Solar Updraft Towers to Generate Food and Energy

by Mike Chino

A new breed of solar tower may soon be sprouting up in Namibia, providing the nation with a carbon-free source of electricity and food during the day and night. At one and a half kilometers tall and 280 meters wide, these massive solar updraft towers could potentially produce 400MW of energy each - enough to power Windhoek, the nation’s capital. Proposed by intellectual property company Hahn & Hahn, the towers generate energy by forcing heated air through a shaft lined with wind turbines. Additionally, the base of each tower will function as a 37 square km greenhouse where crops can be grown.

Solar updraft towers are an oft-overlooked source of alternative energy, although they do require a great expanse of space and copious amounts of sunlight. Theo von Backström from the Department of Mechanical Engineering at South Africa’s Stellenbosch University states: “One of the main reasons why commercial solar chimney power plants have not been built that they have to be very large to be economically viable”. Fortunately Namibia’s arid desert region provides plenty of space for such a generator, and the country sees around 300 days of sunshine per year.

Solar updraft towers generate energy by using sunlight to heat the air within a vast transparent greenhouse situated at the base of the chimney. As the hot air rises, it is funneled into the reinforced concrete chimney, driving a series of wind turbines which in turn generate energy.

The structure’s greenhouse base provides the perfect environment for growing crops, which actually allow the plant to produce energy after the sun has set. The water used for crops is heated during the day and transfers this energy to the tower at night. Once the towers are constructed they require very little maintenance, and Namibia has agreed to finance half of the costs of the $780,000 pre-feasibility report.

Original here

Blue skies, scorched Earth? What is Global Dimming?

With fierce storm after storm hitting the Caribbean and threatening our coasts this hurricane season seems to illuminate the ever more apparent effects of climate change. While we do not have more storms than usual the intensity appears to be on the rise, i.e. more storms are reaching higher categories thus our extremes are getting more extreme [Science]. This alone calls for our attention and efforts to make changes to decrease the greenhouse effect that is warming the Earth and causing greater highs and lows but there is more to this than meets the eye.

It is clearly necessary to work to decrease emissions that are contributing to climate change but what we may unknowingly be doing is exacerbating the problem by not fully understanding the complexity of the system. Now I am not saying we should allow massive amounts of pollution, I am merely suggesting it is more complicated than the simplified version we get watching TV or the glossy greenwashed sound bytes we are so often exposed to. Even this write up is overly simplified but such is life. The main complication I speak of is the phenomena that is termed “global dimming.” Just like it sounds, global dimming describes the decrease in sunlight that is actually reaching Earth’s surface.

Over the past 4 decades scientists have watched the global incoming solar radiation decrease by 12% [American Geophysical Union]. TWELVE PERCENT. That is huge! Breaking it down for each continent the drops in sunlight recorded between the 1950s and 1990s are staggering. The level dropped 9% in Antarctica, 10% over the U.S., nearly 30% over Russia, and up to 60% in parts of England. With that you would expect that we should be cooling down, right? It is logical to think if less sunlight reaches Earth the temperature would drop, just think of a cloudy day or even just standing in the shade. It makes a significant difference but we are not cooling down, we continue to get warmer.

With this in mind it may be that global dimming is masking or delaying the potentially far more extreme effects of global warming. Particle pollution, like ash, soot, and sulfur dioxide, in the atmosphere is believed to be the culprit for global dimming. Just like sunlight bounces off the top of clouds, so too will it bounce off of polluting particles. The compounding factor though, is that the polluting particles apparently make the clouds themselves far more reflective. This is because there are many more pollution particles in polluted clouds (as opposed to natural particles such as pollen or salt crystals in unpolluted clouds) so water droplets cannot condense to be large enough to fall as rain, rather they remain suspended in the atmosphere and continue to reflect sunlight back out of the atmosphere and drought ensues.

If we were to eliminate global dimming all together without addressing global warming the increase in temperature and extreme weather might be more significant than previously predicted. This has been recorded with one full degree temperature change in just a few days of decreased pollution in the days following the 9/11 attacks [Nature]. This reverse effect of dimming has been has been blamed along with global warming for increasing temperatures, appropriately called global brightening [Geophysical Research Letters]. No one wants smoggy skies but it could be smog and particulates that may be shielding us from the full consequences of the greenhouse gases we pump into our air daily. Clear blue skies are something many folks thinks of when they think of “going green” but those clear blue skies may hold more heat than we can handle.

Original here

Where Sweat Equals Electricity

By KI MAE HEUSSNER

It sounds like something you'd only see on the Discovery Channel: people pedaling ferociously to create enough energy to power the television, stereo and lights.

Stationary bicycles connected to small generators can charge batteries that power televisions and stereos.

But for Adam Boesel, owner of the Green Microgym in Portland, Ore., and his partners, this could be the future.

Launched last week, his "human-powered" gym is one of few fitness centers in the world that runs on power generated by people working out, Boesel said.

As members pedal on stationary bicycles, a small motor connected to the stations charges batteries that power the gym's television and stereo system.

Boesel said he doesn't yet have a way to quantify the output but knows that at the moment it's relatively small. However, this is just the beginning, he said.

"Our goal is to someday create 100 percent of the electricity we use in the gym," Boesel said. "The short-term goal is to get all of the electricity we can out of the machines."

In addition to three spin bikes Boesel re-engineered the gym features a new four-person machine that generates 200 to 400 watts of electricity an hour, depending on the fitness level of the group.

Created by El Paso, Texas-based Henry Works, the Team Dynamo connects hand cranks and foot pedals to a generator to capture as much human energy as possible.

"It's a little humbling -- a person can make about a penny's worth of electricity an hour. So it's not a lot," said Michael Tagget, president of Henry Works, adding that on his or her own, an individual can create 50 to 100 watts of electricity.

"But if 20, 30, 40 people are doing that in a gym, they can [create] all the electricity for entertainment systems. It's better than nothing and the feeling of accomplishing something is worthwhile," Tagget noted.

Although Tagget's company is starting with the commercial market -- the Green Microgym is the first gym to test the product -- it plans to offer a home unit in the spring.

Boesel's gym is also working with a St. Petersburg, Fla.-based startup called ReRev.com to implement a "grid-tie" system. Instead of using a battery-based system, ReRev.com's approach is to retrofit elliptical machines to harvest energy from the machines and send the electricity directly back into the electrical panel.

Power Gym of the Future

"These machines -- the way they're set up -- are normally emitting heat. If they run all day, they're putting out ambient heat into the facility. We've developed a system that doesn't emit heat in the facility but instead turns it into electricity," said Hudson Harr, president and founder of ReRev.com.

Harr said his system is an improvement over battery-based approaches that require more maintenance and are less energy efficient. As energy passes through the battery, he said, some of it is lost.

ReRev.com retrofitted 15 machines at a Gainesville, Fla., fitness center in April and, Harr said, on average, that installation is producing between 2 and 7 kilowatts per day.

Although the Portland gym is one of the first facilities in the country to harness human energy, the technology has already been introduced in other parts of the world.

The California Fitness gym in Hong Kong uses a battery-based system to help supply power. The Sustainable Dance Club in Rotterdam, Netherlands, also relies on human-powered technology.

The company's literature says the dance floor is a movable surface composed of small modules. As people dance, the movement of the modules is converted into electricity that lights up the floor. An "energy meter" allows dancers to see the amount of energy they are creating.

Like the TVs and stereos in the gyms, this meter encourages participants to work harder to generate more energy.

Actor and environmentalist Ed Begley Jr. has been a long-standing fan of the human power. In 1990, he and a friend connected a bicycle to a 24-volt battery. On his cable reality show, "Living With Ed," airing on Planet Green TV, he has been known to make toast with energy created by pedaling his bicycle.

"I think as much human-powered exercise equipment as we can advance would be for the good," he told ABCNews.com. "I think that the idea of sitting on a life cycle and using power that is plugged into the wall ... is upside down."

The Emmy Award-winning host of the eponymous educational television program "Bill Nye the Science Guy" also gives the technology a thumbs up but cautions that it's not free of problems.

While the amount of energy a human can generate is not insignificant, it still requires a lot of work. For example, Henry Works' Tagget said he estimates that the average user of his power-generating cycling machine can create 100 watts per hour, which could power a smaller television for about an hour and fifteen minutes.

Nye also said that questions regarding energy storage persist.

Still, he said, "The idea is great. You see people going to the gym now in droves and they ride their bikes to nowhere, and so wouldn't it be nice to capture all that energy?"

Original here