In the renewable energy world, the 115-kilowatt solar array under construction on the roof of Bedminster, N.J.'s Public Works building is nothing special. But when viewed with 37 other mostly small-scale installations across northern Somerset County that have pooled resources to afford solar installations, Bedminster is part of a veritable 7-megawatt powerhouse.

Each individual installation contributes to that powerhouse under a roughly $35-million county initiative to install rooftop, ground mount or canopy solar panels on government buildings and schools that are structurally sound enough to support them. Morris County devised the aggregated-site solar program, backed by a private contractor, to build a 3.2-MW system last year. Since then, Morris has embarked on a second program, or "tranche," and a small but growing number of counties are following suit and several others are considering it. Somerset has the largest program so far.

Under the initiative, a county enters a 15-year power purchase agreement (PPA) to buy sun-powered electricity at fixed, discounted rates from a private owner-developer. The county sells bonds to pay for most or all of the project that the developer pays back over time. The developer, which owns and maintains the system, pays the remaining project costs if applicable, thereby ultimately footing the bill for design and engineering, installation and construction of multiple solar systems on public buildings countywide.

For participants, the PPA offers reduced energy costs and protection from price fluctuations, says Stacey Hughes, principal at SunLight General Capital, New York, the owner-developer for Somerset's program. Besides electricity payments from program participants, the developer gets the right to collect solar renewable energy credits (SRECs) generated by the installations that can be traded in New Jersey's SREC marketplace. SunLight General was also able to take advantage of the now-expired Treasury Dept.'s 1603 cash grant program for renewable power projects last year to do this tranche.

For Somerset's tranche 2, the SCIA issued nearly $24 million in 15-year bonds to cover about 70% of the cost. SunLight General financed the rest.

Like Morris County, Somerset launched two aggregated-solar programs separately: Tranche 1, an 8-MW project that was completed last year, spans the county's southern region, and tranche 2, now under way, crosses its northern section including Bedminster.

New Jersey county legislators have had a long history of sharing services and pooling financing for building libraries or repairing sewer systems, says Steve Pearlman, partner at law firm Inglesino, Pearlman, Wyciskala and Taylor, Parsippany, N.J., which on this project represents the Somerset County Improvement Authority (SCIA), the county's financial services arm. But Morris County was the first to apply this approach to solar, he says. The idea has quickly caught on, says Pearlman, who also represents other county improvement authorities including Morris.

"It's important to aggregate projects throughout the county because no one project alone would have been big enough to receive investor financing," says Edouard Klehe, principal and COO of SunLight General. "It takes at least a $30-million- to $40-million-size project to attract investors." Without investor attention, most municipalities would not be able to afford solar, he adds.

The SCIA hired Birdsall Services Group, Voorhees, N.J., to consult on both tranches. Birdsall began its job by surveying local authorities for some 300 possible installations, asking for such information as current energy consumption and available space. This group was gradually scaled back as sites were found to be "unviable"—or unable to support the solar system's structure—says Jessica Vogel, Birdsall senior energy engineer. The chosen sites were then divided into the two tranches. "You can't have, say, 14 megawatts in one [tranche] program—that's too much. We wanted to have a time frame of one year to do this in," she adds.

Site-selection criteria included rejection of roofs older than 10 years and of most sites that could not accommodate a system larger than 30 kW. A few exceptions were made to the latter, however, for towns that "really wanted to be part of this" but had only enough viable space for single-kW installations, Vogel says.

"Probably the most important thing of this whole process is meeting with each of the local authorities with our proposed drawings," Vogel says. "You do this before you go into the RFP to make sure the local unit is comfortable with what you have." The process allowed Birdsall to discover "interesting things," such as in one case, leaks in a five-year-old roof that had initially been accepted into the program. The roof had to be taken off the list.

Bedminster is the first of the tranche 2 sites to start construction. Prime contractor MasTec's Wanzek Construction unit began work at Bedminster in January and is installing 393 polycrystalline panels on 12,540 sq ft—or about 90%—of the roof, says Tom Kosto, Wanzek project manager for tranche 2. "Because it's the first site, we're waiting for specific materials, which took a little more than a month," Kosto says. "But typically a site this size would take two and a half to three weeks for installation including the direct current (DC) wiring to the inverters." After installation, the team must wait for approvals from the utility and other entities before starting the system up.

The system operates by sending DC from the photovoltaic cells via a cable to the site's power inverter box, where it is converted into alternating current. The power then travels to the main distribution panel for use by the building.

When completed later this month, the Bedminster system will have the capacity to supply about three times the Public Works building's electricity needs. As a result, Wanzek is linking the system up to the police station next door to supply more than half of its needs, Kosto says.

Bedminster has a "typical" system setup except that "you normally don't have solar panels on a roof of one building, supplying two buildings," Kosto says. "But it made sense here" because the panels would generate too much power for just the one building.

There are only a few things that can be called "typical" with these projects, Kosto says. "One of the hardest parts about building these is that the number of installations can change" over the course of the project, he says. That is because, in the early stages, it is difficult to gauge with any certainty which sites will work structurally.

Tranche 2, which was engineered and designed by Wall, N.J.-based Innovative Engineering, has "about 38 sites now; originally it had 44, but 11 fell off, and then some were added, so right now the total is 38," Kosto says. Four of the 38 are at one location, though, the Somerset County Vocational Technical High School in Bridgewater, which consists of three rooftop arrays and one canopy for a total of 899 kW.

"There's a lot of engineering that takes place with these projects, because each individual site requires the same amount of engineering—your layout, surveying," et cetera, he says. By the time tranche 2 is completed this October, the team will have worked on at least 50 sites, although some of those would have eventually been deleted from the project list as they are found to be unviable.

That fluctuation is common for this type of project, which is "100 times more complicated to do than a single solar farm," such as Mercer County's planned 10-MW farm at its West Windsor-based community college, Hughes says. "One of the big challenges is that you have to involve every entity and their decision maker—which could be three to four people per town—in the process," she says. "Reaching consensus is hard. Also, the project takes a lot longer because of all the paperwork, the permits town by town, and every town's [procedures] are different."

The tranche 2 project team will do the bulk of the installations over the summer, with its last and largest project—a ground-mount 1-MW installation at the site of a Bridgewater baseball stadium—to start in mid-August.

Hughes says these types of privately backed programs may spread beyond the state, depending on whether other states establish New Jersey-like SREC programs. "But I don't know of any other models like this outside of the state," Hughes says. The program is "a win-win for the county, the [public buildings] that have the systems and, obviously, the environment."

PROJECT TEAM Owner/Developer/Installer: SunLight General Capital Client: Somerset County Improvement Authority project manager: MasTec Engineering and Design: Innovative Engineering Consultant to SCIA: Birdsall Services Group