24 x Solarworld USA 280 Watt PV Modules
The solar array consists of 24 modules arranged in 3 strings of 8 modules each.
3 x ABB PVI-3.6-TL-OUTD-US-A
The PV system uses 3 single phase ABB inverters, each feeding back to a different phase of a 480Y/277V service.
24 x TIGO TS4-R-S Safety/Monitoring Modules
Each PV module attaches to a TIGO TS4-R-S Safety/Monitoring unit that provides module level monitoring and rapid shutdown capability.
ABB VSN700-03 Data Logger
The ABB Data Logger provides logging and internet access for inverter output from all 3 PV inverters in the system as well as weather station monitoring.
TIGO Cloud Connect
The TIGO Cloud Connect provides logging of TIGO module level monitoring data. If also acts as an internet gateway to upload data to the TIGO web monitoring portal.
CLOUD CONNECT DATASHEET
ABB VSN800-14 Weather Station
The ABB Weather Station provides instantaneous reporting of local weather conditions at the array location.
WEATHER STATION DATASHEET
ABB AuroraVision Web Portal
The ABB AuroraVision Web Monitoring portal provides online monitoring of ABB Inverter and Weatherstation data. Inverter data is stored at 15 minute intervals.
The Bunger-Henry PV Array layout was designed with the fllowing goals:
While the location and layout are not optimal due to shading from the nearby penthouse and ductwork, it is more than adequate for research purposes.
The Bunger-Henry array has the following orientation and tilt:
The 180° azimuth is perfect for solar generation and the 10 degree tilt, while not optimal is used in order to allow for lower ballast loads. While a 30-35° tilt angle would be optimal for this location, it is not practical for ballasted systems due to the additional wind loads incurred and extra ballast that would be required. See the following simulation reports.
Since this system was to be installed on a flat roof, a ballasted racking system was chosen. These systems use a ‘ballast’, in this case 4x8x16 cement blocks, to weigh down the array. The amount of ballast is calculated based on wind loads for the area and terrain. One of the main benefits of a ballasted racking system is that it does not require any roof penetrations so the chance of roof leaks are kept to a minimum.
The racking design was provided by the UNIRAC online design tool. The design tool takes visual layout of the array along with the location, height and other parameters then applies ASCE (American Society of Civil Engineers) (ACSE 7-05 & ACSE 7-10)and IBC (International Building Code) standards for wind, snow and seismic loads to arrive at the specific ballasted design.
SEE RACKING DESIGN REPORT
Since any rooftop PV system, ballasted or attached, imposes an additional load on the building structure, a structural engineer needs to examine the building structure as well as evaluate wind, snow and seismic loads to make sure that the building can support the additional loads and that the array design will withstand the wind and seismic loads. For commercial designs, a stamped PE letter from a structural engineer is generally required.
PE LETTER: RACKING DESIGN
PE LETTER: POST INSTALLATION
The basic design requirements are as follows:
In order to accommodate the requirements for 480Y/277V and per phase power factor adjustment, 3 ABB-PVI-3.6 single phase 277V inverters were selected. Due to the roof space limitations and minimum voltage requirements, a single string of 8 modules per inverter was the optimal choice. The map of Tigo modules and wiring is shown in the following document.
Any PV installation should be in compliance with the National Electric Code (NEC), International Fire Code (IFC), International Building Code (IBC) and International Energy Conservation Code (IECC). The engineering package contains the code list of the different applicable codes along with data sheets, engineering documents and other information.