Brewster DG/Community Solar

Brewster Cheese Plant and Summit Ridge Energy created a partnership to develop 22.66 acres of renewable energy. The power generated from the utility scale solar field behind the Brewster Cheese Plant would serve two purposes. One, to provide an alternate renewable power source for the cheese plant – creating the distributed generation side of the solar field. The second, a community solar field to provide renewable energy to be exported to the ComEd utility grid for the local area to use.

The construction of the 22.66-acre site started in June 2020, however much of the planning and equipment and materials were ordered well in advance. The site was prepared and the construction was started. While the general contractor was having the site surveyed, PDC took the opportunity to plan and layout the underground conduits that would return power from the 30 inverters amongst the rows of solar panels. All power conduits would converge and terminate at the two 3000 amp switchboards on the north side of the solar field. Each conduit feeder had to be traceable and carefully laid out as to maintain the specified separation from the communications conduits and controls conduits. Each of the 3000-amp switchboards fed back to 2000 kw transformers within 50 ft of the switchboard. Power would then flow back to the respective source. For the distributive generation side, the 13.2 kv power would have to be trenched and line bored from the transformer back 812' to the 13.2 kv switch at the Brewster Cheese Plant. The community solar side would flow back to the utility grid on a 34.5 kv line 680' to an overhead metering point to tie into ComEd's power lines.

Power from the solar panels flows back to each inverter mounted in the solar field. Each site is comprised of 6,760 solar modules. The site used 400 watt Talesun Bistar module. The total of 13,520 modules were divided between a total of 30 CPS 125kw solar inverters, with 15 inverters going back to their respective 3000-amp switchboard. Wiring between the inverters and solar modules was completed with #10 gauge 2000 volt PV wire. The entire site used the equivalent of 41 miles of #10 gauge PV wire. The inverters convert the 1,471 DC voltage to 600 volts AC and send the power back to the switchboard.

Site Challenges

Many of the difficulties in the construction of the site stemmed from the terrain. The rolling hillside that the site was constructed on, lead to challenges during a wet or stormy day. On those days, there was a chance for equipment to slide on the grass or mud, which could've resulted in damage. Special consideration had to be taken on a site like this, with the hills to factor in and where all of the work was completed outside. Weather had to be continuously monitored for storms, especially those bringing lightning. PDC enacted a lightning alert system for any storms in the area. PDC mandated all employees had to seek shelter if there was a lightning storm within 10 miles of the site, remaining sheltered until lightning cleared from the radius. Along with storms, while working outside employees also had to monitor for heat exhaustion and take the appropriate steps to prevent this.

Construction of this size also required the need for additional employee training in order to work safely in the trenches. As part of the PDC safety protocols, all trenches were to be covered up or filled in at the end of each working day. This required a lot of communication and coordination with the other contractors on the site. The construction of the concrete pads for the transformers and service equipment took a significant amount of time as the natural site elevations were not conducive for a standard installation. On the community solar site there was a 22" grade difference in a 20' span from the south side of the pad to the north side, with an 8" fall from the east side of the pad to the west. This required additional fill and grading to be installed to make the site stable for the 13,614 lbs transformer.

The distributive generation pad layout was not as extreme as the community solar side. However, the pad had to be relocated after it was surveyed out. It was relocated due to a natural water way from the hillside that ran through the middle of the service. By relocating the pad, the natural water way could remain, and it also allowed for the pad to be placed on a more level surface.

Testing and Quality

An important aspect of the solar field is the 25-year life expectancy of the site. Extra steps were needed to ensure the quality of the installation; from the concrete testing of all structural pads to the very low frequency (VLF) testing of the medium voltage cables. This also included voltage and insulation testing of the 600-volt distribution power cabling. The DC wiring was tested with a Solmetric PV1500 IV curve analyzer. This test checks the DC string circuits while they are connected to the solar modules. This test provides additional information, such as amperage, voltage, and solar irradiance.

During the installation of the DC string circuits, PDC was able to layout pathways and conduit runs to maximize the wire use. PDC was able to prefabricate wire spools to combine multiple cable lengths to minimize the staging time to pull in the wire on the construction site. String circuits could range from 40-760' depending on the location for the solar inverter. The time used in the warehouse to measure out wire lengths and label wires reduced the number of electricians at the site that were needed to install the wiring.

This solar project was the first one of this size and scale for PDC Electrical Contractors.

Brewster Community Solar

• Fixed tilt solar array @ 25 degrees
• 11.33 acres of land
• 2,704 kw DC power / 1,850 kw AC
• 6,760 Talesun Bistar 400 watt solar modules
• 1,471 volt DC string circuits
• 15 CPS 125 kw solar inverters
• 260 total DC string circuits
• 34.5 kv medium voltage distribution grid
• 600v AC low voltage distribution

Brewster Distributive Generation

• Fixed tilt solar array @ 25 degrees
• 11.33 acres of land
• 2,704 kw DC power / 1,850 kw AC
• 6,760 Talesun Bistar 400 watt solar modules
• 1,471 volt DC string circuits
• 15 CPS 125 kw solar inverters
• 260 total DC string circuits
• 13.2 kv medium voltage distribution grid
• 600v AC low voltage distribution