Hourly output of West facing (270 azimuth) panels

[J.P.M.]

My photovoltaic array faces due South.

I am located near enough to the Magnetic pole that deviation here is large. I built a large sun-dial before construction of our house, so I could establish True North/South. I wanted our house' Passive Solar gain to be maximized. Later when I was constructing our Solar-Power array I built it to run parallel to our house.

I have read other people who have set a part of their PhotoVoltaic array to face East, to maximize the morning rays. I find that an interesting idea. But I think the total number of sun-light hours a panel can utilize would be fewer hours if it is facing anything other than due South.

I can see the idea behind getting a boost in wattage the morning. But I think the total wattage per day would be reduced.

I agree that:


I am not in a state with T.O.U. tariffing. There is no possible 'revenue' from solar power production in my state either. So I never had any reason to consider those parts of a puzzle, that would only apply in some other state.

All reference to compass orientation uses true north - magnetic deviation has nothing to do with it unless users are unaware of the necessity of magnetic compass corrections. There are any number of very accurate ways to to determine true north without a magnetic compass. I've outlined a couple in prior posts.

The actual optimum orientation of a solar energy collection device with respect to both azimuth and tilt will vary by location and weather with, for example, geographic features like hills or structures and local common/predominant weather patterns (morning fog/seasonal wind/cloudiness patterns/etc., often and usually shifting the optimum orientation off dead south by a bit. Example: my optimum azimuth for year round max. production is about 186 deg. My property out in the desert has hills about peak about 3 miles to the west that shift the optimum array azimuth to about 178 deg. or so.

Many or, I suspect, parts of most states and areas of the country have, or will have, some form of T.O.U. tariffs in force or available as an option.

I'd also expect that the schedules and peak pricing for such tariffs can be expected to be fluid and changeable as users shift their usage patterns in response to the price squeezes of peak time rates, causing POCOs to adjust peak and other times.

As Gavin Newsom (CA Lt. Gov., speaking about gay's right to marry) said: "It's gonna' happen, whether ya' like it or not."

Regardless of your situation, T.O.U. is the handwriting on the wall for many, if not most parts of the U.S. FWIW, that's probably a good scenario more than bad. With T.O.U., users will have more control over how big their bills will be. They already have a lot of control now, but mostly either don't know it, or know how to turn stuff off, or don't choose to exercise their options. T.O.U. will usually allow some additional flexibility and choice with respect to some control over how much they pay for what they do use - not complete control, just more control as f(when the power is used). That some /most may choose to look at such an option as an impossibility because it's perceived as an inconvenience is a matter of more choice.

[J.P.M.]

Well. I live in Texas and my west facing panels peak around 2:30. About 1/4 of my panels face west with the rest south. The whole array peaks around 1:45. My west facing panels produce about 6% less than the south facing panels.

Sounds about right.

[organic farmer]

My photovoltaic array faces due South.

I am located near enough to the Magnetic pole that deviation here is large. I built a large sun-dial before construction of our house, so I could establish True North/South. I wanted our house' Passive Solar gain to be maximized. Later when I was constructing our Solar-Power array I built it to run parallel to our house.

I have read other people who have set a part of their PhotoVoltaic array to face East, to maximize the morning rays. I find that an interesting idea. But I think the total number of sun-light hours a panel can utilize would be fewer hours if it is facing anything other than due South.

I can see the idea behind getting a boost in wattage the morning. But I think the total wattage per day would be reduced.

I agree that:

... Off south orientations will shift peak production time - to later in the afternoon for westerly facing and before noon to easterly facing with larger off south generally producing more time shift

I am not in a state with T.O.U. tariffing. There is no possible 'revenue' from solar power production in my state either. So I never had any reason to consider those parts of a puzzle, that would only apply in some other state.

[easye]

Well. I live in Texas and my west facing panels peak around 2:30. About 1/4 of my panels face west with the rest south. The whole array peaks around 1:45. My west facing panels produce about 6% less than the south facing panels.

[J.P.M.]

Off south orientations will shift peak production time - to later in the afternoon for westerly facing and before noon to easterly facing with larger off south generally producing more time shift. But, and do not forget, off south orientations will, for most locations, reduce the size of the peak and also the total daily and yearly output, sometimes, depending on local climate, by a fair amount - more off south, more reduction in both daily peak and annual output.

Now, depending on array orientation, local insolation patterns and how the T.O.U. tariff is configured, there is a theoretically optimum orientation (tilt and azimuth) that maximizes annual $$ output from a given array size, different from max. kWh production. That optimum orientation for max. revenue to offset an electric bill seldom exists in reality. More usually it's a matter of comparing $$ production per installed kW for various available orientations and selecting the orientation that produces the most $$ offset per kW (but not necessarily for the most energy output).

Comparing estimates of annual revenue production per kW of system size for various available orientations by combining PVWatts hourly output option with a user's hourly usage history from a POCO on a spreadsheet will often provide useful information. If the available optimum orientation is full, the next optimum orientation can be used, etc.

Commonly, but not always, the optimum orientation in terms of $$ revenue for a lot of current T.O.U. tariffs is closer to an orientation of very approx. 200 - 230 deg. or so. Again, run PVWatts for your location for better estimates.

Often, and in spite of what a POCO may tell you, at least in most of my area, if given a dichotomous choice between a mostly south and mostly west orientation, the mostly south orientation will produce both more output and more revenue than a mostly west facing array of equal size (but the revenue production difference will probably be less disparate). It's never a slam dunk, and given the ease of a PVWatts run or two, the availability of POCO hourly usage data and the ease of constructing a spreadsheet revenue calculator as described above, no reason to assume west is always the best revenue producer.

[cnil1]

I am in Phoenix and am starting to research solar. I have seen on the Enphase website public section that solar panels that are facing South produce about half of their daily kWH before noon and half after. In other words, the bell shaped hourly production curve peaks at noon.

My question, at what time does production peak with West facing panels? Many or even all of my panels will face West due to roof space limitations and also I would like to shift production until afternoon, because I will be on the APS ET-2 rate plan and I want to offset the most expensive time of the day, which is 12pm to 7pm.