Upload
nguyennhan
View
220
Download
3
Embed Size (px)
Citation preview
Sunrun Design TrainingKey Concepts
Danny HytowitzField Technical Trainer
Field OperationsSunrun
Tuesday, January 19, 2016San Diego, CA
Intro – Sunrun Design
• Department Objectives:
‒ Create and maintain industry leading design requirements which help ensure high performing PV systems
‒ Share best practices with partners as they evolve
‒ Good designs lead to well built systems
Sunrun Design TrainingKey Concepts
Objectives
Session Objectives
• Understand Sunrun specific design requirements
• Agenda:
‒ PV basics
‒ Design requirements
• String sizing
• Overcurrent protection
• Point of connection
• Shading
• Array identification
‒ Project requirements
‒ Plan sets
Sunrun Design TrainingKey Concepts
PV Basics
PV Basics – Solar Modules
PV Basics – Solar Modules
PV Basics – Solar Modules
PV Basics – Solar Modules
PV Basics – Solar Modules
PV Basics – Solar Modules
PV Basics – Solar Modules
PV Basics – Solar Modules
PV Basics – Solar Modules
PV Basics – Solar Modules
PV Basics – Solar Modules
PV Basics – Solar Modules
Sunrun Design TrainingKey Concepts
Wiring Methods
Series Connections
• “Strings” of PV modules are electrically connected in series. This means that
the positive end of one module is connected to the negative end of the next,
so on and so forth.
• In series, the voltage increases (sums) but the current stays
constant.
• V = Voc1 + Voc2 + … + Vocx, I = Isc
Parallel Connections
• Sets of strings of PV modules are electrically connected in parallel. This
means that the positive ends of the strings are connected together and the
negative ends also connected together.
• In parallel, the current increases (sums), but the voltage stays
constant.
• V = Vstring, I = Isc1 + Isc2 + … + Iscx
Sunrun Design TrainingKey Concepts
Inverter Array Matching
Inverter-Array Matching
• Objective: to avoid power clipping at peak production times
• Sunrun allows AC watts up to 110% of the inverters nominal output.
• Max AC Power ≤ 1.10 x Inverter nominal AC Power
• How do I get DC to AC watts? Aka DC to AC derate(quick review)
• Max AC Power = (total # modules x PTC rating x inverter efficiency)
Inverter-Array Matching
Max AC Power ≤ 1.10 x Inverter nominal AC Power
Max AC Power = (total # modules x PTC rating x inverter efficiency)
Example:
(1) SMA Sunnyboy 6000 (95.5% efficient CEC)
(28) Yingli 250 (226.2 CEC or PTC rating)
1.10 x 6000 = 6,600 W
Max AC Power = (28 x 226.2 W x .955) = 6,048 W
6,048 W ≤ 6,600 W
This system works!
Page 23 – Installer Handbook
Sunrun Design TrainingKey Concepts
Module String Sizing
String Sizing – Max # of Modules
• Objective: to avoid exceeding inverter and other equipment maximum voltage rating.
Vmax = {Voc - ((25°C - record low temp°C) * Tvoc)} * # of modules in series
Vmax < Inverter max DC voltage
• Note: Tvoc must be converted to V/°C (Voc * Coeff Voc)
• Note: Temperature selection could either be “record low” for the site or ASHRAE “extreme minimum” per NEC 690.7 (2011)
• ASHRAE temperatures can be found on Solar ABC’s website
String Sizing – Max # of Modules
• RECORD LOW TEMP-
• ASHRAE temperatures can be found on Solar ABC’s website
To navigate to this:
A. Web search for (google) “solar abcs ashrae”
or
B. go to www.solarabcs.org
1. Select “Publications”
2. Select “Expedited Permit Process Report”
3. Select “Map of Solar Reference points”
• Select “Interactive Solar Reference Map”
• Enter install site City and State
• Pick the appropriate nearest reference site…
String Sizing – Max # of Modules
• Objective: to avoid exceeding inverter and other equipment maximum voltage rating.
Vmax = {Voc - ((25°C - record low temp°C) * Tvoc)} * # of modules in series
Vmax < Inverter max DC voltage
• Note: Tvoc must be converted to V/°C (Voc * Coeff Voc)
• Note: Temperature selection could either be “record low” for the site or ASHRAE “extreme minimum” per NEC 690.7 (2011)
• ASHRAE temperatures can be found on Solar ABC’s website
String Sizing – Max # of Modules
• Objective: to avoid exceeding inverter and other equipment maximum voltage rating.
Vmax = {Voc - ((25°C - record low temp°C) * Tvoc)} * # of modules in series
Vmax < Inverter max DC voltage
• Note: Tvoc must be converted to V/°C (Voc * Coeff Voc)
• Note: Temperature selection could either be “record low” for the site or ASHRAE “extreme minimum” per NEC 690.7 (2011)
• ASHRAE temperatures can be found on Solar ABC’s website
String Sizing – Max # of Modules
• A brief review of the max string sizing equation
Vmax = {Voc - ((25°C - record low temp°C) * Tvoc)} * # of modules in series
Vmax < Inverter max DC voltage
• 25°C is the STC module temperature
• Record low temp can be found several ways. weather.com select monthly averages then record low
• Extreme minimum ASHRAE numbers found on Solarabcs.org may allow more options
String Sizing – Max # of Modules
• A brief review of the max string sizing equation
Vmax = {Voc - ((25°C - record low temp°C) * Tvoc)} * # of modules in series
Vmax < Inverter max DC voltage
• Tvoc is the module Temperature coefficient multiplied by the Voc
• From the REC module data sheet this is -0.27% = -.0027
• REC265PE specifies 38.1 Voc @ STC
• Tvoc = -.0027 x 38.1 = -0.10287
String Sizing – Max # of Modules
• Example:
28 REC 265PEBLK modules wired in 2 series strings of 14modules
1 SMA Sunnyboy 6000 US inverter with
4°C record low in Los Angeles CA
Temp Coefficient Voc –0.27%/C (STC) Voc 38.1
Tvoc = (38.1 x -.0027) = -.10287 V/°C
Vmax = {38.1 - ((25°C - 4°C) * -.10287)} *14 = 563.64 V
563.64 V< 600 V
• 14 modules in series works!
• Page 20 – Installer Handbook
String Sizing – Min # of Modules
• Objective: to avoid reduced output on warm days and after modules have degraded
Vmin = {Vmp - ((25°C - (max average high temp°C + 25°C)) * Tvmp)} * # of
modules in series
Vmin > Inverter min DC MPPT voltage + 20 V
• Tvmp often needs to be based on Tvoc
• Tvmp must be converted to V/°C
• Temperature selection could either be “max average high” for the site or ASHRAE “2% high” per NEC 690.7 (2011)
• ASHRAE temperatures can be found on Solar ABC’s website
String Sizing – Min # of Modules
• Objective: to avoid reduced output on warm days and after modules have degraded
Vmin = {Vmp - ((25°C - (max average high temp°C + 25°C)) * Tvmp)} * # of
modules in series
Vmin > Inverter min DC MPPT voltage + 20 V
• Tvmp often needs to be based on Tvoc
• Tvmp must be converted to V/°C
• Temperature selection could either be “max average high” for the site or ASHRAE “2% high” per NEC 690.7 (2011)
• ASHRAE temperatures can be found on Solar ABC’s website
String Sizing – Min # of Modules
• Objective: to avoid reduced output on warm days and after modules have degraded
Vmin = {Vmp - ((25°C - (max average high temp°C + 25°C)) * Tvmp)} * # of
modules in series
Vmin > Inverter min DC MPPT voltage + 20 V
• Tvmp often needs to be based on Tvoc
• Tvmp must be converted to V/°C
• Temperature selection could either be “max average high” for the site or ASHRAE “2% high” per NEC 690.7 (2011)
• ASHRAE temperatures can be found on Solar ABC’s website
String Sizing – Min # of Modules
• Objective: to avoid reduced output on warm days and after modules have degraded
Vmin = {Vmp - ((25°C - (max average high temp°C + 25°C)) * Tvmp)} * # of
modules in series
Vmin > Inverter min DC MPPT voltage + 20 V
• Tvmp often needs to be based on Tvoc
• Tvmp must be converted to V/°C
• Temperature selection could either be “max average high” for the site or ASHRAE “2% high” per NEC 690.7 (2011)
• ASHRAE temperatures can be found on Solar ABC’s website
String Sizing – Min # of Modules
• Sunrun requires that you add 20 volts to the inverter’s minimum FULL POWER / RATED MPPT voltage! (high efficiency range)
Inverter min DC MPPT voltage + 20 V
• Example SMA 3800TL lists Rated MPPT 175-480v
• Sunrun + 20 considers this as 195-480v
• Why?
• Equipment degradation
• Small safety buffer…
• Helps reduce losses due to “on the edge” Shade, Temp etc…
String Sizing – Min # of Modules
• Example:
(28) Yingli 250 and (1) SMA Sunnyboy 6000
(2) strings of 14 modules in series
Located in Los Angeles CA (26°C)
Tvmp = (30.4 x -.0045) = -.1368 V/°C
Vmin = {30.4 - ((25°C - (26°C + 22°C)) * -.1368)} * 14 = 381.64 V
381.64 V > 250 V + 20 V
• 14 modules in series works!
• Page 22 – Installer Handbook
Stringing Concepts
• All modules in a DC series string must always face the same pitch and
azimuth.
• Strings wired or combined in parallel must have the same quantity of
modules
• If different size strings or different mounting planes are needed to
meet system size, multiple inverters OR advanced inverters with
multiple mixed or MPPT independent tracking string inputs
• Micro-inverters don’t apply to these concepts since they convert DC to
AC at the module level and are then connected in parallel.
Stringing Concepts
• Modules in each string co-planer
• (6) modules @ 270 and
(10) Modules @ 180 connected
to (1) ABB (Power-one-PVI) 3.6
• (14) modules connected to
(1) Power-one-PVI-3.0
Sunrun Design TrainingKey Concepts
Overcurrent Protection
Overcurrent Protection - DC
.
• Max Current definition 690.8 (A)(1)
Max DC current= Isc* # parallel circuits * 1.25
• When sizing DC overcurrent protection the circuits are considered “continuous” per 690.8 (B)(1)(a)
Min DC OCPD = Max DC current * 1.25
Min DC OCPD = Isc* # parallel circuits * 1.25 * 1.25
• OCPD required when combining strings. In practice fuse size should be the maximum series fuse rating allowed by the manufacturer (15 amps for most modules)
Overcurrent Protection - DC
.
• Sunrun’s strong preference is not to combine strings prior to the inverter:
‒ Easier troubleshooting and service
‒ Fuses on the roof are a potential point of failure
‒ Cost is very similar
‒ New inverters with multiple MPPT, even less value in combining strings
Overcurrent Protection - AC
.
• Max Current definition 690.8 (A)(3)
Max AC current= Inverter continuous output current rating
• When sizing AC overcurrent protection the circuits are considered “continuous” per 690.8 (B)(1)(a)
AC OCPD = Max AC current * 1.25
• Round up to nearest available trade size breaker listed in NEC 240.6
15,20,25,30,35,40,45,50,60,70,80,90,100 Amps
Overcurrent Protection - AC
.
• Example: ABB (Powerone) PVI-6000-OUTD-US
Max AC current = 6000 W/240 V= 25 A
25 amps * 1.25 = 31.25 A
Next available trade size = 35 A
• Note that this inverter manufacturer publishes a max breaker size of 35 amps
Overcurrent Protection – Point of Connection
• Standard expectations of 705.12
‒ 705.12(D)(2) Load side connection, sum of the overcurrent projection devices feeding the bus bar or conductor cannot exceed 120% of the bus bar rating
• Example: (1) PVI-6000-OUTD-US connected to 125 amp service panel feed by 100 amp main breaker
125A * 1.20 = 150A
150A – 100A = 50A
35A < 50A
• This configuration works!
• Page 25– Installer Handbook
Overcurrent Protection – Point of Connection
• Reducing the main breaker is an alternative strategy to meet the requirements of 705.12(D)(2)
‒ Perform a load analysis
‒ Example: 200amp buss bar, reduce the main to 175amps, 65 amps available for solar
• Upgrading the service panel is an additional strategy
‒ Upgrade service from 100amps to 200amps
‒ “Solar Ready” panels provide dedicated 60amp backfeed locations
Overcurrent Protection – Point of Connection
• Standard expectations of 705.12
‒ 705.12(A) Supply side connection cannot exceed service rating
• If a Supply side connection is performed, the point of connection must be protected by:
‒ Minimum 60 amp rated disconnect per 230.79(D)
‒ Disconnect must be bladed and fused
‒ Fuses/Breakers must be rated for a minimum of 22kA
• Page 27– Installer Handbook
Sunrun Design TrainingKey Concepts
Questions?