10 technologies shaping the future of solar power

From bio-solar cells and floating solar farms to energy harvesting trees and transmission of power from space, the future looks quite bright for renewable energy

Floating solar platforms can be used in areas where land is at a premium.
Floating solar platforms can be used in areas where land is at a premium.

1. Bio-solar cells

For the first time ever, researchers connected nine biological-solar (bio-solar) cells into a bio-solar panel and continuously produced electricity from the panel and generated the most wattage of any existing small-scale bio-solar cells.

Last year, the group took steps towards building a better bio-solar cell by changing the materials used in anodes and cathodes (positive and negative terminals) of the cell and also created a miniature microfluidic-based single-chambered device to house the bacteria instead of the conventional, dual-chambered bio-solar cells.

However, this time, the group connected nine identical bio-solar cells in a 3x3 pattern to make a scalable and stackable bio-solar panel. The panel continuously generated electricity from photosynthesis and respiratory activities of the bacteria in 12-hour day-night cycles over 60 total hours.

The current research is the latest step in using cyanobacteria—which can be found in almost every terrestrial and aquatic habitat on earth—as a source of clean and sustainable energy.

Even with the breakthrough, a typical “traditional” solar panel on the roof of a residential house, made up of 60 cells in a 6x10 configuration, generates roughly 200 watts of electrical power at a given moment. The cells from this study, in a similar configuration, would generate about 0.00003726 watts. So, it isn’t efficient just yet, but the findings open the door to future research of the bacteria itself.

“Once a functional bio-solar panel becomes available, it could become a permanent power source for supplying long-term power for small, wireless telemetry systems as well as wireless sensors used at remote sites where frequent battery replacement is impractical,” said Seokheun ‘Sean’ Choi, an assistant professor of electrical and computer engineering in Binghamton University’s Thomas J. Watson School of Engineering and Applied Science, and co-author of the paper, in a 11 April press statement.

The findings are currently available online and will be published in the June edition of the journal Sensors and Actuators B: Chemical.

2. A new way for converting solar energy into electricity

Researchers from The Hebrew University of Jerusalem in Israel, and the University of Bochum in Germany, reported a new paradigm for the development of photo-bioelectrochemical cells in Nature Energy this January, providing a means for the conversion of solar energy into electricity.

While photosynthesis is the process by which plants and other organisms make their own food using carbon dioxide, water and sunlight, bioelectrochemical systems take advantage of biological capacities (microbes, enzymes, plants) for the catalysis of electrochemical reactions.

In a 19 January press statement, the researchers pointed out that although significant progress has been achieved in the integration of native photosystems with electrodes for light-to-electrical energy conversion, uniting photosystems with enzymes to yield photo-bioelectrocatalytic solar cells remains a challenge.

Hence, the researchers constructed photo-bioelectrochemical cells using the native photosynthetic reaction and the enzymes glucose oxidase, or glucose dehydrogenase. The system comprises modified integrated electrodes that include the natural photosynthetic reaction centre, known as photosystem I, along with the enzymes. The native proteins are electrically wired by means of chemical electron transfer mediators. Photo-irradiation of the electrodes leads to the generation of electrical power, while oxidizing the glucose substrate acts as a fuel.

The system provides a model to harness the native photosynthetic apparatus for the conversion of solar light energy into electrical power, using biomass substrates as fuels. Itamar Willner, a professor at the Hebrew University’s Institute of Chemistry, said in a statement: “The study results provide a general approach to assemble photo-bioelectrochemical solar cells with wide implications for solar energy conversion, bioelectrocatalysis and sensing.”

3. Reshaping solar spectrum to turn light into electricity

Land and labour costs account for the bulk of the expense when installing solar panels since solar cells—made often of silicon or cadmium telluride—rarely account for more than 20% of the total cost. Hence, solar energy could be made cheaper if less land had to be purchased to accommodate the panels. This is best achieved if each solar cell generates more power, but it is not easy.

A team of chemists at the University of California says it has found a way to make this happen. In a paper that was published in Nano Letters, an American Chemical Society publication, the researchers said that by combining inorganic semiconductor nanocrystals with organic molecules, they succeeded in “upconverting” (two low-energy photons into one high-energy photon) photons in the visible and near-infrared regions of the solar spectrum.

The infrared region of the solar spectrum passes right through the photovoltaic materials that make up today’s solar cells, explained Christopher Bardeen, a professor of chemistry in a press release on 27 July 2015. This upconverted photon is readily absorbed by photovoltaic cells, generating electricity from light that normally would be wasted, according to Bardeen.

He added that these materials are essentially “reshaping the solar spectrum” so that it better matches the photovoltaic materials used today in solar cells. The ability to utilize the infrared portion of the solar spectrum could boost solar photovoltaic efficiencies by 30% or more.

Besides solar energy, the ability to upconvert two low-energy photons into one high-energy photon has potential applications in biological imaging, data storage and organic light-emitting diodes, says Bardeen.

4. WaterNest 100

Indian real estate developers can take a lesson or two from this project. EcoFloLife has developed the WaterNest 100 eco-friendly floating house, exclusively designed by renowned Italian architect Giancarlo Zema. It is an over 100 sq. m residential unit, 12 metres in diameter and 4 metres high, made entirely of recycled laminated timber and a recycled aluminium hull.

Balconies are conveniently located on the sides and thanks to the large windows, permit enjoyment of fascinating views over the water. Bathroom and kitchen skylights are located on the wooden roof, as well as 60 sq. m of amorphous photovoltaic panels capable of generating 4kWp, which are used for the internal needs of the floating house. The interior of WaterNest 100 floating house can include a living room, dining area, bedroom, kitchen and bathroom or have other configurations according to the different housing or working needs.

The floating house can be positioned along river courses, lakes, bays, atolls and sea areas with calm waters. The use of materials and sustainable production systems make this unit recyclable up to as much as 98%. It has a hull that is made entirely of aluminium—a light alloy, highly resistant to impact, corrosion and 100% recyclable. Its photovoltaic panels installed on the wooden roof differ from conventional ones due to the low-energy consumption required for their production. From an aesthetic point of view, they can be curved to fit almost any type of roofing.

5. Floating panels, floating solar farms

In many countries, there is a lack of space to install large-scale ground-mount solar systems. As authorities wish to avoid taking away large farmlands for ground-mount solar systems, companies are introducing ecological alternative solutions.

One such firm is French company Ciel & Terre International, which has been developing large-scale floating solar solutions since 2011. Its Hydrelio Floating PV system allows standard PV panels to be installed on large bodies of water such as drinking water reservoirs, quarry lakes, irrigation canals, remediation and tailing ponds, and hydroelectric dam reservoirs.

This simple and affordable alternative to ground-mounted systems is particularly suitable for water-intensive industries that cannot afford to waste either land or water.

This is how it works. The main float is constructed of high-density thermoplastic (HDPE) and is set at a 12-degree angle to support a standard 60-cell PV solar module. A secondary non-slip HDPE float is then used to link the main floats together and provide a platform for maintenance and added buoyancy.

According to Ciel and Terre, the system is easy to install and dismantle, can be adapted to any electrical configuration, is scalable from low- to high-power generation and requires no tools or heavy equipment. It is also eco-friendly, fully recyclable, has low environmental impact and is cost-effective.

To date, the system has been installed in the UK. The company has also set up projects for floating solar farms in countries such as India, France and Japan.

6. Transmitting solar power wirelessly from space

The Japanese Space Agency (JAXA)’s Space Solar Power Systems (SSPS) aims at transmitting energy from orbiting solar panels by 2030. On 12 March, Mitsubishi Heavy Industries Ltd (MHI) successfully conducted a ground demonstration test of “wireless power transmission”, a technology that will serve as the basis for the SSPS. In the test, 10kW of electricity was successfully transmitted via a microwave unit. Power reception was confirmed at a receiver located 500 metres away. LED lights on the receiver confirmed the transmission. This marks a new milestone in transmission distance and power load (enough to power a set of conventional kitchen appliances).

Potentially, a solar battery in orbit (36,000km above earth) could generate power that would then be transmitted to earth via microwave/laser, without relying on cables. JAXA anticipates that this new technology could become a mainstay energy source that will simultaneously solve both environmental and energy issues on earth.

The estimated lifecycle carbon dioxide emission for the operational SSPS indicates that it is almost the same as from nuclear power system and much less than fossil fuel power system, JAXA claims on its website. Countries such as India, China and Japan are investing heavily in these technologies right now.

7. Solar energy harvesting trees

Researchers at the VTT Technical Research Centre in Finland have used solar and 3D printing technologies to develop prototypes of what they have christened as “energy harvesting trees”. The tiny leaves generate and store solar energy and can be used to power small appliances and mobile devices. They flourish indoors and outdoors and can also harvest kinetic energy from wind and temperature changes in the surrounding environment.

The tree’s leaves are actually flexible organic solar cells, printed using well-established mass-production techniques. Each leaf has a separate power converter, creating a multi-converter system that makes it possible to collect energy from a variety of sources such as solar, wind and heat temperature.

The more solar panels there are in a tree, the more energy it can harvest. The tree trunk is made with 3D technology by exploiting wood-based biomaterials VTT has developed. They are mass producible and can be infinitely replicated.

8. Squeezing more out of the sun

The sun is undoubtedly the greatest sustainable energy source for earth, but the problem is the low efficiency: 80% of installed PV panels worldwide have a performance of 15% or lower; if the panels are not tracked with the sun, the average of annual tilt losses add up to minus 70%.

German architect Andre Broessel believes he has a solution.

He says his company Rawlemon can “squeeze more juice out of the sun”, even during the night hours and in low-light regions. He has created a spherical sun power generator prototype called the beta.ray. His technology will combine spherical geometry principles with a dual axis tracking system, allowing twice the yield of a conventional solar panel in a much smaller surface area.

The futuristic design is fully rotational and is suitable for inclined surfaces, walls of buildings, and anywhere with access to the sky. It can even be used as an electric car charging station.

By using a high-efficiency multi-junction cell, Broessel’s company claims to have reduced the cell surface down to 1% compared to the same power output as a conventional silicon cell in optimal conditions.

“In combination with dual axis tracking, our system generates twice the yield of a conventional panel. In addition, our smaller cell area has a lower carbon footprint because its production requires fewer precious semiconductor or other building materials,” he says on the company website.

Rawlemon has also introduced a USB spherical sun charger called beta.ey.

9. Ways to boost solar power

A group of scientists at the University of Toronto have unveiled a new type of light-sensitive nanoparticles called colloidal quantum dots, which many believe will offer a less expensive and more flexible material for solar cells. Specifically, the new materials use n-type and p-type semiconductors, but ones that can actually function outdoors. This is possible because the new colloidal quantum dots don’t bind to air (unlike traditional n-type materials that bind to oxygen)—a quality that also helps increase radiant light absorption besides offering stability outdoors. The researchers claim that panels using this new technology were found to be up to 8% more efficient at converting sunlight.

Researchers at Imperial College University in London believe they have discovered a new material—gallium arsenide—that could make solar PV systems nearly three times more efficient than existing products on the market.

The solar cells are called “triple junction cells” and they are much more efficient because they can be chemically altered in a manner that optimizes sunlight capture. The model uses a sensor-driven window blind that can track sun light along with “light-pipes” that guide the light into the system.

A company called Novatec Solar recently commissioned an energy storage solution for solar PV systems using a molten salt storage technology. The process uses inorganic salts to transfer energy generated by solar PV systems into solar thermal using heat transfer fluid rather than oils as some storage systems have. The result is that solar plants can operate at temperatures over 500 degree Celsius, which would result in a much higher power output. This means that costs to store solar power would be lowered significantly and utility companies could finally use solar power plants as base load plants rather than to meet peak demand during prime daylight hours.

In a project funded by the US department of energy, Ohio State University researchers recently announced they created a battery that is 20% more efficient and 25% cheaper than anything on the market today. The secret to the design is that the rechargeable battery is built into the solar panel itself, rather than operating as two stand-alone systems. By conjoining the two into one system, scientists said they could lower costs by 25% compared to existing products.

Scientists are exploring ways to actually line up highways and roads with solar panels, which would then be used to deploy large amounts of electricity to the grid. Called solar roadways, they have already popped up in countries such as the Netherlands and promise to save on land space.

10. Concentrated PV cells

IBM researchers have found a way to make concentrated PV cells that are more efficient in converting the sun’s energy into electricity. The researchers have shown that it is possible to increase the concentration of light on photovoltaic cells by about 10 times without causing them to melt. This, they say, makes it possible to boost the amount of usable electrical energy produced by up to five times.

The principle behind concentrated PV cells is to use a large lens to focus light onto a relatively small piece of PV semiconductor material. The benefit is that only a fraction of the semiconductor material is used, thereby reducing costs. IBM’s solution is to place an ultrathin layer of liquid metal, a compound of gallium and indium, between the two surfaces. The metal has a very high thermal conductivity and because it’s a liquid, it is possible to make this layer extremely thin, typically around 10 micrometers.

IBM is in talks with solar-cell companies about licensing the technology. Last September, Swiss-based Airlight Energy said it has partnered with IBM to bring affordable solar technology to the market by 2017.

The system can concentrate the sun’s radiation 2,000 times and convert 80% of it into useful energy to generate 12kW of electrical power and 20kW of heat on a sunny day—enough to power several average homes.

5 things you may not know about solar

1. Solar energy is the most abundant energy resource on earth--173,000 terawatts of solar energy strikes the Earth continuously. That’s more than 10,000 times the world’s total energy use.(http://1.usa.gov/SiELu2)

2. The first silicon solar cell was built by Bell Laboratories in 1954.

3. The space industry was an early adopter of solar technology, and began to use it in the 1960s to provide power aboard spacecraft. The Vanguard 1--the first artificial earth satellite powered by solar cells--remains the oldest manmade satellite in orbit, logging more than 6 billion miles.

4. As prices continue to fall, solar energy is increasingly becoming an economical energy choice for homeowners and businesses. Still, the biggest hurdle to affordable solar energy remains the soft costs like permitting, zoning, and hooking a solar system up to the power grid.

5. In California’s Mojave Desert, the largest solar energy project in the world is currently under construction. The project relies on a technology known as solar thermal energy. Once the project is complete, 350,000 mirrors will reflect light onto boilers. When the water boils, the steam turns a turbine, creating electricity. The project is expected to provide clean, renewable energy for 140,000 homes and is supported by an Energy Department loan guarantee.

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