As solar cells produce a greater proportion of total electric power, a fundamental limitation remains: the dark of night when solar cells go to sleep. Lithium-ion batteries, the commonplace batteries used in everything from hybrid vehicles to laptop computers, are too expensive a solution to use on something as massive as the electric grid.
Song Jin, a professor of chemistry at the University of Wisconsin-Madison, has a better idea: integrating the solar cell with a large-capacity battery. He and his colleagues have made a single device that eliminates the usual intermediate step of making electricity and, instead, transfers the energy directly to the battery’s electrolyte.
Jin chose a “redox flow battery,” or RFB, which stores energy in a tank of liquid electrolyte.
In a report now online in Angewandte Chemie International Edition, Jin, graduate student Wenjie Li, and colleagues at the King Abdullah University of Science and Technology in Saudi Arabia have demonstrated a single device that converts light energy into chemical energy by directly charging the liquid electrolyte.
Discharging the battery to power the electric grid at night could hardly be simpler, Jin says. “We just connect a load to a different set of electrodes, pass the charged electrolyte through the device, and the electricity flows out.”
Solar charging and electrical discharging, he notes, can be repeated for many cycles with little efficiency loss.
Unlike lithium-ion batteries, which store energy in solid electrodes, the RFB stores chemical energy in liquid electrolyte. “The RFB is relatively cheap and you can build a device with as much storage as you need, which is why it is the most promising approach for grid-level electricity storage,” says Jin, who also works on several other aspects of solar energy conversion.
In the new device, standard silicon solar cells are mounted on the reaction chamber and energy converted by the cell immediately charges the water-based electrolyte, which is pumped out to a storage tank.
Redox flow batteries already on the market have been attached to solar cells, “but now we have one device that harvests sunlight to liberate electrical charges and directly changes the oxidation-reduction state of the electrolyte on the surface of the cells,” says Li, the first author of the new study. “We are using a single device to convert solar energy and charge a battery. It’s essentially a solar battery, and we can size the RFB storage tank to store all the energy generated by the solar cells.”
The unified design suggests multiple advantages, Jin says. “The solar cells directly charge the electrolyte, and so we’re doing two things at once, which makes for simplicity, cost reduction and potentially higher efficiency.”
Having proven the concept of an integrated, solar-charged battery, Jin and Li are already working on improvements. One would be to match the solar cell’s voltage to the chemistry of the electrolyte, minimizing losses as energy is converted and stored.
The aqueous electrolyte used in the current study contains organic molecules but no expensive rare metals, which raise costs in many batteries. Jin and Li are also searching for electrolytes with larger voltage differential, which currently limits energy storage capacity.
A system that both creates and stores electricity will be judged by cost, efficiency and energy storage density, Jin says. “It’s not just about the efficiency of converting sunlight into electricity, but also about how much energy you can efficiently store in the device.”
As solar energy use grows, the storage problem becomes more acute. “People say the solar electricity capacity cannot exceed about 20 percent of overall grid capacity, because of supply shortages at night or during cloudy weather,” Jin says. “In some places, further solar installations may have to wait until better storage is available.”
By: Cynthia Shahan
I met Bill Johnson, founder of Brilliant Harvest, at the EcoFriendlyFloridaFest and then spoke with him again at National Drive Electric Day a few weeks ago. He is knowledgeable, easygoing, and up to date on all things solar. He offers pleasant passion for renewable energy as a provider who knows his work both technically and creatively.
As the CEO of Brilliant Harvest and as an EV enthusiast, Bill was keen to become a Tesla contractor. “Getting certified as a Tesla installer is a testament to the quality of our work,” Bill told me.
Brilliant Harvest in not a cookie-cutter solar company. Bill and his team work with clients to deliver solutions that fit the needs of each individual’s solar designs. A lovely array of solar accomplishments mounted on the wall of the Brilliant Harvest office feature dynamic photographs. Bill pointed out a project with the solar panels integrated into the structure, thus providing shade as well as generating electricity. The solar panels create walkways among sunspots mixed with shade. The thoughtful aesthetics combine the best of nature, art, and technology.
“This project won [Honor Award for Sustainable Design from the American Institute of Architects/Florida-Caribbean]. This is a great example of addressing what the individuals may want. They wanted something that was going to provide shade for the backyard and have some filtered sunlight, that moves throughout the day. We were able to do this lumosolar array — it really worked out perfectly and delivered a solution that exceeded their expectations. It certainly enhances the look and feel of the building itself.”
I drove by to experience the passerby’s view of the house.
The old McClellan Park neighborhood is picturesque on its own. The house swept up the AIA award for a variety of reasons, rising above others for technological and artistic reasons among the entire Florida–Caribbean region. I delighted in the patterns of sun and shade due to the solar panels blending with the leaves and branches of the trees. The panels transmit a filtered sunlight down through the panel.
Another photograph in the office is a display from South St. Petersburg over a large air-conditioned structure. It is a >100,000-watt system, with the panels on the wing of a self-storage facility producing more energy than it consumes. Sending energy back to the main building offsets energy consumption of the main building and cuts energy bills drastically.
As noted in the title, Brilliant Harvest recently landed a deal with Tesla to become one of its certified residential and commercial Powerwall installers. “The Powerwall is a Tesla home battery system that turns your home’s solar panels into an all day resource — increasing self consumption of solar — while offering back-up in the event of outage.” Typically, if solar panels produce more power than a home needs, the excess goes back to the grid. The Powerwall instead enables a homeowner to capture and store excess solar power produced during the day for use at night.
Bill notes that problems with solar policies (in Florida) are improving, but are far from over. As I recently wrote, 73% of Florida voters voted “Yes” in August for pro-solar legislation. However,Amendment 1 needs a “No” vote in November.
In a discovery that could have profound implications for future energy policy, Columbia scientists have demonstrated it is possible to manufacture solar cells that are far more efficient than existing silicon energy cells by using a new kind of material, a development that could help reduce fossil fuel consumption.
The team, led by Xiaoyang Zhu, a professor of Chemistry at Columbia University, focused its efforts on a new class of solar cell ingredients known as Hybrid Organic Inorganic Perovskites (HOIPs). Their results, reported in the prestigious journal Science, also explain why these new materials are so much more efficient than traditional solar cells—solving a mystery that will likely prompt scientists and engineers to begin inventing new solar materials with similar properties in the years ahead.
“The need for renewable energy has motivated extensive research into solar cell technologies that are economically competitive with burning fossil fuel,” Zhu says. “Among the materials being explored for next generation solar cells, HOIPs have emerged a superstar. Until now no one has been able to explain why they work so well, and how much better we might make them. We now know it’s possible to make HOIP-based solar cells even more efficient than anyone thought possible.”
Solar cells are what turn sunlight into electricity. Also known as photovoltaic cells, these semiconductors are most frequently made from thin layers of silicon that transmit energy across its structure, turning it into DC current.
Silicon panels, which currently dominate the market for solar panels, must have a purity of 99.999 percent and are notoriously fragile and expensive to manufacture. Even a microscopic defect—such as misplaced, missing or extra ions—in this crystalline structure can exert a powerful pull on the charges the cells generate when they absorb sunlight, dissipating those charges before they can be transformed into electrical current.
In 2009, Japanese scientists demonstrated it was possible to build solar cells out of HOIPs Continue Reading »
By: Sam Pothercary
Tesla’s utility and business energy storage solution, the Powerpack, is being installed by U.K. developer Camborne Energy Storage alongside a PV plant in Somerset, making it the first large-scale Tesla storage unit to be installed in Europe.
As energy storage solutions become more in vogue in is little surprise to see big global brands such as Tesla muscling in on the industry. This landmark event is just the latest move that Tesla has made in various energy storage markets around the world, as the company looks to become one of the top global providers of residential- and utility-scale storage solutions.
The Tesla Powerpack is the company’s large-scale storage offering that is specifically designed to work with solar PV sites, whether they be utility-scale or commercial in size, as it can be scaled to space, power and energy requirements.
U.K.-based developer Camborne Energy Storage is working with EPC Poweri services for the installation, that is being completed at a ground-mounted solar PV site in Somerset. Camborne hopes that this solution will prove successful, as it looks to deploy battery storage across the U.K.
“The development of Tesla’s first European grid-tied system is an exciting step forward for Camborne and Tesla in terms of our respective storage strategies,” commented Managing Director of Camborne Dan Taylor. “The project is another success for storage development in the U.K. and being co-located with a renewable generation site, should offer significant benefits to all stakeholders.”
Incorporating such energy storage units is moving the energy system in the right direction, as it will help it improve efficiency and allow it to more easily incorporate renewable energy sources. Tesla has already set its stall out as a major player in the energy storage market, and installed its first residential offering to a home PV array earlier in the year.
The first Tesla Powerwall was installed in the UK in March at a home in Essex. It was a 7.2 kW Tesla Powerwall that was connected to a 4.5 kW rooftop PV array.
Courtesy: : http://www.pv-magazine.com/news/
Fabrics that can generate electricity from physical movement have been in the works for a few years. Now researchers at Georgia Institute of Technology have taken the next step, developing a fabric that can simultaneously harvest energy from both sunshine and motion.
Combining two types of electricity generation into one textile paves the way for developing garments that could provide their own source of energy to power devices such as smart phones or global positioning systems.
“This hybrid power textile presents a novel solution to charging devices in the field from something as simple as the wind blowing on a sunny day,” said Zhong Lin Wang, a Regents professor in the Georgia Tech School of Materials Science and Engineering. The research was reported in the Nature Energy.
To make the fabric, Wang’s team used a commercial textile machine to weave together solar cells constructed from lightweight polymer fibers with fiber-based triboelectric nanogenerators.
Triboelectric nanogenerators use a combination of the triboelectric effect and electrostatic induction to generate small amount of electrical power from mechanical motion such as rotation, sliding or vibration.
Wang envisions that the new fabric, which is 320 micrometers thick woven together with strands of wool, could be integrated into tents, curtains or wearable garments.
“The fabric is highly flexible, breathable, light weight and adaptable to a range of uses,” Wang said.
Fiber-based triboelectric nanogenerators capture the energy created when certain materials become electrically charged after they come into moving contact with a different material. For the sunlight-harvesting part of the fabric, Wang’s team used photoanodes made in a wire-shaped fashion that could be woven together with other fibers.
“The backbone of the textile is made of commonly-used polymer materials that are inexpensive to make and environmentally friendly,” Wang said. “The electrodes are also made through a low cost process, which makes it possible to use large-scale manufacturing.”
In one of their experiments, Wang’s team used a fabric only about the size of a sheet of office paper and attached it to rod like a small colorful flag. Rolling down the windows in a car and letting the flag blow in the wind, the researchers were able to generate significant power from a moving car on a cloudy day. The researchers also measured the output by a 4 by 5 centimeter piece, which charged up a 2 mF commercial capacitor to 2 volts in one minute under sunlight and movement.
“That indicates it has a decent capability of working even in a harsh environment,” Wang said.
While early tests indicate the fabric can withstand repeated and rigorous use, researches will be looking into its long-term durability. Next steps also include further optimizing the fabric for industrial uses, including developing proper encapsulation to protect the electrical components from rain and moisture.