You wouldn’t recognize the forerunner of the modern solar panel if you saw one, and who knows what they’ll look like in the future?
The precursor to the first solar panel wasn’t really a panel, and it didn’t even use sunlight. But the physical processes first observed in selenium rods by the French scientist Antoine César Becquerel in his laboratory in 1839, and later by Willoughby Smith when testing telegraph cables to be sunk under the Atlantic Ocean, are essentially the same as those occurring in solar cells everywhere. today.
In short: light hits a semiconductor material, then creates an electric current – no moving parts, no steam, no turbines.
The first true solar cell prototype was created in 1883 by New York inventor Charles Fritts—who, by the way, also worked with clock springs, shutter devices, and train-car clutches (oh, 19th-century inventor!) a thin layer of selenium with gold leaf spread over a metal plate covered with a layer so thin it was almost transparent. Less than 1% of the light energy absorbed by this first solar cell was converted into electricity – a fact that did not escape the attention of many engineers, physicists and entrepreneurs of the time who were newly enamored with the promise of coal-fired turbines. .
Fast forward through the years…
Solar panels are used everywhere on roofs. Credit: Newstead/Getty Images
We travel from 1905 to the famous Albert Einstein who published the physics behind the photoelectric effect (it’s all in the name), to the introduction of the copper oxide solar cell in 1927 and finally to 1941 when silicon illuminated the future of the sun. cells significantly. Over the next decade—helped significantly by the advent of transistors—the 1% power conversion impasse was finally overcome. Energy conversion rates rose to 6% and then to around 20% in the late 1980s – about what you can expect from the average rooftop panel (an array of solar cells) today.
Well, the ones we put on the roofs, anyway.
No doubt there are a few of them around you adorning homes, supermarkets and solar farms.
They were installed on the White House roof by then-President Jimmy Carter in 1979 before Ronald Reagan came along and shut down renewable energy for the next few decades.
Jimmy Carter installed solar panels on the roof of the White House. Credit: Jimmy Carter Presidential Library
These roof-type panels are made up of silicon-based cells, University of Adelaide chemistry researcher Dr. Cameron Shearer explains. “They consist of two types of silicone. One is very good at carrying electrons and the other is very good at carrying holes (or the absence of electrons). When the light is absorbed, the electrons start to move and create a current.
The second type of solar cell is typically found in space applications—spacecraft, satellites, and space observatories—where weight and efficiency considerations dominate. These absorb many different light energies from the Sun – not just visible light – making them more efficient (energy conversion is closer to 48%), but the materials used are more expensive.
Our energy needs
In 2021, a total of 1032.5 TWh (terawatt-hours) of solar energy was produced globally. Of this, 31.19 TWh was produced by Australia, which has plenty of sunshine and open space. Comparing this to the total global energy production of 28,214 TWh from all energy sources in 2021, and taking into account the average amount of sunlight reaching Central Australia, the area of solar panels needed to produce the electricity used for the entire world in 2021 is 55,000 km2 A touch more than , Shearer reckons. This is about 80% of the state of Tasmania, or slightly less than the area of Croatia.
World map showing the amount of solar energy received by global location. Credit: World Bank Group/ESMAP/Solargis/http://globalsolaratlas.info
Approximately 340,000 km2 of land is required to produce the 13,340 TWh of energy consumed globally in 2021 (including non-electric energy sources such as diesel, gasoline and other fuels). That sounds like a lot, but the area covered by deserts within Australia alone is about 2.7 million km2, and that’s to say nothing of the area covered by suitable roofs.
However, according to the International Roadmap for Pholtovoltaic, the world needs to generate more than 60 TWh of energy through solar power to reach net zero emissions.
There are currently several bottlenecks with solar energy.
The first is the same problem as 150 years ago: efficiency. Current rooftop solar cells are limited by the material they are made of, namely silicon. The energy conversion efficiency of a given solar cell is limited by the Shockley Quiesser limit, which takes into account how well the material absorbs energy and how much energy it loses during the entire process. For silicon, at absolute zero, the energy conversion efficiency is 33%, but in real-world conditions it is about 29%.
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There is hope to improve the efficiency of rooftop solar cells, both in the panel design and in the solar cell itself.
Solar panels consist of many solar cells connected together, which leads to dead spots and energy losses in the connections, so no matter how careful the design, the panels will inevitably have some inefficiency.
New solar cell technology
One of the most promising materials the researchers are working with is perovskites, a class of mineral structures, Shearer explains. The most promising is lead halide, and when combined with silicon in tandem solar cells, it has been shown in laboratories to have 31.25% energy conversion efficiency.
Before you say, “That’s not much,” the average energy efficiency of a coal-fired power plant in the United States is about 33%.
Illustration of the idealized atomic structure of a single perovskite cell with the chemical formula ABX3, where A and B are two metal cations (shown here in pink and green), and X is typically an oxide ion (shown here in orange). Credit: Nanoclustering/Science Photo Library/Getty Images
Perovskite on silicon layers may be the way of the future for solar cells. Perovskite tends to work better with high-energy visible light (wavelengths that appear bluer to us), while silicon tends to work better at lower energy or redder wavelengths. The perovskite can also be tuned to absorb specific colors (i.e. red, green and blue) by changing its chemistry, meaning that if arranged sensibly, tuned stacks of perovskite and silicon can even drive an entire assembled cell to over 50% efficiency.
There are other materials that can be used, which you can read more about here.
Interviewed in the Sydney Graduate Journal, Professor Anita Ho-Baillie works with perovskites and is delighted with the progress. “It took 40 years for people to double the efficiency of silicon,” he says. “Perovskite caught up with silicon in just 10 years.”
Moreover, perovskite can be printed, which makes the manufacturing process much faster. trying to make them more resistant to degradation and suitable for commercial use. “It’s easier to handle than silicone,” says Ho-Baillie. “It took me four weeks to make a silicon cell in the laboratory. It only takes two days with perovskite.”
Read more: Another promising material in solar cell development is conductive organic polymers
Solar panels should also collect as much light as possible. Usually this means tracking the Sun and moving the panels through the machine. Recently, a team from Stanford University in the US produced a device that collects and concentrates sunlight, eliminating the need to constantly move the panels. Fewer moving parts increases the longevity of such systems.
The issue of waste and resource management is a serious concern. “Although the raw materials required – silicon, silver, glass and plastic – are not rare, it is easier to mass-produce solar cells from sand than from old solar cells,” says Shearer. But there are companies in Australia harnessing the commercial potential of solar cell recycling, and even an aluminum frame is part of the conversation.
Energy storage from solar cells
Ultimately, one of the biggest advances we expect to see in this space over the next decade is less about using solar cells and more about storing and using energy from them and other renewable energy sources. claims can be paid outside of production hours.
Large lithium-ion batteries, such as the 100 megawatt Tesla attached to the Hornsdale Wind Farm in mid-north South Australia, are a development from the last decade to support renewable energy.
Tesla Powerpack battery at Hornsdale Wind Farm in Adelaide, Australia. Credit: Mark Brake/Getty Images
Many Adelaide residents, including Shearer, are also connected to the ‘virtual power station’.
This means that the solar panels on its roof periodically feed the grid. But, as Shearer explains, “battery storage is generally very heavy, and we only need electricity to power things other than our home or our grid, such as long-distance transportation or heavy industry.”
Shearer’s own research focused on storing energy in another way—using the energy to split water into its components: hydrogen and oxygen. “When they recombine, they form water and release energy,” he says, noting that the hydrogen can then be used as a fuel. “It’s a completely renewable process with no carbon emissions at any stage.” According to Shearer, the future of renewable energy and solar cells in particular is bright. As we move toward a carbon-neutral future, he says, “we’re going to see the benefits of having our own solar panels, our own batteries.” With advances in solar cells and other renewable sources, plus technology like batteries and other methods of storing the chemical energy created to support them, the next decade or two may look very different than the last few years — and certainly different from 150 years ago. .