can i use a solar panel without using battery

[TnAndy]

OK....you have 5,000w of PV. Let's assume, for the sake of argument, they produce 5kw from 7am to 5pm as you have perfect trackers ( I have 3 arrays on trackers, and can tell you it helps, but they ain't perfect )

Now, as Russ said: What ARE your electrical needs ? 1000w ? 2000w ? 4000w ?

Say it's 3657w. When do you turn it on ? 6:59 am ? 7:02 am ? ( remember, the sun is rising later as we go into winter ). How do you deal with a passing cloud.....you gonna keep one eye on your load and the other eye on the sky ?

And let's say a high, Cirrus type cloud cover moves in during the day....does your production fall below 3657w ( or whatever load you have on it at the time ? ).

And let's say you actually DO have 5,000w of PV production.....are you gonna try to USE the whole thing right up to the last watt of PV production, risking browning out loads ? Or are you gonna stay conservative, stay back at 3,000 or so watts ? If you stay conservative, aren't you wasting the other 2,000 watts when it actually COULD produce them ? ( because it won't if the load isn't there )

See, this whole thing is merely an academic exercise.....you can't operate a PV system in a PRACTICAL manner without a decent battery bank, or connected to the grid ( using it as your battery bank ) unless you're willing to WAY oversize the PV amount, to the point of being silly.

[russ]

One of the basics of solar PV is to know how many watts you are really consuming or planning to consume. Name plates on equipment don't mean much as they are a maximum number and no one wants to spend (waste) the money to be able to supply the maximum.

One way is a Kill A Watt or similar - you just plug it into the power supply to the TV, fridge or whatever.

What I have done is use cheap commercial power meters and wire them into the system at certain points plus I have one with plugs on it so I can place it wherever I want. I try to monitor things for days or a week at a minimum. Cost of the meters - about 20$ US each for monophase.

[MooChaqa]

Hi guys,

I'm totally new to this although might be researching a similar situation which may answer the ops question.

Isn't this what a 'shunt' does?

Scenario: Your battery is full. The sun is shining brightly on the panels. The power being produced at that point by the panels is being 'shunted?' directly to any load you may be using. Completely avoiding any battery charge or discharge.

Disclaimer: The load would have to be less that equal to what the panel was generating at that time.

Disclaimer 2: I'm a total newb and this is my 2nd post after my introduction. Be gentle

[russ]

Until you define your loads - how many watts for how many hours it is just whistling in the wind.

[themaxx69]

I did not say that. That is only true assuming the batteries are fully charged.

Here is some math fun. Current out from the controller is 60 amps, batteries are charging with 30 amps. What is going on?

Not sure, besides me losing some more brain cells. And, yes, assuming batteries are full, or damn near. The whole point is to maximize battery life....by not using it, until absolutely necessary.

Another great scenario which fits me is, I get a 5000 watt PV system. I plan on using 100% of my electrical needs during which time those panels can produce that power here in AZ using a sun tracking rig. And I want a battery to provide emergency power at night in case I wake up in the middle of the night and have to puke my guts out cause I drank too much and ate too much mexican food and I need some light and to charge my phone because I forgot to charge it and need to call and order a late night pizza delivery. Do I need a HUGH battery bank for the power which will be used during the time the panels can fully provide that power or just a small battery for when the panels can't produce any power.

I think that's pretty clear on do I need batteries.

[john p]

Mike you just put your bell curve there because its accurate and neat. mine is.. nevermind.

[Mike90250]

5-13Chart.jpgHere is an attached "bell curve" of a 4.5 Kw west facing array

[Sunking]

ALRIGHT! That's what I was looking for....I think. So as long as the demanded load doesn't exceed what the panels can provide, the batteries power isn't used? And then it doesn't affect the batteries at all. So for ****s and giggles

I did not say that. That is only true assuming the batteries are fully charged.

Here is some math fun. Current out from the controller is 60 amps, batteries are charging with 30 amps. What is going on?

[themaxx69]

Or should I just say screw it and try to find a used HUP Solar-One battery.

[themaxx69]

It is not complicated at all. If the panels generate equal or more power than is demanded it goes to the load. If not the batteries have to make up the shortage. It is simple math where both sides of the equation have to be equal and true.

ALRIGHT! That's what I was looking for....I think. So as long as the demanded load doesn't exceed what the panels can provide, the batteries power isn't used? And then it doesn't affect the batteries at all. So for ****s and giggles, If you never exceeded the panels production, would the battery last forever or more than 10 years? The highest Trojan's graph goes is 5000 cycles I think.

[Sunking]

It is not complicated at all. If the panels generate equal or more power than is demanded it goes to the load. If not the batteries have to make up the shortage. It is simple math where both sides of the equation have to be equal and true.

[themaxx69]

Then, when we have excess power the house is NOT using, the meter turns backwards as we put it back on the grid. In off grid situations, if the battery was fully charged, and you weren't using the full power the panels produce, power simply wouldn't BE produced.....the panels just sit there at idle until a load occurs.

That's the WHY of what these other guys are trying to tell you when they say "It won't work"......because it won't work.

Ok, I REALLY appreciate the info, but no one is answering the question I asked twice now, I think.

The quote above looks like half an answer, but not fully.

Again, I mainly want to know how the system works beginning with the electricity produced at the panel and ending with whatever is using it. And all this has to do with how the battery life is affected.

I thought I laid it out pretty easy and precise.

If you have fully charged batteries and say you have 1000 watts of panels capable of producing that, meaning the sun is directly over head and at maximum strength and you start using 5 100 watt light bulbs,which equals 500 watts, does the power come from the batteries or pretty much straight from the panels? In that scenario, which I think for me would be typical of most daylight hours, would the power usage affect battery life? Is the power to lights coming from the batteries stored energy then immediately recharged or what. Or is the power coming from the panel and kind of passing right through the battery to the device using it. And again I'm talking about a device requiring LESS power than the array is capable of producing at that given time.

This is what I would like cleared up, seems such an easy question. I honestly think this is a real basic, fundamental question because battery cost is MUCH MUCH more expensive if you factor in average life spans. Common sense tells me, "basically" the electricity would flow straight through the system, in this case.

I really would just like a straight answer or at least tell me I'm dumb and point me in the right direction of where to find the answer if it's somehow super complicated to explain.

[john p]

panel output verses time of day

Here is an attached "bell curve" of an imaginary 120w panel and its aprox outputs over the daylight hours.. Obviously it wont be exact for every location ,its just to give an idea even though there is "daylight" its not not enough to produce much power except for a comparatavly short period of the day

[Naptown]

Why would you burn 7 light bulbs in the day time ?

What you haven't picked up on is the batteries, or the grid, level out the power supply.

Panels don't produce a nice, even steady flow of electricity like a generator does ( heck, even they bog down when you load them up )....a fixed panel produces a little at sunrise, then the most around noon, then tapers off again in the afternoon as the sun angle falls away from perpendicular to the face of the panel. Also, weather conditions GREATLY affect the output. Cloud moves over, output falls WAY off.

In the case of incandescent light bulbs, say a cloud moves overhead.....they would simply dim. But what happens if you're using a motor ? Brown out....or your system tries it's best to pull it out of the small battery bank.

In a IDEAL world, your attempt "might" work....if you could sit there all day and match your power use to the output of the panels every given second ( or maybe split second )....but I know I sure don't have time to do that......so I pull my excess needs ( wife flips on the oven, or the dryer, or a hair dryer, or anyone of a dozen other things ) from the grid, if the grid is up, and from my batteries ( on limited circuits.....she's just flat out of luck with the oven or the dryer....ahahahaaa ) if the grid is down.

Then, when we have excess power the house is NOT using, the meter turns backwards as we put it back on the grid. In off grid situations, if the battery was fully charged, and you weren't using the full power the panels produce, power simply wouldn't BE produced.....the panels just sit there at idle until a load occurs.

That's the WHY of what these other guys are trying to tell you when they say "It won't work"......because it won't work.

Thank you for that intelligent and well worded answer

[TnAndy]

So, again if you have fully charged batteries and say you have 1000 watts of panels capable of producing that and you start using 7 100 watt light bulbs, does the power come from the batteries or pretty much straight from the panels? In that scenario, which I think for me would be typical of most daylight hours, would the power usage affect battery life?

Why would you burn 7 light bulbs in the day time ?

What you haven't picked up on is the batteries, or the grid, level out the power supply.

Panels don't produce a nice, even steady flow of electricity like a generator does ( heck, even they bog down when you load them up )....a fixed panel produces a little at sunrise, then the most around noon, then tapers off again in the afternoon as the sun angle falls away from perpendicular to the face of the panel. Also, weather conditions GREATLY affect the output. Cloud moves over, output falls WAY off.

In the case of incandescent light bulbs, say a cloud moves overhead.....they would simply dim. But what happens if you're using a motor ? Brown out....or your system tries it's best to pull it out of the small battery bank.

In a IDEAL world, your attempt "might" work....if you could sit there all day and match your power use to the output of the panels every given second ( or maybe split second )....but I know I sure don't have time to do that......so I pull my excess needs ( wife flips on the oven, or the dryer, or a hair dryer, or anyone of a dozen other things ) from the grid, if the grid is up, and from my batteries ( on limited circuits.....she's just flat out of luck with the oven or the dryer....ahahahaaa ) if the grid is down.

Then, when we have excess power the house is NOT using, the meter turns backwards as we put it back on the grid. In off grid situations, if the battery was fully charged, and you weren't using the full power the panels produce, power simply wouldn't BE produced.....the panels just sit there at idle until a load occurs.

That's the WHY of what these other guys are trying to tell you when they say "It won't work"......because it won't work.