Researchers have designed a low-cost modular energy source that can produce energy efficiently at night. The system uses commercially available technology and can ultimately help meet the need for night lighting in urban areas or provide lighting in developing countries.
Although solar energy brings many benefits, its use depends heavily on the distribution of sunlight, which can be limited in many places and is completely unavailable at night. Systems that conserve energy produced during the day are usually expensive, thus increasing the cost of using solar energy.
To find a less expensive alternative, researchers led by Shanhui Fan of Stanford University looked at radiant cooling. This approach uses the temperature change coming from the heat absorbed by the surrounding air and the cooling radiant effect of the cold space to generate electricity.
In the journal Optical Society (OSA) Optics Express, researchers theoretically demonstrate an optimized approach to radiant cooling that can generate 2.2 Watts per square meter with a roof device that does not require a battery or any external power. This is about 120 times the amount of energy that has been demonstrated experimentally and enough to power modular sensors such as those used in security or environmental applications.
“We are working to develop a sustainable high-performance lighting product that can provide access to reliable and sustainable lighting sources for everyone, including those in developing and rural areas.” low cost, “said Lingling Fan, the first author of the paper. “A modular power source can also power off-grid sensors used in a variety of applications and be used to convert waste heat from vehicles into usable power.”
Maximizing power generation
One of the most efficient ways to generate electricity using radiant cooling is to use a thermoelectric power generator. These devices use thermoelectric materials to generate energy by converting temperature changes between a heat source and the cold side of the device, or radiant coolant, into an electrical voltage.
In the new work, the researchers optimized each step of generating thermoelectric energy to maximize overnight power output from a device to be used on a roof. They improved the energy harvest so that more heat flowed into the system from the surrounding air and incorporated new commercially available thermoelectric materials that increase how well that energy is used by the device. They also calculated that a thermoelectric power generator covering one square meter of a roof could achieve the best trade-off between heat loss and thermoelectric conversion.
“One of the most important innovations was the design of a selective emitter that is glued to the cold side of the device,” said Wei Li, a member of the study team. “This optimizes the radiant cooling process so that the power generator can remove more efficiency from excess heat.”
The researchers demonstrated the new approach using computer modeling to simulate a system with realistic physical parameters. The models faithfully reproduced previous experimental results and found that the optimized system created by the researchers could be approximated to what is calculated as maximum efficiency using thermoelectric conversion.
In addition to conducting experiments, researchers are also examining optimal plans for the operation of the system during the day, except at night, which may expand the practical applications of the system.
Cooling mechanism increases solar energy collection for self-powered outdoor sensors
Lingling Fan et al, Maximum night power generation through optimal radiant cooling, Optics Express (2020). DOI: 10.1364 / OE.397714
Provided by the Optical Society
citation: Researchers design an efficient low-cost system for overnight power generation (2020, August 13) taken on August 13, 2020 from https://phys.org/news/2020-08-efficient-low-cost-power- night.html
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