Tag Archives: solar energy

Cleaning Solar Panels without Water

Most installations of solar panels are in desert areas that provide plentiful amounts of sunshine. While the desert property is cheap, winds are also common. When the wind blows, it carries a huge amount of dust, which forms a layer on the solar panels. Dust on the solar panel reduces their performance, and the electrical output from the panel can reduce by about 30% with only a month of exposure to the elements.

For a 150 MW solar panel installation, even a 1% drop in the output could translate to a loss in yearly revenue to the tune of US$200,000. According to researchers, a reduction of 3 to 4% power output from solar plants all over the world could lead to an annual loss of nearly US$3.3 billion to US$5.5 billion. Therefore, it is essential to keep solar panels clean, and the most common technique presently is by using water.

However, keeping solar panels clean presently requires an annual supply of nearly 10 billion gallons of water. This is enough water necessary for a million people in developing countries. Cleaning solar panels without water is a labor-intensive task, and carries with it the high risk of scratching and damaging the surface of the panels, which also leads to a reduction in the efficiency of the cells.

MIT researchers have come up with an innovative method of cleaning the surface of solar panels. The method does not require the use of water, is contactless, and is automatic.

This innovative new method from MIT uses electrostatic repulsion. This makes the dust particles jump off the panels and does not require water or brushes. When activated, the system runs an electrode just above the surface of the panel. This results in the dust particles acquiring an electrical charge. The solar panels have a transparent conductive layer on top of their glass covering, and this is only a few nanometers thick. The system applies the same electric charge to this transparent conductive layer.

The same charge on the conductive layer and the dust particles makes them repel each other. As the conductive layer cannot move, the dust particles fall off the panel because of the repulsion. The researchers had to change the voltage until they found a range that overcame the adhesion forces and the pull of gravity and allowed the dust to lift away. They then automated the system using guide rails on the sides of the panel and an electric motor.

This is not the first time that engineers have tried to use an electrostatics-based approach to keeping solar panels clean. However, most approaches used electrodynamic screens and interdigitated electrodes. The problem with such screens is they allow ingress of moisture that can damage the electronics. If the atmosphere is dry, and moisture is not an issue, such as on the surface of Mars, the arrangement could be useful. However, on Earth, this can be a serious problem, because even the desert has ample amounts of moisture.

The researchers have found that as long as the humidity is more than 30%, dust removal was easy. However, the process of dust removal got increasingly more difficult with a decrease in humidity. 

Wash Your Solar Cells

To augment the energy supply, many are installing solar energy systems or residential solar panels. In general, these are flat units, placed at an angle on the rooftop. That naturally leads to the question of keeping them clean, which people equate to cleaning the roof itself. As this cleaning is usually left to the rainwaters, the next question comes as whether we should depend on the rains for cleaning the surface of the installed solar cells as well. Moreover, some also worry about whether water is good for the cells and will not damage them.

For these skeptics, scientists have a new type of waterproof solar cell that generates electricity even when compressed, stretched, or soaked in water. This is good news for those in the wearable solar cell industry. Wearable solar cells provide power to devices for monitoring health, usually as sensors incorporated into clothing, recording heartbeats, body temperature, and other parameters, for providing early warning of medical problems.

These extremely thin and flexible organic solar cells, or photovoltaic cells as scientists call them, are a result of research in the University of Tokyo. A material, by name PNTz4T, coats both sides of the cells with a stretchable and waterproof film. The researchers then deposit the cells within an inverse architecture of a one-micrometer-thick parylene film. After this process, the researchers applied an acrylic-based elastomer coating to both sides of the cell, which prevents water infiltration.

The elastomer is transparent and allows light to enter the cell, but does not allow air and water from leaking into it. This makes the solar cells longer lasting compared to conventional photovoltaic cells. The researchers decided to test the effectiveness of the coating by immersing the coated cells in water for two hours. They found the cells’ resistance to water to be high, as its efficiency to convert from light to electricity dropped by only 5.4 percent.

Next, the researchers tested the durability of the coated cell by subjecting it to compression. They compressed the cell by half for twenty cycles while placing drops of water on it. Even after surviving this brutal test, the researchers found the cell still had more than 80% of its original efficiency still intact. The above tests confirmed the cells’ mechanical robustness, high efficiency, and great environmental stability.

Not only as wearable sensors, these new washable, stretchable, and lightweight organic photovoltaic cells will also be suitable as long-term power sources as rooftop solar panels. Most experts do not recommend washing solar cells regularly for keeping the dust and debris from collecting on the surface. Since these new solar panels have the additional feature of being waterproof, there is no danger from giving them a frequent wash.

Experts feel it is best to let the rain take care of washing the solar panel. By monitoring the system functionality such as checking the energy bills and usage on monthly basis, the user can detect changes in the electricity bill. Another check can be made by visually inspecting the surface of the panels. If cleaning is necessary, washing it with a hose of water will do the job.

Five New Advancements in Solar Cells

The earth receives a huge amount of sunlight every hour. Converted to electricity, this would amount to 52 PW/hr. This is more than ten times the entire amount of electricity produced per hour by China in 2013. In the same year, top countries of the world together produced only 16 PW/hr. of electricity. As this is much less than the actual potential of generation of electricity from the solar energy falling on the planet earth, several countries are actively engaged on research and development on photovoltaic cells.

There have been several breakthroughs in photovoltaic cell technology. For instance, early cells were very expensive and inefficient—almost $1800/watt and 4% respectively. Costs have now come down to $0.75/watt, while the efficiency has increased to 40%. Since, then, there have been several other breakthroughs in the solar cell domain.

Printable Solar Cells

At the New Jersey Institute of Technology (NJIT), researchers have developed a printable solar cell, and they can print or paint this on a surface. According to the lead researcher Dr. Mitra, they are aiming for printable sheets of solar cells that any home-based inkjet printer will be able to print and place on the wall, roof, or billboard to generate power. The printable cells are made of carbon nanotubes 50,000 times smaller than a human hair.

All-Carbon Flexible Solar Cells

Scientists at the Stanford University have made these flexible solar cells from a special form of carbon called graphene. According to Zhenan Bao, one of the team and a professor of chemical engineering at Stanford, the flexible carbon solar cells can be coated on to the surface of cars, windows, or buildings for generating electricity.
By replacing expensive materials when manufacturing conventional solar cells, the all-carbon solar cell is expected to make the cells much cheaper.

Transparent Solar Cells

At the Michigan State University, a team of researchers has made solar cells that appear transparent to the visible spectrum of sunlight. Rather, these non-intrusive solar cells convert light beyond the visible spectrum to electricity. Therefore, these can be used on smartphones, on windowpanes of buildings, or in windshields of vehicles without impeding their performance.

According to MSU assistant professor Richard Lunt, their aim is to produce solar harvesting surfaces that are invisible. However, the present efficiency of these cells is a mere 1%, as they are in their initial stages.

Wearable Ultra-Thin Solar Cells

In South Korea, at the Gwangju Institute of Science and Technology, scientists have used gallium arsenide to develop solar cells with a thickness of just one micrometer, more than 100 times thinner than human hair. According to Jongho Lee, an engineer at the institute, such thin cells can be integrated into fabric or glass frames to power the next wave of wearable electronics.

To create such thin cells, the scientists removed extra adhesives from the traditional cells, and cold-welded them on flexible substrates at 170°C.

Solar Cells with 100% Efficiency

By extracting all the energy from excitons, researchers at the University of Cambridge have found methods of making solar cells that are more efficient. Such a hybrid cell combines organic material and inorganic material into high conversion efficiency.

Transparent Harvester of Solar Energy

Common belief is anything that harvests solar energy must be non-transparent. Popular logic is if sunlight is allowed to pass freely through the collector, it cannot lead to energy production. Although this may be partly true for the visible spectrum of light from the sun, it must also be considered that the sun gives out radiations beyond the band of light visible to the human eye.

Therefore, even see-through solar concentrators can successfully harvest energy from sunlight. Now, a team of Michigan State University researchers has proven this by creating a transparent solar concentrator. They claim to be able to turn any window into a photovoltaic solar cell. Not only windows, any sheet of glass, including the screen of a smartphone, can be turned into a harvester of solar energy. All the while, the panel remains truly transparent.

Earlier, transparent solar cells were restricted to tinted glass or compromised the visibility. This did not become popular, as people felt rather uncomfortable sitting behind colored glass making for colorful environments. In contrast, the new solar cell from the Michigan State University is completed transparent.

At MSU, researchers used TSLC or Transparent Luminescent Solar Concentrators. These employ organic salts for absorbing wavelengths of light normally invisible to the human eye, such as the infrared and the ultraviolet light. The researchers can tune the amount and composition of the organic salts to pick up only the near-infrared and the ultraviolet wavelengths leaving the visible spectrum untouched. The organic salts make the captured wavelengths glow at another wavelength – the infrared.

The TSLC then guides the infrared light to the edge of the panel, where it encounters thin strips of photovoltaic cells, which converts it to electricity. The organic salts do not absorb or emit any light in the visible spectrum and the panel looks extraordinarily transparent to the human eye.

The process is non-intrusive and opens doors to several opportunities of deploying solar energy creatively. Tall buildings with lots of windows can benefit tremendously with this technology, as can any mobile device demanding high aesthetic quality. The biggest benefit is you can have a solar harvesting surface and need not even know that it is present.

At present, the energy producing efficiency of TSLC is rather low, of the order of 1 percent, and additional work is needed to improve its performance. However, researchers are confident they will eventually increase the efficiency to above 5 percent. In comparison, non-transparent luminescent concentrators offer efficiencies of up to 7 percent.

In July 2014, the journal of Advanced Optical Materials carried an article describing the transparent solar cells. Apart from the lead researcher Richard Lunt, Yimu Zhao, Benjamin Levine and Garrett Meek are other members of the research team working on transparent solar cells at MSU.

Lunt has cofounded a Silicon Valley start-up – Ubiquitous Energy – for commercializing the transparent solar cell. The researchers have named the technology ClearView Power. They plan to integrate it directly on surfaces of mobiles, creating an auxiliary power source. They also want to promote this as a power-producing invisible coating for windows.

High Efficiency Hybrid Solar Cells

Normally, a modern silicon solar cell exhibits a maximum theoretical efficiency of about 33.7 percent. A majority of the sunlight falling on the solar cell – more than 66 percent – is not converted to electricity and is simply wasted in heating up the cell. Now, a new type of solar cells may be able to boost this efficiency to 95 percent or more.

The University of Cambridge Cavendish Laboratories is researching on a new type of high-efficiency hybrid solar cell. The UK researchers are using an organic formulation to put in as a layer on top of a standard silicon solar cell. This layer will help the solar cell to reach its target of the hard-to-believe 100 percent efficiency.

The top layer of special organic formulation coating on the solar cell helps to absorb high-energy light and produce pairs of triplets. Inorganic solar cells underneath can efficiently absorb these triplets. Generally, the cells cannot convert the high-energy radiation into electricity and these radiations only serve to heat up the solar cells. The organic film on top of the solar cells converts the wasted energy into a form that the underlying solar cell can turn into useful electricity.

With an increase in efficiency brought about by the Cavendish Laboratory hybrid approach, solar energy harvesting farms can be reduced in size significantly, while still producing the same amount of electricity.

According to Maxim Tabachnyk, Scholar, and Akshay Rao, research fellow at Gates Cambridge, and other members of the Cavendish Laboratory at the University, they have developed a film to convert wasted energy into useful form. The traditional solar cell is unable to convert high-energy light and wastes it as heat because of the fundamental limit of the solar cell’s power conversion efficiency.

The researchers coated the silicon solar cells with a special organic layer. This layer functions to distribute the energy of the incoming high-energy photons into two triplet excitons that in turn transfer their electrons on to the silicon cells.

The researchers had to first characterize the ultra-fast processes occurring at the organic/inorganic interface. For this, they directed ultra-short laser pulses into organic pentacene and studied the effect with laser spectroscopy. By following the transfer of energy taking place within a femtosecond (a billionth of a billionth of a second), they confirmed the presence of two electrons for each high-energy photon. Normally, only one electron is generated per photon.

After proving the concept that each high-energy photon can generate two electrons, the researchers had to find an alternative candidate to replace pentacene, which is not a suitable candidate to produce electrons suitable for silicon to absorb. They have now found a suitable organic material that can produce electrons with excitation higher than the band gap or the minimum absorption energy of silicon. The organic material is cheap and can be printed or even sprayed on as ink on top of traditional silicon solar cells.

According to Tabachnyk, normal solar cells harvest only the bright single-spin excitation electrons produced by the photons. The organic layer extends the ability of the cells by allowing them to harvest additional electrons from high-energy photons producing dark spin-triplet excitations.

Can a Solar Cell Store Its Own Power?

Can a Solar Cell Store Its Own Power?

Researchers at Ohio State University have invented a device that looks like a solar cell but has the ability to store the power it generates. The patent-pending device is the world’s first solar battery. On October 3, 2014, the researchers reported in the journal – Nature Communication – that they have succeeded in combining a solar cell and a battery into a single hybrid device.

The innovation is a special solar panel in the form of a mesh that allows entry of air into the battery. Another unique process allows electrons to be transferred between the solar panel and the electrodes of the battery. Light and oxygen entering the device enable chemical reactions to charge the battery.

According to Yiying Wu, Professor of chemistry and biochemistry at the Ohio State University, they will license the new solar battery to industry. Wu expects that the solar battery will tame the costs of renewable energy.

A solar panel is typically used to capture light for converting it to electricity, which is then stored in a cheap battery for later use. By integrating the two functions into a single device, installation becomes simpler and costs go down. The new solar battery may typically bring down the costs by about 25 percent.

The invention also has another advantage. The long interconnections between solar panels and its battery introduce ohmic resistance that reduces the solar energy efficiency because of heat generation when charging. Typically, about 20 percent of the electricity generated by the solar cells is wasted as heat when charging the battery. With the new design, nearly all the electricity generated reaches the battery.

Wu and his students have also developed a high-efficiency battery for use with their solar cells. An earlier designed battery, invented by Wu and his research team, won them the 2014 clean energy prize of $100,000 from the US Department of Energy. The researchers have created a technology spinoff – KAir Energy Systems, LLC – to develop the battery.

The high-efficiency battery is air-powered, meaning it breathes in air when discharging and breathes out when charging. The battery discharges by the chemical reaction of potassium and oxygen. The researchers faced a formidable challenge when trying to combine a solar panel with the KAir type of battery. Typical solar cells are solid panels of semiconductor material and this would prevent air from entering the battery.

Wu and his research team had to redesign the solar panel to make it permeable. They did this by using titanium gauze, a flexible fabric. They grew vertical rods of titanium dioxide on the fabric, similar to blades of grass growing on soil. The rods capture sunlight, while air passes freely through them and the gauze.

Normally, interconnecting a solar cell and a battery requires four electrodes – two on the solar panel and two on the battery. The hybrid design of the researchers has reduced the number of electrodes required to three.

The mesh in the solar panel forms the first electrode. Under this, a thin sheet of porous carbon forms the second electrode, while a lithium plate forms the third. Layers of electrolyte sandwiched between the electrodes forms the battery to store electricity.

How about a solar energy bikini for this summer?

We thought we’d seen just about everything powered by solar panels or solar film until we came across this bikini. Made by Solarcoterie, this bathing suit is made of photovoltaic film strips sewn together in series with conductive thread! With a USB connection, you could be laying on the beach and powering your iPod at the same time. The suit is constructed of 1″ x 4″ solar strips which terminate in a 5V regulator and a female USB connector – perfect for powering your iPod.

The downside is that the bathing suit is a currently custom made offering only so this is not something readily available at your local store. And, we don’t have the power specs but wonder if this also wouldn’t be a great solution for charging other small appliances needed at the beach – like most smartphones and iPads. Of course, this got us thinking about our dream ideas of powering a small cooler (imagine never needing ice at the beach!) or a small fan for cooling off while you’re baking in the sun. The biggest item on our wishlist is always a blender but we’ve got that covered with our battery operated one!

No matter what, we think this use of solar technology is genius.

Solar Energy – a beginner’s look

Solar energy is an exciting field for both scientific study and home and office use, representing the modern drive to find clean, sustainable ways to power everyday life while protecting the planet for generations to come. Solar energy is created by the sun, which plays host to constant explosions of heat and energy. This energy radiates light that eventually reaches Earth, where water, land, and the clouds in the atmosphere absorb a portion.

This light manifests as heat and helps to regulate the planet’s water cycles, including rainfall. Solar energy is converted into food for trees and plants via photosynthesis, and in turn provides the Earth with oxygen and the natural materials necessary for human habitation.

With the many intrinsic and ancient benefits of solar energy we’ve enjoyed over the centuries, it is perhaps unsurprising that modern man has taken it upon himself to truly harness the potential of this natural power source. Solar power is fast becoming a popular way for businesses and homeowners to cut down on energy costs while making a commitment to the health of the environment.

Solar power itself can take many forms, operating for instance through the means of solar panels, which convert radiation from the sun to practical electric energy suitable for a variety of uses, and can store this energy in batteries.

Other common applications for solar power include pumps, switches, and fans for various industrial purposes, greenhouse and other thermal agricultural uses, and special technologies employed in space, such as those used to operate satellites.

Taking advantage of natural solar energy is not only an efficient way to power machines, houses, and more, but is cost-effective as well. Many entrepreneurs and environmentally savvy homeowners find that using solar power greatly diminishes their average monthly electricity expenditures, adding a welcome benefit to the clean and green energy source.

As oil prices fluctuate, and we become more aware of our impact on the global ecosystem, it is becoming imperative that we search for and use renewable sources of energy, and seek to live in a sustainable fashion, so that future generations can enjoy a happy and healthy planet. The use of solar energy through solar power panels and other technologies is an important step in reducing your overall energy footprint, and can give you — and your wallet — a sincere sense of peace and well being.

The New York Jets are green on and off the field

With the installation of an array of 3000 solar panels, the New York Jets have really set themselves apart from other professional sports teams. Their team headquarters and 120,000 square foot training facility will be powered by the solar panels that will generate an estimated 750,000 kilo-watt hours of electricity.

Other sports teams have installed alternative energy systems at their training camps and stadiums, but the system at the Jets facility is the largest to date.

The New York Jets can wear their long-time green jerseys proudly – their commitment to providing a source of green energy at their training camp is an inspiration for the rest of the league.

The future of solar power: Flexible solar panels

As the popularity of solar energy grows, so does the selection of solar equipment that is made available. The big trend in solar energy right now is flexible panels.

Flexible solar panels have many advantages over traditional framed solar panels. The flexible solar panels are lightweight so there is less worry in the installation process and during use. They can also be installed on a semi-permanent basis because they are very easy to remove and install elsewhere.

Probably the biggest advantage is that they can be manufactured in any size or shape so they can be used in unconventional places.

In the past, the biggest disadvantage of the flexible solar panels is that they could only power low-wattage devices however that has changed significantly in the past year as new solar technology has been introduced. The newest flexible panels that are available for commercial applications have the ability to collect more energy than earlier versions.

In the future, we will be seeing even more advances in solar energy products based on this emerging technology.