Foray into Solar

For the past week or so, I've been playing around with a solar system to get better educated about solar power.  Claudia (my wife) would say the operative word is "playing".

Reading specs and literature about solar systems, it's hard to get a feel for things.  There's a lot more to it than just hooking up solar panels, and voila!, you've got electricity.  It's necessary to get your hands on actual hardware (and live wires) to get a real sense of what goes on.

In upcoming posts, I'll ramble on about what I've discovered.  I use the word "discover" loosely.

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First an update on the dehumidifiers:

Finally I have valid data from the "good" unit in the "damp" location:

6.05 kWh over 25.09 hours, or pro-rated over 24 hours: 5.79 kWh.

The "bad" unit used over 11 kWh over about 24 hours in the same location.  Clearly there's something wrong with it. Today it gets replaced.

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Back to the solar experimentation.

My set-up is the standard Harbor Freight "45 watt" kit:

The kit includes three "15 watt" panels, a charge controller (the aluminum box), two 12 volt compact fluorescent light bulbs and assorted wires for connecting things up.

As solar systems go, this one is really tiny.  The systems you see on people's roofs are claimed to generate 4000 W or so.  Mine is only 1% of so of such systems.   It turns out it would have been a bad idea to have me do any sort of backyard lab experiments with anything much bigger, so a 1% system was a good thing.

What I quickly discovered is that the solar business is laden with deception.  You might think that with this kit I'd be able to set it up, and voila!, I've got 45 W of free power on sunny days.  But you'd be wrong.

No one mentions when you buy the kit that it's not complete -- you need at least one 12 volt battery to make the thing work.  Why?  (interpreted either as "Why don't they tell you?" or "Why do you need a battery?")

The answer to the first 'why' is because this keeps the price of the kit down.  Once you own the kit, you'll probably come back for a battery, all while still thinking that the kit was a great deal.

The answer to the second 'why' is that the voltage and current coming from the solar panels is all over the place.  Even with steady sunlight, I've watched (using one of any number of multi-meters, some of which no longer work) the voltage rapidly skitter over a range of  13 and 18 volts. To power most things, you need something with a pretty steady voltage and dependable current -- like a battery. Then it becomes clear what the scheme is -- the charge controller is an intermediary between the highly-unsteady solar panels and the highly-steady ... battery.  The battery that no one at the store mentions you will need.

So this was about the first thing I learned about solar systems.  It's not just panels.  It is panels and batteries or some energy reservoir that can hold the energy that the panels collect and feed the energy back out in a calm fashion.  In the popular roof-top systems that are connected to the grid, the energy reservoir is the grid itself.  For off-grid systems that can power a house, the reservoir usually consists of a disturbing number of batteries (that can produce a really disturbing amount of current; more on my adventures with current in a future post).  It would be good when you are buying a Harbor Freight kit that they tell you that you will also need a battery (it turns out there is no such thing as "a battery" either; more on that in yet another post).

It turns out I have one of these that has a 12 V battery inside, so I was able to complete my solar system without any further purchases:

Starting with this lack of mention of batteries, I got the nagging feeling that there is a lot the solar industry doesn't want you to know until you own the panels.  Tomorrow I'll go into what "45 watt kit" really means.