Page 1 of 2 1 2 LastLast
Results 1 to 20 of 28
  1. #1
    Join Date
    Jan 2013
    Location
    Jhb
    Age
    45
    Posts
    287
    Thanked: 11

    Default Solar Panel Calculator For My Trailer

    Having read a number of threads containing debate about what panel size is adequate to survive without shortage of supply I decided to run some tests at home to see what results I could achieve.

    From my experience so far and numerous articles that I have read I created the attached excel calculator.

    Let me know if I could improve on it, I make no claim to it accounting for all scenarios but it seems to have worked for me so far.

    Notes:
    1. Only change yellow cells
    2. Biggest impact on supply is hours you can achieve of sunlight
    3. Biggest impact on consumption is hours of compressor at full usage

    When I ran tests at home with fridge untouched I got days more than when opening an closing the fridge door, it makes a massive impact!
    Attached Files Attached Files
    2017 FORD, Ranger Wildtrak
    2015 Bush Lapa, Boskriek 444

  2. #2
    Join Date
    Aug 2012
    Location
    Okahandja, Windhoek
    Age
    69
    Posts
    5,000
    Thanked: 1226

    Default

    I am sure you would get more than 60% eff out of a solar panel. With a fix position you will get 6 hour at full amps. If you track the sun it can be 20 to 30 % more, or 7 hours at full amps. The volts should be the charged volts namely 14.2? for the solar and the rest 12 volt

    Agree you need to allow for days not full sun. If that is the 60% than I agree to a certain extent, but thats maybe for a contingency plan only.
    Last edited by JLK; 2015/02/25 at 08:04 PM.
    Johan Kriel

  3. #3
    Join Date
    May 2009
    Location
    Hillcrest
    Age
    65
    Posts
    20,089
    Thanked: 10229

    Default

    Quote Originally Posted by JLK View Post
    I am sure you would get more than 60% eff out of a solar panel. With a fix position you will get 6 hour at full amps. If you track the sun it can be 20 to 30 % more, or 7 hours at full amps.

    Agree you need to allow for days not full sun. If that is the 60% than I agree.
    The industry standard for daily average best performance efficiency is 40 odd %. That's perfectly clear weather, not tracking but optimum position.
    Cheers

    ZS5KAD - PROFFESIONAL DUMBASS
    3 Land Rover V8's
    NA - TwinTurbo - SuperCharged
    A V6 and an inline 4

    If you fly or drive to an anti-Fracking meeting, you have no business being there and you wont get my ear......

  4. #4
    Join Date
    Aug 2012
    Location
    Okahandja, Windhoek
    Age
    69
    Posts
    5,000
    Thanked: 1226

    Default

    That might be a design? standard, but in reality I don't agree.
    Johan Kriel

  5. #5
    Join Date
    May 2009
    Location
    Hillcrest
    Age
    65
    Posts
    20,089
    Thanked: 10229

    Default

    Quote Originally Posted by JLK View Post
    That might be a design? standard, but in reality I don't agree.
    In reality I would think you may be even lucky to get 40%.

    I can send you a link to a website (Actually more than one) that shows blow by blow, hour by hour power generation from professional installations.

    You can see the power generated as it is happening and the historical data over hours, days, weeks, months and years.
    Cheers

    ZS5KAD - PROFFESIONAL DUMBASS
    3 Land Rover V8's
    NA - TwinTurbo - SuperCharged
    A V6 and an inline 4

    If you fly or drive to an anti-Fracking meeting, you have no business being there and you wont get my ear......

  6. #6
    Join Date
    Aug 2012
    Location
    Okahandja, Windhoek
    Age
    69
    Posts
    5,000
    Thanked: 1226

    Default

    Than I should double up all my installations that served me over the years.
    Johan Kriel

  7. #7
    Join Date
    May 2009
    Location
    Hillcrest
    Age
    65
    Posts
    20,089
    Thanked: 10229

    Default

    Quote Originally Posted by JLK View Post
    Than I should double up all my installations that served me over the years.
    While your installations may very well have worked over the years, its not because of the reasons you state. Probably just nicely over sized or specced.

    The point I am trying to make here is that nobody EVER, ANYWHERE, got 100% output power from a SOLAR array for 7 hours in a day. Not even 6 hours. And almost certainly not even 30 minutes.

    Please look at the graph below.

    This is todays DATA. Mid summer, no cloud cover. Best in class equipment in a test installation of a MAJOR very respected SA supplier. I have access to many more sites and data.

    9kW Array, 12 hours of sunlight. Total Power generated is 50kWh

    12 hours X 9kW = 108kW potential generation. The efficiency of this professional system under almost ideal conditions, in a day, is less than 50%.

    To suggest that people base a design for general consumption on a figure greater than 45% is irresponsible and misleading.

    The attachment is live real data from today, right here in JHB, not some Lab in China.
    Attached Images Attached Images
    Last edited by Fluffy; 2015/02/25 at 09:47 PM.
    Cheers

    ZS5KAD - PROFFESIONAL DUMBASS
    3 Land Rover V8's
    NA - TwinTurbo - SuperCharged
    A V6 and an inline 4

    If you fly or drive to an anti-Fracking meeting, you have no business being there and you wont get my ear......

  8. #8
    Join Date
    Jan 2013
    Location
    Jhb
    Age
    45
    Posts
    287
    Thanked: 11

    Default

    The 60% efficiency I can vouch for as that is what I get from the 50W panel on my garage roof... I can regularly get 20Ah from that panel on a good sunny day, but not much more than that so whether you tweak the hours of sunlight or the efficiency you will get more or less that on my calc.

    Many factors influence the efficiency but I am happy to stick to my 60% and change the hours of good sunlight in my calc as really achievable.

    Plus that is what the spec sheet says...
    50W max under "standard test conditions"
    35,9W max under "normal conditions"

    http://www.bushpower.co.za/content/d...0_poly_RMA.pdf
    2017 FORD, Ranger Wildtrak
    2015 Bush Lapa, Boskriek 444

  9. #9
    Join Date
    Aug 2012
    Location
    Okahandja, Windhoek
    Age
    69
    Posts
    5,000
    Thanked: 1226

    Default

    Did not know that your radiation is so poor there. You should get away form there

    Seriously we get much more watts from a solar here.
    Last edited by JLK; 2015/02/26 at 08:37 AM.
    Johan Kriel

  10. #10
    Join Date
    May 2009
    Location
    Hillcrest
    Age
    65
    Posts
    20,089
    Thanked: 10229

    Default

    Quote Originally Posted by SvenT View Post
    The 60% efficiency I can vouch for as that is what I get from the 50W panel on my garage roof... I can regularly get 20Ah from that panel on a good sunny day, but not much more than that so whether you tweak the hours of sunlight or the efficiency you will get more or less that on my calc.

    Many factors influence the efficiency but I am happy to stick to my 60% and change the hours of good sunlight in my calc as really achievable.

    Plus that is what the spec sheet says...
    50W max under "standard test conditions"
    35,9W max under "normal conditions"

    http://www.bushpower.co.za/content/d...0_poly_RMA.pdf
    60% in one good hour is easy peasy. Even 90% is quite the norm.

    60% over a total day is an altogether different story. You will have two or three hours at high efficiency and another 6-8 at very much reduced efficiency.

    Have a look at the graph I posted.

    That's not a spec sheet, that's real life.

    When doing these calcs you cant try and play with how efficient the panel is and how many hours of sun you have.

    You are operating day to day. How much power do I generate per day.

    We are now into the realm of total energy yield, not efficiency.

    How much power will a panel generate per day.

    Panel W x 10/4 is the answer. In Summer in a good system. Note that this is more than your 6 hours at 60%. Its just a less subjective more accepted way of specifying it.
    Cheers

    ZS5KAD - PROFFESIONAL DUMBASS
    3 Land Rover V8's
    NA - TwinTurbo - SuperCharged
    A V6 and an inline 4

    If you fly or drive to an anti-Fracking meeting, you have no business being there and you wont get my ear......

  11. #11
    Join Date
    Jan 2013
    Location
    Jhb
    Age
    45
    Posts
    287
    Thanked: 11

    Default

    Look it's jhb and the air is not exactly clear. So am sure there are some losses there.. Seriously though it's on the roof at no special angle and the roof faces the way the roof faces which is luckily more or less at the sun for the majority of the day.

    However in my experience unless you track the sun with the panel direction and angle I struggle to get a better efficiency... And most web sites I read say the same.

    All I can advise buyers of panels is don't assume the power rating is what you will get out, because losses occur with wrong angle, wrong direction, heat build up, dirt on glass, poor connections, cables etc.
    2017 FORD, Ranger Wildtrak
    2015 Bush Lapa, Boskriek 444

  12. #12
    Join Date
    May 2009
    Location
    Hillcrest
    Age
    65
    Posts
    20,089
    Thanked: 10229

    Default

    Quote Originally Posted by SvenT View Post
    Look it's jhb and the air is not exactly clear. So am sure there are some losses there.. Seriously though it's on the roof at no special angle and the roof faces the way the roof faces which is luckily more or less at the sun for the majority of the day.

    However in my experience unless you track the sun with the panel direction and angle I struggle to get a better efficiency... And most web sites I read say the same.

    All I can advise buyers of panels is don't assume the power rating is what you will get out, because losses occur with wrong angle, wrong direction, heat build up, dirt on glass, poor connections, cables etc.
    Agree.

    Exactly what I am saying.

    Max energy per day is Panel W x 10/4

    Counting on more than that unless you are on top of a cold sunny mountain with a tracking array would be foolhardy.
    Last edited by Fluffy; 2015/02/25 at 10:54 PM.
    Cheers

    ZS5KAD - PROFFESIONAL DUMBASS
    3 Land Rover V8's
    NA - TwinTurbo - SuperCharged
    A V6 and an inline 4

    If you fly or drive to an anti-Fracking meeting, you have no business being there and you wont get my ear......

  13. #13
    Join Date
    Jan 2013
    Location
    Jhb
    Age
    45
    Posts
    287
    Thanked: 11

    Default

    Keith, I totally agree that's a matter of energy yield in a day, I thus built the calc to quantify how you get to a daily supplied Ah figure from a rated panel wattage, it's semi theoretical but tried and tested to come out with what I yield on my 2 panels.

    I cannot comment much on a fully installed PV array, as all my experience and working is on single solar panel as installed on my trailer and similar on panel on my garage roof to charge batteries and keep some LED lights on during load shedding

    I struggle to get your formula of panel W x 10/4

    So by your formula my roof panel would be 50W x10 /4 = 125Wh, if I want that in Ah on a 12v system I get 10,41Ah... Yet I get double this for sure on a good day, what am I missing in my logic here?
    2017 FORD, Ranger Wildtrak
    2015 Bush Lapa, Boskriek 444

  14. #14
    Join Date
    May 2009
    Location
    Hillcrest
    Age
    65
    Posts
    20,089
    Thanked: 10229

    Default

    Quote Originally Posted by SvenT View Post
    Keith, I totally agree that's a matter of energy yield in a day, I thus built the calc to quantify how you get to a daily supplied Ah figure from a rated panel wattage, it's semi theoretical but tried and tested to come out with what I yield on my 2 panels.

    I cannot comment much on a fully installed PV array, as all my experience and working is on single solar panel as installed on my trailer and similar on panel on my garage roof to charge batteries and keep some LED lights on during load shedding

    I struggle to get your formula of panel W x 10/4

    So by your formula my roof panel would be 50W x10 /4 = 125Wh, if I want that in Ah on a 12v system I get 10,41Ah... Yet I get double this for sure on a good day, what am I missing in my logic here?
    Oops, quite correct. Sorry.

    It should be Array W x 10/2 per day.

    So 50W will give 250Wh as you say.

    This is right in line with the Graph I posted.

    Arithmetic error. The 4 came from my rule of thumb of, - count on 4 hours at max power ie in this case 200W, which is what I would design around instead of 250W, just as a safety factor.
    Cheers

    ZS5KAD - PROFFESIONAL DUMBASS
    3 Land Rover V8's
    NA - TwinTurbo - SuperCharged
    A V6 and an inline 4

    If you fly or drive to an anti-Fracking meeting, you have no business being there and you wont get my ear......

  15. #15
    Join Date
    May 2009
    Location
    Hillcrest
    Age
    65
    Posts
    20,089
    Thanked: 10229

    Default

    Your spreadsheet reveals some interesting info.

    A 150W panel is not as OTT as I thought.

    It has the potential to be marginal if you open the fridge often and the weather doesn't play ball.

    EDIT - It may be worthwhile doing some actual measurements of the fridges current draw. I am not convinced those fridges actually draw a constant extended 5.5A when running.
    Last edited by Fluffy; 2015/02/25 at 11:35 PM.
    Cheers

    ZS5KAD - PROFFESIONAL DUMBASS
    3 Land Rover V8's
    NA - TwinTurbo - SuperCharged
    A V6 and an inline 4

    If you fly or drive to an anti-Fracking meeting, you have no business being there and you wont get my ear......

  16. #16
    Join Date
    Jan 2013
    Location
    Jhb
    Age
    45
    Posts
    287
    Thanked: 11

    Default

    Thanks Keith for the clarity, that makes more sense, different formula but pretty much the same result, for my next version I will add that as a comment.

    The fridge is by far the biggest impact, and to your point on yield earlier the same goes for consumption, I don't really worry to much about the actual amps it draws but rather Ah it consumes over a day. So whether it's 5A or 5,5A is not a big issue its how many hours a day it runs at full rating that gives the consumption impact. Again the calc is just to show that as a quantified formula as simply as possible.

    The calculator also can't compensate for the environmental impacts, as in my garage with my fridge untouched I get rather large swings in daily consumption, simply one day the compressor runs more than another even though average temperatures etc. remain constant.

    The calculator I at least hope helps to guide and provide insight to ensuring you consider the right size panel, it's can never be a perfect formula.
    2017 FORD, Ranger Wildtrak
    2015 Bush Lapa, Boskriek 444

  17. #17
    Join Date
    Aug 2012
    Location
    Okahandja, Windhoek
    Age
    69
    Posts
    5,000
    Thanked: 1226

    Default

    Indeed an eye opener regarding the radiation levels there. We have an average level 6400W/m2/day. So no issue to work on the rated watts.

    If 800W/m2 is 72% of the rated watts (at 1000w/m2) then I can believe you can get lower at some places. But that's not the place where we camp With a PWM controller the watts will then be 2.2 x 14 = 28 Watts for that 50 Watt panel which getting close to the 50%

    Running time on a fridge is very depending the ambient temperature, it could be anything from 20% to 100% in our range of temperatures. I work on average 70% at 35 to 40 deg day time temperatures, for the over spec design.

    SvenT yes a nice calculator anyway to get an idea where one should go
    Last edited by JLK; 2015/02/26 at 09:19 AM.
    Johan Kriel

  18. #18
    Join Date
    May 2009
    Location
    Hillcrest
    Age
    65
    Posts
    20,089
    Thanked: 10229

    Default

    Quote Originally Posted by JLK View Post
    Indeed an eye opener regarding the radiation levels there. We have an average level 6400W/m2/day. So no issue to work on the rated watts.

    If 800W/m2 is 72% of the rated watts (at 1000w/m2) then I can believe you can get lower at some places. But that's not the place where we camp With a PWM controller the watts will then be 2.2 x 14 = 28 Watts for that 50 Watt panel which getting close to the 50%

    Running time on a fridge is very depending the ambient temperature, it could be anything from 20% to 100% in our range of temperatures. I work on average 70% at 35 to 40 deg day time temperatures, for the over spec design.

    SvenT yes a nice calculator anyway to get an idea where one should go
    Correct. Hence the industry standard of approx. 4hours a day at max Watts for a total power generated thumbsuck, especially for a camping system that may be deployed almost anywhere any time.

    If one is designing for permanent sites you have the luxury of optimizing the system for the location.

    I would love a sight at 4000m ASL in the middle of a desert with a tracking array.
    Cheers

    ZS5KAD - PROFFESIONAL DUMBASS
    3 Land Rover V8's
    NA - TwinTurbo - SuperCharged
    A V6 and an inline 4

    If you fly or drive to an anti-Fracking meeting, you have no business being there and you wont get my ear......

  19. #19
    Join Date
    Jun 2011
    Location
    Bosveldsig, Nylstroom/Modimolle
    Age
    66
    Posts
    1,969
    Thanked: 265

    Default

    SvenT,
    Just a question.
    Noted you have days until cut off as a negative value.
    Does this indicate how many days you can run till battery is at 50% charge?
    Danie & Marinda - die wiele is rond, dus moet hulle hardloop - afgetree nou leef ons net.
    2017 BL - Kewer B1115 RUS WA GP - bos en kamp tyd
    2016 Ford Fiesta Ecoboost - daaglikse ryding
    2013 Ford Ranger 3.2 DC XLT 4x4 - nuwe rondloop ry ding, nou sleep ons! (2017)
    2011 Echo 4, die RUSWA-ZN - (verkoop 44 000 km)
    2010 Ford Ranger 2.5 DT DC XLT 4x4 - rondloop ry ding met "bietjie ekstra" krag (Verkoop 177 000 km)
    2005 Chev Aveo - Afgeskryf (2016 130 000)
    2005 Opel Corsa 17DTi - Geruil (warm enjin 180 000)
    2003 Opel Corsa 17DTi - Geruil (warm enjin 150 00)
    2000 Nissan Hardbody - Geruil (pyne by die duisended 52 000 km)
    1998 Opel Kadett - Dogter se wiele geword in 2003 (baie warm enjin 116 000 km)
    1990 Datsun 1800 short wheelbase - Pa se ou plaas bakkie, na die Nissan die pad gevat het met sy probleme in 2003 (117 00km)
    1990 Hilux 2.4D - en hy kon loop, pomp en top gewerk aan.
    1984 Opel Commondore - het gehardloop
    1983 Safary 3 karavaan - verkoop en begin tent in 2000 (51 000 km)
    1980 Ford Granada 3.0 - warm enjin afgeskryf
    1969 VW 1600 TL - geen einde nie, warm enjin en geruil
    1968 VW 1600 L - geen einde en baie warm enjin, verkoop in 1998 (328 000 myl/525 000 km)

    .

  20. #20
    Join Date
    Jan 2013
    Location
    Jhb
    Age
    45
    Posts
    287
    Thanked: 11

    Default

    Hi Danie,
    Sorry if that is not so clear, I will soon upload a version 3 with some footnotes based on questions asked and yours is a valid one.

    Your assumption is however correct, so for example if you enter 0 watt solar panel you will see how long you can last to cutoff without any solar panel, you then increase the solar wattage until the days is enough or figure becomes positive and it will say "you have adequate supply"

    You can change any of the yellow cells, so of you don't want your battery to go as low as 50% change that to say 60% and you will see the effect on the days until cutoff adjust down.

    Hope it's clear, let me know if it helps and if any other questions or comments welcome.

    Kind Regards, Sven
    2017 FORD, Ranger Wildtrak
    2015 Bush Lapa, Boskriek 444

Page 1 of 2 1 2 LastLast

Similar Threads

  1. Nosecone on an Echo 3 trailer
    By swerwer in forum Trailers, Caravans, Towing etc
    Replies: 22
    Last Post: 2020/02/08, 08:22 PM
  2. Solar system ...
    By Elders in forum Camping, Fridges, Accessories
    Replies: 73
    Last Post: 2013/02/27, 12:09 AM
  3. Solar Experiment 80W
    By PGJ in forum Camping, Fridges, Accessories
    Replies: 67
    Last Post: 2011/08/20, 06:39 AM
  4. Got my solar panel today..
    By Gert du Preez in forum Camping, Fridges, Accessories
    Replies: 12
    Last Post: 2010/12/10, 05:36 PM
  5. Solar Panel calculations?????
    By Tricky Dicky in forum Camping, Fridges, Accessories
    Replies: 12
    Last Post: 2010/11/21, 11:34 AM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •