Want book recommendation on off grid design

Re: Want book recommendation on off grid design

I have posted information about books in the:

Working Thread for Solar Beginner Post/FAQ

among other stuff there...

If anyone else wants to add their favorite information to that thread, please feel free. Someday, perhaps the thread fairy will go through and make a nice FAQ out of it.

Odys99, I (we) did not intend to push you out there without any help.

There are many ideas and folks out there that can give you some good starting points. Energy usage is highly personal, so we try not to answer "how we would do something"--Because you may not find our solutions fitting your needs.

People have a very poor "feeling" of power usage and generation. A desktop computer/server running 24 hours per day may use 4-5x as much power as a 25 cuft full sized (North American) refrigerator/freezer. Making accurate measurements will be a big help in understanding your needs, and what you are will to pay for.

Just to give you some ideas on general energy usage:

• 1,000 WH per day (30 kWH per month): A small cabin with lights, laptop, radio, water pump to pressurize plumbing
• 3,300 WH per day (100 kWH per month): Add a full size 120 VAC Refrigerator/Freezer, "reasonable" well pump, washing machine--About the minimum for a "normal" electric power experience
• 10,000 WH per day (300 kWH per month): Add more people, a second freezer, TV+DVR, desktop computer, possibly even some heat pump heating/cooling/hot water
• 33,000 WH per day (1,000 kWH per month): A "typical" north American home
• 100,000 WH per day (3,000 kHW per month): Heavy A/C usage in a hot climate, swiming pool pump, electric water heater, etc...

For a weekend cabin, you probably would aim at 1,000 WH per day.

For an off grid home occupied 9+ months a year--Around 3,3000 kWH per day

For a full home with kids, and some creature comfort--10,000 WH per day.

A 3,300 WH per day system is not cheap--Probably around $10,000 to $20,000+ dollars worth of hardware+batteries+etc... Add a bit more if you pay somebody to install (systems larger than ~3.3 kWH per day, you should look closely if you have the knowledge and skill to install vs hiring somebody else--Especially if this is your first rodeo. And you need to replace the battery bank every 5-7 years or so, and electronics (charge controllers, inverters, etc.) every 10+ years (ongoing expenses).

Roughly, if you add up all the expenses (installation, maintenance, battery replacement for 20 years) and divide it by the amount of power you use over 20 years, you will get around $1-$2 per kWH, although a few folks here have gotten well under $1 per kWH for their estimated power costs.

When you compare to utility power at $0.10 to $0.20 or so per kWH, off grid power costs around 10x as much.

With power cost for off grid power so high--you can see your appliance selection is very important (electric coffee pot, perhaps not, A/C--Not on a small system, LED lights instead of filament, efficient $1,000-$2,000 well pump vs "cheap" jet pump, etc.).

I hope this helps. The numbers are very rough, and as I said, others may have different opinions/results (I, and the other moderators, are not in the solar business--We have nothing to sell)--But for a first look at your loads and potential budget--They are "good enough" to at least get you in the ball park before you really get down into the numbers for "your system" (looking up costs, selecting hardware, etc.).

Please ask questions and let us know how your plans are going. We are here to help and learn ourselves.

-Bill

Re: Want book recommendation on off grid design

A higher end MPPT type charge controller with ~140-150 VDC maximum input voltage can usually take an array with around 100 VDC Vmp-array maximum for most areas. Places that never get very cold may accept a higher voltage array.

And there are higher voltage controllers from Midnite with 250-~295 Varray-cold max voltage:

http://www.solar-electric.com/misoclchco.html

And there is a Schneider 600 VDC input MPPT controller (~400 volt Vmp-array).

http://www.solar-electric.com/xaxwmp80amp6.html

There are some other ways of doing this with SMA's Sunny Island system--But that is usually a bit "pricey" for a smaller system, especially outside of Europe (but it is very nice--Especially if you need a distributed AC power system for a small group of homes/work shops/etc.):

http://www.solar-electric.com/smasunnyisland.html

Lastly--There is building the power system at the array (panels, chargers, inverters, battery bank) and sending AC power from the array to the home (120/240/480 VAC etc.).

The drawback is the system is 500 feet away--A trek to check/maintain the system, figure out what you are going to do for AC backup genset, etc. But it can be done.

-Bill