Self Sufficient on Solar? Something Not Right !

[RJsfishin]

I'm happy w/ my small 200 watt solar, but it dawned on me the other day that if the sun hangs in here as long as I do (here in QZS) I will have saved a whole $60 of gasoline I usually burn in my Honda 1000 in a couple months. Not a terrible return on a $300+ solar investment, I thought.
But when I found myself going after my 2nd tank of propane @ 50 bucks a trip, I realized something about this self sufficient solar ain't workin quite right.
Just curious, how many are running their electric heates on some of these chilly nites,.....meaning how many more watts of solar do I need ? 🙂

Or maybe a better question,...how many solarers are still buyin propane. Maybe we don't have this solar all figured out yet ??

[mena661]

smkettner wrote:
In a mild chill a heat pump would produce 2 to 3 times the heat btu per watt vs resistance heat.

Didn't know this and great information!

2oldman wrote:
Running heat off batteries is pretty much like running A/C. Ain't gonna happen.

Actually there are members here already running A/C off inverter (few hours here and there), they just don't talk much about it. It's not like it's an impossible task, it just takes some planning like everything else.

[doughere]

30 lbs propane is about 7 gal.
7 gal propane * 95000 BTU/lb * 65% EFFICIENT = 432250 btu
1 AH @ 12V = 12 watts * 3.5 BTU/watt = 42 BTU/AH
432250 BTU / 42 BTU/AH = 10291 AH

If a 30 lb tank lasts 2 weeks, that means you need to harvest 735 AH a day (3 weeks 490 AH a day). You're looking at 1500 to 2000 watts of solar.

This is based on resistance type heat; as SMKEENTR above mentioned, in mild weather a heat pump could provide significantly more heat per watt than resistance.

THINK BIG.

Doug

[BoonHauler]

2oldman wrote:
Running heat off batteries is pretty much like running A/C. Ain't gonna happen.

I second the motion.

[time2roll]

In a mild chill a heat pump would produce 2 to 3 times the heat btu per watt vs resistance heat.

[2oldman]

Running heat off batteries is pretty much like running A/C. Ain't gonna happen.

[BFL13]

Recharge time is all about the charging rate and having enough generator VA to run the charger(s) You can do a 50-90 in two hours with a 30% charging rate (any size battery bank), which is the max rate usually given for deep cycle Wets.

I can recharge my 700AH bank 50-90 in more like 2.5hrs with 140 amps (20% charging rate) going in but I can't recharge faster because the Honda 3000 can't handle more chargers of the kind I have.

You would need to calculate your AH usage for the heater or air conditioner, then know how much gen time you would have, then fit that AH usage with all other usages into your 40% of AH capacity (50-90) Then you know what the 100% capacity is and now you know how many amps charger you need to get a 30% charging rate to get it done in two hours or what rate you need for the allowed time if time is longer than two hours.
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[mena661]

pianotuna wrote:

The lowest draw I've observed in the last week is 1800 watts. It has been as high as 5000. I know my case is special--but there is no possible way I could have enough panels installed on the rv to support the heating needs.

With enough battery capacity and solar, you could even run that 5kW load BUT how/when do you recharge for that? That's the killer. Space is not really an issue either as you COULD tow a trailer with enough batts/solar OR buy a rig that allows enough batts/solar OR make something that allows enough batts/solar (like that stacked solar panel idea you had or that guy with the toy hauler that built a battery rack under his rig).

[pianotuna]

Hi BFL13,

Actually, if you can do logging roads there are over 100 places in BC to boondock. British Columbia

btw I picked up one of the inverters you mentioned from Canuck Tire. Do you know if I can run it (at low wattage) from a cigarette lighter outlet?

BFL13 wrote:
We don't have areas around here you can just go off by yourself in and RV like they do in the States. (Drat!)

[BFL13]

Good point. You can only really recharge the batts during daytime either with solar or with gen where gen at night is a no-no.

If you only need heat at night, then you have all day to recharge that usage. Air conditioning is a variable whether you need it all day and all night or which. If it cools off at night so you only use a/c during the day, then you can't use the cooler night to recharge the batts. If it is hot at night but you are away from the rig during the day, then you get a chance to recharge with solar while you are away during the day.

[pianotuna]

Hi mena,

The lowest draw I've observed in the last week is 1800 watts. It has been as high as 5000. I know my case is special--but there is no possible way I could have enough panels installed on the rv to support the heating needs.

I can do one night when the temperature is 0 C (32 F) on battery power, if I restrict heating to the bedroom, but it takes days to recover from that on solar alone.

I think I can have a "shot" at running the air conditioner if I add 800 more watts, but 1600 would be better.

[mena661]

We set the thermostat to the low 50's at night and use an electric blanket to warm up the bed but, with enough solar, you could let it run all night. But we're weekenders and I have no numbers to say if that would save propane or not over your usage. You might be doing something similar already. IMO, this is similar to running the A/C on inverter, in order to get an electric heater big enough to replace your propane furnace, you're looking at A/C level power draws. We've had some good discussions on this and the consensus is that the problem is not battery capacity or amount of solar, it's being able to recharge the batteries for the next days usage. IMO, since the heater only runs a few times at night it's probably easier to run a big electric heater on inverter than an A/C unit.

[BFL13]

The campground we like in summer has a section for hook-ups in the usual side by side configuration plus it has an area you can just park with no electric hookup The difference in price is $10/day between the two places. (Allowed gen hours in the un-serviced area 10am-2pm so you can't make breakfast with the gen like a lot of people on here recommend. You need the inverter for supper too)

The difference in experience is that in the un-serviced area you are not packed in like sardines. Lots of people don't mind that and prefer having hook-ups. Others prefer being off by themselves more and they need to set-up their rigs for that. It's not about the money

Same in a provincial park, you get lots of space between rigs and the price (here anyway) is about $10/day less than at a campground with hook-ups. The provincial parks here are in the woods so you can't use solar, but then you don't stay that long at a time anyway so you can get by with gen /charging in their limited gen hours (9-11am and 6-8pm)

We don't have areas around here you can just go off by yourself in and RV like they do in the States. (Drat!)

[NinerBikes]

Add insulation... to you, and the wife, in the form of blankets, covers, layered clothing, etc, or add insulation to the motor home to minimize heat losses. That is the most cost effective way to add heat... by retaining it. You only need a thin layer of warm air surrounding all body parts. By heating the least amount of air around the body parts, you maintain the highest levels of efficiency. Bundle up, and your wallet will stay warm with the extra paper insulation inside of it.

As a kid, some super cheap parents of friends of mine used to dump us down at the mall all day on hot summer days. That was a way of saving their electrical bill from the ravages of keeping the AC blasting and sucking megawatts monthly. Alternatively, go hang out at McDonalds, drink Sr. Citizen priced coffee, charge up and suck wifi on their dime during the coldest portions of the day, from 4 am to 9 am down in the "Q". You can learn a lot by observing all the Rasta bums with corn rows or dread locks on how to get by on less, they know all the tricks. However, being a Gypsy, and stealing, is where I draw the line.

[MrWizard]

RJ...My Onan is propane, I think yours IS to
Don't use the generator to run electric heater, it's really wasteful
Use the on board furnace, or add another heater
We recently replaced a Olympic 6000btu with a 8000but
We have 505 watts of solar panels on the roof, mainly because we have a residential fridge
We run the Onan for 2 hrs in the morning, because of the 100 amp WfCo and the large battery bank almost 1000 amp hrs, after that we can run the small generator on cloudy days like today
Or let the solar take care of things
Yesterday sunny and cold wind, solar produced 1110.0 watt hrs, 83.## amp hrs
Our total daily consumption is 1600~1800 watt hrs of battery use, fridge television pc lighting
MW and coffee maker not included, it is almost always on the Onan, very seldom on inverter, it can be done, I just don't like doing it , extra strain extra recharge

[pianotuna]

Hi,

How much for a full service campground? My solar cost about $5.50 per watt plus installation. It has paid for itself time and time again.

JiminDenver wrote:
Solar for us frees us from the daily grind of listening to the generator. I know it would take us years to recoup even the small amount we have into the systems but you can't put a price on silence.