Power/Performance Bits: June 8

High temp capacitor; solar windows.


High temp capacitor
Researchers at Pennsylvania State University doped a dielectric capacitor to increase storage capacity while also increasing electric charge efficiency, enabling the capacitor to withstand greater voltage with very little energy loss at temperatures higher than 300 degrees Fahrenheit.

“What we have done is to use interface effects in nano-dopants to increase both the storage efficiency and electric breakdown strength with a very small quantity of dopants and at a low cost,” said Qiming Zhang, distinguished professor of electrical engineering at Penn State. “A lot of people think they need to fill the capacitor with a lot of fillers to achieve the greater energy storage efficiency, but we showed you can accomplish it in the opposite direction, that is, by using very low-volume content fillers with very low-cost materials, which can also lead to greater breakdown strength. This keeps the cost low and makes this highly scalable.”

“Hybrid electric vehicles now use a capacitor made of a material known as BOPP,” Zhang said. “They work well up to 80 degrees Celsius (176 F). However, vehicles can get very hot, so you have to use a cooling agent. It increases cost and also adds volume. Now, you can use this new capacitor with metamaterials, which are smaller, to replace the existing capacitor and not worry about the cooling loop since it can handle higher temperatures.”

Equipment used for deep drilling also will potentially benefit from having an increased temperature threshold and a smaller, less expensive capacitor. The electric grid will potentially benefit from this new technological development, particularly in terms of the increased energy efficiency and higher electric breakdown strength.

“We did not create a new material, but by using metamaterials in this way, we can greatly enhance the performance of existing materials without adding cost,” Zhang said.

Solar windows
Researchers from the Australian Research Council Centre of Excellence in Exicton Science at Monash University and CSIRO Manufacturing developed perovskite solar cells that generate electricity while allowing light to pass through. They are now investigating how the new technology could be built into commercial window products with Viridian Glass, Australia’s largest glass manufacturer.

The researchers say the technology will transform windows into active power generators. Two square meters of solar window, the researchers say, will generate about as much electricity as a standard rooftop solar panel.

They used an organic semiconductor that can be made into a polymer and used it to replace a commonly used solar cell component (known as Spiro-OMeTAD), which shows very low stability because it develops an unhelpful watery coating. The substitute showed promising results.

“Rooftop solar has a conversion efficiency of between 15 and 20%,” said Jacek Jasieniak, from the ARC Centre of Excellence in Exciton Science. “The semi-transparent cells have a conversion efficiency of 17%, while still transmitting more than 10% of the incoming light, so they are right in the zone. It’s long been a dream to have windows that generate electricity, and now that looks possible.”

CSIRO research scientist Anthony Chesman said the team is now working on scaling up the manufacturing process. “We’ll be looking to develop a large-scale glass manufacturing process that can be easily transferred to industry so manufacturers can readily uptake the technology.”

“There is a trade-off,” said Jasieniak. “The solar cells can be made more, or less, transparent. The more transparent they are, the less electricity they generate, so that becomes something for architects to consider.”

He added that solar windows tinted to the same degree as current glazed commercial windows would generate about 140 watts of electricity per square meter.

“These solar cells mean a big change to the way we think about buildings and the way they function. Up until now every building has been designed on the assumption that windows are fundamentally passive. Now they will actively produce electricity.

“Planners and designers might have to even reconsider how they position buildings on sites, to optimize how the walls catch the sun.”

The team’s next project is a tendem device, said Jae Choul Yu, also from Exciton Science and Monash. “We will use perovskite solar cells as the bottom layer and organic solar cells as the top one.” The team hopes for commercialization within ten years.

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