GreenMountain Engineering

IEEE PVSC 34 Paper Available

My sources tell me that Brandon and Max had a great time mingling with the "solarati" at the IEEE Photovoltaic Specialists Conference last week, and the presentation was a success!  The full paper (abstract below) is available on our Papers page.

Solar Tracker Accuracy: Field Experience, Analysis,
 and Correlation With Meteorological Conditions

B. Stafford1, M. Davis1, J. Chambers1, M. Martínez2, D. Sanchez2
1GreenMountain Engineering, LLC, San Francisco, CA, and Somerville, MA, USA
2Instituto de Sistemas Fotovoltaicos de Concentración S.A., Puertollano, SPAIN

Abstract: Tracker performance is a significant factor in the energy production of PV systems, especially concentrating photovoltaic (CPV) systems. The nonlinear relationship between CPV optic pointing accuracy and energy production means that simple metrics such as mean pointing accuracy are not sufficient for predicting performance of these systems.

Additionally, trackers are currently a significant component of system cost. Understanding the real causes of tracking errors in the field (as well as which types of errors have a less significant impact on energy production) is an important step towards the development of lower-cost tracking systems.

In this paper we present a collection of real-world data, including tracking error and corresponding meteorological data, gathered over a period of months from commercial solar trackers installed at Instituto de Sistemas Fotovoltaicos de Concentración S.A. (ISFOC) in Puertollano, Spain. We present several relevant mathematical tools for analyzing this data, and draw conclusions about the implications of tracking errors for system energy production.

Full Paper

GreenMountain to Present at PVSC 34

Breaking News! There's been an addition to the program at the IEEE 34th Photovoltaic Specialists Conference next week in Philadelphia.  Brandon Stafford will be presenting data on tracker performance in CPV field installations that was collected in collaboration with ISFOC. Below is an image of the poster and here is a link; we'll upload the paper shortly.

Tracker Accuracy: Field Experience, Analysis, and Correlation With Meteorological Conditions
Area 3: Concentrator Panels and Systems
Tuesday, June 9, 3:30 PM

Two Opportunities to See Us

Two Mountaineers will be speaking at events in the Bay Area in the next few days.  We hope you can join us for one of these engaging discussions!  On Thursday, Brian Atchley is speaking on the changing landscape of renewable energy infrastructure at a one-day seminar presented by the Society of Manufacturing Engineers, An Engineer's Guide to Green: New Rules - New Tools.  Then next Wednesday, David Hague will be participating in a panel exploring innovation and financing for clean technologies, Clean Tech Companies in Growth Mode: Challenges, Opportunities, and the Competitive Landscape in a Global Marketplace. Full details and registration information are included below.

An Engineer's Guide to Green: New Rules - New Tools
Thursday, May 21 8:30 AM - 3:30 PM
Santa Clara, CA

Clean Tech Companies in Growth Mode
Wednesday, May 27 6:30 PM - 9:00 PM
San Francisco, CA

Rooftop Test Station

Spring is here!  And for us, that means more sunny days spent running experiments and collecting data at our rooftop test station.

The "rooftop lab" has been used for many things over the years from testing CPV designs to powering a corner of the office with solar panels.  A couple of years ago, during the development of the Trac-Stat SL1, we installed a two-axis solar tracker.  The current setup includes:

• Two-axis tracker capable of handling up to 125 ft² of panels
• 12V and 24V DC power supplies
• Pyranometer, to measure solar irradiance levels
• Temperature and relative humidity data-loggers
• One or two Trac-Stat SL1 accuracy monitors

 

This test station has helped us to expedite several hardware and software projects, for both PV and CPV clients.  Our last paper on tracker accuracy characterization (PDF) includes some of the data we've collected.  This year we’re hoping to get even more use out of it with some system upgrades, including:

• Telemetry system for remote access and operation
• Pyrheliometer, for measuring direct-normal irradiance
• Spectroradiometer, to measure spectral distribution throughout the day
• And possibly a few upgrades to the tracker's stock controller (!)

Stay tuned for updates, and enjoy the weather!

Evergreen Solar Panels Receive High Performance Rating

One of our engineers just pointed out that Evergreen Solar recently received the highest rating for panel performance in the first 6 months of a one-year test being conducted by TUV Rheinland, an international test institute headquartered in Germany.

Out of 14 major brands of solar panels tested, Evergreen's produced the most power over a 6-month period.  In fact, their newest products are guaranteed to initially provide a minimum of 100% of their power rating.  This means that when you plug in a new 200 W panel in full sun it will generate 200 W of power, while the industry standard is to provide only 95-97% or 190-194 W for a 200 W panel.

Congratulations to Evergreen on this performance achievement!  You can check out their press release for more details.

The DOE and the Stimulus: Digging into the Numbers

When I broke down the $33.5 billion allocated to the Department of Energy in last month's American Recovery and Reinvestment Act it was no surprise that it provides a huge shot in the arm for the DOE's Office of Energy Efficiency and Renewable Energy (EERE). The $16.8 billion marked for EERE is a tenfold increase over their 2008 appropriation of $1.7 billion. (EERE)

David Hague also pointed out that overall federal energy spending (adjusted for inflation) has remained flat over the last twenty years. The adjusted DOE outlay only increased from $20.3 billion in 1988 to $21.9 billion in 2008. (USGPO)

We're happy to see that the stimulus package provides a much needed boost to the agency responsible for one of the most pressing issues of our time. EERE has already announced the first few funding opportunities, in the vehicle technologies program.  We'll be keeping an eye out for further announcements in the coming weeks.

Trac-Stat SL1: One-Year Anniversary

We’re extremely happy to make note that it has been one year since we launched the Trac-Stat SL1!

The demand and reception for this tracker accuracy measurement tool have far exceeded our expectations.  After a year of sales it’s now in use by companies, universities, and research institutions all over the world, including the regions shown below.  SL1 owners are using its precise measurement capabilities to develop solar trackers, CPV modules, CSP technologies, and more.

For more information about the capabilities and applications of the SL1, visit our website.

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