Saturday, December 14, 2013

Not Just Solar Panels

I've been going on and on about how solar panels have some down in price and are such a good deal. Technology has come a long way. However, a stand alone solar electric system consists of more than just panels. There are some other components, and most of theme have also come a long way.

The electricity generated by the panels has to regulated so as not to damage the battery bank. For that there's a device called a charge controller. When first installed, my system had a simple Pulse width modulation (PWM) controller. It was dead simple and reliable, but not as efficient as the maximum power point tracker (MPPT) type. My system had a big jump in efficiency when I switched to the MPPT charge controller. In general, they are more expensive than the older type, but prices have come down. Over time, they more than pay for themselves.

That being said, the small solar electric system on my boat is still using a cheap PWM controller. They are dead simple, and cheap, and that's not a bad thing. Besides, it came as a kit with the panel I'm using. There has been no need to upgrade.

After the charge controller, we have the batteries. While there have been some improvements in batteries. For most people they aren't worth the high cost. My house is powered with flooded lead acid batteries, (golf cart batteries) a technology little changed in over 100 years. They work and stand up to abuse that kills more expensive batteries. Their big disadvantage is weight. Lightweight batteries make sense in cars and tools, but weight is not a big deal in a stationary installation. It's not like you are changing out batteries like a kid's toy at Christmas. I change mine about every 10 – 12 years.

Inverters have also been improved. That's the device that turns battery DC power into house 120 volt AC power. Mine is over 20 years old, a Trace 2524. It's old technology but has never given me any problems. Since it ain't broke, I'm not going to fix it. Newer inverters tend to be smaller, cheaper, and lighter.

The power output from my inverter is something called modified sine wave. What does that mean? Utility power is is pure sine wave. Every electric device made is designed to work with it. Inverters that produce pure sine wave power used to be outrageously expensive and inefficient. They've since improved and also come down in price, but are still expensive.

For most uses modified sine wave is good enough. People never notice the difference with the majority of devices. There might be some buzzing in some audio equipment. My microwave makes a humming noise, but it's harmless, if unsettling when first heard. Newer quality inverters lessen those effects. That being said, there are some pretty inexpensive, good enough, powerful inverters. When mine finally dies, I'm probably going to replace it with something cheap.

That's pretty much a solar electric system: panels generate power, a charge controller regulates it, batteries store power, and an inverter makes house current. Of course, it's prudent to have the proper fuse, disconnects and gauges in the system, for safety's sake.



  1. When you get the chance, why not shoot a few pictures of your set-up to us. It would be interesting to check out!

  2. Good idea! I'll do it when I get home in the spring.