The completed Bergey Excel-R, 7.5kW wind turbine on an 80 foot guyed lattice tower.
Carr wind/PV grid tie, Ellensburg, WA, 2005/2006
The Ellensburg, WA, area is renowned for consistent high winds, and commercial wind farms are being built nearby. Dr. Marilynn Carr had been interested for many years in using the wind resource at her farm/orchard to produce most of her power, and have backup power from wind and PV. She monitored the wind resource for two years and recorded 13 mph average annual wind speeds, an excellent resource for a small wind turbine.
After a site assessment and learning the alternatives available, Dr. Carr selected a Bergey Excel-R wind turbine (the 7.5kW battery charging version of the Bergey Excel-S 10kW turbine) and a Uni-Solar Building Integrated PV (BIPV) array of twelve PVL-136 “peel and stick” solar modules (1.6kW).
Dr. Carr also decided to house the battery and inverters in a new straw bale shed, fulfilling another desire to explore this building method.
The completed Bergey Excel-R, 7.5kW wind turbine on an 80 foot guyed lattice tower.
The completed Uni-Solar 1.6kW BIPV array on the straw bale power shed.
The power shed interior, with the HuP Solar-One 48v, 1,160 amp hour battery in an insulated, ventilated enclosure with automatic watering system; wind turbine disconnect and step down transformer supplying the Bergey OptiCharge VCS-10 48v charge controller with a PentaMetric meter monitoring both wind and PV input; OutBack MX60 PV charge controller, OutBack PS2 power panel with two OutBack GVFX3648 grid tie inverters (7.2kW), HUB4, and OutBack MATE system controller. The two kilowatt hour meters separate passed through grid power from renewable energy power to measure “Green Tags”.
The completed system meets Dr. Carr’s desires to produce renewable energy, have back up power, and be more energy self sufficient.
This was a technically difficult system. Some of the challenges included:
- The Bergey OptiCharge VCS-10 48v charge controller and step down transformer are not UL listed and the electrical inspector would not pass the system until a testing laboratory conducted a field evaluation to insure the components met UL standards. Intertek Labs conducted the field evaluation and certified the installation, at a cost of $3,600.
- Because the value of “Green Tags” is different for wind and PV, we needed to determine how much power each source produced. We used a PentaMetric meter, which can monitor three input shunts, to measure wind, PV, and battery current. We learned that while the PentaMetric can monitor three shunts, only shunt channels 1 and 2 can be displayed in watt or kilowatt hours, so we connected the wind and PV input shunts to these channels. This allows us to determine how many kilowatt hours each source produces. We use these figures to develop a ratio of wind to PV energy. This ratio is then applied to the total AC kilowatt hours produced by the system to determine the amount of AC power produced by wind and PV for “Green Tag” reporting.
After considerable effort we were unable to get the PentaMetric to accurately and reliably report PV and wind kWh, so abandoned the effort to separate the power source and report all Re produced as wind Green Tags (the majority of production and least value for Green Tags.)
- The OutBack grid tie inverters bypass grid power to supply backed up loads, and also use renewable energy to power backed up loads. To separate grid power from RE power, OutBack recommended using two kilowatt hour meters, one on each 120vAC leg of the 240vAC inverter output. The meters are wired to discount any grid power used for loads, while recording any RE power used to power loads or supply the grid. We learned these "5 jaw" meters require an adapter be installed in standard meter bases to accept the 5th jaw (neutral.)
- The HuP Solar-One battery allowed for a large capacity battery bank, required for the wind turbine, in a small space with minimal cable interconnects. But it also required a lot of labor to clean and reassemble the battery trays after shipment, and build a vented battery box around the almost 4,000 pound battery bank.
- This is the first time we have used an automatic battery watering system, and although it took some time to assemble and install, it is very quick and easy to top off the battery electrolyte with distilled water. Update 2007: The battery watering system has overfilled some cells and failed to keep others full. The system has been removed and manual watering of cells is now being done.
- The OutBack PS2 power panel provided some unexpected challenges. The HUB4 communications manager, that links all the OutBack products, did not work properly unless the components were connected in a specific sequence - Master inverter first, slave inverter, MX-60 PV charge controller, and MATE system controller last. The inverters would not “sell” initially because we had turned the battery charger function off to avoid using grid power to charge the battery. After considerable searching through controller menus, and a call to OutBack, we learned that the charger function had to be activated, and go through an initial charge cycle when first connected to the grid, before the sell function would operate.