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New Technology Aims to Makes Photovoltaic Cells 70% More Effective.
Technion researchers have developed a technology that could improve the efficiency of photovoltaic cells by nearly 70 percent. The study was conducted at the Excitonics Lab, headed by Assistant Professor Carmel Rotschild at the Faculty of Mechanical Engineering, with the assistance of the Grand Technion Energy Program (GTEP) and the Russell Berrie Nanotechnology Institute (RBNI) at the Technion, and as part of the lab’s ERC project on new thermodynamic tools for solar cells.
The sun is a powerful source of renewable energy. In fact, it is currently the only energy source capable of supplying the energy consumption of the human race, so it’s no wonder that the use of solar energy is increasing. But there are currently a number of technological limitations when it comes to photovoltaic cell efficiency.
Photovoltaic cells optimally utilize a very narrow range of the solar spectrum – the broad light supplied by the sun; radiation not within this narrow range merely warms these cells and is not utilized. This energy loss limits the maximum efficiency of current solar cells to around 30%.
The Technion team’s method is based on an intermediate process that occurs between sunlight and the photovoltaic cell. The photoluminescence material they created absorbs the radiation from the sun, and converts the heat and light from the sun into an “ideal” radiation, which illuminates the photovoltaic cell, enabling higher conversion efficiency. As a result, the device’s efficiency is increased from 30% (the conventional value for photovoltaic devices), to 50%.
The inspiration for the breakthrough comes from optical refrigeration, where the absorbed light is re-emitted at higher energy, thereby cooling the emitter. The researchers developed a technology that works similarly, but with sunlight.
“Solar radiation, on its way to the photovoltaic cells, hits a dedicated material that we developed for this purpose, the material is heated by the unused part of the spectrum,” says graduate student Assaf Manor, who led the study as part of his PhD work. “In addition, the solar radiation in the optimal spectrum is absorbed and re-emitted at a blue-shifted spectrum. This radiation is then harvested by the solar cell. This way both the heat and the light are converted to electricity.”
The group hopes to demonstrate a full operating device with record efficiency within 5 years’ time. If they are successful, they feel could become a disruptive technology in solar energy
Sunflower solar panel
Q.CELLS – Q.ANTUM TECHNOLOGY
Q.ANTUM technology supercharges ordinary crystalline solar cells and modules. Unlike expensive high-end solar modules, Q.ANTUM does not involve a complex new cell design. No special system components are required. Q.ANTUM delivers exceptional performance under real-world conditions. No PV system sees direct sunlight every minute of every day. Therefore, this is designed to generate more power when the sun is rising, setting, or even behind clouds. You’ll also see higher yields in the middle of hot and sunny summers, and during clear fall and winter days, when the sun is not as high in the sky. We enhanced low-light performance, but also the output of our modules across a range of temperatures – all to bring you higher profits.
Depending on which source is consulted, PERC stands for Passivated Emitter Rear Cell, Passivated Emitter Rear Contact or even Passivated Emitter and Rear Cell. First developed in Australia in the 1980s by scientist Martin Green and his team at University of New South Wales, PERC technology adds an extra layer to the rear-side of a solar cell. Manufacturers spent many years focusing on the front side of a solar cell, and less attention was paid to taking advantage of production opportunities from the backside. Incorporating PERC into a solar cell boosts generation.
In order to create a PERC cell, an additional two steps are employed to the standard back surface field (BSF) during the manufacturing process. First, a rear surface passivation film is applied. Second, lasers or chemicals are used to open the rear passivation stack and create tiny pockets in the film to absorb more light. Manufacturers can approach this in different ways (i.e. varying the recipe for the film and opening technique), but in every instance a dielectric passivation layer is added to the back of the cell.
In employing just two additional steps, the return is threefold: 1.) Electron recombination is significantly reduced; 2.) More light is absorbed; and 3.) Higher internal reflectivity is experienced. Not all sunlight is absorbed through non-PERC solar cells (some light passes straight through). But with a passivation layer on the rear side of a PERC cell, unabsorbed light is reflected by the additional layer back to the solar cell for a second absorption attempt. This process leads to a more efficient solar cell. This is great news for those across the spectrum of the industry.
DUAL GLASS PANELS
Many manufacturers are now producing what is known as glass-glass, dual glass or double glass solar panels which should not be confused with bifacial technology. The rear glass back sheetreplaces the traditional EVA (plastic) back sheet and creates a glass-glass sandwich which is considered superior as the glass does not deteriorate over time or suffer from light induced degradation (LID). Due to the longer life of glass-glass panels some manufacturers such as Trina solar are also offering 30-year performance warranties.
Without the strength of the standard aluminium frames double glass panels are more durable and stiffer than a single glass panel and most double glass panels are frameless which offers other advantages especially in regards to cleaning. With no frame to catch dirt and dust the frameless modules when tilted or flat are much easier to clean and are more inclined to aid from wind and rain to self-clean which results in greater solar output.
Manufacturers producing dual glass solar panels include Jinko solar, Longii Solar, Trina Solar, Yingli Solar and JA solar.
BIFACIAL SOLAR MODULES
Bifacial solar technology has been available for several years but is starting to become popular as the cost to manufacture the very high quality monocrystalline cells required continues to decrease. Bifacial cells absorb light from both sides of the panel and in the right conditions can produce up to 30% more energy than traditional monofacial panels. The bifacial solar panels use a front and rear glass system to encapsulate the cells which is more durable than the traditional plastic laminate back sheet used on regular panels. The glass rear side lasts longer with lower degradation over time and can significantly reduce the risk of failure, with some manufacturers now offering 30-year performance warranties on bifacial panel models.
Traditionally bi-facial solar panels were only used in ground mounted installations in unique locations where the sunlight is easily bounced or reflected off the surrounding surfaces, in particular snow-prone regions and extreme latitudes. Although they have been proven to work well when ground mounted over light sandy surfaces and are also able to achieve up to 10% higher output even on light coloured rooftops when tilted. Manufacturers producing bifacial solar panels include LG energy, Trina solar, Jinko Solar and Yingli Solar.
The busbars are the thin wires or ribbons which run down each cell and carry the electrons (current) through the solar module. As PV cells have become more efficient they generate more current and over the last 5 years most manufacturers have moved from 3 busbars up to 4 or 5 busbars. The compromise is that the busbars actually shade part of the cell and so can slightly reduce performance if they are too large, so they need to be very carefully designed. On the other hand, multiple busbars provide lower resistance and a shorter path for the electrons to travel resulting in higher performance.
LG energy have developed a unique technology on their Neon 2 modules using 12 small round wires rather than thin busbars, known a Cello which stands for ‘cell connection, electrically low loss, low stress and optical absorption enhancement’. Essentially the Cello Multi wire busbar technology lowers electrical resistance and further increases efficiency.
SOLAR ROOF TILES
Solar shingles are photovoltaic cells designed to look like and integrate with conventional asphalt roof shingles. First commercially available in 2005, solar shingles were much costlier than traditional “bolt-on” photovoltaic panels, and thus were used mainly by those wanting to go solar but maintain a traditional roofline. But more recently solar shingles have become price-competitive with bolt-on panels, and are getting much more popular accordingly. Eco-conscious home and building owners might find solar shingles especially attractive when they are re-shingling anyway since the solar shingles also double as functional, protective and weatherproof roof shingles in their own right.
SOLAR ROOF TILES
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