Jan. 20, 2025

Should you install & orient your solar system panels, to maximize Summertime production … Wintertime production …. or some combination???

Aim them due South ? … Aim them slightly South-East ?…

or … Is that asking the wrong question ?** 😉

. Imagine 3 simple orientations for Yucatan’s weather conditions … latitude … and our angles of the sun’s changing position in the Yucatan sky, relative to the front face of the panels.

1. For MAXIMUM WINTERTIME production … Point the panels due South … with a somewhat steep elevation angle of 19º-21º …. which maximizes the WINTER TIME 9 am to 6 pm energy production … where off-angle production is reduced by at least 10% – due to the sunlight captured is reduced from being deflected by off-angle sunlight reflections.

1.a. FOR THE SAME DAILY CLOUD FLUCTUATIONS (same number of morning clouds as afternoon clouds) … then a due-South orientation points the panels most-directly at the sun … with a higher 19º to 21º degree steeper elevation … to maximize WINTERTIME production … especially when the Sun is lower in the sky (because of the sunlight’s longer path through the earth’s atmosphere reduces the solar intensity at the panels)… and because in the mid-Sept to mid-March months our sun is in the SOUTHERN SKY all day.**

(See explanations of monthly, seasonal variation effects below).**

1.b. What temperatures are we having in Merida?
Merida is a HEAT ISLAND that generates it’s own clouds & own weather. When there is lots of sunlight – and hot conditions, as the daily HEAT increases … we have more afternoon clouds … meaning a due South orientation can sometimes give lower daily energy totals, when Merida’s HEAT (on hot day) drive BIGTIME afternoon cloud production.

IOW … Are this year’s COOLER Merida daytime winter temperatures the new normal? … because if so … then a due South orientation maximizes both morning & afternoon solar productions. … while past years’ warmer Merida winter*temperatures drove MORE PAST afternoon cloud production … making the previous slightly South-Eastern panel orientations more effective by gathering MORE of the pure-brighter morning sunlight …

2. For maximum late Spring, SUMMERTIME & early Fall maximum production … remember that the sun tracks PURELY, ONLY across the NORTHERN sky … from March 21’st to Sept 22’nd … each year.

So having a 14º elevation summer angle (lower height) of panels … lower angle than the 20º winter angle- gives lower wintertime production values … but gives roughly 10% more energy production from mid-March through mid-Sept …

IOW … a much improved energy-efficiency* (but not cost effective*) design would be to have panels on a teeter totter to point them NORTH for 6 months of the year … and SOUTH for the other 6 months of the year … to gain 10% – 15% more energy year round.

and the BEST energy efficiency design (but poorest cost effective design*) is to have them move like SUNFLOWERS … tracking the sun’s movement every 15 minutes… which gains roughly 44% more energy,,,

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**BUT… because Chinese govt. $$$ subsidies are so large now… panels are CHEAP … so it’s actually cheaper now to just add an extra panel or 2 … to more than equal the lost 15% due to POOR ALIGNMENT.

Real World Example:
Notice that going from a 6 panel system to a 7 panel system, makes up that 15% inefficient-sun-angle problem … for the $200 cost of another panel. changing a 3.3kW system to a 3.8 kW system … gaining an extra 1000 kWh per yr from that panel … @ Merida’s current $4.3 pesos per kWh of Excedente power … => $4300 pesos per year of savings … WHICH PAYS FOR THE EXTRA PANEL IN as little as JUST ONE YEAR.

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Hint … IF YOUR SOLAR SALES guy did not explain these things … it’s time to get a better solar guy…

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and …

3. Notice that BECAUSE OUR daily CLOUD CONDITIONS are changing with Global Climate change … a slight angling of the panels to the South-East … combined with a flatter 14º elevation angle … would give a higher YEAR ROUND total … but give poorer mid-Winter production.

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Finally … Because CFE gives BIG SUMMERTIME April-Sept Hot Season Mexican taxpayer-paid subsidies vs small winter cool season taxpayer subsidies … of summertime 600 kWh’s subsidies to homeowners of almost 3X CHEAPER power

… Saving Merida homeowners $1,842 PER BILL from April through September using 1000 kWh … versus the small $602 pesos subsidies per bill Winter subsidies …

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SO … Some solar homeowners CHOOSE to have their panels angled DUE SOUTH … to maximize their solar production during the EXPENSIVE POWER RATES Oct-March CFE cool season subsidies of just $602 pesos …

and yes, you lose 10%-15% of energy generation in the summertime … but summertime is when CFE GIVES YOU $1,842 per bill of subsidies…

subsidies paid by us Mexican taxpayers …

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Again, IF your solar salesperson is NOT explaining these factual realities … maybe it’s time to change solar companies.

Dr. Steven M. Fry
Ph.D in Science … and Solar System repair guy in Yucatan since 2007.

https://app.cfe.mx/aplicaciones/ccfe/tarifas/TarifasCRECasa/Tarifas/Tarifa1D.aspx


Cheers,
Dr. Steven M. Fry


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Feel free to copy while giving proper attribution: YucaLandia/Surviving Yucatan.
© Steven M. Fry