Solar power sees cheaper prices


Solar power has the potential to be a cheap and efficient source of energy — thanks in part to the work of Jason Stauth.

Dr. Jason Stauth, assistant professor at Dartmouth College, spoke about the potential to improve and expand the use of solar power at the Electrical and Computer Engineering Colloquium last Wednesday on Busch campus.

He said the cost of solar energy per watt has come down faster than anyone predicted. It has lowered to about 15 cents per watt.

“It was predicted that the cost of solar energy would be fifteen cents per watt by 2020. We achieved this in 2011,” he said.

Market competition has played a role in garnering attention. The United States has been improving, but China is still the main source for solar energy, Stauth said.

“In the last five years, China jumped from zero percent to 60 percent of global contribution to solar generation,” Stauth said.

He said there has also been an increase of local interest in solar energy. Walmart has installed solar panels on its rooftops and generates 65 megawatts of electricity — enough to power a moderately sized-town of 20,000 homes.

The two methods to capture solar power are through solar panels and solar thermal collectors, Stauth said. Thermal energy is more efficient, but much more costly, spacious and difficult to improve.

But even improving solar panel technology is no small feat, he said. The main concern is power efficiency, or grid cost parity, since the parts of the cells that compose solar panels, called photodiodes, lose power when not all of them are activated.

“The problem is with a particular photodiode, only a particular range of wavelengths of light can activate it,” said Robert Gatdula, a first-year graduate student in the Department of Electrical and Computer Engineering.

He said a way to improve efficiency is by making multiple layers of photodiodes that respond to multiple wavelengths of sunlight.

But adding layers to a solar cell increases the volume of the solar panel, which creates problems in practical implementation, Gatdula said. The goal of improvement is to downsize volume.

There are more components to take into account. A solar panel is only responsible for generating electricity, not optimizing, Stauth said.

The solar panel needs a converter to boost the energy received from the photodiodes, he said.

“The only place where you don’t use a converter is when you take a solar panel and connect it directly to a lead acid battery,” Stauth said.

Another part, the inverter, takes the energy and puts it in a form that is usable by electronics, he said.

The next step in research is minimizing the size of the inverter and refining it to efficiently transfer solar energy into usable energy, Stauth said. Micro-inverters are taking over for residential applications, when it makes sense to have a smaller system.

“The inverters [Stauth] was showing on the solar cells were tiny. The typical ones are probably a few cubic feet large when his are a few cubic inches in volume,” Gatdula said.

Stauth said he expects all the modules of the solar panel system to be combined, minimizing power loss.

“The examples I showed had three converters per panel,” he said. “We want to go to something like 30 converters per panel.”

Stauth revealed new technologies that are still in the development phase including the deep-trench and intermagnetic systems. Deep-trench caps are hole-punched silicon chips that have a higher charge capacity.

“The larger the capacitance density of a material is, the more charge it can hold in a smaller volume, a crucial property in electronics miniaturization,” said Michael Boan, a School of Engineering junior.

Stauth said his research at Dartmouth expands on these intermagnetic systems, which involve chips with integrated components that maximize power efficiency while minimizing volume.

Maintenance and shading are other factors that hinder efficiency, he said. Solar panels do not lose too much efficiency from the lack of maintenance, which is why it is often overlooked.

“Externalities are often neglected. People don’t talk about this,” Stauth said.

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