About a mile south of campus is a 27-acre field of solar panels that generates 5.5 percent of the University’s power. Of all the University’s clean energy efforts, this solar field has a relatively small contribution — at least on paper. Despite this technicality, the solar field is a key contributor to the University’s status as a leader in sustainable energy.
The solar field’s contribution to the University’s carbon footprint is measured through Solar Renewable Energy Certificates, or SRECs. For each megawatt-hour of clean energy that a company produces, it earns one SREC.
SREC’s can be bought and sold, according to New Jersey law. This process transfers credit for the production of clean energy to an SREC’s new owner. Since New Jersey state law requires that a certain percentage of companies’ total energy production is clean, corporations that do not want to invest in creating their own clean energy can compensate by buying SRECs from others in order to meet the state minimum.
Though the University earns SRECs from the energy its solar field produces, the University currently sells those SRECs to pay off the initial loan for the solar field, explained Engineering and Campus Energy executive director Thomas Nyquist. As such, the SREC-measured value of the energy produced by its solar field is masked, at least on paper.
According to Nyquist, the University will start taking credit for the solar field’s clean energy production once the field’s lease is paid off around 2020 or 2021.
“It might take five or ten years, or even fifteen years to pay off,” said energy plant manager Ted Borer. “But we [the University] expect to be around forever, or at least for another hundred years so we can think that far forward, so we can tolerate a long payback period.”
During the day, 75 percent of the field’s solar panels change their angles to follow the sun and maximize their energy production. The rest face south to gain as much solar exposure as possible.
Large-scale carbon emission reduction projects like the solar field and the co-generation power plant are more feasible for some entities than for others. They require a large financial investment and take some time to produce a benefit that outweighs those costs.
The University’s most prominent clean energy goal is to reduce carbon emission levels by the year 2020 to where they were in 1990. Even without the solar field’s contributions, this goal appears to be within reach. Campus emissions have significantly decreased in recent years — even in the face of extensive new construction, which has increased the campus’s energy demands.
Practically — since the sun is not always shining — the University’s solar field cannot consistently produce energy. This means that while it significantly reduces the total amount of energy that needs to be purchased, it cannot be relied upon the same way in which the power plant is.
“I look at the gas turbine generator as something I can use to address the immediate needs of the campus. The solar field really displaces electric purchase over the span of a year, but I can’t count on it in any given moment,” said Borer. “So that is less predictable generation.”
The solar panel field is also not connected to batteries, so its energy is stored using a different method. Its electricity is, in effect, stored as thermal energy: It is used to heat and cool water that is stored for later use.
“Building a whole power plant and especially a steam system takes a forward vision — it takes a long-term view,” Borer said.
This article is part of a series The Daily Princetonian is undertaking about the University’s power plant and its energy needs.