Calculating how much AC Energy can pv panels of particular area generate?

[bernard]

I am currently using PVWatts online calculator to calculate the AC Energy output.
I was wondering if PVWatts can be used to calculate how much AC Energy will particular surface(pv panel) output?
By default PVWatts uses 4 kW DC rating system. In the help pages, there stands that 4kW corresponds to a PV array area of approximately 35 m2 (377 ft2). Based on this ratio, can I use the initial area of my surface, then convert it to kW, and do the calculation? In this way I would exactly know how much AC Energy could my specific surface (say roof top) generate ? Example:
Let's say I have an area of 200 ft2 I would like to populate (it does not matter if there are no pv panels which could exactly populate that area. So this is only an assumption):

(4kW * 200 ft2)/377 ft2 = 2.12kW

So for initial area of 200 ft2, I should use 2.12kW as DC rating for PVWatts calculator.
Is this approach not correct?

Just to mention that I am currently not interested in shading. I just want to know how much AC Energy can pv panels/arrays of certain area generate.

Thank you.

[sensij]

I am currently using PVWatts online calculator to calculate the AC Energy output.
I was wondering if PVWatts can be used to calculate how much AC Energy will particular surface(pv panel) output?
By default PVWatts uses 4 kW DC rating system. In the help pages, there stands that 4kW corresponds to a PV array area of approximately 35 m2 (377 ft2). Based on this ratio, can I use the initial area of my surface, then convert it to kW, and do the calculation? In this way I would exactly know how much AC Energy could my specific surface (say roof top) generate ? Example:
Let's say I have an area of 200 ft2 I would like to populate (it does not matter if there are no pv panels which could exactly populate that area. So this is only an assumption):

(4kW * 200 ft2)/377 ft2 = 2.12kW

So for initial area of 200 ft2, I should use 2.12kW as DC rating for PVWatts calculator.
Is this approach not correct?

Just to mention that I am currently not interested in shading. I just want to know how much AC Energy can pv panels/arrays of certain area generate.

Thank you.

Your calculation will get you in the ballpark. There are some 2nd order effects in efficiency that may not scale exactly, but that may not matter for your purposes. You might not be able to find panels that will fit any arbitrary area, so that would also be a constraint in turning the theoretical number into an actual system. For the next level of accuracy, there are some panels that are more area efficient than others, PVWatts acknowledges this with their module type selection. Other modelling tools are available that will do a better job of accounting for the performance of a particular type of module. System Advisor Model, released by NREL, is one.

[J.P.M.]

I am currently using PVWatts online calculator to calculate the AC Energy output.
I was wondering if PVWatts can be used to calculate how much AC Energy will particular surface(pv panel) output?
By default PVWatts uses 4 kW DC rating system. In the help pages, there stands that 4kW corresponds to a PV array area of approximately 35 m2 (377 ft2). Based on this ratio, can I use the initial area of my surface, then convert it to kW, and do the calculation? In this way I would exactly know how much AC Energy could my specific surface (say roof top) generate ? Example:
Let's say I have an area of 200 ft2 I would like to populate (it does not matter if there are no pv panels which could exactly populate that area. So this is only an assumption):

(4kW * 200 ft2)/377 ft2 = 2.12kW

So for initial area of 200 ft2, I should use 2.12kW as DC rating for PVWatts calculator.
Is this approach not correct?

Just to mention that I am currently not interested in shading. I just want to know how much AC Energy can pv panels/arrays of certain area generate.

Thank you.

Before going further, note that PVWatts is a tool for estimating long term performance of a general system, not a performance predictor, as explained in the help screens, and not specific enough for individual products from either the same or different mfgs.

To use PVWatts, once you have determined (estimated) what your annual load will be and what your goals are (essential steps before any solar estimating), PVWatts will put you in the ballpark for a size estimate to meet the electrical load offset goal you set.

You can vary the array default size, either in a general way, from 4 kW to say, 5kW, or whatever size, and note the output.

OR, if you have a particular panel in mind, say LG 300, and if your annual load is, say, 12,000 kWh. Start with a, say, (12 X 300) = 3,600 W = 3.6 kW system, run PVWatts, and note the output, which will be in kWh/month with year totals at the bottom. Then, rerun PVWatts, increasing/decreasing the # of panels until the estimated annual output is close to your load offset goal.

Divide the annual output by 12 and that will be an estimate of 1 panel's annual output, rough SWAG.

Note the output will be in kWh/mo., and totaled to kWh/yr. Not kW.

Also note that most 4 kW arrays have an area something like, very approximately, 25 m^2 (~269 ft^2).

If you are limited as to available area for panel placement, divide that limited area by the particular panel(s) you may have in mind or use another SWAG of about 18.5 ft^2 per panel (~1.7 m^2) as a common area for a lot of commonly used panels to get a SWAG for the # of panels that will fit in your space. Don't forget fire set backs and other restrictions. If the resulting system does not meet your annual offset goal, either use conservation to reduce the annual load and the offset ( the cheap way), or use Sunpower panels that have a greater output/area allowing a larger (electrical) size array for a lot more money (the expensive way).

To estimate Sunpower paneled systems, use the "premium panel" option in PVWatts.

So, I guess the answer to your 2d question is a cautious yes - area ratios are possible ways to adjust sizes in a SWAG fashion, but with the STRONG caution to check your assumed area of 377 ft^2, and notwithstanding my probable misunderstanding of your question.

I'm sort of wondering what your looking for. If you are looking for how much power in Watts an individual panel will produce over an hour (kWh), the hourly output option in PVWatts can be of some use, but given your questions, I sort of wonder if you need more education before you attack that task. I think the short answer to your 1st question is maybe, but I'm not sure what good it may be, or it's accuracy.

If you are looking for the max. approximate instantaneous power a particular individual panel can produce amount (in Watts), the place to start is usually the panel model # itself which often has the "S.T.C." Wattage as part of the model # (for ex.: An LG 300 panel has a RATED max. output of 300 Watts under standard test conditions).

[bernard]

This website has a wonderful support.
Thank you for the replies both Sensij and J.P.M.

[J.P.M.]

This website has a wonderful support.
Thank you for the replies both Sensij and J.P.M.

For my part, you're welcome. I hope you find some benefit from my input.

[bernard]

I will definitively do J.P.M. Thank you once again.