Though solar energy may seem to many like a relatively recent technology, the United States Patent and Trademark Office issued the first patent for solar-powered devices in 1879 to inventor Edward Weston. 40 years earlier, French physicist Edmond Becquerel discovered the photovoltaic effect—the phenomenon where exposure to light can create voltage and electrical current in certain materials—setting the stage for the next 200 years of solar innovation.
During the 20th Century, rising costs of traditional energy sources and eventual concern over the impacts of climate change drove substantial innovation in solar electricity generation. The first solar cells installed in the United States—on a New York City rooftop in 1883—had a 1-2% energy conversion rate. Today’s panels generally achieve a conversion rate of 15-20%.
Solar electricity generation is now a mainstay of energy production. In 2019, eight U.S. states generated more than 5% of their electricity from solar. California led the pack with 19%. Much has also changed with respect to the solar panel design. For example, homeowners may now opt for solar roof developed by Tesla, combining rooftop and solar panel installation into one.
Growing international concerns over clean water and food security have led not just to increasing efforts to make solar electricity generation more efficient but also to develop applications that, in a sense, cut out the middleman. Using solar-generated electricity to power a water desalination system is great. But what if the sun could simply make the clean water?
Using Solar Energy to Create Clean Water
Solar desalination—using solar power to purify non-potable water sources like seawater or contaminated water—is a critical element of efforts both in the United States and internationally to address growing concerns about the availability of clean water. The U.S. Department of Energy’s ongoing solar desalination funding program aims to encourage innovations that reduce the cost of these systems and make them smaller and more portable.
But solar desalination still requires that water be available, a need that can limit its usability in some areas of the world. And the process requires a significant amount of energy.
A U.S. startup, Zero Mass WaterTM, has developed a product—called SOURCE arrays—that cuts out the need for existing water at all and instead pulls moisture directly from the air to create between four and ten liters of water each day.
The SOURCE arrays use two hydropanels that create condensation by converting the sun into energy that heats the spongy, absorbent material inside the array. A fan pulls in air from the surrounding environment and blows it through pores within the material, which then collects water at 20,000 times the concentration of vapor in the air.
A 30-liter reservoir holds the water while minerals (for taste) and ozone (for purity) are added. The water can be pumped straight to a household’s faucet or a refrigerator’s fill station—all off the grid. Each array includes a microchip that allows Zero Mass Water to maximize efficiency by collecting data on temperature, humidity, and water output.
The company has a growing patent portfolio for their solar technology, including US Patent No. 10,357,739 and has installations in more than 35 countries.
Solar Thermal Panels for Heat Generation
In the same way that scientists are developing solar technologies that convert solar energy straight into water, solar thermal panels cut out the need for electricity generation by converting solar energy directly into heat.
Solar thermal systems include a collector, generally a glass tube, that uses the sun to heat a transfer fluid (generally a mixture of glycol and water) that runs via a pump from the collector to a heat exchanger in a hot water cylinder. After the heat from the exchanger increases the temperature of the water inside the cylinder, the transfer fluid flows back to the collectors to be heated again. In climates that never drop below freezing temperatures, some solar thermal systems pump heated water directly into the home’s cylinder.
Dozens of different solar thermal panels have been developed. For example, a patent search for “solar thermal panels” generates over 200 results. Yet there’s still room for improvement regarding their efficiency, cost effectiveness, and lower material demand.
These systems are used primarily in residential settings to create hot water for household use. They are also very effective at heating pools—in fact, the U.S. Department of Energy has called solar pool heating “the most cost-effective use of solar energy in many climates.”
Solar Energy for Simultaneous Processes
Regardless of the desired output—electricity, heat, water—reducing the cost and increasing the efficiency of conversion continue to be drivers of solar innovation. The examples above achieve these goals by cutting out the electricity generation component but another method is to develop systems that can harness the sun’s energy to do two things at once, often by using the waste heat from a cycle to perform a different task rather than allowing it to release into the environment.
By installing a device on the back of solar cells that can recycle the latent heat of an electricity generation process, researchers at King Abdullah University of Science and Technology in Saudi Arabia have developed panels that can distill seawater while simultaneously generating electricity. The solar cells’ electricity conversion rate is slightly lower than an average solar cell—around 10%—but one square meter of the installation can simultaneously distill over 1.6 liters of seawater in an hour. To review the growing solar desalination patent portfolio of the University, click here.
This type of innovation could have applications for solar-powered devices of all types, raising overall efficiency rates and reducing the cost of solar solutions while providing resources such as potable water to entire communities. Thus, what had started with the discovery of the photovoltaic effect in mid-19th century has been gaining momentum. This trend is bound to continue due to rising environmental consciousness, public needs, financial grants, and intellectual property services providing legal protection for the inventive efforts.