24 volt system help, newbie

[SunEagle]

Ok, thanks!
I was missing that .66 efficiency calculation.
So my "system" would be good for half my needs, or very close to my needs minus the distiller...thanks sunking!

I would also look at another source to cook your food. Using batteries to run even an induction cooker is costly.

[Anton]

With an average of 6 hours full sun and a desired production/usage of 8kwh/day what is the most economical/best 24 volt set up?

I wanted to stick with 24 volt because I can get new panels for 82 cents/watt and I think I'd be able to start it small (just run my .4kwh/day chest fridge) and increase its size to suit my long term needs of ~8kwh/day.

Thanks again!

[Anton]

I would also look at another source to cook your food. Using batteries to run even an induction cooker is costly.

Yeah, I had thought of that but one of my goals is to live for a year emitting nearly no CO2 into the atmosphere at all, farts excluded

I'll most likely abandon the distiller and make a solar still, that 3kwh/day could go to a little tv instead.

[SunEagle]

Yeah, I had thought of that but one of my goals is to live for a year emitting nearly no CO2 into the atmosphere at all, farts excluded

I'll most likely abandon the distiller and make a solar still, that 3kwh/day could go to a little tv instead.

I don't know what type of food you were planing on cooking but they do make solar ovens that use the heat of the sun to cook with.

They also make a small travel tv with an internal battery but it might be easier to stream tv shows on your computer using a satellite up-link.

[Anton]

I'll most likely build a solar oven into the south facing wall. I'll also build a distiller which will fit into the solar oven, there's a diagram in one of the Michael Reynolds books I have.
I'll still want the induction cooktop for some quick eggs in the morning etc. 2kwh/day on the cooktop would be over an hour at full use. That'll mostly never happen. My 8.5kwh/day is really a MAX usage.
Any thoughts on the set up?
Thanks!

[Anton]

With an MPPT cc it wouldn't matter what solar panels I purchased so I could use 27 volt panels to charge a 48 volt battery?
If so, would it be cheaper/same/more expensive to do a 48 volt system instead of a 24 volt? Where you're looking to produce 8.5kwh/day with 6 hours avg sun?
Thanks everyone

[SunEagle]

With an MPPT cc it wouldn't matter what solar panels I purchased so I could use 27 volt panels to charge a 48 volt battery?
If so, would it be cheaper/same/more expensive to do a 48 volt system instead of a 24 volt? Where you're looking to produce 8.5kwh/day with 6 hours avg sun?
Thanks everyone

It should be cheaper to build a 48volt system.

If you hooked up the panels in series you will increase the voltage (such as 2 - 27volt panels = 54volts) to the charger input. For that matter the higher voltage output panels end up to be less expensive per watt than the lower voltage panels.

Also most MPPT chargers have a much wider voltage input range than PWM type as well as multiple output voltage settings including 48volt.

By using the 48volt battery system you will:

1. reduce the amperage allowing you to use smaller wire size
2. give your batteries a better life by running them in series instead of parallel.

[FloridaSun]

Check out those Earthship homes he is talking about. Pretty cool architecture.

I've always wondered if those earthships made out of old tires smelled of old rubber.

[SunEagle]

I've always wondered if those earthships made out of old tires smelled of old rubber.

Only if you burn them to stay warm.

I still think they are pretty cool looking. I had entertained the though of building a dome type home on my retirement property back a few years when the hurricanes where beating us up. I actually found a number of places that sold everything from full cast concrete to engineered panels that assembled into a dome. The HUD ratings had is survivable up to Cat 4 storms as long it was above any type of storm surge.

[Sunking]

Yeah, I had thought of that but one of my goals is to live for a year emitting nearly no CO2 into the atmosphere at all, farts excluded

Extremely flawed assessment, and the truth will surprise you. If you go with a solar off-grid battery system you will be emitting more CO2 vs buying it from the POCO not to mention the electricity from a battery system will cost you around 10 times more than buying it for the rest of your life. So if you are under the impression you are going to save money or the earth forget it as it is not remotely possible.

[Sunking]

With an average of 6 hours full sun and a desired production/usage of 8kwh/day what is the most economical/best 24 volt set up?

You cannot use yearly average on a battery system. You have to use worse case otherwise you are dark all winter.

If you demand 8.4 Kwh/day, you have no choice to go with a 48 volt system period in your area. Higher voltage is less expensive than lower voltage.

Your system to meet 8.4 Kwh minimum requirement is:

• Panel Wattage = 2600 watts
• 48 volt Battery Capacity = 875 Amp Hours
• MPPT Charge Controller = 50 amps
• Maximum Inverter Wattage supported = 2600 watts or smaller
• Minimum Generator = 7 Kva
• Minimum 48 volt AC charger = 100 amps.

[FloridaSun]

Only if you burn them to stay warm.

I still think they are pretty cool looking. I had entertained the though of building a dome type home on my retirement property back a few years when the hurricanes where beating us up. I actually found a number of places that sold everything from full cast concrete to engineered panels that assembled into a dome. The HUD ratings had is survivable up to Cat 4 storms as long it was above any type of storm surge.

hahaha.... I never thought of that, burning, if they would be a hazard in/near a forest fire.
domes can be cool, specially if they can be sunk into the ground a bit. I built a truncated icosahedron (pentagon floor plan, triangle walls/roof) on the edge of a cliff one time back in 80s. Amazin how much room there was in there with only 140 sq ft of floorspace.

[SunEagle]

hahaha.... I never thought of that, burning, if they would be a hazard in/near a forest fire.
domes can be cool, specially if they can be sunk into the ground a bit. I built a truncated icosahedron (pentagon floor plan, triangle walls/roof) on the edge of a cliff one time back in 80s. Amazin how much room there was in there with only 140 sq ft of floorspace.

Yeah but it is hard finding ways to hang pictures on curved walls.

[FloridaSun]

Yeah but it is hard finding ways to hang pictures on curved walls.

divide and conquer the issue, build walls. Would be a hellofa rack to mount solar panels for a dome too... but then you'll have your RV shed roof for that.

[SunEagle]

divide and conquer the issue, build walls. Would be a hellofa rack to mount solar panels for a dome too... but then you'll have your RV shed roof for that.

Either the RV shed roof or a ground base system. I have more that a couple of acres available for that. Probably won't put in a tracking system since I get good S by SW exposure.

I think I can keep my electrical footprint down to only needing about a 5kw system to handle everything but have to work out the numbers and it is still a few years off.