Blue Oak Energy was fortunate to attend the ribbon cutting ceremony on November 18, 2011 for a project we began designing in May 2009. There was an abundance of enthusiasm, community support and sunshine at this event to celebrate full operation of this awesome solar electric system.
This project is known as the Long Island Solar Farm which is a 37MWp (32MWac) solar farm covering six distinct parcels of land within the confines of the Brookhaven National Laboratory property. Brookhaven National Laboratory’s role is to produce excellent science and advanced technology with the cooperation, support, and appropriate involvement of our scientific and local communities. As such, this solar electric system is an indicative example of their leadership in science and technology. Brookhaven is one of ten total national laboratories in the United States and is located in the center of Long Island in Upton, New York.
When we started working on the Long Island Solar Farm, we knew there were some challenges which could significantly alter the intended outcome of the project. The items below are some of the challenges we expected from the onset or discovered during the design process:
The site is surrounded by wetlands on two sides of the multifaceted perimeter. The required offsets from natural wetlands were considered and we took a conservative approach to ensure there was no encroachment on these important habitats.
- Native Species
A protected tiger salamander required zero disturbances in any native habitat areas. As a result of the tiger salamander habitat locations, there are several radii in the solar array property which allows designated setback.
- Crossing the Long Island Rail Road (LIRR)
Crossing a railroad easement with the electrical conductors which deliver the solar farm’s energy to the Long Island Power Authority’s substation was all new to us. We obtained a permit from the Long Island Rail Road to provide a path for the solar farm’s conductors.
- Governmental Entity
Ok, we have done governmental projects before but we did not know what it would be like to help secure easements and lease land from the US Department of Energy (DOE) and Brookhaven National Labs (BNL). In fact, the DOE and BNL turned out to be great partners.
- Native Pine Barren Forestland
There were trees and undergrowth removed from this site to accommodate the PV system. However the designated Central Pine Barrens forests were untouched. We worked diligently with the Pine Barrens conservancy group to ensure there was no harm to this native forestland. Boundaries were surveyed to ensure any development was within the land areas designated for development by the conservation.
- Topographic Variation and Grading
There was a major effort to remove the existing vegetation but not change the current topography of the site in order to ensure the same drainage patterns to the wetlands. As a result the non-uniform site ranged from nearly flat to hilly across the field. We were able to design the site in three dimensions in order to ensure the shading, ground clearances and spacing was properly accounted for in order to match the energy production & economic models remained valid.
- Conductor design Based on Soil Resistivity
The underground solar field electrical conductors were specifically sized for the soil resistivity, which is a measure of how much the soil’s properties will resist the flow of electricity. It is an important factor in designing an efficient underground electrical system. The soil resistivity and how it varies in the soil is also necessary to properly design the electrical substation’s grounding system.
- AC Collector System: 34.5kV versus 13.8 kV
The solar farm contains 25 each 1.25MVA inverter stations which covert the solar array direct current to alternating current. We had the opportunity to choose 13.8kV or 34.5kV voltage class electrical “collector” system gear. The higher voltage equipment is more expensive, but the high voltage requires less conductor area to transmit the current. A detailed engineering cost study revealed that the 34.5kV collector system was the best choice for this solar farm.
- Step-up Transformer
The solar farm’s alternating current collector system delivers electricity at 34.5kV. But the interconnection voltage to the Long Island Power Authority is at 69kV. We used a central step-up transformer at a median location in the array field to transform from 34.5kV to 69kV. This step-up transformer has a long delivery time and thus a potential failure of this critical component could shut-down the facility for months. Therefore, the development team chose to site a spare transformer at the site which allows for quick replacement in the event of a failure.
- Transformer Oil Containment
The transformers all use environmentally friendly and biodegradable mineral oil. However, we still chose to design an oil containment feature at each transformer to collect the oil in the event of a transformer failure.
- NYISO System Impact Study
The interconnection queue at the New York Independent System Operator required completing the interconnection process through a cluster study. This put the solar farm in the interconnection study process with other projects which change the major supply or demand of electrons to the state’s grid. The whole study process took about 12 months from initial application to final approval.