Solar power is getting much, much better. Now, a team of scientists has created the world’s most efficient nanostructured black silicon solar cell—which converts an impressive 22.1 percent of incident light into electricity.
The team, from Finland’s Aalto University and Universitat Politècnica de Catalunya, have smashed the existing record for such a cell by an amazing 4 percent. When a photon hit’s the surface of a PV cell, it causes a quantum reaction that spits out an electron. The researchers boosted the efficiency by adding a new layer to the back surface of the cell, which encourages those electrons to flow through as electricity rather than recombining with the photovoltaic materials at the surface. The results are published online in Nature Nanotechnology.
While black silicon solar cells don’t yet provide the highest efficiencies of PV solar cells, their deep black color makes them well-suited to generating electricity when the sun is low in the sky—as they absorb more light than other cells. “This is an advantage particularly in the north, where the sun shines from a low angle for a large part of the year,” explains Professor Hele Savin to PhysOrg. “We have demonstrated that in winter Helsinki, black cells generate considerably more electricity than traditional cells even though both cells have identical efficiency values.”
No PV cell can compare to what’s claimed to be the new most efficient solar power system, which manages a terrific 34 percent efficiency. But there’s still a place for PV cells, as they can be more easily positioned on buildings in built-up areas, unlike solar farms. Now, the team hopes to create the new black silicon solar cells at industrial scale.
Scientists everywhere are working on ways to increase the efficiency of solar panels, so here’s an idea out of Australia where a solar panel’s nano-scale indentations hold in sunlight in the way that Buddhist singing bowls hold in sound!
Using military technology and a zero-emission engine invented by a 19th-century Scot, Swedish firm seeks to revolutionise solar energy production
By: Jeffrey Barbee
A new solar electricity generation system that developers claim is the most efficient in the world, is being tested in South Africa’s Kalahari desert.
The Swedish company behind the project – which combines military technology with an idea developed by a 19th-century Scottish engineer and clergyman – says it is on the verge of building its first commercial installation.
In the remote Northern Cape province, huge mirrors reflect the sun across the brown Kalahari sand. This is the test site for Swedish company Ripasso, which is using the intense South African sun and local manufacturing know-how to develop their cutting-edge kit.
“Our whole team in South Africa has been hired locally, and our new systems have all been built with local South African labour. It works great,” says CEO Gunnar Larsson.
This is the only working small-scale concentrated solar energy system of its kind in the world. 34% of the sun’s energy hitting the mirrors is converted directly to grid-available electric power, compared to roughly half that for standard solar panels. Traditional photovoltaic panels are able to turn about 23% of the solar energy that strikes them into electricity, but this is cut to around 15% before it is usable by the grid.
Jean-Pierre Fourie is Ripasso’s South African site manager. His crew has been testing the system in the Kalahari under harsh desert conditions for four years. “What we hope is to become one of the biggest competitors for renewable energy in the world.”
The massive 100 square metre dishes slowly rotate, following the sun. Light clicks and taps fill the still desert air as they constantly adjust to capture the maximum solar energy.
Independent tests by IT Power in the UK confirm that a single Ripasso dish can generate 75 to 85 megawatt hours of electricity a year – enough to power 24 typical UK homes. To make the same amount of electricity by burning coal would mean releasing roughly 81 metric tonnes of CO2 into the atmosphere.
Paul Gauche, director of the Solar Thermal Energy Research Group at the University of Stellenbosch has visited the test site many times. “The technology looks good to me. I’ve seen it working and I believe it meets the efficiency goals. The technology is proven with years of performance in the navy.”
He points out that it will be crucial to keep costs low enough to compete with photovoltaics, a significant challenge as their price falls every year. The system is also limited in that it is only useful in areas with consistent bright sunshine.
The technology works by using the mirrors as giant lenses that focus the sun’s energy to a tiny hot point, which in turn drives a zero-emission Stirling engine.
The Stirling engine was developed by Reverend Robert Stirling in Edinburgh in 1816 as an alternative to the steam engine. It uses alternate heating and cooling of an enclosed gas to drive pistons, which turn a flywheel. Because of the material limitations at the time, the engine was not commercially developed until 1988, when Swedish defence contractor Kokums started making them for submarines.
Larsson worked in the Swedish defence industry for 20 years and realised what a clean and efficient generator could mean for renewable energy systems.
He wanted to bring the technology from the depths of the ocean into the sunshine, so he resigned as CEO of Kokums and licensed the technology to start Ripasso.
“When I founded the company in 2008 my youngest son came to me and said, wow daddy I am so proud of you, now I can tell everyone what you are doing, you are going to save the world instead of destroying it.”
The project has not been without its troubles. “Our major challenge over the last couple of years has been to get the technology accepted by the financing community, especially from the banks,” says Larsson.
Although banks have been unwilling to finance such novel technology, Ripasso has now secured private funding to begin their first large-scale installation. “We are very ready to head into the commercial phase,” says Larsson.
AllianceEarth.org paid for Jeff Barbee’s travel expenses.
By Duncan Geere
MIT invention takes top prize in desalination competition
There’s more than enough freshwater on Earth for humans to survive – but the problem is that it isn’t very well-distributed. Northerly and equatorial countries have loads of it, but those in between are growing increasingly parched.
To address this issue, the United States Agency for International Development launched a competition to create an affordable desalination system. Entrants were judged on three criteria – their designs had to be cost-effective, energy-efficient and environmentally sustainable.
The winners of this competition have now been announced, with a team from MIT taking home the $140,000 first prize. They created a system that uses solar panels to charge batteries, which then are used to draw dissolved salt particles (which have a slight electric charge) out of the water. As well as pulling out the salt, the team exposed the water to ultraviolet light – which destroys bacteria and makes it safer to drink.
Most desalination plants use a technique called reverse osmosis to remove salt – using high pressure pumps. But this is an inefficient method, wasting 40 percent of the water. With MIT’s method, just 5 percent of water is lost.
The team has built their technique into a single robust unit that can supply enough water every day to either irrigate a small farm or satisfy the drinking and cooking needs of up to 5,000 people. It’s powered exclusively by the sun.
While the unit has been tested extensively in the United States, it hasn’t yet been proved in the areas where it’s need the most. A pilot project, involving rural farmers in the areas where the US Agency for International Development operates, will be the next step.
By: Derek Markham
Small-scale wind generators, especially vertical designs, are the renewable energy pariahs, and the clean energy concept that many cleantech enthusiasts love to hate.
But that hasn’t stopped anyone from continuing to develop new versions of wind generators that break with the conventional windmill design, and the team behind the Vortex Bladeless design believes their creation is a leap forward in wind energy, and is a “more efficient, cost-effective, and environmentally friendly way to produce energy.”
I’ve previously covered other designs of bladeless wind turbines here on TreeHugger, with the comments mostly resembling that of Eeyore saying, “It’ll never work,” but like many innovations intended for established industries, that’s par for the course. That’s not to say that there aren’t any clean energy startups (or startups in general) that mislead the public about the claims of their products, or that there aren’t any scams or hoaxes in the green energy field, but rather that it’s easy to take a quick look and say something’s a scam, even if you’re only talking about a company that overpromises and underdelivers on its marketing claims.
The Vortex wind generator represents a fairly radical break with conventional wind turbine design, in that it has no spinning blades (or any moving parts to wear out at all), and looks like nothing more than a giant straw that oscillates in the wind. It works not by spinning in the wind, but by taking advantage of a phenomenon called vorticity, or the Kármán vortex street, which is a “repeating pattern of swirling vortices.”
Here’s a quick video overview of the device:
The company claims that its design can be reduce manufacturing costs by 53%, cut maintenance costs by 80%, and would represent a 40% reduction in both the carbon footprint and generation costs, when compared to conventional bladed wind turbines. The Vortex is also said to be quieter (than standard wind turbines), and to present a much lower risk to birds and the local environment.
According to Vortex, the devices can be used to generate more power in less space, because not only is the wind wake narrower than a traditional turbine, but installing them closer together can actually be beneficial to the technology, based on wind tunnel testing.
“We tested in a wind tunnel to put one Vortex just in front of another and the second one actually benefits from the vortices given off by the first structure.” – David Suriol, Vortex
The first model that Vortex will introduce is the Mini, a 4 kW unit that stands 12.5 meters in height, which is intended for small-scale and residential wind energy applications. Also in the works is a Gran version, a 1+ MW model that is designed for large-scale wind generation for utilities and other similar applications.
According to an interview in Renewable Energy Magazine, the company has already raised over 1 million Euros from both private and public funds in Europe, and is expected to roll out its pre-commercial prototype within the year.
The company’s website states that it will be launching a crowdfunding campaign in June of this year, although no other details about the goal of the campaign are listed on the site yet.