Does your Commercial Rooftop Project need a PV Booster?

Dual-axis PV (Photovoltaic) tracking for Commercial and Industrial Rooftops.

Edisun Microgrids, Inc., an Idealab company, launched the PV Booster dual-axis tracker solution for commercial and industrial (C&I) rooftops in advance of Solar Power International (SPI 2016).  Edisun’s basic PV value proposition is to “Boost Project Economics by 20%”.  On the first day of SPI, I happened upon the PV Booster booth only to find Edisun Microgrids CEO and Idealab founder Bill Gross pitching the technology and product.

PV Booster photo IMG_2291-imp_zpsmd8vvjs6.jpg

After visiting the booth a few times and reviewing the PV Booster Case Studies, I submitted the below questions to Edisun, and they were kind enough to respond over the weekend after SPI. Here is the dialog in question and answer format with the only edits to correct my “dual-axis” and “single-axis” PV tracker jargon.

Q: Why dual-axis instead of single-axis tracking?

Edisun: We use a full dual-axis tracker instead of single-axis to capture the maximum boost in annual power by adding the second axis.

The reason we can do this is we have solved for the challenges posed by the wind. A single-axis tracker pivots the panels in the center so they can track East and West for early morning and late afternoon boost. However, that means the panel is up high in the wind stream, and would not be able to survive a rooftop mount situation because of the torque-load placed on the roof. On the ground, that’s easy since it’s solved by putting a pole deep into the ground. On the roof, that deep anchoring is not possible, and the roof is not strong enough to handle that. As for the second axis on the ground, if conventional trackers were to add the second axis it would have to move the massive structure altitudinally and economics would not pencil out.

We invented a new method of making a dual-axis tracker that pivots the panel from the FRONT edge and not from the center.  That means PV Booster captures the altitude changes of the sun PLUS retracts the module to even lower on the roof than a stationary 10-degree rack.

So, the second axis not ONLY gives a boost in annual energy, but it makes the commercial rooftop trackers possible for the first time because we can retract completely flat in winds above 50 mph.

Q: How does PV Booster become bankable?

Edisun: PV Booster™ will be securing independent third-party engineering and performance verifications.  For our first customers we will work with a partner or provide direct project finance so that our customers will pay via PPA and not take any risk on our product.

Q: What is the PV Booster warranty? As a startup with a limited track record, how do you guarantee spares and qualified maintenance for 20-25 years?

Edisun: 10 year with extended warranty available. We plan to back the warranty as needed with third-party warranty insurance.

Q: What is the basis for the O&M (Operations and Maintenance) PV Booster delta of $7.5/kWp?

Edisun: We have put great engineering effort into creating O&M that approaches fixed-tilt. First, our system has fully distributed controls, so there is no single point of failure. Unlike other tracking systems that gang 100’s or sometimes even 1000’s of panels together, we have a separate microprocessor, sensor, and controls for EACH PV panel, so that out of a thousand panels, if one or two fail, then the other 998 will work perfectly and unaffected. In addition, if 2 out of 1,000 fail, those two panels still produce power, just not with the 31% annual boost. Since our warranty covers that loss in energy production, there should be no O&M to fix those two units, because our warranty will pay out those funds.

To further increase reliability we have eliminated the two things that fail the most in trackers – gearboxes and motor brushes. We designed a unique drive that is direct drive (the only tracker in the world with no gearbox) and with brushless servo motors (no brushes to wear out). Our motors are rated for well over 1 billion cycles, which would represent 1000’s of years of PV Booster operation. The motors and mechanisms have been tested in harsh environmental chambers for more than 30+ years of lifetime with no failures.

As a result, our testing shows that there will be minimal difference in O&M versus fixed-tilt. That said, in order to be conservative in our case studies, we added 50% to typical O&M costs as a reserve.

Q: Is reliability data available? What failures have been observed during development?

Edisun: We have more than 1,000,000 tracking hours tested so far with no failures.  We have not yet seen a mechanical, electrical, or wear failure of any kind in all of our testing to date.

PV Booster 2-axis commercial rooftop tracker photo IMG_2294-imp_zps3acisia7.jpg

Q: I observed the cabling to be a potential point of failure.

Edisun: PV Booster’s cabling approach is similar to conventional fixed-tilt systems. Cabling and connector vendors are all UL approved.

The tracker movement flexes the cable bundle +/- 90 degrees once per day. We have run tests of more than 50 years of cable flexing with no wear or degradation, because we have a radius of curvature of the bundle that is well below the stress point of the wires.

Q: From the case studies, the energy density of PV Booster per roof area is lower than fixed. What inputs do you have from local governments nationwide about added PV Booster design constraints for permitting?

Edisun: Our energy density on rooftops is approximately 33% less than more densely packed PV panels on fixed racks. However, we more than make up for that with the superior economics. Because of the spacing, we have a lighter load on rooftops of only about 2 pounds per square foot before ballast.

Our product must comply with the same PV standards (UL and ASCE in the U.S.) and must be installed to local building and fire codes, which we do.

Q: Does PV Booster stow itself flat if winds are excessive?

Edisun: Yes, PV Booster stows automatically when the wind is above 50 mph and has a backup system for doing so.

Q: How does PV Booster wake up in the morning?

Edisun: PV Booster wakes up automatically in the morning based on a light sensor in each unit that automatically detects when the morning light is sufficient. (These sensors keep each module optimally pointed at the sun all day.)

Q: Is it Grid connected or does it begin operation when the morning sun is sufficient?

Edisun: PV Booster is grid connected, but also has its own integrated UPS to continue tracking or to stow if the grid fails. In addition, if a tracker loses connectivity it regresses to a stowed position until connectivity is restored. (Note that it would still produce as-if it were a flat PV panel.)
PV Booster provides tangible cost savings to C&I customers subject to Time-of-Use (TOU) electricity rates by generating more power during peak rate periods especially at the end of the normal workday. However, C&I customers seeking to maximize rooftop MegaWatt-hour (MWh) power generation regardless of timing might prefer to stick with a fixed tilt system.

Going beyond the apples to apples PV Booster Case Studies, I would recommend using higher efficiency monocrystalline PV modules and DC optimizers with PV Booster. Besides attracting dirt and debris, roofs are a favorite hangout for birds and their droppings.

I should have posted this last Sunday, but I was trying for a better placement.

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