The solar revolution won't be just about the electricity gridWe've been writing a lot about the historic drought that California has been going through and all the damage that it is doing... Looking at the problem is important, but figuring out what's the best solution is even more important. So far we've seen big pushes for increased efficiency/conservation, including mandatory cuts in water usage, but we haven't looked too much at the other side of the supply-demand equation.
What if instead of just pushing for more conservation and hope for rain we could also create more freshwater in a way that is environmentally responsible?
That's the big problem, right. Just drilling for water is not sustainable because we end up using the water faster than it replenishes, messing with rivers has all kinds of unintended consequences, traditional desalination uses a lot of energy, which is usually from dirty sources, etc. But what if there's another way?
The argument that some people are making, including those at WaterFX, a company that makes solar-powered desalination plants, is that solar is getting cheap enough now that it can be used to desalinate vast quantities of water, enough to make places like California less vulnerable to droughts.
After all, the Earth isn't short on water. There's plenty of that! It's freshwater that is problematic, because it's rarer and not evenly distributed along with the population and agriculture.
WaterFX wrote a very interesting blog post (take it with a grain of salt - sorry about that bad pun - because they do sell desalination equipment, but it does make a lot of sense) which basically runs through the situation and our options. They use Israel as an example of what desalination technology can do, allowing that originally very dry country to turn into a net freshwater exporter.
Here are a few excerpts, but I encourage you to read the whole thing if you are interested in the issue.
Desalination is contentious, especially as a broad‐based water solution for California. The most common objections are the high cost and environmental impact. But contrary to popular belief, the cost of not considering desalination is much larger and so are the potential environmental consequences. When we evaluate the cost of desalinated water, we are not talking simply about the cost of a gallon of H2O, we are weighing the economic value of a gallon of water against our productivity (or inversely the lost productivity without it). When we analyze environmental impact, we are not examining solely the local impact of a desalination plant; we are broadly minimizing the irreversible deterioration to our habitat from over‐drafting the water supply.
This is a good point. The alternative to solar desalination is not nothing, it is more of what we've been doing so far, which is damaging underground water reservoirs, rivers, etc.
Irrigated farmland is the single largest use of water in California (approximately 40‐50% when you exclude environmental allocations), so this is an ideal place to start. The conclusion that we came to, if implemented properly, is that solar desalination can be highly profitable. [...] A Concentrated Solar Still (CSS), therefore, is a way to increase the production using concentrating solar energy to generate higher temperatures (up to 350 degrees C) allowing the heat to be efficiently recycled. With this approach, the performance of a simple solar still is increased by a factor of thirty, providing 600 gallons of freshwater per square foot per year. [...]
This means that an acre of solar desalination can satisfy the water needs of forty acres of irrigated farmland. This is an extremely attractive land utilization factor because only two percent of the land needs to be dedicated to water production and this multiple will improve. With access to an abundant source of saltwater, an area encompassing two square miles would provide 100 million gallons per day; sufficient fresh water for a city the size of Las Vegas (600,000 people).
What changes the game with desalination is solar power. If this had to be run on fossil fuels, we'd just be contributing to another problem. But once enough solar desalination capacity has been built, the "fuel" (sunlight) is free forever, and the impact is minimal, especially compared to most of the alternatives.