By Sebastian Anthony
MIT is reporting that it has created a new, cheap material — using a microwave, no less — that converts sunlight into steam with an amazing 85% efficiency. This could have major repercussions in the realms of desalination and sterilization, and perhaps for concentrated solar thermal power generation as well.
The new material, developed by MIT mechanical engineer Hadi Ghasemi, consists of a thin double-layered disc. The bottom layer consists of spongy carbon foam that doubles up as a flotation device and a thermal insulator that prevents solar energy from dissipating into the fluid underneath. The top layer — the active layer — consists of flakes of graphite that were exfoliated using a microwave. The microwave causes the graphite to bubble up “just like popcorn” according to Gang Chen, another researcher involved with the work.
When sunlight hits the graphite, hot spots are created that draw water up through the carbon foam via capillary action. When the water reaches the hot spots in the graphite, there’s enough heat to turn the water into steam. The efficiency of the material is linked to the amount of incoming light — at a solar concentration (intensity) of 10 times that of a typical sunny day, 85% of incoming solar energy is converted into steam (assuming there’s enough water nearby; this doesn’t magically create steam out of thin air). “There can be different combinations of materials that can be used in these two layers that can lead to higher efficiencies at lower concentrations,” says Ghasemi. Graphene, anyone?
As for what this little spongy steam-maker might actually be used for, there’s a variety of possibilities. The low solar intensity requirement (10x is easy to obtain with a simple lens or reflector) means this could a very good way of producing clean water or sterilizing equipment (to this day, steam is still a very popular way of sterilizing things). Bulk desalination is another possibility, though we wonder if the carbon foam wouldn’t get clogged up with the leftover salt crystals.
And then there’s the most exciting possibility: Good ol’ power generation. In modern-day concentrated solar thermal power generation, fresnel lenses or parabolic reflectors are used to concentrate sunlight by up to 1,000 times. If steam can be produced with just the intensity of 10 suns, then system costs can probably be reduced and overall efficiency increased. A lot more work needs to be done before this stuff revolutionizes power generation, though: So far, though, MIT hasn’t gone any further than “ooh, this stuff produces steam!” As we mentioned before with regards to desalination, it’s very likely that this new material would clog up with mineral deposits rather quickly (i.e. fouling), completely destroying any semblance of efficiency.
Still, it’s clearly early days. Problems like fouling (limescale! corrosion!) have been around forever, and as such there are lots of ways to combat it. If MIT really has stumbled across a way of cheaply and easily producing steam from sunlight, then this could be big news.
NORFOLK, Va. (WAVY) – Old Dominion University and Dominion Virginia Power picked a sunny July day to dedicate a massive solar grid at the school.
The solar panel project now sits atop the roof of ODU’s student recreation center.
“It was just a great opportunity for us to partner, and a logical one, Dominion and Old Dominion to take a look at how we could expand solar opportunities here on campus and tie into what they’re trying to do in terms of growing that energy as well,” said ODU President John R. Broderick.
ODU is no stranger to solar power. Last year, solar panels were assembled on a rotating grid on the roof of Kaufman Hall. That project had 24 solar panels, which could power about two home. This latest array has more than 600.
Ken Barker, with Dominion Virginia Power, says ODU was a perfect partner for the project. “We’ve installed enough panels to power about thirty homes here on the roof of Old Dominion. That power will go back on our grid and we’ll use it as a demonstration of understanding how solar energy can fit into our electric grid at Dominion Virginia Power.”
Dr. Sylvain Marsillac, who oversaw the construction of last year’s project, has high hopes this new solar panel project is a stepping stone for powering America’s future energy needs. “It will be the future, you have to go through renewable energy, there’s no other way around, just because your gas and your oil will run out at a point. Fifty years or seventy years, it will run out; the sun will never run out.”
As part of Dominion’s solar partnership program, the facility will power about 31 homes during daylight hours.
By Katherine Tweed
Workers carry a damaged photovoltaic solar panel at a Gujarat solar park under construction in April 2012.
India recently committed millions of dollars to solar power and grid improvements in an effort to provide electricity to more homes, according to Bloomberg.
Prime Minister Narendra Modi’s government will spend 15 billion rupees (US$ 250 million) to increase solar power across the country and also to improve power delivery. Nearly 40 percent of India’s 1.2 billion people have no access to reliable electricity.
Two-thirds of the funds would go to various types of solar power projects. About $83 million would go to large solar power plants, and another $67 million would go towards 100,000 solar-powered irrigation pumps.
The investment in the pumps is just a fraction of the 26 million groundwater pumps that the Indian government wants to replace with more efficient solar-powered pumps. The power used for pumping irrigation water is also one of the largest strains on the Indian power grid. Earlier this year, Bloomberg reported the cost of 200 000 pumps would be $1.6 billion.
The government also recommitted to providing 24/7 power supply to all homes with an $83 million investment in feeder systems to bring electricity to rural areas. The program would mirror one that Modi instituted in its home state of Gujarat, according to Bloomberg.
In Gujarat, power feeder lines for farmers, which have substantial power needs, were separated from those that go to homes and villages. That allowed the state to provide more reliable electricity to most areas while also limiting the amount of subsidized power provided to farmers.
Some industry analysts question whether the budget allocation for this project would make a significant impact. Kameswara Rao, head of energy, utilities, and mining in India for PricewaterhouseCoopers LLP told Bloomberg that the funding needed to split off rural electricity supply was far larger than budgeted.
The efforts “are directionally correct but involve relatively small steps or lack specifics to support a meaningful improvement in the short-term,” credit rating agency Fitch Ratings said of the investment for India’s power sector. “There are entrenched structural issues affecting the performance of the power sector of India and the solution would require a sustained and disciplined policy focus.”
While India’s power sector suffers from an inadequate grid, there are also generation shortfalls that will not be helped by the funds committed to solar power and distribution upgrades. Fitch Ratings notes that there is a domestic shortfall for both coal and gas for power plants.
“The entire ecosystem of the power sector – from generation to distribution – needs to be strengthened,” Fitch analysts wrote.
Environmentalists were not pleased with the budget, calling for more distributed generation, rather than investment in large-scale solar plants and a continued reliance on coal that is fed into an inefficient grid.
“The steps on renewable energy and energy efficiency are not transformational,” Vinuta Gopal, head of climate and energy at Greenpeace India, told Reuters, “and the attempt to force fit coal production to clear the irrational power proposals is a signal that the reality of climate change has far from been recognized by this government.”
By Sarah Zhang
Weather is annoyingly fickle, and so is the wind. If massive offshore wind farms are going to become reality, we need better ways to store the extra energy from windy days for the windless ones. One a bizarre-sounding idea floating around: giant balloons of compressed air stored deep underwater.
Like many good ideas, the seeds of compressed-air energy storage, or CAES, were sowed long ago, in the 1870s. Today, a handful of operations store energy as compressed air in sealed-off caves or pipe systems. But that’s all on land. Bringing CAES deep underwater, where water pressure naturally keeps air compressed, is a novel and tantalizing idea for the massive offshore wind farms of the future.
In August, IEEE Spectrum reports, the Toronto-based Hydrostor will make the first commercial deployment of underwater CAES technology. It’ll use electricity to fill several balloon-like bags tethered to the bottom of Lake Ontario with compressed air. To turn that stored air back into electricity, they’ll run the compressed air through a turboexpander.
Proponents of CAES have their sights set on grand scales. Maxim de Jong, CEO of Thin Red Line Aerospace—a company that also makes the energy bags—recently calculated how underwater CAES would be used to store energy from the London Array, currently the largest offshore wind array in the world. One day’s worth of energy from the array would require 812,000 cubic meters of compressed air, or a whopping 27,500 of his company’s five-meter diameter balloons. If we made much bigger balloons, say 41 meters in diameter, de Jong calculates you’d only need 23 of them.
De Jong tells IEEE Spectrum his calculations are meant to provoke us into thinking about underwater CAES, which will have to be deployed at pretty massive scales. The UK recently approved a new offshore wind farm that will be twice the size of the London Array. As wind energy projects get ever more ambitious, the infrastructure that support them will need ambitious ideas, too.