pgtruspace's blog

about things that interest me.

Monthly Archives: August 2021

8 Kw of PhotoVoltaics

Another project underway.

40 Photo Voltaic panel array

40 – 200 watt Sanyo PV panels installed on a wooden rack with a winter orientation. The panels are arranged as shingles to provide a dry area under them for the wooden framework as well as a place for power management and battery storage area.

You will notice the steep angle of the panel array. This is to maximize the winter production at the expense of summer production. The best average inclination is the same as the Latitude of solar collection, then plus up to 15degrees for maximum winter power production, or less up to 15degrees for summer maximum production. The angle of the Solar Collection Panels is best set at 90degrees to the Sun but in a fixed array one must compromise to produce the most advantageous output for the position of the Sun available as well as time of year needs. In this case I opted for a winter angle. Giving up summer production in favor of greater winter production. This has the added benefit of reducing the array’s foot print, fast snow removal, and ease in cleaning

construction started
40 panels with outriggers
30 panel rack design

This spring, a bunch of used lumber became available to create the rack to mount them on, so I built it on the space available that had a suitable “Solar Window”, something not common in the woods.

I first planned on a 25 unit system but as I designed found that a 30 panel rack was possible on the base created because of the steep winter angle. After much consideration that grew to 40 by adding outriggers on the ends. An important part of the design was to shingle lap the panels to provide a dry environment for the wood frame and equipment below.

Now that it has been built I found that the best “window” available is where the green pickup was parked so I moved the pickup as well as the old equipment behind it. Now at this point the entire rack has been moved about 15 feet to the south., But that will increase the usable “window” from 6 hours to 8 hours. A gain of nearly 10% in possible energy production. 8 hours is about the maximum effective “solar window” that a fixed array can utilize. When you build in the woods tall trees cast long shadows. But an added benefit of the move is that I can add another row of 8 panels along the bottom of the rack frame because of abrupt elevation change of ground level at this point. As the seasons progress I can evaluate the sun and shadows cast to determine the final placing of the rack. a nice side effect from building the rack on a skid that can be moved.

The project begins.

Nearly 3 years ago we had the opportunity to buy 50 used, 200watt 10year old Sanyo panels for a very good price and brought them home.

stack of Sanyo PV panels

Sanyo HIP205-BA5 Photo Voltaic panels

Max Power 205 watts

96 cell ( 48vdc )

maximum voltage 68.8vdc

maximum current 3.8 amps

maximum operating voltage 56.7vdc

To this we added used Enphase inverters also at a cheap price.

enphase Micro Power Point Tracker…mppt controller

enphase M190-72-240-12s

Enphase Micro Power Point Tracker – mppt controller/inverters

M190 – 72 – 240 – s12, 190watt – 72 cell ( 36vdc ) 240vac, split-phase

22 – 40vdc input ( that is about 6amps at 40vdc )

240 vac – 0.8amp output split phase ( that is 120vac – neutral- 120vac or 240vac )

12 panels temporary set up in field

A dozen were set up in an open area with salvaged individual grid-tie controllers but the mis-match involved yielded very little power.

At best 3 amps at 240vac. from the 12 units at right. The ( 96cell ) panels can only output 3.8 amps @ their peak effective 57 volts to create 200 watts.

Solar panels are limited in their output amperage, in this case 3.8amps so that the panels could not develop enough energy to really load the controllers that wanted over 6 amps @ at least 40 vdc (72 cell) to power 190 watts. The panels open voltage is over 68vdc (96 cell) so if the inverters cycled off for any reason they would not turn back on during that day due to High voltage at the input. But if on, would drain the panel below the needed 22 volt operating voltage. This effort to generate useful power was abandoned.

Then it was possible to build the rack and mount 40 panels! As I was mounting them up I discovered why the inverters were not working direct drive from the Solar panel as they were designed to do. I was hooking 36 volt(72cell) inverters to 48 volt(96cell) panels. By loading the buss with 36vdc of batteries I could sink the Solar panels output voltage to within the operating voltages of the inverters that were connected to the buss. Wow, they all worked ! Over 2Kw output to the grid.

At first I installed a large number of used Lead Acid batteries but soon found that they were inadequate for the job. They have narrow window of working voltage and their output is very limited. A 40Ah Lithium battery will store and output several times a comparable Lead Acid battery and last 10 times longer under sever use. So I was able to pick up 12 – used 40Ah LiFePO4 to replace 15 – 80Ah lead acid batteries

Valence 40Ah LiFePO4 battery

Valence 40Ah

To this I have added 12 used LiFePo4 batteries. These have built in controllers that make the batteries mimic 12volt lead acid batteries operating voltages. All this equipment. has been included in the erected system, and a bunch of wire and connectors has arrived so I can start hooking up things.

Now to put what I have learned from my mistakes into practice within this rack. Panels in series and parallel as well as batteries in series and parallel on a buss to balance the Panels to the inverters.

batteries hooked to buss wir

The present system uses panels hooked directly to the buss along with 12 – LiFePO4 batteries in 36 volt configuration to supply the Gridtie Micro inverters. The enphase inverters output nearly 2Kw to the grid for a good 6 hours.

At present the battery bank is only able to deal with the output of 28 of the panels. I will need to add 12 more batteries to use all the panels. At some point we hope to have a stand alone system that will only use the Grid for backup charging of the batteries

This post will be under construction as I build the generation system.