Hello from Tucson: PV newbie

[posplayr]

Apparently my new idea is called a Tip - Tilt Tracker.

https://en.wikipedia.org/wiki/Solar_tracker#cite_note-25

Tip–tilt[edit]

Other such TTDAT trackers have a horizontal primary axis and a dependent orthogonal axis. The vertical azimuthal axis is fixed. This allows for great flexibility of the payload connection to the ground mounted equipment because there is no twisting of the cabling around the pole.

Field layouts with tip–tilt dual axis trackers are very flexible. The simple geometry means that keeping the axes of rotation parallel to one another is all that is required for appropriately positioning the trackers with respect to one another. Normally the trackers would have to be positioned at fairly low density in order to avoid one tracker casting a shadow on others when the sun is low in the sky. Tip-tilt trackers can make up for this by tilting closer to horizontal to minimize up-sun shading and therefore maximize the total power being collected.[24]

The axes of rotation of many tip–tilt dual axis trackers are typically aligned either along a true north meridian or an east west line of latitude.

Given the unique capabilities of the Tip-Tilt configuration and the appropriated controller totally automatic tracking is possible for use on portable platforms. The orientation of the tracker is of no importance and can be placed as needed.[25]

Like this one it does not have to violate it's designated horizontal foot print. My design tries to reduce the cost of what this one will cost.

http://konzasolar.com/

[sensij]

I don't understand. A typical 60 cell panel is around 17.5 sq ft. 10x10 = 100 sq ft, so you are designing around the equivalent of 5.7 60 cell panels... let's say 6. Even 6 * 300 W = 1800 W, which is too small for most string inverters, so you must be using micros.

When I run PVWatts on this, 1800 W in Tuscon might produce something close to 3500 kWh annually on a fixed roof with excellent orientation and no shade (See this system on PVOutput.org for actual data, consistent with PVWatts model). I'm seeing increases in PVwatts of up to 44% with 2-axis tracking, around 1500 kWh.

Under the standard TEP rates of around $0.13/ kWh in the highest tier, including PPFAC, that is around $195 of energy.

To get that same improvement from additional panels on a fixed roof, you need another 800 W, which could cost $2500 installed.

So, the economic benefit of the system relative to roof mount panels = $2500 - (BOM costs) - (value of energy lost to operate tracking) - (maintenance costs) - (engineering costs, since no rubber stamp above 8" from roof). It doesn't look like a life changing kind of number to me.

All this, to chase about $200 / year in actual cost avoided.

[solarix]

OP obviously has his heart set on inventing a new tip-tilt tracker. Let him do what he wants... He will find out the hard way that it doesn't make sense.

[SunEagle]

OP obviously has his heart set on inventing a new tip-tilt tracker. Let him do what he wants... He will find out the hard way that it doesn't make sense.

But if the OP can design a cost effective tracker for flat roof installations he may be onto something.

While all of the historical data shows that tracking on small scale pv arrays is not economically smart there might be new technology that proves the old can be cost effective.

The is a company up in Mass that has a flat roof tracking system although it is a single axis the principal and hardware is very basic and seems not expensive to install or maintain. Still waiting to see how that technology progresses.

I am interested in the OP's results and hopes he doesn't go in too much debt proving his design works.

[J.P.M.]

FWIW, I'd respectfully suggest the OP may also benefit from more experience coupled with a bit more mechanical engineering.

[posplayr]

I don't understand. A typical 60 cell panel is around 17.5 sq ft. 10x10 = 100 sq ft, so you are designing around the equivalent of 5.7 60 cell panels... let's say 6. Even 6 * 300 W = 1800 W, which is too small for most string inverters, so you must be using micros.

When I run PVWatts on this, 1800 W in Tuscon might produce something close to 3500 kWh annually on a fixed roof with excellent orientation and no shade (See this system on PVOutput.org for actual data, consistent with PVWatts model). I'm seeing increases in PVwatts of up to 44% with 2-axis tracking, around 1500 kWh.

Under the standard TEP rates of around $0.13/ kWh in the highest tier, including PPFAC, that is around $195 of energy.

To get that same improvement from additional panels on a fixed roof, you need another 800 W, which could cost $2500 installed.

So, the economic benefit of the system relative to roof mount panels = $2500 - (BOM costs) - (value of energy lost to operate tracking) - (maintenance costs) - (engineering costs, since no rubber stamp above 8" from roof). It doesn't look like a life changing kind of number to me.

All this, to chase about $200 / year in actual cost avoided.

I like these calculations, they are a little more direct.

50% of 1350 ft^2 at 15 watts / ft^2 gives me a 10KW capability without tracking. Figure 13KW with tracking.

What I am exploring is the comparative cost to gain 3Kw (a 30% increase of production for tracking) using fixed v.s. tracking. Using a $3 kW Installed (AZ is cheaper) that is $9K. You still have to pay for the increased inverter capacity and wiring capacity which for discussion might be 20% of the installed cost. So we now have a top line number for break even analysis $7200 to mobilize about 675 ft^2 of panels or 36 panels nominally. If there is a 40% gain from tracking, then we are talking about 80% of $12K = $9.6K.

It appears that I'm close to meeting the basic zoning requirements and the waiver for what would otherwise be fixed solar installs. The 4lbs/ft^2 might be exceeded so a structural analysis may in fact be required. I posted the tip-tilt link because other readers here had assumed I was describing and azimuth tracker. Now that I see horizontally oriented trackers exist, I further disclosed that that is the basic form of tracker I envisioned also for a low cost solution.

In this 10'x10' configuration we would have 6 dual axis trackers which would allow for $1200 and $1600 per tracker for 30% and 40% gains respectively. Cost of actuators and servo controllers I'm looking at are probably about $300 (for a single install) and however much it costs to build and install the structure. On the low side it might only be $900 available to build a structure and maintain the system which is essentially replacement cost of servos and electronics. On the high side $1300 would be available for break-even.

To my mind, it appears that it is possible to build and install a tracking system that will yield the same if not better Production Cost Efficiency (PCE) as a fixed install. I would define that PCE as Kw-Hr Production/ Total Life Cost. This is apples to apples comparison but without all of the complexities required to calculate ROI or payback periods.

I fully realize that if you are at simply break even and costs are a wash, with the uncertainties of trying to keep something running(moving) on your roof for 25 years without breaking down every few years the fixed install is a slam dunk. I certainly do not envision house after house in Orange or SD counties having tracking mounts on top of their roofs.

Certainly the justification for making an ever cheaper solar panel more efficient falls off as their price plummets. However, as I see the market today, the cost to install a tracking system (which are mostly ground mount) is generally always higher than a fixed mount. Regardless even at today's panel price point, it appears a tracker could be competitive (PCE) and for certain situations perhaps preferable to a fixed mount system. This last part is really the remaining question.

[posplayr]

OP obviously has his heart set on inventing a new tip-tilt tracker. Let him do what he wants... He will find out the hard way that it doesn't make sense.

Thanks you.

[inetdog]

FWIW, I'd respectfully suggest the OP may also benefit from more experience coupled with a bit more mechanical engineering.

One major difference between a tip-tilt mount and an azimuth-elevation mount is that it is harder to calculate the control inputs to point to a particular piece of sky and you may need to go around some limit points of travel in getting to the next sun-following point.
Automated control using shaded photocells and amplifiers may still work OK as long as no travel constraints affect the sun path tracking.

[posplayr]

But if the OP can design a cost effective tracker for flat roof installations he may be onto something.

While all of the historical data shows that tracking on small scale pv arrays is not economically smart there might be new technology that proves the old can be cost effective.

The is a company up in Mass that has a flat roof tracking system although it is a single axis the principal and hardware is very basic and seems not expensive to install or maintain. Still waiting to see how that technology progresses.

I am interested in the OP's results and hopes he doesn't go in too much debt proving his design works.

If you have a link to the other companies website I would be very interested.

I have been working on this concept for a full two weeks I would say, so there are still plenty of questions. The design leverages some other technology that I'm already plan to and have developed. For me the costs to maintain are minimal, the question is can it be made simple enough for others to install and use. Doing something one off and doing something reproducible are two different things.

I would install a system for the same reasons that any solar system would be to reduce long term energy costs. So to the extent there is debt involved it would be about the same. I'm sure there are some who would envision a collapsed roof and cracked glass as the results of the experiment. While I guess anything is possible, we are talking about following a legal permitting process and having enough enginnering done to minimize the possibility of anything catastrophic happening.

[posplayr]

One major difference between a tip-tilt mount and an azimuth-elevation mount is that it is harder to calculate the control inputs to point to a particular piece of sky and you may need to go around some limit points of travel in getting to the next sun-following point.
Automated control using shaded photocells and amplifiers may still work OK as long as no travel constraints affect the sun path tracking.

I like harder, if weeds out the riff raff.

[posplayr]

FWIW, I'd respectfully suggest the OP may also benefit from more experience coupled with a bit more mechanical engineering.

I'll file that with your other recommendations.

[inetdog]

Sadly, stuck in the mud AHJs can sometimes also guarantee that nothing spectacularly good will happen either.

[SunEagle]

If you have a link to the other companies website I would be very interested.

I have been working on this concept for a full two weeks I would say, so there are still plenty of questions. The design leverages some other technology that I'm already plan to and have developed. For me the costs to maintain are minimal, the question is can it be made simple enough for others to install and use. Doing something one off and doing something reproducible are two different things.

I would install a system for the same reasons that any solar system would be to reduce long term energy costs. So to the extent there is debt involved it would be about the same. I'm sure there are some who would envision a collapsed roof and cracked glass as the results of the experiment. While I guess anything is possible, we are talking about following a legal permitting process and having enough enginnering done to minimize the possibility of anything catastrophic happening.

I will look for the article. I thought it was in one of my electronic magazines which I get at work which provides some of the latest Newscasts on RE projects around the world.

I think it is something called "renewablesbiz".

[posplayr]

Sadly, stuck in the mud AHJs can sometimes also guarantee that nothing spectacularly good will happen either.

It seems there are still plenty of people working on tracking.

http://solarprofessional.com/articles/products-equipment/racking/pv-trackers

http://www.renewablesbiz.com/blog/15/06/amplified-demand-solar-trackers-boost-market-growth-middle-east-and-africa

[J.P.M.]

I'll file that with your other recommendations.

As usual, take what you want, scrap the rest.