Ones and Zeros

Everyone knows that rural temperatures are often lower than city temps.  Sometimes when the air temperature is near the dewpoint the effects of local heating caused by cities are noticeable in differences of condensation.  When that condensation is rain and is visible on radar then we get a radar image of a heat bubble.  That heat bubble is always there, it’s just not always visible.  It’s caused by things like cars and trucks, heat leaking from buildings, and sun on asphalt and concrete.

In the radar image below is from late last week the area without the rain in the middle is warmer by just enough to stop the formation of the rain.  Multiply the heat effect of Washington DC below by all the cities in the world, and you can get some massively large effects.

I’ve finished the installation of my solar power system in the popup camper. I think of it as a pilot to a possible house solar system that’s rather more-expensive.

I talked about this a little before, but in short we have a 30 Watt panel feeding a 65 AH battery with a charge controller. This is a larger battery that I think I need, but was a standard size that I could buy. Having more reserve won’t hurt. When I tested it, I propped up the panel as below. (Yes, it still generates power in the shade, but less.)

The battery, in turn feeds several 12 Volt DC uses: LED lighting strips and four 120mm computer fans for ventilation. These are almost silent (I bought them specially for that). Then there’s the 120VAC inverter for AC power. That makes a sound with its vent fans so we’ll only use it when we need AC. That’s for charging a computer, etc.

The first steps to doing a solar installation are to figure out the electrical load you want to supply, and thus the amount of power you’ll need. My load is 200 Watts/day. Pretty minimal. Your house uses much more than that. Read your power meter for your house’s load. Or, for a smaller system like mine, calculate your load. There are online tools for this at places like the www.altestore.com which also has many helpful articles too.

Once you have an idea of the load, then figure the power you’ll get from the panels. Mine is for use in the longer sunny days of summer, so I figured 5-6 hours of sun per day. For a house, you’d need a year-long average of hours of sun/day, and adjust that for shade from nearby trees, hills, etc. The amount of power helps determine the size and number of the panel.

You also will need to know how many days reserve power you’ll need. If you’re an off-grid system, this is more critical since you can’t pull power from the mains. If you’re connected to the grid, you actually don’t need much (or perhaps any) batteries. Your reserve requirements determine the size of your batteries.

Then, you need a charge controller. Overcharging or overusing your batteries can shorten their life drastically. Since they’re expensive, it makes sense to spend a little money on a device that controls that charge level. It has to be sized for the amperage and current your panels provide. Wire this together with wiring for the amperage you’ll be passing through the wires. Put some fuses in place (I have one leading to the battery, and one from the battery.)

Then, you need an inverter, this converts the DC power to 120VAC power. Some systems use 12 VDC like mine, but larger systems will use batteries in series at higher voltages.

My inverter is the small blue device here. This is my battery, the small gray thing is my charge controller. The large black cable and the device it attaches to is a parallel system for plugging the camper into campground-provided AC power that we’re not using. Since I took this photo, I’ve added the outputs from the battery in terminal strips that the LED lights, fans, and USB power converter’s plugged into.

Most of the work was in the wiring and in figuring out the connections. In any real project the minutia of fitting the parts into what’s already there is a big part of things. Most of the connections are soldered, a few are crimped as I trust crimping less.

A less minimal system would have amperage meters to show the charging current and load current.  Some more expensive controllers have a monitor to show power stored, etc.  But this is a vacation-purposed system though, if the power dies it isn’t a big deal.

More planning on my part would have simplified the installation as I would have just ordered all the parts and wiring I needed from DigiKey, Jameco, or Mouser Electronics. But I tried to buy local from Radio Shack. Radio Shack is no longer a parts store and hasn’t been for years; I hereby give up on them. Since I like to see the parts and handle them when planning I really miss a local parts store. If I still lived in Austin TX or Silicon Valley there would be no problem. (I love Fry’s Electronics!) But government is the local industry here and they don’t need local electronics parts stores, just conference rooms.
So, vacation is soon and we’ll test out the system in real life instead of the driveway. And perhaps I’ll get some solar-powered iPhone programming done!

Thomas Friedman is on the trailing edge of the obvious. In his new book “Hot, Flat, and Crowded” he finally figures out that the economy is driven by energy, not by politics. And, that we’re way behind on addressing our energy problems.

I’ll give him faint praise in that Friedman isn’t a pollyanna merrily denying any problems with our energy infrastructure. But I’ll take that back by saying that his thesis in this book is neither original nor very perceptive. While he highlights incidents and particular stories, his prescription is the same thing that others have been writing and saying for many years now.

Nice that he’s finally caught up.

He takes the Bush administration to task for essentially not defining a useful energy policy, yet doesn’t recognize his own culpability in his early support of that administration. He also thinks that McCain’s has “the right instincts” on energy policy despite McCain’s almost total agreement with the Bush administration.

I’m guessing it’ll take Freidman another five years to figure out that he was wrong on that one too.