Solar output during non peak hours

[gburke1]

How much energy, as a percentage of peak output, can one expect to generate during off peak sunlight - with the assumption that you're positioned well at all times?

 

[GotSmart]

Where are you located?  That makes a difference in what is peak hours.

 

[gburke1]

Midwest - I am seeing 4.5 peak hours in my area. Just wondering roughly how much would be generated during non-peak sunlight hours - I.e. if I have a 100w panel how much can I expect out of it in non peak hours? 75%? 50%?

 

[Seraphim]

I've found that to be a difficult question to answer for our system, because we never draw the batteries down much, so they don't ask for a lot amperage recharging. One day I need to run the batteries down, then recharge them...

But as the the sunlight comes up over the horizon and starts to charge what we used overnight - the 210ah battery array being somewhere around 92% - we start getting about 1.5 amps across the shunt to the battery. Perhaps in an hour its up around 5 amps. By noon ( three hours?) the array's at 100% and amperage flow to the battery back under 2 amps - float charging, I assume - which is pretty much where it stays the rest of the day. The 400 watt system should be realistically capable of producing 20ah if needed, but I've never seen it tasked more than 11ah. Panels are flat mounted, we're often in overcast conditions. During the day we recharge two iPads, one iPhone and an old cell phone via a 12v charge station I installed. This does not interfere with charging the battery array in anyway. As long as there is any direct light from the sky at all, the panels seem to produce at least an amp or two.

I expect if we drained the batteries down further, the panels would provide more amperage, as needed - but charging rate is dictated by the controller, if I understand it correctly. We just tax our system that much.

 

[Seraphim]

We just DONT tax our system that much

 

[GotSmart]

This is direct from Renogy.  I hope it helps.  Depending on how cloudy it is depends on how much solar gets through during non peak hours. 

[font='Times New Roman', serif]Peak Hours[/font]

[font='Times New Roman', serif]When sizing a system, it is very important to know the peak sun hours of your state. You can find all of that information for the U.S. here: [/font][font='Times New Roman', serif]http://renogy.com/wp-content/uploads/2013/06/Average-Peak-Sun-hours-by-State.pdf[/font][font='Times New Roman', serif]. You can view peak sun hours as an average, as basing power off the hours of daylight during the day isn’t sufficient. The reason why is because sunlight in the morning and evening will not produce as much radiation as solar during midday. To calculate each states peak hours, the radiation is averaged based on the highs and lows and also other factors such as what is mixed into the atmosphere. It is important to use the peak hours with the wattage of your system to calculate how many watt hours your system produces in a day (You can see example under Off-Grid ->How appliance wattage relates to your panel wattage.)[/font]

 

[highdesertranger]

to be positioned well at all times means you have to track the sun. are you going to do this? without an automatic tracking system(big bucks), you will be doing this all day long everyday. what I mean is you must adjust your panels about every 10 minutes, I don't think that is very practical. when I first started charging with more than 1 little panel I thought I was going to track the sun. well without being there all day adjusting the panels I found that 3 times a day was what I could realistically do, facing east, flat, facing west. then I realized that if I just left them flat all day I got plenty of charge. so that's my 2 cents. leave them flat and if you are not getting enough juice get another panel. highdesertranger

 

[rvpopeye]

X2 HDR

 

[Spaceman Spiff]

How much energy, as a percentage of peak output, can one expect to generate during off peak sunlight - with the assumption that you're positioned well at all times?

The information you are seeking is here:
http://rredc.nrel.gov/solar/old_data/nsrdb/1991-2010/hourly/list_by_state.html

Instructions on how to extract it is here:
http://www.nrel.gov/docs/fy12osti/54824.pdf

It is much easier to use a peak sunlight estimator (like the Renogy one linked to above) or measure it for your location.

-- Spiff

 

[Baloo]

I mounted mine flat, and they work fine all day long, even when it is rainy and overcast. Although I plan to add two more panels (not sure you can ever have enough). The best part about mounting them where they require no adjustments is that you will forget they are even there. They just keep charging the batteries like good little solar panels should...

 

[Optimistic Paranoid]

It would be nice if someone here, with nothing particularly important to do on some cloudless, bright sunny day, could take a series of ammeter readings from their solar panels and post the results here.  Something like:

7:13 am  Sunrise

8 am  x amps

9 am y amps

10 am z amps

etc., right up till sunset.

Regards
John

 

[akrvbob]

There are so many variables this kind of an experiment is very difficult to do.

* First, the time of the year would radically change it, even a few months would throw it off.
* Second, even a little cloud cover would throw it off.
* Finally, and most important, a hungry batter will eat up all the power the controller can give and a nearly full battery won't take hardly anything. A good controller will give the panel output but I'm not sure how accurate they are.

It really needs to be done under controlled conditions.
Boib

 

[highdesertranger]

good idea john. I would like to see a couple more things added to that like temperature and location. of course you have to state what you have for a system. number of panels, ratings, number of batteries, state of charge, etc. well it's getting to be allot of work. never mind. unless someone has nothing better to do. highdesertranger

 

[Optimistic Paranoid]

While there are certainly too many variables to draw any ABSOLUTE conclusions, I still think you could get some useful information.  Pick a clear day, no clouds.  Turn your solar off for a day or two before you run the experiment, so as to get your battery bank down to the 40% to 50% point.

Your HIGHEST figure is your maximum output.  How many hours during the day does that last?  The lower figures you get on either side of that - what percentage of max is that?  Those would both be good things to know.

HDR, good idea about the temperature.  Maybe record both the air (shade) temperature as well as using an IR thermometer to get a panel reading to coincide with each amp reading.

If no one else want's to try it, I guess I will when I hit the road.  I'm hoping to visit Death Valley next winter, and that would be a perfect place to play around with this.

Regards
John

 

[TucsonAZ]

Remember, a 100w panel with a PWM controller is NEVER going to give you more than 80 watts and that's ideal everything. I won't even account for losses from wires, conversion inefficiencies and so on. With 1,400 watts on my roof and some branches shading the panels some I was pulling in a max of 300 watts with a MPPT controller, low clouds and rain that went down to 75 watts. On a good day it would jump around some but less than ideal hours I would be getting in maybe 300 watts with flat panels and full sun.

I would expect you will get at best 75 watts and that will drop as the conditions become less than ideal.

 

[GotSmart]

Remember, a 100w panel with a PWM controller is NEVER going to give you more than 80 watts and that's ideal everything.  I won't even account for losses from wires, conversion inefficiencies and so on.  With 1,400 watts on my roof and some branches shading the panels some I was pulling in a max of 300 watts with a MPPT controller, low clouds and rain that went down to 75 watts.  On a good day it would jump around some but less than ideal hours I would be getting in maybe 300 watts with flat panels and full sun.  

I would expect you will get at best 75 watts and that will drop as the conditions become less than ideal.

That 80% is accounting for conversion inefficiencies.  (PWM) PER HOUR.  

The MPPT is up to 97% efficiency.  

That all depends on how clean your panels are, how old they are, and who made them.  (How they are put together.)

But if someone choses to use sub par wires, connecting methods, and inner parts~~~ The system is only as good as the weakest link.

If you have a 100W panel, and you have 5 peak hours per day, (PWM) then you can count on 500 W per day.  If you have a MPPT, then you can count on 600 W per day. That is on a sunny day.   

You could produce more by eliminating shading, proper tilt and positioning and so on.  Chasing the sun so to speak.  On clear hot days you will produce also more.

Clean your panels regularly of dust, and immediately of leaves.

 

[Optimistic Paranoid]

If you have a 100W panel, and you have 5 peak hours per day, (PWM) then you can count on 500 W per day.  If you have a MPPT, then you can count on 600 W per day. That is on a sunny day.   

Did you mean to say 500 watts, or 500 watt-hours?  There is such a thing as watt-hours, right?

I mean, it drives me crazy that solar panels are rated in watts, but batteries are rated in amp-hours!

A 12 volt battery with 100 amp-hours would hold 1200 watt-hours, of which 50%, or 600 watt-hours would actually be available for use.

Or am I completely misunderstanding this?

Regards
John

 

[Spaceman Spiff]

Did you mean to say 500 watts, or 500 watt-hours?  There is such a thing as watt-hours, right?
Watts is an instantaneous measure, so yes there is a unit called watt-hours (electric companies charge in kilowatt-hours).

I mean, it drives me crazy that solar panels are rated in watts, but batteries are rated in amp-hours!
One reason solar panels are rated in watts because there is too much variability over time and location to give a per hour or per day number (think of how different that number would be for someone in Quartzite in July and someone in Seattle in December).  Batteries are rated in amp-hours because, as a storage device, it tells you how much it holds when full (how many amps it can actually supply).

A 12 volt battery with 100 amp-hours would hold 1200 watt-hours, of which 50%, or 600 watt-hours would actually be available for use.
You are basically correct (your assumption of 12v is a good ballpark number)

Or am I completely misunderstanding this?

Regards
John

One other thing.  MPPT only gives you an advantage during bulk charging.  Both MPPT and PWM throw away (convert to heat) extra amps during absorption and float charging (the batteries determine how many amps they will accept).

-- Spiff

 

[SternWake]

 (the batteries determine how many amps they will accept).

-- Spiff

The batteries determine how many amps they accept at the Voltage allowed by the controller.  Higher electrical pressure(voltage), more amps can flow into battery.

When held at absorption voltage, then amps required to hold the battery there begin to taper.  Once it only requires a small amount of amperage to hold a battery at absorption voltage the battery is full or nearly so.

The exact amount of amps changes among different batteries and changes as they age, and a heavily sulfated battery can do all sorts of strange things regarding the amperage required to reach absorption voltage.

The Key is achieving the correct absorption voltage at the battery terminals, and holding it for long enough to nearly max out the specific gravity of the battery.

Having Fat as possible wiring( and limited length) between charging source/controller and battery can significantly improve battery charging.

If it is too thin  and long, then the controller thinks the battery is at 14.4 but the  battery terminals might only getting 14.15v.  So the battery never gets to the proper absorption voltage and does not stand a chance of fully charging the battery.

That flashing green light will still tell you the battery is full.  It Lies.  Those who believe their batteries are full when the green light full charge indicator is flashing are seriously deluded.  The green light only indicates the controller held absorption voltage as long as it was programmed to do so.  They are all programmed timidly as it is safer  to undercharge and it gets the lawyerly maximum profit stamp of approval, at the expense of battery life.

If your controller is not holding absorption voltage for at least 2 hours after a discharge cycle below 80% state of charge, then the battery is NOT being fully charged, despite that soothing green light.

The deeper the discharge the more important it is to hold absorption voltage for the correct amount of time.

I think any product can be sold and make millions if it has enough flashing green lights and a marketing team to make up new terms.  Humans flock to them like a moth to a flame.

Many batteries were murdered while that flashing green light said all was well.

 

[IGBT]

If no clouds and any sun at all is hitting our 1100 watt system, I get at least 150 watts, even if it is 8am or 5pm.

I need to do the hour tracking thing but I would say 15 to 30% of full output during the non peak hours (peak being about 11am to 4pm here)

A reason I went big, as 15% of 1100 is still a lot of juice.