New Generation of High-Efficiency Solar Thermal Absorbers Developed

Researchers from the Universities of Bristol and Exeter are one step closer to developing a new generation of low-cost, high-efficiency solar cells. The structure is one of the world’s first examples of a tri-layer metasurface absorber using a carbon interlayer.

The focused ion beam fabricated trilayer metasurface within the inset shows rounded features in the upper 2-D gold square periodic surface. Image courtesy University of Bristol.

The system, developed by Chenglong Wang a PhD student in Professor Martin Cryan’s research group, uses amorphous carbon as an inter-layer between thin gold films with the upper film patterned with a 2D periodic array using focused ion beam etching.

The trilayer gold-carbon-gold metasurface strongly absorbs light across the solar spectrum but minimises emission of thermal radiation from the structure. The use of gold in the research is a first step towards a high temperature metasurface where gold can be replaced by other refractory metals such as tungsten or chrome.

The cell will be used for solar thermal energy applications and has the potential to reach much higher temperatures than simple black surfaces because it can minimise the emission of thermal radiation.

The metasurface has been developed as part of a joint project, led by Dr Neil Fox, between Bristol’s Department of Electrical and Electronic Engineering and Schools of Physics and Chemistry. The aim of this project is to develop diamond-based solar thermionic devices, which use sunlight to get surfaces sufficiently hot that they emit electrons directly into a vacuum.

If these electrons are collected at a cooled anode, electrical energy can be produced with maximum efficiencies predicted to be much higher than is achievable using conventional silicon solar cells.

Martin Cryan, Professor of Applied Electromagnetics and Photonics in the Department of Electrical and Electronic Engineering, said: “Integrating diamond within metasurfaces is very challenging, and this paper is a first step in that direction using amorphous carbon.

“The next stage is to carry out high temperature testing on the structures and to attempt to reach the ~700 degrees celsius required to obtain efficient thermionic emission.”

The Bristol team have been working with Professor Tapas Mallick from the University of Exeter to develop the low-cost solar concentrator systems.


Apple has Some Solar Power it Wants to Sell You

By: David Carnoy

Courtesy: designboom

Making a big jump into renewable power, Apple last year invested $850 million in a California solar farm. That facility was supposed to provide enough renewable energy for Apple’s new campus in Silicon Valley, all of its other offices in California, all of its retail stores in the state and a data center, CEO Tim Cook said.

Apple now has plans, according to and Bloomberg, to sell excess energy from the solar panels it’s installing on the roof of that new campus, Apple Campus 2, which the company will move into next year.

The news comes thanks to a filing by subsidiary Apple Energy, which applied to the US Federal Energy Regulatory Commission to sell power from the Campus 2’s solar panels and hydrogen fuel cells, plus other renewable energy facilities in Oregon, North Carolina, California, Nevada and Arizona.

Bloomberg notes that if Apple’s application is approved, starting August 5 it will be able to sell energy directly to customers instead of through an energy utility. Google secured similar rights in 2010, the news agency said.


Bionic Leaf Turns Sunlight into Liquid Fuel

New system surpasses efficiency of photosynthesis

A new “bionic leaf” system uses solar energy to produce liquid fuel. Credit: Courtesy of Jessica Polka/Silver Lab

By: Peter Reuell

The days of drilling into the ground in the search for fuel may be numbered, because if Daniel Nocera has his way, it’ll just be a matter of looking for sunny skies.

Nocera, the Patterson Rockwood Professor of Energy at Harvard University, and Pamela Silver, the Elliott T. and Onie H. Adams Professor of Biochemistry and Systems Biology at Harvard Medical School, have co-created a system that uses solar energy to split water molecules and hydrogen-eating bacteria to produce liquid fuels.

The paper, whose lead authors include post-doctoral fellow Chong Liu and graduate student Brendan Colón, is described in a June 3 paper published in Science.

“This is a true artificial photosynthesis system,” Nocera said. “Before, people were using artificial photosynthesis for water-splitting, but this is a true A-to-Z system, and we’ve gone well over the efficiency of photosynthesis in nature.”

While the study shows the system can be used to generate usable fuels, its potential doesn’t end there, said Silver, who is also a Founding Core Member of the Wyss Institute at Harvard University.

“The beauty of biology is it’s the world’s greatest chemist — biology can do chemistry we can’t do easily,” she said. “In principle, we have a platform that can make any downstream carbon-based molecule. So this has the potential to be incredibly versatile.”

Dubbed “bionic leaf 2.0,” the new system builds on previous work by Nocera, Silver and others, which — though it was capable of using solar energy to make isopropanol — faced a number of challenges.

Chief among those challenges, Nocera said, was the fact that the catalyst used to produce hydrogen — a nickel-molybdenum-zinc alloy — also created reactive oxygen species, molecules that attacked and destroyed the bacteria’s DNA. To avoid that problem, researchers were forced to run the system at abnormally high voltages, resulting in reduced efficiency.

“For this paper, we designed a new cobalt-phosphorus alloy catalyst, which we showed does not make reactive oxygen species,” Nocera said. “That allowed us to lower the voltage, and that led to a dramatic increase in efficiency.”

The system can now convert solar energy to biomass with 10 percent efficiency, Nocera said, far above the one percent seen in the fastest growing plants.

In addition to increasing the efficiency, Nocera and colleagues were able to expand the portfolio of the system to include isobutanol and isopentanol. Researchers also used the system to create PHB, a bio-plastic precursor, a process first demonstrated by MIT professor Anthony Sinskey.

The new catalyst also came with another advantage — its chemical design allows it to “self-heal” — meaning it wouldn’t leech material into solution.

“This is the genius of Dan,” Silver said. “These catalysts are totally biologically compatible.”

Though there may yet be room for additional increases in efficiency, Nocera said the system is already effective enough to consider possible commercial applications but within a different model for technology translation.

“It’s an important discovery–it says we can do better than photosynthesis,” Nocera said. “But I also want to bring this technology to the developing world as well.”

Working in conjunction with the First 100 Watts program at Harvard, which helped fund the research, Nocera hopes to continue developing the technology and its applications in nations like India with the help of their scientists.

In many ways, Nocera said, the new system marks the fulfillment of the promise of his “artificial leaf” — which used solar power to split water and make hydrogen fuel.

“If you think about it, photosynthesis is amazing,” he said. “It takes sunlight, water and air–and then look at a tree. That’s exactly what we did, but we do it significantly better, because we turn all that energy into a fuel.”


Green skies: Solar Impulse 2 pilot Eyes Renewable Energy Future

By: James Rogers

Piloted by Andre Borschberg, Solar Impulse 2 flies over New York (Solar Impulse).

Solar Impulse 2, which flew over the Statue of Liberty on its historic solar-powered global journey Saturday, continues to prove the vast potential of renewable energy, according to pilot Bertrand Piccard.

The plane landed at New York’s JFK airport at 4 a.m. ET on Saturday, completing the 14th leg of its trip.

“In the 21st century, liberty is to be free from fossil energy and pollution,” said Solar Impulse chairman and pilot Piccard, during a press conference at JFK. “We can have clean technology that creates jobs, sustains growth – it’s a new market for the world.”

The record-breaking plane has travelled 18,540 miles without a single drop of fuel since setting off on the first leg of the trip from Abu Dhabi to Oman in March 2015.

A larger version of a single-seat prototype that first flew six years ago, Solar Impulse 2 is made of carbon fiber and has 17,248 solar cells built into the wing that supply the plane with renewable energy, via four motors. The solar cells recharge four lithium polymer batteries, which provide power for night flying.

To accommodate the solar cells the plane has a 236-foot wingspan, similar to that of a Boeing 747. The aircraft weighs just 2.3 tons, similar to a family car.

However, Solar Impulse 2’s comparatively low speed (it typically flies at 30 to 40 mph) could prevent the adoption of solar-powered technology for commercial passenger aircraft.

Nonetheless, the pioneering aircraft could drive innovation in a number of areas. Andre Borschberg, who is taking it in turns with Piccard to fly the single-seat aircraft around the world, described Solar Impulse 2 as “a flying smart grid,” during the press conference.

Power and automation specialist ABB is one of the companies partnering with Solar Impulse, providing engineering expertise during the global trek. “What they are doing in the air could definitely be done on the ground,” Conor Lennon, ABB’s global head of special projects, told, adding that the plane could help develop more efficient battery technology.

Other partners include polymer specialist Covestro, which developed a new form of microcell insulation foam for Solar Impulse 2, and chemical firm Solvay, which is providing a number of products, from specialty polymers to lubricants.

Piloted by Borschberg, the solar-powered plane took off from Lehigh Valley, Pennsylvania after 11 p.m. ET Friday and flew over the Statue of Liberty during a 4 hour-41 minute flight to JFK.

“All morning, when I was over the Hudson River I felt like a 3-year old kid looking at a Christmas tree, it was so beautiful,” said Borschberg, during the press conference.

Borschberg broke a number of records on the eighth leg of Solar Impulse’s 2 journey, landing in Hawaii on July 3 2015 after an incredible 4,480-mile, 118-hour flight from Japan. The journey shattered the record for longest solar-powered flight in terms of distance and duration. Borschberg also bro ke the record for longest non-stop solo flight without refueling, which previously stood at 76 hours and 45 minutes.

The next leg of the journey takes Solar Impulse 2 on a risky non-stop flight across the Atlantic. Piloted by Piccard, the trans-Atlantic flight has not yet been scheduled.

Prior to its arrival in Lehigh Valley, Solar Impulse 2 made stops in India, Myanmar, China, Japan, Hawaii, California, Phoenix, Tulsa and Dayton. After flying across the Atlantic, the final leg of the odyssey is from Europe to Abu Dhabi.


Turning Human Waste into next Generation Biofuel

The waterless energy-producing toilet system, located inside the Science Walden Pavilion at UNIST. Credit: Ulsan National Institute of Science and Technology (UNIST)

Researchers affiliated with Ulsan National Institute of Science and Technology (UNIST), South Korea, have found a new way to convert human waste into renewable energy sources.

A brand new outdoor laboratory has been recently launched at UNIST and this is expected to convert human waste into renewable energy sources, and possible to a monetary value.

Nestled in the center of UNIST campus, this hexagonal-shaped laboratory, called Science Walden Pavillion is now open to the public.

The pavillion, designed by Artist Seung-hyun Ko, Co-Founder of the Korean Nature Art Association (YATOO), consists of two floors with a total area of 122.25 square meter, featuring walls of translucent polycarbonate to allow visual connection between the inside and outside of the pavillion.

Prof. Jaeweon Cho (School of Urban and Environmental Engineering, UNIST), Director of Science Walden Pavillion who is heading the project, states “Science Walden Pavillion not only stands for a playground for both scientists and artist, but also the medium that connects arts and science.” He adds, “The pavillion is a unique blending of creative studio and research lab, bringing arts and science together.”

The major research facilities of this pavillion include “Waterless Energy-producing Toilet System” and “Microbial Energy Production System”.

Science Walden Pavillion, a unique blending of creative studio and research lab is now open to the public at UNIST. Credit: UNIST

The waterless toilet system, located on the first floor of the pavillion treats human excrement without using water. The system utilizes a natural biological process to break down human waste into a dehydrated odorless compost-like material. Then, at the microbial energy production system, this compost-like material is converted into biodiesel or heat energy.

Once the grinding system inside the toilet converts feces into a dry, odorless material, it will be transferred to a digestion tank, containing thousands of different microbes. The microbes inside the tank will, then, biodegrade the powdered human manure to generate carbon dioxide and methane. Using high pressure and membrane, carbon dioxide is extracted to culture green algae for biofuel while methane is stored for later use as a heating fuel.

The project aims to reduce urbanization’s negative footprint on ecosystems by safely converting human waste into viable renewable energy and possibly to a monetary values.

Prof. Cho states, “Our ultimate goal is not only for the new toilet system to save water and operational costs for wastewater treatment plants, but for us to establish an ecosystem that supports technology innovation and drives economic diversification where human waste literally has a financial value.”

To reduce the objection of using the facility, Prof. Cho and his project team added a unique artistic touch to this collaborative outdoor laboratory. They have designed a futuristic toilet with groundbreaking innovations in sanitation technology that is comfortable at the same time. A roof garden, which filters rainwater and provides insulation is another added value to this pavillion.

Director Jaeweon Cho of Science Walden Pavillion, examining the Green Algae Tree Structure.

Besides, Prof. Cho has developed a smartphone application that can determine the monetary value of the treated human excrement. Using this application, people can soon trade their waste for a virtual or digital currency to use. At the pavillion, the team plans to expand into selling salads made with barley sprouts, which can be only purchased with such virtual currency.

“This is a very exciting project for us,” says Prof. Cho. “We expect that this will become a pivotal stepping stone in the developing future of many countries facing dangerous sanitation issues and a lack of reliable, affordable energy”.

If this experiment succeeds, the team plans to expand its use of the waterless toilet system and microbial energy production system in real life. This project has been carried out in collaboration with YATOO, Art Center Nabi, Paju Typography Institute (PaTI), and Hankuk Engineering Consultants (H.E.C.) in South Korea.