Scientists at Berkeley Labs have developed a “sun umbrella” that could radically reduce the amount of land needed for industrial evaporation ponds. Evaporation ponds are a cheap way to deal with industrial pollution in a variety of industries, including power plants, desalination plants, and the oil, gas and lithium industries. The idea behind the evaporation pond is to create shallow waste water that is naturally evaporated by sunlight and left behind by solid waste that is easier to treat.
The largest evaporation pond sits on the equivalent of hundreds of football fields, sometimes lined up next to each other, forming a huge mosaic that occupies large tracts of land. In addition to their direct impact on the natural environment, evaporation ponds may mislead birds into natural wetlands, where high concentrations of salt and selenium may also pose a direct risk to birds.
The experimental prototype stoussita developed by scientists has a evaporation rate of more than 100% higher than that of a normal evaporation pool, which could mean that the size of the evaporation tank could one day be significantly reduced. This evaporation umbrella works by making water more efficient in absorbing solar radiation in the infrared band. Normal sunlight gradually heats up all the water in the evaporation pool, while infrared light only heats the water surface strongly, at a depth of only about 100 microns. By building a one-foot-per-foot canopy, the incoming sun’s rays will be converted from 400 to 1,500 nanometers to 3,000 nanometers or more, while the evaporation rate increases.
This is not the first attempt to use solar energy to improve evaporation pools, but so far most of the proposals have involved floating sunlight-absorbing materials. The disadvantage, according to researchers at Berkeley Labs, is that they can be blocked by pollutants, so that their performance plummets over time.
The researchers believe that with more work, they may have increased overall evaporation by 160 percent. They also hope to reduce the cost of evaporative umbrellas with cheap polymers. The study, led by Akanksha Menon and Ravi Prasher of Berkeley Labs, was published this week in the journal Nature Sustainability.