Article originally
published on thinkprogress in July 23th 2015.
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| The parabolic solar panels at WaterFX's demonstration solar desalination plant in California's Panoche Water and Drainage District. |
Solar power turns the sun’s energy into electricity.
Desalination removes unwanted minerals from saltwater so it can be used for
drinking or agriculture.
These two technologies have typically been employed
separately in the effort to live more sustainably and limit dependence on
finite resources. Now in California, a company has found a way to merge the two
with the aim of providing long-term relief to farmers suffering the impacts of
the state’s devastating four-year drought. The implications are far-reaching,
as agriculture accounts for 80 percent of water use in California and roughly
70 percent of water use globally. In California alone, there is an estimated
one million acre-feet of irrigation drainage that could be treated and reused
if solar desalination catches on.
“Conserving or recycling even a small share of this
water can make a big difference,” Sandra Postel, director of the Global Water
Policy Project and a Freshwater Fellow of the National Geographic Society, told
ThinkProgress.
WaterFX, a San Francisco-based water producer for
agricultural and commercial users, recently announced that its California
subsidiary, HydroRevolution, plans to build the state’s first commercial solar
desalination plant. To be located in the agriculture-intensive Central Valley,
the plant will ultimately generate up to 5,000 acre-feet, or 1.6 billion
gallons, of clean water per year — enough water for 10,000 homes or 2,000 acres
of cropland. It will be built on 35 acres of land currently used to grow
salt-tolerant crops, and will recycle unusable irrigation water from a
7,000-acre drainage area into a new and much-needed source of freshwater for
nearby water districts by removing unwanted mineral and salts.
It could be a win-win for farmers and the environment.
Using something called Aqua4 technology, the
desalination process creates zero excess discharge and produces only freshwater
and solid salt as co-products. This differs from traditional desalination where
up to half the discharge ends up as brine back in the ocean.
This is not the only way solar desalination differs
from traditional reverse osmosis desalination projects, where sea water is the
main input. There are currently several of these large-scale projects in use or
under construction along the California coastline. Conventional desalination
plants force salt and other minerals through a membrane; they are
energy-intensive and can also harm marine life and disturb coastal ecosystems.
The solar desalination plants developed by WaterFX use solar thermal energy to
avoid the use of fossil fuel-powered electricity.
“The energy intensity of conventional reverse osmosis
plants has dropped considerably over the last two decades, but they still have
a relatively high energy price tag compared to other water supply and demand
management strategies,” said Postel. “I see no elegance in a technology aimed
at ensuring there’s enough drinking water during droughts if it employs a
process that will hasten climate change, which in turn will worsen droughts.”
Postel said WaterFX’s technology has several
advantages, including “not contributing to climate change,” cleaning up local
salty, toxic irrigation drainage, and being more cost-effective. She said while
she hasn’t done an independent cost comparison, she’s read that solar
desalination produces clean water at rough one-fourth the cost of conventional
desalination.
“Lastly, it’s super exciting to me because it opens up
the possibility of farmers and irrigation districts leasing some water back to
the environment,” said Postel. “It could be a win-win for farmers and the
environment” if they could lease some water “to safeguard habitats for fish and
wildlife.”
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The Aqua4 technology at WaterFX’s demonstration solar desalination plant in California’s Panoche Water and Drainage District.
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The solar desalination technology is also “modular and
movable,” Ivy Wisner with the WaterFX communications team told ThinkProgress.
“The equipment is delivered in modules and mounted on
skids so installation is easy and equipment can be moved depending on water
treatment needs,” she said.
According to WaterFX, the HydroRevolution system is
the most efficient of its type available. It uses heat generated from parabolic
solar panels to evaporate clean water out of the original source water. The
condensate is then recovered as pure water at over 90 percent efficiency. When
the sun isn’t shining, thermal heat storage used to hold excess heat allows the
process to continue.
“WaterFX hopes this project is merely the first step
in revolutionizing the way California uses water,” said Wisner.
WaterFX Co-founder and Chairman Aaron Mandell, who
studied groundwater engineering, told ThinkProgress that in order to confront
climate change, any solution to the water crisis must be long-term.
“Droughts come and go, but the water problem in
California is driven by climate change,” he said. “While lack of rain is
temporary, elevated temperatures due to a warming climate is permanent and as a
result will have a long-lasting impact on the amount of available water.”
WaterFX’s mission is to expand the availability and
reliability of freshwater generation — very few places need this more than
right now than California’s dried-out Central Valley. In some places in the Central
Valley, groundwater tables have dropped 50 feet or more in just a few years,
and many shallower wells have run dry.
While the HydroRevolution plant is currently in
pre-production and seeking investors, WaterFX installed a demonstration plant
in the Panoche Water and Drainage District in the Central Valley, where the
federal Bureau of Reclamation has cut back water deliveries from dams and
canals by up to 80 percent. Central Valley water districts are also under
pressure to limit polluted irrigation runoff from their fields into the San
Joaquin River. The solar desalination plants could also provide a fix to this
issue.
“The technology is being piloted in the perfect place
for it,” said Postel. “The drainage water from irrigation in this western side
of the San Joaquin River in the Central Valley has an unusually high load of
salts, selenium, and other contaminants.”
As the Central Valley publication Ag Alert recently
reported, the plant “will help the district clean up salts, selenium, boron and
other minerals in tile-drain water coming from irrigated fields and reach its
goal of zero agricultural water being discharged into the San Joaquin River by
2019, which is required by an agreement with federal agencies.”
Part of HydroRevolution’s innovative approach to the
solar desalination project is to pursue a crowdsourcing effort, or
capital-raising campaign, that will be available to California residents only.
It is still in the preparatory stages.
Postel considers WaterFX’s approach one way of
confronting the bigger challenge of repairing the overall water cycle.
“Our approach to water management has been very
disruptive of the natural water cycle and all the benefits that cycle
provides,” she said.
Other avenues that can aid in this process include
better storm water management, green infrastructure that helps rainwater
infiltrate back into the earth, and wastewater recycling and reuse.
“We still have a long way to go with water
conservation and efficiency improvements,” she said. “Both indoors and
outdoors.”
