Tracy Dahl Polar Field Services
Partner in CH2M Hill Polar Services
Chalet in summer
(E/S/W) solar PV to AGM type lead acid battery bank.
Toolik Field Station, Alaska
This NSF funded, summer-only science project has a fairly high power requirement (~500W continuous). It is located far enough away from the station to where an independent power supply became cost effective. The system deploys 24 Kyocera KD140 PV panels in three directions, providing solar input for approximately 20 hours per day. This greatly reduces the battery storage requirement. The innovative A-frame design for the E/W facing arrays serves a double function, providing minimalist weather protection for the back-up generator and power electronics enclosure. The design also allows snow to scour through it, preventing heavy snow drifting that could affect the science. The south facing array is fairly conventional, simply raised high enough to allow snow to scour under.
The PV input is regulated by three Outback Flexmax 60 MPPT charge controllers. Power output to loads is 120VAC @ 60Hz, via a sealed Outback FX1548 sine wave inverter. Outback components are networked via a HUB/Mate system. Power routes through a Bender GFCI protection device, which offers greater sensitivity to an actual ground fault, while eliminating nuisance trips. The 48 volt nominal battery bank could also be charged via a Honda 6.5kW sound attenuated generator. The Outback inverter has an integral charger, and combined with three Iota battery chargers allows for up to a 59A charge rate (~3kW).
This project is now conluded (Summer 2016). While in service, the multi-azimuth PV system worked so well that the
backup generator never had to be operated.
Operators ManualBuilding the Solar Chalet
Solar Generation: Three solar facets, each deploying eight 140 Watt Kyocera solar photovoltaic (PV) panels in three azimuth directions; east, south and west; 3.36kW total. A conservative 1kW average output over a 20 hour period results in up to 20kWh per day energy production, if the load demands it. The PV panels are wired in series/parallel configuration at 72 VDC nominal. The operating voltage from the PV arrays will typically be in the 80 – 90 VDC range.
PV Charge Control: Three Outback Flexmax 60, MPPT charge controllers, one for each facet/azimuth orientation. By utilizing three independent charge controllers, energy production across the three PV facets is maximized. Since the series voltage from the panels is greater than the nominal battery voltage, the MPPT functionality enables a greater energy harvest.
Engine Generator: Honda EU6500i, inverter based, sound attenuated, gasoline fueled generator. Capable of 5kW continuous power output with surge capability to 6.5kW. Exports 240VAC split phase at 60Hz to the power electronics enclosure.
Energy Storage: Two strings of Concorde Sun-Xtender 3050T AGM type batteries; 16 batteries total in series/parallel. 305Ah @ 6V X 8 = 14.64kWh per string, 29.28kWh total.
Battery Chargers: The FX1548 can output up to 20A @ . Three IOTA chargers can output up to 13A each. Engine generator is wired to feed the FX1548 and the science load on one 120V circuit, and the three IOTA chargers on the second 120V circuit. Up to 59A charge capability.
Metering: Outback Mate/Hub system provides high resolution monitoring at the system. Remote monitoring has not been implemented, but is possible.