Photovoltaic Electricity (PV) or SOLAR POWER is the center of renewable energy generated electrical production at Green Alchemy Farm.
In the summer of 2013, Green Alchemy Farm added an additional 8.55KW grid-tied array. The following system components make up this roof-mounted PV system:
- (30) 285 watt Mage PV panels in 3 strings of 10
- SMA-America 7000-US grid-interactive inverter
For a description of how we or anyone could determine how to install their own solar system, we will describe below the
development of the 2003 5.55Kw PV install as an example.
In 2003, Green Alchemy decided to install a 5.55K (Kilowatt), grid-tied, battery interactive PV system, one of the first in Berks County, Pennsylvania. The system components are comprised of:
- (3) solar arrays of (10 )185watt,24 volt, single crystalline Sharp PV modules
- (3) combiner boxes and 3 DC surge protectors
- (3) MX 60 Outback MPPT charge controllers
- (2) 5548 Xantrex inverters
- Battery bank of (24) 2-volt GNB Absolyte IIP100A-23 cells
Green Alchemy farm is at 40′ latitude and a NASA site was originally used to initially predict seasonal solar insolation over 1 year. This is a valuable site for one to determine potential power production at a particular latitude with a fixed array, single axis tracker and a double axis tracker. An array should point true south and this is determined by local magnetic declination which for Green Alchemy farm was 15′ west of magnetic south.
Green Alchemy chose a 3 array set-up: 2 fixed pole mounted arrays and 1 roof mounted array with (10) 185 watt – 24 volt modules each. The pole mounted arrays are fixed at true south, but are using a DP&W adjustable racking to adjust altitude angle from 15′ to 65′. The roof mounted array is fixed at close to true south by building, but can also adjust altitude angle at either 35′ (roof pitch) and 60′ in winter. The following chart shows optimal tilt angle for maximum solar insolation per each month of year here at Green Alchemy farm:
Obviously a dual axis tracker would be your most efficient mounting (see next graph below), but we chose all fixed-pole mountings with the addition of a roof array, because 3 fixed arrays would cost the same as 2 dual tracking arrays BUT without moving parts that could break!! The beauty of solar PV is that there are NO moving parts!
In each array of (10) 185 watt modules, 5 pairs of 24 volt PV modules were wired in series to attain the 48 volts required by the 5548 Xantrx inverters. At the combiner boxes the pairs were wired in parallel to increase amperage. From here the arrays go to a DC resettable surge protectors and on to DC disconnects before the MX 60 charge controllers.
The(3) MX60 Maximum Power Point Tracking (MPPT) charge controllers were new in 2003 and were chosen for their ability to increase power output of the PV arrays up to 30%. The controllers are current-limited to 60 amps and therefore, the manufacturer recommends not to exceed 46 amps of current input to get the boost. Each of the arrays has a capacity to produce 26 amps, too much to have 2 arrays per controller, but allowing maximum MPPT functional boost. See graph below to see how MPPT charge controllers work:
The (3) MX60’s interact with a 48 volt battery bank. A set of GNB Absolyte II 100A-23 batteries was installed. This set is made up of (24) 2-volt cells in series providing about 66.5 KW Hours of storage. These batteries are maintenance free and require no venting, so they were installed in the electrical room. The complete bank is comprised of (8) 6-volt battery modules.
Up to now everything has been DC, now we connected the batteries to the(2) SW5548(TRACE) Xantrex inverters. This inverter was selected because of its long track record and its ability to function in both stand-alone and grid-intertied situations. In example, when grid power is down or I shut off the grid, this inverter will continue to function as a “Stand-Alone” system. Two inverters are used to provide 240-volt power. The maximum rated output of each inverter is 5500 watts. The maximum rated pass through current of each inverter is 60 amps and can surge to a peak of 78 amps for motor starting.It can produce a continuous 46amps.(2) arrays were connected to 1 5548 and the last array to the other 5548. It is our goal to attach a Jacobs 110 volt wind turbine to this inverter with a Midnight Solar MPPT controller. This system has met 85% of all our electrical needs on Green Alchemy Farm.
Click the photos below for more information.
Green Alchemy provides valuable consultation for Solar PV installation for the “Do-It-Yourselfers” who need that extra information to fill in the blanks.
We provide Solar Site Analysis at $100/hour plus mileage. Solar site analysis includes:
- Orientation – Azimuth and Altitude angle as well as magnetic declination information
- Tilt angle – Optimal tilt angles of your array by your latitude
- Solar access – Using a Solar Path Finder we can locate the optimal site for your array minimizing shading throughout the year—WHAT IS Your Best SOLAR WINDOW!!
- Practical determinants – Consideration of loads, local climate characteristics, distance from power conditioning equipment, accessibility for maintenance and of course best mounting options for your site.