Study says solar panels are better west than south?

evme said:

I often heard that solar panels are best if they are facing south, others say any direction but north. But a study by pecan street research institute says west is the best side is west offering 2-11% improvement.

http://inhabitat.com/have-we-all-been-installing-solar-panels-the-wrong-way/

Click to expand...

This was one study in one location and I think they mean SW not W. There may have been atmospheric conditions that skewed the results. I can see a future where it would be beneficial to sacrifice overall production in favor of higher production in the evenings but sadly we're probably decades away from that level of solar penetration in most areas.

And it's not like most people have a lot of choices of where to install solar panels on their roof. I have half my panels facing southwest and half facing southeast, because that's just the way my roof is. I do notice better production on the southwest-facing panels, which I think it due to the weather we have around here (often marine layer in the morning and sunny in the afternoon).

One advantage for west facing is it produces more power in the evening during the peak energy usages times. Peak rates are 12 to 6 in many places. South facing produces more on the morning, but less in the afternoon.

I'm out of south facing roof so when I expand I'll add to the west side. I have far more west facing roof than anything else.

FWIW, due to my roof layout, I have a totally east-west 16 kW Solar City install (63 panels, 5 strings). To balance out the swings due to panel layout and sun transit, each Canadian Solar panel has a special SolarEdge module that somehow allows the current to 'bypass' a panel that is underperfroming. I have 4 single SolarEdge inverters that match/sync with the strings. Work for me....

South is best.

My panels face South and on clear cloudless days I produce nearly identical amount of energy before and after Solar Noon. Being in Long Beach, "June Gloom" does have a significant impact. Solar for 10+ years now.

That story is terribly misleading because of the very poor and imprecise language used.

What they are trying to say is that if you have a small solar system that provides less power than your evening demand, then you can have it provide a larger fraction of that evening demand by turning the panels SW. This will only work if your system is undersized, or you don't have net metering.

Otherwise there is no question that south facing panels generate more energy.

The more accurate way to answer the question is to say that the panels should be perpendicular to the sun's rays at solar noon. This will account for variations in latitude (including "down under") and seasonal effects. Obviously local conditions might dictate otherwise. Keeping the panels perpendicular to the sun's rays continuously throughout the day (dual axis tracker) results in the maximum output possible for a given array.

Amd it appears they were trying to match peak production to peak needs and peak demand charges. So SW could work if you use a lot of power in the afternoon and you have peak rates. But for most of us mortals a southern exposure is best.

The question is whether you should be maximizing the quantity of power you generate or the value. Just as a quick look, I pulled up the average (day-ahead) power prices in Texas for July 2013. During daylight hours:
These prices are the actual cost of running power plants somewhere in the state, not some value set in a tariff. So from a pure economics POV, generating power in the morning is worth only ~half as much as power in the afternoon. Retail tariffs mask this value from consumers, however, so we make bad decisions.

In terms of maximizing power production, tracking the sun is ideal -- perhaps this is obvious. Unfortunately tracking mounts still cost a lot! I don't really think they should, but without widespread deployment, there aren't many economies of scale in the manufacturing.

You need to know the weather on this. My experience is that morning fog where I live changes the rules. The fog doesn't burn off for some hours and by then the sun will be more to the west. And when the fog is there the direction doesn't matter so much because the fog diffuses the light so that direction doesn't matter so much. So I'll echo markb1 re: marine layer changes things.

Well here in NC, for 6 months 1-4 pm is off peak. So my East facing panels are the best - they start trailing off at 1:30 this time of the year. My house has all its glass facing East so summertime a/c is actually pretty strong in the AM.

So every area is different when it comes to peak electricity cost. Even in Texas, July is just one month...

I think this is likely determined more by weather than anything else. Where I live, we tend to get afternoon thunderstorms most summer days, and in winter storms tend to be either all day or not at all, so I suspect that facing east may be more productive.

Then again, the temperature of the panel may have an impact on efficiency, and as the heat distribution during the day is skewed towards the afternoon, west may be better overall.

Someone should do some studies in various places to test this out. Then again, if you can develop efficient, effective, and cheap sun tracking systems, that would be better still.