Two Axis vs One Axis vs Fixed Angle installation?

System · January 2008

I've been reading the forums for a bit now and there seem to be mixed reviews on tracking systems.

I've been looking at a few options and a few have came to light that seem cost effective for two reasons. First off, we are located in Ontario, Canada; an area that has medium-moderate snow coverage 3-4 months of the year and with a tracking system alot of the snow would slide off on a daily basis. Though this might also happen with a fixed installation (45 deg) I think it'll clear better with a tracker.

I'm looking at a couple systems, but one that caught my eye (specifically for price, and the number of installations they have) is the Lorentz system - http://www.lorentz.de Has anyone had any experience with these? or any trackers for that matter? The projected yeild in my area for a single axis 10kw array is about 15,648 kwh/year vs 16,650kwh/year with a dual axis. The cost of the single is about $1-$1.20/watt, where as most dual axis trackers are $2+ /watt.

Anyhow, I'll stop my rambling and let the elders tear my post apart :-) Cheers!

mike95490 · January 2008

Re: Two Axis vs One Axis vs Fixed Angle installation?

What's the projected yeild with NO tracker, and a fixed angle ?

System2 · January 2008

Re: Two Axis vs One Axis vs Fixed Angle installation?

11,516 kwh/year, but keep in mind - we're getting $0.42/kwh here in Ontario.

mike95490 · January 2008

Re: Two Axis vs One Axis vs Fixed Angle installation?

10kw array Tracker:

none 11,516 kwh/year

Single 15,648 kwh/year

Dual 16,650kwh/year

Not having used the estimating software, I don't know what the December vs June values are. If you are NOT using air conditioning, and have sized your 10KW array (that's pretty large, my 4.5KW takes up a huge chunk of my roof) to meet your loads for the short winter days, it should only get better in summer.

What's the price spread for the single and dual trackers ? For that same cost, can you get more PV's, or a small genset for once a week in winter ? I've heard nobody say good things about trackers after 3 years.

BB. · January 2008

Re: Two Axis vs One Axis vs Fixed Angle installation?

I think he is getting paid $0.42 per kWhr and probably pays less than $0.10 per kWhr for his power...

At least 4,000 kWhr extra per year, $0.042*4k= $1,680 per year additional revenue.

4,000 kW array, $1 per watt (over and above basic frame). $4k/$1.68k=2.4 year pay back (3x 1,500 watt array mounts)...

Replace the 4AH 12volt steering battery every few years. Probably replace the linear actuator every 5 years (just a SWAG--times three array mounts)...

-Bill

crewzer · January 2008

Re: Two Axis vs One Axis vs Fixed Angle installation?

Another configuration to consider is a south-facing array (no tilt axes) tilted up at latitude plus ~15 degrees. For your location (~43 degrees N?), the tilt angle would be ~58 degrees. This configuration substantially improves winter energy harvest over “tilt = latitude” installations, although summer harvest is reduced.

However, if a fixed-tilt system can meet December energy requirements, it can typically meet summer needs as well (except for A/C). This steeper “winter” angle also helps with snow shedding as well as rain assisted self-cleaning.

I haven’t thoroughly crunched the numbers on fixed vs. tilt installtions. However, my gut feeling is that a tilt solution probably isn’t worth the extra cost, space, and maintenance for an off-grid system, primarily because of the small improvement in December (northern hemisphere) energy harvest potential.

Trackers and utility-intertie (U-I) systems might be something else altogether. Compared to a fixed-tilt system, which is usually sized in accordance with the month with the lowest average insolation (i.e., December), a tracking system would allow for a smaller array to meet energy needs based on average annual insolation, which is invariable greater than the lowest month’s.

In other words, use the grid as the “battery bank”, sell excess energy to the grid in the summer, and buy what you need from the grid in the winter, with the goal of achieving an annual "net zero", either in Dollars or in grid-suplied energy consumption. Time-of-use (TOU) rates can make this scenario both more interesting and more complicated.

Whether the savings from a smaller array, a smaller controller (perhaps), smaller AWG wire (less array current), and reduced installation labor would pay for the tracker and associated maintenance would need to be considered.

Finally, note that battery-less (B-L) U-I systems are useless during a power outage. To prevent injury to utility workers, the required “anti-islanding” safety feature prevents a B-L U-I inverter from generating power and sending it to the grid when it’s down. At the same time, the B-L U-I inverter won’t send power into your home as it no way or balancing generation vs. demand. A U-I inverter will reconnect to the grid five minutes after grid power is restored and stable.

The comment above is not intended as a criticism of B-L U-I systems. Minus batteries, they are cost effective, more efficient, and require lower maintenance. However, I’ve come across more than just a few people who were rather astonished to learn of this "no grid, no operate" characteristic, so I believe it’s important that this issue be clearly stated and understood, especially by those who are expecting their U-I PV system to be available as a source of backup power.

HTH,
Jim / crewzer

GreenerPower · January 2008

Re: Two Axis vs One Axis vs Fixed Angle installation?

This site http://www.sunposition.net/sunposition/spc/locations.php#1 is helpful in determining the sun angle over the year to tilt your panel to get max annual yield.
GP

System2 · January 2008

Re: Two Axis vs One Axis vs Fixed Angle installation?

BB. wrote: »

I think he is getting paid $0.42 per kWhr and probably pays less than $0.10 per kWhr for his power...

At least 4,000 kWhr extra per year, $0.042*4k= $1,680 per year additional revenue.

4,000 kW array, $1 per watt (over and above basic frame). $4k/$1.68k=2.4 year pay back (3x 1,500 watt array mounts)...

Replace the 4AH 12volt steering battery every few years. Probably replace the linear actuator every 5 years (just a SWAG--times three array mounts)...

-Bill

Yea, I've crunched the numbers and we're actuallying getting the 1-axis for around $1/watt - including mounting rack. The 2-axis are ALOT more, and have more parts to break, along with a minimal increase in power yield. Not to mention the 1-axis can also be adjusted quarerly on the tilt access for even better yield.

The array we're looking at building is ONLY for power sale back to our government, and if the 4 or 5 friends I'm working with come through with their end of the cash we'll be over 100kw in total.

I keep hearing the arguement about just buying more panels, but even with our panel cost at $3.20/watt the 30-35% increase isn't exceed by buying more panels with the same money. The only real plants in our area that have fixed tilt installations are the Opti-Solar plants, but those will use thin film technologies which cost < $2/watt from what I'm told.

Take a look at the link above, these trackers seem to used alot in Europe and Asia. I'm probably going to make a trip to one of their sites prior to buying anyhow.

icarus · January 2008

Re: Two Axis vs One Axis vs Fixed Angle installation?

Scott,

I'm coming to this a bit late, but I wonder if your calcs include a estimate for greater panel output during cold weather? Also, have you included any increase for reflected snow. If you are going to locate near the Soo you might have plenty of both.

My peak output increases dramatically with both cold as well as snow reflection. My December, January output is terrible except for those rare days of full sun, but by February, with cold temps and a bit more sun I'm smoken'. My panels are fixed in about the attitude Jim (Crewser) suggests. (I do manually change them a bit in the summer. The steep angle does have the added benefit of increasing reflected gain, and it sheds snow very quickly.

Just a thought.

Icarus

BB. · January 2008

Re: Two Axis vs One Axis vs Fixed Angle installation?

Sr*w the tracking mounts and inverters... Just buy some old non-functional solar panels and bury an extension cord from the house meter to the "solar meter"... Pay $0.10 a kWh and get paid back $0.42 per kWh and keep the $0.30 spread without all that expensive and problem filled equipment to maintain....

-Bill :roll:

nigtomdaw · January 2008

Re: Two Axis vs One Axis vs Fixed Angle installation?

I bet someone somewhere is doing that, we live in a very sharp world, trouble is I never ever seem to think that way dooh .

If your tracking so many arrays all following the sun from the same point on earth, why dont you buy one tracker and mechanically link the other 50 or so arrays to gether, would be a lot cheaper no? 8)

Two Axis vs One Axis vs Fixed Angle installation?

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