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Science

How Do Solar Panels & Solar Energy Work?

by Tina Casey August 22, 2017

Have you ever wondered how sunlight can travel 93 million miles from the Sun to the Earth, and still have enough oomph in reserve to burn your light bulbs? That, in a nutshell, is the miracle of solar energy. As for how solar panels work, that’s a little harder to fit in a nutshell but if you think of yourself as a kind of walking, talking vessel for solar energy, it’s a little easier to understand the science behind the miracle.

Solar Energy For People In A Hurry

To begin at the beginning, energy refers to the ability to do work. In other words, energy is not a person, place, or thing. Energy is the state of being at work.

Loosely speaking, “work” consists of movement, or at least the potential for movement. So, the thing at work — aka an energy carrier — can be anything at all — a star, or an elephant, or a rock, or you lying in bed at night and dreaming of solar energy.

At the other end of the size scale, the thing at work can be as small as a subatomic particle.

That brings us to the “solar” part of the solar energy equation.

Light is a unique phenomenon because it behaves like both a wave and a particle. Its wavelike behavior includes the ability to travel through space (at the speed of light, of course). The particle behavior — first described by Albert Einstein in 1905 — includes the ability to interact with another material — in other words, to work.

That’s common knowledge now but Einstein broke with generations of settled science when he proposed that electromagnetic waves (including visible light) consist of discrete units or “packets” of energy.

Btw, coinage of the word “photon” is credited to the physical chemist Gilbert Lewis, who first used it in 1926 to describe those packets of energy.

So, How Do Solar Panels Work?

If you caught that thing about light being able to interact with other materials, you’re on to something.

Think about the last time you got a sunburn, and it’s pretty clear that photons interact with material on earth.

Sunlight can also touch off a chain reaction deep within your body — for example, by setting Vitamin D production in motion.

So, yes, you are living proof that solar energy still packs a punch after its 93 million mile journey to Earth.

That brings us to solar panels.

In 1839, teenage French scientist Edmond Becquerel got the credit for being the first researcher to document that sunlight can interact with certain metals to generate an electrical charge.

That’s the essence of photovoltaic technology, aka solar cells and solar panels.

The first functioning solar collector on record was built by an employee of the Carnegie Steel Company, William J. Bailey. In 1908 Bailey developed a solar energy harvesting device consisting of copper coils and an insulated box.

That’s more or less the idea behind today’s generation of solar panels. The rest is basically a matter of finding the most efficient materials for converting sunlight to electricity.

In the 1940s, Russell Shoemaker Ohl of Bell Laboratories accidentally stumbled on the basic element of modern solar cells when he observed the effect of sunlight on a defective sample of silicon.

It took a while after that but Bell Labs is widely credited with introducing the first working silicon-based “solar battery” in 1954.

No, Really, How Do Solar Panels Work?

For light dinner conversation, that’s about all you need to know. Sunlight creates an electrical charge in certain materials, back in the middle of the last century researchers discovered that silicon does the trick, now pass the potatoes.

If you’re interested in the meat of the muscle, NASA offers this explanation:

“Photovoltaics is the direct conversion of light into electricity at the atomic level. Some materials exhibit a property known as the photoelectric effect that causes them to absorb photons of light and release electrons. When these free electrons are captured, an electric current results that can be used as electricity.”

Now go back to Ohl’s discovery, and you can see where things get a little more complicated.

The American Physical Society has a handy rundown of Ohl’s observation. Check it out for more detail, but for those of you on the go, it all boils down to the defect in the silicon sample.

The defect was a crack, which in effect formed a visible boundary. The boundary marked the difference between invisible (aka atomic level) properties on either side:

“This crack, which had probably formed when the sample was made, actually marked the boundary between regions containing different levels of impurities, so one side was positively doped and the other side negatively doped.”

When Ohl exposed the silicon to sunlight, a positive charge built up on one side of the crack, and a negative charge built up on the other. In other words, he accidentally created a solar cell with a basic p-n (positive-negative) junction.

The buildup of charges is what makes an electric field, and then it’s just a matter of getting that one last connection in place:

“When the cell is hooked up in a circuit, an incoming photon that hits the cell can then give an electron a kick and start current flowing.”

According to APS, the Ohl’s solar cell had a conversion efficiency of 1%.

If that doesn’t sound too impressive, it’s not — at least by today’s standards.

Conversion efficiency refers to the portion of sunlight that can be converted to electricity, and the latest crop of silicon solar cells tops 25% in the lab.

Onwards & Upwards For Solar Energy

For those of you interested in more history, the US Department of Energy has assembled a handy timeline that traces all the major steps that took us from 7th century BC ant-burners (no, really!) on up to silicon and other high-efficiency materials for solar panels.

Aside from carbon nanotubes, one of the most exciting developments in recent years is graphene, a form of carbon that comes in atom-thin sheets. Graphene was discovered by a pair of researchers in 2004 and it quickly became the “it” material of solar cell research.

Graphene developments of recent note include the use of bacteria to fabricate graphene sheets with desirable “wrinkles” to enhance efficiency, and a graphene-silicon “all-weather” hybrid cell capable of harvesting energy from rainwater as well as the sun.

Another promising photovoltaic material is perovskite, which refers to a class of synthetic crystalline materials based on the naturally occurring mineral perovskite.

Belgium’s IMEC, for example, just reported a conversion efficiency of 23.9% for a silicon-perovskite cell.

Thin film technology has also had an impact on the solar field in recent years.

“Thin film” refers to solar cells that are made by depositing layers of a solution containing microscopic particles of photovoltaic material.

Though generally not as efficient as their silicon cousins, thin-film solar cells have the advantage in other ways.

The layers can be coated on practically anything — glass, for example — so thin-film solar cells can be integrated with windows and other building elements.

They are also lightweight and flexible when layered on thin sheets of plastic and other materials, lending themselves to a range of applications unavailable to conventional solar cells.

That’s just a taste. We haven’t even gotten to the inverter thing or why tracking systems are a good idea, or other solar-related fields like passive solar and solar thermal — which includes devices that can range in size from the rooftop hot water heaters on up to massive concentrating solar power plants.

Researchers are also tinkering around with artificial systems that mimic the chemical reactions involved in photosynthesis, in order to pump out hydrogen fuel and other fuel products.

To catch up on all the latest solar news — solar energy, solar panels, and much more — take a scroll through the CleanTechnica solar archives.

Photo via National Renewable Energy Laboratory

August 22, 2017 0 comment

Science

Giant UFOs Are Stealing Solar Power From The Sun!

by Steve Hanley November 30, 2016

written by Steve Hanley

If you check your calendar today, you might be excused if you thought today is April Fool’s Day after reading this story. Almost as hard as the election of Donald Trump is to believe, this report from the lunatic fringe is even more difficult to give credence to. The UFO hunter known as Streetcap1 on YouTube is putting forth the theory that giant UFOs are draining solar energy from the sun.

Aare UFO's stealing power from the sun?

The proof, Streetcap1 says, is a line of “plasma” running from the sun to a strange object seen in a telescopic photo of the sun taken by NASA. “Is this a massive UFO feeding off sun energy?” he asked on his YouTube channel. “The fact that the UFO is a different color and shape to the rest of the connected line is what convinced me to upload this,” he explains. “I was not a great believer in this plasma sun energy theory, but this has got me thinking.”

UFO blogger Scott C Waring picked up on the video and said, “This UFO shot out of the sun yesterday but was seen by Streetcap1 of Youtube. The UFO may have been using the suns energy to fuel itself or to recharge in some way, but it’s leaving at high speed. Notice that the UFO is a glowing white, but the sun’s plasma is a yellow. This tells us the craft is made from a different material than the sun’s surface.”

Later, Mr Waring posted his own NASA image taken by the Solar and Heliospheric Observatory (SOHO), a spacecraft with telescopic camera sent to image the sun and beam back high detail images. He says it shows huge UFOs orbiting the sun. On his website ufosightingsdaily.com, a post entitled ‘Hundreds of Giant UFOs Orbiting Our Sun, NASA/SOHO Images Confirm’, Waring suggested the UFOs are as big as the Earth in some cases.

ufo-sun-738018

“Now please know,” he adds, “the UFOs in each photo are different because the sun is rotating, and there are a lot of moon size and earth size UFOs around our sun. Back about 10 years ago, two Russian scientists announced that they have found hundreds of UFOs orbiting Earth’s sun at any given moment in time. And that these UFOs can increase and decrease speeds for no reason, and that they can make sudden right turns at speeds that should be impossible, especially for a moon size UFO.”

Waring asks rhetorically, “Now, are these unmanned giant drones sent to get energy for planets far away? I would say yes, but they don’t have to be unmanned if their technology can protect them from the incredible heat.”

November 30, 2016 0 comment

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US Power Emissions Could Drop 78% Below 1990 Levels By 2030

by Jake Richardson February 5, 2016

written by Jake Richardson

A joint NOAA/CIRES research study has found that greenhouse gas emissions from electric power production could be cut by 78% below 1990 levels by 2030. The National Energy with Weather System (NEWS) simulator model was used for the study, which is a tool used to simulate the electrical power sector. The model is used to help investigate what happens when large amounts of wind and solar power are added into the grid system, as Carbon Brief writes: “As the size of the connected system grows, the amount of wind and solar PV generation increases. Moreover, the cost of electricity decreases as the area increases, because the system has access to more remote, rich resources and the correlation between connected sites weakens.”

In the model, renewable energy generation potential is examined by the analysis of 152,000 NOAA weather data grid points in the continental United States and beyond, including all hours of day from 2006 through 2008.

Some folks who are concerned about the cost of renewable electricity increasing their utility bills might be relieved to hear this: “the model produces power at 8.5 to 10.2 cents per kilowatt hour, less than current national average residential costs of 12.3 cents/kWh (from the Energy Information Administration).” So, a big reduction in climate change emissions and lower costs — what’s not to like?

A new national high-voltage direct current (HVDC) network for transmission was included in the model and its cost was factored into the cost of electricity. A nationwide renewable energy generation system was used in the model as well. Carbon Brief described this system as, “Building a combination of 1,529 GW of solar, wind, natural gas, nuclear and hydro would cover the power needs of the US while reducing CO2 emissions by 78% and keeping costs lower than current projections…”

(It’s a little peculiar that the Carbon Brief quote does not includes geothermal, because it is a clean, renewable, consistently available source and there is a significant potential for it in the US.)

FAQS for the study are here.

Of course, models are not the real world and they are useful in controlled, virtual contexts. The crux of the findings seems to be a counterpoint to the doomsday discourse that seems to be common at times. With steady investments in renewable energy, better grid systems and energy storage, climate change emissions could at least be decreased to some degree and any progress would be welcome.

Image Credit: NOAA

February 5, 2016 0 comment

Science Solar Research

Perovskite Solar Cells Rule, Clean Power Plan Lawsuits Drool

by Tina Casey November 2, 2015

written by Tina Casey

We were just talking about the accelerated pace of R&D for perovskite solar cells, and along comes the University of California, Los Angeles, with another contribution to the perovskite pot. Put that in the context of the lawsuits sprouting up against President Obama’s new Clean Power Plan, and you have yet another instance of the fossil fuel lobby waging battle in a war that’s already been lost.

That’s because perovskite is a cheap, easily manufactured material that has the potential to force the cost of solar energy even lower than it is today, forcing its chief competitors — coal and natural gas — off the electric power plant field, Clean Power Plan or not.

By the way, did you know that the iconic fossil fuel producing state of Texas is already well on the way to meeting its Clean Power Plan goals? More on that in a second.

Perovskite Power, Solar Cell Style

Where were we? Oh right, perovskite solar cells. For those of you new to the topic, perovskite actually refers to a class of synthetic crystalline materials based on the unique properties of the naturally occurring mineral perovskite.

Perovskite offer enormous promise in terms of solar cell conversion efficiency, but they also have an enormous Achilles heel, which is their tendency to fall apart when exposed to air, especially humid air.

Just this week we took note of a futuristic new development in the field involving so called hot-carrier perovskite solar cells, but the new perovskite solar cell research from the University of California – Los Angeles (UCLA) is a bit more down to earth in terms of solving the air-phobia problem.

A team from UCLA’s California Nanosystems Institute has figured out a new way to stabilize perovskite, basically by creating a perovskite solar cell sandwich.

The conventional approach is to use an organic material as the top buffer layer, in order to get the solar-generated electricity out of the cell. However, the materials typically in use aren’t all that stable themselves, and provide relatively poor cover for the perovskite layer.

By replacing those layers with metal oxides, the UCLA team achieved a “dramatic” difference in longevity. Specifically, the new perovskite solar cells are composed of layers in this order: glass, indium tin oxide, NiOx (oxidized nickel oxide), perovskite, zinc oxide, aluminum, with the ZnO layer providing protection by keeping the aluminum from the perovskite.

In a 60-day open air test at room temperature, the metal oxide perovskite solar cells retained 90 percent of their original conversion efficiency.

Okay, so that doesn’t solve the entire problem, but it indicates that the way forward is to engineer metal oxide layers that are more dense, providing better protection for the perovskite.

You can read all about it in the journal Nature.com under the title “Improved air stability of perovskite solar cells via solution-processed metal oxide transport layer.” The study includes a relatively plain-language description of the challenges involved in engineering a long-lived perovskite solar cell.

UCLA’s press materials also provide a good snapshot of just how fast the rate of perovskite R&D is accelerating. The team started less than two years ago with a conversion efficiency of less than one percent, and it’s already closing in on the 20 percent mark. In the new study, the relatively stable version clocked in at approximately 14.6 percent plus or minus 1.5 percent, for a maximum of 16.1 percent.

The Clean Power Plan Battle (Or Horse Race)

As for the Clean Power Plan, our friends over at TheHill.com have been tracking the “quagmire” of lawsuits pouring in from legislators and businesses over the whole bundle of Obama Administration executive actions on climate and environment.

However, the Clean Power Plan may suffer death by a thousand cuts — and Senator Inhofe may schlep a boatload of snowballs to the Paris climate talks — but the simple fact is that the cost of renewable energy generally, and solar energy in particular, has been dropping like a stone despite efforts by the fossil fuel lobby to monkeywrench progress at the federal and local level. When you put an army of scientists up against an army of lawyers, science is already winning. If you prefer sports metaphors, let’s call it a horse race.

In the case of solar energy, the march of technology is only part of the equation. Costs have also been dropping because the Obama Administration has been focusing on smoothing over “soft” bumps for solar energy such as the permitting process, zoning rules, and administrative costs. Those soft costs still account for about 70 percent of the installed cost of a solar array, and the Energy Department has big plans to push that figure way down with a new “same-day” rooftop solar initiative.

If you prefer nature metaphors, take a look at Texas and you’ll see why the Clean Power Plan obstructionists are barking at a losing tree. Thanks partly to its magnificent wind resources, as well as a huge incentive to improve its transmission infrastructure, Texas is already well on its way to meeting its Clean Power Plan goals, even without sporting the kind of clean energy political image that some other states have been working on.

Stay tuned.

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Photo: via UCLA.

November 2, 2015 0 comment

Science Solar Research

Hot-Carrier Perovskite Solar Cells Could Bounce to 66% Efficiency

by Tina Casey October 30, 2015

written by Tina Casey

Perovskite solar cells have been getting a lot of attention for their potential to reach new heights of efficiency and new lows of cost. In the latest development, our friends over at the National Renewable Energy Laboratory have revealed a critical “bottleneck” in perovskite solar conversion that has huge implications for third-generation, super-efficient, hot-carrier solar cells.

Hot-Carrier Solar Cells

For those of you new to the topic of hot-carrier solar cells, you can get the lowdown in plain language from SPIE, the International Society for Optics and Phonics. The gist of it is as follows: With conventional solar cells, you only get two choices: simple materials, low cost, and low efficiency (such as single-junction solar cells); or multiple materials, high cost, and high efficiency (that would be multi-junction solar cells). In contrast, with hot-carrier solar cells, you could get simplicity of design, low cost, and high efficiency all in one, kind of like having your cake and eating it too. Here’s the explanation from SPIE:

“Heat production is detrimental to the output of solar cells. It occurs when a material absorbs photons with energies larger than its bandgap. To circumvent this problem, photogenerated charge carriers must be collected through specially designed contacts that are energy-selective. Carriers with large kinetic energies—‘hot carriers’—reach these contacts before losing most of their energy as heat. In principle, efficiencies as high as 86% could be achieved.”

If that sounds too good to be true, it is. Hot-carrier solar cells are a long way from the marketplace, one big challenge is how to rev up the kinetic energy transfer to top speed (as in, subpicoseconds), in order to prevent energy loss.

Nevertheless, the high return on efficiency makes the hot-carrier field full of temptation. When SPIE covered hot-carrier solar cells back in 2011, the high mark for solar conversion was 40%, achieved by multi-junction solar cells. In December 2014, CleanTechnica took note of a new solar conversion record of 46%. Considering that the theoretical limit is about 87%, that still leaves plenty of room for alternative, “third-generation” technologies to elbow in.

The Perovskite Solution For Hot-Carrier Solar Cells

So, finally, that brings us back around to the National Renewable Energy Laboratory (NREL). Just today, the lab announced that researchers have figured out a pathway for tackling the heat loss problem by deploying hot-carrier technology in perovskite solar cells.

Perovskite refers to a class of easily synthesized crystals with a structure based on a naturally occurring mineral, perovskite, that was discovered in the Ural mountains in 1839. Within recent years, researchers have been pursuing perovskites for improving solar conversion efficiency.

The commercial deployment of perovskite in solar cells faces some obstacles, with the use of lead being a particular thorny issue, but according to NREL, successive versions of perovskite solar cells have been “shooting up the efficiency charts faster than almost anything researchers have seen before,” making them juicy targets for further research, lead or no lead (for the record, tin is being explored as one alternative to lead).

When NREL began studying perovskites in 2009, it achieved a 3.8% efficiency rate. Within just a few years, the latest attempts have jumped up to more than 20%.

The new study, published in Nature Photonics under the title “Observation of a hot-phonon bottleneck in lead-iodide perovskites,” provides a pathway for pushing perovskite levels into the stratosphere, possibly as high as 66%. Here’s the rundown from the NREL media team:

“The NREL research determined that charge carriers created by absorbing sunlight by the perovskite cells encounter a bottleneck where phonons (heat carrying particles) that are emitted while the charge carriers cool cannot decay quickly enough. Instead, the phonons re-heat the charge carriers, thereby drastically slowing the cooling process and allowing the carriers to retain much more of their initial energy for much longer periods of time. This potentially allows this extra energy to be tapped off in a hot-carrier solar cell.”

According to the research team, the new study fills a critical information gap:

“Despite the earlier flurry of activity in characterizing the lead iodide perovskite system by transient absorption (TA) spectroscopy, a comprehensive and profound interpretation of the photocarrier-induced spectra is lacking. Previous work explained the TA spectra using a straightforward state-filling or Burstein–Moss model. However, a full assignment of the spectral response and the correlation between the magnitude of the TA signal and charge carrier density remains unexplored, in particular the role that excitonic transitions play in both the linear and excited-state optical and electronic properties.”

Did you get all that? Coincidentally, this morning, we just got a sneak peek at the new National Geographic–General Electric six-part series on breakthrough technology, aptly titled “Breakthrough,” which begins unspooling this Sunday, November 1. Following the reel, we got to hear from a panel of rather interesting people involved in creating the series, and one of the themes that came up was the speed at which technology is advancing, to the point where the filmmakers found themselves recording new developments practically in real time rather than simply recounting the past. Today’s revved-up world of solar cell research certainly fits the bill.

The whole series looks amazing, and of course we’re especially excited about the “Energy on the Edge” episode directed by the incredible sci-fi storyteller Akiva Goldsman. We’ll bring you some more details about that soon, including an exclusive interview with the folks at Dogfish Head (yep, these guys), a company featured in the episode.

Photo via NREL.

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October 30, 2015 0 comment

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Do Panasonic & SolarCity Announcements Herald Beginning Of Solar Without Subsidies?

by Guest Author October 12, 2015

written by Guest Author

Originally published on The Handleman Post.
By Clayton Handleman

Not so long ago, Sunpower’s 20+% efficiency modules were seen as high end niche products. Last week SolarCity announced that it had leapfrogged that benchmark with its 22% modules currently rolling off of its 100 MW lines and soon to be rolling off its 1 GW line at Elon Musk’s ‘other’ gigafactory. With multiple vendors at GW scale with above 20% efficient modules, PV has reached the point of commoditizing high efficiency modules, and the ripple effect on system level costs has profound implications.

SolarCIty-Truck-1-570x330 Adding fuel to the fire, in a recent Cleantechnica post, Panasonic shot back with its announcement of production prototypes testing at 22.5% efficiency. And the longtime leader, Sunpower, is in the process of upping its game with 23% efficient modules planned for production in 2017 in its Fab 5, which at a planned 800MW (.8GW) is also at the GW scale and rivaling SolarCity’s fab in capacity.

The importance of these announcements cannot be underestimated. SolarCity has long stated that its plan is for its residential PV systems to be cost competitive without subsidies by the time US tax credits expire. Low cost, high efficiency modules offer the path by reducing the physical size of solar arrays and the size-related costs. The benefits of high efficiency include reduced footprint and reduced balance of system costs on a dollars per kW/hr basis and amortization of fixed costs over a larger system capacity.

Many residential systems are limited by roof space, not desired capacity. And a substantial fraction of the cost of residential systems is fixed. As such, by increasing the array capacity those costs can be amortized over a larger project. This reduces the cost per watt and therefore the cost per kW/hr. As module prices have dropped, Balance of System costs for racking, wires, etc. are contributing a larger percentage of system costs. Because more efficient modules provide more energy per square foot, they reduce the cost of balance of system components on a dollars per watt basis. This is explained clearly in this article which includes an easily understood graphic showing how the economics play out. And things have only gotten better since it was written. High efficiency modules are coming in lower than $1.00/W, further amplifying the benefits.

The final piece of the puzzle is gigawatt-scale manufacturing to provide high volume and lower price. SolarCity is doing that with its PV gigafactory, and Panasonic has the scale to develop manufacturing on a globally significant level. When Sunpower was the only game in town and it was producing a tiny fraction of the world’s PV modules, it really didn’t matter how much their modules cost, as it had no real impact on the cost of solar globally.

With high efficiency modules soon to be rolling off gigawatt-scale assembly lines, SolarCity’s vision of PV reaching grid parity even as incentives are phased out appears to be coming to pass. And in volumes with global significance. Clearly the industry is rapidly transitioning to greater than 20% efficiency as the new normal, and with it, the brass ring of cost effective solar without subsidies is rapidly coming within reach.

Reprinted with permission.

October 12, 2015 0 comment

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A (Relatively) Gigantic Perovskite Solar Cell Breakthrough

by Tina Casey October 9, 2015

written by Tina Casey

We’ve been spilling a lot of ink over perovskite solar cells recently, and here comes Brown University with yet another breakthrough. Along with researchers from the National Renewable Energy Laboratory, the Brown team has figured out a way to grow larger perovskite solar cells while keeping the conversion efficiency at a fairly high level. (h/t James Wimberley)

The Promise Of Perovskites

Solar researchers are all over perovskites, a class of synthetic crystals that mimic the unique structure of naturally occurring perovskite. Perovskites could become a low-cost, easy-to-manufacture substitute for silicon in solar cells, and researchers have been slowly breaking down the barriers to achieving that.

One problem, according to the Brown team, is that while relatively high solar conversion efficiencies of more than 20% have been reported in the laboratory, those are based on very small samples, typically 1/10 of a square centimeter.

Conventional processes for producing larger perovskite solar cells have fallen short in the quality department, with defects that interfere with efficiency.

“Glue” For Bigger, Better Perovskite Solar Cells

The new study can be found in the journal Advanced Materials under the title “Square-Centimeter Solution-Processed Planar CH3NH3PbI3 Perovskite Solar Cells with Efficiency Exceeding 15%.”

It’s based on a perovskite fabrication process previously developed at Brown, in which a solvent containing perovskite precursors is spread out on a substrate. An “anti-solvent” is then applied to get rid of the first solvent, leaving a nice smooth film of perovskite crystals.

The beauty of this method, aside from yielding a high-quality product, is its potential for scaling up to a commercial rate while keeping costs down, one factor being its ability to produce perovskite solar cells under room temperature conditions.

Scaling that process up is the challenge tackled by the new perovskite study. Here’s the rundown from Brown:

“The trick is to add excess organic precursor that initially “glues” the small perovskite crystals and helps them merge into larger ones during a heat-treatment, which then bakes away the excess precursor.”

Initial results for the new perovskite solar cells show an efficiency of 15%, which is not bad considering the potential to churn them out quickly and cheaply.

The team is pretty confident that this method, or one closely resembling it, could eventually get up to the 20% range and higher.

From The Lab To… Your Electric Vehicle

We’re still a ways away from a perovskite solar cell in every pot (except for maybe these guys), but when perovskites break through, there could be some very interesting applications in the mix.

In particular, we’re keeping an eye on this one with our sister site Gas2.org — a perovskite coating for electric vehicles, which would recharge your battery on the go a lot more efficiently than strapping a panel of silicon solar cells on top.

Earlier this year, we also floated the idea that Volkswagen might be toying around with a perovskite based EV battery, with a decision on the new battery apparently due this past July.

That date has come and gone, and the last we heard, Volkswagen chief Martin Winterkorn was still teasing the idea, so if you’ve heard anything drop us a note in the comment thread.

Meanwhile, of course, Winterkorn has left the company, which appears to have its hands full with other matters.

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Image via Brown University/NREL.

October 9, 2015 0 comment

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12 Solar Facts You Should Know

by Glenn Meyers October 8, 2015

written by Glenn Meyers

Lists are always fun, so here are 12 solar facts to put in your notebook so you can share the important stuff with anyone who’s interested.

I have divided this list of facts into four categories that might help you to better keep track of things.

Understanding Our Sun
Solar History
Solar Technology
Solar Metrics

But before you start this list of 12 solar facts, how about a quick trip to the classroom that might help bring all readers up to speed? Here’s a short book list:

Solar Electricity Handbook – 2014 Edition: A Simple, Practical Guide to Solar Energy – Designing and Installing Photovoltaic Solar Electric Systems, by Michael Boxworth
Let It Shine: The 6,000-Year History of Solar Energy, by John Perlin
Photovoltaic Design & Installation For Dummies, by Ryan Mayfield.

Understanding Our Sun

Age: Estimates calculate our sun is 4.6 billion years old, ands will continue burning its hydrogen fuel for another 5 billion years. Will it eventually burn out? Yes, of course — we all learned that in elementary school, right? For those fretting about the lifespan of their PV system’s power source, don’t worry.

Size: The sun is an average-sized star, we find at Cornell’s “Ask An Astronomer.” Here, Christopher Springob tells us, “The biggest stars are more than 100 times as massive as the Sun, and the smallest stars are less than 1/10th as massive as the Sun.”

Closeup Inspection: The NASA video below is worth seeing. In it, we learn that hydrogen is fused into helium in the core of the sun.

Solar History

Solar Ignitors: Historian John Perlin provides this information gem: During the sixth century BCE, Confucius wrote about the common use of curved mirrors shaped from shiny metal to concentrate the rays of the sun for making fire. These became known as yang-suis – translating to solar ignitors or burning mirrors. According to the great philosopher, upon waking up, the eldest son would attach a solar ignitor to his belt as he dressed for the day. It was his duty to focus the solar rays onto kindling to start the family’s cooking fire.

Photovoltaics’ Discovery: Willoughby Smith’s 1872 experiments that proved the photosensitivity of selenium stirred keen interest in two British scientists, William Grylls Adams and Richard Evans Day, to discover something previously unknown to science – that a current could be started by the action of “light alone” in a solid-state material. The two scientists called the flow of electricity caused by light, “photoelectric.” Today, we say, “photovoltaic.” So began in 1875 the first stirrings of today’s solar revolution.

Effort To Commercialize PV: Charles Fritts, an American inventor, built the first solar panels in 1881. They produced a current, Fritts reported, “that is continuous, constant and of considerable force not only by exposure to sunlight but also to dim, diffused daylight.”

Solar Technology

Photovoltaics: Historian John Perlin said this about the public reaction to Einstein’s photoelectric discovery: “Even after proving the validity of Einstein’s light quanta equation in explaining the photoelectric effect, Milliken dismissed the physicality of the photon as ‘untenable.’ In 1923, 18 years after Einstein published his light quanta piece, American physicist Arthur Hailey Compton created a collision between a stationary electron and a short wave of light. Just as in billiards, when the cue ball strikes its target, the light wave transferred some of its energy and momentum to the electron… After the Compton Experiment, the reality of Einstein’s photon and the photovoltaic effect gained universal acceptance in the scientific community.”

Concentrated Solar Power: Concentrated solar power (also called concentrating solar power, concentrated solar thermal, and CSP) systems generate solar power by using mirrors or lenses to concentrate a large area of sunlight, or solar thermal energy, onto a small area. The heat is what is used to eventually spin a turbine and generate electricity (very different from how solar PV generates electricity).

Solar Net Metering: The world’s first net-metered solar system was connected to the grid in 1979, when 28-year old architect Steven Strong put solar PV panels on two buildings making up a 270-unit apartment complex and connected them to a utility meter that tracked how much solar electricity was sent back into the grid. “A small meter mounted on the wall of the dining room told the story in kilowatts. When the utility power was drawn it ran forward. But when the PV was pumping out excess power, it ran backward.”

Solar Metrics

Solar Power In The US: Solar power in the United States surpassed 20 gigawatts (GW) of installed capacity in 2015. “The report also highlights the fact that 40% of all new electric generating capacity brought online in the first half of 2015 in the US came from solar. 21 states throughout the country now have more than 100 MW of solar PV capacity, though the top five states in terms of solar capacity account for nearly ¾ of the total US cumulative PV capacity.”

Solar US Growth Spurt: From 2006 to 2013, the number of homes with solar power grew by more than 1,000 percent in the US, from 30,000 home to 400,000 homes.

Cost Of Solar: The lowest electricity price ever bid by a solar developer was 0.1875 Riyals ($0.049) per kilowatt-hour (kWh) by the Saudi Electric Company in Saudi Arabia in August 2015. That’s far less than the average price of electricity from natural gas or any other electricity source in the region.

There is plenty more that can be added to this list, but I hope this is a great starting place for understanding this stunning renewable energy source.

Image: Solar collage via Shuttersock

October 8, 2015 0 comment

Science Solar Modules Solar Research Thin Film Solar

Detergent-Enabled “Green” Thin-Film Solar Cells Wipe The Floor With “Clean” Diesel

by Tina Casey October 6, 2015

written by Tina Casey

As the saying goes, there ain’t no such thing as a free lunch. You can’t generate usable energy without some form of impact, whether it’s fossil fuels or renewables, and the Volkswagen “clean diesel” scandal provides ample evidence that technology solutions for fossil fuels are reaching their limit. In contrast, a new “green” thin-film solar cell study by Oak Ridge National Laboratory in the US demonstrates that solar energy has ample wiggle room to earn its clean cred.

What’s Not Clean About Thin Film Solar Cells

While solar energy is renewable, creating the goods needed to harvest that energy involves impacts all along the supply chain, from mining to manufacturing.

We’ve been spilling a lot of ink on thin-film solar cells partly because, although their solar conversion efficiency can’t match conventional silicon solar cells, they involve a highly efficient manufacturing process that cuts costs and helps to reduce lifecycle impacts. What has escaped our attention — our bad — is that the typical thin-film solar cell manufacturing process involves solvents, which are generally toxic.

The Road To Greener Thin Film Solar Cells

Well, group hug for all you US taxpayers. The new thin-film solar cell study from Oak Ridge National Laboratory (ORNL) indicates that the industry could transition out of its dependency on toxic solvents in favor of a more environmentally relaxed solvent called a surfactant, which is fancyspeak for detergent.

If you’re up for it, you can find the study under the title “Controlling molecular ordering in solution-state conjugated polymers” in the aptly named journal Nanoscale.

As described by ORNL, in the manufacturing of conventional thin-film solar cells, toxic solvents are deployed to shepherd molecules of polymers (that’s fancyspeak for plastics) to form nanoscale films. That’s 1,000 times thinner than your hair, for those of you keeping score at home.

To come up with a non-toxic alternative, the ORNL team designed a unique new polymer with a water-repelling “backbone” and water-attracting side chains.

The next step was to put the tailor-made polymer into a solution with a non-toxic surfactant. Like the new polymer, the surfactant also had both water-repelling (hydrophobic) and water-attracting (hydrophilic) ends.

When the research team tweaked the temperature and concentration of the solution, this happened:

“…the surfactant self-assembles into different templates that guide the polymer to pack into different nanoscale shapes—hexagons, spherical micelles and sheets.”

In other words, the surfactant arranges itself in a series of tiny stamps — kind of like nanoscale cookie cutters — that determine the shape of the polymer.

Here’s research team co-leader Jiahua Zhu enthusing over the discovery:

“Rationally encoding molecular interactions to rule the molecular geometry and inter-molecular packing order in a solution of conjugated polymers is long desired in optoelectronics and nanotechnology…”

Zhu further notes that the team was able to confirm its findings accurately because the researchers measured the effect of the surfactant in situ (fancyspeak for “in place”), instead of isolating the material or altering their tests.

Another Group Hug For Greener Thin-Film Solar Cells

Accurate in situ measurements can be extremely difficult — think of the difference between measuring the length of an eel while it’s swimming, compared to pinning it out on a board.

For its delicate nanoscale task, the ORNL team designed a test chamber that enabled the use of optical probes while the surfactant was busy doing its work.

So, another group hug for us taxpayers. The research team was based at ORNL’s Spallation Neutron Source, which does this:

“SNS is a one-of-a-kind research facility that provides the most intense pulsed neutron beams in the world for scientific research and industrial development. SNS produces neutrons with an accelerator-based system that delivers short (microsecond) proton pulses to a target/moderator system, where neutrons are produced by a process called spallation.”

That’s just for starters. Along with the spallation, you have your deuteration, which is a method for depositing heavier atoms into the polymer. That makes it easier to pick out contrasts, which helps to define the structure accurately as it evolves over time, from a solution to a solid.

In addition to defining the structure, the test chamber enables researchers to monitor the changing state of the material in real time when exposed to different conditions, including the type of solvent and the temperature, pressure, and humidity.

Don’t run out to Home Depot just yet to get your greener thin-film solar cells. So far, the research team has tested the new non-toxic self-assembly method under increasing temperatures. The next step is to do pressure tests, among other things.

As for so-called “clean diesel,” it looks like you can lump that in the same category as “clean coal.”

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Image: “A surfactant template guides the self-assembly of functional polymer structures in an aqueous solution” by Youngkyu Han and Renee Manning, via Oak Ridge National Laboratory.

October 6, 2015 0 comment

New Technology PV Science Solar Research

New Solar Tracking Technology Boosts Efficiency

by Steve Hanley September 14, 2015

written by Steve Hanley

A solar cell that tracks the sun’s movement across the sky can generate 40% more electricity than a stationary panel. But tracking devices add complexity and cost. They also are subject to malfunction due to ice, snow, or high winds.

Researchers at the University of Michigan, led by Max Shtein and Stephen Forrest, both professors of materials science and engineering, say they have devised a new solar tracking technology that follows the sun without moving an entire solar panel. They cut solar cells into specific designs using kirigami, a variation of origami which entails cutting in addition to folding, reports CleanTechnica.

Making a specific kirigami cut creates strips in a solar cell. By pulling the two ends in opposite directions, the strips can make the solar cells tilt and assume a desired angle. Done correctly, the structure changes shape in a way that prevents the individual strips from casting shadows on each other and the “waviness” of the new form does not detract from solar performance.

The kirigami approach makes it possible to generate more electricity while using the same amount of semiconducting material and is nearly as effective as conventional tracking systems, says Shtein. Most of those systems are cumbersome and costly. Not only that, they don’t work well on most pitched rooftop systems, which account for the majority of rooftop solar installations.

The University of Michigan system uses flexible solar cells made of gallium arsenide. The research is only at the “proof of concept” phase and will take a lot more work before the system is suitable for commercial applications. The researchers need to devise a system for encasing the structures to protect them against the weather and provide mechanical support. Then they will need small electric motors to pull the cells apart at specific times during the day.

“It doesn’t take much force at all,” says Shtein. Although the approach is best suited for thin, flexible materials; in principle, it could work with “almost any kind of solar cell,” he says.

September 14, 2015 0 comment

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