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Hot news in cleantech: Mining for geothermal, fusion find, solar cones

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In the quest to find new renewable energy solutions, a disused coal mine shaft might not seem like an obvious place to start. Luckily, some people – like the researchers at Canada’s McGill University – don’t deal in obvious; which brings us to a renewable energy concept that marries spent coal mines with geothermal power. And it goes a little something like this: flood the abandoned mine with water, let the surrounding rock heat it up, et voila – instant geothermal. According to CleanTechnica, the McGill researchers have estimated that geothermal energy from abandoned coal mines could serve about a million Canadians – not a massive amount in the big scheme of things, but enough to account for a decent portion of a local community’s power supply.

According to the McGill study’s lead author, Seyed Ali Ghoreishi Madiseh, it’s about more than just energy. “Abandoned mines demand costly perpetual monitoring and remediating. Geothermal use of the mine will offset these costs and help the mining industry to become more sustainable.” And it looks like there might be potential in strip mines as well as shaft mines, with a Purdue University (Indiana) study recently mapping the geothermal potential of both types in the southwest part of the state. The key, apparently, is to identify sites where underground water could be easily exchanged with surface water. Parts of Ohio, Pennsylvania and West Virginia are also emerging as potential geothermal coal mine hotspots. (And, as an addendum, Greenearth Energy in Australia has nominated cement company Holcim’s quarry at Moriac, about  8.5 km north-northwest  of the Alcoa brown coal-fired power station at Anglesea, Victoria, to be the site of its proposed geothermal demonstration plant).

Clearing fusion confusion

Nuclear fusion, while regarded by some as the ultimate clean energy source, is still considered by most to be some decades away from making it out of the lab. As Technology Review‘s Kevin Bullis writes, one of the  reasons for this is that “physicists don’t completely understand what’s going on in the high-temperature plasma inside a reactor.” But this week, a new theory developed by researchers at the US DoE’s Princeton Plasma Physics Laboratory (PPPL) may have come up with an explanation to help engineers design better reactors, says Bullis. “And that might help them increase the power output of a reactor, perhaps doubling the electricity they could produce, and making fusion reactors more economical.”

How? Bullis explains: “Based on experiments, there is a practical limit to how dense the plasma in a reactor can be.” Beyond a certain density, it becomes unstable, dissipates its energy, and disappears. Because researchers don’t understand exactly why this happens, it’s difficult to predict the collapse, so researchers avoid getting close to that limit in experimental reactors. The new research allows engineers to better predict what will happen in the reactor, which might then allow them to design reactors that get closer to an optimum density for the plasma. That, in turn, could increase the amount of power a fusion power plant could generate, says Bullis.

According to the researchers’ theory, islands develop within the plasma that cool and cause the plasma to disappear. It’s thought that these islands could be selectively heated with microwaves, which could keep the plasma stable. The hope is that the team at PPPL – led by David Gates – will be able to test the theory in research reactors this year. But whether this will bring the advent of fusion energy any closer remains to be seen. Researchers still need to solve many practical problems before optimising energy density is even an issue, says MIT fusion researcher Martin Greenwald. Ultimately, solving these problems will require a combination of better theories, more computing power, better algorithms, and big experiments. Like we said: decades.

Solar cones

The quest to make solar PV more efficient is never-ending. And this week’s contributor to the cause is Solarphasec, with its 3D Spin Cell Generators. CleanTechnica reports that the California-based company – which has a branch in Melbourne, Australia – claims its conical solar technology can generate 40 per cent more power throughout the course of the day than regular PV panels, with 60 per cent more gain during the course of the year. Here’s how Solarphasec explain it: “This technology introduces a conic form factor which allows for a larger photovoltaic surface area for a given footprint. This in turn leads to an exponential increase in active area as the Solarphasec system footprint increases. The conic form factor also essentially eliminates the concern of modules shadowing adjacent modules as is the case with ground mounted flat solar panel arrays. Additionally, the conic form factor significantly reduces wind load, allowing for large scale, high power commercial rooftop deployment.”

The efficiency of the technology is also boosted by the proprietary electromechanical function of the system, which increases the efficiency of the photovoltaic cells deployed in the system leading to significantly higher output power compared to an equivalent footprint of a standard solar panel, says CleanTechnica. “The proprietary electromechanical function is designed to provide alternating current output for electrical distribution without the need for inverter equipment normally required to modify the direct current output from the photovoltaic cells. This is a significant design issue as inverters cause an efficiency loss and currently cost $0.70/watt of the total installed system cost of approximately $7.00/watt.”

One idea the company is work-shopping for the solar cone is to put them atop power poles or lamp posts. “The 17 kW Power pole serves as an art form with the ability to produce 17,000 watts in a 3 square meter footprint,” says the website. Solarspheric opened a new funding round in February. It aims to raise $3.5 million to fund set-up costs “associated with the full-scale commercial production of its Sentinel Spin Cell range.”

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