Solar Power Questions

Campesina · Oct 3, 2014

I have 8 - 280 watt solar panels, a 3500 watt inverter and 12 batteries. I am ready to get it all installed to replace edenorte power. I currently use about 850 to 900 KW hours per month so I am hoping this will be sufficient to do that. I run 7 to 9 fans 24 hours and 150 watts of light bulbs throughout the entire night. No ac of course but a midsize nedoca refrigerator and a flat screen TV several hours a day and a few during the night. I will be keeping the edenorte connected to use the ac, water heater and occasional shortages on cloudy days.

I have a spare 2000 watt inverter and can utilize the old battery bank (8) for outside lighting for a while if the panels are strong enough to charge all of it.... which I doubt.

My immediate question is what size controller do I need, the best place to buy it since I only need that and what it might cost me. It has been suggested that I need an 80 amp but also that I could use 2 - 35 amp which would be cheaper. Any advice would be appreciated.

Olly · Oct 3, 2014

Hi Campasina,
Well this is not entirely my area of expertise but a quick run of the maths suggest that you will only get about 16kWhour out of your panels and you use about 30 per day. This is based on north coast sun and the sort of charging rates you will get from the 8 panels.
It would be better to increase the panel to 12 and this would give you about 27kWhours on a fine sunny day. This is 12 kWh during the day to run you house plus 12 or so to charge the batteries for the night.

With the eight panels ONE 80 Amp controller would just be sufficient. With 12 panels you would need TWO 80 Amp controllers. (This assumes a 26 volt DC voltage)

Looking at you consumption the main usage is the 7 to 9 fans on 24 hours a day. (12kWhrs ) next comes the Fridge at about 2.8 kWhrs , TV at 1.8 kWhrs and then lights at about 1.5 kWhrs. This only totals 18.8kWhrs per day so where are you using the other 12kWhrs?

hope that helps

Olly and the Team

(ps the Electrical engineer is away at present so sorry for not geting back earlier)

windeguy · Oct 3, 2014

I suspect you will need closer to 16 to 20 panels to completely replace Edenorte based upon a study I did years ago based with about the same electricity usage. Since I don't have room for that many panels, it became a moot point for me.

donP · Oct 3, 2014

Insufficient

Campesina said:
I have 8 - 280 watt solar panels, a 3500 watt inverter and 12 batteries. I am ready to get it all installed to replace edenorte power. I currently use about 850 to 900 KW hours per month so I am hoping this will be sufficient to do that.

You get about 2.24 kWp.
I have 2.82 kWp and from that I get approx. 9.6 kWh/d, so about 285 kWh/month.
{Our consumption is about 245 kWh/d, so I am about +15% on the safe side.}

Your current consumption is much higher.
Thus your system is insufficient.

We use 2 Outback Flexmax 80 charger.
Ask AE whether she still is selling hers, they are an excellent choice.

donP

william webster · Oct 3, 2014

OK boys figure me

12 @ 195...... and a big battery bank -- 36 of the deep cycle gel

I seem to do fine.... as a precaution, I run the generator for an hour 8-9 pm... just to lock in the power for the night

windeguy · Oct 3, 2014

william webster said:
OK boys figure me

12 @ 195...... and a big battery bank -- 36 of the deep cycle gel

I seem to do fine.... as a precaution, I run the generator for an hour 8-9 pm... just to lock in the power for the night

You forgot to mention an important point. How much power do you use monthly? If 12 panels are working for you, then you are in donP's range of power consumption which is much lower than the OP

The OP is going to be very underpowered.

william webster · Oct 3, 2014

I do music all day - Tv at night - French door fridge, Impeller water pump...
maybe I'm kind of "Eco"... wouldn't know

I just use what I use... it was a few yrs ago.

On a sunny day, I'm rechagred by 12 -1pm

doesn't the storage capacity have an impact?

donP · Oct 3, 2014

Not much energy

william webster said:
OK boys figure me

12 @ 195...... and a big battery bank -- 36 of the deep cycle gel

I seem to do fine.... as a precaution, I run the generator for an hour 8-9 pm... just to lock in the power for the night

Different situation alltogether.
A large generator can push a lot of juice into the batteries.
Without that help, you'd only produce approx. 2.34 kWp, merely about 235 kWh/month.... :disappoin

donP

william webster · Oct 3, 2014

miesposa likes the pool loght .. I switched to LED.... 200w became 19..... lifesaver

thats my luxury... her luxury.......

donP · Oct 3, 2014

Many Ah's but not enough kW(p)

william webster said:
doesn't the storage capacity have an impact?

No, you have a surplus of storage capacity.
But your solar panels do not deliver enough power to utilize it well.
(Unless your generator does that.)

donP

windeguy · Oct 3, 2014

william webster said:
I do music all day - Tv at night - French door fridge, Impeller water pump...
maybe I'm kind of "Eco"... wouldn't know

I just use what I use... it was a few yrs ago.

On a sunny day, I'm rechagred by 12 -1pm

doesn't the storage capacity have an impact?

The storage capacity has these impacts:

1) If fully charged, you will of course have power that lasts longer than a smaller battery bank if you have nothing charging the batteries
2) The cost of having more batteries than you need for your usage is higher over time than if you match your requirements because wet cell batteries have a limited life time even if they are not used (drained and charged) heavily.
3) Having huge banks of 6 volt batteries can lead to imbalances in the charge rates of each bank if there are connection problems or batteries that are not "equal" to the others in the bank. That can cause premature failures of the batteries. It would be better to have one bank of 12 2 volt batteries that provide the same capacity of the 36 batteries you have.

Rolls Battery - Our Products

donP · Oct 3, 2014

Mermaid Hunting

william webster said:
miesposa likes the pool loght .. 200w....

Quite an advantage when it comes to hunting mermaids..... :bunny:

donP

Campesina · Oct 3, 2014

Part of my hours were wasted on water heating and unnecessary ac which has since been corrected. So more realistic future usage would be 600 to 650. So if I got a better control of the fans would it help that much? I always thought fans didn't take that much juice. As long as I already have the equipment except the controller, which I still don't know the cost, my new goal would be to stay under the magic number and only have to pay a minimal edenorte bill. Sounds like the fridge might be a huge consumer... I'll have to consider how to minimize and cut a few more areas. I am changing most lights to LED very low wattage. Hoping that might help.

Thank you all for your prompt responses. All very helpful, even for mermaid hunting tips.

william webster · Oct 3, 2014

keep the fridge full... even with bottles of water

my system has been trouble free since Jan 2009.....

just watch the wattage on everything you buy and get the lowest that works.

My night generator runnung is a new thing.... for years I got on well with little effort.
as I began to worry more (from reading here) I opted to augment my night time use.

It probably helps my batteries recoup faster the next day

cloudy/rainy days -- I hit the generator early

BTW - coffee maker is a HUGE culprit.....

windeguy · Oct 3, 2014

Campesina said:
Part of my hours were wasted on water heating and unnecessary ac which has since been corrected. So more realistic future usage would be 600 to 650. So if I got a better control of the fans would it help that much? I always thought fans didn't take that much juice. As long as I already have the equipment except the controller, which I still don't know the cost, my new goal would be to stay under the magic number and only have to pay a minimal edenorte bill. Sounds like the fridge might be a huge consumer... I'll have to consider how to minimize and cut a few more areas. I am changing most lights to LED very low wattage. Hoping that might help.

Thank you all for your prompt responses. All very helpful, even for mermaid hunting tips.

A fan does nothing to an unoccupied room, so turning off fans would help. They can use around 100 watts of power each. donP has 12 solar panels and has a slight energy surplus, but still uses much less than your projected power.

Campesina · Oct 3, 2014

So what if I only use the solar to charge the batteries and only use that during the night? In other words edenorte during the day and batteries during the night. Would the 8 panels completely recharge the batteries? I'm realizing now that I can only supplement my usage with what I now have.

I wish there was someone other than a salesman who could come and give me some suggestions. The solar companies tend to over estimate but will adjust those estimates just to get a sale, even though their final system won't performed as I need it to.

william webster · Oct 3, 2014

windeguy said:
The storage capacity has these impacts:

1) If fully charged, you will of course have power that lasts longer than a smaller battery bank if you have nothing charging the batteries
2) The cost of having more batteries than you need for your usage is higher over time than if you match your requirements because wet cell batteries have a limited life time even if they are not used (drained and charged) heavily.
3) Having huge banks of 6 volt batteries can lead to imbalances in the charge rates of each bank if there are connection problems or batteries that are not "equal" to the others in the bank. That can cause premature failures of the batteries. It would be better to have one bank of 12 2 volt batteries that provide the same capacity of the 36 batteries you have.

Rolls Battery - Our Products

any comments on the deep cycle gels.... or is this deep cycle talk?

does anybody still use wet cell ?

Campesina · Oct 3, 2014

Thank you for the information on the fans. They tend to run 24/7. That's being corrected right now! Sometimes the most obvious thing has to smack you upside the head to get attention!

windeguy · Oct 3, 2014

william webster said:
any comments on the deep cycle gels.... or is this deep cycle talk?

does anybody still use wet cell ?

Virtually everyone in the DR uses wet cell batteries. Like the TROJAN T105. They are still the most cost effective batteries available and doubly so because we are in the DR. Gel batteries are more convenient and are suited for remote locations where maintenance is difficult.

Olly · Oct 3, 2014

Campasina,
This is quite a complex subject but I am glad you took on board the energy analysis our engineer did of your usage. We hope it did not smack you in the head! Fans use about 50 Watts and 7 to 10 about five hundred watts max per hour - thats 12 kWhrs per day. The batteries (12) you are planning on store about 12kWhrs so would run comfortably over night.

We use about 21 to 22 kWhrs per day and switch everything off when we leave the room. It helps.

Olly and the Team

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