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MIT Wind Power Storage

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One of the problems with wind power is that when there is no wind then there is no power. Offshore wind could provide abundant electricity — but as with solar energy, this power supply can be intermittent and unpredictable. A new approach from researchers at MIT could mitigate that problem, allowing the electricity generated by floating wind farms to be stored and then used, on demand, whenever it’s needed.

The key to this concept is the placement of huge concrete spheres on the seafloor under the wind turbines. These structures, weighing thousands of tons apiece, could serve both as anchors to moor the floating turbines and as a means of storing the energy they produce.

Pumped-storage hydroelectricity or other forms of grid energy storage can store energy developed by high-wind periods and release it when needed. The type of storage needed depends on the wind penetration level — low penetration requires daily storage, and high penetration requires both short and long term storage — as long as a month or more. Stored energy increases the economic value of wind energy since it can be shifted to displace higher cost generation during peak demand periods. Although pumped storage power systems are only about 75% efficient, and have high installation costs, their low running costs and ability to reduce the required electrical base-load can save both fuel and total electrical generation costs.

Whenever the wind turbines produce more power than is needed, that power would be diverted to drive a pump attached to the underwater structure, pumping seawater from a 30-meter-diameter hollow sphere. (For comparison, the tank’s diameter is about that of MIT’s Great Dome, or of the dome atop the U.S. Capitol.) Later, when power is needed, water would be allowed to flow back into the sphere through a turbine attached to a generator, and the resulting electricity sent back to shore.

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One such 25-meter sphere in 400-meter-deep water could store up to 6 megawatt-hours of power, the MIT researchers have calculated; 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. The 1,000 wind turbines that the spheres could anchor could, on average, replace a conventional on-shore coal or nuclear plant. What’s more, unlike nuclear or coal-fired plants, which take hours to ramp up, this energy source could be made available within minutes, and then taken offline just as quickly.

The system would be grid-connected, so the spheres could also be used to store energy from other sources, including solar arrays on shore, or from base-load power plants, which operate most efficiently at steady levels. This could potentially reduce reliance on peak-power plants, which typically operate less efficiently.

The weight of the concrete in the spheres’ 3-meter-thick walls would be sufficient to keep the structures on the seafloor even when empty, they say. The spheres could be cast on land and then towed out to sea on a specially built barge. (No existing vessel has the capacity to deploy such a large load.)

Preliminary estimates indicate that one such sphere could be built and deployed at a cost of about $12 million, Hodder says, 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. Hundreds of spheres could be deployed as part of a far-offshore installation of hundreds of floating wind turbines, the researchers say.

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In combination, floating turbines and undersea storage spheres could provide reliable, on-demand power, except during extended calm periods. Meanwhile, a siting many miles offshore would provide the benefit of stronger winds than most onshore sites, while also operating out of sight of the mainland. “It provides a lot of flexibility in siting,” Hodder, a researcher at the MIT Energy Initiative, says. The team calculated that the optimal depth for the spheres would be about 750 meters, though as costs are reduced over time they could become cost-effective in shallower water.

Slocum and some of his students built a 30-inch-diameter prototype in 2011, which functioned well through charging and discharging cycles, demonstrating the feasibility of the idea.

The team hopes to extend its testing to a 3-meter sphere, and then scale up to a 10-meter version to be tested in an undersea environment, if funding becomes available. MIT has filed for a patent on the system.

The researchers estimate that an offshore wind farm paired with such storage spheres would use an amount of concrete comparable to that used to build the Hoover Dam — but would also supply a comparable amount of power.

While cement production is a major source of carbon-dioxide emissions, the 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.

For further information see Wind Power Storage.

SOURCE



Cigarette Butts Litter Waterways, Create Toxic Aquatic Ecosystems

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What would you say is the most littered item on US roadways? I think of two things: gum and cigarette butts. But let’s focus on cigarettes for now.

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Cigarette filters are made from cellulose acetate, a plastic which is technically biodegradable. However, cigarette butts only degrade under conditions described by researchers as “severe biological circumstances,” such as when filters end up in sewage.

Even under optimal conditions, it can take at least 9 months for a butt to degrade.
And even though these filters are only an inch long, with over 360 billion cigarettes being consumed in the United States (according to a 2007 estimate), cigarette remnants are bound to end up in our natural environments and public spaces.

A new survey conducted by Legacy, an organization committed to public education of tobacco products, evaluates Americans’ attitudes on the issue, their own littering behaviors, and whether survey respondents consider cigarette butts to be an environmental concern.

Some of the key findings include:

- More than 88 percent of Americans surveyed think that cigarette butts are an environmental concern, however, more than 44 percent of those polled who had ever smoked admit to having dropped a cigarette on the ground and nearly 32 percent have dropped a cigarette out of a car window.

- Over the prior 30 days, Americans surveyed reported seeing cigarette butts on sidewalks (80.1 percent), in parks (32.1 percent), on playgrounds (16.6 percent) and on beaches (15.7 percent).

- While more than 93 percent of those surveyed agree that dropping a cigarette butt on the ground is a form of littering, many smokers still litter them.

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Cigarette butts are in fact toxic waste. Not only are these small stubs an eyesore, but they can also leach toxic chemicals and carcinogens into the environment, poisoning wildlife and contaminating waterways. Environmental cleanup reports also find that cigarette butts are the No. 1 littered item found on beaches and waterways worldwide.

Data from the Ocean Conservancy shows that in 2010, over one million cigarettes or cigarette filters were removed from American beaches and inland waterways as part of the annual International Coastal Cleanup (ICC). This represents about 31% of the total debris items collected and by far the most prevalent item found.

As studies start to show how the toxicity of cigarette butts in aquatic ecosystems affect wildlife, more actions will need to be taken by municipalities and government organizations in order to prevent cigarette littering in their parks and beaches.



How Fast is Global Climate Changing?

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There’s plenty of evidence that the climate has warmed up over the past century, and climate scientists know this has happened throughout the history of the planet. But they want to know more about how this warming is different.

Now a research team says it has some new answers. It has put together a record of global temperatures going back to the end of the last ice age — about 11,000 years ago — when mammoths and saber-tooth cats roamed the planet. The study confirms that what we’re seeing now is unprecedented.

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What the researchers did is peer into the past. They read ice cores from polar regions that show what temperatures were like over hundreds of thousands of years. But those only reveal changes in those specific regions; cores aren’t so good at depicting what happened to the whole planet. Tree rings give a more global record of temperatures, but only back about 2,000 years.

Shaun Marcott, a geologist at Oregon State University, says “global temperatures are warmer than about 75 percent of anything we’ve seen over the last 11,000 years or so.” The other way to look at that is, 25 percent of the time since the last ice age, it’s been warmer than now.

You might think, so what’s to worry about? But Marcott says the record shows just how unusual our current warming is. “It’s really the rates of change here that’s amazing and atypical,” he says. Essentially, it’s warming up superfast.



Concord, Mass. US First City to Ban Plastic Water Bottles

It has taken a few years for the ban to take effect, but as of January 1st 2013, Concord became among the first U.S. communities to ban single-serving plastic water bottles.

Water bottles might seem like a small thing, but according to Ban the Bottle:

“It takes 17 million barrels of oil per year to make all the plastic water bottles used in the U.S. alone. That’s enough oil to fuel 1.3 million cars for a year.” Their website also states: “In 2007, Americans consumed over 50 billion single serve bottles of water. With a recycling rate of only 23%, over 38 billion bottles end up in landfills.”

And it’s not like bottled water is a good deal for your wallet either:

“The recommended eight glasses of water a day, at U.S. tap rates equals about $.49 per year; that same amount of bottled water is about $1,400.”

Hopefully this is the beginning of a larger movement that will return bottled water to what it should have stayed: An emergency thing, when you really need water but can’t get it any other way. It’s ridiculous that it has become an everyday thing for so many people that have access to perfectly fine water for a fraction of the price from their tap (and there are so many great filtering systems out there for those who want to make extra sure — though it’s not like bottled water can’t be contaminated either).