A multidisciplinary engineering team at University of California San Diego Jacobs School of Engineering (UCSD) has developed a new nanoparticle-based material designed to absorb and convert to heat more than 90% of the sunlight it captures. The new material can also withstand temperatures greater than 700º C (1292º F) and survive many years outdoors in spite of exposure to air and humidity.

The remarkable new nanoparticle-based material is destined for use in concentrating solar power plants.

The UCSD team’s paper has been published recently in two separate articles in the journal Nano Energy. The effort was funded by the U.S. Department of Energy’s SunShot program.

Sungho Jin, a professor in the department of Mechanical and Aerospace Engineering at UC San Diego Jacobs School of Engineering said, “We wanted to create a material that absorbs sunlight that doesn’t let any of it escape. We want the black hole of sunlight.”

Jin worked with professor Zhaowei Liu of the department of Electrical and Computer Engineering, and Mechanical Engineering professor Renkun Chen, all experts in functional materials engineering.

Nanoparticle-based material for concentrating solar power.  Click image for the largest view.

Nanoparticle-based material for concentrating solar power. Image Credit: UC San Diego Jacobs School of Engineering. Click image for the largest view.

The novel material is a Silicon boride-coated nanoshell material featuring a “multiscale” surface created by using particles of many sizes ranging from 10 nanometers to 10 micrometers. The multiscale structures can trap and absorb light which contributes to the material’s high efficiency when operated at higher temperatures.

Keep in mind current solar absorber materials function at lower temperatures and need to be overhauled almost every year for high temperature operations.

Concentrating solar power (CSP) is an emerging alternative clean energy market that produces approximately 3.5 gigawatts worth of power at power plants around the globe, enough to power more than 2 million homes, with additional construction in progress to provide as much as 20 gigawatts of power in coming years. One of the technology’s attractions is that it can be used to retrofit existing power plants that use coal or fossil fuels because it uses the same process to generate electricity from steam.

Traditional power plants burn coal or fossil fuels to create heat that evaporates water into steam. The steam turns a giant turbine that generates electricity from spinning magnets and conductor wire coils. CSP power plants create the steam needed to turn the turbine by using sunlight to heat molten salt. The molten salt can also be stored in thermal storage tanks overnight where it can continue to generate steam and electricity, 24 hours a day if desired, a significant advantage over photovoltaic systems that stop producing energy with the sunset.

One of the most common types of CSP systems uses more than 100,000 reflective mirrors to aim sunlight at a tower that has been spray painted with a light absorbing black paint material. The material is designed to maximize sun light absorption and minimize the loss of light that would naturally emit from the surface in the form of infrared radiation.

 Graduate student Bryan VanSaders measures how much simulated sunlight a novel material can absorb using a unique set of instruments that takes spectral measurements from visible to infrared.  Click inage for the largest view.

Bryan VanSaders Measures How Much Simulated Sunlight. Image Credit: UC San Diego Jacobs School of Engineering. Click image for the largest view.

The UCSD team’s combined expertise developed, optimized and characterized the new material for this type of system over the past three years. Researchers included a group of UC San Diego graduate students in materials science and engineering, Justin Taekyoung Kim, Bryan VanSaders, and Jaeyun Moon, who recently joined the faculty of the University of Nevada, Las Vegas. The synthesized nanoshell material is spray-painted in Chen’s lab onto a metal substrate for thermal and mechanical testing. The material’s ability to absorb sunlight is measured in Liu’s optics laboratory using a unique set of instruments that takes spectral measurements from visible light to infrared.

Current CSP plants are shut down about once a year to chip off the degraded sunlight absorbing material and reapply a new coating, which means no power is generated while a replacement coating is applied and cured. That’s why DOE’s SunShot program challenged and supported the UCSD research team to come up with a material with a substantially longer life cycle, in addition to the higher operating temperature for enhanced energy conversion efficiency. The UCSD research team is aiming for many years of usage life, a feat they believe they are close to achieving.

The DOE’s SunShot program is modeled after President Kennedy’s moon landing program that inspired widespread interest in science and space exploration. Energy Secretary at the time Steven P. Chu launched the Sunshot Initiative in 2010 with the goal of making solar power cost competitive with other means of producing electricity by 2020.

For all the waste, weirdness and bizarre ideas the Fed’s fund, some gets through with remarkable results. Funding programs done right can payoff to economy in a powerful way. Lets hope the UCSD team’s material works out in the field trials. Concentrated solar has a useful place in power generation and the better and cheaper CSP gets the better for everyone.


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