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General => General Forum => Topic started by: tjm73 on October 22, 2007, 01:25:24 PM

Title: Off-Grid Power Systems
Post by: tjm73 on October 22, 2007, 01:25:24 PM
Don't know if this is an O/T thing or not, but I can't seem to find a very clear tutorial on how an off grid system is put together. It's almost like the people that do know don't want to tell about it.

I've tried some research but everything I find seems incomplete.  

Knowing their are some pretty resourceful and knowledgeable folks in the part of the web, can someone share a good primer of solid example of an off grid system?
Title: Re: Off-Grid Power Systems
Post by: glenn kangiser on October 22, 2007, 02:37:09 PM
There are a million ways to do it.   :)

Depends on what you have and what you want and what your budget is.

Basics

1. A Battery or bank of batteries.

2.  A light or other desired loads -appliances etc.

3.  A way to charge the battery or batteries.

Tell us what you want to power and your budget and we will see what ideas we can come up with.  The fancier it is - the more it costs.  No secret - it is something that can grow so there are few that are the same.  What is pretty well fixed is the equipment you have to work with and the cost of the materials is pretty stable.
Title: Re: Off-Grid Power Systems
Post by: Redoverfarm on October 22, 2007, 02:50:08 PM
Not trying to sidetrack your train of thought but some of the ideas had been discussed in my post " Alternative Energy" . You might pick up something there.
Title: Re: Off-Grid Power Systems
Post by: glenn kangiser on October 22, 2007, 02:55:49 PM
There is a lot of info here already for sure, -- seems tjm73 may want to get into - hook wire "A" to terminal "a", which we can do also if need be.

Here is a link to that topic.  Thanks, Redoverfarm. :)

http://www.countryplans.com/cgi-bin/yabb2/YaBB.pl?num=1192660727
Title: Re: Off-Grid Power Systems
Post by: ak_meli on October 22, 2007, 03:10:56 PM
I am planning an off grid power system too. (very early stages though)

I have a very good local place that has a wealth of knowledge. This diagram is really helpful.
http://www.absak.com/diagram/general/index.html

The specifics of your offgrid system will depend on a couple of factors:

Watts or Amp. used / day =
number of days =
time of year=?
can you see the sun ?
number of cloud cover days =
average wind speed @ 50 feet=
$$$$ to spend=
Will you have a generator?


For me, solar panels won't work for the majority of the year. Some other alternatives that people employ up here is generator and batteries. A few deep cycle fork lift batteries go a long way and are easily charged by generator. The place above, Absak.com sells a quick charge wall unit to place next to the generator from for charging multiple batteries all at once. Spendy charger but well worth it. Costs about $350 for it. Running the generator for an hour or so would charge them enough for a full day and night.

Home Power Magazine may also be a helpful resource.

The Backwoods Solar Electric System of 1395 Rolling Thunder Ridge, Sandpoint, Id. 83864. These folks will do as much or as little to get you electrified in the best-suited type of system for your needs. They will give advice in the planning stage or build the most eleborate power system for you. They are a big help in just getting up to speed an all the various methods for living on and off the grid. AND, they are living and working their own advice: so, www.backwoodssolar.com

As well, The Lehmans Company [non-electric catalog](www.Lehmans.com)and the Cumberland General Store(www.cumberlandgeneral.com.)

Explore the backwoodssolar.com homepage. It has a wealth of information. Here are some things that might help you get started.

Be sure to check out the backwoodssolar.com Newsletters. Here is the summer 2007 one. There is a Fall 07 one out. They are extremely helpful. Also have stories from users.
http://www.backwoodssolar.com/newsletter/pdf/SUMMER%202007%20NEWSLETTER.pdf

They also have a great page on figuring out how much you need, giving some examples.
http://www.backwoodssolar.com/reference/examples.htm

Here is a page on wiring:
http://www.backwoodssolar.com/reference/home_wiring.htm

Some resources to buy:
http://www.backwoodssolar.com/catalog/books_videos.htm

Also, be sure to check out Coyote Cottage, although their system is for the minimalist

Forgot the link....
http://www.coyotecottage.com/powerplant/system.htm
Title: Re: Off-Grid Power Systems
Post by: MountainDon on October 22, 2007, 03:15:50 PM
tjm73, can you help and narrow the question down a little...

Do you mean like Glenn suggested, the how to connect one thing to another safely, or how to select components, or what components make a system, or??

Title: Re: Off-Grid Power Systems
Post by: MountainDon on October 22, 2007, 03:23:27 PM
The diagram at absak is good, but depending on what inverter you choose the auxillqary battery charger may not be needed. And the system meter, is interesting for technofiles, but not necessary. They're only as good as they are calibrated and that changes over time as the batteries age. It's probably the last thing I'll ever buy. My opinion.

And you will need a generator in nearly every installation.
Title: Re: Off-Grid Power Systems
Post by: glenn kangiser on October 22, 2007, 07:58:24 PM
Welcome to the forum, ak_meli.  

Lots of good info there.  I like the diagram - even if not all options are used.  It is a good overview of what you could do.  

The guy around here sold a lady a system at near double the price with no generator.  35K for a 20K or less dollar system.  It failed the first night they went to use it -- dead batteries and no way to charge them.  He probably got another 10K out of her for a generator.

I guess he figured she was old and wouldn't need it for much longer anyway.  I don't do business that way. :(
Title: Re: Off-Grid Power Systems
Post by: tjm73 on October 23, 2007, 02:48:13 PM
Quote
tjm73, can you help and narrow the question down a little...

Do you mean like Glenn suggested, the how to connect one thing to another safely, or how to select components, or what components make a system, or??


Let me try to get kinda specific......

What components are needed? I know you need batteries, an invertor (of which there are several kinds) and I know that the type f inverter is importent if you run sensitive electronics.
How do you size your battery bank?
How do you wire that battery bank? In series? In parallel?


Let's take a hypothetical situation/example....

Let's say we need monthly service of 3.6 kW/h. My little apartment with all the lights on, the TV on, the VCR on, the DVD on, the computer on, refridgerator, microwave, etc... averaged 3.6kW/h on the bill each month over a year time frame.

I know how to make the power, but not how to safely and efficently collect and store it. We are studying the basics of DC and soon AC electricity in a class at college.



I will look through the provided links as well.
Title: Re: Off-Grid Power Systems
Post by: MountainDon on October 23, 2007, 04:07:23 PM
3.6 Kwh for a monthly average? That seems to be incredibly low.  :-/  :-?

I use far more than that per day in a 1550 sq ft single floor house, and I'm under the national average.

This calculator gives you a good idea of number of panels and batteries you'll need.

http://store.altenergystore.com/calculators/off_grid_calculator/#

If 3.6 Kwh was the true monthly average a single 85 watt PV panel with 2 - 6volt batteries in series would work. I use more than that in my RV.

 :-/
Title: Re: Off-Grid Power Systems
Post by: tjm73 on October 23, 2007, 04:14:00 PM
hmmmmmm.....................it may have been 360 kWh. I was going back and forth on which it was.
Title: Re: Off-Grid Power Systems
Post by: MountainDon on October 23, 2007, 04:35:24 PM
That sounds more realistic, but that's a lot of electricity. That calculator comes up with 15 x 175 watt panels and a minimum of 8 x 6 volt 420 amp/hr batteries for even sunny NM.  15 x 175 watt panels alone will cost about $11,000.00. Batteries at about $2700. Add freight to all.

Rather than use those actual usage figures you should really do an accurate audit of what you really need to use. A normal refrigerator is a big energy hog, that's why some of us have been talking over what's the best propane gas fridge. There are very efficient electric fridges; google sunfrost.

Cooking with an electric range is a no-no. Ditch that for propane.

Calculate the lights using CF lamps, if you don't already use them.

This calculator will let you easily total up your daily use.
http://www.affordable-solar.com/index.php?file=c-off_grid
It will not help with panels or batteries... that other one will.
Title: Re: Off-Grid Power Systems
Post by: MountainDon on October 23, 2007, 04:57:25 PM
But back to part of your question... your stated main crux... "how to safely and efficiently collect and store"

Collection:
Have the PV panels as close to the batteries as possible. (shorter and smaller cables)
Use a MPPT type of charge controller.

Storage:
Lead-Acid batteries are what's used. Use nothing less than a 6 VDC golf cart style battery. RV/Marine so called deep-cycle"batteries are not much better than the common automotive starting battery, IMO. The "L-16" type are better with heavier plate construction. Also heavier to handle, a disadvantage. Golf Cart batteries can give an excellent cost to service life ratio is maintained.

There are advantages to using a system wired for 24 VDC rather than 12 VDC, though many have used 12 VDC.

The main advantage to 24 VDC is smaller size cables. Also 24 VDC systems have more batteries in series strings. Better for the batteries in the long run, IMO.

The main advantage of 12 VDC systems is the vast number of 12 VDC "things" available. Lots of stuff from the RV market.

At the PV panels where all their wires come together you need a disconnect for maintenance safety. Also fuses or breakers. If the distance between panels and batteries is great then another disconnect from the panels and before the charge controller is advised.

A big fuse or breaker, able to handle the max current of the inverter is required right after the batteries. The inverter should be close to the batteries to avoid long cable losses. Inverter should not be mounted above or adjacent to the batteries. On the other side of a wall is good. Most inverters don't like really cold temperatures any more than batteries do.

A pure sine wave inverter is best if you will have electronics, or motors running off it. Some battery chargers self destruct on square [so called modified] wave inverters. And some electronics work fine off some square wave inverters. Depends.

The compinents you choose, switches, cable types, etc. etc. depend a lot on whether or not you must meet the NEC. You can't go wrong with NEC / UL approved components, but some things get pricey. And some things can be safely exchanged for non code devices. Some. Not all. Not what I necessarily recommend anyone do.
Title: Re: Off-Grid Power Systems
Post by: glenn kangiser on October 23, 2007, 05:35:02 PM
I am currently producing and using around 12 kwh per day - for 360 per month -- might even be more but I doubt it's much less.  I don't get into the numbers as much as Don. :)

If they get short on power  I add more panels or I could go and build racks and add an MPPT controller - tilt up for better angle -- build simple racks and do every few week seasonal tracking  adjusting vertical angle for lower or higher sun as the case may be.
Title: Re: Off-Grid Power Systems
Post by: tjm73 on October 23, 2007, 05:43:30 PM
That helps, but I'm still not understanding how to select the batteries.

Let's say we have a small cabin. In it their are the following electrical devices. (some wattages are guesses)

8 CF lights, each 23W, 300mins/day
1 32" TV, 500W, 120 mins/day
1 VCR, 25W, 120 mins/day
1 DVD Player, 30W, 120 mins/day
1 PC, 80W, 180 mins/day
1 Monitor, 180W, 180 mins/day
1 Microwave Oven, 1100W maximum, 10 mins/day
1 Toaster, 700W, 3 mins/day
1 Stereo, 400W, 300 mins/day
1 Refridgerator, 1800W, 1440 mins/day

My calculations show that's 48.2 kW/h, 120V service
Title: Re: Off-Grid Power Systems
Post by: MountainDon on October 23, 2007, 05:48:41 PM
Also.....where is the point of use geographically?
Title: Re: Off-Grid Power Systems
Post by: tjm73 on October 23, 2007, 05:53:43 PM
Quote
Also.....where is the point of use geographically?

Rochester, NY is the closest city to me.

About batteries....

Say you have 2-6V batteries that are 500amps/hr each. In series they add up to 12 volts, still at 500A/h. In parallel they woudl be 6V @ 1000 A/h. Is that correct am I understanding correctly?
Title: Re: Off-Grid Power Systems
Post by: MountainDon on October 23, 2007, 06:05:48 PM
Using the calculator at http://www.affordable-solar.com/index.php?file=c-off_grid
Leaving the fridge out of it, that's 5000 watts a day, or 150 Kwh a month.

Using the other calculator at http://store.altenergystore.com/calculators/off_grid_calculator/#
I see your profile states upstate NY. Is Schenecftady considered upstate? That's what I selected. That gives a need for 15 x 175 watt PV panels.

I chose a 24 VDC system. Skipped the charge controller for now.

Battery section of the calculator; selecting 3 days of backup power to allow for clouds. Selected 55 degrees F as the lowest temp for the batteries (inside storage, cool unheated room... battery capacity falls as temp falls).  That gives a minimum of 12 x 6 VDC L-16 type batteries at 350 amp/hours per battery. That would be  3 series strings with 4 batteries per series string. Each series string parallel connected to the others. Calculations assume running the batteries down to 50%. You should try to never draw down more than that;better would be to only draw 25%.

Does that help? And remeber that's without the energy sucking fridge.

All the above may vary depending upon location and the winter hours of usable solar sunshine
Title: Re: Off-Grid Power Systems
Post by: tjm73 on October 23, 2007, 06:10:40 PM
Yeah that helps. Schenectidy is Upstate NY. Not near me, but close enough for the example.

I think I'm kinda gettin my head wrapped around the batteires thing. I'll keep readign and thinking about it.
Title: Re: Off-Grid Power Systems
Post by: MountainDon on October 23, 2007, 06:14:15 PM
Quote
Rochester, NY is the closest city to me.
Oh crap! That means less sun than the above example... more panels needed... like about 24 of them and 16 batteries.

Quote
Say you have 2-6V batteries that are 500amps/hr each. In series they add up to 12 volts, still at 500A/h. In parallel they woudl be 6V @ 1000 A/h. Is that correct am I understanding correctly?
Absolutely right! And because the parallel connection doubles the amps the cable size goes way up. That's why I say 24 VDC system is better. With lots of batteries some people would consider 48 VDC systems.

Say 16 batteries, two sets of 8 x 6 volt in series, connected in parallel.

Cutting down on the power use will cut the solar equipment needed. LCD TV's are king. Laptop computer is better than desktop.
Title: Re: Off-Grid Power Systems
Post by: glenn kangiser on October 23, 2007, 06:19:15 PM
Sounds good, Don.  I am running 12 L-16 @375 ah each.

The fridge must be off or needs to be replaced.  My 1934 GE Monitor Top fridge and 20 cu ft freezer each pull only around 1 kwh per day.  Freezer is modern energy star - GE is an antique with better efficiency than new ones.  It runs for about 8 minutes per hour at under 200 watts as I recall.  
Title: Re: Off-Grid Power Systems
Post by: tjm73 on October 23, 2007, 06:24:39 PM
Quote
Quote
Rochester, NY is the closest city to me.
Oh crap! That means less sun than the above example... more panels needed... like about 24 of them and 16 batteries.

Yup. We don't get poop for sunlight lots of the time.

We get about a 10 mph average wind when the sun isn't shining though. SO a soalr/wind combo with generator backup could maybe work.
Title: Re: Off-Grid Power Systems
Post by: MountainDon on October 23, 2007, 06:28:29 PM
The fridge is a killer, but the compressor doesn't run 1440 min (24 hrs) a day.Find the model # of your fridge or pick a fridge that seems similar.

Go to http://www.energystar.gov/index.cfm?fuseaction=refrig.display_products_html  and find that model and see what the EPA says the average Kwh use is. It's listed per year.

For example, a new efficient Kenmore is rated at 480 Kwh/year, 40 Kwh a month.
That calculates to 7 x 175 PV panels and 6 of the 6 VDC 350 amp batteries just to serve the refrigerator!!  :o  
Title: Re: Off-Grid Power Systems
Post by: MountainDon on October 23, 2007, 06:32:05 PM
Quote
We get about a 10 mph average wind when the sun isn't shining though. SO a soalr/wind combo with generator backup could maybe work.
Glenn's the windy guy around here.  ;D  But 10 mph doesn't sound like much to me. The wind up above trees and houses tends to be stronger, but you'd have to check wind charts/tables and/or talk to a reliable alt power company with local wind experience.
Title: Re: Off-Grid Power Systems
Post by: glenn kangiser on October 23, 2007, 06:36:14 PM
Wind tends to be about 3 times higher at 100 feet up, where your wind generator should be.

Note that charts don't take micro-climates into consideration, and while maybe not as efficient as if you were in a super great area, a good wind generator such as a Bergey can do quite well.  You can also build your own.  Watch some of the small commercial ones though.  Many are just crap.
Title: Re: Off-Grid Power Systems
Post by: Madroaster on October 27, 2007, 11:16:38 PM
Quote
The fridge is a killer, but the compressor doesn't run 1440 min (24 hrs) a day.Find the model # of your fridge or pick a fridge that seems similar.

Go to http://www.energystar.gov/index.cfm?fuseaction=refrig.display_products_html  and find that model and see what the EPA says the average Kwh use is. It's listed per year.

For example, a new efficient Kenmore is rated at 480 Kwh/year, 40 Kwh a month.
That calculates to 7 x 175 PV panels and 6 of the 6 VDC 350 amp batteries just to serve the refrigerator!!  :o
 

Wait--I'm confused.  If an appliance is rated at X kWh/year, then it can be divided by 365 for an average daily requirement.  Correct?

A Sun Frost RF16, rated at 0.48kWh/day * 365 = 175kWh/year.  Correct?

A Brand X model, rated at 335kWh/year / 365 = 0.91kWh/day.  Correct?

The way I read it, basing my entire electrical needs on a Sun Frost DC model-based system will require 86kWh/month, while basing it on a Brand X model-based system will require 112kWh/month.  

Unless I'm wrong, either Sun Frosts are prohibitively consumptive, or I misread what you said, or you have some error I don't quite understand.  But my thinking is more in line with what you wrote in this thread:

Quote
FYI, IF a person was to consider an electric, compressor driven refrigerator however, I am not convinced that the large additional cash outlay for the Sunfrost (type) is counterbalanced by the lower energy use. I ran the numbers many months ago. A less expensive, but highly rated (but not as frugal on power as the Sunfrost) refrigerator saves a bundle on the purchase. I calculated that spending a part of the difference on another good PV panel would provide the needed power difference.  :-/ :-/ :-/ :-/

Can you clarify this for me, please?

As a side note, if anyone's interested--taking the data from that website quoted above and playing with it in Excel for a while yields some pretty interesting results when you sort by different variables.  Specifically interesting is creating a ratio of annual energy use to volume (especially when you previously sort for configuration (chest freezer, fridge only, manual defrost, etc.)).  It really helps you narrow down appliance choices.  Neat stuff that we couldn't have done even 15 years ago.

Cheers,
--Derek
Title: Re: Off-Grid Power Systems
Post by: glenn kangiser on October 28, 2007, 03:16:49 AM
Derek, my numbers are  175/12 =14.6 KWH per month or less than 1/2 kwh per day.

The brand x would come in at 27.9 kwh pwr month or under 1 kwh per day

This pretty well agrees with my fridge and new freezer.  The freezer comes in at less usage than advertised per the Kill-a-watt meter.  It is the most efficient Sears freezer we could find and there is a great range of difference in their range of models, some using twice as much power for the same size.  Chest freezers without a defrost cycle are most efficient.

Chest refrigerators or a chest freezer converted to a refrigerator are very efficient also but you don't see them often.  The chest keeps the cold air from falling out every time you open the door.

Title: Re: Off-Grid Power Systems
Post by: John_C on October 28, 2007, 05:06:38 AM
Quote
chest freezer converted to a refrigerator

How would you do that?
Title: Re: Off-Grid Power Systems
Post by: peter nap on October 28, 2007, 05:20:44 AM
Glen and Don.....this is straying a little further OT, but since I've been looking at usage meters, what's your opinion (Cost aside) of:

New Kill-a-Watt EZ

and the

Watts Up Pro

The Watts Up seems to have a few features that will give more detailed information over time as well as a USB port.

Any others you can think of?
Title: Re: Off-Grid Power Systems
Post by: glenn kangiser on October 28, 2007, 05:26:16 AM
I read abut it somewhere.  I'm pretty sure all you would have to do is modify the thermostat or if the range on it is wide enough you may only have to set it warmer.

Here it is -- [highlight]Uses 100 watts per day[/highlight].

http://mtbest.net/chest_fridge.pdf

http://mtbest.net/part-list.pdf
Title: Re: Off-Grid Power Systems
Post by: peter nap on October 28, 2007, 05:30:38 AM
Here's a good link:
http://www.fieldlines.com/story/2007/10/26/12500/761
Title: Re: Off-Grid Power Systems
Post by: MountainDon on October 28, 2007, 09:26:41 AM
Quote
Wait--I'm confused.
Derek, let's see what I can clarify.

But first a question: You used a figure of "A Sun Frost RF16, rated at 0.48kWh/day * 365 = 175kWh/year." I do see that number on the Sunfrost website. But the EPA figure for that model is 254 Kwh/year. Since all the figures on the EPA comparison chart have been arrived at by the same EPA testing method, and not what the manufacturer reported, I would only compare numbers from that EPA worksheet.

There is a Sunfrost, model RF12, that carries an EPA rating of 171 Kwh/year, but it's smaller.

I picked a Kenmore model at random for the example calculation of 480 Kwh/year. Some of the models on the EPA sheet may not be currently available except from old inventory. So today I went to the Sears website and used their selection eliminator. I came up with some available Kenmore fridges to compare.  One is their model# 6787. It uses 407 Kwh/year (EPA). Part of the problem with comparing this Kenmore to the Sunfrost of the size. Kenmore just doesn't have a model that's really comparable to the SF R-16. The Kenmore is bigger.  :-/

Searching some more, a more comparably sized Frigidaire, FRT17HB3C, has an EPA rating of 391 Kwh/year. Not much better than the larger Kenmore. Therefore I believe it's safe to say that it would not be difficult to find a "normal" Energy Star fridge that uses about 400 Kwh/year.

400 Kwh is 146 Kwh more than 254 Kwh; 57% more than 254. So the Sunfrost appears to the Energy Star King (out of available ready to use new refrigerators) , but at a price of around $2600 - 2800 + freight

Now, back to my statement "480 Kwh/year, 40 Kwh a month. That calculates to 7 x 175 PV panels and 6 of the 6 VDC 350 amp batteries just to serve the refrigerator!!" That was calculated on tjm73's solar deficient location. The tables indicate Rochester, NY has a minimum winter solar sun-hours of 1.58. For comparison my NM location has a minimum winter solar sun-hours of 6.01. That's 3.8 times as much usable solar sunshine, or 3.8 times fewer PV panels required. Geographic location makes a big difference in calculating solar PV power generation expense.

Re-running the Rochester figures at 400 Kwh, instead of 480 reduces the # of 175 watt panels to 6, instead of 7.

Running the numbers for my NM location on the 400 Kwh fridge gives the result of 2 panels required. Lucky me. My location is what I based my statement: "....however, I am not convinced that the large additional cash outlay for the Sunfrost (type) is counterbalanced by the lower energy use.", on. I should have emphasized that my opinion was based on a location with similar solar exposure. That was deficient on my part and I'm sorry for that.

At this point I have to consider whether or not the expensive Sun frost ( $2600+) is the correct choice, or the relatively cheap (<$500) Frigidaire plus 175 watt 2 panels, $1600 (+ batteries ?). Or maybe the Servel propane at is the best choice, best compromise at around $1300 shipped to my home city.  :-/ :-/ :-/  (Compromise because propane is a fossil fuel you buy from somebody else. And no, I don't want to get into methane production, or whatever.  ;D

I hope I made some sense.





Title: Re: Off-Grid Power Systems
Post by: MountainDon on October 28, 2007, 12:02:08 PM
Quote
.....New Kill-a-Watt EZ   and the    Watts Up Pro
I had a quick look. The Kill-a-Watt EZ is much like the older one I have, but without the cost calculator. Since I've never bothered calculating the actual cost from the power company, that doesn't really interest me if I have to pay more than $5 for the feature. [I never looked at the price diff between old and EZ]

The Watts Up Pro offers more ability, especially if you spring for the optional computer interface/software. But once again, for my purposes all I wanted to do was obtain some real world power use figures. If I make changes and reduce actual power paid for my meter and power bill tells me what's really important. But that's just me. [Watts Up Pro is tempting, but I have enough things to occupy my time.   ;D]
Title: Re: Off-Grid Power Systems
Post by: peter nap on October 28, 2007, 12:21:41 PM
The biggest thing I liked about the watts up, is the ability to chart usage over time. I worked for this states  utility commission for a number of years and monthly charting saved the day for a lot of customers having a spat with Virginia power.
Of course, in those days, we used meters wit real paper charts in it.

I can't resist telling this story.

I had one fellow who had the nerve to claim Vepco was overcharging him. I went out and tested his meter and it was 99.99999. He still wasn't happy. I looked at his bills and they looked way too low for what he was using. All the seals were good on the meter so I put a graph meter in the line.

A month later, he was still bitching so I told the company to swap his meter. He went ballistic over that. The next month, his bill nearly doubled so I checked the graph...same usage. I had the Power Company pull the meter apart and found he had wired a photoresistor in line with the potential coil. When the sun went down, it quit recording.

Why he complained....I haven't a clue :o But having that chart as a reference was a lot of help.
Title: Re: Off-Grid Power Systems
Post by: MountainDon on October 28, 2007, 12:24:24 PM
As for converting a chest freezer into a chest refrigerator, the successful tinkering would bring personal satisfaction.  :) But I don't like chest fridges or freezers.  :(

We have a small chest freezer and a small upright, and there is no doubt the chest is more efficient than the upright, mainly (only?) because the cold air doesn't spill out when you open the door. But I always seem to be rummaging more in the chest type than I do in the upright. When possible most frozen goods are in the upright with the chest reserved for overflow of things like a dead elk/deer/cow. If you don't open the door a lot I don't think the upright is much worse than the chest.  :-/

I might rethink my home side by side fridge/freezer if I was solar generating all my power and storing the power in enough batteries to run everything when the sun doesn't shine.

So I'm kind of here and there on this power question. At home one set of criteria [for grid intertie] and in the mountains [off grid] another.

Title: Re: Off-Grid Power Systems
Post by: MountainDon on October 28, 2007, 12:45:04 PM
Of course for the die-hard tinkerer one could always build their own ammonia absorption refrigerator and/or freezer.  ::) ;D

http://www.nh3tech.org/abs.html

Like Allie Fox (Harrison Ford) in Paul Theroux's book, made in to a movie  "The Mosquito Coast".

http://www.amazon.com/Mosquito-Coast-Paul-Theroux/dp/0618658963/ref=pd_bbs_sr_2/105-7550156-2238024?ie=UTF8&s=books&qid=1193607783&sr=8-2

http://en.wikipedia.org/wiki/The_Mosquito_Coast

http://www.peterweircave.com/mosquito/
Title: Re: Off-Grid Power Systems
Post by: MountainDon on October 28, 2007, 02:04:12 PM
Quote
I can't resist telling this story.
Love that story, Peter. Makes you wonder.... must have forgotten he tampered with the meter. I'd think that swapping the meter would be one of the first things if a customer complained enough.

I heard of a case, or cases, back home where several neighbors on one street got caught stealing power from the power company. Back then the city owned hydro company did a lot of flat rate water heater hookups. You paid by the size and number of electric heater elements in the tank. People swapping their smaller elements or adding a second was commonplace, but those folks were usually caught more readily. I think there was a tank size factor as well. But there was no controller that limited the amount of power that could be used. That was strictly limited by cable and fuse size. The water heaters were all situated in the basement and wired with BX armored cable. So the one neighbor replaced the cable with heavier and jumped up the fuses too. Then he used that power for some special outlets he used for electric room heaters. He did several neighbors too. They got caught when one of the neighbors got caught when he complained about blowing fuses frequently.
Title: Re: Off-Grid Power Systems
Post by: glenn kangiser on October 28, 2007, 02:24:26 PM
Don't forget about our member, Gary's website-- lots of free stuff there.  http://www.builditsolar.com/

Gary has a link to the Solar Ice project from Home Power. I thinke I have a copy of the PDF somewhere.  It used to be free but is now a $5 archive item from HP.

(https://countryplans.com/smf/proxy.php?request=http%3A%2F%2Fwww.builditsolar.com%2FProjects%2FOddProjects%2FHp53AmmoniaFrig.jpg&hash=71177fd405d6169f95c7f15f20d1720b6b0f9600)

You could build one from the information in this PDF.
Title: Re: Off-Grid Power Systems
Post by: glenn kangiser on October 28, 2007, 02:33:47 PM
Matter of fact I do -

(https://countryplans.com/smf/proxy.php?request=http%3A%2F%2Fi35.photobucket.com%2Falbums%2Fd184%2Fglennkangiser%2Fsolarthermalicemakerfromsolarice.jpg&hash=8ea17a885cf0faab68e7521dc83747e50ea5c93d)
Title: Re: Off-Grid Power Systems
Post by: Sassy on October 28, 2007, 05:51:52 PM
After we started spending most of our time in the underground cabin, I kept expecting the power bills to decrease  at our house in the valley - they just kept going higher.  I called the power company to inquire - they asked me to go out & read what the meter #'s were.  I read them back - they kept telling me I needed another # - I said "no, there are only 4 #'s!"  Anyway, come to find out, they had been reading the meter wrong - it was an old meter - after that the bills were about a 1/3 of what they had been.  The month I called, the bill was around $275-300 - the next month, $80 & they've been low ever since.  Never could get them to refund all the over-charges  >:(
Title: Re: Off-Grid Power Systems
Post by: glenn kangiser on October 28, 2007, 06:42:59 PM
We suspect that they had been adding a zero at the end or somehow making up the 5th number that the new meters have.  I think our meter was from 1952.
Title: Re: Off-Grid Power Systems
Post by: tjm73 on October 29, 2007, 05:26:21 PM
Quote
After we started spending most of our time in the underground cabin, I kept expecting the power bills to decrease  at our house in the valley - they just kept going higher.  I called the power company to inquire - they asked me to go out & read what the meter #'s were.  I read them back - they kept telling me I needed another # - I said "no, there are only 4 #'s!"  Anyway, come to find out, they had been reading the meter wrong - it was an old meter - after that the bills were about a 1/3 of what they had been.  The month I called, the bill was around $275-300 - the next month, $80 & they've been low ever since.  Never could get them to refund all the over-charges  >:(

I woudl think documented overcharges could be used to force at least a credit applied to future bills.
Title: Re: Off-Grid Power Systems
Post by: Madroaster on October 29, 2007, 05:50:39 PM
Quote
Quote
Wait--I'm confused.
Derek, let's see what I can clarify.

But first a question: You used a figure of "A Sun Frost RF16, rated at 0.48kWh/day * 365 = 175kWh/year." I do see that number on the Sunfrost website. But the EPA figure for that model is 254 Kwh/year. Since all the figures on the EPA comparison chart have been arrived at by the same EPA testing method, and not what the manufacturer reported, I would only compare numbers from that EPA worksheet.

Agreed.  My bad.

Quote
There is a Sunfrost, model RF12, that carries an EPA rating of 171 Kwh/year, but it's smaller.

I picked a Kenmore model at random for the example calculation of 480 Kwh/year. Some of the models on the EPA sheet may not be currently available except from old inventory. So today I went to the Sears website and used their selection eliminator. I came up with some available Kenmore fridges to compare.  One is their model# 6787. It uses 407 Kwh/year (EPA). Part of the problem with comparing this Kenmore to the Sunfrost of the size. Kenmore just doesn't have a model that's really comparable to the SF R-16. The Kenmore is bigger.  :-/

Danby makes a manual defrost 17CuFt fridge (no freezer), D1707W which is pretty close to the R16.  It uses 335kWh/year according to the EPA.  That's a good approximation.

Quote
Searching some more, a more comparably sized Frigidaire, FRT17HB3C, has an EPA rating of 391 Kwh/year. Not much better than the larger Kenmore. Therefore I believe it's safe to say that it would not be difficult to find a "normal" Energy Star fridge that uses about 400 Kwh/year.

400 Kwh is 146 Kwh more than 254 Kwh; 57% more than 254. So the Sunfrost appears to the Energy Star King (out of available ready to use new refrigerators) , but at a price of around $2600 - 2800 + freight

Now, back to my statement "480 Kwh/year, 40 Kwh a month. That calculates to 7 x 175 PV panels and 6 of the 6 VDC 350 amp batteries just to serve the refrigerator!!" That was calculated on tjm73's solar deficient location. The tables indicate Rochester, NY has a minimum winter solar sun-hours of 1.58. For comparison my NM location has a minimum winter solar sun-hours of 6.01. That's 3.8 times as much usable solar sunshine, or 3.8 times fewer PV panels required. Geographic location makes a big difference in calculating solar PV power generation expense.

Ahah.  I didn't realize you were referring to his specific location.  That does make a big difference.

Thanks for the clarification.  It makes perfect sense now.  I'm in the same boat you are...which appliances to use with which power system.  Sometimes my head hurts.  Hopefully my wallet won't.
Title: Re: Off-Grid Power Systems
Post by: MountainDon on October 29, 2007, 05:56:41 PM
Quote
Danby makes a manual defrost 17CuFt fridge (no freezer),
Yes, the freezerless fridges do use less. But I want and use a freezer. Been used to having one for so long it's a must. But if you don't need a freezer that could be an excellent choice. I beieve sunfrost makes some fridge only too. But still pricey.

I believe one of the things tat makes the RF-16 so good is it has a compressor for the fridge and one for the freezer.

A normal fridge actually only cools the freezer. There's a bleed of cold air (for lack of knowing the proper term) from the freezer to fridge.
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