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NC company is soaring with the sun

By Reid Creager
    Jean Revillard/Rezo - Rezo
    - Solar Impulse
    - Solar Impulse

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  • Solar flight’s highs and lows

    Le Tang and Hongrae Kim are keenly aware of solar flight’s pros and cons. Part of their roles in ABB’s global research and development center for electric power at N.C. State will be to help us learn more about both extremes.

    “The good thing is that solar is free,” said Le, who heads ABB’s corporate research center. “That’s the reason people really have an interest, because it’s free and renewable. You can use it forever.”

    Though solar power is free, the cost of building and installing solar equipment is not. It’s often expensive, though the cost of solar panels varies by location and the design of the system.

    This is changing. Subsidy programs, tax and rebate incentives by the government to encourage the use of solar panels have helped. The Natural Resources Defense Council says the cost of solar energy has dropped sharply in the past two decades, and experts predict that cost will be less than retail electricity rates in many parts of the U.S. within the next few years.

    Other oft-cited advantages of solar-powered flight: It helps reduce our dependence on fossil fuel, a limited resource that has major cost fluctuations; it doesn’t cause pollution; it doesn’t make noise. One lesser-known disadvantage is that the average cruising speed is about 44 mph, one of the signs that commercial solar flight could be decades away.

    Perhaps the largest issue – and the subject of ongoing research – is the effect of clouds, storms and night time.

    “There’s a big energy generation difference between a sunny day and a cloudy day,” said ABB technological expert and project manager Hongrae. “Another problem is a shade effect. When a cloud is passing by and some panels are shaded, the energy production decreases.”

    Le Tang explained that solar energy is what is called an intermittent source – not consistent, not always available. “That’s the reason we need energy storage,” a backup source of energy such as an electric grid that allows flight even when the sun isn’t shining.

    This energy storage becomes an issue because batteries used to recharge the cells are large and heavy. Many say that finding a more efficient, cost-effective way of storing solar energy is the key to advancing solar flight. Reid Creager

A Raleigh-area company is partnering with a solar plane team that keeps making aviation history. Both are aiming even higher.

ABB, the Swiss global electric engineering firm with North American headquarters in Cary, recently announced that it will work with world-renowned Solar Impulse on energy projects. Solar Impulse’s most visible undertaking is its plan for next year: to circumnavigate the world in a plane powered only by the sun’s energy.

Zurich-based Solar Impulse has made international headlines. Solar flight feats by co-founders and pilots Bertrand Piccard and André Borschberg include the first manned overnight flight (26 hours, in 2010); the first intercontinental flight (2012); and a trip across the United States last year that set several world distance records for solar flight.

But Solar Impulse’s ultimate goal has little to do with records, or even aviation. It’s about demonstrating the dramatically useful impacts of clean energy.

“Our primary purpose is not to revolutionize aviation but the way in which people think about energy and clean technologies,” said Piccard, who captained the first nonstop, around-the-world balloon flight in 1999. “If Solar Impulse technologies were used on a massive scale, the world would be able to save up to 50 percent of the current consumption of fossil energy and produce half of the rest with renewable energies.”

ABB – the second-largest maker of solar power adapters worldwide – has its own solar resume. Its PowerStore is a flywheel technology that protects conventional microgrids and ensures the safe integration of large amounts of wind and solar energy. ABB’s global research and development center for electric power is located on N.C. State’s Centennial Campus.

ABB’s specific role with Solar Impulse is unclear at this point, with details of projects under wraps. Piccard summed up the partnership this way: “Solar Impulse delivers the message, and ABB produces the corresponding products.”

Specs and how SI2 flies

Maxine Ghavi, head of the Solar Industry Segment Initiative at ABB, said the collaboration is a natural: “If you look at ABB and Solar Impulse, we share a common ideal – which is to address the growing energy demand with increased efficiency and minimal environmental impact.”

Increased efficiency was the impetus for Solar Impulse building a second prototype plane. The first – the HB-SIA, which made its initial test flight in December 2009 – was basically a technology lab with wings that was unable to handle flights of longer duration. It was disassembled last August in favor of the larger, upgraded and more powerful Solar Impulse 2 (HB-SIB), which made its maiden flight June 2.

The single-seater has a 236-foot wingspan that’s larger than that of a Boeing 747-8. The 17,000 solar cells built into the wings provide four electric motors with renewable energy.

The plane is made of carbon fiber, known for its strength, low weight, temperature tolerance and chemical resistance. It weighs only 5,070 pounds – about the weight of a midsize car. More than 40 percent of that weight comes from lithium ion batteries that are recharged during the day so that the Solar Impulse 2 can fly through the night.

This technology has advanced dramatically since the 1970s, when solar aviation began with model aircrafts and affordable solar cells appeared on the market. The first manned solar flight was in 1980 in California by Paul MacCready, whose teenage son was a test pilot.

On the horizon

Despite how far Solar Impulse and solar flight have progressed in a short time, “We do not foresee solar-powered commercial aircraft in the near future,” Piccard said. He emphasized that Solar Impulse 2 is an experimental plane, with a calculated lifespan of 2,000 hours.

“As for the aviation industry, it is well aware of its need to change. However, this cannot be done quite as drastically as with Solar Impulse.

“Our project involves zero fuel. Conventional aviation cannot switch straight to zero fuel. Intermediate steps are needed, such as using lighter materials, more direct routes or approaching airports through constant descent rather than performing level landings. Aviation will be the final area of transport able to stop using fuel.”

Nonetheless, Piccard is among the many who eagerly await SI2’s around-the-world attempt next year. He said the operation, planned from March to June, will probably include about 10 flights of two to five days each.

Sunshine will be crucial, especially in the morning. The plan calls for the plane to spend all day climbing as its batteries recharge before descending slowly under power at night to save energy. A headwind at night could cause the plane to lose energy before sunrise.

“At the beginning, the daylight will be too short to fly several days in a row; we will need to land at night with charged batteries and be able to take off again in the morning. If the weather conditions are favorable, we will change pilots and leave again immediately. If there is a storm, we will have to wait for good weather to continue.”

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