Solar PV Panel on the move

Rather than make the sensible choice and plug my solar differential controller and pump into the "mains" AC power, I chose to use a solar PV (photovoltaic) panel to supply this electricity.  This choice continues to cause issues.

The latest issue is that sometimes I find that the Taco zone valves fail to open and the solar hot water system overheats because the pump cannot pump the fluid past a closed valve.  The problem with the Taco zone valve is not clear.  I have tried to duplicate the problem by turning on and off a power supply connected to a spare zone valve.  The valve seems to work flawlessly.

On the actual solar hot water system, however, on a few occasions, I have seen the valve fail to open.  The problem is that the power available to open the valve is inadequate in the morning.  This causes continuous cycling and resetting of the solar controller and the valve.  When the solar fluid gets hot enough, the solar controller attempts to turn on the valve and the pump.  This causes too much load on the batteries and PV panel and the 24 VDC power drops below the cutout voltage of the controller (about 22 volts) and the controller shuts off and the valve closes.  With this load removed, the battery voltage quickly recovers to 24 VDC and the system turns on, only to repeat the same reset cycle.

The problem seems to be largely caused by my chosen location for the solar PV panel which is on the right of the Heliodyne solar hot water panels.  In this location, the solar PV panel is getting shade in the morning even when the hot water panels are in the sun.  The result is that there is inadequate electrical current to turn the system on when needed in the morning.  Usually this just means that the system continues to cycle and reset for 10 or 15 minutes until adequate PV power is available.  This would be no big deal.  However, the weakness in the zone valve means that under some combination of reset cycling, the valve ends up closed for the whole day.  That is bad.

To work around this problem, I have decided to relocate the PV panel to a location with less shading.  Specifically, I decided to put the panel at the top center of the hot water panels.  The picture below shows the old PV panel location.

And the next picture shows the new location.

Initially, I had rejected that location for the PV panel because I didn't want it to block the view from the window.  However, I think it looks fine at that location and the symmetry looks nice.

To hold the panel in place, I used about $100 worth of aluminum extrusions and other part from Misumi.  The aluminum extrusions are HFS8-4040 from Misumi which is 40x40 millimeters or about 1.5 inch square.  These are coupled into the Misumi frame that I used to hold up the solar hot water panels.  All the fasteners are stainless steel so the frame and fasteners should not rust.

As typical, I laid this all out in Pro/Engineer before hand to make sure everything would fit.

The first sunny day showed that this location works much better and the controller was able to turn on the valve and pump with no problem early in the morning.  Ultimately, the choice of solar PV based electricity over mains power may ultimately prove to be the right one.