resource model linking water security, industrial decarbonization and critical materials supply.

從產業與政策層面來看，這項技術的意義不僅在於提升海水淡化效率，更反映全球水資源治理正在從「單一供水問題」轉向「水、能源、材料」整合管理的新階段。隨著氣候變遷加劇乾旱風險、資料中心與製造業擴張推升用水壓力，以及鋰等關鍵礦物需求因電動車與儲能產業快速成長而攀升，未來能同時解決淡水供應、減少污染並回收戰略資源的技術，將更具投資與部署價值。對沿海國家、海島經濟體與缺水工業聚落而言，若此類太陽能淡化技術後續能完成規模化驗證與成本優化，將有望成為下一代分散式水處理與資源循環基礎設施的重要選項。

For industry and policymakers, the research highlights a growing shift in desalination strategy: away from stand-alone water treatment and toward integrated systems that simultaneously address water scarcity, waste minimization and resource recovery. If the technology can be scaled economically, it could offer a compelling solution for coastal communities, remote regions, island economies and industrial sites seeking resilient freshwater supplies without the environmental burden associated with conventional brine-intensive desalination.