specific application battery bank (and system) help

[isee]

As mentioned in other posts my knowledge of green generation and living is purely theoretical, but I am keen to learn.

So rather than asking vague questions I thought I'd ask something specific to my needs.
I have a biltong/salami/jerky maker in my workshop. It uses a 240volt 70w lighbulb and a 14CM, 12V PC fan (i believe it's draw to be in the region of 3ah)

Can you please guide me with regards to calculating the total power usage as well as then correctly sizing the battery bank I would need to keep this box going 24/7 completely off grid?
In other words I need to charge the battery bank and keep the device running during the day and then have the batteries take over during the night.

I understand that doing it might not make financial sense, but please humour me.

[Flux]

Let's say 80W to cover the fan, so 1/3A at 240v.  At the 12v end you are looking at 20 times 1/3A or7A.  For 24hrs that is 170 Ah approx.

In a miserable November in the uk you may get 2 weeks with no useful solar power so 14 x 170 = 2380 Ah before we look at efficiencies. Do I need to carry on?

Flux

[DamonHD]

My off-grid storage is sized to allow 3 weeks without significant input.

Current load ~2W--4W (50--100Wh/day) with batteries of 12V 400Ah (2400Wh usable).

Rgds

Damon

[Mary B]

I can get a week of no sun here in MN, reason I have a 120vac charger to keep things topped off

[isee]

In other words, renewable micro-generation is still uneconomical to the average person and remains the domain of rich or incredibly committed. Shame we cut the feed-in rates so much and so early...

[Bruce S]

In other words, renewable micro-generation is still uneconomical to the average person and remains the domain of rich or incredibly committed. Shame we cut the feed-in rates so much and so early...

I don't see this statement to be totally true.
As the "average" person begins to try AE systems, they also quickly realize they can lower their battery or generations needs by merely adjusting their daily power needs.
This then becomes part of that total equation.
I'm not rich nor am I totally committed to being off the grid, BUT my daily needs and therefore monthly costs have steadily become less.
My solar setup would actually be considered as sub-micro :-).
BUT by doing the math and then implementing small changes that are no where near considered draconian is now paying off in less worries when the grid goes dark.
It's not about the now , for me , it's about the near future.

Cheers;
Bruce S   

[gww]

Bruce
I agree with your statement.  I put my system together knowing I was going to retire and be on a fixed income.  I don't blieve my system would be payed for if I had fifty years to do it.  I did build it by doing some overtime and knowing when I retired I wouldn't have things like overtime to relie on.  Could I have saved my money and just used it to pay my bill. yea I could have but now no matter what happens a portion of what I use in power will stay at todays rate (barring equiptment breakdown)  and as a side binnifit I actually think about turnning the lights off when I leave a room.  There is something about watching a meter and thinking about what it is saying to you that make you want to improve in other areas of power use.  Lastly I haven't proved to myself that I could save the money and use it just for electric cause I didn't save a bunch for retirement so I feel my investment is good even if it doesn't work out on paper yet.  It also kept me busy and moving while installing and now keeping up with IE getting up to look at the monitors.  That and having to feed the chickens may keep me moving enough that I don't get bed sores from sitting around so much.  beneifits come in many forms.
Gww

[isee]

I may have been a bit too harsh. I should have said that the green generation of electricity isn't currently for me. Generating heat on the other hand might be worth looking into.

[madlabs]

ISEE,

A little more info would be helpful. What is your sun window like where you are? How many hours of sun in the winter and in the summer? Do you have space and money for a few panels or do you already have some?

In your situation I wouldn't worry about having days worth of stored energy. If there is sun, great, use it. If not, run the food dryer from the grid.

Even better would be to build a solar dryer and install the guts of your current dryer in it. Then, if the sun is shining you are drying the food and charging the battery. At night switch over to batteries, unless they aren't charged, in which case go to grid power.

Jonathan

[Bruce S]

isee;
Don't worry about coming across harsh. We've all been there.
Using solar heated air , if done with cast off "stuff" (stuff=beer cans  or the like ) can pay for the labor in about two winters.
There are quite a few posts here , as well as another site" http://www.builditsolar.com/ " that can give you real world experiences.
Gary Gary : still posts here sometimes and will certainly answer most questions. He is a very well respected poster and his site is from him doing the actual work with other possible avenues.

Having a wife in the food biz; I can understand the needs for high temps to keep the food within safe temps and the high energy uses that comes along with that too.

Your energy needs may not be typical.
The stainless steel chill table I built for her to temper chocolates, using solidstate peltier devices could certainly be a battery killer!
Best of luck

[DamonHD]

@isee In the UK, at least not in the northernmost corners, grid-tied PV should pay off within 10 years and be 'profitable' after that.  The automatic FiT digression tries to keep that so.

I paid off my mortgage, did some insulation, and my PV means that I effectively no longer have energy bills (FiT payments and reduced consumption from paying attention as mentioned above).

http://www.superhomes.org.uk/119

Biggest expenses are really food and clothes for the kids.  I guess if I fed them less the clothes problem would be reduced too.  %-P

Basically renewables investment has paid up front for my energy bills and my outgoings are halved, and that gives me time to work on my exciting new start-up in ... energy saving!  B^>

Rgds

Damon

[isee]

ISEE,

A little more info would be helpful. What is your sun window like where you are? How many hours of sun in the winter and in the summer? Do you have space and money for a few panels or do you already have some?

In your situation I wouldn't worry about having days worth of stored energy. If there is sun, great, use it. If not, run the food dryer from the grid.

Even better would be to build a solar dryer and install the guts of your current dryer in it. Then, if the sun is shining you are drying the food and charging the battery. At night switch over to batteries, unless they aren't charged, in which case go to grid power.

Jonathan

I have a south facing garden in London and the workshop is a separate building with a flat roof that would fit about 6 panels I guess. For the salami box, I think I would need just one though (250w).
I feel like hitting myself in the forehead... Running the heated air through the salami box would be a fantastic idea!

Thanks!

[isee]

@isee In the UK, at least not in the northernmost corners, grid-tied PV should pay off within 10 years and be 'profitable' after that.  The automatic FiT digression tries to keep that so.

I paid off my mortgage, did some insulation, and my PV means that I effectively no longer have energy bills (FiT payments and reduced consumption from paying attention as mentioned above).

http://www.superhomes.org.uk/119

Biggest expenses are really food and clothes for the kids.  I guess if I fed them less the clothes problem would be reduced too.  %-P

Basically renewables investment has paid up front for my energy bills and my outgoings are halved, and that gives me time to work on my exciting new start-up in ... energy saving!  B^>

Rgds

Damon

Still paying mortgage, but am getting a tad fed up with the £250 in monthly energy cost. It doesn't help that my wife cannot sleep without the fresh air coming through the window though.

[DamonHD]

Does "fresh" necessarily mean "cold"?

Consider fitting single-room MHRV (Mechanical Heat Recovery Ventilation) of which I have two, and you get bags of fresh air for vastly reduced heat loss (3x typically).

My *annual* gas and electricity bill, even ignoring FiTs, are each less than £250.

Rgds

Damon

[madlabs]

ISEE,

Yeah, the beauty is that if there is enough sun to charge batteries there is enough to dry food. Then your panel can charge batteries instead of drying food and thus you need less panel/exposure to dry your food.

I have an appalachian style dryer that I built. It doesn't have any electric heat though. When I made it I didn't have much power (I'm off-grid). Maybe I'll add some heat this year, I have enough power now. As it is I just go out and close it at night.

JOnathan

[gww]

I....
I hope that whatever you find the time and resources to do that you keep posting here and I want to be the first to let you know that we love pictures as you go.
Even though I try my best to sound like I know everything, I believe you might bring something or appoch matters in a way that allows me to learn more.
Thanks
gww

[isee]

I....
I hope that whatever you find the time and resources to do that you keep posting here and I want to be the first to let you know that we love pictures as you go.
Even though I try my best to sound like I know everything, I believe you might bring something or appoch matters in a way that allows me to learn more.
Thanks
gww

Thanks Gww,

I've already priced up all the parts i'd need to make the active space heater i have in mind, even from B&Q it's coming out at under £100, which is great! Will definitely post pics and instructions as well as actual heating data once I get round to it.