Cheap Panels = No Solar Trackers?

Re: Cheap Panels = No Solar Trackers?

Not all trackers are $6,000: http://www.solar-electric.com/zotrmoforsoe.html

However, for the most part the "more panels vs. tracker" debate already comes out with more panels ahead most of the time. This will only augment the result.

But there will always be those sites where tracking is the way to go.

Re: Cheap Panels = No Solar Trackers?

Of course there's the third option which is becoming more financially feasible as prices drop:
Multiple arrays on separate charge controllers facing in different directions.

If you wanted to get really clever with this you could have an "East array", "South array", and "West array" - and tailor the sizes according to the predicted power need at the time of the day. For instance the East array would be large enough to get through the Bulk charge stage before midday. The South array would only need to be sufficient for Absorb/Float and loads. The West array would pick up the Float and loads function until the sun was too low to provide any real power.

Crazy? Perhaps. But it is possible and would work.

Re: Cheap Panels = No Solar Trackers?

solar_dave wrote: »

I am confused why this might not work?

It would work.
But it would be dreadfully inefficient compared to using a tracker.
Think about it: you'd need 2.5-3 times as many panels to produce the same kW hours per day as a tracked system. Plus two more charge controllers. Panels may be cheap, but they're not that cheap. Not yet anyway.

In defense of my own crazy idea I have to add that there are some sites that do not lend themselves to trackers but could make use of redundant arrays. Let's just say I happen to know one.

Re: Cheap Panels = No Solar Trackers?

Here's another way to look at it:

One 400 Watt array mounted on a tracker vs. three 400 Watt arrays mounted East, South, and West.

Angles will make a huge difference here. Not only the angle for insolation of the panels but the angle of the sun as it moves through its daily arc.

The East and West arrays will not get the "4 hours equivalent good sun" we count on for a South-facing array because the early and late hours will not be as intense even if "square on" (which they wouldn't be) due to the sun filtering through more atmosphere. Worst-case scenario you get 2 hours equivalent. This would mean:

South array = 400 Watts * 4 hours = 1600 Watt hours
East array = 400 Watts * 2 hours = 800 Watt hours
West array = 400 Watts * 2 hours = 800 Watt hours
Total: 3200 Watt hours from 1200 Watts of array.

400 Watts on tracker * 8 hours = 3200 Watt hours from 400 Watts of array.

Again, depending on the angles of the East and West arrays there could be significant drop-off in production as the sun shifts from the East to the South to the West arrays. The tracking system will not suffer this potential loss.

I know: I propose the system and then proceed to shoot it full of holes. But you have to question your own thesis or else it isn't proven.

Besides, my original idea was to have the largest of the array facing East (probably South-East would be better, depending on the site) for early morning Bulk recharge after night use, with lesser arrays (possible 1/2 or even 1/4 the main array size) on South and South-West facets to maintain the batteries through the day.

The real point is, don't rule out the possibilities. Solar is highly site-specific and you need to tailor the system not only to the power requirements but also to the availability of sun. Too often that gets left out when system design gets reduced to the simplest rule-of-thumb practices we use here as a starting point.

Re: Cheap Panels = No Solar Trackers?

Shane Jackson wrote: »

I would say a 3 angle setup at those extremes is an absolute waste. Anything much more than 30* off due south is max.

Latitude makes a big difference too. If you're way up North like me, it's a waste because the Winter months have so little sun at such a narrow angle of exposure that the two "sideways" arrays will produce practically nothing. By the same token, as you near the equator the panels get closer to laying flat and their angle to the compass points becomes less relevant, so again no real advantage.

If someone wanted to play PV Watts with this they could examine the cumulative Watt hours for the three arrays vs. a "South-only with tracker" (PV Watts doesn't do trackers but it would be approximately a fixed South array +30% - Dave Sparks would have more info on the accuracy of this for comparative purposes). You could spend a lot of time playing with the possibilities.

At any rate, this also doesn't address the idea of splitting a large South-facing array into three parts to gain earlier charging and sustained PV output over a longer time. That is worth some examination too.