It’s always about the money. Yes, everyone wants to go solar. Yes, they realize the environmental benefits, and of course the enormous financial savings. But the average American home’s electricity needs require a 9 kilowatt solar array, at the cost of over $60,000. And so the average solar installation covers only one third of the building’s total needs.
However, with a little bit of chemistry and molecular engineering, and a dose of intellectual ingenuity, solar costs stand on the verge of tumbling. A second generation of light-to-energy converting products is currently under manufacture by Konarka Technologies Inc. Co-founded by Nobel laureate chemist Alan Heeger, Konarka is fitting tents, canopies, sailboats, awnings, even ladies hand bags and clothing with a thin layer of photo-active material for solar conversion.
Heeger and his team at University of California, Santa Barbara, have completed the initial science and have guided manufacturing toward a goal that matches the title of his upcoming Princeton speech: “Turning the Dream of Low Cost Plastic Solar Cells into a Reality.” Heeger will explain how close we are to a new era of solar energy at the Princeton Regional Chamber of Commerce’s Albert Einstein Memorial Lecture, a free, open-to-the-public lecture that takes place Thursday, April 23, at 5:30 p.m. at the Woodrow Wilson School of Public and International Affairs on Washington Road. Visit www.princetonchamber.org.
Heeger’s quest for solar-applicable semiconducting and metallic polymers has, as he puts it “taken me on a great ride,” which began from the unlikely avenue of physics. Growing up in Omaha, Heeger earned his bachelor’s in physics and mathematics at the University of Nebraska in 1957, followed by his Ph.D. in physics from the University of California, Berkeley, in l961. He spent the next 20 years as a professor at the University of Pennsylvania before moving to Santa Barbara in l982.
Not content with pure research, Heeger’s discoveries led him to found four companies, beginning with Uniax in 1990. Uniax sold the conducting polymers he developed. Ten years later Dupont acquired Uniax for a hefty sum and Heeger also won the Nobel prize in chemistry for his discovery of conductive polymers. “I guess you can say 2000 was sort of a good year for me,” says Heeger modestly. Heeger continues to work on more efficient polymers for solar conversion, both at UCSB and through Konarka.
“It’s all about dollars per watt,” says Heeger. The next generation of solar energy must overcome the prohibitively high cost, while surpassing the current silicon solar cell efficiency.
Silicon solar. Solar conversion, as commonly used today, employs a monocrystaline silicon cell, deceptively called a wafer. Grouped into large arrays, these wafers are protected under heavy glass, facing the sun. Photons in sunlight strike the array and are absorbed by the conducting silicon. They excite negatively charged atoms that slide down the copper wires as electricity. An inverter typically changes the direct charge to alternating current.
First invented in 1954, this solar technology, along with industrial mass production, has made giant strides in lowering the cost. “The problem is, they are now at the low end of the cost-shaving curve for this technology,” notes Heeger. The protecting glass is itself expensive, and they make the solar panels cumbersome.
Copper prices are ever soaring. However, silicon solar does hold, theoretically at least, the potential for converting 30 percent of the sun’s rays into effective energy. That holy grail of efficiency (which most fall far below) places it on financial par with fossil fuels.
Solar film generation. Imagine, if instead of silicon wafers, copper wires, and glass, you found a plastic-like strand that could be chemically dipped and spread like a film on a flexible substrate, such as a canvas awning. You would have solar energy’s better mousetrap, and well-funded CEOs would be elbowing their way to your door. Such have been the hopes and labors of Heeger and his partners around the globe.
Yet simple as the process sounds, creating the materials is incredibly complex. The polymers sought are basically long strands of macromolecules with repeating structural units. Three basic classes of polymers have been observed to conduct electricity — that is, become semiconductors. “You don’t just find these things in the ground,” states Heeger. “They must be designed and molecularly engineered.”
And the right polymer is only the half of it.
Heeger’s team is also looking for second material to form the necessary junction. To achieve an electric charge, the photons must excite the polymer and jump the gap between it and a second material that spontaneously separates the precise amount to let the charged electrons excite into electricity. The search demands an exhausting whirl of nano-experimentation.
“This first step of exciting the polymer is the same as the first step of photosynthesis,” says Heeger, but it occurs 100 times faster in the solar conversion process. “It took nature millions of years to get photosynthesis right, so I guess you have to be patient with us.”
Solar II’s timetable. Patience is the last virtue being expressed by a solar-seeking public. To date Heeger and his group have done and proved the initial science for cheaper, more flexibly used solar energy. Konarka has found a way to produce small items. “The real fly in the low-cost ointment is efficiency,” says Heeger. “We need more science to amplify the efficiency for major structural solar — that’s why we have been sticking to the smaller items.” But even with these attractive mobile products, toxicity and durability issues remain.
However, Heeger foresees — if hopefully — 10 percent efficiency achieved by 2010 and 20 percent soon thereafter. The uses and savings of this next generation abound. Millions of square feet of the glass that form our nation’s cityscapes already bear a thin, glare protecting film. Imagine the power if they were spread with a solar film that made each pane an energy producer.