solar power

[mickeyrench]

We have a roof with about 80 solar panels [3'x5' x2" thick]. They have been up there for 2 yrs. and 24 batteries that are corroding at the post. Does anyone have any ideas how much wattage they are putting out? And how many years
will it take to break even on something like that? This is a industrial setup .
Thanks for any input.

 

[cadpoint]

Baken-Soda and H2O is one mix that will clean your terminals and be sure to wash that off!

The corrosion is an enviroment aspect, this can be put into a null state with a approved paste.

The model and type of your panels can be referenced via any search engine.
I'd almost dare to say that there will be an output ratio of that size per the type of construction, etc., etc.,

Your DC in Parallel, proof accordingly...

 

[broadgage]

Sounds like quite a large system.
Please take care, some electricians assume that anything isolated from the utility is safe to work on.
In this case it is probable that both the battery bank and the PV array produce potentialy dangerous voltages, even when dissconected from the remainder of the installation.

What are the batteries for? a system this size is often grid tied and uses no battery.
Or is it an off grid system?

Pv modules can be expected to last for decades, batteries have a more limited life, up to 25 years for the very best, but only a few years for most types.

Financial payback for PV installations can vary from a few years, to never, it really does vary that much depending on insolation levels, present and future price of grid power, interest rates, maintenance costs, and assumed life of the equipment.

 

[mickeyrench]

I don't know what the batteries are for , I always though that the batteries stored the electricity till needed and went through a inverter to make ac. I am trying to find out how the system works. The little i know about pv is that they are not advanced enough to be cost effected as far as a timely pay back. I don't know what kind of dc a panel produces, what voltage or it's wattage.
Thanks again

 

[broadgage]

I don't know what the batteries are for , I always though that the batteries stored the electricity till needed and went through a inverter to make ac. I am trying to find out how the system works. The little i know about pv is that they are not advanced enough to be cost effected as far as a timely pay back. I don't know what kind of dc a panel produces, what voltage or it's wattage.
Thanks again

In an off grid system the batteries do indeed store the power until required, since lights etc will be needed when the sun is not shining, also the batteries can supply peak loads in excess of the PV output.
Some systems use DC appliances worked at the battery voltage, but except on very small systems, it is useual to use in inverter to produce line voltage AC.

If a grid connection is available, then it is common not to use batteries. The PV array is connected via special inverter to the grid, any surplus power is backfed into the grid, and any demand in excess of the production is obtained from the grid.
Such systems can be justified on financial grounds, and certainly benifit the enviroment by reducing carbon dioxide emisions.
Grid tied systems do not however protect against failure of the utility supply, they turn off automaticly if the grid fails (in order to protect linemen)

The output of a PV module is typicly at from about 18 volts up to about 40 volts, wattages vary according to size, but often range from about 60 watts up to about 250 watts.

For an off grid system, modules with a nominal voltage of about 18 volts are used to charge 12 volt batteries, with higher voltages being used for higher voltage batteries.
Common battery voltages are 12 volts for small systems, with 24 or 48 volts being used on large systems.
Very large off grid systems use a battery of 96, 108, or 120 volts nominal.

For grid tied systems, a number of PV modules are wired in series to obtain the correct DC input voltage for the grid tie inverter. This is typicly several hundred volts DC.
The inverter output in generaly 120 volts for small systems, with multi voltage 208/240/277 volt inverters being used on larger systems.

 

[iwire]

The output of a PV module is typicly at from about 18 volts up to about 40 volts, wattages vary according to size, but often range from about 60 watts up to about 250 watts.

Just want to mention that often PV modules are wired in series with a goal of reaching about 500 volts DC to send to the inverter.

Point being don't assume the DC output from a solar array is 'low' voltage and harmless.

 

[Jraef]

In an inverter system, the minimum DC peak voltage level is 141% of what you want for the AC output. But it can be anything higher than that and the inverter can trim it down using the PWM pattern. So what PV system designers do size the system to provide at least a minimum usable voltage level when sun conditions are not optimal, then they can get a steady voltage output even at those times. So if they want 208V AC for example, the minimum DC voltage needs to be about 295V. But to maximize the output at full sun, they set up the array of panels to generate as much as 600VDC. So in PV systems, especially larger commercial ones, you must ALWAYS assume the DC voltage level is potentially at 600VDC! In Europe, they have already begun boosting that to 1000VDC, so I would expect that to hit here in the US in short order. Some of the larger commercial inverter manufacturers are already working on 1000VDC input systems.

But with regards to the output power capability of an existing system, there is really no way to tell without knowing more about your panels and the configuration of the array. So as others mentioned, you will have to determine the manufacturer and check on-line to see if data exists.

 

[SolarPro]

All UL-listed PV modules will have a label on the back of the module that specifies the electrical cahracteristics of the product. This is a good place to start reverse engineering the system in the absence of an electrical schematic. Based on the dimensions and the age, these are probably in 175 W to 225W each. The electrical output has a 25 year warranty. You can assume the array is probably doing its job, unless testing shows otherwise.

The array will be wired in series and in parallel. Each series connected string should have a circuit breaker or fuse to provide OCP. Assuming this is built properly, the number of series fuses is a quick way to determine that array wiring. Simply divide the total # of modules by the # of source circuit OCPDs. That will tell you the number of modules connected in series. Each series string should have the same number of modules.

The battery bank wiring will also tell you a lot about the system. Is the nominal battery voltage 12, 24, 36, 48, 60Vdc or other? What are the specifications for the components connected to the batteries. The system probably contains a charge controller and possibly an inverter. You can Google the specifications for these products. In a system like this, the batteries are typically the only part that need regular maintenance. This assumes that the system was properly installed and programmed in the first place.