Offshore wind power, attractive for so many reasons but right now rather expensive, could get another notch in its plus column under an MIT scenario that calls for the addition of utility-scale storage literally under the turbines.
“Storage spheres” – giant concrete canisters – are the key to what the MIT researchers call the Ocean Renewable Energy Storage (ORES) system.
The idea is that when offshore turbines are producing more electricity than the grid needs – overnight or on weekends, for instance, when demand is slack – power would be used to pump seawater out of the hollow spheres placed at the seafloor beneath the turbines. When extra power is needed, the system would take advantage of hydrostatic pressure, opening up to suck water back into the spheres, with the water passing through a hydropower turbine to generate electricity.
According to an MIT release, “One such 25-meter sphere in 400-meter-deep water could store up to 6 megawatt-hours of power … that means that 1,000 such spheres could supply as much power as a nuclear plant for several hours — enough to make them a reliable source of power.”
Careful readers might have been struck by the water depth MIT is talking about for this concept: 400 meters is far deeper than anything employed now for offshore wind. Most turbines being installed in Europe these days – the only place in the world where offshore wind is yet of consequence – are in waters less than 30 meters deep. The MIT researchers say their system would need to operate in waters at least 200 meters deep to be ”economically feasible … with cost per megawatt-hour of storage dropping until 1500 meters before beginning to trend upward.”
The MIT researchers assume that their turbines would float – a not unreasonable assumption for the long-term. Floating turbines are an area getting solid R&D attention these days, as developers aim to operate in waters deeper than 50 meters, where they could take advantage of superior wind conditions, while also likely facing fewer conflicts.
The MIT researchers actually see their spheres – made of concrete, with three-meter thick walls and weighing “thousands of tons apiece” – doing double duty: storing energy, and anchoring the floating turbines.
As for the economics: the researchers say “preliminary estimates indicate that one such sphere could be built and deployed at a cost of about $12 million … with costs gradually coming down with experience. This could yield an estimated storage cost of about 6 cents per kilowatt-hour, a level considered viable by the utility industry.”
And what about the carbon-dioxide emissions from all that cement production? The researchers say they have that covered:
(T)he team calculated that the concrete for these spheres could be made, in part, using large quantities of fly ash from existing coal plants — material that would otherwise be a waste product — instead of cement. The researchers calculate that over the course of a decade of construction and deployment, the spheres could use much of the fly ash produced by U.S. coal plants, and create enough capacity to supply one-third of U.S. electricity needs.
This concept is detailed in a paper published in IEEE Transactions and co-authored by Alexander Slocum, the Pappalardo Professor of Mechanical Engineering at MIT; Brian Hodder, a researcher at the MIT Energy Initiative; and three MIT alumni and a former high school student who worked on the project.
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Top Renewable Energy Sources
Renewable energy made up 9 percent of all energy consumed in 2011, according to the <a href="http://www.eia.gov/">U.S. Energy Information Agency</a>, and that number is <a href="http://www.eia.gov/forecasts/aeo/er/pdf/0383er(2013).pdf">predicted to grow throughout the next decade</a>. Here's a breakdown of the top sources of renewable energy in the country, from wind to water and everything in between. <em>Information courtesy of the <a href="http://www.eia.gov/totalenergy/data/annual/perspectives.cfm">U.S. Energy Information Agency</a>.</em>
Solar Power - 2 Percent
Solar power and photovoltaic cells make up the smallest percentage of U.S. renewable energy production, but its future looks fairly promising. Warren Buffett's Berkshire Hathaway <a href="http://www.huffingtonpost.com/2013/01/03/warren-buffett-solar-power_n_2398816.html">invested $2.5 billion in Calif. solar company SunPower</a> earlier this year. Also, unlike other sources of renewables, energy can also be generated by small-scale solar installations (like on the rooftop of a home or business), and<a href="http://www.eia.gov/todayinenergy/detail.cfm?id=8570"> declining costs</a> have made solar much more affordable. <em>Information courtesy of the <a href="http://www.eia.gov/totalenergy/data/annual/perspectives.cfm">U.S. Energy Information Agency</a>.</em>
Geothermal - 2 Percent
Geothermal power captures naturally occurring heat from the earth to turn it into power. The renewable source is geographically dependent, <a href="http://www.eia.gov/todayinenergy/detail.cfm?id=3970">but the Western half of the U.S.</a> has many promising locations for power plants, <a href="http://www.geysers.com/">like The Geysers in Calif.</a>, the largest geothermal power plant in the world. The U.S. is the largest producer of geothermal power on the planet, but growth hasn't kept up with wind or solar development in recent years. <em>Information courtesy of the <a href="http://www.eia.gov/totalenergy/data/annual/perspectives.cfm">U.S. Energy Information Agency</a>.</em>
Waste - 5 Percent
Believe it or not, burned garbage accounts for 5 percent of all renewable energy created in the U.S. each year. More than 29 million tons of municipal solid waste was burned in 2010 to create steam to spin turbines and generate power, <a href="http://www.eia.gov/todayinenergy/detail.cfm?id=7990"> and there are more than 75</a> waste-to-energy plants in the country. Emissions regulations have been in place at waste incineration plants since the 1960s, but the <a href="http://www.epa.gov/ncer/publications/research_results_needs/combustionEmmissionsReport.pdf">EPA warned in a 2006 report that the toxins released</a> during the process could pose a serious environmental risk if not strictly enforced. <em>Information courtesy of the <a href="http://www.eia.gov/totalenergy/data/annual/perspectives.cfm">U.S. Energy Information Agency</a>.</em>
Wind - 13 Percent
The amount of wind power has grown for each of the past three years throughout the U.S. and accounted for the <a href="http://www.eia.gov/todayinenergy/detail.cfm?id=9931">largest growth in capacity</a> of any energy resource in the country last year. Wind turbines now supply more than <a href="http://www.reuters.com/article/2012/10/19/us-utilities-windpower-usa-idUSBRE89I0TX20121019">50,000 megawatts a year,</a> enough to power 13 million homes, according to Reuters. Federal tax credits, which were set to expire at the end of 2012, have made wind farms an attractive form of renewable energy. Congress <a href="http://www.forbes.com/sites/davelevitan/2013/01/02/wind-power-tax-credit-survives-fiscal-cliff-deal/">approved an extension of the credits</a> through the end of 2013. After production, wind turbines are net zero, meaning they require no energy and produce no emissions. The only problematic thing generated in some cases other than clean power has been <a href="http://www.huffingtonpost.com/2011/05/24/wind-power-noise-pollution-maine_n_866182.html">a whole lot of noise</a>. <em>Information courtesy of the <a href="http://www.eia.gov/totalenergy/data/annual/perspectives.cfm">U.S. Energy Information Agency</a>.</em>
Biofuel - 21 Percent
Biofuels, like ethanol, are created from organic matter like corn or soybeans. Gasoline in the U.S. contains 9 percent of the resource by federal mandate under the <a href="http://www.epa.gov/otaq/fuels/renewablefuels/index.htm">Renewable Fuel Standard program,</a> and more than <a href="http://www.huffingtonpost.com/2012/08/10/us-should-change-biofuel-_n_1764735.html">40 percent of the corn crop</a> last year was turned into biofuel. The resource is slightly more unstable than other renewables because it depends on the productivity of farms - <a href="http://www.huffingtonpost.com/2012/08/10/us-should-change-biofuel-_n_1764735.html">drought or other environmental problems</a> can significantly lower yields and increase prices. On average, <a href="http://www.afdc.energy.gov/vehicles/flexible_fuel_emissions.html">ethanol has 20 percent fewer emissions</a> than traditional gasoline but some types, like <a href="http://en.wikipedia.org/wiki/Cellulosic_ethanol">cellulosic ethanol,</a> cut greenhouse gas emissions more than 85 percent, according to the U.S. Department of Energy. <em>Information courtesy of the <a href="http://www.eia.gov/totalenergy/data/annual/perspectives.cfm">U.S. Energy Information Agency</a>.</em>
Wood - 22 Percent
Timber accounts for nearly a quarter of all renewable energy created in the country. <a href="http://news.nationalgeographic.com/news/energy/2012/10/121022-wood-for-heating/">Rising energy costs </a>have led to an upswing in wood burning over the past decade, and nearly <a href="http://www.eia.gov/forecasts/steo/report/winterfuels.cfm">20 percent of New England homes </a>use wood for heating, according to a National Geographic report. Although it may be a cheaper alternative, wood burning stoves and fireplaces<a href="http://www.epa.gov/burnwise/energyefficiency.html"> release more emissions of fine particles </a> than other home heating methods, according to the EPA. Burning <a href="http://www.epa.gov/burnwise/bestburn.html">good wood in an efficient burner</a> lowers toxic emissions and lost energy. Oh, and always have working smoke and carbon monoxide detectors handy. <em>Information courtesy of the <a href="http://www.eia.gov/totalenergy/data/annual/perspectives.cfm">U.S. Energy Information Agency</a>.</em>
Hydroelectric - 35 Percent
Almost all of the current hydroelectric power plants in the U.S. were <a href="http://www.eia.gov/energy_in_brief/article/hydropower.cfm">built before the mid-1970's</a>, but it's still the highest producing renewable energy source in the country. In 2011, 8 percent of all power created in the U.S. came from hydroelectric sources, but it's also one of the most geographically dependent sources of energy. The Pacific Northwest gets more than half of all power via hydroelectric due to prime geography. <em>Information courtesy of the <a href="http://www.eia.gov/totalenergy/data/annual/perspectives.cfm">U.S. Energy Information Agency</a>.</em>
How To Really Go Renewable
Watch this TED talk on the missing link in the future of renewable energy.