Moving Ahead with Off grid move... Amish style!

Rngr275

As the closing on our Amish farm approaches, I am trying to be very hard to get things organized and lined up. Per suggestions and past posts, I am engaged with 2 different contractors who are certified solar installer types. Both currently live off Grid and have for a number of years. I have a concern about the one since he has to be reminded a couple times to do what he has said he would do. They are both going to supply me with details of what their services include, a recommendation of what a personalized system for me would include and cost. After I provide them a list of my estimated loads (I was glad they both asked for that). I have a couple things I want to bounce off of you guys.

The one guy (whom I like and calls back) told me that he tries to persuade "New" off gridders and especially meto go with cheaper golf cart batteries initially. In a way it makes sense because I have read many a horror story of rookies trashing their first set of batteries, We are going into this as an experiment since we can get the grid (big $$$) if needed but we want to give off grid a serious attempt 1-3 years which is in the range of having to replace that type of battery. If we do decide to stay off grid I would then replace the battery bank with a better battery. I have also made it clear that I want to be able to use as much of the equipment in the future to tie to the grid if we decide to. Does this make sense to you?

Power use question. Bought my Kill a Watt and have it connected to our small energy star spare refrigerator. When it runs it is drawing 95w. It has been on there for 31hours and has used 0.65Kwh. I am having a hard time coming up with a useful Kwh number because it is a spare frig and doesn't get used (door open closed much). Any idea how I could put a better usage number on my load sheet. How often does a frig run how long, etc. I was thinking of using say 18hr at 95w=1700whr... does that seem high/low OK? What are your thoughts.

Also, those load sheets/forms seem to total everything even thogh some appliances only get used a couple hours a couple times a week as compared to say a water pump used everyday but for a shorter time. How do you or he/they decide the system (panels,battery bank) size.

Thanks
All

McD

Cariboocoot

Re: Moving Ahead with Off grid move... Amish style!

That first guy is telling you the truth about the batteries. The golf cart units are very inexpensive sources of Watt hours because so many of them are made and sold. Being "open" you can check the specific gravity (unlike a sealed AGM). The FLA's are more forgiving of mistakes, and if you do absolutely blow it you won't be out a ton of money. All that aside, sometimes the things last a long, long time - making them a great bargain in power.

As for using the same equipment in future for GT. Forget it. Although it can be done, most of the stuff will not be compatible unless you spend the big money and put in a hybrid (battery based GT) inverter now. Retrofitting to it later will be only one step away from tossing everything but the panels and starting new. They are majorly different.

The numbers you got from your 'frige on the K-A-W are accurate. 650 Watt hours over 31 hours = 21 Watts per hour * 24 hours that's 0.504 kW hours per day. That is every bit as valid a number as anything else. There's no need to go in multiples of 1 kW hour per day. If this is typical use, that's what you should plan on. If it's atypical use it will be inaccurate.

The load calculation sheets start off with the big handicap of assuming the Amps listed by manufacturers are accurate. They rarely are. That is usually a peak number, and I don't mean the start surge. As you know, some things get used more or less and trying to judge how many hours something is used each day is nearly impossible. Plugging it in to the meter, letting it run while people go about their daily routines, and pulling the actual Watt hours from that is far more accurate. Taking "3 Amps @ 120 VAC = 360 Watts" and then thinking "used about two hours a day = 720 Watt hours" is just one step away from guessing outright in my book.

Things you can't plug in to the meter are another matter. A well pump that's 240 VAC for example. You can use a clamp-on Ammeter to get a real number for how much it draws when running, but you'll have to do the calculation after that. Also things that are 120 VAC but "hard wired". You may want to temporarily install a plug on them so you can use the meter.

niel

Re: Moving Ahead with Off grid move... Amish style!

yes, the golf cart batteries are good to start with for if something goes wrong then you are out cheaper batteries. of course you may change the system too after trying it for a few years too.

the spare refrig seems to be very very good on its usage and most want 24hr readings for the load sheets. a bit of proportional math reveals about .5kwh per day. if in doubt then move the figure up. it may be due to not only the door being opened and closed, but also higher readings can be seen during hotter weather. maybe go .6kwh or .7kwh for the day, but it's up to you.

what refrig is this (make and model) that has such excellent figures on the killawatt meter?

Rngr275

Re: Moving Ahead with Off grid move... Amish style!

Cariboocoot wrote: »

That first guy is telling you the truth about the batteries. The golf cart units are very inexpensive sources of Watt hours because so many of them are made and sold. Being "open" you can check the specific gravity (unlike a sealed AGM). The FLA's are more forgiving of mistakes, and if you do absolutely blow it you won't be out a ton of money. All that aside, sometimes the things last a long, long time - making them a great bargain in power.

As for using the same equipment in future for GT. Forget it. Although it can be done, most of the stuff will not be compatible unless you spend the big money and put in a hybrid (battery based GT) inverter now. Retrofitting to it later will be only one step away from tossing everything but the panels and starting new. They are majorly different.

The numbers you got from your 'frige on the K-A-W are accurate. 650 Watt hours over 31 hours = 21 Watts per hour * 24 hours that's 0.504 kW hours per day. That is every bit as valid a number as anything else. There's no need to go in multiples of 1 kW hour per day. If this is typical use, that's what you should plan on. If it's atypical use it will be inaccurate.

The load calculation sheets start off with the big handicap of assuming the Amps listed by manufacturers are accurate. They rarely are. That is usually a peak number, and I don't mean the start surge. As you know, some things get used more or less and trying to judge how many hours something is used each day is nearly impossible. Plugging it in to the meter, letting it run while people go about their daily routines, and pulling the actual Watt hours from that is far more accurate. Taking "3 Amps @ 120 VAC = 360 Watts" and then thinking "used about two hours a day = 720 Watt hours" is just one step away from guessing outright in my book.

Things you can't plug in to the meter are another matter. A well pump that's 240 VAC for example. You can use a clamp-on Ammeter to get a real number for how much it draws when running, but you'll have to do the calculation after that. Also things that are 120 VAC but "hard wired". You may want to temporarily install a plug on them so you can use the meter.

PArt of what I ment about using equipment for grid tie is I want to be able to use the panels (big$$) and possible the inverter (big$$) and anything else that is possble. Can't use the same inverter? That sucks.I hope that if we do decide to tie to the grid 1) the batteries are dead or wearing out, 2) the grid will be my back up.

Or am I missing something with grid tie. Remember I am a rookie!

I will get the frige information when I get home. Also, as it is a spare it is in the basement so the ambient temp. is a little lower ~60F. It was new last year and energy star rated.

McD

Cariboocoot

Re: Moving Ahead with Off grid move... Amish style!

The two methods of what is usually called grid-tie:

1). Panels feed inverter directly. Whatever power that can be had from them goes to the AC wiring. This is the "straight" grid-tie and includes micro inverters.

2). Panels charge back-up battery bank. "Surplus" power above that is converted to AC and sent to the AC wiring. This is the hybrid grid-tie and requires an inverter designed to function this way.

Off-grid is a matter of inverter running off batteries which are recharged by panels. You can use the hybrid type inverter for this, but it costs more money than a standard off-grid inverter of the same capacity.

Some people use the grid as a "generator" for off-grid systems; connecting when necessary to supplement battery charging and power loads. This may be an option for you.

Often we get inquiries about using straight grid-tie inverters when the power is down. The frustration of not be able to have any AC in an outage when you have thousands of dollars in panel on the roof is extreme to say the least. There are ways around it, but they can be complex and/or cumbersome and again require planning and rewiring. The result has varying degrees of success too.

In short, it's best to plan ahead for what you want to do then. Having to pull out wires and change them because you now want/need a different system which needs a different configuration is really annoying. If you can see ahead to what you might be doing in the future you'll be able to plan for it now.

petertearai

Re: Moving Ahead with Off grid move... Amish style!

I tested my samsung fridge over 4 days with continual usage, door opening and closing etc. In the first 24 hours it used .9kw. Then for the subsequent 3 days .84 kw per day averaged. Energy star rating 339kw per year.

Rngr275

Re: Moving Ahead with Off grid move... Amish style!

The refrigerator is a Hotpoint HT17cb, we bought about a year and a half ago. Energy star usage at 370Kwh per year. Kill Watt is currently @ 1.26KW @ 56 hours, so we are at ~540Whrs per day. Not to shabby. I think that we will keep this one for the house when we move. Of course I am sure the KwHrs will go up some when we start using it more so I will fudge the w/day value up a little to build in a small buffer.

BB.

Re: Moving Ahead with Off grid move... Amish style!

Remember that refrigerators/freezers use more power in warm rooms... If you have a hot kitchen in the summer, it will probably use closer to 1 kWH per day (I believe the energy star ratings are for 90F room temperature--or at least the couple I looked at seem to match that environment).

Of course, for most people, the generate much more power during hot (sunny) weather when the extra power is needed.

-Bill

techntrek

Re: Moving Ahead with Off grid move... Amish style!

BB. wrote: »

Remember that refrigerators/freezers use more power in warm rooms... If you have a hot kitchen in the summer, it will probably use closer to 1 kWH per day

+1 Somewhere around here I posted the numbers for my inside fridge, which sits about 20 feet from my wood stove, one side of it is in full view of the stove so it gets hit with radiant heat, too. In the winter it uses way more than the summer when the A/C is on.

Edit: found the numbers for my stuff:

Winter numbers:
1. Chest freezer: 22 W-h (ambient temps 20-40F)
2.1 Fridge/freezer combo: 15 W-h (ambient temps 20-40F)
2.2 Fridge/freezer combo: 12 W-h (ambient temps teens-30F, same fridge as above)
3. Fridge/freezer combo: 51 W-h (15 feet from a wood stove running full blast, obviously this one is inside)

Summer numbers:
1. Chest freezer: 51 W-h (ambient temps 70s-80sF)
2 Fridge/freezer combo: 73.5 W-h (ambient temps 70s-80sF)
3. Fridge/freezer combo: 64 W-h (75F inside)