Off-Grid Planning

[Tobit]

My 2x275W SolarWorld panels arrived the other day, very nice looking panels and they actually came in under quoted price by a few cents/watt.  I think I am going to add one more which will be max for the KID CC.  I'm going to start looking for some decent 225AH 6V batteries next.

[Tobit]

vtMaps, sorry if it sounded like I was being overly stubborn on the Sundanzers.  I am open to other suggestions as refrigeration and freezer are going to be my two largest power consumers.  I don't want a huge battery bank and solar array but I do want to run quality batteries and the batteries play a major role in the cost.  Since I found someone close by to my present location who can ship me panels for only $25, I will most likely be adding the third 275W panel to get me to 825W and a 24V 225AH battery bank sounds like it will play well.

I was looking at the Sundanzers because their smallest ones are 1.8 liter in size which is plenty for me.  I also prefer chest style over front door.  In fact, freezer size is more important to me than refrigeration.  Other than keeping things like eggs, butter, and a few condiments cold.  I don't see a need to get anything larger than 1.8 liters. 

My climate is southern Missouri.  Winter nights will get below freezing, down to 0 on a few occasions, but it usually warms back up to the low 30s during the days although last winter was one of the coldest in decades according to a friend who lives 2 miles from my off-grid location .  The shed will have a fair amount of water storage in it so I plan to insulate it well and it may have a tiny wood stove for those rare nights it gets super cold.  I could also always unplug the refrigerator during the night on those cold winters. 

If there is something that'd be more efficient than the small Sundanzer freezer, I'm listening.  Over on another forum, I think you are a member there as well, I heard about a Stecca 24V unit but they seem hard to find here in the US.  Again, I will be living alone and only have my mouth to feed.  I plan to hunt a couple times a year so vacuumed packed meat in my freezer is important.

Edit: Maybe go with a slightly larger inverter and a freezer like this http://tinyurl.com/ky296vt and a fridge like this http://tinyurl.com/lcnpkwt ?

[zoneblue]

Im still not sure that you have enough PV for a fridge and a freezer. Refridgeration is a hard task master. And when it comes to power use/efficiency, you either spend the big bickys on the fridge or you spend it on the rest of the system... to power less efficient units/inverter losses etc.

[Tobit]

825W of PV cannot power a fridge and freezer unit?

[TomW]

825W of PV cannot power a fridge and freezer unit?

It probably matters "where" but for years I ran a full size fridge and 2 smallish freezers as base loads on 820 watts of panels. Seldom needed to switch to grid or charger. It did other stuff but mostly on an opportunity basis like running the washer.

Then this year with 2350 watts I have had stretches of 3 days of switching them to the grid from lack of incoming power combined with improper load management.

So it can be all over the map but anywhere reasonably sunny that seems it should  be enough.

Just from here in my real world situation.

Tom

[Tobit]

Im still not sure that you have enough PV for a fridge and a freezer.

Tiny 1.8 cu. ft. fridge and 5.0 cu. ft. freezer I am looking at, kWh/year numbers from energy star labels:

240+260=500KWH/year 500/365= 1.37 KWH/day

825 watts x 4.9 hours (solar insolation average for Springfield MO) =4042.5 = approximately 4 KWH/day

Would appear I'd have plenty of PV buffer in the array, especially in summer when insolation climbs to 6.  In winter, since they'd be in the shed, they'd hardly run if I keep temps just above freezing.

I could actually save energy by going with a conventional fridge/freezer combo but the fridge areas are much larger than I need with smaller freezers sections.

[ClassicCrazy]

Some of those little fridges have the same size compressor of a larger refrigerator. True it may not have to run as long - but consider a larger refrigerator instead of those mini ones - the kind with manual defrost. You might be surprised it doesn't take too much more energy for the extra room you get - plus the much larger freezer section.

Also be aware that some refrigeration may not operate properly outside if it gets too cold.  The refrigerator I am using a friend gave me - it had a bad cold control so I replaced it with one of the $15 digital ones you see on ebay and it works with very good precision now.

[Tobit]

Some of those little fridges have the same size compressor of a larger refrigerator. True it may not have to run as long - but consider a larger refrigerator instead of those mini ones - the kind with manual defrost. You might be surprised it doesn't take too much more energy for the extra room you get - plus the much larger freezer section.

See, that's the thing.  I don't need large refrigeration.  I'm just one person who doesn't drink milk, soda, beer, juices, and use a wide variety of condiments and leftovers that need a lot of refrigeration space.  I drink water, tea, and coffee.  A freezer, on the other hand, is something I'd get more use out of and this 5 cu. ft. chest freezer I am looking at would be perfect.  I just need an energy efficient way of keeping small things like butter and eggs.

Again, I'll be keeping my shed, where the freezer and reefer will be located, just above freezing as my shed will also be used for water storage.

[TomW]

Just a thought for low capacity cooling...

Try using an old fashioned "ice box" or cooler and swap frozen water in jugs into the cooler?

The up side of a freezer full of frozen jugs is it will run very little.

Based on you having a freezer anyway.  Plus less equipment to fail?

Just tossing it on the wall to see if it sticks.

Tom

[ClassicCrazy]

That ice box idea is a good one - well insulated box and a jug of frozen water will keep it cool enough. And as Tom says - easy to swap out a frozen jug from the freezer.

[Tobit]

Yeah, that's a good idea Tom.  It is definitely worth a try.  I used to have an old-fashioned ice-box when I lived on a small sailboat and it worked quite well.  However, the ambient temperature down in the cabin always seemed much cooler than outside probably due to being partly in the ocean. 

I'll give it a go before investing in a fridge.  Freezer and and old-fashioned ice-box.  I dig it.

[TomW]

Yeah, that's a good idea Tom.  It is definitely worth a try.  I used to have an old-fashioned ice-box when I lived on a small sailboat and it worked quite well.  However, the ambient temperature down in the cabin always seemed much cooler than outside probably due to being partly in the ocean. 

I'll give it a go before investing in a fridge.  Freezer and and old-fashioned ice-box.  I dig it.

Might look at those extra thick styrofoam coolers they sell in summer for extended camping, several inches thick but likely need a box around them for long term use.

We used one with dry ice to keep bacon frozen that we bought vacationing in the west and kept it frozen for days on a hunk of dry ice.

I love the bacon selections out west much better than here in the corn belt where we have millions of hogs?

Tom

[zoneblue]

Ill say it again. Refrdigeration is a relentless load.  Small fridges are as bad or even worse than bigger fridges because there is less room for insulation. Dont rely on published numbers, they are for certain optimistic "marketing" conditions that you may not find exist in your setup.

If you are willing to spend the bucks you can buy super insulated units, and then your minimum pv thing will work.

Its an exceptional fridge that uses less than 1000Wh per day and an exceptional freezer that uses less than 1500Wh/day. Worse case, for cheap off the shelf whiteware would be 3000Wh/day for both.

If you think you can consistently produce 3kWh/day from 800Wp pv you clearly live somewhere a lot more sunny that me.

Be careful to use realistic data, else your design will not satisfy. Living off grid with insufficent pv is a misery. And ... PV is cheap!

[Tobit]

If you think you can consistently produce 3kWh/day from 800Wp pv you clearly live somewhere a lot more sunny that me.

The weather is always a gamble but, based on insolation numbers, with 825W of PV, I am showing the ability to produce 95-104 kWh/month from March - Sept. at my location in southern, MO.  I am also on a south facing slope of a ridge at 1400'.  Drops down to 75 to 80's all other months but those are the coldest months anyway where the freezer will not run as much.

As I stated in my last couple of posts, I'm going to ditch the idea of a traditional fridge and stick with just a single 5.0 cu. ft. freezer and build a well insulated, old-fashioned, ice chest cooler for the small amount of items such as butter and cheese that'll need it.  The fridge is still a relative modern convenience.  I think I can live without it if I have a good freezer for making ice jugs.

[zoneblue]

The weather is always a gamble but, based on insolation numbers, with 825W of PV, I am showing the ability to produce 95-104 kWh/month from March - Sept. at my location in southern, MO.

Unlike virtually every other load off gridders have, a fridge in particular doesnt understand monthly averages, it runs 24/7, and the weather ... you know how she is, sunny one day rainy the next,...fickle, and batterys are expensive, so...

As I stated in my last couple of posts, I'm going to ditch the idea of a traditional fridge and stick with just a single 5.0 cu. ft. freezer and build a well insulated, old-fashioned, ice chest cooler for the small amount of items such as butter and cheese that'll need it.  The fridge is still a relative modern convenience.  I think I can live without it if I have a good freezer for making ice jugs.

Cool. Theres always room for simpler lives.