Why you should use microinverters for commercial rooftop projects

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Before We Start

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Christopher Barrett Technical Services Manager

APsystems

Kathie Zipp Managing Editor

Solar Power World

Meet your Speakers

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Value-adding Applica/ons of Microinverters

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Proprietary and confidential. Property of APsystems.

§  Microinverters vs String, 3-Phase §  Safety and NEC compliance by design §  Systems monitoring / asset management §  Higher energy harvest §  Reliability / Uptime

§  Micro vs micro comparison, standard & 3-Phase §  Design & installation §  Reliability

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§  No high-voltage DC running across the roof (~30V DC per module, vs. strings of 600V DC or higher)

§  Safer for tenants, property managers, emergency responders

§  Microinverters comply with NEC 690.12 and 690.11


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§  Rapid Shutdown or NEC 2014 690.12 is in place to protect first responders from high voltage DC hazards on the roof that remain energized after the AC service has been shut-off in PV systems.

§  NEC 690.12 specifically states that: PV System Circuits installed on or in buildings shall include a rapid shutdown function that controls DC conductors as follows:

1.  Requirements for controlled conductors shall only apply to PV system conductors of more than 5 feet inside a building or 10 feet from a PV array.

2.  Controlled conductors shall be limited to not more than 30 volts and 240 volt-amperes within 10 seconds of shutdown.

3.  Voltage and power shall be measured between any two conductors and between any conductor and ground.

4.  The rapid shutdown initiation methods shall be labeled in accordance with NEC 690.56(B).

5.  Equipment that performs the rapid shutdown shall be listed and identified.


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§  Microinverters inherently [by design] meet the rapid shutdown requirement without the need to install additional costly equipment.

§  When the AC utility is not present, the microinverter performs the rapid shutdown function in approximately 100 milliseconds, 100 times faster than the required 10 seconds required per code.

§  Microinverters are installed directly underneath solar modules, so all low voltage < 30VDC wiring is not accessible to the first responders eliminating any hazard.

§  In regards to APsystems microinverters, there are no DC conductors energized more than 5 feet in length inside a building or more than 10 feet from a PV array.

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§  Module-level monitoring – can identify performance issues at module level

§  Improved asset management – which units are underperforming, where to deploy resources

§  Maintenance scheduling


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§  Microinverters minimize effects of: §  Shading §  Module degradation §  Module

contamination; leaves, soiling, even bird droppings

§  Results in improved energy harvest


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§  Typical Microinverter will turn on and start to produce power after the module provides ~21Vdc

§  Typical String inverters will only turn on and start to produce power after the string of modules provides ~200Vdc

§  Conclusion: Microinverters will start earlier and work later than string inverters, increasing overall energy harvest.


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§  No single point of potential failure – one component failure won’t take the entire system offline

§  Wireless Zigbee Mesh communication – when one microinverter can’t reach the gateway, it can communicate through its neighbor to relay information

§  25-year warranty option vs. 10-year warranty for many string inverters

§  Microinverter technology has proven itself in challenging environments


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§  Microinverter testing and certifications are as rigorous as those of string inverters

§  Test performed based on standards

§  IEC-61215 - set of specific test sequences, conditions and requirements for the design qualification of PV equipment (humidity freeze, damp heat, thermal cycle)

§  NEMA-6 – an operational test submerged under >1 meter of water for one hour

§  UL-1703 - covers flat-plate photovoltaic modules and panels intended for installation on or integral with buildings

§  IEC-62093 – a defined set of accelerated tests to identify potential reliability weaknesses in PV equipment

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New innova/ons compared to industry standard microinverters


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1:1 – Serves 1 module



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§  Simple and fast engineering design on front end

§  Integrated ground §  Faster installation process §  Trunk and daisy-chain AC wiring

options


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§  1:4 ratio §  True three phase 120Y/208V and 277Y/480V §  Phase balance completed inside microinverter §  Line voltage phase monitor built-in

§  1:2 ratio §  Single phase inverter which can be used on 120Y/208V service §  Phase balance by installer via three, two pole breakers


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Single Three two pole

Three Two three pole

A B C A B C

A B C A B C

YC1000

YC1000 YC500

YC500

YC500

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§  Multi-module microinverters have improved reliability over standard 1:1 micros due to: §  1:2 and 1:4 Microinverter configurations reduce overall part count §  Fewer units installed = fewer potential failure points §  APsystems incorporates the use of a Field-Programmable Gate Array

(FPGA) in all inverter designs for greater reliability, future-proof flexibility §  APsystems has incorporated oversized film and aluminum electrolytic

capacitors for reliable power conversion (low power consumption / highly de-rated components)


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§  Location: Fresno, Calif.

§  Installer: Valley Unique Electric/Solar Universe

§  Microinverters: APsystems YC1000 true 3-phase

§  No. of microinverters: 429

§  Modules: SunEdison 320W

§  No. of modules: 1,760

§  System capacity: 529 kW

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§  Location: Bainbridge Island, WA

§  Installer: A&R Solar



§  Modules: Solarworld 280W

§  No. of modules: 176

§  System capacity: 42kW


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§  Location: Seattle, WA

§  Installer: Artisan Electric



§  Modules: Talesun 240W

§  No. of modules: 30

§  System capacity: 7.2kW


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§  Microinverters

§  Eliminate exposure to dangerous high voltage DC

§  Eliminate Rapid Shutdown concern & the risk of fire from arcing

§  Don’t require special / expensive DC switchgear

§  Improve energy harvest

§  Improve systems monitoring and management

§  Can be added easily in the future

§  Multi-module microinverters

§  Reduce installation time

§  Reduce potential failure points


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Kathie Zipp Managing Editor

Solar Power World [email protected]

Questions?

Christopher Barrett Technical Services Manager

APsystems [email protected]

@SolarPowerWorld @APsystemsSolar

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