<p class=”item-title”>Rooftop Wind Power
If you want to provide off-the-grid power for your own home, there’s only been one solution: solar panels. Wind power is usually deployed on a utility-scale, in vast farms of mighty turbines that feed directly into the grid. That’s a scale that helps explains why more than 10,000 MW of wind power were installed in the U.S. in 2009. Solar has always been the choice for homeowners who want to stop paying electricity bills and start generating their own juice.
But if wind can do big, it can also do small — and it does rooftops as well. The startup Windtronics is developing mini-wind turbines that can be installed on any flat root, either alone or in larger arrays. Each turbine measures about 6 ft. in diameter and looks like a large, circular window fan, but it can generate an average of 1,500 KW/h a year, with more or less depending on wind strength. And unlike utility-scale turbines, the Windtronic turbine contains no rotating gearbox to generate electricity, and is thus much quieter. In an ordinary wind turbine, the blades moves the gears, the gears turn a generator, and the generator creates electricity. With a Windtronics model, the blades are equipped with magnets at the tips and are enclosed in a wheel that contains coiled copper, so the entire turbine is an electric generator. That makes the Windtronics turbine silent — something your neighbors will appreciate.
It’s a dirty secret: the biggest renewable energy business in the U.S. isn’t solar or wind or electric cars. It’s plain old corn ethanol. Thanks largely to generous government subsidies, the U.S. produced 10.6 billion gallons of ethanol in 2009. That was enough to displace the need for 364 million barrels of oil, but study after study has shown that high levels of corn ethanol production simply aren’t sustainable. Corn that could go to feed the world instead feeds our cars — and not very efficiently. The growth of corn ethanol has more to do with political realities in the U.S. (think Iowa, home of both corn and the first Presidential caucus) than it does with environmental ones.
But that doesn’t mean biofuels can’t play a major role in a greener U.S. energy policy — they just have to be the right kind. One of the best options on the horizon is biofuel made from algae, which counters a lot of the problems with corn ethanol. (The right strains of algae secrete oils that can be used to make fuel.) Algae do not need farmland to grow: tanks will do the job just fine anywhere there is spare land and a decent amount of sunshine. Algae also grow much faster than traditional crops, and the micro-organisms may be able to use to use wastewater or even saline water during their development, rather than fresh water. Startups like Sapphire Energy and Algenol in California and Florida are passing the pilot phase and nearing commercial development; they just need a little government help.
Molten Salt Storage
Renewable energy has many advantages, as environmentalists won’t hesitate to tell you. There’s no need to pay for fuel since the wind and the sun are free, and that saves utilities from the price spikes seen in coal, natural gas, oil and nuclear. But wind and solar face one major problem: intermittency. When the wind doesn’t blow and the sun doesn’t shine, turbines and silicon panels aren’t producing electricity, and there’s no way to store the electricity they do produce during peak times if it’s not being used. That’s a serious obstacles since utilities, often by law, need to provide enough electricity to meet demand at all times.
But utility-scale solar companies are working on ways to store the energy they produce during the brightest days. One option: molten salt. It can be used in solar thermal, which employs powerful mirrors to focus the sun’s heat to create steam, driving an electric turbine. The surplus heat produced during the day can be used to warm up massive amounts of salt, which can absorb significant amounts of heat. When the sun goes down — or when it’s simply cloudy — that heat can be used to generate steam and run an electric turbine. It’s not perfect, but it’s the best battery that’s been developed yet for utility-scale solar.
Sometimes high tech can start out low tech. Fuel cells are an old and basic technology; they generate electricity within a cell through the reaction of a fuel and an oxidant. Essentially they’re a kind of chemical battery, and your average high school chemistry class can make one. Unlike batteries, however, they can’t store electricity; you need an outside fuel source that has to be replenished over time. But their simplicity has also made them useful for certain purposes; NASA has long used hydrogen fuel cells to power its spacecraft.
Inventors have tried to use hydrogen fuel cells as a cleaner way to create electricity commercially. Honda and other car companies have made hydrogen fuel cell-powered cars, for example, but they’ve always been limited by the cost. That’s beginning to change, however, thanks to a California startup called Bloom Energy. The company exploded onto the public scene earlier this year with the release of its Bloom Box, a system that uses fuel cell technology to provide off-the-grid power. The Bloom Boxes — about half the size of a shipping container — use solid oxide fuel cells, which generate electricity by oxidizing natural gas. The technology has existed for awhile, but Bloom figured out how to carry out the reaction at a relatively low temperature, making the Bloom Boxes safe to use in corporate offices — which is exactly where they’re being put to work now, by companies like Google and eBay that can use the lower carbon power as an off-the-grid back up to conventional grid electricity and as a way to reduce their own carbon footprint.