New System Installed But Somewhat Disappointed?

[silversaver]

add few panels. simple solution without needed engineer calculation.

[bcroe]

A virtual tracker is not as efficient a use of your panels as a mechanical tracker, but it accomplishes the same thing for less money and more reliability.

--mapmaker

For most locations, I don't understand how off south panels can be as efficient as south facing panels. If you're going to add panels to make up the diff., I'd think adding them in the most advantageous orientation to the greatest extent possible would be better. What am I missing ?[/QUOTE]

The additional panels (not facing south) will not require a larger inverter or AC wiring, since
they extend the sun day instead of just boosting the peak. With more time spread output,
some clouds near noon won't wipe out the whole day. And when clouds & overcast come,
the extra panels help support output no matter what direction they face (compared to a
tracker). Bruce Roe

[inetdog]

For most locations, I don't understand how off south panels can be as efficient as south facing panels. If you're going to add panels to make up the diff., I'd think adding them in the most advantageous orientation to the greatest extent possible would be better. What am I missing ?

The additional panels (not facing south) will not require a larger inverter or AC wiring, since
they extend the sun day instead of just boosting the peak. With more time spread output,
some clouds near noon won't wipe out the whole day. And when clouds & overcast come,
the extra panels help support output no matter what direction they face. Bruce Roe[/QUOTE]
What Bruce is talking about is not substituting E or W facing panels for S facing panels. He is talking about adding in E or W facing panels or both to supplement the limited number (maybe zero) that you can fit in with optimal S orientation.

If you look at the production curve over the day, the additional panels in either E or W orientation will produce less total power (see PVWatts for exact numbers) but they will add in power at a time when your S facing panels are not producing much and so will not require a larger inverter.
A balance of just E and W facing panels can give you a large number of sun hours in total, even though the individual panels will not produce as much as they would with S orientation.
The decision depends in part on your inverter cost versus your panel cost.

[mapmaker]

A balance of just E and W facing panels can give you a large number of sun hours in total, even though the individual panels will not produce as much as they would with S orientation.
The decision depends in part on your inverter cost versus your panel cost.

And some other parts of the decision:

The OP is grid-tied, so depending on the rate structure (tariffs, TOU, etc) it may, or may not, be advantageous to extend the sun hours rather than add south-facing panels.

For those of us who are off-grid, the extended sun hours is usually advantageous... minimize the daily number of hours that the batteries have to carry the load. Some folks put their extra panels facing west to get extra power for air conditioning in the late afternoon.

Trackers (both virtual and mechanical), give the most bang for the buck when the sun moves around a lot... for those of us in the north (where the winter sun rises and sets in the south), there isn't as much to gain trying to track the sun in the winter. In the northern summers, the sun rises and sets on the north side of south-facing panels... tracking can be very beneficial then.

--mapmaker

PS... inetdog, can you fix the [quote problems in the preceding few posts?

[bcroe]

And don't forget "THE CLOUDS". Each situation will vary, but clouds & overcast are
quite common here. The extra panels keep my inverters around 50% when the sky
is overcast, and near max for lesser clouding. I never have to write off a day as
insignificant production. Bruce Roe

[SunEagle]

And don't forget "THE CLOUDS". Each situation will vary, but clouds & overcast are
quite common here. The extra panels keep my inverters around 50% when the sky
is overcast, and near max for lesser clouding. I never have to write off a day as
insignificant production. Bruce Roe

I would say your system could be considered a "fixed" tracking. The panels are fixed and the sun tracks across the sky.

[Sunking]

I know it is after the fact but i was just hoping that they knew what they were doing

James they did know what they were doing, they knew full well your system would never perform at optimum. They just told you what you wanted to hear. The responsibility is yours to find out the truth, and you will never obtain that asking the company sales team. It is not their job to educate and protect you. Their only obligation is to sell you something and they succeeded at doing their job.

[silversaver]

I don't think the installer has done anything wrong. Just look at the sat image. If that is my house, I'll install the panels at the same spots, period.

The center flat roof space is too small and I don't like to see the panels from the street. I think it is the best possible design the installer have done. The only thing I'm not sure if the sizing is properly, and that is really optional base on installer and owner.

[Naptown]

James they did know what they were doing, they knew full well your system would never perform at optimum. They just told you what you wanted to hear. The responsibility is yours to find out the truth, and you will never obtain that asking the company sales team. It is not their job to educate and protect you. Their only obligation is to sell you something and they succeeded at doing their job.

I do not think this way.
For grid tie it is the overall annual production most( at least I ) shoot for. Monthly production will vary obviously and a prediction is based on historical weather patterns which will vary year to year but the annual over several years is what counts.
A couple of things
A system will rarely output if ever it's nameplate rating.
Monthly production and more so daily will vary to a large extent.
Run a PV watts calculation with the proper derate factor to see if you are on or off track

[Ian S]

I do not think this way.
For grid tie it is the overall annual production most( at least I ) shoot for. Monthly production will vary obviously and a prediction is based on historical weather patterns which will vary year to year but the annual over several years is what counts.
A couple of things
A system will rarely output if ever it's nameplate rating.
Monthly production and more so daily will vary to a large extent.
Run a PV watts calculation with the proper derate factor to see if you are on or off track

Agreed, and I would just add that in order to output nameplate rating, all panels would have to be oriented the same and even then it's going to be very infrequent. As soon as you have multiple arrays facing say east and west, then I doubt you could ever expect to see nameplate power. That said, a combination of east-west arrays, while the peak power will be less, the power curve gets broadened so the production is not as deficient as one might expect from the lower maximum power. I agree with silversaver: the setup is probably optimum for the characteristics of the home. I don't see any evidence to suggest that the installer was cutting corners.

[bcroe]

Agreed, and I would just add that in order to output nameplate rating, all panels would have to be oriented the same and even then it's going to be very infrequent. As soon as you have multiple arrays facing say east and west, then I doubt you could ever expect to see nameplate power. That said, a combination of east-west arrays, while the peak power will be less, the power curve gets broadened so the production is not as deficient as one might expect from the lower maximum power. I agree with silversaver: the setup is probably optimum for the characteristics of the home. I don't see any evidence to suggest that the installer was cutting corners.

I'm not sure what your "nameplate rating" is. To me its the AC output capability of the inverter(s).
The panels are then chosen to keep those inverters working hard for sufficient hours. Obviously
the AC output can NEVER equal the panel DC rating, with wiring & inverter losses; don't see a
reason to refer to DC as the rating. Bruce Roe

[J.P.M.]

xxx

[russ]

xxx

That was concise!

[J.P.M.]

Several things on this thread, perhaps not concise:

1.) As long as the sun is above the horizon, any (panel) addition to a system, added in any orientation, will increase the instantaneous system output, full sun, or complete cloud cover, at any and all times of the day when the sun is up. For example, east facing panels added to a south facing array will add to solar noon output, just not as much as the south facing panels.

2.) Safety first: Any system changes must trigger a system review for impacts on the entire system and all components. For starters, to state adding non south panels will not require a larger inverter because it will not increase peak output is not correct. Peak output will increase. Maybe not much, maybe a lot. Probably somewhere in between, but it will go up.

3.) Bruce: Most commonly, "Nameplate Rating" refers to the S.T.C. rating of the panels used. Sometimes it is considered the S.T.C. rating of each panel times the # of panels to give total system size. Referring to "Nameplate Rating " by inverter size is uncommon to my experience, except perhaps in the subcontext of talking about inverters. Most of the time, a residential solar electric generating system is sized with some idea of the load to be met and the resource available to meet that load - the irradiance. The panels, their characteristics and number are then chosen to meet that duty. The inverter(s) that works best for the duty and the panels is decided after that, not before. The panels have priority in most design endeavors, not the other way around.

4.) On grid and off grid systems are different animals with different outputs, requirements and quirks. Since the OP has a grid system, I'd suspect most comments would be directed to grid systems.

5.) One goal of any solar design is usually most bang for the buck. This particular goal is most often best met when most of an array faces generally south to the greatest extent possible.

Other design constraints, requirements and priorities may likely require off south, split or unequal array sizes and orientations. Making the best choices between all/nothing is one way to think of the design process.

However, to think that east-west arrays or splitting arrays to off south orientation will be more cost effective simply and solely because it will make the daily production peak(s) a bit lower and also increase output some at other times of the day (thus, flattening the curve and putting "more area under the curve") is, in almost all cases, incorrect. Such orientations may be required by the design constraints, but the bottom line is, in most situations, it will cost more for less output, and thus not the first choice. Put another way, given any array or panel, south facing will, in almost all cases, produce more output per area than non south orientations.

6.) As stated elsewhere in this thread, S.T.C. ("Nameplate") output will be seen infrequently, if ever.

7.) The vendor's primary reason for existence is to make money by putting a solar product on your property. Many vendors are knowledgeable. Many are not. Some are unethical. A few are crooks. I'd guess the lousy ones are more of a PITA and more costly to the good vendors than they are to customers.

Regardless of their ethics or knowledgeability, increasing the customer's knowledge base is not part of their job description. For anyone to rely on someone with skin in the game for accurate, unbiased, always truthful information is foolish.

Caveat Emptor.

Part of the customer's responsibility in all this is to be as knowledgeable as possible about the product being considered and be aware of the consequences, financial and otherwise, of the choices made consistent with long and short term goals.

IMO, most folks' version of being knowledgeable is usually limited to being angry with the POCO for a bloated electric bill (mostly of the users' own doing), and throwing money at the problem by using the (usually) most expensive and thus least cost effective way to reduce an electric bill.

8.) OP has taken some hits here that IMO, could have been softer and gotten the same message across. But, the question (probably rhetorical) stays with me, if the OP had known, by heads' up objective, hard headed information gathering, some of what people knowledgeable with respect to solar energy know, would the same choices have been made ?

[J.P.M.]

That was concise!

Screwed up. See below.