Category Archives: Solar Panels

Butterfly Technology Boosts Solar Panel Output

We normally do not relate butterflies to solar panels. After all, bees and butterflies are good for pollinating flowers and transforming them to fruits so that nature can propagate. On the other hand, solar panels are human creations that collect energy from the sun for the use of humankind. The link between the two seems rather distant, apart from the fact that the sun is the basic force that drives all life on our planet. However, science finds the humble butterfly could be holding the key to unlock new techniques for making solar energy cheaper and more efficient.

Cabbage White butterflies need to heat up their flight muscles before they can take off. Researchers at the University of Exeter have observed that the butterflies adopt a specific posture to maximize solar heat capture. The butterflies position their wings in a V-shape, which, when the researchers adapted for their solar panels, increased the power-to-weight ratio of the panels by about 17 times, making them more efficient.

Scientific Reports, a leading scientific journal has published the research. The research team contained members from both the Centre for Ecology and Conservation and the Environment and Sustainability Institute, based at the University of Exeter in the Penryn Campus in Cornwall. According to Tapas Mallick, the lead author of the research, although bio mimicry is popular in engineering, such unparalleled multidisciplinary research is opening pathways for developing low cost solar panels.

Butterflies usually depend on the sun to heat up their flight muscles before they can take off. However, researchers found the Cabbage White butterflies taking flight before other butterflies did, even on cloudy days. The energy from the sun is limited on cloudy days, forcing insects to make maximum use of the available energy to heat up their flight muscles.

Researchers observed that Cabbage White butterflies adopted a v-shaped posture, known as reflectance basking. That allows the butterflies to maximize the concentration of solar energy onto their thorax, so necessary for fast heating up the flight muscles. The wings of the butterflies have a specific sub-structure that allows maximum light from the sun to be most efficiently reflected onto their muscles, which warm up to the optimal temperature as quickly as possible.

The scientists then investigated the process of replication of the butterfly wings for developing a new, lightweight reflective material solar energy products could use. They found that by replicating the simple monolayer of scale cells on the butterfly wings, they could optimize the power-to weight ration of solar concentrators. That made the solar cells lighter and more efficient.

The team also found the optimal angle at which the butterfly held its wings. When the butterflies tilted their wings by about 17 degrees to the body, they were able to increase the temperature of their bodies by 7.3°C more than when they held their wings flat. By positioning the reflectors at 17 degrees within the solar cells, researchers found the output from the solar cells increased by 50 times.

Therefore, by studying the manner in which the lowly butterfly maximized its use of solar energy, scientists could not only double the output of their solar cells. They were also able to improve its power-to-weight ratio significantly.

Is Your Solar Panel Installed the Right Way?

Although few people would have noticed, the costs of solar photovoltaic cells have been dropping over the years. As the technology took off, costs plummeted in the first 12 years. However, between 2005 and 2009, global market demand surged, making it difficult for supply to keep up. As manufacturing picked up post 2009, solar PV cell prices have continued their downward trend steadily. Now, it makes sense for companies to switch to PV cells purely based on economics.

As solar grows to become a more attractive option, we see a clear preference in its adoption over adding new wind capacity. Navigant Research has predicted in their recent report that declining prices will result in the global solar PV market exceed $134 billion by 2020 – a phenomenal increase of 50% from this year. That means a solar capacity addition of nearly 435 Gigawatts.

However, getting the maximum benefit from solar PV cells requires mounting them the right way. As the sun traverses the sky in the daytime, the PV cells must either follow the trajectory of the sun or be mounted in the most optimum way for them to catch most of the sunlight. Automatically turning the PV cells to face the sun requires elaborate sensing and expensive movement mechanisms. Therefore, most people prefer fixed installations that are simple to put up and maintain.

Another thing to consider is the latitude tilt of the location where you intend to install the solar cells. If your location is below the 25 degrees latitude, tilt the solar panel towards the sun the same amount as the latitude number. At 25 degrees latitude, your panel must tilt by 25 degrees. Above 25 degrees, you will need to add five degrees for each additional five degrees of latitude up to 40 degrees. At and beyond 40 degrees latitude, add 20 degrees of tilt to the latitude number. The above is the general thumb rule people follow for solar PV panel installation. Consequently, most installations have the solar panels facing south to catch the maximum amount of sunlight.

Researchers at the Pecan Street Research Institute have discovered ways to additionally fine-tune the positioning and tilt of the solar panels to extract somewhat more power. During their research on impact of residential solar power on the power grid, they discovered that if the solar panels faced west rather than the customary south, they could generate about 2% more power.

So long, homeowners, utilities and architects believed that in the northern hemisphere, solar panels directed south would receive the maximum exposure from the sun. However, when studying home installations in Austin, Texas, Pecan Street researchers found that this was not true. In fact, they noticed south-facing panels generating less energy. They found west-facing panels generated more power in the afternoon, when the energy demand peaked.

As energy demand peaks, a typical home in Austin using solar panels reduces its reliance on the power grid by as much as 54%. However, for homes with west-facing panels, this number shot up to 65% – a significant power saving. Therefore, by merely shifting the angle, you may be able to achieve significant gain in solar power generation.

New Combination of Materials for Efficient Solar Cells

An international team of scientists have come together to build solar cells with high efficiency using a new blend of materials. The materials used allow the cells to convert sunlight into electrical energy without the addition of dopants. The design, termed DASH, uses molybdenum oxide and lithium fluoride.

Doing away with doping

Most of the solar cells use silicon wafers in the crystalline form. The wafer, along with the layers of materials deposited on it are doped or injected with special impurity atoms that either introduce free electrons or create electron deficiencies called holes. The presence of these extra electrons or holes increases the electrical conductivity of the material. However, the impurities introduce certain complexities within the crystalline structure, which bring down the performance.

Since solar cells are all about increasing the performance of these devices, researchers have been looking at means to eliminate the doping process. The international team has made available a cell prototype with a simple architecture. The journal Nature Energy has published an article on the design of the solar cell. James Bullock, a faculty member of Australian National University and a team member is the principal author of the paper. He has been a visiting researcher at Lawrence Berkeley National Laboratory and UC Berkeley as a part of the project.

Bullock explains that the simple structure of the cell designed by them would cut down the production and operational costs considerably, thereby enhancing the efficiency. The silicon cell, free from doping impurities designed by the team is termed DASH, which is the acronym for dopant-free asymmetric heterocontact. The efficiency of this product is 19%, which exceeds that of other dopant-free cells. The efficiency of previous cells of this category did not exceed 14%.

Special properties of the contact materials

The researchers applied several layers of amorphous silicon over a wafer of crystalline silicon. This was overlaid with very thin films of molybdenum oxide on the sun exposed surface and lithium fluoride at the bottom one. These two external layers are only a few nanometers thick and act as contacts for the holes and electrons. Ali Javey, a team member and a professor of Electrical Engineering and Computer Science at UC, Berkeley, explains that both molybdenum oxide and lithium fluoride have been selected for making up the contacts because of their special properties. The materials form transparent layers at this thickness. Molybdenum oxide has several imperfections in its crystalline structure that allow it to act as an effective hole contact.

Likewise, the defects in the lithium fluoride structure allow it to be a useful electron contact. Stefaan de Wolf, another team member has described in the article how the molybdenum oxide and lithium fluoride layers work as effective contacts when used with a combination of amorphous and crystalline silicon. In addition, these materials have allowed the scientists to come up with remarkable variations in their properties with different thicknesses.

The scientists used the thermal evaporation technique at room temperatures to apply the coatings. Javey said that the researchers intend to use the material combination for other semiconductor applications like transistors to improve their performance.

Solar Deployment Component Selection

The market for renewable energy is in turmoil right now, mainly because of lower utility costs, a desire for energy independence, incentivized solar installations, and low-cost batteries. Homeowners are now trending towards storing energy from solar cells rather than selling it back to the grid. However, that requires selecting storage components wisely.

Although 2016 was the cutoff year for the current solar energy tax incentives, there has been a successful bid to the Congress to extend the incentives up to 2020. As a result, the solar industry finds itself rejuvenated and this is having a reflective effect on the battery-based energy storage systems as well.

This has created a massive surge for ESS or energy storage systems in general, with particular emphasis on RES or renewable energy storage systems. Designers of inverters and power conversion architectures now have enormous opportunities, especially those designing for home applications. For instance, Tesla has announced the Powerwall, a 10-kWh storage system suitable for homes, businesses, and utilities.

Designers and manufacturers are looking at advanced storage options such as ultra-capacitors and battery chemistry such as solid electrolytes, magnesium-ion, lithium sulfur, and next-generation flow and metal-air. The next-generation technologies for energy storage are expected to increase from near zero in 2015, to above $9 billion by 2030. Overall, the demand for batteries will increase from 66 GWh in 2014 to over 225 GWh in 2023
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Traditionally, people assumed that any excess power generated from solar panels and not used by the homeowner would be sold back to the utility. However, they are beginning to realize that saving the extra energy in batteries can help in the evenings, when the energy consumption is the highest and so are the utility rates. In the evenings, when there is no sun, the home can be less reliant on the grid, and be more self-sufficient if it relies on the backup batteries to supply electricity.

So far, people had to buy all parts separately and put them together for a solar system. This included the battery, inverter and metering. However, all this involved multiple voltage conversions leading to unnecessary losses and overall lower efficiency.

Now, all that is changing. You can opt for a fully integrated system. This includes the PV monitoring, the inverter, and the DC/DC conversion to charge the battery. Metering now is highly advanced, with wireless technologies such as ZigBee, providing either computerized or application-based monitoring of the entire system.

However, that does not mean it simplifies optimizing the PV conversion. One still needs MPPT or maximum power point tracking to make sure of capturing the varying PV energy and transferring it to the battery with the minimum of power losses, regardless of the strength of the sun. For instance, this involves using a capacitor for stabilizing the PV voltage and dropping it sufficiently, ensuring the charging voltage matches the battery chemistry.

Although efficiency, cost, and ease of use are all factors critical to the system level, safety is still the highest priority. The emphasis is on isolation including both digital isolators and opt couplers to meet the IEC 62109-1 standards.

Raspberry Pi for the Solar Plant Monitoring System

In an effort to go green, solar energy is proving to be the forerunner. Collecting energy from the sun requires photovoltaic cells that convert the solar energy directly into the usable electrical form. Even computers are getting smaller and using less energy than before. As a result, several companies are building commercial products based on SBCs or Single Board Computers such as the hackable Raspberry Pi, or the RBPi.

For example, Storm Energy is a Germany-based firm designing the SunSniffer system that monitors photovoltaic solar power installations or all sizes. According to the company, their latest version is capable of even controlling the equipment. They have enhanced the flexibility and upgradability of their system by adding an RBPi SBC running a customized Linux OS, along with a customized expansion board.

Users can utilize the SunSniffer system and its backend software for monitoring and controlling solar equipment at the system, string and module levels. According to Storm Energy, use of the system enhances the system efficiency by more than 7 percent, as it enables monitoring temperature, cable power loss, interconnection bandwidth and many more functions that are important. An included iPhone application or SMS allows the SunSniffer system to present reports online, as well as on mobile devices.

The open Linux platform is the chief attraction for the company to select an RBPi for its proprietary SunSniffer solar plant monitoring system. According to Storm Energy, using Linux has brought it maximum upgradability for SunSniffer. The Google translation of their website indicates that the company is able to make necessary changes and adjustments most economically because of Linux.

Storm Energy uses a Radio Ripple Control Receiver to turn on/off their solar inverters. This is an addition to simply monitoring their data. That gives them support for real-time reduction of their system’s performance for compensation just as the market premium models do. Apart from the system supporting meter readings, which are useful for solar-powered apartment buildings, the system also has SSL encryption to support future requirements complying with BSI Smart Meter Gateway.

Users can opt for additional integrated anti-theft protection on the SunSniffer. It includes features such as an emergency shutdown system and nighttime surveillance. According to the company, using the RBPi enables integration of cameras for optically monitoring the PV system with up to 1920×1080 pixels at 30 frames per second.

Just like any other conventional power station, constant monitoring of solar installations is necessary, since a solar plant is as prone to errors as with any other technical system. That includes pollution from soot, accumulation of dust and flower pollen. Usually, these form a thin layer on the surface of the modules, preventing sunlight from reaching the solar cells.

In addition, there can be damage such as glass breakage because of extreme temperature fluctuations, high snow loads, hail, swarms of birds soiling the modules and martens biting through cables. Moreover, there can be manufacturing defects such as joints becoming brittle leading to hot sports. Installation errors can include incorrect sorting of modules and forgotten plug connections leading to losses, and perilous electric arcs, etc. SunSniffer detects such errors and malfunctions quickly, enabling an increase in system 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?

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.

Energy Harvesting – How & Why

What Is Energy Harvesting – Why Is It Needed?

The process of extracting small quantities of energy from one or more natural, inexhaustible sources, accumulation and storage for subsequent use at an affordable cost is called Energy Harvesting. Specially developed electronic devices that enable this task are termed Energy Harvesting Devices.

The world is facing acute energy crisis and global warming, stemming from rapid depletion of the traditional sources of energy such as oil, coal, fossil fuels, etc., which are on the verge of exhaustion. Not only is the global economy nose-diving, but the damage to the environment is also threatening our very existence. Natural calamities like earthquakes, tsunamis, droughts, floods, storms, etc., have become the order of the day. Economic growth is generating a spiraling demand for energy, goading us to tap alternative sources of energy on a war footing. Our very existence on the planet Earth is at stake, and we must find immediate solutions to meet the energy needs for survival.

Alternative Energy Sources Available

There are many, almost inexhaustible, sources of energy in nature. In addition, these energy forms are available almost free, if available close to the place where required. Sources include: Solar Energy, Wind Energy, Tidal Energy, Energy from the waves of the ocean, Bio Energy, Electromagnetic Energy, Chemical Energy, and so on.

Recent Advances in Technology

The sources listed above provide miniscule quantities of energy. The challenge before us is to gather the miniscule amounts and generate meaningful quantities of energy at affordable cost. Until very recently, this has remained an unfulfilled challenge.

Today, research and innovation has resulted in creation of more efficient devices to capture minute amounts of energy from these sources and convert them into electrical energy. Besides, better technology has led to lower power consumption, and hence higher power efficiency. These have been the major propelling factors for better, more efficient energy harvesting techniques, making it a viable solution. These solutions are considered to be more reliable and relatively maintenance free compared to traditional wall sockets, expensive batteries, etc.

Basic Building Blocks of an Energy Harvesting System

An Energy Harvesting System essentially consists of:

a) One or more sources of renewable energy (solar, wind, ocean or other type of energy)
b) An appropriate transducer to capture the energy and to convert it into electrical energy (such as solar cells for use in conjunction with solar power, a windmill for wind power, a turbine for hydro power, etc.)
c) An energy harvesting module to accumulate, store and control electrical power
d) A means of conveying the power to the user application (such as a transmission line)
e) The user application that consumes the power

With advancement in technology, various interface modules are commercially available at affordable prices. Combined with the enhanced awareness of the efficacy of Energy Harvesting, more and more applications and utilities are progressively using alternative sources of energy, which is a definite sign of progress to effectively deal with the global energy crisis.

Optional addition of power conditioning systems like voltage boosters, etc., can enhance the applications, but one must remember that such devices also consume power, which again brings down the efficiency and adds to cost.

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.