Solar Energy: New Sunflower-Inspired Pattern Increases Concentrated Solar Efficiency

Solar Energy: New Sunflower-Inspired Pattern Increases Concentrated Solar Efficiency

Just outside Seville, in the desert region of Andalucia, Spain, sits an oasis-like sight: a 100-meter-high pillar surrounded by rows of giant mirrors rippling outward. More than 600 of these mirrors, each the size of half a tennis court, track the sun throughout the day, concentrating its rays on the central tower, where the sun’s heat is converted to electricity — enough to power 6,000 homes.

The sprawling site, named PS10, is among a handful of concentrated solar power (CSP) plants in the world, although that number is expected to grow. CSP proponents say the technology could potentially generate enough clean, renewable energy to power the entire United States, provided two factors are in ample supply: land and sunlight.

Now researchers at MIT, in collaboration with RWTH Aachen University in Germany, have come up with a design that reduces the amount of land required to build a CSP plant, while increasing the amount of sunlight its mirrors collect. The researchers found that by rearranging the mirrors, or heliostats, in a pattern similar to the spirals on the face of a sunflower, they could reduce the pattern’s “footprint” by 20 percent and increase its potential energy generation. The sunflower-inspired pattern allows for a more compact layout, and minimizes heliostat shading and blocking by neighboring mirrors.

The researchers published their results in the journal Solar Energy, and have recently filed for patent protection.

Blocking a shadow

At PS10 and other CSP plants in the world, mirrors are arranged around the central tower in concentric circles. The spacing between mirrors is similar to the seats in a movie theater, staggered so that every other row is aligned. However, this pattern results in higher-than-necessary shadowing and blocking throughout the day, reducing the reflection of light from mirrors to the tower.

The MIT team looked to optimize the pattern to increase a plant’s overall efficiency. Alexander Mitsos, the Rockwell International Assistant Professor of Mechanical Engineering, and Corey Noone SM ’11 collaborated with Manuel Torrilhon of RWTH Aachen, where Mitsos was a researcher prior to joining the MIT faculty.

Mitsos’ lab developed a computational model to evaluate the efficiency of heliostat layouts. The model divides each mirror into discrete sections and calculates the amount of light each section reflects at any given moment. The researchers then tested the model on an existing commercial-scale CSP plant. Noone and Mitsos ran the dimensions of the mirrors from the PS10 plant through the model, determining the plant’s overall efficiency. The group found that the CSP plant experiences a significant amount of shading and blocking each day despite the staggered layout of its mirrors.

Spiraling out

To increase the plant’s theoretical efficiency, Noone and Mitsos tinkered with the pattern of heliostats, using numerical optimization to first bring the fanned-out layout closer together. This narrower layout, the model calculated, reduced the amount of land the mirrors took up by 10 percent without affecting the mirrors’ efficiency in reflecting light. The resulting pattern had some spiral elements similar to layouts in nature.

So the MIT team, working with Torrilhon, looked to nature for inspiration — specifically, to the sunflower. The florets of a sunflower are arranged in a spiraling pattern, known as a Fermat spiral, that appears in many natural objects and has long fascinated mathematicians: The ancient Greeks even applied the patterns to buildings and other architectural structures. Mathematicians have found that each sunflower floret is turned at a “golden angle” — about 137 degrees — with respect to its neighboring floret.

The researchers devised a spiral field with its heliostats rearranged to resemble a sunflower, with each mirror angled about 137 degrees relative to its neighbor. The numerically optimized layout takes up 20 percent less space than the PS10 layout. What’s more, the spiral pattern reduced shading and blocking and increased total efficiency compared with PS10’s radially staggered configuration.

Mitsos says arranging a CSP plant in such a spiral pattern could reduce the amount of land and the number of heliostats required to generate an equivalent amount of energy, which could result in significant cost savings. “Concentrated solar thermal energy needs huge areas,” Mitsos says. “If we’re talking about going to 100 percent or even 10 percent renewables, we will need huge areas, so we better use them efficiently.”

Frank Burkholder, an engineer with the National Renewable Energy Laboratory, says for expensive heliostat fields, Mitsos’ model could potentially generate the same annual energy by taking up “far less” land area.

“The heliostat field presently contributes to about a third of the direct cost of most [CSP] plants,” says Burkholder, who was not involved in the study. “Because heliostats are costly, their spacing relative to each other and the tower … is important. If care isn’t taken in their placement, they can shade and block each other and reduce the amount energy delivered significantly.”

SOURCE: – ScienceDaily

Reclaimed Wastewater for Drinking: Safe but Still a Tough Sell

Reclaimed Wastewater for Drinking: Safe but Still a Tough Sell

Water filtration technology has advanced to the point where wastewater can be rendered safe for drinking, according to a new report, but legislative and psychological hurdles will need to be overcome before widespread adoption can happen.

“Expanding water reuse could significantly increase the nation’s water resource, particularly in coastal communities,” said Rhodes Trussell, president of Trussell Technologies in Pasadena, California, and chair of the committee that wrote the report.

Treated wastewater, also known as reclaimed water, is commonly used for irrigation and industry. And many towns already rely on reused water simply because they draw water downstream from other municipalities’ wastewater release pipes.

“De facto reuse takes place throughout the country,” Trussell said.

But getting the public to knowingly drink treated wastewater has been a tough sell.

New Report Underscores Safety

A new report by the National Research Council (NRC) that reviewed current wastewater treatment technologies found that the possible health risks associated with exposure to chemical contaminants are minimal.

“Available technology can reduce chemical and microbial contaminants to levels comparable to or lower than those present in many current drinking water supplies,” Trussell said.

Trussell and the other NRC report authors say the government could do much to help increase public confidence in wastewater treatment programs for drinking—also known as potable use—and help to provide a consistent minimum level of protection across the nation. Many of these goals could be met by toughening federal regulations, they add.

“For example,” Trussell said, “under the Clean Water Act, the pretreatment regulations, which have made tremendous strides to reduce toxics in the nation’s wastewater since they were first implemented, could be updated to more aggressively pursue organic contaminants that were not identified on the original 1977 list.” In other words, by updating the standards in keeping with current knowledge, consumers can feel more confident that the water is truly safe.

Another challenge is that water reuse regulations can vary widely by location. “In most coastal communities, municipal wastewater belongs to the wastewater utility and retaining it for reuse is fairly easy,” Trussell explained. “In many inland communities that water already [legally] belongs to a downstream user.”

But perhaps the biggest hurdle that will need to be overcome before the public will accept drinking recycled wastewater is not technological or legislative, but psychological.

(See an interactive map of the world’s most important river basins.)

Getting Used to the Idea

“The psychological side is often what’s critical,” said Paul Rozin, a psychologist at the University of Pennsylvania. Rozin appears in the upcoming documentary Last Call at the Oasis, which investigates several aspects of the looming global water crisis.

Most people have a deep revulsion to the idea of drinking reclaimed water, explained Rozin. “The revulsion comes from its closeness to sewage,” he said. “For tap water or bottled water, people tend not to think where it comes from. But for recycled water, they do.” (This despite the fact that many people already drink water drawn downstream from wastewater operations.)

One way to overcome this revulsion is to provide some mental separation between the recycled water and its source. In Last Call at the Oasis, for example, the filmmakers try selling treated water under the catchy product name of “Porcelain Springs” and enlist comedy actor Jack Black to vouch for its drinkability.

Another possibility, Rozin said, is to follow the example set by Singapore. “They’re switching over to recycled water and they’re doing it gradually and also giving people an economic advantage to switch,” he said.

“First, they take recycled water and pump it into the ground so they don’t go directly from recycled water to drinking. And they will also provide the water at any catered event [for free].”

One example of a successful wastewater-recycling program is the Groundwater Replenishment System in Orange County, California, Trussell said. There, wastewater is treated to a level exceeding state and federal drinking standards and is then released into local groundwater recharge basins, where it will eventually be re-drawn for municipal or private use. Previously, treated wastewater was simply discharged into the Pacific Ocean. But the new process should help extend the life of the aquifers, and it may make the idea of reclaimed water more appealing than more direct recycling, since the water receives additional filtering in the ground.

“This project just broke ground for expansion from 70 to 100 million gallons per day,” Trussell said.

(Help reduce global water use by using our tool to calculate your own water footprint.)

The Groundwater Replenishment System and other programs across the United States provide reasons to be optimistic about the future of wastewater treatment programs, Trussell said. “Increasingly, projects are being conducted in the open and have successfully garnered public support,” he added.

In general, Penn’s Rozin said, people often greatly underestimate their ability to adapt to new things, including drinking treated water.

“There’s no doubt that people can get used to it,” he said. “It’s just a matter of getting them there.”

But while wastewater recycling could contribute significantly to the nation’s available freshwater, it will not in itself solve all the water problems that we will face in the coming decades.

“Our estimate is that reuse of all the wastewater we discharge to the oceans and estuaries would increase the water available to U.S. municipalities by about 6 percent,” he added. “Significant, but no panacea.”

In other words, reclaiming our wastewater can be one step toward reducing the amount of freshwater we use, but it cannot solve all our problems. It may help decrease pressure on our overtapped aquifers and rivers, but we still have to improve water management and protection on a global scale.

New generation of nuclear reactors could consume radioactive waste as fuel

New generation of nuclear reactors could consume radioactive waste as fuel

A new generation of “fast” nuclear reactors could consume Britain’s radioactive waste stockpile as fuel, providing enough low-carbon electricity to power the country for more than 500 years, according to figures confirmed by the chief scientific adviser to the Department of Energy and Climate Change (Decc).

Britain’s large stockpile of nuclear waste includes more than 100 tonnes of plutonium and 35,000 tonnes of depleted uranium. The plutonium in particular presents a security risk as a potential target for terrorists and will cost billions to dispose of safely. The government is currently considering options for disposing of or managing it.

Decc’s preferred option is to build a plant to combine the plutonium with other materials in so-called mixed-oxide fuel (Mox), which is less dangerous than the current plutonium-oxide powder. However, there is currently no large-scale capacity for consuming Mox fuel, and the previous Mox plant at Sellafield has been shut after being beset by operating and financial problems. In addition, Mox fuel allows only a tiny proportion of the energy in the waste to be converted into electricity.

The engineering firm GE Hitachi has submitted an alternative proposal based on their Prism fast reactor, which could consume the plutonium as fuel while generating electricity.

“It’s a very elegant idea that we should try and use [the waste] as efficiently as possible. I definitely find it an attractive idea”, said Prof David MacKay, Decc’s chief scientific adviser.

Recent news reports have suggested this proposal has been rejected by the government and Nuclear Decommissioning Authority (NDA) on the grounds of being too far from commercial viability.

However, the Guardian has confirmed that talks between GE Hitachi, Decc and the NDA are continuing. MacKay told the Guardian: “My position as chief scientific adviser at Decc is that I think Prism is an interesting design and I’d like to see [details about its credibility] worked out.” A spokesperson for the NDA said: “The statement that the NDA has rejected the GE Hitachi Prism reactor is completely without foundation.” He added that the current round of discussions “might last about six months”.

Fast reactor technology was developed by the US government over many decades until 1994 when President Clinton terminated all nuclear power research. GE Hitachi’s Prism reactor is a commercial offshoot of that government-funded research. No Prism reactors have yet been sold, but GE believes it could construct one in just a few years plus the time taken to license the technology.

The reactor is a fixed small size, producing around 311MW of power – equivalent to 100 large wind turbines running non-stop or a quarter of a conventional nuclear plant. The reactor core is submerged in a pool of liquid sodium, which acts as a coolant, transferring the heat to the turbines where electricity is generated. Designers say that passive safety features ensure that the reactor won’t go into meltdown if its power source is cut off, which is what happened in last year’s accident at Fukushima, Japan.

In the proposal currently under discussion, a pair of Prism reactors would be installed at Sellafield and optimised to consume the plutonium stockpile as quickly as possible. If, however, the government decided to prioritise low-carbon power generation rather than rapid waste disposal, a larger number of Prism reactors could theoretically be combined with a fuel recycling system to extract as much electricity as possible from the plutonium and depleted uranium.

According to new figures calculated for the Guardian by the American writer and fast reactor advocate Tom Blees, this alternative approach could – given a large enough number of reactors – produce enough low-carbon electricity from Britain’s waste stockpile to supply the UK at current rates of demand for more than 500 years.

MacKay confirmed this figure. “As an upper bound on what you could get from those resources in fast reactors I think it’s a very reasonable estimate. In reality you’d get all kinds of issues so you wouldn’t achieve the upper bound but I still think it’s a reasonable starting point.”

However, he added that free or low-cost fuel wasn’t in itself sufficient to make inexpensive nuclear energy. “When you think about the economics of the low-carbon transition, it isn’t the nuclear fuel that’s the expensive bit – it’s the power stations and the other facilities that go with them.”

The cost of any Prism installation would depend on unknown quantities including the details of the licensing requirements. However, Eric Loewen, chief engineer at GE Hitachi nuclear, claims that the technology should be economically competitive due to its small and fixed-size modular design, which allows it to be produced in an off-site factory.

MacKay said, “I think it’s credible that it could be cheaper [than Mox] but it’s up to GE to tell us the price tag”. He added that the alternative option of making Mox would not be easy either. ” You have to make a big facility to make the Mox fuel and you need to have a load of reactors that can accept the Mox fuel, and we don’t have either of those in place yet.”

MacKay also said that he supported “long-term research and development” into new reactor technologies that could be safer and more efficient than current designs. He argued that such research should not be seen as a threat to renewable technologies such as wind and solar, which were crucial but not sufficient on their own to meet the UK’s ambitious carbon targets.

“If you’ve seriously looked at ways of making plans that add up you come to the conclusion that you need almost everything and you need it very fast – right now. You need all the credible technologies that can develop at scale … I don’t think anyone serious would say that we only need nuclear … but similarly I think it’s unrealistic to say we could get there solely with renewables.”

Another next-generation nuclear technology that convert nuclear waste into plentiful electricity is the molten salt reactor (MSR), also know as the liquid fluoride thorium reactor (LFTR). MacKay said the MSR is “another design that looks very interesting and I think the first prototype will probably get built in the USA in the next few years, if the thorium advocates over there are successful – and I’m going to be very interested to see how it works. On paper, that kind of reactor could burn up plutonium as well, but we’d need detailed designs that are costed before we can seriously consider that option.”

Energy and Industry – Moving Water Moves Industry

Energy and Industry – Moving Water Moves Industry

Energy and water are inextricably linked. Water generates power, and, on the other side of the same coin, it takes large amounts of energy to clean and deliver water.

Nearly 6 percent of electricity in the U.S. comes from hydroelectric sources, which capture the natural energy stored in moving water and convert it into electricity. Hydropower has been in play for thousands of year—an original use was to grind grain at small mills.

But now huge dams associated with hydropower are under fire for altering natural flows and water quality.

In most developing countries, elaborate systems are in place to treat and transport water into our homes, onto agricultural fields, and into factories. All of this pumping and disinfection, especially of salt water, can be very energy intensive, requiring large amounts of nonrenewable resources, such as coal.

Understanding this energy-water nexus can help shine a light on our dependency on both and lead us toward conservation.

Fast Facts

  • A U.S. Congressional mandate to produce 15 billion gallons (56.8 billion liters) of corn ethanol by 2015 would annually require an estimated 1.6 trillion gallons (6 trillion liters) of irrigation water (and even more direct rainfall)—a volume exceeding the state of Iowa’s annual water withdrawals.
  • Transferring Colorado River water into southern California requires about 1.6 kilowatt-hours (kWh) of electricity per cubic meter (35 cubic feet) of water; the same quantity sent hundreds of kilometers from north to south through California’s State Water Project takes about 2.4 kWh, primarily for pumping. Because of these delivery mechanisms, the energy required to provide drinking water to a typical southern California home can rank third behind that required to run the air conditioner and refrigerator.
  • Producing 35 cubic feet (one cubic meter) of drinkable water through desalination reverse osmosis (the process of forcing salty water through a membrane to remove the salts) requires about 2 kWh of electricity. Although that’s down from 5-10 kWh 20 years ago, it is still energy intensive.
Positive & Negative Facts About Wind Energy

Positive & Negative Facts About Wind Energy

Wind is a form of solar energy created by interactions between atmospheric heating, irregularities in the earth’s surface and the earth’s rotation. Wind is a clean energy source that is endlessly renewable and remarkably reliable. It does not pollute the air or cause acid rain like fossil fuels. (See References 1) Advances in wind turbine technology and an abundance of regions with winds suitable for producing power have made wind power the fastest-growing source of energy in the world. (See References 1, 2)

Zero Greenhouse Gases

Some carbon dioxide is released during manufacture and maintenance of wind turbines, but wind turbines themselves emit no carbon dioxide or other greenhouse gases while they are producing electricity. That means users of wind energy have smaller carbon footprints. (See References 2)

Free Fuel

Building and maintaining wind turbines costs money but no one pays for the wind itself. Since wind is a free fuel, wind power prices do not go through the kind of price fluctuations consumers experience with fossil fuels.(See References 2) Wind power prices in the United States averaged 4 to 6 cents a kilowatt-hour in 2010, making it one of the cheapest renewable energy technologies on the market, according to the U.S. Department of Energy. (See References 1)


The towers and turbines that turn wind into electricity come in different sizes to meet different needs. The biggest wind turbines use rotors spanning more than 100 yards mounted on towers higher than 20-story buildings. One of those monsters can generate enough power to support 1,400 homes. A unit designed to make electricity for a single house might have blades with a diameter as small as 8 feet atop a 30-foot tower. (See References 3)


Wind turbines have to be installed on towers higher than nearby trees and buildings to make the most efficient use of the wind. That high profile sometimes leads to complaints that they detract from the aesthetic appearance of a skyline or a neighborhood. (See References 2) Their blades can also churn out noise that irritates neighbors. “We’re 2,400 feet away and it’s really unbearable. It shakes the house and goes through our bones and bodies,” David Wylie, who lives near three wind turbines in Maine, told the “Portland Press Herald.” (See References 4)

Killer Blades

Wind turbines blades batter birds, killing 20,000 to 37,000 a year in the U.S., according to a 2007 National Academy of Sciences study, “Environmental Impacts of Wind-Energy Projects.” In contrast, at least 90 million birds die annually by flying into buildings, more than 130 million die in collisions with power lines, and millions more are killed by pesticides and domestic cats, according to the study. (See References 5)

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Google: Five things to look for in 2012

Google: Five things to look for in 2012

It may be a measure of Google’s dominance that some of the most important events for the company next year will likely take place in courtrooms and government offices.

The Web giant is under investigation both domestically and abroad for allegedly abusing its powerful position as the leader in Internet search. And rivals are suing Google and its partners as the company expands into markets where they’re already competing.

So even as Google works to improve its search engine and bolster emerging businesses such as its Google+ social network, it will be worth keeping tabs on the regulators, lawmakers, and judges who will play a significant role in the company’s business going forward.

Here are five things to look for in 2012:

1. Antitrust decisions in the U.S. and EU

Regulators both in the United States and abroad are closing in on Google. The Federal Trade Commission began a “formal review” of Google’s strategies for building its search business, as well as the tactics it’s used to bake search into its Android mobile operating system. The European Commission is investigating whether Google has unfairly manipulated search results by lowering the rankings of competing services and elevating its own offerings in unpaid results. And the Korean Fair Trade Commission is gathering information about Google allegedly limiting access to rival search engines on its Android mobile operating system

Those inquiries may well come to a head in 2012. It seems likely that U.S. trustbusters will want to resolve the matter before the presidential election, in part because the possibility of a new administration could lead to a different approach with regard to applying antitrust law to search.

European regulators have been looking into Google’s tactics for more than a year now. That investigation is said to be approaching a ruling. The European Commission is also reviewing Google’s pending bid to acquire Motorola Mobility, and regulators there recently suspended that review until Google produces additional documents that the agency said are essential to its evaluation.

The challenge for regulators, if they determine that Google has acted unlawfully, is coming up with an appropriate solution. They could make it more difficult for Google to acquire companies. The bigger fear for Google, if it gets slapped, is a remedy that restricts its conduct regarding search. That may well mean some sort of regulatory structure over the way Google generates search results.

2. Google steps up patent defenses

Google continues to be embroiled in patent litigation. Oracle has sued Google, while Microsoft and Apple have either sued or threatened to sue companies that make devices that run Google’s Android and Chrome operating systems. Google has largely struggled to combat the challenges, leading the company’s chief legal officer, David Drummond, to blog about “a hostile, organized campaign against Android by Microsoft, Oracle, Apple and other companies, waged through bogus patents.”

Whether Android infringes on patents will ultimately be decided by the courts. But the biggest challenge for Google is that it’s put itself in the vulnerable position of having a relatively tiny patent portfolio with which to defend itself. That’s because, in intellectually property litigation, a company with a patent threatens to sue, or actually sues, another company that it believes has infringed on its innovation. The common defense is for the accused company to find one of its own patents that the accusing company has infringed upon and threaten a countersuit. That gives it the ammunition to propose cross-licensing deals that keep both companies out of court.

Google’s thin patent portfolio has made it a bigger target. That’s one key reason, Google Chief Executive Larry Page said, why the Web giant is purchasing Motorola Mobility. Sure, the company is a key Android customer. But it’s also a huge holder of mobile-device patents, something that should help Google protect itself against future litigation. Google will likely continue to acquire patents in the new year to bolster its defenses.

3. Making search more social

Bradley Horowitz, one of the top Google+ executives, recently said, “We’ve shipped the ‘Plus,’ now we’re beginning to ship the ‘Google.'” His point is that simply creating the social network wasn’t the goal. The company is busily weaving other Google properties and technologies–such as YouTube, videoconferencing, and integration with the Android mobile operating system–through it.

But watch for Google to use the knowledge it gleans from those on the social network to make search more relevant. The more Google learns about users, through the comments or companies that they click on the “+1” tab, the smarter Google search results can be for those users. There’s a good chance that users will want to read news articles, for example, that their Google+ connections have liked. The more Google+ learns about users, the more it can translate that information into more relevant search results.

Ultimately, Google is aiming to do more than provide Web surfers with links. It wants to answer their questions. Right now, it can predict what queries users are after before they finish typing the words. It can provide weather forecasts and answers to mathematical equations rather than simply issuing links. Going forward, Google wants to anticipate searchers’ needs without them having to explicitly ask each and every time. Google+ will help give them more tools to do so.

4. Further Android fragmentation

Google’s mobile-phone fortunes have soared on the back of its Android mobile operating system. Since launch in 2007, Android has leapfrogged Research In Motion’s BlackBerry and Apple’s iOS to become the most widely used smartphone operating system. But with several device makers creating Android phones and tablets, and even tweaking the operating system to fit their needs, the user experience often varies from device to device.

Take the slick Motorola Droid Razr, a trim, snappy phone that runs Android 2.3, dubbed Gingerbread. Shortly after it debuted, Google released Android 4.0, known as Ice Cream Sandwich, and Samsung released the Galaxy Nexus, running the latest version. The Droid Razr? It’s still on Gingerbread. Eventually, it will get Ice Cream Sandwich. But it’s unclear when.

Fragmentation isn’t a problem until one version of an Android device can’t run the latest operating system, or a cool new application designed for it. Google acknowledged the challenge at its I/O conference in the spring, saying it would work with manufacturers and wireless carriers to develop guidelines to help get updates to devices more quickly. But it’s not really clear that Google will take the issue seriously because the Android market continues to grow.

5. Chrome market share climbs

A little kerfuffle emerged earlier this month when Web research firm StatCounter noted that Google’s Chrome 15 was more widely used in the last week of November than Microsoft’s Internet Explorer 8. The tumult, of course, is caused by the fact that Internet Explorer has long been the browser leader. And when you add up all the versions of IE in use, it’s far and away the top browser worldwide.

But there’s little doubt that Chrome share is on the rise. And that’s crucial for Google because the browser gives the company the ability to push the Web standards it favors as they emerge. What’s more, Google seems to be moving beyond the notion, floated when Chrome launched in 2008, that its browser was primarily about enabling people to see Web pages faster.

These days, Google is encouraging developers to create Web apps for Chrome that users can get through the Chrome Web store. Already, users can add Angry Birds, a scoreboard from Major League Baseball, and Rdio’s music streaming service. As Chrome grows, expect that business to follow.