Green Wombat describes a balloon solar collector:

It sounds like something out of one of those do-it-your-self magazines: Stitch together two buck’s worth of thin-film plastic – the stuff potato chip bags are made of – stick in a photovoltaic cell, inflate with air and, voilà, you’ve got yourself a “solar balloon” that will generate a kilowatt of electricity. String together 10,000 balloons and you’ve got a solar power plant that can power a town. California startup Cool Earth Solar believes this high-low tech approach is what will make its solar power plants competitive with fossil fuels.

Instead of using expensive optics to concentrate sunlight on the solar cell, Cool Earth manipulates the air pressure inside the balloon to change the shape of the mirrored surface so that it focuses the maximum amount of sunlight on the solar cell, boosting electricity generation 300 to 400 times. By replacing expensive materials like steel with cheap-as-chips plastic and air, Cool Earth aims to dramatically lower the price of solar electricity.

A prototype power plant is being built in a field across the street from Cool Earth’s offices and Lamkin says a 1.5 megawatt plant will be constructed early next year in the Central Valley town of Tracy.

Lamkin estimates that a Cool Earth power plant can be up and running in six months, which should appeal to [California] utilities [...], which are under the gun to meet state mandates to obtain 20% of their electricity from renewable sources by 2010.

“Our major structural element is air, which so far is free,” Lamkin says. “And the sun isn’t taxed either.”  Yet.

Careful, don’t temp Obama.

A micro nuclear reactor in your garden?

According to The Guardian, a U.S. company based in New Mexico, Hyperion Power Generation, has designed mini nuclear plants to power 20,000 homes. The company has already received firm orders and expects to deliver about 4,000 ‘individual’ plants between 2013 and 2023.

In the U.S., where people spent more energy than in other parts of the world, such a reactor should be able to deliver power to only 10,000 households, for a cost of $2,500 per home. But in developing nations, one HPM could provide enough power for 60,000 homes or more, for a cost of less than $400. This is quite reasonable if you agree with Hyperion, which states that the energy from its HPMs will cost about 10 cents/watt.

Now there are some new twists and turns—essentially, three very positive developments that would not have been generally anticipated a decade ago. First, silicon-based solar technology has decoupled from the semiconductor industry and is achieving steady cost reductions, so that those following PV discern a kind of Moore’s law at work. In 2005, production of silicon for solar cells already surpassed production of silicon for semiconductors.

Second, the industry has become so confident in that evolutionary path, policymakers and planners have started to set dates when they expect PV-generated electricity to be competitive with the major sources of electricity sold on the grid now. And third, while the incremental path promises a commercial breakthrough within ten years, it’s suddenly looking like second generation technology may be arriving after all—in which case wide commercialization of PV could occur much sooner.

 
[Above, maps showing average daily solar energy]

In recent years, global PV production has been increasing at a rate of 50 percent per year, so that accumulated global capacity doubles about every 18 months. The PV Moore’s law states that with every doubling of capacity, PV costs come down by 20 percent. In 2004, installing PV cost about $7 per watt, compared to $1/W for wind, which at that time was beginning to stand on its own feet commercially, Last, year, as recently noted in this blog, average global solar costs had come down to between $4 and $5 per watt, right in line with the PV Moore’s law. Extrapolate those gains out six or seven years, and PV costs will be below $2/W, making photovolatics competitive with 2004 wind.

Johnson says it has the potential to be the best-ever method of converting solar energy into a form that we can use. Among the potential applications are at utility-scale solar thermal farms and for plug-in hybrid vehicles, in which the device would use waste heat from the car’s internal combustion engine to help power the car’s electric motor.

Johnson says a prototype of the heat engine, called the Johnson Thermoelectromechanical Energy Conversion System, or JTEC, will be ready in a few months. It could, ideally, be 78 percent Carnot efficient. But what sets JTEC apart is its all-solid-state design. The lack of moving parts such as turbines and pistons eliminates nearly all of the parasitic losses that, in machines like an automobile engine, greatly lower efficiency.

In contrast, photovoltaic devices have net conversion efficiencies in the teens and thermionic (or thermoelectric) chips reach only a little higher than 20 percent of Carnot when converting heat to electricity.

“Johnson has opened up a fundamentally new pathway to generate electricity from heat,” says Paul Werbos, program director for power, control, and adaptive networks at the U.S. National Science Foundation (NSF). Werbos, an IEEE Fellow, says the NSF is funding Johnson’s heat-engine research because of the strong chance that it could cut the cost of solar power in half. Werbos acknowledges that the product’s development is still at an early stage where unforeseen problems might creep in. “But I don’t see any showstoppers,” he says.

Find out all the gory details in this IEEE Spectrum article.

Animation of the process.

Johnson’s page for JTEC, Johnson Thermoelectric Energy Conversion System.

In his hometown of Marietta, Georgia, February 25, 1994 was declared “Lonnie G. Johnson Day” in his honor

To recap, solar thermal plants, which are very different from solar photovoltaics, use long rows of parabolic mirrors to focus the sun’s rays on tubes of synthetic oil suspended above the arrays. The hot oil is used to create steam which drives electricity-generating turbines. This new power plant will be built on 2,012 acres of former farmland beside a Honda test track near California City.

According to the Green Wombat article, California law requires the state’s investor-owned utilities — PG&E (PCG), Southern California Edison (EIX) and San Diego Gas & Electric (SRE) — to obtain 20 percent of their electricity from renewable sources by 2010 and 33 percent by 2020. But public utilities like LADWP only have to set green energy targets, 13 percent by 2010 and 20 percent by 2017 in Los Angeles’ case. Under California’s global warming law, the state’s greenhouse gas emissions must be reduced to 1990 levels by 2020.

Not surprisingly, those renewable energy mandates have been driving the market for large-scale solar power plants, but so far California’s Big Three utilities have placed their bets on startups like Ausra, BrightSource Energy and Stirling Energy Systems.

See my recent post on solar thermal plants.

According to the story there are plans to build several new solar thermal plant in the deserts of the southwestern US.

Today, natural gas prices are much higher [than the 90s when natural gas plants were being built across the nation], and political opposition is rising to construction of new coal-burning power plants. Many states, including California, are imposing mandates for renewable energy. All of that is reviving interest in solar thermal plants.

The power they produce is still relatively expensive. Industry experts say the plant here produces power at a cost per kilowatt- hour of 15 to 20 cents. With a little more experience and some economies of scale, that could fall to about 10 cents, according to a recent report by Emerging Energy Research, a consulting firm in Cambridge, Mass. Newly built coal-fired plants are expected to produce power at about 7 cents per kilowatt-hour or more if carbon is taxed.

How it works:

Nevada Solar One, built by a Spanish company, Acciona, is of a proven design. It uses a mirror in the shape of a parabola to focus light onto a black pipe with a heat-transfer fluid inside. The fluid is used to boil water into steam, which turns a generator that can produce 64 megawatts.

That is small compared with a plant running on coal or natural gas, but far bigger than a typical installation involving solar photovoltaic panels, the type of solar power most people are familiar with. That technology, while good for some uses, is far more expensive than solar thermal power.

…

The newest solar-thermal technology involves building a “power tower,” a tall structure flanked by thousands of mirrors, each of which pivots to focus light on the tower, heating fluid. That design can work even in places with weaker sunlight than a desert.

One of the big advantages of these plants is that they can be built with the capacity to store heat in what amounts to a giant Thermos. Experts say that will smooth production and make it easier to integrate the plants into the electrical grid.

Obligatory environmental considerations:

They could take up immense amounts of land and damage the environment.

Already, building a plant in California requires hiring a licensed tortoise wrangler to capture and relocate endangered desert tortoises.

I’m amazed that the state of California has an office that licenses “tortoise wranglers.” Thank God someone’s watching out for the tortoises!

Also see this 5 min NYT video summarizing the technology.