Tag Archives: solar panel

Why transparent solar cells could replace windows in the near future

No matter how sustainable, eco-friendly, and clean sources of energy they are, conventional solar panels require a large setup area and heavy initial investment. Due to these limitations, it’s hard to introduce them in urban areas (especially neighborhoods with lots of apartment blocks or shops). But thanks to the work of ingenious engineers at the University of Michigan, that may soon no longer be the case.

The researchers have created transparent solar panels which they claim could be used as power generating windows in our homes, buildings, and even rented apartments.

Image credits: Djim Loic/Unsplash

If these transparent panels are indeed capable of generating electricity cost-efficiently, the days of regular windows may be passing as we speak. Soon, we could have access to cheap solar energy regardless of where we live — and to make it even better, we could be rid of those horrific power cuts that happen every once in a while because, with transparent glass-like solar panels, every house and every tall skyscraper will be able to generate its own power independently.

An overview of the transparent solar panels

In order to generate power from sunlight, solar cells embedded on a solar panel are required to absorb radiation from the sun. Therefore, they cannot allow sunlight to completely pass through them (in the way that a glass window can). So at first, the idea of transparent solar panels might seem preposterous and completely illogical because a transparent panel should be unable to absorb radiation. 

But that’s not necessarily the case, researchers have found. In fact, that’s not the case at all.

Professor R. Lunt at MSU showing the transparent luminescent solar concentrator. Image credits: Michigan State University

The solar panels created by engineers at the University of Michigan consist of transparent luminescent solar concentrators (TLSC). Composed of cyanine, the TLSC is capable of selectively absorbing invisible solar radiation including infrared and UV lights, and letting the rest of the visible rays pass through them. So in other words, these devices are transparent to the human eye (very much like a window) but still absorb a fraction of the solar light which they can then convert into electricity. It’s a relatively new technology, only first developed in 2013, but it’s already seeing some impressive developments.

Panels equipped with TLSC can be molded in the form of thin transparent sheets that can be used further to create windows, smartphone screens, car roofs, etc. Unlike, traditional panels, transparent solar panels do not use silicone; instead they consist of a zinc oxide layer covered with a carbon-based IC-SAM layer and a fullerene layer. The IC-SAM and fullerene layers not only increase the efficiency of the panel but also prevent the radiation-absorbing regions of the solar cells from breaking down.

Surprisingly, the researchers at Michigan State University (MSU) also claim that their transparent solar panels can last for 30 years, making them more durable than most regular solar panels. Basically, you could fit your windows with these transparent solar cells and get free electricity without much hassle for decades. Unsurprisingly, this prospect has a lot of people excited.

According to Professor Richard Lunt (who headed the transparent solar cell experiment at MSU), “highly transparent solar cells represent the wave of the future for new solar applications”. He further adds that these devices in the future can provide a similar electricity-generation potential as rooftop solar systems plus, they can also equip our buildings, automobiles, and gadgets with self-charging abilities.

“That is what we are working towards,” he said. “Traditional solar applications have been actively researched for over five decades, yet we have only been working on these highly transparent solar cells for about five years. Ultimately, this technology offers a promising route to inexpensive, widespread solar adoption on small and large surfaces that were previously inaccessible.”

Recent developments in the field of transparent solar cell technology

Apart from the research work conducted by Professor Richard Lunt and his team at MSU, there are some other research groups and companies working on developing advanced solar-powered glass windows. Earlier this year, a team from ITMO University in Russia developed a cheaper method of producing transparent solar cells. The researchers found a way to produce transparent solar panels much cheaper than ever before.

“Regular thin-film solar cells have a non-transparent metal back contact that allows them to trap more light. Transparent solar cells use a light-permeating back electrode. In that case, some of the photons are inevitably lost when passing through, thus reducing the devices’ performance. Besides, producing a back electrode with the right properties can be quite expensive,” says Pavel Voroshilov, a researcher at ITMO University’s Faculty of Physics and Engineering.

“For our experiments, we took a solar cell based on small molecules and attached nanotubes to it. Next, we doped nanotubes using an ion gate. We also processed the transport layer, which is responsible for allowing a charge from the active layer to successfully reach the electrode. We were able to do this without vacuum chambers and working in ambient conditions. All we had to do was dribble some ionic liquid and apply a slight voltage in order to create the necessary properties,” adds co-author Pavel Voroshilov.

Image credits: Kenrick Baksh/Unsplash

PHYSEE, a technology company from the Netherlands has successfully installed their solar energy-based “PowerWindow” in a 300 square feet area of a bank building in The Netherlands. Though at present, the transparent PowerWindows are not efficient enough to meet the energy demands of the whole building, PHYSEE claims that with some more effort, soon they will be able to increase the feasibility and power generation capacity of their solar windows.   

California-based Ubiquitous Energy is also working on a “ClearView Power” system that aims to create a solar coating that can turn the glass used in windows into transparent solar panels. This solar coating will allow transparent glass windows to absorb high-energy infrared radiations, the company claims to have achieved an efficiency of 9.8% with ClearView solar cells during their initial tests.

In September 2021, the Nippon Sheet Glass (NSG) Corporation facility located in Chiba City became Japan’s first solar window-equipped building. The transparent solar panels installed by NSG in their facility are developed by Ubiquitous Energy.  Recently, as a part of their association with Morgan Creek Ventures, Ubiquitous Energy has also installed transparent solar windows on Boulder Commons II, an under-construction commercial building in Colorado.

All these exciting developments indicate that sooner or later, we also might be able to install transparent power-generating solar windows in our homes. Such a small change in the way we produce energy, on a global scale could turn out to be a great step towards living in a more energy-efficient world.

Not there just yet

If this almost sounds too good to be true, well sort of is. The efficiency of these fully transparent solar panels is around 1%, though the technology has the potential to reach around 10% efficiency — this is compared to the 15% we already have for conventional solar panels (some efficient ones can reach 22% or even a bit higher).

So the efficiency isn’t quite there yet to make transparent solar cells efficient yet, but it may get there in the not-too-distant future. Furthermore, the appeal of this system is that it can be deployed on a small scale, in areas where regular solar panels are not possible. They don’t have to replace regular solar panels, they just have to complement them.

When you think about it, solar energy wasn’t regarded as competitive up to about a decade ago — and a recent report found that now, it’s the cheapest form of electricity available so far in human history. Although transparent solar cells haven’t been truly used yet, we’ve seen how fast this type of technology can develop, and the prospects are there for great results.

The mere idea that we may soon be able to power our buildings through our windows shows how far we’ve come. An energy revolution is in sight, and we’d be wise to take it seriously.

Shade from solar panels makes for more and more diverse flowers

Solar panels make for very good real estate — if you’re a flower. A new paper reports that the partial shade these panels generate can increase the abundance of flowers and create a delay in their blooming time, which could help improve our agricultural output. The authors explain that extending bloom times is important for pollinators, as it provides them food later in the season.

Image credits Berkan Küçükgül.

New research at the Oregon State University could have important implications for managers of land under solar panels, farmers, and those concerned with the plight of pollinators such as bees. According to the findings, these devices do impact the plants living in their shade, but that’s not to say they have a negative impact. In fact, the shady areas beneath solar panels increase flower density.

Shady places

“The understudy of solar panels is typically managed to limit the growth of plants,” said Maggie Graham, a faculty research assistant at Oregon State and lead author of the paper. “My thought coming into this research was can we flip that? Why not plant under solar arrays with something beneficial to the surrounding ecosystem, like flowers that attract pollinators? Would insects even use it? This study demonstrates that the answer is yes.”

The team says their study is the first to look at how solar panels impact flowering plants and insects. The findings come just after some states, including Minnesota, North Carolina, Maryland, Vermont, and Virginia, have implemented statewide guidelines and incentives meant to support pollinator-focused solar installations.

Pollinators are an essential lynchpin of virtually every ecosystem on Earth. They’re directly involved in the reproduction of 75% of flowering plant species and 35% of crop species globally, and their services are valued at an estimated 14 billion USD annually. Which is a lot!

That being said, they’re also struggling. One of the most pressing issues they’re facing is a global decline in habitat due to urbanization, agriculture, and other types of land use. Climate change is also having a negative impact on these insects and further impacting their available habitat.

But solar panels — of which there are increasing numbers in the US — could help. Agrivoltaics is the approach of installing solar energy production on agricultural land, such as cropfields or grazing areas. The authors have previously studied agrivoltaics and its potential, finding that it could provide 20% of total electricity generation in the United States with an investment of less than 1% of the annual U.S. budget. It would also slash around 330,000 tons of carbon dioxide emissions per year, create jobs, and have a minimal impact on crop yields.

Those findings spurred the current research. The team wanted to better understand how these panels impact plant life around them, so they collected data on pollinators and plant populations in the US from seven, two-day sampling events from June through September 2019. These samplings corresponded with the post-peak bloom times for flowers. The collected data pertained to 48 species of plants and 65 different insect species. The study sites were broken into three categories: full shade plots under solar panels, partial shade plots under solar panels, and full sun plots (not under panels).

Among the most important findings, the team reports that flowers were most abundant in partial shade, where 4% more blooms were found compared to full sun and full shade plots — but there was no difference in the number of (flower) species between the plots. Plots with partial shade had 3% more pollinating insects on average than full-shade or full-sun plots. Partial-shade plots had more insects, and more insect diversity, than full-sun or full-shade spots. Finally, the team didn’t find any difference in the number of insects per flower among the plots.

“Unused or underutilized lands below solar panels represent an opportunity to augment the expected decline of pollinator habitat,” Graham said. “Near agricultural lands, this also has the potential to benefit the surrounding agricultural community and presents an avenue for future study.”

“Solar developers, policymakers, agricultural communities and pollinator health advocates looking to maximize land-use efficiency, biodiversity and pollination services might want to consider pollinator habitat at solar photovoltaic sites as an option.”

The paper “Partial shading by solar panels delays bloom, increases floral abundance during the late-season for pollinators in a dryland, agrivoltaic ecosystem” has been published in the journal Scientific Reports.

Korean researchers develop fully transparent solar panels — and they’re smartphone compatible

The thin, all-transparent solar panels can work as invisible generators for a number of electronic devices.

Depiction of the transparent solar cell (left), and the cell in action (right). Image credits: Nguyen et al (2020) / Journal of Power Sources.

Solar photovoltaics are the fastest-growing electricity source in the world, producing 2% of the world’s energy, up from a mere afterthought just a few years ago. Nowadays, most commercial solar panels have an efficiency between 15 and 20%, although outliers do exist on both sides of this range.

But in most cases, you can’t really use solar panels for electronics because of a very simple reason: they’re not transparent.

At first glance, transparent solar panels sounds like a contradiction, but that’s not necessarily the case. Partially transparent solar panels or other similar devices have been produced in recent years, although incorporating them into electronics has remained challenging. This is where the study, led by Professor Joondong Kim, comes in.

The team claims to have devised the first fully transparent solar cell (as opposed to previous efforts, which were not entirely transparent), and can therefore be implemented in electronics with relative ease. The cell’s combination of transparency and conversion of sunlight into energy is achieved through the use of nickel oxide semiconductors and titanium dioxide.

TItanium dioxide (TiO2) is already used in solar panel technology as a semiconductor. It’s not only abundant in the Earth’s crust (unlike other materials used in solar cells), but also non-toxic. Nickel oxide (NiO), on the other hand, is also a semiconductor, but it has high optical transparency features. Both of these materials are manufactured at low temperatures, in existing industrial settings. Together, they make for a transparent and eco-friendly solar panel.

However, this transparency comes at the cost of efficiency. The power conversion efficiency of the transparent solar panel is 2.1% — much lower than conventional black panels but still significant enough to be used in some applications.

The applications are countless. This technology could be integrated into buildings, windows, buses, even smartphones. This would make solar power more accessible, especially in a crowded urban environment where space is scarce. It may be a while before we charge our phones from their very screens, but it’s an idea that’s definitely looming on the horizon.

The study has been published in the Journal of Power Sources.


What are the pros and cons of solar energy? Here’s everything you need to know


Image: Flickr

Using solar energy to meet your power demands doesn’t just make you more environmentally friendly — in many parts of the world, it may actually save you money as well. It’s a win-win situation, but only if you’re in it for long-run. Of course, the viability also depends on where you live, since how much energy your panels can harvest and consequently save you money depends on constantly changing factors such as time of day, season and weather, as well as geographic traits such as climate and latitude.

With this in mind, consider these pros and cons of solar energy before making a purchase.

Pro: Solar is Renewable and Clean Energy

Solar power systems still generate some emissions and pollution during their manufacturing process. However, during their operation, solar panels do not generate additional greenhouse gases that warm the atmosphere. Once your solar power system is set up, you can live comfortably knowing that your home isn’t making a negative impact on the environment. This means that overall, solar is a much cleaner alternative to conventional sources of energy.

Solar power is also renewable, meaning it will never run out. Fossil fuels like coal and oil, on the other hand, are depletable. In the case of oil, at least, experts forecast it will run out in a couple of decades. By hopping over to solar, you’re hastening society’s transition towards renewable energy.

Pro: You Can Save a Lot of Money

This is one of the main advantages. When you use solar energy, you rely less on utilities to give you electricity. Consequently, your monthly bills go down, and you can even earn a credit on your statement. Electricity companies also pay customers for using panels for the extra energy they don’t use in a month, so you make money (in some countries, at least).

According to a report by the North Carolina Clean Energy Technology Center, backed by the SunShot Initiative, a fully financed solar PV system costs less than the energy purchased from a residential customer’s local utility in 42 of the 50 largest cities in the United States.

Figure 1: Ranking of 50 Largest Cities Based On Where Solar Offers Best Financial Value. Source: Going Solar in America (report)

Figure 1: Ranking of 50 Largest Cities Based On Where Solar Offers Best Financial Value. Source: Going Solar in America (report)

Pro: Improves the Value of Your Home

According to recent studies, a property’s value increases after solar is installed, as many people would love to move into a solar-powered home without actually going through the hassle of installing a solar power system. Know this, it’s a lot easier to make the decision of investing in solar knowing that you can actually turn a profit if you choose to move to a different town.

Pro: They’re Quieter than a Heartbeat

Solar panels make no noise whatsoever since they don’t contain any moving parts unless you order a PV array with a rotational axis that follows the sun throughout the daytime. Even then, however, the noise and nuisance are barely noticeable.

Another alternative energy source, wind turbines, might make noise because it is like a large fan blowing in your backyard. This is partly the reason why wind turbines are mostly located near farms or other remote locations because there aren’t many residences nearby to complain about the noise.

Pro: Solar Energy is Accessible in Remote Areas

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The cost of installing and maintaining solar energy panels is high in the beginning, but for areas that aren’t able to receive electricity the traditional way, adding these can be a huge benefit. Some areas are remote and off the grid, so electric companies cannot add a grid matrix to install electricity. These areas use the solar power so that they might use devices such as a microwave, washer and dryer, and the Internet. In some states, it’s debatable whether or not solar can beat the grid in terms of cost, but as far as remote off-grid locations are concerned, solar almost always beats a diesel or gas-fired generator.

Con: They may be Expensive to Install

While you save money by using less electricity, you spend a lot of money upfront buying solar panels. The bigger your energy needs, the more your cost is, and you can spend tens of thousands of dollars. The government can give you credits for adding solar panels, on the bright side. And some providers are actually offering interesting ways to fund your PV installation, so you don’t need to invest a massive initial capital to get going. Depending on where you live and your payment plan, your energy savings could equal your monthly payment. Also, thanks to advances in energy conversion and manufacturing, solar panels are cheaper than ever. According to Lawrence Berkeley National Laboratory, the median cost of a residential solar project fell from $12 per watt in 1998 to $4.70 per watt in 2013. EnergySage reports that the average cost of a 5-kilowatt rooftop system in the third quarter of 2014, before incentives, was as low as $3.70 per watt. In 2018, most homeowners are paying between $2.71 and $3.57 per watt to install solar. As you can see, solar energy is becoming cheaper year after year.

Using the U.S, average for system size at 6 kW (6,000 watts), solar system costs will range from $11,380 to $14,990 (after tax credits). For some, it makes sense to install now, for others perhaps you have to wait. Check out the calculator below to learn where you fit.

Here’s how much a solar power system will set you back on average in the following states:

Note that these are power system prices after the 30% federal tax cut for solar is applied. The price include cost of solar panel, storage, and installation. Source: Energy Sage / Solar Pricing Table 2018.

Con: It Might Not Work so Well in Your Area


Areas closer to the equator have far greater potential for producing solar electricity than those closer to the poles, and areas with consistent sun have greater solar potential then areas that are frequently overcast. Luckily, most of the United States has a great potential for solar energy, as you can see in this map of global solar radiation from the United Nations Environment Programme. For the absolute best solar resources in the United States, think southwest.

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New Mexico and Arizona are red hot with solar potential, and California, Nevada, Texas, Utah, and Colorado also have large areas highly favorable for PV development. If you live in one of these states, consider this point as a “pro” on your checklist. Also, another point you should consider is air pollution. Using solar power, you disconnect from the grid, thus generating less demand which is generally met by coal power plants. In effects, this ultimately reduces pollution. But if you’re living in a polluted area in the first places, you’ll experience poorer performance than otherwise because black carbons spewed by power plants combine to form haze and smog. These greatly reduce the amount of available sunlight by blocking the sun. In 1985, Atsumu Ohmura discovered that the amount of sunshine on Earth had dimmed by 10% between the 1960′s and 1980′s.  In addition, over the past 50 years, the average sunlight reduction was 3% per decade.

Con: Your roof might not be big enough

The more energy you use, the more space is required in order to host more solar panels. Solar panels are great because you can install them on your home’s rooftop, without the need for any additional space (apart for the batteries in a garage, for instance). However, if you’re really burning a lot of energy, the rooftop might not be enough.

Con: It’s Weather Dependent

Solar energy works during cloud and rainy days but its efficiency drops significantly. Just a few cloudy or rainy days could have a noticeable effect on your energy bill’s bottom line. Most importantly, solar energy cannot be collected during the night, which forces you to install batteries to store energy.

Con: Storing Solar Energy Costs a Lot (for now)

You use solar energy during the night hours thanks to batteries charged during the day. These batteries run from a few hundred dollars to over $1,500 and weigh from 60 to 420 pounds. You also require a place to store them that will not get wet and damage the battery, as well as buy accessories such as a cord and replaceable cells, which you’ll have to replace every 15 to 20 years. Consider, however, that now we have Tesla batteries! The list price for a new 13.5-kilowatt-hour (kWh) Tesla Powerwall 2.0 battery, which offers twice the storage capacity of the original Powerwall, is $5,900. Supporting hardware adds another $700 to the equipment costs, bringing the total to $6,600. Installation can add anywhere from $2,000 to $8,000 to the final bill.

Because Tesla Powerwalls aren’t available to the mass market yet, you’ll have to settle for other commercially available alternatives. In 2018, solar batteries range from $5,000 to $7,000 and from $400 dollars per kilowatt hour (kWh) to $750/kWh, cost of installation and additional equipment not included.

The cells change from transparent to orange-red when heated enough. Credit: UC Berkeley.

‘Solar windows’ change from transparent to tinted at high temperatures, blocking the sun while generating electricity

Berkeley chemists devised a new type of photovoltaic out of cesium-doped perovskite that not only provides power but also doubles as a tinted window. At room temperature, the solar cell is transparent but automatically tints once the temperature rises, blocking the sun, thereby cooling the space behind the window, and generating electricity at the same time.

The cells change from transparent to orange-red when heated enough. Credit: UC Berkeley.

The cells change from transparent to orange-red when heated enough. Credit: UC Berkeley.

Peidong Yang and colleagues at Berkeley Lab described their creative solar cell in the journal Nature Materials. Yang thinks the invention could be used for smart windows or displays in the buildings, vehicles, and the handheld devices of the future.

“This class of inorganic halide perovskite has amazing phase transition chemistry,” Yang said. “It can essentially change from one crystal structure to another when we slightly change the temperature or introduce a little water vapor.”

A cheap and versatile photovoltaics material

The perovskite mineral was originally found in the Ural Mountains in 1839, but it was only in 2009 that its ability to transport solar energy and convert it into electricity was discovered. Just a couple of years later, rated efficiency in the lab had soared from 3.8% to 19.3%, a pace of improvement unmatched by any other solar technology. Currently, the leading commercial solar tech employs crystalline silicon solar cells, which convert roughly 25% of incoming photon energy into electricity but have decades worth of research behind them.

What makes this mineral so exciting is its uncanny ability to diffuse photons over a long distance throughout the cell when prepared in a liquid solution. Typically, solar cells convert energy to electricity by exploiting the hole-pair phenomenon. The photon hits the semiconducting material, then if its energy falls into the semiconductor band gap, an electron is knocked off, leaving a gap in the material or a ‘hole’. The electron travels from atom to atom within the material, occupying holes and knocking out other electrons at the same time until it eventually reaches an electrode and has its charge transferred to a circuit. Last step: profit and generate electricity.

The key is to have electrons moving for as long as possible, and thanks to its diffusing capabilities, perovskite can theoretically generate more electricity than silicon. Perovskite is also dirt cheap which is highly important if we’re ever to cover a significant portion of the planet’s surface with solar cells for a 100% sustainable energy future. Organometal halide perovskites can also be used the other way around — namely turning electricity into light with high-brightness LEDs, manufactured at low cost and more easily than current commercially-available options.

Credit: UC Berkeley.

Credit: UC Berkeley.

Pull the shades

Yang and colleagues showed that perovskite can be extremely versatile. By tweaking the chemicals in the materials (cesium, lead, iodine, and bromine), the researchers were able to change the material’s transparency.

For the last couple of years, the team has been working on a perovskite solar cell that changes from transparent to opaque when heated. Last year’s version could tint when heated but the cell’s conversion efficiency dropped drastically after several cycles. The new cell retains its conversion efficiency after many cycles between transparent and reddish-tint.

One major downside is that the warmed perovskite transforms only up to 7% of its energy into electricity, which is well below conventional solar cells. Another drawback is that the cells won’t tint unless they’re heated to more than 100°C. However, the researchers claim they’ve already come up with a variation that switches between 50°C–60°C. With a bit more tweaking, they might just find the right composition for their perovskite.

“The solar cell shows fully reversible performance and excellent device stability over repeated phase transition cycles without any color fade or performance degradation,” said Minliang Lai, a graduate student in Yang’s group. “With a device like this, a building or car can harvest solar energy through the smart photovoltaic window.”

Credit: Pixabay.

How exactly do solar panels work?

Credit: Pixabay.

Image in public domain

If you told the average person only thirty years ago that black panels left in the sun would generate copious amounts of electricity for homes and businesses, the likeliest reaction would have been a condescending grin. Luckily the technology to capture energy from the sun — which shines enough light on Earth’s surface in an hour to power the whole world’s energy for an entire year — has improved immensely, to the point that for many homeowners it’s cheaper to install solar panels on their rooftop than to use the grid.

The first solar cell was constructed by Charles Fritts in the 1880s and had a conversion efficiency of just 1% — hardly enough to be useful. Today, however, the most efficient commercially available solar panels on the market have efficiency ratings as high as 22.5%, while the majority of panels range from 12% to 16% efficiency rating. However, solar efficiency can climb to rated efficiencies as high as 46%, in the case of multi-junction photovoltaic (PV) cells that pick up energy from multiple different spectra.

If all this sounds somewhat familiar, it’s because plants have been harnessing energy from the sun for hundreds of millions of years — there’s nothing new about how solar energy works, we are just using it in a different way. Plants convert the sun’s energy into chemical energy, whereas solar cells produce electricity. This leads us to an important question: how do solar panels work?

Solar panels ABC

Solar panels generate electricity when photons knock electrons off from the material. In fact, a solar panel is comprised of an array of smaller units called photovoltaic cells, which are the things that actually convert solar energy into electricity. The typical solar panel is additionally comprised of a metal frame, a glass casing, and various wiring to allow current to flow from the silicon cells. Because solar panels generate direct current, an inverter is also required to allow you to use the electricity in your home.

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Physics-wise, solar power is predicated on the photovoltaic effect (photo meaning “light” and voltaic meaning “electricity”), in which two dissimilar materials in close contact produce an electrical voltage when struck by light or other radiant energy. In solar energy, the materials belong to a class called semiconductors — neither conductors nor electrical insulators that allow electrons to flow under certain conditions. The most common semiconductor used in the solar industry is silicon.

Semiconductors can be one of two types: P and N. Every solar cell sandwiches two of these semiconductors, one layer of P-type and one layer of N-type (which looks a lot like a battery).

P-type semiconductors tend to pick up a small positive charge while N-type ones have a negative charge. Typically, the semiconducting material is riddled with impurities that make them more susceptible to donating or accepting electrons because crystals such as silicon or germanium do not usually allow electrons to move freely from atom to atom. It’s all very similar to how one of the battery’s electrodes has a negative voltage with respect to the other, but applied in a different context.

It’s the P-N junction where electrons are free to cross from one side to the other, but not in the opposite direction. Imagine a hill — electrons can easily go down the hill (to the N side), but can’t climb it (to the P side).

Each photon with enough energy will normally free exactly one electron, causing a ‘hole’ to form. The electric field will then cause the electron to migrate to the N side and the hole to the P side.

This happens when an electron is lifted up to an excited state by consuming energy received from the incoming light. Were it not for a junction-forming material, the free electrons would have eventually fallen back to the ground state.  And because the electrons are only allowed to flow in a single direction — from N-type to P-type — the photovoltaic effect produces a direct current.  This current, together with the cell’s voltage, defines the power (or wattage) that the solar cell can produce.

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The future

According to the International Energy Association (IEA), photovoltaic solar power grew faster than any other energy source in 2016. The organization estimates that more solar capacity will be added in the next four years than any other type of renewable energy, including wind and hydropower.

Much of this demand comes from China, which is expected to add 40% of the world’s new solar panels between now and 2022, despite having already surpassed its solar power target for 2020. Along with developments in other countries, such as India, Japan, and the US, the IEA estimates that by 2022 the world will triple its PV cumulative capacity to 880 GW. This is equivalent to half the global capacity in coal power, which has taken 80 years to build. This also means that in the next five years, about 70,000 new solar panels will be installed every hour – enough to cover 1,000 soccer pitches every day.

Credit: Imperial College London.

Bacteria-printed solar cells produce electricity during both day and night

Credit: Imperial College London.

Credit: Imperial College London.

British researchers have achieved a breakthrough in biophotovoltaics (BPV) by printing electronic circuits and bacteria at the same time. The biological solar panel produce electricity both day and night, unlike conventional photovoltaic cells that are entirely reliant on sunshine. The entire device is also biodegradable, making it ideal for a disposable solar cell or battery that can decompose in composts or gardens.

“Cheap, accessible, environmentally friendly, biodegradable batteries without any heavy metals and plastics – this is what we and our environment really need but dont have just yet, and our work has shown that it is possible to have that,” said Marin Sawa from Imperial College London.

The living solar cells

Cyanobacteria are crucial organisms for all of the planet’s inhabitants, including us. They are photosynthetic organisms that have been living on Earth for billions of years. Up until 2.45 billion years ago, organisms had to rely on sulfate for their energy needs. But during a period known as Great Oxidation Event, for the first time, oxygen became a major component of the Earth’s atmosphere, indicating that cyanobacteria had taken over using sunshine, water and carbon dioxide to produce carbohydrates and oxygen.

Sawa and colleagues have now shown how cyanobacteria could potentially be used as an ink and printed from a common inkjet printer onto electrically conductive carbon nanotubes. These nanotubes were again inkjet printed on a piece of paper to etch precise patterns. The bacteria survived the ordeal and continued to supply electricity continuously for 100 hours during both light and dark cycles, as reported in the journal Nature Communications.

The bio-solar panel could resemble wallpaper (pictured), but is in fact an environmental sensor for monitoring air quality in the home. Credit: Imperial College London.

The bio-solar panel looks like wallpaper. Credit: Imperial College London.

However, the power they produce isn’t impressive — nine connected cells are capable of powering a digital clock or generating flashes of LED light. But that may be more than enough for some applications such as disposable environmental sensors disguised as wallpaper or paper-based sensors for monitoring patients with diabetes.

The field of biophotovoltaics, which employs cyanobacteria or algae that convert light into electricity, hasn’t really taken off. Cost, low power output, and short lifespan have all been challenges preventing the technology from scaling to an industrial level. British researchers, however, claim that their off-the-shelf inkjet printing method demonstrates the potential for scaling up the technology.

“Paper-based BPVs are not meant to replace conventional solar cell technology for large-scale power production, but instead, could be used to construct power supplies that are both disposable and biodegradable. Their low power output means they are more suited to devices and applications that require a small and finite amount of energy, such as environmental sensing and biosensors,” said Dr Andrea Fantuzzi, a co-author of the study from Department of Life Sciences at Imperial College London. \

The current paper-based BPV unit is palm-sized. The next step will see the team scale up their proof-of-concept to A4 size to determine the electrical output on a larger scale, as well as more powerful, long-lasting and robust.


(C) Land Art Generator Initiative

How much land California needs to cover with solar panels to become 100% fossil fuel-free

(C) Land Art Generator Initiative

(C) Land Art Generator Initiative

The men and women behind the Land Art Generator Initiative (LAGI), a yearly competition which awards the most innovative but artful sustainable designs, just illustrated how much land we’d need to cover in California to power the sunny state with 100% renewable energy.

We knew that you’d need to a boat load of solar panels and wind turbines to turn California into a carbon-free state, but now we finally have a visual rundown.

“Starting in 2009 with theSurface Area Required to Power the World with Solar, we have been making the case that the renewable energy transition, while a huge undertaking, is not any more ambitious in scale than previous human endeavors, and that the footprint on our environment can be designed to be in harmony with nature and provide a unique benefit to human culture,” the authors of the infographic wrote on their blog.

According to research, the land use required to power California with 100% renewable energy (all electricity, fuel and heat) is:

  • 1,184 km^2 solar electricity
  • 1,184 km^2 solar fuels
  • 987 km^2 wind power
  • 592 km^2 Wave, tidal, run-of-the-river

That sounds like a lot to most people but this is 2016. By now, humans have completed immense infrastructure works which can be incredibly complex. In fact, the authors of the infographic cite a previously published MIT study that estimated the land area required to satisfy 100% of U.S. energy demand, not just Cali, in 2050. According to the study, 100% renewable energy from solar requires half the land used for cropland currently devoted to growing corn for ethanol production. This same land area is less than the total area occupied by major roads in the nation or, more revealing, less than the area disturbed by surface mining for coal.

In the end, we might not even need to displace that much land for renewable energy. Another study found American rooftops provide enough surface area for solar panels to provide 60% of the nation’s projected electricity needs in 2050.

“Recognizing the unprecedented global threat of human induced climate change, we do not have the luxury of acting any less vigorously than California on a global scale, and in fact, that may not even be fast enough. Don’t ask how much it will cost because that is the wrong question. What will be the cost to the children born in 2016 if we do not act now? The technology exists to begin today, and the economic stimulus effect of a WPA-scale regenerative infrastructure project for the 21st century will bestow positive benefits for generations.”

“Let’s get to work!”

Six rectangular cells made from conductive polymer coated onto a fabric. Credit: Jeff Miller/UW-Madison

Solar cells woven into fabric could turn any tent, curtain or clothes into a solar panel

Six rectangular cells made from conductive polymer coated onto a fabric. Credit: Jeff Miller/UW-Madison

Six rectangular cells made from conductive polymer coated onto a fabric. Credit: Jeff Miller/UW-Madison

Marianne Fairbanks is a fabric designer who in 2010 briefly founded a company called Noon Solar that specialized in manufacturing solar-charged handbags. Not only would the handbags looked fashionable, but they would also generate electricity — enough to power a portable battery or mobile phone. Though the idea caught on for a while, but poor business eventually forced Fairbanks to seek other projects. The experience working at Noon Solar proved to be invaluable, though.

Connecting the dots

She eventually joined the University of Wisconsin-Madison as a professor at the school of human ecology, where Fairbanks would go on to meet Trisha Andrew, an assistant professor of organic chemistry.

Andrew had been experimenting at the time with an organic dye-based solar cell on paper, which definitely got Fairbanks excited. The two would eventually go on to collaborate and use their complementary skills to design an innovative solar harnessing unit — one you can wear on your clothes. Correction, one that makes up your clothes.

“The way that today’s wearable electronics are created is a simple process of packaging,” says Andrew. “A Fitbit or an Apple watch—they all have a PCB [printed circuit board], which holds the little electronic circuit. It allows you to ‘wear’ that device, but to me that’s not real wearable electronics. That’s only something that is patched onto another material.”

Textile solar cells aren’t exactly new. The first ones were made fifteen years ago, but what the two researchers at UWM claim their product is superior in terms of breathability, strength, and density.

Their solar cells are made up of one layer of fabric, which theoretically can be just about any material, and four coats of different polymers. The first coat is called Poly(3,4-ethylenedioxythiophene), or “PEDOT”, which works to increase the fabric’s conductivity. The other three are semiconducting dyes that act like light absorbers for the cell. To evenly distribute their coatings, the researchers used Chemical Vapor Deposition (CVD).

Various fabrics were tested for the substrate from silk to wool to nylon. Some would absorb sunlight and keep it there as heat. Other fabrics dispensed the heat, but conducted electrons.

“The conductivity of the PEDOT was completely determined by the underlying textiles,” adds Andrew. “If we had a porous textile, we got conductivity higher than the copper. If we had a very fuzzy textile, like fuzzy cotton jersey or wool felt, or very tightly woven textiles, then the conductivity of the PEDOT was really bad.”

The first commercial item the duo completed so far is a glove made from pineapple fiber, which is very conductive and absorbs heat, and cotton, which traps heat between the layers.


Andrew (left) and Fairbanks (right). Credit: Jeff Miller/UW-Madison

What they’re currently working on now sounds more interesting, though. Andrew and Fairbanks are experimenting with coating each individual textile fiber with PEDOT so they can weave them and form a working circuit. The completed fabric then works like a triboelectric generator which translates mechanical motion into electricity. Various 10-by-10-inch swatches have been demoed, the most efficient of which can generate 400 milliwatts of power.

“If you actually made a standard curtain for a house, something 4-by-4-feet, then that is more than enough power to charge your smartphone,” says Andrew,

“I get really excited, because textiles are portable and lightweight,” says Fairbanks. “They could be deployed in the wilderness for a hunter or in the field for medical or military applications in a way that big clunky solar panels never could be.”

The startup's solar panel is of the same size and can be as easily installed as any other typical residential-grade panel. Credit: EPFL/Alain Herzog

Swiss startup demoes residential solar panels twice as efficient than what the market has to offer

The startup's solar panel is of the same size and can be as easily installed as any other typical residential-grade panel. Credit: EPFL/Alain Herzog

The startup’s solar panel is of typical size and can be as easily installed as any other typical residential-grade panel. Credit: EPFL/Alain Herzog

Solar is growing exponentially fast all around the world. But while prices per kW-hour drop year after year, the same can’t be said about solar efficiency — here, progress is incremental. A Swiss startup backed by the prestigious Swiss Federal Institute of Technology in Lausanne (EPFL) might change all that by helping the industry take a big leap, instead of small steps. Their solar panels are about twice as efficient as most residential solar panels, but only marginally more expensive.

A new ray of hope for the solar industry

The most efficient solar cells were demonstrated by researchers at Soitec, France in December 2014. Their multi-junction concentrator solar cell can harness 46% of the sunlight’s energy into electricity. These sort of cells, however, are extremely expensive and only make economic sense for a narrow range of applications, like satellites in space or utility-scale solar power plants. Reaching this sort of efficiency for residential applications, like rooftop solar, has proven far more challenging.

In its labs based in EPFL’s Innovation Park, Insolight showed that it is possible to harness 36.4% of the sun’s incoming rays using a novel design developed in-house. Other solutions currently traded in the market can only offer 18 to 20 percent efficiency.

Their panels are made out of two main sub-systems. The first part is made of a very thin optical structure comprised of millimetric lenses which act as a small network of magnifiers. The incoming light is thus amplified and concentrated onto a ‘super solar cell’, which comprises the second system. This cell is a multi-junction one consisting of multiple layers that each act to capture a particular band of energy from sunlight.

The lenses used to concentrate solar power onto the cell. Credit: Credit: EPFL/Alain Herzog

The lenses used to concentrate solar power onto the panel’s cell. Credit: Credit: EPFL/Alain Herzog

Multi-junction cells can be prohibitively expensive, but Insolight made their panels in such a way that only a very small super solar cell is used. Even so, when the light is concentrated onto the tiny cell, it generates twice the electricity for the same surface area as the typical solar panels you can buy anywhere today. An important component that helped the Swiss researchers gain this remarkable performance is a proprietary tracking system that can direct 100% of the sun’s rays into the cell no matter the angle of incidence.

“All the components were designed from the start to be easily mass produced,” says Mathieu Ackermann, the company’s CTO. “Working in industry gave us what we needed to reach our goal, which was to develop solar panels that could be rapidly brought to market at a competitive price.”

The results were validated by an independent lab in Germany, part of the Fraunhofer Institute group. But transitioning this performance from the lab to the real world is a whole different matter. The founders are optimistic, though, and say that even if their design falls short of a couple points it will still be better than what’s currently being offered.

“The price of solar panels has dropped sharply in recent years, but not enough to produce electricity at a competitive cost,” Ackermann  says.

“For residential systems, solar panels accounted for less than 20% of total installation costs in the United States in 2015. Even if the solar panels were free, this would not always offset the system’s cost. Currently, most of the margin earned by solar energy developers comes from subsidies. Yet these subsidies are declining.”

This is where Insolight hopes to step in. It remains to be seen whether the young startup can scale production and deliver on its promises. There’s no word for now regarding the wholesale price.

“Insolight has designed a highly innovative system, and these initial prototypes show an impressive yield in external assessments,” says Christophe Ballif, Director of EPFL’s Photovoltaics Laboratory. “They now need to test the limits of their concept, show how a commercial-sized system can perform, and prove the product’s economic potential.”

Elon Musk’s company revealed plans for a roof made of solar panels

Elon Musk has shown plenty of times in the past that he’s not afraid to go a bit outside the box – or even a bit more. His latest stint came up during a meeting with SolarCity’s investors, where he announced plans to make a solar roof. No, not a roof with solar panels, a roof made of solar panels. According to him, the roof “looks way better” and “lasts far longer than a normal roof.”

SolarCity wants to reinvent the concept of a solar roof, and design a roof made from solar panels, not fitted with solar panels, as seen above. Image in Creative Commons via Wikipedia.

The roof would be integrated with Tesla’s house battery system, allowing the roof to store energy for a longer time. This kind of integration is why Musk has been pushing for a merger between Tesla and SolarCity in the first place. New panel installations have been declining for SolarCity and many other companies in the US, so they hope to target a new class of consumers altogether: people who want to install a new roof.

“There is a huge market segment that is currently inaccessible to SolarCity,” Musk said. The company says there are 5 million roof replacements in the US alone every year.

Of course, a meeting with investors isn’t exactly a public announcement, but that doesn’t make it any less exciting. There was not much insight as to how the system would work, but Musk said that users will be able to customize their own design. According to Engadget, SolarCity’s Peter Rive says the company only started talking about roofing “a couple of weeks ago,” but it’s also going to be a key part of a ramp-up in production around the second quarter of 2017.


Ikea resumes selling solar panels in the UK

Ikea made it much easier for British people to green their homes – for a while. Then, after the government reduced subsidies for renewable energy, the company quietly stopped selling the panels, and now they’ve resumed them again.

Why Ikea selling solar panels matters

Image via Ikea.

When Ikea starts selling something, it’s safe to say it’s become mainstream. Initially, the company said that the solar panels will be available in stores in Glasgow, Birmingham, and Lakeside, as well as online. They offer two options: blue solar panels (which are cheaper) and black solar panels (which are more expensive, but offer more energy).

According to Solarcentury  (Ikea’s current partner in this endeavor) the blue solar panels cost about £4,875, or $7,057, while the black solar panels will run about £5,150, or about $7,455. That’s quite a hefty price, but the average annual electricity bill for a house in the UK is £1,000, or $1,500 so you could recover the investment in 10 years, which is acceptable from a business point of view, though not fantastic. For larger houses,  that investment could be recovered 50% faster. But the main incentive would be greening up your house, and with Ikea involved, the whole process became much easier and accessible.

IKEA UK and Ireland’s Head of Sustainability Joanna Yarrow said:

“At IKEA we believe that renewable energy is undoubtedly the power of the future. We’re already using solar power across our operations, and it’s exciting to be able to help households tap into this wonderful source of clean energy.”

Why Ikea stopped selling solar panels…

There’s a specific “bla-bla” in the quote above, as Ikea was quick to trumpet its green credentials, but withdrew their project after government cuts to green subsidies. The UK made a mockery of their sustainable ambitions when they slashed subsidies by 64 percent, greatly affecting Ikea’s prospects of selling solar panels.

The company’s move was understandable, but their silence wasn’t. They touted the start of the solar affair so much, but were quite quiet when it all went down crashing.

Their first contract was with a Chinese company called Hanergy, but they cancelled the deal and didn’t renew it. No details were given, and Ikea’s foray into renewable energy seemed to come to an end.

… and then started selling them again

Quote example. Image via Solarcity.

Ikea now partnered with a new company, Solarcentury – and this time, it seems like the panels are here to stay. Customers in Glasgow, Birmingham, and Lakeside can check them online, but everyone else can check out the prices at the website of Solarcentury.

They say that even with the current events, a third of all British homeowners are still considering installing solar panels.

“Despite the challenging UK renewable energy policy situation, we want to turn solar into an essential part of any home and believe our new ‘Solar Shops’ will be a major milestone in making this happen,” said Joanna Yarrow, IKEA’s UK and Ireland head of sustainability.

It will be interesting to see what impact this move has, and whether it will make a big difference or not. But it’s becoming clearer and clearer that renewable energy is starting to enter our lives more and more – even with a lack of government support.

San Francisco just became the first big US city to require solar panels on new buildings

The San Francisco Board of Supervisors unanimously passed legislation that obligates all new constructions shorter than 10 floors to install solar panels or solar water heaters on top of both new residential and commercial buildings.

“By increasing our use of solar power, San Francisco is once again leading the nation in the fight against climate change and the reduction of our reliance on fossil fuels,” said Supervisor Scott Wiener, who put forth the legislation, in a statement. “Activating underutilized roof space is a smart and efficient way to promote the use of solar energy and improve our environment.”

“Painted Ladies” near Alamo Square, San Francisco, California. Photo by King of Hearts.

San Francisco is famous for its foggy days. As it’s surrounded by water on three sides, inland heat tends to draw cool ocean air across the city, shrouding it in fog. But contrary to popular belief, solar panels do work in the fog, because some of the light can reach the panels. There’s even a small advantage, as the fog keeps panels relatively cool, which improves their efficiency. Overall, SF compares well with other cities in the sunny state of California, and it’s definitely one of the cities where solar panels are worth installing.

Renewable energy has developed significantly in California, with the state being required to obtain at least 33% of electricity from renewable sources other than large hydro. In 2014, solar provided 4.2% of the state’s energy, while wind chipped in at 8.1% and geothermal came in with 6.1%, for a total that’s under 20%. But with measures like these, California’s green energy will certainly develop.

The new rules don’t go into effect until January 1, 2017. The legislators also introduced a backup possibility for people who don’t want solar panels on their buildings: installing a garden or green area on top of the building, instead of the solar array.

Nine bacterial solar cells that combined generate 5.59 microwatts. Image: Seokheun "Sean" Choi

You’ve heard all about solar cells, but what about bacterial solar cells?

On the desk of  Seokheun “Sean” Choi sits a 3×3 array that at first glance looks like a lemon squeezer. It is, in fact, a solar panel but not like any you’ve seen or heard about before. Instead of using semiconductors like silicon crystals to convert sunlight into electricity, the array employs a complex system that nurtures cyanobacteria — beings whose metabolism create free electrons which can be harnessed.

Nine bacterial solar cells that combined generate 5.59 microwatts. Image: Seokheun "Sean" Choi

Nine bacterial solar cells that combined generate 5.59 microwatts. Image: Seokheun “Sean” Choi

Choi and colleagues at Binghamton University have been working on the bacteria solar cell for years now. Last year they significantly improved their design by changing the materials for the anodes and cathodes. They also used a microfluidic system chamber that houses and feeds the bacteria, instead of a dual-chamber reactor. Now, they’ve shown how to stack each cell into an array, proving the design is scalable.

Cyanobacteria, being photosynthetic organisms, use the sun’s energy, H2O and CO2 to synthesize their energy storage components, i.e. carbohydrates, lipids and proteins. Some researchers have proposed that it may be feasible to use cyanobacteria to make biofuels and even hydrogen fuel  by the reversible activity of hydrogenase. The Binghamton University researchers, however, are tapping directly into the photocurrent generated by the bacteria themselves.

“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 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.

“This research could also enable crucial understanding of the photosynthetic extracellular electron transfer processes in a smaller group of microorganisms with excellent control over the microenvironment, thereby enabling a versatile platform for fundamental bio-solar cell studies,” said Choi.

I know you like numbers, so let’s look at some figures. A typical solar panel configuration of, say, 6×10 cells generates roughly 200 watts of electrical power. The same number of bacterial solar cells generates 0.00003726 watts, researchers report in the journal Sensors and Actuators B: Chemical. Alright, that was disappointing but this is still 1) experimental research and 2) bacterial solar cells aren’t meant to compete with traditional solar cells. It’s also worth noting that the power output was measured at 1.28 V operating voltage under a 200 kΩ external resistor, so there’s room for plenty of juice to power small devices.

The findings open the door for more research into how cyanobacteria could be used to power remote devices, like wireless sensors. Other than that, it’s pretty amazing to see other creatures besides hamsters turning a wheel generate raw electricity — and the cyanobacteria don’t seem to mind at all.

“It is time for breakthroughs that can maximize power-generating capabilities/energy efficiency/sustainability,” Choi said. “The metabolic pathways of cyanobacteria or algae are only partially understood, and their significantly low power density and low energy efficiency make them unsuitable for practical applications. There is a need for additional basic research to clarify bacterial metabolism and energy production potential for bio-solar applications.”



rooftop solar

Rooftop solar could meet 39% of U.S. electricity needs

The National Renewable Energy Laboratory (NREL) estimates that rooftop solar has the potential to cover 39 percent of the country’s electricity needs. Sunny states like California, Texas and Florida topped the list of states where rooftop solar could generate the most energy.

rooftop solar

Image: Pixabay

In 2008, the agency estimated the country could meet 21 percent of its electricity demand using rooftop solar. Then, scientists reckoned its potential was 800 terawatt-hours of electricity per year. Eight years later, this estimate jumped almost two fold to 1,432 terawatt-hours of annual rooftop solar generation. Today, commercial solar panels are vastly superior in terms of efficiency. There are also more buildings.

California is the clear leader, having the potential to generate 74 percent of its electricity from rooftop panels alone. Percentage wise, the next states in line are surprisingly the New England states which don’t get much sunshine, but use little electricity to begin with. In absolute numbers, topping the list are, again, California, Texas, Florida and New York — in this order.

 Potential rooftop PV annual generation from all buildings as a percentage of each state’s total electricity sales in 2013. Image: NREL.

Potential rooftop PV annual generation from all buildings as a percentage of each
state’s total electricity sales in 2013. Image: NREL.

The researchers made their estimates by analyzing LIDAR data captured by aircraft for 128 cities from around the country. LIDAR stands for LIght Detection And Ranging — a technology that uses lasers to measure distance highly accurately. Correlating LIDAR with known solar energy potential for every square meter, the researchers could estimate how much energy solar panels placed on the rooftops of buildings and homes could generate. The results where then extrapolated for the rest of the country. In the previous 2008 analysis LIDAR wasn’t used, which is one of the reasons estimates are higher now.

“Although only 26% of the total rooftop area on small buildings (those with a footprint smaller than 5,000 ft2 ) is suitable for PV deployment, the sheer number of buildings in this class gives small buildings the greatest technical potential. Small building rooftops could accommodate 731 GW of PV capacity and generate 926 TWh/year of PV energy, which represents approximately 65% of rooftop PV’s total technical potential. Medium and large buildings have a total installed capacity potential of 386 GW and energy generation potential of 506 TWh/year, which represents approximately 35% of the total technical potential of rooftop PV,” the NREL researchers noted in their report.

This all sounds great news for renewable energy enthusiasts. It sends a clear signal that the potential is there. Of course, 39 percent solar only from rooftops is huge. Think of it as something close to the absolute limit — so half is realistically feasible. It’s still a lot more than the 2.4 percent California generated from rooftop solar in 2014, for instance.


U.S. small town rejects solar project out of fear it would ‘suck up all the energy from the sun’


In news worthy of satire, the town council of  Woodland, North Carolina rejected a proposal that would allow the Strata Solar Company to build a solar farm off Highway 258. Furthermore a moratorium on solar farms has been instituted that will see three previously accepted solar farm projects suspended until further notice. The decision reflected the fears and angst expressed by Woodland residents that such solar installation would harm the community, its economy and biodiversity. Bobby Mann, present at the meeting where the decision was made, said he was afraid  Woodland would become a ghost town because of the solar farms. According to the Roanoke-Chowan News Herald, Mann said the solar farm “would suck up all the energy from the sun and businesses would not come to Woodland.”

In the same meeting, Jane Mann, a retired science teacher, said that the local, beautiful plants depend on photosynthesis to survive. As such, the solar panels would keep the plants from growing. She said she has observed areas near solar panels where the plants are brown and dead because they did not get enough sunlight. Later, she said she found a link between a high number of cancer deaths in the area and solar panels. She added that ‘no one could tell her that solar panels didn’t cause cancer.’

“I want to know what’s going to happen,” she said. “I want information. Enough is enough. I don’t see the profit for the town.

“People come with hidden agendas,” she said. “Until we can find if anything is going to damage this community, we shouldn’t sign any paper.”

Good thing she’s retired.

Other residents were much more moderate, saying the town is surrounded by solar farms and is no longer worth its value because of those facilities. The only funding the town would get is about $7,000 per year to train the fire department in case something goes wrong. This is actually a legitimate concern, and the solar companies involved in Woodland should have provided better incentives to the local community, like cheaper electricity.

Other than that, most objections are hilarious. Solar panels don’t suck up the sun, nor cause cancer. What causes cancer is coal-fired plants. The only sunlight that gets ‘sucked away’ is the one that hits the panels directly. Yes, plants wither and may die if these grow right beneath the solar panels. As for jobs, I apologize if I might hurt anyone’s feelings but it seems the reason why there isn’t work anymore in this town is because businesses may be reluctant to join such a close-minded community.

120-country Solar Alliance announced at COP21 in Paris

A possible game changer – 120 country alliance spearheaded by India and supported by France has been announced, with the purpose of promoting solar energy in developing countries.

Solar panels in an off-grid Indian village. Image via Wikipedia.

Many developing countries enjoy sun-rich areas, but they lack the technology and financial capabilities to make full use of that potential. With that in mind, India’s prime minister Narendra Modi said that the future of these countries depends on bold initiatives and alternatives to fossil fuel energy.

“Solar technology is evolving, costs are coming down and grid connectivity is improving,” he said. “The dream of universal access to clean energy is becoming more real. This will be the foundation of the new economy of the new century.”

It’s easy to get behind such an initiative – even only technological exchange could dramatically improve renewable energy availability, with massive social and economic impacts – but a full fledged alliance, with technological, financial and policy support seems destined to shine.

France’s president, François Hollande praised the initiative, raising the stakes even more and saying that this type of deal could pave the way for a global climate agreement and calling it an example of “climate justice”.

“What we are putting in place is an avant garde of countries that believe in renewable energies,” he told a press conference in Paris. “What we are showing here is an illustration of the future Paris accord, as this initiative gives meaning to sharing technology and mobilizing financial resources in an example of what we wish to do in the course of the climate conference.”

According to the presentation documents, the alliance could set in motion funds of up to $1000 billion (a thousand billion, yes), but that sounds like an overly optimistic figure. So far, India has is investing an initial $30m (£20m) in setting up the alliance’s headquarters and funding from international agencies and membership fees will raise the sum to $400m – that’s still a long way to go to a billion, let alone a thousand, but this is definitely a step in the right direction.

This shouldn’t be mistaken for the Breakthrough Energy Coalition which is basically an investment fund for clean energy projects launched by Bill Gates and Facebook founder Mark Zuckerberg.

We’ll keep you posted as developments continue to unfold.

Silicon pillars emerge from nanosize holes in a thin gold film. The pillars funnel 97 percent of incoming light to a silicon substrate, a technology that could significantly boost the performance of conventional solar cells. Credit: Vijay Narasimhan, Stanford University

Finally, the metal wiring in solar cells might stop reflecting light. One up solar efficiency

There’s an inherent flaw in solar cells: the metal wiring that’s quintessential to harnessing the electrons reflects the incoming light, acting like a mirror. Now, must people would brush off this issue and leave it like that. It’s a necessary trade off. But a team at Stanford University devised an elegant chemical technique that basically hides the wiring with silicon, away from the light while preserving energy harnessing. Metal wires cover 5 to 10 percent of a solar cell’s surface. Now, in the same area more light can be absorbed, hence more electricity generated which jumps the efficiency. Of course, this also means cheaper solar panels — if only the chemical technique is covered by the recurring costs of increased efficiency.

Silicon pillars emerge from nanosize holes in a thin gold film. The pillars funnel 97 percent of incoming light to a silicon substrate, a technology that could significantly boost the performance of conventional solar cells. Credit: Vijay Narasimhan, Stanford University

Silicon pillars emerge from nanosize holes in a thin gold film. The pillars funnel 97 percent of incoming light to a silicon substrate, a technology that could significantly boost the performance of conventional solar cells. Credit: Vijay Narasimhan, Stanford University

“Using nanotechnology, we have developed a novel way to make the upper metal contact nearly invisible to incoming light,” said study lead author Vijay Narasimhan, who conducted the work as a at Stanford. “Our new technique could significantly improve the efficiency and thereby lower the cost of solar cells.”

The researchers modeled a typical solar cell with a thin film of gold 16-nanometer-thick atop a flat sheet of silicon. Tiny, itsy bitsy holes were perforated on the whole surface, but to the naked eye the gold layered object still looked like a shiny mirror. Analysis showed the hole-ridden gold film covered 65% of the silicon’s surface, reflecting 50% of the incoming light. So far so good. That was predictable.


A typical solar cell – wiring is both on top and back. 

Narasimhan and colleagues then immersed the object  in a solution of hydrofluoric acid and hydrogen peroxide. What happened next was the silicon started popping up through the holes, like pillars. These grew up to 330 nanometers in height, transforming the once golden surface into a dark red. That alone indicated the surface wasn’t reflective anymore. Narasimhan compares the silicon pillars to a colander in your kitchen sink

“When you turn on the faucet, not all of the water makes it through the holes in the colander, ” he said. “But if you were to put a tiny funnel on top of each hole, most of the water would flow straight through with no problem. That’s essentially what our structure does: The nanopillars act as funnels that capture light and guide it into the silicon substrate through the holes in the metal grid.”

The metal contacts still work great. Through trial and error, the Stanford researchers eventually reached an optimal design where nearly two-thirds of the surface can be covered with metal, yet the reflection loss is only 3 percent. This not only means that manufacturers can hide metal contacts – they can include more of it since it helps with efficiency! The researchers estimate a conventional 20% solar panel can up its efficiency to 22%, a huge gain. Multiply that by millions of solar panels and you’ve got a massive energy gain and cost reduction.

What about the gold? Yes, gold is expensive but Narasimhan says the technique works with  silver, platinum, nickel and other metals. “We call them covert contacts, because the metal hides in the shadows of the silicon nanopillars,” co-author Ruby Lai. said. “It doesn’t matter what type of metal you put in there. It will be nearly invisible to incoming light.”

“With most optoelectronic devices, you typically build the semiconductor and the contacts separately,” said Cui, co-director of the Department of Energy’s Bay Area Photovoltaic Consortium (BAPVC). “Our results suggest a new paradigm where these components are designed and fabricated together to create a high-performance interface.”

A model gold sheet is, of course, different from an actual solar cell. Looking forward to seeing this work applied to an actual working cell.

Reference: Vijay K. Narasimhan et al. Hybrid Metal–Semiconductor Nanostructure for Ultrahigh Optical Absorption and Low Electrical Resistance at Optoelectronic Interfaces, ACS Nano (2015). DOI: 10.1021/acsnano.5b04034

passive cooling system

A simple coating cools solar panels by reflecting the heat into outer space

No kidding, Stanford researchers actually showed it’s possible to cool solar panels by applying a special coating that reflects some of the heat back into space. The coating, called a  photonic crystal cooling system, is transparent. This allows the light to reach the PV cells so these can generate energy, but – crucially – some of the heat is reflected back in space. It’s so good that the researchers showed their PV panels can even stay below ambient temperature, which is incredible by itself. If you know a thing or two about solar panels, then you’ll remember their efficiency is directly related to temperature. The cooler a panel is, the more of the sun’s energy it can convert into electricity. And we’re talking about a mere coating, which shouldn’t be too difficult to scale. Bit by bit, you if you multiply the extra efficiency by millions of panels you end up with a huge useful energy gain. This may be a game changer.

passive cooling system

Illustration: Nicolle R. Fuller/Sayo-Art

Previously, the same team at Stanford made headlines after their turned cooling upside down. A radiator is the most basic cooling part and implies transferring the heat out of your system, to the ambient. Take your refrigerator, for instance. It uses energy to cool food inside, but it also release heat into the room its kept, which is then absorbed and released outside and so on. Same with a car, where a simple grilled metal part stays in contact with both the engine and the air to move away the heat. What’s innovative about the new solution developed at Stanford, however, is that heat is thrown out of the planetary system itself. The heat literally ends up in outer space. When they first showcased their passive cooling prototype, the researchers reported they could lower the temperature of anything that it’s placed on by up to five degrees Celsius by absorbing heat, then re-emitting it at an infrared frequency which can pass through the atmosphere. This way, you use the Universe as a heat sink. Brilliant.

The silica coating over a the Stanford logo.

The researchers were interested, however, in making this work for solar panels, but their initial prototype also reflected 97% of the sun’s rays which is obviously impractical for solar power generation. Now, they’ve found a workaround: they’ve designed a thin film of pattern silica which is transparent to visible light, which makes up most of the energy that solar panels use, but essentially absorbs infrared light (heat). In the paper published in PNAS, the researchers report cooling a solar panel layered with such a film by up to 13 degrees Celsius, which is huge! In terms of efficiency, this translates in increased performance of at least 1% in absolute efficiency.

All matter dissipates heat under the form of far infrared waves, be it rocks, trees or cells. Humans, at normal body temperature, radiate most strongly in the infrared at a wavelength of about 10 microns, which can be viewed with special thermal vision goggles. Heat is dissipated in wavelengths between 6 and 30 micrometers, but air molecules can only absorb, and thus emit, heat in the lower and upper range. Anything that’s between 8 and 13 micrometers passes right through the air and into space. So the trick lies in building a surface that reflects lower and upper ranges, while radiating microwaves that can’t be absorbed by air. The polished fused silica coating is very thin, only 500-μm thick, and patterned with of 6-μm wide, 10-μm deep holes. In the lab, it was etched using photographically which doesn’t sound too practical for large scale but other manufacturing methods could be used.

Artist impression of Solar Sunflowers next to the plant variety. Image: Airlight Energy

‘Solar suflower’ array generates 60 times more power than a typical solar panel

An innovative concentrated solar power design called the “Solar Sunflower” was recently demonstrated by Swiss researchers at Airlight Energy and IBM Research in Zurich. The energy generator concentrates 5,000 suns onto a semiconductor chip to generate both electricity and heat at 80% efficiency. This meas roughly 60 times more power generated over the same surface area than a typical roof-mounted solar panel – granted, the parabolic dish array, which is quite big, isn’t included. The electricity and hot water generated by one single Solar Sunflower can meet the needs of a couple homes.

Artist impression of Solar Sunflowers next to the plant variety. Image: Airlight Energy

Artist impression of Solar Sunflowers next to the plant variety. Image: Airlight Energy

Those familiar with solar tech might not be all that excited by now. It’s true concentrated solar and thermal power isn’t all that novel anymore. The Ivanpah Solar Electric Generating System located in California is the largest concentrating solar power array in the world. The facility has the capacity to generate 392 megawatts (MW) of clean electricity — enough to power 94,400 average American homes. The design is considerably different: a field of mirrors called heliostats rack the sun and focus sunlight onto boilers that sit atop 459-foot tall towers. This heats water that produces steam which turns turbines to produce electricity. Add this as a pro to our list of advantages and disadvantages to solar.

solar sunflower

What makes the Solar Sunflower particularly promising is its remarkable efficiency, which to me is unheard of (someone please correct me if I’m wrong) because it leverages the energy both as electricity and heat. The design work is also particularly impressive. For one, the structure is made out of concrete instead of steel like is the case for most concentrating parabolic mirror arrays. The carbon fiber enforced concrete is just as reliable mechanically as steel, but at one fifth of the cost. Then, the mirrors themselves are not bulky, heavy and expensive as you might think at first face. Instead, the 36 mirrors that cover one parabolic array are simply 0.2 millimeter thick recyclable plastic foils with a silver coating, not all that different from the wrapper chocolate is packaged in – another enlightening fact about solar energy.

solar sunflower

Together, the array concentrates the power of 5,000 suns on a surface area, which is where the greatest challenge lies. At this kind of concentration, the mirror array can melt a lump of iron in under a minute (over 1538°C). To keep the multi-junction semiconductor chips from failing, Airlight Energy partnered with IBM Research and used their patented liquid cooling technology – typically used to cool supercomputer – to cool the Solar Sunflower.

This isn’t your typical liquid cooling tech. Usually, water picks up heat from a system, then goes through a radiator to dissipate the energy in the atmosphere as wasted heat. The IBM cooling tech uses all that hot water in a more efficient manner since it transfers it to residences and businesses to heat them. For instance, the Aquasar a supercomputer at ETH in Zurich transfers hot water to heat university buildings. There’s more to it, of course. You don’t see a bulky radiator strapped to heat generating transistors. Instead, thousands of tiny microfluidic channels bring the water in contact with select surface areas, maybe just a few microns in size. In the case of the Solar Sunflower, the microfluidic slices of silicon are stuck to the backside of the gallium-arsenide photovoltaic cells.

Ultimately, one Solar Sunflower produces 12kW of electricity and 21kW of thermal energy through water flowing at temperatures up to 90°C. This is enough energy to power a couple of homes, meaning you’d need lots and lots of these to make sense powering a community, for instance. This is where the trouble starts, in fact. There is no way these Sunflowers could be used on a extensive level since in terms of cost they’re not competitive with the plain silicon solar panels. Sure, they might look cool, but when it comes down to money these Sunflowers don’t stand a chance. Why make them then? For one, it’s a remarkable display of technology even though it can’t be scaled. Secondly, there’s always a niche. Airlight Energy says it will start delivering a couple of orders to early adopters in 2016, then ramp production at a larger scale in 2017. My hope is someone can find a way to spin this design and turn it into something cheaper. At least cheap enough so most of us can afford putting one in our backyards. Waaay cooler (and dangerous) than boring solar panels.

via Ars Technica