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This November 2011 the Energy Department's Brookhaven National Laboratory "flipped the switch" on the largest solar photovoltaic array in the eastern United States. The 164,312 solar panels hosted at BNL in Long Island, New York -- one of the largest solar farms built on federal property in the nation -- produces enough energy to power up to 4,500 homes. The 32-megawatt Long Island Solar Farm (LISF) Project is a collaborative project between the Long Island Power Authority (LIPA) and BP Solar International, Inc. (BP Solar). It is estimated to have the smallest carbon footprint of any solar array with its amount of output. Its 200-acre site is owned by US Department of Energy which helped attract investments from public and private sources, contributing to the project’s economic success and helping meet the US goal to reduce the country’s dependence on fossil fuels and foreign oil. It provides a significant source of clean energy for Long Island, as well as a positive economic impact for the local workforce and businesses. The project also helps New York state meet its goal of 30 percent renewable resources by 2015. (Scroll to bottom for additional resources)
In addition to providing thousands of Long Island homes and businesses with clean, renewable electricity, this impressive solar array will also offer Brookhaven Lab scientists a unique opportunity to study the challenges of deploying large-scale solar power installations in the northeastern U.S. These include the variable weather conditions that impact the array’s output on an hour-by-hour or even minute-by-minute basis. Understanding local ‘microclimate’ effects help scientists and engineers reliably integrate power from intermittent sources -- like solar and wind -- into the existing electric grid, and advance state and national renewable energy goals.
The Long Island Power Authority has a 20-year contract with LISF to take electricity produced by the farm and supply it to LIPA customers. Co-owned by BP Solar and MetLife through Long Island Solar Farm LLC, LISF will introduce approximately 50 gigawatt-hours per year of clean, Long Island-based renewable energy into LIPA’s electric grid. This also means the reduction of carbon emissions by 30,000 metric tons per year. These environmental benefits, combined with a thoughtful and comprehensive stakeholder engagement approach, helped the project earn the Best Photovoltaic Project of Year Award from the New York Solar Energy Industries Association.
A smaller solar installation will be built at BNL in the spring of 2012, to be completed later that year. It is designed to help scientists from universities, national laboratories and companies around the country test new solar technologies on a 5-acre test facility that will generate one megawatt of electricity. Scientists will use it to investigate technologies like photovoltaic components, energy-efficient batteries and "inverter technology.”
Blue Oak Energy began designing the Long Island Solar Farm in May 2009. Following are some of the challenges expected and encountered 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.
Long Island Solar Farm EIS Dec 2009 (2,508 kb)