On Fri,9/25/2015 8:33 AM, Wayne Burdick wrote:
Some of our friends are putting in large solar arrays that feed power back into the electrical grid. I'm looking for something smaller and simpler since our electricity use is very low overall.
Sticking with the original title of supplying only lighting, computers, and shack, I'll provide some general information that may help you think about designing a suitable system. My QTH is in a clearing surrounded by very tall redwoods, so an array of solar panels doesn't get a lot of illumination. As a result, I've made no effort to run 120V gear from it.
My system is pretty simple. It starts with four 55W panels retrieved from the dumpster at an agency where a neighbor ham maintained remote instrumentation sites. Because of the shadows cast by the trees, I have two strapped together and located to catch the sun before noon, the other two for the end of the day.
I use a Genasun MPPT charge controller between the panels and a pair of Trojan 6V 220 Ah lead-acid batteries. This system runs everything in my shack with the exception of the computers, the rotators, the SteppIR controllers, and my power amps. For lighting, I'm using the LED strips sold by a Pacificon vendor. Four strips taped to the ceiling provide illumination that's adequate for operating in the shack, and draw about 1.2A. The low power 120V stuff is connected to a small UPS. Because the draw VERY little current, a UPS can keep up for quite a while.
If I want to run power during a power failure, I can fire up the Honda 2000i.
The downside of this system is that the lead-acid batteries discharge curve starts around 12.5V and goes down below 11V for full capacity. That's fine for a KX3, but not great for a K3. The batteries cost me about $240, the Genesun about $120. The Genesun is available in several voltage and current ranges, and for both lead-acid and several Li chemistries. Buy direct from Genesun.
This system can yield 33Ah or more during the summer half of the year, but dips to MUCH less during the winter months. Also, if I want to contest with the K3s, I need a lot more power than I can get from this system, and I'd like higher voltage to keep the signal cleaner (those reading the mail may not know that the IMD in the K3 is lowest at high DC supply voltage).
So -- for contesting, and during the winter months, I must float charge the batteries from a small regulated supply. 10A is enough to keep up with a single K3 at 100W, but 20A is needed for heavy duty SO2R.
Because of their relatively low voltage discharge curve and the K3's need for higher voltage, I'm searching for battery chemistry with a discharge curve that stays above at least 12V, and higher would be better. There are some Li chemistries that are candidates, but cost is currently prohibitive.
If you have enough batteries and enough sun, you can start thinking about inverters to run your fridge and other 120V stuff when the power drops. Samlex has models for several power ratings, and two lines -- one that meets FCC Part 15 Class B, and another that does not. Appliances like refrigerators require a lot more current to start than to run. There are refrigerators specifically designed to run on DC for off-the-grid homes.
Samsung makes both computer monitors and TVs that run from a nominal 14V. I'm running their monitors from my 12V system, and they work fine. My cable modem and wi-fi router both run from 12V; they're not in the shack, so I run them from a sealed 12V lead-acid cell that is float charged by a linear wall wart that gives it a bit more than the gear draws. The result is a poor-man's UPS that holds internet up longer than Comcast does. :) Batteries for their fiber electronics repeaters are rated for 6 hours of operation, and it's common for power failures here in the Santa Cruz Mountains to last a LOT longer. And they want to sell me a package telephone service? No thanks.
73, Jim K9YC ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected]
