Published on February 26, 2014
How to Choose and Care For Your Solar Inverter
Webinar Sponsored By:
Moderator Kathie Zipp Solar Power World Presenters Daniel Ithurburn J.S. Roy Martifer Solar Beacon Power Services
Module Level Power Electronics • Microinverters (DC to AC) o Examples: Enphase Energy, SMA, Solar Bridge, Enecsys, … • DC Optimizers (DC to DC) o Examples: SolarEdge, Tigo, …
Why? • Benefits: o o o o Shade tolerant Fault tolerant More flexibility in design Granular data & lots of it! • Costs: o The cost! o Faults are obvious*
Sizing • System Specs: o 260 W solar panels • 260W @ STC / 232.5 W @ PTC o 96.5% microinverter efficiency • Do the Math: o Max power in for max power out: • STC: 260W x 96.5% = 250.9 W AC • PTC: 232.5W x 96.5% = 224.4 W AC • Consider your location!
O&M: At a High Level • Monitoring • Preventative Maintenance o Solar panel cleaning • Unscheduled Maintenance
Monitoring • No more weather stations! • Data, Data, & more Data!
Preventative Maintenance • Little to none (depending on the technology used) o Microinverter has none o DC optimizer has some for the inverter • PM should still be performed! o o o o AC interconnections Racking Solar panels Etc.
Unscheduled Maintenance • Issues are immediately obvious! • Fault has little impact on the overall system • Truck roll is scheduled • Remote troubleshooting is possible in ~90% of cases o Truck will have necessary replacement parts
Take Aways • Benefits & Costs of operating one of these systems o Is the ease of operation worth the added upfront cost? • Maintenance of Module Level Power Electronics systems o Use the data to tailor your maintenance strategy
Choosing and Maintaining String and Central Inverters - A Designer’s Perspective
Introduction • Lead Design Engineer • Array Troubleshoot Consulting • Project Feasibility Reporting
Inverter Reliability • • • • • Failure Rate The Bathtub Curve Infant Mortality Rate Useful Life MTBF
Failure Rate The frequency with which an a engineered system fails as defined by Reliability Engineering
Bathtub Curve Infant Mortality
MTBFIs NOT the average life span of a product, but rather the inverse of the failure rate during the Useful life period.
Third Party EvaluationsAsk the Manufacturer for any reports available Use Test Data from readily available sources (ie: websites, magazines; studies) If unavailable, consider purchasing reliability testing.
Inverter Maintenance • Commissioning • Preventive Maintenance • Monitoring
Inverter Commissioning A Proper Commissioning Procedure done by a trained professional will reduce the likelihood of infant mortality of the inverter
Inverter Commissioning Torque Checks Thermal Imaging Performance Verification
Preventive Maintenance • MTBF Studies include all Preventive Maintenance and consumable parts • Follow the Maintenance Procedure in the Inverter’s Manual.
Preventive Maintenance • Recommission the Inverter • Note any abnormalities in the inverter and Repair as Necessary. • Keep a log of repairs that feed back into the inverter selection process.
Monitoring • Setup alarms to your O&M personnel using specific criteria. • Perform Spot Checks for Array Performance
Picking the Right Inverter • Environmental Constraints • Choosing a DC/AC Ratio • Inverter Efficiency • Advanced Utility Features
Environmental Constraints • Use ASHRAE to determine the design temperature • Check the spec sheet against the design temperature, note any efficiency derates at higher temperatures • Communicate with the manufacturer when working on the edges of the inverter capability
Environmental Constraints • High Humidity Environments will lead to higher corrosion rates. Consider Humidity Controllers • If an area is susceptible to flooding or high snow fall, Consider increasing the enclosure rating of the Inverter.
Choosing a DC/AC Ratio PVSYST will quickly calculate the overload losses due to inverter overload in the first year
Choosing a DC/AC Ratio • Pushing up the DC/AC Ratio often helps the overall financials of the Project in terms of ROI • Tiered Electricity Rates may reduce the need of overload losses by offsetting the initial costs with increased efficiency during high tiered months
Choosing a DC/AC Ratio • Inverter Manufacturers have a limit on how much overloading they will allow • Overloading an inverter in a high temperature environment may result in decreased performance and useful life
Inverter Efficiency • It is easy to say that given the same price and quality always choose the highest efficiency inverter • How do you compare when the costs are not the same?
Inverter Efficiency Using CEC Weighted Efficiency
Inverter Efficiency Using PVSYST
Inverter Efficiency Additional Advantage of Increased Returns after ROI has been reached for the useful life of the inverter.
Thank You References: 1) 2) Lewis, E.E. Introduction to Reliability Engineering. Hoboken: John Wiley and Sons, Inc, 1996 Print Quinn, Connor. 61673-fig. 2010. Electronic Design Europe. Graph. 2/19/2014
Questions? Solar Power World Beacon Power Services Kzipp@solarpowerworldonline.com Phone: 440.234.4531 Twitter: @SolarKathieZ email@example.com Phone: 773.354.2100 Kathie Zipp J.S. Roy Martifer Solar Daniel Ithurburn firstname.lastname@example.org Phone: 310.663.2750
Thank You This webinar will be available at www.solarpowerworldonline.com & email Tweet with hashtag #SolarWebinar Connect with Solar Power World Discuss this on EngineeringExchange.com
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