Denkenberger's research began with solar cells, devices that turn sunlight into electricity. Solar cells are too costly for people to use currently, Denkenberger said.
"Right now, in most applications, the solar cells are so expensive that it doesn't pay back," he said.
In order to try to utilize less of the expensive solar cells while still producing a high-energy output, Denkenberger began experimenting with reflectors -- equipment that collects sunlight from a large area and reflects it toward solar cells. Thus, sunlight that does not land directly on a solar cell still can be received by a solar cell with the use of reflectors.
"What actually happened was that I figured out, on my own, the best shape of my reflector, and I was going to patent it, but then I figured out it was already patented in the early 1970s," Denkenberger said.
Nonetheless, "I independently found the equation," he said.
Reflectors are placed in a trough-like fashion on both sides of long and narrow strips of solar cells, Denkenberger said. The strips of solar cells themselves are on an inclined panel.
When viewed from the top, the parabola-shaped reflectors run along the same length of the solar cell strip and increase the effective sunlight-collecting area by about three times.
"These reflectors, it's not a simple question on how big to make them, because if you make them taller, then you catch more light in, but then it's more expensive," he said.
Additionally, while a flat bed of solar cells can accept sunlight from any angle, a strip of solar cells surrounded by reflectors can only accept sunlight from angles that do not bump into the outside of the reflectors. "Again, there's a tradeoff, because you're giving up some light, but when the sun is in the right spot, you're getting what we call a concentration factor," he said.
Denkenberger proceeded to write a computer program that would give the optimal angle of the panel and the optimal equation for the reflectors to produce a maximal amount of energy for a minimal price.
"There are a million and one variables involved," said Akhlesh Lakhtakia, professor of engineering science and mechanics and Denkenberger's research advisor, adding that, although other people had optimized reflectors with one variable before, Denkenberger's work was unique for its multivariable optimization.
"You want to expose solar cells to the most amount of energy," Lakhtakia said. "In reality, the thing is that the conditions that make the solar cells exposed change every minute, and they depend a lot on location."
Everything from climate, latitude, environment, reflectiveness of the reflector, cost of the reflectors and solar cells, time of year and other variables were factored into Denkenberger's optimization program.
"He's has taken the art of designing solar cell concentration to a new level," Lakhtakia said.
Thus, when the program finishes its calculations, it shows how to make solar energy cheaper.
"The power of my program is that it's not just for one size of solar cell or for one latitude," Denkenberger said. "I can actually enter in things that vary those parameters. If you're on the equator or if you're in State College, I can factor that in."
The program's optimization of the reflectors is the crux of Denkenberger's research. "The original part is optimizing, actually figuring out how to use these things," he said. "That's what this program does. ... It gives you real numbers."
Denkenberger's work did not stop with solar cells, however. He recently became involved with solar cookers and solar pasteurizers.
"Much of the world cooks with wood, and also this is the less-developed countries," he said, adding that people will deforest their living areas in order to find wood with which to cook.
"Most of the less-developed countries are near the equator, so they get more sun," he added.
Reflectors can be used to concentrate sunlight for use in cooking and heating water in order to kill dangerous microbes. Denkenberger said these cookers and pasteurizers, which work by sunlight instead of wood, could be an asset to the less-developed countries that have plenty of sunlight. "It makes a lot of sense to use solar," he said.
With a solar cooker, food is placed into an enclosed box with a clear cover. Parabolic reflectors are placed on all four sides on the top of the box. They collect and concentrate sunlight to heat and cook the food.
The use of reflectors is especially economical and useful in solar cookers, Denkenberger said.
A solar pasteurizer is similar to a solar cooker, in that reflectors are placed around the top of a box to heat up water inside the box. "We know we have to warm the water up to 150 degrees Fahrenheit," Denkenberger said. "Almost everything that causes disease in humans is killed at 150 F, not 212."
To make a solar pasteurizer, a tube curled into a rectangular spiral is placed inside the solar cooker. At one end of the tube comes the dirty water. The other end of the tube has a temperature-sensitive valve.
When the dirty water flows into the spiraled tube inside the box, it is stopped at the valve. The reflectors concentrate light into the box, which heats up the water. When the water has reached a high enough temperature, the valve opens up, allowing the clean, hot water to flow out and letting more, cold, dirty water to flow in until it reaches the valve, which then closes again.
The outgoing hot water and incoming cold water also go through what is called a heat exchange. "The heat exchange says that we have a bunch of clean water that's hot. We should be able to use some of that heat to warm the dirty water that's going to come in," Denkenberger said.
Thus, the hot water gives some heat to the cold water in the heat exchange, increasing the efficiency of the solar pasteurizer.
The autonomy of the solar pasteurizer makes it easier to use than simply putting a pot of water in a simple solar cooker and hoping that all the water will be heated enough to kill the microbes, Denkenberger said.
Denkenberger's research with the solar cookers and pasteurizers again utilizes a computer program. However, the curvature and height of the reflectors are no longer an output, but an input. "In this application, it's more of a calculator than it is an optimizer," he said.
Denkenberger also assumes that the solar cooker and pasteurizer will be frequently moved manually to point the reflectors more toward the sun, making the output of his computer program slightly different.
"What comes out is how much food you can cook or how much water you can pasteurize," Denkenberger said. "Also, the other thing it can do is tell you how much the reflector would cost."
Denkenberger hopes that his work with solar cookers and pasteurizers will eventually help less-developed countries stop major deforestation and provide them with clean water.
"Approximately half of the people in less-developed countries don't have safe drinking water," he said.
Lakhtakia was cautiously optimistic about Denkenberger's work. "The very best ideas can languish," Lakhtakia said. "Let's put it this way -- I think if his idea does catch on, then I think in the tropical areas, certainly it could have a major impact."
Lakhtakia did fully recognize the potential in Denkenberger's research, which so far has been mostly theoretical and done on a computer. "Ideas of this kind are certainly very significant," he said.
Denkenberger will have a poster of his work March 21-22 at the Undergraduate Exhibition in the HUB-Robeson Center's Alumni Hall. He is also traveling March 15-17 to Lexington, KY, where he will present his work at the National Conference on Undergraduate Research.
Most of all, Denkenberger is proud of the immediate applicability of his work.
"I really feel that this work can be used to help people in the real world," he said. "It means a lot to me because I think I can help people with it."
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