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Duke researcher pioneers solar panel substitute

Implementing solar panels may make most environmentally conscious individuals feel virtuous, but Duke engineer Nico Hotz has higher standards.

Hotz, who accepted a position as an assistant professor of mechanical engineering in the Pratt School of Engineering last summer, is working on a system that combines sunlight and biofuel—what he calls a hybrid system—to create electricity. This new technology could make solar panels, which convert sunlight directly into electricity, obsolete.

In Hotz’s system, the energy from sunlight starts a chemical reaction that converts fuel to hydrogen. This hydrogen is then stored in a fuel cell, which converts it to electricity. Although Hotz currently uses purchased methanol for fuel, he said the system would ideally utilize biomass, like wood waste or other agricultural waste, which can be converted into methanol. Hotz added that the process is “very clean.”

A more efficient alternative

Hotz created his design to eliminate what he recognized as a design flaw in other renewable energy systems.

“If you have a [solar panel] on the roof of your house, you only get power from it during the day, maybe from 9 a.m. to 5 p.m. or something like that. At night, obviously you don’t get any power and in the evening and early morning you get hardly any power,” he said. “You need to have something to store the energy… for example, a battery that you charge during the day and then recharge and take the energy from the battery at night.”

But, Hotz said, batteries are often large and expensive. Storing energy in the form of a gas such as hydrogen requires much less space and is more efficient and cheaper.

Although Hotz said the process of converting fuel to hydrogen is well known—other researchers have also experimented with this process—his utilization of sunlight is new. To convert methanol to hydrogen without using sunlight, one must burn some of the fuel to heat the reactor.

“If you do it [by burning fuel] you lose maybe a third of your fuel to heat the whole thing,” he said. “We ignored that way—we use the whole fuel to convert hydrogen and heat it by using sunlight instead of burning the fuel.” Hotz estimates that this alternative allows him to increase efficiency by up to 50 percent.

Cheaper energy?

In addition to being clean, Hotz also believes his system will also be a cost-effective alternative to solar panels, also known as photovoltaic cells.

“The problem with photovoltaic cells, like silicon cells, is that the efficiency of it is around 10 to 15 percent, so per square meter or per square foot of area that you have such cells on your roof, it can only convert 10, maybe 15 percent of the sunlight into electricity,” he said. “In our case, because we’re using a different fuel, we get a power output, let’s say six, seven, eight times higher than photovoltaic cells per area.”

Consequently, Hotz says he needs less area of panels to generate the same amount of energy that would be generated by photovoltaic panels. Although Hotz said that at the price of his system cannot compare to the cost of using a traditional electricity provider at the moment, he said he hopes reduced prices as a result of mass production will eventually make his system a cost-effective alternative for consumers in that market, too.

Training a future generation of researchers

Hotz’s staff is usually comprised of only about five people and includes high school students, undergraduates and graduate students.

Junior Emmanuel Lim, who said he has been interested in renewable energy research since he worked in the environment department for the Philippine government in high school, will be pursuing independent research in Hotz’s lab this Fall.

“It’s really exciting because we’re always talking in lab about how we’re one of the first people to do this,” Lim said. “There aren’t very many papers or studies in the past so it’s really right at the forefront of research in the field.”

Hotz’s lab also has attracted the attentions of people not already tied to the University.

“I heard from my university in Munich about this project and they also were pretty interested,” said graduate student Alexander Boecker, a visiting student from Technical University Munich, who works on operating the fuel cell.

Researchers hope they are only at the beginning of a process that could drastically change the face of energy production.


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