Solar Power in the Desert part II

I visited my friend again in Arizona for 5 days to continue work on his solar array last week (from 7/31 to 8/4). He had made some progress since my last visit HERE but it was tough going on his own. Working mostly at night due to the high (100+ degree F) daytime temperatures, we completed the welding of the full array frame and then mounted and connected all 40 panels to the system. Below is a picture of the completed 65 foot long array.

The array is aligned due south, however you may have noticed that near by tree. We have observed that the tree reduces the output of the first quarter of the array by over 10% in the morning (1-3 hours max from sun up). Since the array is over sized it is probably not a big deal. When the instrumentation has collected a full season of data it can be re-evaluated.

During our stay we had a powerful rain storm blow through with high winds which confirmed the design of the heavy steel frame. The storm did display some lightning but no nearby strikes were observed. Full lightning protection is not installed yet but we did get the first ground rod installed before we left. Lightning rods or air terminals are planned for a tall security light pole and some of the buildings and possibly the array as well.

To give some scale as to the size of the array, here is a picture of my friend and I with a truck in front of the array.

The configuration has changed a bit since last time since obtaining a single 12kw split phase inverter instead of the two 6kw units. This single inverter is a 48 volt only unit, so the 8 batteries are now configured as two series banks of four in parallel. The 48 volt configuration is preferred since the charge controllers can be better utilized up to their maximum 40 amps at 48 volts verses 24 volts in the previous configuration. This 12kw AIMS Power Inverter has not functioned as expected and fails intermittently on various load changes. A replacement has been on  order for months but has yet to arrive which brings into question the stability of both the unit and the company. Since there is a need for three phase power on the ranch, a split phase to three phase mechanical converter was obtained, however it is one of the loads that the 12kw inverter fails on currently. Recent research has now found that Outback Power has an inverter model VFX3648 that is capable of being setup to generate three phase power directly with three units combined. This would be a better solution and eliminate the mechanical phase converter. There is additional cost in this solution but taking in to consideration the issues (and wasted time) with the AIMS unit and the losses from a mechanical phase converter this may be the way to go in the future.

There is still a lot of work to do in terms of electrical on this ranch. There is the 25kw 3-phase diesel generator that is currently being used for water pumping due to the well pump being a 3-phase water pump (since the solar can't run it yet!) and now a second diesel generator has been revived for use now too. This second gen-set is a 10 kw 3-phase unit, which may save fuel while just running the water pump. In any event these electrical sources will need to be wired into a set of panels so the power can be routed where needed in the event of a failure of any of these sources. Also a small wind turbine is also planned for solar backup.