[Palo Alto, California USA]
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| From Palo Alto Municipal Service Center PV Trackers |
The tracker mounted Photovoltaic modules are filthy and have shading issues.
Questions emerge about design and installation compromises.
On my way back from checking out the SolFocus SF-1100 System at the Palo Alto Regional Water Quality Control Plant, I stopped by the Palo Alto Municipal Service Center (MSC) to take photos of the seven (7) Photovoltaic (PV) tracker arrays located on East Bayshore Road. My intent was to juxtapose this approach versus some purported benefits of Concentrator Photovoltaics (CPV). I was shocked to find numerous issues with the site during my brief visit.
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| From Palo Alto Municipal Service Center PV Trackers |
Dirty modules
As can be seen in the photos above and below, the PV modules are speckled with bird droppings and a tinge of dried dust. At first glance, this could be an online advertisement for the Tigo Energy Module Maximizer, a per module DC (Direct Current) MPPT (Maximum Power Point Tracking) solution, featuring an innocent looking seagull. The bird droppings and grime degrade the performance and attractive appearance of the SunPower SPR-205-BLK-U modules used on the Wattsun Dual-Axis Solar Trackers.
In reviewing my other photos (not shown), I believe the modules on the lower left corner of two trackers may have received a recent dusting. Otherwise, my guess is the modules have not been cleaned since installation.
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| From Palo Alto Municipal Service Center PV Trackers |
Obvious Shading
It doesn’t take a PV expert to notice significant tracker shading from nearby trees in the morning and late afternoon. The shading is so unsubtle, branches from two of the trees brush up against the modules and trackers towards the beginning and end of the day. The tracker I designate number seven (#7), the northern most one or to the far left in the group photo, is almost half shaded in the late afternoon. Two street lights in front of the trackers also contribute to partial shading in the afternoon.
California has a delayed summer power peak in the late afternoon and early evening, so generating power at this time is the most valuable and a key justification for dual-axis tracking.
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| From Palo Alto Municipal Service Center PV Trackers |
Installation completion date, anyone?
When was this installation completed? My hazy recollection is I first noticed the MSC trackers driving North on 101 (U.S. Route 101) last summer as a passenger during my hiatus recovery. I tried to confirm the exact date by contacting the City of Palo Alto through the Photovoltaic Project Website Palo Alto Solar, the PaloAltoGreen Program, and the City Council, but I have yet to receive a reply. I believe the City of Palo Alto response has been hampered by summer vacations and maybe furloughs (this is California) last week.
After multiple emails and phone calls, I =finally= got in touch with SPG Solar, Inc. who landed the $2,648,461 contract (CMR:445:06, FORMAL CONTRACT) with the City of Palo Alto to install PV systems at three locations as part of the PHOTOVOLTAIC DEMONSTRATION PROJECT- CAPITAL IMPROVEMENT PROGRAM PROJECT PE-05001 including the trackers and carports at the MSC. In a curious twist, SPG Solar declined to answer even a simple question “from that Ed Gunther” such as when the tracker installation was completed citing the need to “obtain written approval to release information about work we perform from all clients.” While this may well be the case, it is a convenient dodge and raises my suspicions regarding SPG Solar’s execution and latent responsibilities on the project.
PaloAltoGreen
Per the City of Palo Alto Utilities (CPAU) PaloAltoGreen Program:
In 2008, CPAU received 100% of its supply from projects that have come online since 2005, including three CPAU-funded new solar projects within its own service territory. One of these CPAU projects uses a tracking system that (follows the sun’s path across the sky) increases its capacity factor or annual output percentage to 32%, which is almost 50% better than a nearby non-tracking solar system.
At this time, the tracker benefits are nullified by the lack of ongoing maintenance cleaning the modules and trimming tree branches. In addition, drastic action must be taken to solve the gross shading issues including tree removal (I’m not a proponent) or optimizing the placement of fewer trackers on the grass strip in front of the MSC.
For the record, I applaud the City of Palo Alto’s efforts on the PHOTOVOLTAIC DEMONSTRATION PROJECT starting with a $1.4 million grant from the US Department of Energy in Fiscal Year 2003-2004 matched by the PV Partners program for a $2.8 million total. Nonetheless, I do wonder if the tracker portion of the PV Demonstration Project would have complied with Palo Alto’s current PV PARTNERS PROGRAM 2009 GUIDEBOOK.
Another question I’ve had about the PV Demonstration Project concerns the requirement for online monitoring via the City of Palo Alto website in CMR:445:06:
One goal of the DOE grant is to educate the public about solar energy. Kiosk-type signage explaining how solar energy is produced will be installed at each location. In addition, monitoring hardware will be installed at each site that will link the PV system to the City’s website. This will allow staff and the public to monitor power generation and other features from a computer. This educational component is not part of this project, but will be completed under an existing Utilities Department contract, funded by the PV Partners program.
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| From Palo Alto Municipal Service Center PV Trackers |
The kiosk signage is present at the MSC site. Perhaps the online monitoring has been held up by the City website redesign, Open House August 18 for Tracking City Results on Palo Alto See-It Site? The MSC performance data should indicate degrading power production relative to solar insolation.
In a follow up post, I’ll review the chronology of the tracker project and how I think it devolved to its current state.
Re: Birdshit, Dust, & Shadows
Behind every poor design and neglected operation you can usually find the absence of any economic downside for these sins of omission or commission. Perhaps one of the lessons of this demonstration project is that municipalities should stay out of the technology demonstration business no matter how excited they get about renewable energy.
Also, perhaps best not to confuse people more than they already are by referring to this project being about “concentrator photovoltaics”. Single or dual axis tracking with flat silicon panels concentrates nothing – it only boosts overall production by 20-35% by having the panels face the sun more directly more of the time than with fixed panels. The panels see only 1X sun….not 10X, 100X or 1000X as with real concentrated PV.
I’m sure you’ll get to the bottom of this and we’ll all be better off for it.
Good luck.
It is difficult to accept the low level of maintenance in a govt aided project in USA and I suggest entering a Long Term Service Contract(LTSC) at the time of commissioning, in all govt aided project particularly in public sector
I appreciate your efforts to get to the bottom of this Ed, but I’d consider a few items along the way (and I qualify this by saying I have no direct knowledge at all about this project, just speaking generally): First, sometimes a customer will be aware of shading issues and will plan to act on it later (maybe the city had planned to move a tree and didn’t). That certainly was the case on a project I was involved in a few years ago. As the installer that’s an element you can’t control. Secondly, cleaning is not necessarily part of a system owner’s O&M plan. A utility in the southwest owns a number of systems but as of the last time I visited their sites and spoke to them about it, they did not clean modules as a policy and simply accepted the soiling losses, which they modeled using before and after studies. I’ve seen Sunpower do the same kind of analysis.