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Collaboration with start-up company aims to improve efficiency of = solar=20 power

by Teresa Riordan =C2=B7 Posted September 21, 2006; 03:59 = p.m.

Solar panels that are slated to be installed this fall on the roof of = Princeton's Engineering Quadrangle will shave only about $60 off the=20 University's monthly electricity bill. But the technology that emerges = from this=20 unique industry-academia research collaboration may eventually save New = Jersey=20 households millions of dollars in energy costs.

Princeton Power = Systems,=20 a company started in 2001 by three freshly minted Princeton engineering=20 graduates, has received a grant of $529,626 from the New Jersey = Commission on=20 Science and Technology for a collaboration with the School of Engineering and = Applied=20 Science.

"Most people think of solar panels as being = passive," said=20 Darren Hammell, who is chief executive officer of Princeton Power, which = he=20 cofounded with Erik Limpaecher and Mark Holveck, all members of the = class of=20 2001. "But we can actively control them to optimize their efficiency in = response=20 to changing environmental conditions."

The company produces a = device=20 called a "grid-tied inverter," which allows raw electricity produced by = a group=20 of solar panels to flow easily into the main power grid. It translates = the=20 direct current (DC) produced by the solar panels into alternating = current (AC)=20 -- the form of electricity that is the lingua franca of public utility = grids --=20 more efficiently than anything currently available.

Princeton = Power=20 already produces commercial-scale inverters. One purpose of the research = project=20 with the School of Engineering is to scale the inverter to a smaller = size so=20 that it can work optimally for a three-bedroom house in, say, New=20 Brunswick.

Hammell noted that most studies of solar power have = been done=20 in sun-saturated states like California and Arizona. "New Jersey is in = many ways=20 ideal for solar power because of a good state rebate program and high = energy=20 prices," he said. "But no one has really studied how solar power can be=20 optimized in New Jersey."

For one thing, of course, New Jersey = has a lot=20 of clouds. This means that in order to maximize the power harvested from = the=20 panels, the inverter needs to tweak both the voltage (the capacity to = produce=20 electricity) and the current (the flow of the electricity) so that both = run=20 optimally in an on-the-fly response to changing sun = intensity.

Professor=20 of Electrical Engineering Sanjeev = Kulkarni is=20 one of the faculty members helping Princeton Power develop robust = algorithms=20 that will convert DC power to AC power as efficiently as possible.=20

Kulkarni is no stranger to industry collaborations. He has = consulted=20 with Siemens, NEC, IBM, Intel and other big corporations on thorny = problems in=20 image/video processing, statistical pattern recognition and machine = learning.=20 But this is the first time he has worked with a young company like = Princeton=20 Power.

"I'm mostly a theoretician, but having a concrete = application in=20 mind often drives some of the best questions in theory," said Kulkarni, = whose=20 interests extend from signal processing to philosophy (he teaches an=20 undergraduate course and has cowritten a forthcoming book with Professor = of=20 Philosophy Gilbert Harman).

Kulkarni, who also is master of = Butler=20 College, said that he and Clancy=20 Rowley, assistant professor of mechanical and aerospace engineering, = are=20 hoping to inspire a team of undergraduates to focus their senior theses = on the=20 solar power project.

"It's exciting to have this real = experimental rig to=20 test out work that is often done through computer simulations," said = Rowley, who=20 specializes in control theory.

Joseph Montemarano, industrial = liaison for=20 the Princeton Institute for the Science and Technology of Materials, = also is=20 consulting on the project.

For the past two years, the University = has=20 been using another of Princeton Power's products -- a beta version of a=20 high-efficiency variable speed fan controller -- on the cooling tower of = the=20 cogeneration plant on Elm Road. It is one of 12 fans that chill water = for 87=20 campus buildings.

The company is one of a growing number of = startups to=20 emerge from electrical engineering professor Ed Zschau's highly popular = course,=20 "High-Tech Entrepreneurship."

Princeton Power is headquartered = in office=20 space on the Forrestal Campus, but the young engineers consider a couple = of=20 downtown Princeton coffee shops their auxiliary offices of sorts. They = had their=20 first meeting with entrepreneur and private space traveler Greg Olsen, = who has=20 invested in the company, at Starbucks. And they often confer with = Kulkarni at=20 Small World.

The solar panels on the Engineering Quadrangle will = produce=20 three kilowatts of electricity, which is about what the average house in = New=20 Jersey consumes.

Princeton Power believes that its inverters, = which have=20 been tested in computer simulations but not yet in real-life New Jersey = weather=20 conditions, may represent a 75 percent efficiency improvement over other = inverters currently available.

The roof-top panels at the = engineering=20 school will be shielded by a brick parapet. "They should be invisible = from=20 street," said Roland Heck, associate dean for administration at the = engineering=20 school.

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Professor of Electrical Engineering Sanjeev Kulkarni (center) and = Assistant=20 Professor of Mechanical and Aerospace Engineering Clancy Rowley (far = left) are=20 collaborating on a solar energy project with Princeton Power Systems = founders=20 (from left) Erik Limpaecher, Mark Holveck and Darren Hammell. In the = foreground=20 is a solar panel similar to those that will be installed on the = Engineering=20 Quadrangle roof.

Photo: John Jameson

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Collaboration with start-up company aims to improve efficiency of = solar=20 power

by Teresa Riordan =C2=B7 Posted September 21, 2006; 03:59 = p.m.