is the optimum year round angle what you really think it is?

[wattmatters]

With Enphase Enlighten , you can play around with the orientation of each array and instantly see the monthly and yearly production estimates.

Handy. It's just using this site which anyone can use:

PVWatts

Estimates the energy production and cost of energy of grid-connected photovoltaic (PV) energy systems throughout the world. It allows homeowners, small building owners, installers and manufacturers to easily develop estimates of the performance of potential PV installations

pvwatts.nrel.gov

I keep an old AC powered alarm clock in one of my bedrooms. Whenever the grid goes down, it stops and when the grid is restored, I can tell exactly how long the grid was down by calculating how far behind it is compared to the real time.

During grid outages I flip over to our off-grid backup system. Several high power circuits are excluded from backup supply, including our oven and these are only connected to grid supply. The oven acts as my indicator for when grid power has returned, the clock comes back on and the oven makes a nice bleeping noise when power is restored. In our case the clock resets to 00:00 on power up and so rather than how long the outage was for, I can tell how long ago grid power was restored if I have not heard the beep. In any case my data loggers tell me all this data.

this happens in Houston from the prevailing South winds injecting moisture from the Gulf of Mexico into the atmosphere

Accounting for local weather patterns will make some difference to assessing which orientation squeezes out optimal production.

But for rooftop arrays, you just use the roof you have and in general just putting up more panels is cheaper and more effective than attempting to tilt panels. Tilting often reduces the number of panels which can fit a given roof surface area as you have to space the panels so one row doesn't shade the one behind it. Crinkle cut set ups can help but it's extra expense and rarely worth it in a domestic set up.

 

[12VoltInstalls]

Do you have total year production data from the panels on the different azimuths?

I do not. I’ve played little games with 200W panels including 2S on a pwm to thwart December clouds that would have me at 10V PV all day (nothing in other words) but I could get a bit of charge in series.
My increase to 400W and the mppt led to other “games” while I awaited connectors to use six 100W panels- the two-directional experiment worked so well for a week that I left it at 400W spring - october. Rearranging and going to two 400W arrays is going to be way overkill in a month or two but it was useful this winter.
So I don’t have recorded data- I just know I wasn’t charging/holding enough in a sunny period, but changing to bidirectional again I instantly was 12.9-13.2 near sunset, and 12.4-12.5 in the AM instead of 12.2 or 12.1. That convinced me!

I may throw another panel in this spring and play with three directions 3S3P to see what happens- but it won’t probably show me anything because I’m overpaneled for my demand.

you just use the roof you have and in general just putting up more panels is cheaper and more effective than attempting to tilt

That is how I felt about it: panels using the space I had for convenience seemed better and cheaper than the logistics of ground mounting for tilt or cleaning off snow.

 

[TBoone]

If you really want precision:

SunCalc sun position- und sun phases calculator

Application for determining the course of the sun at a desired time and place with interactive map.

www.suncalc.org

-TBoone

 

[12VoltInstalls]

If you really want precision

There’s sometimes advantages to off-optimal positioning in higher latitudes and/or time-of-use requirements.

 

[kanelr]

You angle panels based on what production is more important to you. For maximal annual production it will generally be a tilt close to your latitude. If you want superb Summer performance then lie them flatter, if Winter is key to you then have them steeper. It all depends on what's most important to you - overall output or when the power is produced.

Then you need to work out azimuth and whether maximal peak production from a south facing array is more important than evening out production across the day with split azimuth facing east and west, or whether morning or afternoon production is more important. In some locations weather patterns might often see morning fogs or afternoon storms and so sometimes greater overall output is attained by an azimuth a little away from south (or north if you are in stern hemisphere).

For roof top array you kind of just put panels on the roof and the decision is made for you.

"For roof top array you kind of just put panels on the roof and the decision is made for you". I would add Unless you go to the trouble of using complicated mounts

 

[Casey]

I have personally found it best to optimize for winter sun, since the days are much longer and the skies much more often clear in the summer. I have no problem keeping batteries topped off all day in the summer even with air conditioning running, and actually have to switch off some of my panels to keep my charging rate low enough to not prematurely age my batteries. In the winter I have a harder time not running out of power overnight, and need to get every bit I can when the sun is out, especially during overcast periods. For fixed installation, I am thinking of building something with a roof with a south-facing slope at a 45-degree angle. That's a nice simple angle for building and the panels will be biased towards winter as I've found is best for my needs.