Advice for Off-Grid desert cabin

Re: Advice for Off-Grid desert cabin

To puncture your bubble a little bit... Solar RE energy is expensive!!!

So, your "electric appliances" used for heating, cooking, etc. are probably better off running from regular fuels (gas, propane, diesel, etc.) and/or or use various solar thermal collectors (hot water, solar hot air, solar ovens, etc.). Solar Thermal can be quite cost effective for "low grade" heating (hot water, heating, perhaps a solar oven on sunny days and long cooking items).

Just to give you an idea... Your utility power is ~$0.10-$0.20 per kWhr.

Your Solar RE system (parts, battery replacement, perhaps some professional installation) will run you $1.00 to $2.00 per kWhr--or 10x as much as your home power costs.

Typically, a "cost effective" system is for powering small, highly efficient loads. Not to say that you could not build a system large enough to power an electric stove--but it will cost you a huge amount of money to do so ($x0,000-$100,000).

In the end, there are two values for generating your own electricity that you need to look at... One is Peak Power (simply, how many watts you need to power at the same time) and, how many Watt*Hours do you need to power in a day. Believe it or not--typically the expensive part is Watt*Hour per day that will drive your system costs.

For example. Lets look at a microwave and a home desktop computer system.

The Microwave--lots of power--perhaps 1,500 Watts peak. But, you only run it a few minutes per day to heat food:

1,500 Watts * 20 minutes per day / 60 min per hour = 500 Watt*Hours

A desktop system--you are looking at ~250 Watts for tower+monitor+Laser Printer... And you use it 12 hours per day (work and audio/visual entertainment.

250 watts * 12 hours per day = 3,000 Watt*Hours per day

So, the computer system is 6x more power than the microwave...

A recommendation would be use a low-power Laptop at ~25 watts (turn the printer on only when you need it, etc.)--and all of a sudden, it is not 3,000 W*H but 1/10 that at 300 W*H per day.

In the end, people get away with living in a cabin full time on less than 1,000 Watt*Hours per day (30 kWhrs per month). And, I would recommend that for your monthly usage you aim at less than 100 kWhrs per month (100,000 Watt*Hours per month). Most homes in the US are around 600-1,000+ kWhrs per month--so that is some serious energy reduction for most people.

To start, review your current utility bills and start estimating energy use. For smaller devices a Kill-A-Watt meter (120 VAC 15 amps max) is a great tool for this job (less than $30.00)

Kill-A-Watt AC Power Monitor Meter
P4400 Cumulative Killowatt-Hour Monitor

Lets price a system that generates 100kWhrs per month (3kWhrs or 3,000 Watt*Hours) per day, for at least 9 months out of the year (use genset to make up winter production). And assume you are in the high desert of southern California. Using the PV Watts Website (use 1kW base solar panel wattage, 0.52 overall system efficiency, Daggot CA):

[FONT=Fixedsys]
Results

Month
Solar Radiation (kWh/m2/day)
AC Energy (kWh)
Energy Value ($0.125 per kWhr)

1      5.59          85        10.62   
2      6.03          80        10.00   
3      7.10          105        13.12   
4      7.74          109        13.62   
5      7.42          104        13.00   
6      7.42          98        12.25   
7      7.33          97        12.12   
8      7.40          99        12.38   
9      7.34          98        12.25   
10      6.76          97        12.12   
11      5.78          83        10.38   
12      5.20          80        10.00 
======================================= 
Year      6.76 ave sun hr    1135kWh $141.88 per year[/FONT]

Tossing the lowest three months of generation (80, 80, 83), the next is 85 kWhrs per month @ 1kW of solar panels. To convert to 100 kWhrs per month:

100kWhrs per month / 85 kWhrs per month per 1kW) = 1.2 kW (1,200 watts) of solar panels.

Very roughly, a 1.2 kW off-grid solar system will cost around $12,000 to $24,000 (self installed, shopping for best prices vs turnkey install).

We can go into the details to help you better price the system--but until you know your loads--that is sort a waste of time right now.

The above estimate of price is at least close enough for you to compare cost trade offs between appliance selection (propane stove, solar thermal hot water, etc.) and impact on your Solar RE Installation costs. (I am not an installer or connected with any solar retailer/vendors--just educated guesses from helping price systems here for others over the last couple years--some systems will cost less, some may cost more--just enough information to help guide your decision process).

Also, remember, that for an off grid system, you will need to replace the battery bank approximately every 5-10 years (more expensive batteries tend to last longer--and first time off-grid people very often kill their first battery bank in less than 3 years).

Questions?

-Bill

Re: Advice for Off-Grid desert cabin

Tony/Icarus is obviously on the "low side" of living with solar power--so, unlike me who is living On Grid with Grid Tied Solar--Tony and his wife has lived the low impact life style (but still has Internet--priorities! ).

You will find some points where there are credible either/or solutions (propane vs solar electric)... For example, the "Fridge"... You can get propane power, DC powered, or even just use an Energy Star Rated 120 VAC unit (and use the cost savings to buy a bit more AC Inverter, solar panels, and battery bank). And, you can even go with "home brew" and convert a chest freezer into a very low power fridge (1/4 the energy use of a similar Energy Star Fridge).

Research and ask--not everything made for "off grid" use is worth the money (off-grid refrigerators are one common appliance that is not always worth the $$$).

-Bill

Re: Advice for Off-Grid desert cabin

HairFarm,

By the way, looking at your pictures--it appears that the cabin and property may have had utility power at some time--and are those power poles in the background?

For the amount of power it sounds like you want to use (perhaps, only a first--live there, build out with modern low energy home)--utility power may be the cheaper solution (even if they charge you $x,000 of dollars to reconnect your power).

You can, later, always converter to full off-grid solar for emergency and/or change in lifestyle. Having utility power while you work on your conservation--is a very cheap and practical way to experiment with Off-Grid power consumptions with the backup of having "cheap" utility power. Plus, the property may be worth more if it has utility power available (if you ever decide to sell).

But, if you have grid, and it is reasonably reliable--then going with a Grid Tied solar system (no batteries) may be a better solution... If this is in the US (various rebates/tax credits, and your utility supports some sort of reasonable net metering)--you could get your GT power costs down to $0.10-$0.20 per kWhr...

In California--those cost levels are very competitive with the costs of utility power--and if you use more than "base tier" level power (all electric, A/C, well pump, irrigation)--it can actually cost much less than Utility power (which is in the $0.44-$0.60 per kWhr in some plans).

-Bill

Re: Advice for Off-Grid desert cabin

I would be very careful of "dorm style" fridge and assuming it is energy efficient... From what little I have seen, they may use 1/2 the power of a full sized fridge, but only store 1/5th the capacity. Many (all) that I have seen do not have an Energy Star approval.

If you want to do it your self--and don't need a freezer section--converting a chest freezer to a fridge (basically an thermostat--ectomy) works pretty well and uses 1/4 the power of a regular fridge (I think I said this earlier--getting old and lazy--a terrible combination :roll: ).

Otherwise, go "RV" and use a propane unit until you are there full time.

-Bill

Re: Advice for Off-Grid desert cabin

There was the "classic stolen house" from 2003:

The troubles of the world, however, caught up with him. Sometime in the past two months, somebody stole everything inside Miller's house -- and then stole the house.



Investigators and neighbors say it could have taken a day or more for thieves to deconstruct his 10-by-20-foot prefabricated home south of Placerville, yank a well pump from 625 feet below ground, rip off his 600- pound generator and haul away his 2,600-gallon water tank.
All that's left on the property are pads where the house and a tool shed once stood. Thieves made off with everything from Miller's wife's toothpaste to a rope sitting in the bed of a 1976 Ford pickup that doesn't run -- which Miller guesses is why they left the truck but stripped its four balding tires.

I don't think they ever found the perp... However, they did get donations to replace much of the physical objects.

-Bill