Short-lived solar panels can be economically viable

A new study shows that replacing new solar panels after just 10 or 15 years, using the existing mountings and control systems, can make economic sense, contrary to industry expectations that a 25-year lifetime is necessary.

Research shows that, contrary to accepted rule of thumb, a 10- or 15-year lifetime can be good enough.

A new study shows that, contrary to widespread belief within the solar power industry, new kinds of solar cells and panels don’t necessarily have to last for 25 to 30 years in order to be economically viable in today’s market.

Rather, solar panels with initial lifetimes of as little as 10 years can sometimes make economic sense, even for grid-scale installations — thus potentially opening the door to promising new solar photovoltaic technologies that have been considered insufficiently durable for widespread use.

The new findings are described in a paper in the journal Joule, by Joel Jean, a former MIT postdoc and CEO of startup company Swift Solar; Vladimir Bulovi?, professor of electrical engineering and computer science and director of MIT.nano; and Michael Woodhouse of the National Renewable Energy Laboratory (NREL) in Colorado.

“When you talk to people in the solar field, they say any new solar panel has to last 25 years,” Jean says. “If someone comes up with a new technology with a 10-year lifetime, no one is going to look at it. That’s considered common knowledge in the field, and it’s kind of crippling.”

Jean adds that “that’s a huge barrier, because you can’t prove a 25-year lifetime in a year or two, or even 10.” That presumption, he says, has left many promising new technologies stuck on the sidelines, as conventional crystalline silicon technologies overwhelmingly dominate the commercial solar marketplace. But, the researchers found, that does not need to be the case.

“We have to remember that ultimately what people care about is not the cost of the panel; it’s the levelized cost of electricity,” he says. In other words, it’s the actual cost per kilowatt-hour delivered over the system’s useful lifetime, including the cost of the panels, inverters, racking, wiring, land, installation labor, permitting, grid interconnection, and other system components, along with ongoing maintenance costs.

Part of the reason that the economics of the solar industry look different today than in the past is that the cost of the panels (also known as modules) has plummeted so far that now, the “balance of system” costs — that is, everything except the panels themselves —  exceeds that of the panels. That means that, as long as newer solar panels are electrically and physically compatible with the racking and electrical systems, it can make economic sense to replace the panels with newer, better ones as they become available, while reusing the rest of the system.

“Most of the technology is in the panel, but most of the cost is in the system,” Jean says. “Instead of having a system where you install it and then replace everything after 30 years, what if you replace the panels earlier and leave everything else the same? One of the reasons that might work economically is if you’re replacing them with more efficient panels,” which is likely to be the case as a wide variety of more efficient and lower-cost technologies are being explored around the world.

He says that what the team found in their analysis is that “with some caveats about financing, you can, in theory, get to a competitive cost, because your new panels are getting better, with a lifetime as short as 15 or even 10 years.”

Although the costs of solar cells have come down year by year, Bulovi? says, “the expectation that one had to demonstrate a 25-year lifetime for any new solar panel technology has stayed as a tautology. In this study we show that as the solar panels get less expensive and more efficient, the cost balance significantly changes.”

He says that one aim of the new paper is to alert the researchers that their new solar inventions can be cost-effective even if relatively short lived, and hence may be adopted and deployed more rapidly than expected. At the same time, he says, investors should know that they stand to make bigger profits by opting for efficient solar technologies that may not have been proven to last as long, knowing that periodically the panels can be replaced by newer, more efficient ones.

“Historical trends show that solar panel technology keeps getting more efficient year after year, and these improvements are bound to continue for years to come,” says Bulovi?. Perovskite-based solar cells, for example, when first developed less than a decade ago, had efficiencies of only a few percent. But recently their record performance exceeded 25 percent efficiency, compared to 27 percent for the record silicon cell and about 20 percent for today’s standard silicon modules, according to Bulovi?. Importantly, in novel device designs, a perovskite solar cell can be stacked on top of another perovskite, silicon, or thin-film cell, to raise the maximum achievable efficiency limit to over 40 percent, which is well above the 30 percent fundamental limit of today’s silicon solar technologies. But perovskites have issues with longevity of operation and have not yet been shown to be able to come close to meeting the 25-year standard.

Bulovi? hopes the study will “shift the paradigm of what has been accepted as a global truth.” Up to now, he says, “many promising technologies never even got a start, because the bar is set too high” on the need for durability.

For their analysis, the team looked at three different kinds of solar installations: a typical 6-kilowatt residential system, a 200-kilowatt commercial system, and a large 100-megawatt utility-scale system with solar tracking. They used NREL benchmark parameters for U.S. solar systems and a variety of assumptions about future progress in solar technology development, financing, and the disposal of the initial panels after replacement, including recycling of the used modules. The models were validated using four independent tools for calculating the levelized cost of electricity (LCOE), a standard metric for comparing the economic viability of different sources of electricity.

In all three installation types, they found, depending on the particulars of local conditions, replacement with new modules after 10 to 15 years could in many cases provide economic advantages while maintaining the many environmental and emissions-reduction benefits of solar power. The basic requirement for cost-competitiveness is that any new solar technology that is to be installed in the U.S should start with a module efficiency of at least 20 percent, a cost of no more than 30 cents per watt, and a lifetime of at least 10 years, with the potential to improve on all three.

Jean points out that the solar technologies that are considered standard today, mostly silicon-based but also thin-film variants such as cadmium telluride, “were not very stable in the early years. The reason they last 25 to 30 years today is that they have been developed for many decades.” The new analysis may now open the door for some of the promising newer technologies to be deployed at sufficient scale to build up similar levels of experience and improvement over time and to make an impact on climate change earlier than they could without module replacement, he says.

“This could enable us to launch ideas that would have died on the vine” because of the perception that greater longevity was essential, Bulovi? says.

Learn more: Study: Even short-lived solar panels can be economically viable


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Placing solar panels on agricultural lands maximizes their efficiency

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The most productive places on Earth for solar power are farmlands, according to an Oregon State University study.

The study, published today in the journal Scientific Reports, finds that if less than 1% of agricultural land was converted to solar panels, it would be sufficient to fulfill global electric energy demand. The concept of co-developing the same area of land for both solar photovoltaic power and conventional agriculture is known as agrivoltaics.

“Our results indicate that there’s a huge potential for solar and agriculture to work together to provide reliable energy,” said corresponding author Chad Higgins, an associate professor in OSU’s College of Agricultural Sciences. “There’s an old adage that agriculture can overproduce anything. That’s what we found in electricity, too. It turns out that 8,000 years ago, farmers found the best places to harvest solar energy on Earth.”

The results have implications for the current practice of constructing large solar arrays in deserts, Higgins said.

“Solar panels are finicky,” he said. “Their efficiency drops the hotter the panels get. That barren land is hotter. Their productivity is less than what it could be per acre.”

For their study, OSU researchers analyzed power production data collected by Tesla, which has installed five large grid-tied, ground-mounted solar electric arrays on agricultural lands owned by Oregon State. Specifically, the team looked at data collected every 15 minutes at the 35th Street Solar Array installed in 2013 on the west side of OSU’s Corvallis campus.

The researchers synchronized the Tesla information with data collected by microclimate research stations they installed at the array that recorded mean air temperature, relative humidity, wind speed, wind direction, soil moisture and incoming solar energy.

Based on those results, Elnaz Hassanpour Adeh, a recent Ph.D. graduate from OSU’s water resources engineering program and co-author on the study, developed a model for photovoltaic efficiency as a function of air temperature, wind speed and relative humidity.

“We found that when it’s cool outside the efficiency gets better,” Higgins said. “If it’s hot the efficiency gets worse. When it is dead calm the efficiency is worse, but some wind makes it better. As the conditions became more humid, the panels did worse. Solar panels are just like people and the weather, they are happier when it’s cool and breezy and dry.”

Using global maps made from satellite images, Adeh then applied that model worldwide, spanning 17 classes of globally accepted land cover, including classes such as croplands, mixed forests, urban and savanna. The classes were then ranked from best (croplands) to worst (snow/ice) in terms of where a solar panel would be most productive.

The model was then re-evaluated to assess the agrivoltaic potential to meet projected global electric energy demand that has been determined by the World Bank.

Higgins and Adeh previously published research that shows that solar panels increase agricultural production on dry, unirrigated farmland. Those results indicated that locating solar panels on pasture or agricultural fields could increase crop yields.

Learn more: Installing solar panels on agricultural lands maximizes their efficiency, new study shows


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New GraphExeter Material Able to Withstand Temperature and Humidity Extremes



A resilience to extreme conditions by the most transparent, lightweight and flexible material for conducting electricity could help revolutionise the electronic industry, according to a new study.

Researchers from the University of Exeter have discovered that GraphExeter – a material adapted from the ‘wonder material’ graphene – can withstand prolonged exposure to both high temperature and humidity.

The research showed that the material could withstand relative humidy of up to 100 per cent at room temperature for 25 days, as well as temperatures of up to 150C – or as high as 620C in vacuum.

The previously unknown durability to extreme conditions position GraphExeter as a viable and attractive replacement to indium tin oxide (ITO), the main conductive material currently used in electronics, such as ‘smart’ mirrors or windows, or even solar panels. The research also suggests that GraphExeter could extend the lifetime of displays such as TV screens located in highly humid environments, including kitchens.

These research findings are published in the respected scientific journal, Scientific Reports, on Thursday, 8 January 2015.

Lead researcher, University of Exeter engineer Dr Monica Craciun said: “This is an exciting development in our journey to help GraphExeter revolutionise the electronics industry.

“By demonstrating its stability to being exposed to both high temperatures and humidity, we have shown that it is a practical and realistic alternative to ITO. This is particularly exciting for the solar panel industry, where the ability to withstand all weathers is crucial.”

Read more: GraphExeter defies the Achilles heel of wonder material graphene


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British scientists develop solar panels which work better on a cloudy day

English: Cloudy morning Sun shining through cloud (Photo credit: Wikipedia)

In a departure from ‘blue sky thinking’ scientists in Britain have developed solar panels that work better on a cloudy day.

Their material is as thin and flexible as cloth, and can be made in any colour and printed in sheets on a 3D printer.

Although the technology is still at development stage, researchers hope that in future it could be used to make coats or bags which could charge phones or laptops or keep the wearer warm.

It is so lightweight that it could also be fitted to homes cheaply without the need to reinforce roofs and would be virtually invisible so homeowners would not be forced to put up with the eyesore of solar panels.

Car manufactures Fiat and Ford are also testing it to see if it could be added to car roofs to charge electrical circuits and avoid flat batteries.

Traditional solar cells are made of semi-conductors such as crystalline silicon. When light strikes the cell some of the energy is absorbed and knocks electrons loose in the silicon which can be forced into a current and drawn off for external use.

The new technology use small organic molecules as semi conductors which can be dissolved in a solution and printed in any shape using a 3D printer.

Most photovoltaics work best in strong, direct, sunlight of an intensity that is rarely seen in northern European countries.

But intriguingly the new material – known as organic photovoltaic – works more efficiently when out of direct sunlight, so is well suited for Britain’s inclement weather.

Scientists discovered that when testing it in direct sunlight desert conditions it could only manage 10 per cent efficiency, but in cloudy conditions that jumped to 13 per cent.

Dr Fernando Castro, principal research scientists at the National Physical Laboratory in Teddington, said: “Organic photovoltaics work much better in low and diffused light conditions. Even if it’s cloudy they still work.

“It’s not that they are going to produce more power but they are more efficient at generating power from the light that is available. So they would work better than normal soar cells do in cloud.”

The material would be cheaper and more environmentally friendly than traditional solar cells, slashing the cost of installing them on homes.

Read more . . .


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A new material for solar panels could make them cheaper, more efficient

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An illustration of the perovskite crystal fabricated in the experiment. Image credit: Felice Macera

A unique solar panel design made with a new ceramic material points the way to potentially providing sustainable power cheaper, more efficiently, and requiring less manufacturing time.

It also reaches a four-decade-old goal of discovering a bulk photovoltaic material that can harness energy from visible and infrared light, not just ultraviolet light.

Scaling up this new design from its tablet-size prototype to a full-size solar panel would be a large step toward making solar power affordable compared with other means of producing electricity. It would also help the nation toward its goal of creating a national power grid that receives one-third of its power through wind and solar sources.

This affordable sun-powered future could be closer than we think thanks to early tests on this new material, which was developed by a team led by scientists at the University of Pennsylvania and Drexel University. The tests were conducted, in part, at the Advanced Photon Source housed at the U.S. Department of Energy’s Argonne National Laboratory.

The team created a new class of ceramic materials that has three main benefits. First, it can produce a solar panel that is thinner than today’s silicon-based market leaders by using one material to do the work of two. Second, it uses cheaper materials than those used in today’s high-end thin-film solar panels. Third, the material is ferroelectric, which means it can switch polarity, a key trait for exceeding the theorized energy-efficiency limits of today’s solar cell material.

Part of the reason solar panels have low efficiency is that the particles collected from the sun enter the solar cell and spread out in all directions. Getting them all to flow one direction typically requires layers of different channeling material. Each time the particles pass between these layers some get lost, decreasing the energy efficiency of the solar cell. The team’s new design uses fewer layers to limit loss and uses ferroelectric material to use up less energy channeling the particles.

It took more than five years to model and design a material with this combination of properties. The material uses perovskite crystals made with a combination of potassium niobate and barium nickel niobate. It has shown significant improvement over today’s classic ferroelectric material. The new material can absorb six times more energy and transfer a photocurrent 50 times denser. Further tuning of the material’s composition should expand efficiency, the scientists say.

“This family of materials is all the more remarkable because it is comprised of inexpensive, non-toxic and earth-abundant elements, unlike compound semiconductor materials currently used in efficient thin-film solar cell technology,” said Jonathan Spanier, a team member from Drexel’s Department of Materials Science and Engineering.

Read more . . .


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