The challenge of solar-powered energy has always been the means to store it. And the intermittency of solar and wind energy makes that storage capability essential. Energy from the sun and wind can only be created — and stored — when the sun shines or the wind blows.
But that technological gap may be closing thanks to scientists at the University of California, Santa Barbara, who have created a “rechargeable solar battery” that stores sunlight in molecules and later releases enough heat to boil water.
The scientists started with the assumption that solar panels lose their ability to generate electricity after sunset; the challenge was to store solar power for use later, whether during cloudy weather or overnight.
According to Science Daily,
Researchers at UC Santa Barbara believe they may have found an answer that avoids the need for massive battery systems or reliance on the electrical grid. Writing in the journal Science, Associate Professor Grace Han and her research team describe a new material capable of absorbing sunlight, storing that energy in chemical bonds, and later releasing it as heat whenever needed. The material is based on a modified organic molecule called pyrimidone and represents a new step forward in Molecular Solar Thermal (MOST) energy storage technology.
The invention is inspired by DNA. The pyrimidone structure resembles a component found naturally in DNA — the hereditary material in human beings and all other living organisms — that can reversibly change shape when exposed to ultraviolet light.
Using a synthetic version of that structure, the team engineered a molecule capable of repeatedly storing and releasing energy… the material could retain stored energy for years without significant loss.
According to Science Daily, a key milestone for the team involved turning the molecule’s energy storage capacity into a practical demonstration.
“Boiling water is an energy-intensive process,” said Han Nguyen, a doctoral student in the Han Group and lead author of the study.
“The fact that we can boil water under ambient conditions is a big achievement.”
“We typically describe it as a rechargeable solar battery,” Nguyen added. “It stores sunlight, and it can be recharged.”
According to the researchers, the battery packs an energy density punch. It stores more than 1.6 megajoules of energy per kilogram, compared to a lithium-ion battery that stores roughly 0.9 MJ/kg.
Potential uses include off-grid heating systems for camping, or home water heating. Also:
Because the material dissolves in water, researchers say it may someday circulate through rooftop solar collectors during the day before being stored in tanks that release heat at night.
“With solar panels, you need an additional battery system to store the energy,” said co-author Benjamin Baker, a doctoral student in the Han Lab. “With molecular solar thermal energy storage, the material itself is able to store that energy from sunlight.”
Storage technologies most frequently coupled with solar power plants are electrochemical storage (batteries) with PV plants and thermal storage (fluids) with Concentrated Solar Power (CSP) plants. (U.S. Department of Energy)
Electrochemical batteries are like those found in laptops and mobile phones. When electricity is fed into a battery, it causes a chemical reaction, and energy is stored. When a battery is discharged, that chemical reaction is reversed, which creates voltage between two electrical contacts, causing current to flow out of the battery. The most common chemistry for battery cells is lithium-ion, but other common options include lead-acid, sodium, and nickel-based batteries.
In thermal energy storage systems, the heat stored in fluids like water or molten salt is used to boil water. The resulting steam drives a turbine and produces electrical power. Thermal energy storage is useful in CSP plants, which focus sunlight onto a receiver to heat a working fluid.
As my colleague Felicity Bradstock recently reported, the limitations of lithium-ion batteries — for one, lithium is a finite resource — have encouraged researchers to explore more sustainable alternatives.
Chinese researchers have taken a major step forward in the production of an alternative alkaline all-iron flow battery, developed using low-cost, abundant materials and a water-based electrolyte that cannot explode. According to a report published in Advanced Energy Materials, the battery is capable of over 6,000 charge-discharge cycles without measurable capacity decay, equivalent to around 16 years of daily use.
Because iron is one of the most abundant elements on the planet, the team from the Institute of Metal Research under the Chinese Academy of Sciences is hopeful that the battery will offer a more sustainable, long-term alternative to lithium-ion batteries. In addition, iron is far cheaper than raw lithium, by around 80 times. Flow batteries work using liquid electrolytes held in external tanks and pumped through a cell stack. To increase capacity, companies must simply construct larger tanks, making it highly appealing to wind and solar energy producers, although it is not viable to use these batteries in smaller electronics.
By Andrew Topf for Oilprice.com
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