May 8, 20224 yr Hello.. I want to install 14 panels however I only have space for 8 in the N direction and 3 in the NE and 3 in the E. My question is those that are placed in the NE and E direction.. Typically what time would PV production start and for how long?
May 8, 20224 yr Assuming 35 degree roof angle and Cape Town: Yield on 1 July Yield on 1 Jan: Essentially, in summer not much difference. in winter the East facing panels (red line) do very poorly. The actual numbers change a lot with different roof angles and locations, but you get the general idea. If you supply your location and angle I can rerun the graphs.
May 8, 20224 yr Author Thank you for the response, so I assume the black is North and the dark red is NE? Attached my location. When u say 35 deg roof angle you mean the roof or the actual angle of the panels when installed? Also assume JHB please
May 8, 20224 yr 11 minutes ago, Solarcrazy said: When u say 35 deg roof angle you mean the roof or the actual angle of the panels when installed The actual panel inclination is needed. 12 minutes ago, Solarcrazy said: I assume the black is North and the dark red is NE The legend is at the top: 0/35 means North, panel inclination 35 degrees, 45 means NE, 90 means East
May 8, 20224 yr @Solarcrazy You can use Solcast to give you a fair forecast for three days in advance with their free service https://solcast.com/ All documentation is available on their site. https://articles.solcast.com.au/en/articles/2979582-getting-started-with-rooftop-pv-sites Here is the past three days actuals and the next three days forecast that they provide for my specific location input. And this is for Johannesburg.
May 8, 20224 yr 7 hours ago, Solarcrazy said: Hello.. I want to install 14 panels however I only have space for 8 in the N direction and 3 in the NE and 3 in the E. My question is those that are placed in the NE and E direction.. Typically what time would PV production start and for how long? Well it would depend on where you are. I'm in Randburg with 6 panels facing N and 6 facing E. I start getting PV about 7:00 this time of year, something useful just after 7:30, peak PV power about 11:30, and as late as 14:30 I am getting about 30% of PV from the E facing array. Edited May 8, 20224 yr by Bobster sppeling
May 8, 20224 yr Author 6 hours ago, zsde said: @Solarcrazy You can use Solcast to give you a fair forecast for three days in advance with their free service https://solcast.com/ All documentation is available on their site. https://articles.solcast.com.au/en/articles/2979582-getting-started-with-rooftop-pv-sites Here is the past three days actuals and the next three days forecast that they provide for my specific location input. And this is for Johannesburg. Thank you.. Looking into it 😁
May 14, 20224 yr I've seen panels on some of the buildings at Route 21 Business Park in Irene , Centurion mounted on all 4 sides of their roofs ( buildings with 4 sided roofs E,W,N,S). Just to add that these buildings have no trees or other buildings blocking the roofs and are on a hillside with tons of sunshine the whole day.
May 16, 20224 yr The research I have done shows not significant difference in daily production (give or take up to 15%) irrespective of facing and inclination through the arc east, north to west provided no shading. Certainly east will provide power sooner with the morning sun and likewise west in the afternoon but if the battery is right sized, it will matter less. My panels are just off north and in full sun all day (roof inclination 25 deg). I'm in East London and typically see production peaking from around 11:30. What has been noticable is the production fall off (as much as 25%) now in May compared to February when my system got installed. My advice, do not be to hung up on facing, try and avoid shading.
May 16, 20224 yr Author 13 minutes ago, Peter V said: The research I have done shows not significant difference in daily production (give or take up to 15%) irrespective of facing and inclination through the arc east, north to west provided no shading. Certainly east will provide power sooner with the morning sun and likewise west in the afternoon but if the battery is right sized, it will matter less. My panels are just off north and in full sun all day (roof inclination 25 deg). I'm in East London and typically see production peaking from around 11:30. What has been noticable is the production fall off (as much as 25%) now in May compared to February when my system got installed. My advice, do not be to hung up on facing, try and avoid shading. Thank you 😁
May 16, 20224 yr 1 hour ago, Solarcrazy said: Thank you 😁 I agree , although my west facing string is weaker than north facing at their peaks . In Feb they actually punch above their nominal weight , in May I also experience considerable less performance . But my angle is only 18% , that's bad , good for midsummer but especially bad for this time of year.
May 24, 20224 yr This tool is very helpful for testing different scenarios: https://re.jrc.ec.europa.eu/pvg_tools/en/
June 9, 20224 yr @Solarcrazy Was thinking that your 3 panel NE & 2 panel E strings might not be long enough by themselves to reach a high enough voltage for the MPPT controller to switch on. You may need to make one string with the NE & E panels. Not ideal as this would result in you not getting the maximum from the panels as the amperage would drop down to whatever the lower power production level is from the panels. The East facing panels would be stronger that then NE panels in the morning but weaker in the afternoon. If you join the panels into one string it will only produce the weaker of the two in amperages from the string. What inverter are you thinking of getting? Would be worthwhile having a good look at the space you have available and see if there is no other option to fit more panels on, even if they are a smaller lower wattage panels. Ideally you want to make 300V which is usually 6 panels depending on the voltage of the panels obviously.
June 9, 20224 yr Author 4 hours ago, Sc00bs said: @Solarcrazy Was thinking that your 3 panel NE & 2 panel E strings might not be long enough by themselves to reach a high enough voltage for the MPPT controller to switch on. You may need to make one string with the NE & E panels. Not ideal as this would result in you not getting the maximum from the panels as the amperage would drop down to whatever the lower power production level is from the panels. The East facing panels would be stronger that then NE panels in the morning but weaker in the afternoon. If you join the panels into one string it will only produce the weaker of the two in amperages from the string. What inverter are you thinking of getting? Would be worthwhile having a good look at the space you have available and see if there is no other option to fit more panels on, even if they are a smaller lower wattage panels. Ideally you want to make 300V which is usually 6 panels depending on the voltage of the panels obviously. Hello, I am looking at the Deye 5kw. I am thinking of going for the 595w or 560 X 8 panels. This way I can install all N facing. How do I work out if this is not too much Wattage or Volts for a single MPPT?
June 9, 20224 yr Got a East & West String 7 pannels on each side of 455W Ja Solar 21.5Kw a day now. The West string is weaker though 24' Angle East being the one close to 7.73
June 10, 20224 yr 8 hours ago, Solarcrazy said: Hello, I am looking at the Deye 5kw. I am thinking of going for the 595w or 560 X 8 panels. This way I can install all N facing. How do I work out if this is not too much Wattage or Volts for a single MPPT? Hi @Solarcrazy According to the specifications, the Deye 5kw has 2 x MPPT controller with optimum voltage of between 240V-425V, starts working at 125V. So you can support two strings of panels It is very important not to go over 425V on each string, otherwise you can have smoke & fire from your MPPT controller. Maximum amps is 11A (I think that they have raised this to 12A, not sure). You can overwatt your panels within reason as the inverter is able to restrict the Amps coming from the panels by increasing resistance. Something it can't do with the Voltage Maximum DC input power is 6500W (the total of both strings combined) Canadian Solar panels produce 17.15A max @ 34.7V, you will however not be able to use more than 12A so you are paying for 5.15A of power that you won't be able to use. Would be better to go with the JA Solar panels 535W panels which are rated at 12.97A @ 41.47V, 8 panels would be well within the max voltage, you would loose a small amount of efficiency at max production as you would not be able to use the last bit of power and you would benefit from the extra production on more overcast days. So you chart would have a flat top at 12A on high solar radiation days East and West facing strings are preferable if possible due to the longer hours of production if slightly lower total than a N facing string. The yellow part of the chart if from an North-East facing string the green part is from a NWest facing string
June 10, 20224 yr Author Thanks, so you are saying I should rather do NW facing 8 panels of 535W (4280W production) on one MPPT String (331V, which is less than 425V) due to the longer production time in that direction. And rather not face it N? If this is the case, I would need to see if I have space NW....
June 10, 20224 yr No, the idea is to have your two strings split in East & West directions so you have a longer period of time of making good solar power. East facing panels get the morning sun and start making power earlier than North facing panels but power drops of earlier. West facing panels get the afternoon sun and make power for longer in the afternoon but only start producing power later in the day. If you have a split setup with East and West facing panels you will get the early morning sun from the east panels and the afternoon from the west facing panels. You can see in the chart I posted the yellow East facing string produces peak power @ about 11:00 whereas the West facing green string produces peak power at about 13:00. This will result in a flatter top max power production vs 2 purely North facing strings and probably more power if you are maxing out the DC power production of the inverter. It really depends on what usable area you have on your roof and what directions the panels would be facing. A East/West split (or NE/NW) is definitely preferable to a purely North facing panels for domestic use, especially if you are maxing out the power per string. What do your roofs look like? You also need to be conscious of shade on the panels as shade on 1 panel will pull the whole strings production down to that level.
June 10, 20224 yr Some other random thoughts on the topic. Somewhat stating the obvious, use it, don't use it, whatever fits your scenario. Consider the purpose of this power. If you're using it to heat up your geyser, and you're away from home during the day, a West-facing panel set may make more sense than East-facing so the water stays hotter when you need it. Consider the weather. If you get typical afternoon cloud cover and thundershowers, then East-facing may be better. If you need to recharge batteries after running them down overnight, then the choice might be better to point East to get them fuller earlier. In a scenario where you're running from the grid with a daytime power draw that's higher than the solar generation, you may as well go full-north and generate the maximum off solar that you can. Consider your tariff structure. If you ever have to go grid-tied you may need to move to a time-of-use tariff, or if you're a business, in that case consider pointing East. Power that you generate/save during the peak period from 7-10am is worth more than the equivalent afternoon period from 2pm to 5pm. This could be of most benefit in Gauteng and Eastern parts of the country, as the sun rises earlier and is higher in the sky between 7-10. If you live in Cape Town there may be a case for choosing West as you may be generating some useful power still during the evening peak in summer. Except if you live in the shadow of the mountain.
June 10, 20224 yr On 2022/05/08 at 7:34 AM, Solarcrazy said: Hello.. I want to install 14 panels however I only have space for 8 in the N direction and 3 in the NE and 3 in the E. My question is those that are placed in the NE and E direction.. Typically what time would PV production start and for how long? Hi Solarcrazy, Attached is a spreadsheet I created that you can use to play around with theoretical values. I got the equations from https://www.itacanet.org/the-sun-as-a-source-of-energy/part-3-calculating-solar-angles/. You can add different strings (consisting of panels at different orientations) together to form a bigger plant. Keep in mind that it assumes perfect sunshine and no obstructions. Hope this helps. Solar Angles.xlsx
June 10, 20224 yr Author 9 minutes ago, Peer said: Hi Solarcrazy, Attached is a spreadsheet I created that you can use to play around with theoretical values. I got the equations from https://www.itacanet.org/the-sun-as-a-source-of-energy/part-3-calculating-solar-angles/. You can add different strings (consisting of panels at different orientations) together to form a bigger plant. Keep in mind that it assumes perfect sunshine and no obstructions. Hope this helps. Solar Angles.xlsx 246.88 kB · 0 downloads Oh wow.. Thank you.. Will play around the weekend 😁
June 12, 20224 yr On 2022/06/10 at 3:21 PM, Peer said: Hi Solarcrazy, Attached is a spreadsheet I created that you can use to play around with theoretical values. I got the equations from https://www.itacanet.org/the-sun-as-a-source-of-energy/part-3-calculating-solar-angles/. You can add different strings (consisting of panels at different orientations) together to form a bigger plant. Keep in mind that it assumes perfect sunshine and no obstructions. Hope this helps. Solar Angles.xlsx 246.88 kB · 5 downloads Thanks for the sheet! I tried it, works well! Why are there 13 months?
June 13, 20224 yr 13 hours ago, DJ1 said: Why are there 13 months? Month "0" and "12" should be the same. You can ignore either. Wasn't sure what was the best way to do it...
June 13, 20224 yr @Sc00bs "It is very important not to go over 425V on each string, otherwise you can have smoke & fire from your MPPT controller. " With the sweet spot 125-425V and the maximum only at 500V why do you think one could have smoke exceeding 425 but still below 500V as per the specs. Is it not that you might loose just a percentage or 2 between 425 and 500V?
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