Solar on Campus
- Written by David Wagman
Perhaps the biggest drawback to renewable energy systems like wind generators or solar panel generation is the inability to schedule the wind and solar energy. Despite the difficulty, these intermittent sources need to be coordinated with the power system as more of them come online or go off line.
If large electric storage systems are available, the renewable energy can be stored until needed by the electric grid. If plug-in hybrid vehicles are available in large numbers, the rate of battery charge or discharge can be scheduled to coordinate with the intermittent wind and solar energy. Related opportunities and challenges range from the need for economically viable and technologically efficient storage as well as the growing need to provide reactive power and frequency support for system stability.
A smart grid would make it possible to island parts of the electric system from the main grid when main grid prices are high or when it is blacked out. The concept would need intelligent agents to manage the island until it is reconnected to the grid.
Islanding can be particularly important in university and research settings where power disruptions can be potentially devastating to experiments and energy—dependent research projects. The Illinois Institute of Technology, for example, estimates it experiences three or more power outages each year, at a cost of up to $500,000 annually in restoration expenses, lost productivity, and ruined experiments that often cannot be recovered. The Institute is working to protect itself by building a new power delivery system that reduces its vulnerability to blackouts and enhances its ability to add renewable generating capacity to its power supply mix.
William Paterson University in Wayne, New Jersey, took a different approach. Rather than reengineer its internal power grid, the school contracted to build a 3 MW solar PV array. Its primary goal was to reduce its electricity bill, but the behind-the-meter installation opens additional possibilities for future smart grid functionalities that can enhance the system's efficacy for its university host and for the larger regional grid.
An early plan to site solar PV on some of the university's classroom rooftops was set aside due to cost and lack of space from existing heating, ventilating and cooling equipment. Then SunDurance Energy designed and presented WPU with a solution that used elevated solar canopies over several university-owned parking lots in addition to roof-mounted PV. SunDurance ran the numbers and found the approach both financeable and capable of lowering the university’s electric bills.
The option, however, presented engineering challenges such as drilling footers that reach into the shallow bedrock and bracing the tall structures against wind forces. It also presented economic challenges stemming from the cost of building atop campus parking lots.
These and other challenges were overcome and, since October 2010, the university has hosted a 2.7 MW solar PV array. (An additional 500 kW is expected to come online in 2012 atop a 1,100-space parking structure.) The university signed a 15-year power purchase agreement with Nautilus Solar Energy, which developed and owns the project. Through the PPA, the university cut its electricity bill 25 percent from what it had been with local utility, Public Service Electric and Gas. An escalator tied to the rate of inflation adjusts the rate every three years. "Over the life of the PPA, the university could save $4.3 million in electricity costs," said Steve Bolyai, the university’s vice president of administration and finance.
The PV array is set on precast foundations, 30 inches in diameter, sunk 6 to 12 feet in the ground, depending on the bedrock. The array is fixed in place and the panels are tilted at a 10-degree angle toward the south. A tracking system generally "doesn’t make economic sense in New Jersey," according to Al Bucknam, CEO of SunDurance, because New Jersey’s solar intensity is not high enough to justify the extra expense. Plus, a tracking system’s moving parts can reduce reliability and increase maintenance costs.
Compared to a traditional ground-mounted system, the William Paterson project had to span longer spaces with fewer columns to accommodate cars and pedestrians moving beneath it. Wind and snow loads also had to be figured into the project’s engineering specs. All totaled, the elevated array structure added around $1 per watt to project costs, Bucknam said.
The university considered a self-finance option to develop the project. That path would have seen it sell tax-exempt bonds to finance the investment. Bolyai said, "The university ultimately decided it didn't want to be in the power generation business and did not want to use up its bonding capacity for a solar energy project."
A second option was to pursue a public-private partnership. Through this model the university would put up no money but would partner with a developer, provide the land and become a long-term power customer.
The William Paterson project has proven to be a "classic behind-the-meter system" for developer Nautilus Solar, said Laura Stern, president. She and CEO James Rice started Nautilus in 2006, drawing on their expertise in power development and finance. “We came with the thesis we could apply typical finance structure of large-scale projects to distributed solar,” Stern said. In late 2008, the pair sold a majority interest of their business to Starwood Energy, a venture capital fund, which committed $50 million to investments. The finance and development model Nautilus first used in New Jersey has since been applied to projects in Connecticut, Maryland, Florida, California and Ontario.
The project received a $5 million, 10-year, interest-free loan from the New Jersey Economic Development Authority through a solar incentive program. That program quickly reached capacity and has since closed to other participation. The William Paterson project may be the portfolio's only project that includes a non-recourse loan and a third-party with a PPA. Stern said the loan proved “very helpful” in the months between first estimating both project costs and the value of available solar renewable energy credits (SRECs) and the time construction began.
"Prices in both these markets move," Stern said. "Then you're really juggling assumptions you made nine months ago with current market dynamics." The loan has a 10-year term, but will be "significantly shorter as we accelerate amortization," she said.
A quirk in New Jersey's market structure has worked to depress SREC prices in recent months. Although the market is growing in liquidity and depth, the only public record showing capacity in the SREC market comes from a list published by the Board of Public Utilities. But discrepancies can develop between the number of credits applied for and the number of projects that actually move forward. Currently, there is an undersupply of SRECs; however, according to Stern, the market can carry a lot of "bragawatts," in which developers apply for credits but then fail to develop the project. SREC buyers can perceive the market as being oversupplied, which lowers the forward curve of SREC prices.
"This is a very New Jersey-specific structure" not seen in other markets where Nautilus is active, Stern said. “The market mechanism works and will ultimately determine the correct level, but it’s a risk that market participants should evaluate carefully."
Siting solar PV on a structure atop a parking lot can make sense where vacant land or suitable rooftops are not available, Bucknam explained. "A lot of buildings have HVAC on the roof" or the roofs themselves may need repairs or reinforcement to support a structure. A parking lot may not always make sense; particularly if it is on the shady, north side of a building or otherwise blocked from the sun.
Another consideration is the disruption construction can cause for commuters. SunDurance coordinated deliveries and construction activity to make the most of available laydown space and avoid taking away too many parking places at any one time.
The university also insisted that, for public safety reasons, lighting levels beneath the structures be at least the same as they were before construction. Bolyai said lighting levels actually improved after construction. The additional operating costs for the highly efficient lighting fixtures installed on the structures are passed on to Nautilus.
Future thinking might include how to expand the university’s PV system to accommodate plug-in hybrid vehicles that commuters may bring onto the campus, how the system can better improve system reliability in the university’s semi-rural setting, how energy storage systems with a "self-healing" grid can enhance electric security, how the university’s array can become an emergency backup power asset and how the system can provide ancillary services for grid management as well as a source of energy for peak load management. Addressing these issues would go a long way towards moving the PV system from a fairly conventional solar installation to a showcase for a variety of smart grid applications.
In the end, solar turned out to be the "right thing to do" for William Paterson University, Bolyai said. The project has been well received on campus, gives the university more predictable electricity costs and improves its sustainability profile. Plus, the elevated solar panels offer a shady parking place on hot, sunny days.
A version of this article originally appeared in the March/April 2011 issue of Renewable Energy World North America magazine.