Placing solar panels on agricultural lands maximizes their efficiency

via OSU

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

 

The Latest on: Agrivoltaics

via  Bing News

 

Transforming lighting technology and photovoltaics so you can paint them on

Carlos Silva and Felix Thouin in Silva’s lab at Georgia Tech

LED lights and monitors, and quality solar panels were born of a revolution in semiconductors that efficiently convert energy to light or vice versa. Now, next-generation semiconducting materials are on the horizon, and in a new study, researchers have uncovered eccentric physics behind their potential to transform lighting technology and photovoltaics yet again.

Comparing the quantum properties of these emerging so-called hybrid semiconductors with those of their established predecessors is about like comparing the Bolshoi Ballet to jumping jacks. Twirling troupes of quantum particles undulate through the emerging materials, creating, with ease, highly desirable optoelectronic (light-electronic) properties, according to a team of physical chemists led by researchers at the Georgia Institute of Technology.

These same properties are impractical to achieve in established semiconductors.

The particles moving through these new materials also engage the material itself in the quantum action, akin to dancers enticing the floor to dance with them. The researchers were able to measure patterns in the material caused by the dancing and relate them to the emerging material’s quantum properties and to energy introduced into the material.

These insights could help engineers work productively with the new class of semiconductors.

Unusually flexible semiconductors

The emerging material’s ability to house diverse, eccentric quantum particle movements, analogous to the dancers, is directly related to its unusual flexibility on a molecular level, analogous to the dancefloor that joins in the dances. By contrast, established semiconductors have rigid, straight-laced molecular structures that leave the dancing to quantum particles.

The class of hybrid semiconductors the researchers examined is called halide organic-inorganic perovskite (HOIP), which will be explained in more detail at bottom along with the “hybrid” semiconductor designation, which combines a crystal lattice — common in semiconductors — with a layer of innovatively flexing material.

Beyond their promise of unique radiance and energy-efficiency, HOIPs are easy to produce and apply.

Paint them on

“One compelling advantage is that HOIPs are made using low temperatures and processed in solution,” said Carlos Silva, a professor in Georgia Tech’s School of Chemistry and Biochemistry. “It takes much less energy to make them, and you can make big batches.” Silva co-led the study alongside Ajay Ram Srimath Kandada from Georgia Tech and the Istituto Italiano di Tecnologia.

It takes high temperatures to make most semiconductors in small quantities, and they are rigid to apply to surfaces, but HOIPs could be painted on to make LEDs, lasers or even window glass that could glow in any color from aquamarine to fuchsia. Lighting with HOIPs may require very little energy, and solar panel makers could boost photovoltaics’ efficiency and slash production costs.

The team led by Georgia Tech included researchers from the Université de Mons in Belgium and the Istituto Italiano di Tecnologia. The results were published on January 14, 2019, in the journal Nature Materials. The work was funded by the U.S. National Science Foundation, EU Horizon 2020, the Natural Sciences and Engineering Research Council of Canada, the Fond Québécois pour la Recherche, and the Belgian Federal Science Policy Office.

Quantum jumping jacks

Semiconductors in optoelectronic devices can either convert light into electricity or electricity into light. The researchers concentrated on processes connected to the latter: light emission.

The trick to getting a material to emit light is, broadly speaking, to apply energy to electrons in the material, so that they take a quantum leap up from their orbits around atoms then emit that energy as light when they hop back down to the orbits they had vacated. Established semiconductors can trap electrons in areas of the material that strictly limit the electrons’ range of motion then apply energy to those areas to make electrons do quantum leaps in unison to emit useful light when they hop back down in unison.

“These are quantum wells, two-dimensional parts of the material that confine these quantum properties to create these particular light emission properties,” Silva said.

Imaginary particle excitement

There is a potentially more attractive way to produce the light, and it is a core strength of the new hybrid semiconductors.

An electron has a negative charge, and an orbit it vacates after having been excited by energy is a positive charge called an electron hole. The electron and the hole can gyrate around each other forming a kind of imaginary particle, or quasiparticle, called an exciton.

“The positive-negative attraction in an exciton is called binding energy, and it’s a very high-energy phenomenon, which makes it great for light emitting,” Silva said.

When the electron and the hole reunite, that releases the binding energy to make light. But usually, excitons are very hard to maintain in a semiconductor.

“The excitonic properties in conventional semiconductors are only stable at extremely cold temperatures,” Silva said. “But in HOIPs the excitonic properties are very stable at room temperature.”

Ornate quasiparticle twirling

Excitons get freed up from their atoms and move around the material. In addition, excitons in an HOIP can whirl around other excitons, forming quasiparticles called biexcitons. And there’s more.

Excitons also spin around atoms in the material lattice. Much the way an electron and an electron hole create an exciton, this twirl of the exciton around an atomic nucleus gives rise to yet another quasiparticle called a polaron. All that action can result in excitons transitioning to polarons back. One can even speak of some excitons taking on a “polaronic” nuance.

Compounding all those dynamics is the fact that HOIPs are full of positively and negatively charged ions. The ornateness of these quantum dances has an overarching effect on the material itself.

Wave patterns resonate

The uncommon participation of atoms of the material in these dances with electrons, excitons, biexcitons and polarons creates repetitive nanoscale indentations in the material that are observable as wave patterns and that shift and flux with the amount of energy added to the material.

“In a ground state, these wave patterns would look a certain way, but with added energy, the excitons do things differently. That changes the wave patterns, and that’s what we measure,” Silva said. “The key observation in the study is that the wave pattern varies with different types of excitons (exciton, biexciton, polaronic/less polaronic).”

The indentations also grip the excitons, slowing their mobility through the material, and all these ornate dynamics may affect the quality of light emission.

Rubber band sandwich

The material, a halide organic-inorganic perovskite, is a sandwich of two inorganic crystal lattice layers with some organic material in between them – making HOIPs an organic-inorganic hybrid material. The quantum action happens in the crystal lattices.

The organic layer in between is like a sheet of rubber bands that makes the crystal lattices into a wobbly but stable dancefloor. Also, HOIPs are put together with many non-covalent bonds, making the material soft.

Individual units of the crystal take a form called perovskite, which is a very even diamond shape, with a metal in the center and halogens such as chlorine or iodine at the points, thus “halide.” For this study, the researchers used a 2D prototype with the formula (PEA)2PbI4.

Learn more: Brilliant Glow of Paint-On Semiconductors Comes from Ornate Quantum Physics

 

 

The Latest on: Semiconducting materials

via  Bing News

 

New double-glazing solar power device aims for more advanced photovoltaics

Dr. Gavin Bell and Dr. Yorck Ramachers in the laboratory.
CREDIT
University of Warwick

A new ‘double-glazing’ solar power device — which is unlike any existing solar panel and opens up fresh opportunities to develop more advanced photovoltaics – has been invented by University of Warwick researchers
  • New ‘double-glazed’ solar power device opens up fresh opportunities to develop more advanced photovoltaics – invented by University of Warwick researchers
  • Totally new way of collecting solar energy – using gas rather than vacuum to collect electricity – inspired by early 20th century ideas
  • Researchers currently seeking optimal material for device – one possibility is diamond film

A new ‘double-glazing’ solar power device – which is unlike any existing solar panel and opens up fresh opportunities to develop more advanced photovoltaics – has been invented by University of Warwick researchers.

This unique approach, developed by Dr Gavin Bell and Dr Yorck Ramachers from Warwick’s Department of Physics, uses gas – rather than vacuum – to transport electrical energy,

The device is essentially a thin double-glazed window. The outer pane is transparent and conducts electricity. The inner window is coated with a special material, which acts a source of electrons under illumination by sunlight – this is called a “photocathode”.

The two panes are separated by a safe inert gas, such as argon – exactly as is found in high quality double glazing windows.

When sunlight hits the device, electrons are knocked out of the photocathode and bounce through the gas to the outer pane without being absorbed or lost.

This is totally different to how electrons act in existing solar panels, and opens up the possibility of improving solar power generation methods – whereas improvements in classic photovoltaics are hard to come by.

The electrons are then collected and the electrical energy pumped into the grid. This can be done through a gas-filled gap rather than a vacuum which would be far more cost-effective for any practical device.

Dr Bell and Dr Ramachers re-investigated ideas about the photoelectric effect dating back to Nikola Tesla and Albert Einstein when they considered whether these ideas could be used for modern solar power generation – leading to the development of this new process.

Dr Gavin Bell, from the University of Warwick’s Department of Physics, commented:

“It’s satisfying to find a new twist on ideas dating back to the start of the 20th century, and as a materials physicist it is fascinating to be looking for materials which would operate in an environment so different to standard photocathodes.”

The optimal material for the photosensitive layer still needs to be identified, and the researchers have proposed a range of candidate materials – including thin films of diamond, which would be very robust and long-lasting.

The transparency of the photocathode could be varied, leading to the possibility of tinted windows generating solar power.

The researchers would like the scientific community to think about potential optimal materials:

“We think the materials challenge is really critical here so we wanted to encourage the materials science community to get creative,” said Dr Bell. “Our device is radically different from standard photovoltaics, and can even be adapted for other green technologies such as turning heat directly into electricity, so we hope this work will inspire new advances.”

Learn more: Solar Power Advances Possible with New ‘Double-Glazing’ Device

 

The Latest on: Double-glazing solar power device

via Google News and Bing News

New technique offers spray-on solar power

It may look more like Junk Yard Wars than high-tech, but U of T researcher Illan Kramer's device is the first step towards spray-on solar cells. Click for video

It may look more like Junk Yard Wars than high-tech, but U of T researcher Illan Kramer’s device is the first step towards spray-on solar cells. Click for video

Pretty soon, powering your tablet could be as simple as wrapping it in cling wrap.

That’s Illan Kramer’s (ECE) hope. Kramer and colleagues have just invented a new way to spray solar cells onto flexible surfaces using miniscule light-sensitive materials known as colloidal quantum dots (CQDs)—a major step toward making spray-on solar cells easy and cheap to manufacture.

“My dream is that one day you’ll have two technicians with Ghostbusters backpacks come to your house and spray your roof,” said Kramer, a post-doctoral fellow with The Edward S. Rogers Sr. Department of Electrical & Computer Engineering at the University of Toronto and IBM Canada’s Research and Development Centre.

Solar-sensitive CQDs printed onto a flexible film could be used to coat all kinds of weirdly shaped surfaces, from patio furniture to an airplane’s wing. A surface the size of your car’s roof wrapped with CQD-coated film would produce enough energy to power three 100-Watt light bulbs—or 24 compact fluorescents.

He calls his system sprayLD, a play on the manufacturing process called ALD, short for atomic layer deposition, in which materials are laid down on a surface one atom-thickness at a time.

Until now, it was only possible to incorporate light-sensitive CQDs onto surfaces through batch processing—an inefficient, slow and expensive assembly-line approach to chemical coating. SprayLD blasts a liquid containing CQDs directly onto flexible surfaces, such as film or plastic, like printing a newspaper by applying ink onto a roll of paper. This roll-to-roll coating method makes incorporating solar cells into existing manufacturing processes much simpler. In two recent papers in the journals Advanced Materials and Applied Physics Letters, Kramer showed that the sprayLD method can be used on flexible materials without any major loss in solar-cell efficiency.

Kramer built his sprayLD device using parts that are readily available and rather affordable—he sourced a spray nozzle used in steel mills to cool steel with a fine mist of water, and a few regular air brushes from an art store.

Read more . . .  

 

The Latest on: Spray-on solar power

via  Bing News

 

Scientists Get to the Heart of Fool’s Gold as a Solar Material

University of Wisconsin-Madison Geology Museum This crystal of iron pyrite shows the characteristic cubic crystals of "fool's gold." A new study led by Song Jin at the University of Wisconsin-Madison identifies defects in pyrite's crystal structure as a critical obstacle to building commercial solar cells from the cheap and abundant iron pyrite material.

University of Wisconsin-Madison Geology Museum
This crystal of iron pyrite shows the characteristic cubic crystals of “fool’s gold.” A new study led by Song Jin at the University of Wisconsin-Madison identifies defects in pyrite’s crystal structure as a critical obstacle to building commercial solar cells from the cheap and abundant iron pyrite material.

As the installation of photovoltaic solar cells continues to accelerate, scientists are looking for inexpensive materials beyond the traditional silicon that can efficiently convert sunlight into electricity.

Theoretically, iron pyrite — a cheap compound that makes a common mineral known as fool’s gold — could do the job, but when it works at all, the conversion efficiency remains frustratingly low. Now, a University of Wisconsin-Madison research team explains why that is, in a discovery that suggests how improvements in this promising material could lead to inexpensive yet efficient solar cells.

“We think we now understand why pyrite hasn’t worked,” says chemistry Professor Song Jin, “and that provides the hope, based on our understanding, for figuring out how to make it work. This could be even more difficult, but exciting and rewarding.”

Although most commercial photovoltaic cells nowadays are based on silicon, the light-collecting film must be relatively thick and pure, which makes the production process costly and energy-intensive, says Jin.

A film of iron pyrite — a compound built of iron and sulfur atoms — could be 1,000 times thinner than silicon and still efficiently absorb sunlight.

Like silicon, iron and sulfur are common elements in the Earth’s crust, so solar cells made of iron pyrite could have a significant material cost advantage in large scale deployment. In fact, previous research that balanced factors like theoretical efficiency, materials availability, and extraction cost put iron pyrite at the top of the list of candidates for low-cost and large-scale photovoltaic materials.

Read more . . .  

 

The Latest on: Iron pyrite

via  Bing News