Solar Panel Angle for Roof installation

[Guest]

Hi,

I'm a builder from New Delhi, India, i recently came to know about, how efficient solar power can be, but i'm very new to this industry, so i need some help from experts, hence i came.

My Question :-

As i'm constructing 1 building of around 3 floors (ground, 1st, 2nd, & 3rd floor), i like to know, is there any average angle (complete year i.e. all 365 days) for solar panel, with which i can get some useful amount of output power from solar panels, so that at that particular angle i can make my building roof, & install solar panels on them, which may help my customer of that building in some amount to reduce there electricity bills.

If yes, then whats the average power output do i get & whats the number of solar panels required for the same.

Home size - 1200 Sq.Ft.

Thanks in Advance
Ashish

[russ]

Hi Ashish - Welcome to Solar Panel Talk!

It will all depend on the daily power consumption - what will that be in your best estimation?

[Wy_White_Wolf]

General answer is the same angle as your latitude. There may be some seasonal factors that would change that slightly but generally the same as your latidude.

WWW

[inetdog]

General answer is the same angle as your latitude. There may be some seasonal factors that would change that slightly but generally the same as your latidude.

WWW

By going to a site like PVWatts you can plug in different angles and see the results month by month.
For off grid you usually try to optimize for winter. For grid tie you usually go for highest annual total unless the rate changes from season to season or you have A/C usage that pushes you into a high rate tier in the summer. In those cases you may want to optimize for summer production.

For a roof installation it usually does not pay to put in the additional hardware to make the angle adjustable during the year. (Using anything but the roof angle itself for roof mounted increases the wind load and complicates control of shading.)

[Guest]

Hi All,

Thanks for Reply, now i got some more questions like :-

1. Effects of Wind Load, what it means, & how much it can effect.

2. Effects of complicates control of shading, what it means, & how much it can effect.

3. Effects of Solar Panel Height, i.e. if i put 1 solar panel in ground floor, & 1 solar panel at roof, is there any difference in output power of ground solar panel & roof solar panel ???, (both places have complete solar light availability).

4. whats the average output of 1 sq.ft. solar panel & how much time it needs solar light i.e. hours, to generate that output.

5. Is there any difference in output power, if i put 6 solar panel (smaller - 1 sq.ft. each) in line or if i put 1 solar panel of 6 sq.ft. (bigger).

6. Is solar panel is Transparent i.e. is solar panel passes some sunlight through them or there's complete shade behind solar panels.

The basic requirement of my building would be, to run

1 refrigerator (200W) for 24 hrs. daily (1 in each floor),
3 lights (40W) for avg. 5 hrs. daily (in each floor),
3 fans (60-100W) for avg. 5 hrs. daily (in each floor),
1 TV's (200W) for avg. 3 hrs. daily (1 in each floor),

Thanks in Advance
Ashish

[inetdog]

Hi All,

Thanks for Reply, now i got some more questions like :-

1. Effects of Wind Load, what it means, & how much it can effect.
Wind blowing over the array can exert both side forces and uplift that must be counteracted by the mounting hardware and transferred to roof members that can take the load. Usually not a problem when the roof design takes this into consideration.

2. Effects of complicates control of shading, what it means, & how much it can effect.
Take the example of a flat roof: I can put panels side by side in a square array with no problem as long as they are flat. If I tip each row of panels to 30 degrees, I have to add space between rows to prevent the top of one row from shading the bottom of the next. The amount of light hitting the area of the roof will be a constant upper limit, but the efficiency of the panels in accepting it will be greater if they are perpendicular to the incoming light rays.

3. Effects of Solar Panel Height, i.e. if i put 1 solar panel in ground floor, & 1 solar panel at roof, is there any difference in output power of ground solar panel & roof solar panel ???, (both places have complete solar light availability).
NO.

4. whats the average output of 1 sq.ft. solar panel & how much time it needs solar light i.e. hours, to generate that output.
The insolation (energy from the sun) is about 1000watts per square meter at sea level. The area is measured perpendicular to the incoming light. Efficiency of solar panels in converting that energy to electricity can range from as low as 10% to as high as 20% in ideal situations with expensive cell design.
Most crystalline silicon cells are within a percent or two in initial efficiency.

5. Is there any difference in output power, if i put 6 solar panel (smaller - 1 sq.ft. each) in line or if i put 1 solar panel of 6 sq.ft. (bigger).
No, except for the area lost to mounting hardware and interconnections. If you are not fighting a limit of available area the output will be the same but the cost per watt of the smaller panels will be much higher.

6. Is solar panel is Transparent i.e. is solar panel passes some sunlight through them or there's complete shade behind solar panels.
Complete shade for commercial panels, since there will be a metallic coating on the back side of the silicon to serve as an electrode. There are some lab experiments with transparent cells or films, but they are not currently practical. The mounting (backing) is also opaque.

The basic requirement of my building would be, to run

1 refrigerator (200W) for 24 hrs. daily (1 in each floor),
3 lights (40W) for avg. 5 hrs. daily (in each floor),
3 fans (60-100W) for avg. 5 hrs. daily (in each floor),
1 TV's (200W) for avg. 3 hrs. daily (1 in each floor),

Thanks in Advance
Ashish

Answers inserted inline above

[brokejame]

Power Consumption

I think first you need to check basic requirements of power and then after taking some expert's advices, you can definitely do it.

[Guest]

Answers inserted inline above

Hi,

Thanks a lot for answering my queries so quickly, i like to know, is there any other precaution i need to consider, before implementing the solar panels, & also can u let me know, how much approx. size of solar panel is required & cost it may cause, as per below requirement.

The basic requirement of my building would be, to run

1 refrigerator (200W) for 24 hrs. daily (1 in each floor),
3 lights (40W) for avg. 5 hrs. daily (in each floor),
3 fans (60-100W) for avg. 5 hrs. daily (in each floor),
1 TV's (200W) for avg. 3 hrs. daily (1 in each floor),

& are those panel are enough capable to supply above requirement, or how much output they can deliver in around 5 hours of solar light daily.

Thanks in Advance
Ashish

[inetdog]

Hi,

Thanks a lot for answering my queries so quickly, i like to know, is there any other precaution i need to consider, before implementing the solar panels, & also can u let me know, how much approx. size of solar panel is required & cost it may cause, as per below requirement.

The basic requirement of my building would be, to run

1 refrigerator (200W) for 24 hrs. daily (1 in each floor),
3 lights (40W) for avg. 5 hrs. daily (in each floor),
3 fans (60-100W) for avg. 5 hrs. daily (in each floor),
1 TV's (200W) for avg. 3 hrs. daily (1 in each floor),

& are those panel are enough capable to supply above requirement, or how much output they can deliver in around 5 hours of solar light daily.

Thanks in Advance
Ashish

First, let's get the biggest load (the refrigerators) calculated correctly. Is the 200watts the running wattage, with the motor only turning on as controlled by the thermostat or is this already the average power over 24 hours?
Second, if you can arrange to run the refrigerators mostly during the time the panels are producing, staying cold the rest of the time because they are well insulated, you can get by with a smaller battery bank even though the panel size requirement will be the same.
Third, using fluorescent or LED lights can cut the lighting power requirement be a factor or 3 or more.
Fourth, I did not find any description of the size or number of panels that you are talking about.

As a rough estimate, not factoring in changes in load as described above, you would need ~25kwh of energy for all three floors (if my math is correct), which would require
5kw worth of panels, with an area of roughly 35 square meters. And that is assuming that you mean 5 hours equivalent of full noon sun ("solar hours" or hours of insolation) rather than 5 hours of sun hitting the panels.

[Naptown]

Actually BIPV panels are mostly translucent to allow light to pass through. However this is at the expense of efficiency (watts per sq meter harvested)

[jwax]

You would do well to talk with several installers in your area, and have them answer your questions besides researching forums like this one.
John

[russ]

You would do well to talk with several installers in your area, and have them answer your questions besides researching forums like this one.
John

jwax - He is posting from India - make your comments relevant please.

[Guest]

General answer is the same angle as your latitude. There may be some seasonal factors that would change that slightly but generally the same as your latidude.

WWW

Hi All,

Just 1 more question, how much difference it makes in Output Power, if solar panel are installed complete horizontally (flat to surface) & at an latitude angle of the location, with same amount of sunlight, is there any major difference ???

Thanks in Advance
Ashish

[russ]

Try playing with the PV Watts calculator - you can change the orientation however you want. Just pick an address or location that the program knows and run -

[Naptown]

Hi All,

Just 1 more question, how much difference it makes in Output Power, if solar panel are installed complete horizontally (flat to surface) & at an latitude angle of the location, with same amount of sunlight, is there any major difference ???

Thanks in Advance
Ashish

depends on how far you are from the equator.