Basic off grid system

System

I'm a real beginner and I thank you for any advice. I'm interested in an off-grid solar energy system to power a fridge in the event of a primary power failure at my house. However, I don't know exactly what I'd be getting myself into. I could buy a fridge based on some posts I reviewed here (like an energy star). I have a gas generator but it has its downsides (noise and fuel). Can you tell me what things I should consider, basic components I would need, a ballpark cost? Mike

BB.

Re: Basic off grid system

Mike,

It will not be cheap to go with off-grid solar just to power a fridge in an emergency.

Assuming you are somewhere around Columbus Ohio--a 1 kW solar array would supply about 1 kWhr per day in December up to around 2+ kWhrs per day for 9 months out of the year....

A really wild guess to build such a system would be around $10-$15 per watt or $10k-$15k (plus a bit more for permits and professional install)... Depending on what you install (and where) you can get 30% or more in government tax credits and rebates.

Because solar is so expensive, it is better to conserve first (such as a good energy star fridge) than to try and build a larger system (as you can see, it is not cheap).

Personally, I have a grid tied system and a Honda eu2000i generator. Very fuel efficient and quiet. Fuel can be used in car to bug-out if needed (my need is probably for a once in a lifetime earthquake--different than your needs).

And given that solar needs sun--you probably will still need a generator to cover bad weather (more than three days of no sun)--the the genset/fuel issue does not go away--just reduced.

The above numbers are just a really rough guess to start a discussion--I can easily be off by -50% or +100%--depending on a whole bunch of stuff.

-Bill

niel

Re: Basic off grid system

seems like he just wants to be able to run the refrig at times without the noise from the genny and that is a reasonable want, especially at night. firstly, i am assuming you may have read some of the other threads that may have addressed some of this or at least i get that indication. i will generalize and take you through a bit of a general process and you may need to specify what it is you would elect to do and would need to specify what kind of loads we are talking about per day in kwh.

if the genny is large enough to recharge the batteries in a backups system (inverter/charger combo and properly sized battery bank for your loads) without pv and run the refrig at the same time this might be a good option as the pvs are expensive. this would assume you have lost your utility power and that which was stored in the batteries has already exhausted to about 50% dod. the problem is many small gennies don't handle both and would depend on the genny you have if this is viable. there may be other loads added to this by you for lights, radios, tvs, etc on top of the huge load the charger and refrig would pose and hence you would need another power source.

enter solar here that can be added. this is expandable in an add as you go thing and you'd want to start with pvs that can deliver at least 1% of the battery capacity to float charge the batteries. this won't recharge the batteries during a prolonged outage, but will maintain them. to start charging you'd need at least a 5% rate of charge going to batteries and note that a 5% rate of charge is a 20hr rate. if you get 5 full rated sun hours per day you can see the dilemma that has developed as it will take more than a day to recharge from 50% dod and is actually 2 days if no clouds or rain or midwinter days. now you need more pvs to replenish it in a day and boosts it to a 10% rate of charge. if your sun is out 75% of the time considering clouds or rain (wishful thinking it's that good for ohio) you will want another 25% more in pv to store and use the next good day. now 12.5% is around the max charge rate of 13% we recommend without knowing or getting the manufacturer's recommendation for flooded lead acid (fla) batteries.

if one takes into account the efficiencies and losses of such a system you may find you will need to add 20-40% more on the 12.5% as these are dependent on the actual items obtained and how configured. you are now looking at over the 13% rate and i recommend agms for rates this high. the design will be around 15-17.5% and we aren't being specific yet on a system based on whrs needed yet.

i don't mean to scare you with all of this, but it does get involved with much to consider and the costs will be high as solar usually is. it can be done, but what you would need specifically i can't say and some things aren't as clear cut either as you may want one inverter/charger over another or you may elect to use straight pwm charge controllers rather than the higher cost of the more efficient mppt charge controllers.

bb,
i should mention that conserving during an outage is a forced issue.:roll::D