Solar Power

September 2021 – The Beginnings

I’ve always had an interest in solar power but never had dug much deeper. Way, way back in high school, I wrote a paper about alternative energy sources which ranged from wind, ocean tides, hyrdo, solar, and more. Of all of the ones I studied, I always felt like solar, either photovoltaic or thermal, would be the most viable.

Recently looking at some options for a “go box” or something that could be carried around for mobile AC and DC power, I stumbled back into the solar power concept. At first I picked up a small 30W mono panel, built a small 20ah go box that provides 12v ports, USB power, and a small 350W modified sine wave inverter. It worked and could be easily moved and used for small power needs and would rather quickly recharge with the 30W panel. I had found a cheap $2.99 simple charge controller and picked up a 10A and 30A version of those just because they were cheap. They are simple PWM based units, but work fine for my needs.

I had always assumed anything grid tied solution would be complicated and require some major interaction with the utility provider, so I never really considered it. However, during my research for the go box, I found grid tied inverters could be picked up rather cheap and one didn’t have to “go big” for a grid tie setup that could assist the grid for power needs.

Also while looking at the 30W panel, I noticed some 100W panels on sale for under $80. I also had enough amazon points that I had saved up for some special project or need, so I picked three panels and a 500W grid tie inverter to play around with. The hookup was simple, three 100W panels in parallel provides enough juice to the inverter to push around 250W back into the local system off loading a tiny bit (1% to 5%) of our daily power load.

Currently it is averaging only about 1-2kwh per day of generation, but that’s around .11 to .22 cents US per day of savings average overall. The only way this setup has any pay back is the use of amazon points for most of the primary purchase (and future expansion) which puts the payback currently at just over three years. Once I add a fourth panel for free in the future, that will drop down to around 2.8 years. Otherwise the payback would have been out around 7 years. As this is purely a hobby adventure, either wasn’t a concern, but it’s nice to know it will recover it’s cost sooner than later.

Off Grid Options

Although the grid tie generation was nice, I still wanted the ability to have some off grid capability. We do have a 8kw generator to cover power when we are out, but that is not usable longer term so having the ability to drive 500-1000W off grid would be nice. I did have the 30A PWM controller for $2.99 and some extra 12v (non deep cycle) SLA batteries on hand from other projects, so a currently I have 36AH of off grid that can be used if needed. This will drive a 1000W pure sine way inverter to power small items when the generator is not needed.

To keep the off grid battery bank topped off, I have a smart switch turn on a relay to redirects the 100W panels to the off grid charge controller for a short period each day to top off the SLA batteries. Since these are NOT used or depleted daily, they should last for some time until they are needed repeatedly.

Sun Tracking – 10/2021

Not able to leave good enough alone, I have always liked seeing things, such as my small robots, track a light and move towards it. With that in mind and a bit of research, it appears that some simple solar tracking can boost generation by about 20-30% as compared to static panel positioning. That, along with not wanting to have to manually adjust the tilt angle of the panels every month and already having a couple linear actuators, sparked the desire to build out a simple solar tracker provide two axis movement.