off-grid DC-only system

[noglider]

I saw this Instructables article and thought, hmm, going part-way might make some sense.

I have a friend who knows a thing or two about this stuff and tells me that the setup described in the article uses really cheap equipment and is a pretty shoddy job. So first, does the goal make sense. And second, if it makes sense, how would you do it?

The idea is that I could save a small fraction of my power bill by generating some power with solar. I might generate a bit with a stationary bike, but I realize it won't amount to much.

And a DC system powering DC devices uses less power overall. And coincidentally, a lot of the DC appliances are the things I most want to stay running in a power outage.

I don't want to spend the kind of money required for a grid-tie system, and I don't want to keep my consumption level when the power goes out. When the power goes out, I'm willing to endure a certain amount of discomfort. How much? I haven't decided yet.

Thanks, folks.

Tom

[inetdog]

I saw this Instructables article and thought, hmm, going part-way might make some sense.

I have a friend who knows a thing or two about this stuff and tells me that the setup described in the article uses really cheap equipment and is a pretty shoddy job. So first, does the goal make sense. And second, if it makes sense, how would you do it?

The idea is that I could save a small fraction of my power bill by generating some power with solar. I might generate a bit with a stationary bike, but I realize it won't amount to much.

And a DC system powering DC devices uses less power overall. And coincidentally, a lot of the DC appliances are the things I most want to stay running in a power outage.

I don't want to spend the kind of money required for a grid-tie system, and I don't want to keep my consumption level when the power goes out. When the power goes out, I'm willing to endure a certain amount of discomfort. How much? I haven't decided yet.

Thanks, folks.

Tom

Well, for use as backup during power outages, a straight DC to DC system makes some sense. But you will still need batteries and a charge controller to make up for the fact that solar does not deliver a steady output and has a hard limit on the current it can produce at any moment.
But if you try to run some of your loads off DC full time, you will be saving on your power bill but paying 5 time or more as much for the solar power after you take equipment purchase and battery replacement into consideration, even if you do not end up buying and inverter.
The flexibility given by using 120 VAC appliances, etc. generally makes it worthwhile to go for an inverter.

A hybrid system that produces power mostly for resale back to the POCO makes more economic sense, and the you just keep the battery-only capability for use in power outages.

As for the article you mentioned, if you correctly take into consideration all of the costs (particularly battery replacement) the cost per Kwh is going to be far higher than the cost from POCO (unless your rates are on the order of $1 per Kwh) even if you use cheap equipment.

[Sunking]

The idea is that I could save a small fraction of my power bill by generating some power with solar.

Never going to happen Tom, it is impossible. The exact opposite is true. Electricity off grid from solar will cost you 10 to 20 more than you pay for it the rest of your life.