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Renewable and Emerging Generation Technology Overview Greg Ball – SolarCity Lee Kraemer – First Solar
Renewable and EmergingGeneration Technology Overview
Greg Ball – SolarCity
Lee Kraemer – First Solar
Agenda
¾ Introduction to PV Plants– Systems Overview– Design Considerations– Safety Considerations
¾ NEC 691 Overview – Large Scale PV
¾ NESC Code Sections that are Relevant to DER
¾ Summary
2
PV System Types - Residential
3
PV System Types - Commercial
4
PV System Types – Utility Scale
5
PV Growth Trend
6
0
2000
4000
6000
8000
10000
12000
14000
16000
2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 Projected
Yearly US Solar Installations MWdc
Residential Non Residential Utility CSP
*Data Reported by GTM Research and Solar Industries Energy Association http://www.seia.org/research-resources/solar-industry-data
Share of New Generating Capacity
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0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
2010 2011 2012 2013 2014 2015 2016 Q1
Solar Wind Natural Gas Coal Other
*Data Reported by GTM Research and Solar Industries Energy Association http://www.seia.org/research-resources/solar-industry-data
Workers Employed by Industry
8
0
50000
100000
150000
200000
250000
2010 2011 2012 2013 2014 2015
Solar Coal Mining Oil and Gas Extraction
*Data Reported by GTM Research and Solar Industries Energy Association http://www.seia.org/research-resources/solar-industry-data
Falling Prices Driving Demand
9
$-
$1.00
$2.00
$3.00
$4.00
$5.00
$6.00
$7.00
$8.00
2009
2010
2011
2012
2013
2014
2015
2016
$/W Installed
$-
$1.00
$2.00
$3.00
$4.00
Residential Commercial Utility Scale
Q2 2016 Quoted PV Prices
PV Module Inverter
BOS Direct Labor
Engineering S.C., Overhead, Margin
*Data Reported by GTM Research and Solar Industries Energy Association http://www.seia.org/research-resources/solar-industry-data
Utility Scale PV in Context
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¾ Large areas
¾ Low power density
¾ Generation is distributed
¾ Power electronic converters – no rotating
machines– quiet!
¾ Trending to smaller plants (e.g. 50 MW)
150 MW PV Plant 1.4 GW
1 GW
Combined Cycle Natural Gas
4 GW Nuclear
Power Plants Near Phoenix, AZ
~ 2 miles
PV Plant Design Basics¾ Series/parallel connected PV
modules – 100-400 Watts each (typ)– 25k-100k per 100 MW
¾ 1,000-1,500 Vdc Arrays– < 10 Amp “strings”
¾ Inverter stations– Inverters 1-4 MW– MV transformers
¾ MV collection system (34kV)– Usually underground
¾ Plant substation– e.g. 34kV/230 kV
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PV Plant Safety ConsiderationsDC Array Circuits
¾ Wire management - miles of exposed cable within arrays
¾ Combiner boxes– Multiple parallel sources– Opposite of dist. panels
¾ Fault protection– Limited short-circuit current– Forward fault current not protected
¾ Leakage current in large arrays– Isolation resistance monitoring– Ground fault detection sensitivity
¾ Grounding and equipotential bonding– Lightning protection
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PV Plant Safety ConsiderationsOperational Safety
¾ Step and touch potential insignificant relative to T&D substations– Low power density
¾ Arc flash at combiner panels– Parallel feeds in both directions– But manageable
¾ Aging wiring and components– Long life expectations in harsh environments
¾ Increasing leakage current from aging arrays
¾ Switch operations– Breaking dc current, infrequent use
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PV Interconnection and Grid Impact¾ Renewable resource intermittency
– Variable production with cloud cover– Can control ramp up, but not ramp down– Forecasting and storage mitigation
¾ Reactive power support– Use of inverter capacity for VAR control– Plant controller– Volt/Var and Frequency/Watt modes
¾ Voltage and frequency ride through capability– Traditionally required to disconnect
¾ Anticipate more use of storage in future
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Courtesy: Perez, Hoff, Dise, Chalmers & Kivalov
NEC 691 – Large Scale PV
¾ 690.1 Scope. This article applies to solar PV systems, other than those covered by Article 691, including the array circuit(s), inverter(s), and controller(s) for such systems. [See Figure 690.1(a) and Figure 690.1(b).] The systems covered by this article may be interactive with other electrical power production sources or stand-alone or both, and may or may not be connected to energy storage systems such as batteries. These PV systems may have ac or dc output for utilization.
¾ Informational Note: Article 691 covers the installation of large-scale PV electric supply stations.
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Key Provisions of 691 - Scope
¾ 691.1 Scope. This article covers the installation of large-scale PV electric power production facilities with a generating capacity of no less than 5000 kW, and not under exclusive utility control.
– Informational Note No. 1: Facilities covered by this article have specific design and safety features unique to large-scale PV facilities and are operated for the sole purpose of providing electric supply to a system operated by a regulated utility for the transfer of electric energy.
– Informational Note No. 2: Section 90.2(B)(5) includes information about utility-owned properties not covered under this Code. For additional information on electric supply stations, see ANSI/IEEE C2-2012, National Electrical Safety Code.
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Key Provisions of 691 - Definitions
¾ Electric Supply Stations. Locations containing the generating stations and substations, including their associated generator, storage battery, transformer, and switchgear areas.
¾ Generating Station. A plant wherein electric energy is produced by conversion from some other form of energy (e.g., chemical, nuclear, solar, wind, mechanical, or hydraulic) by means of suitable apparatus.
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Key Provisions of 691 – Special Provisions
¾ Electrical circuits and equipment shall be maintained and operated only by qualified personnel.
¾ Access to PV electric supply stations shall be restricted by fencing or other adequate means in accordance with 110.31. Field-applied hazard markings shall be applied in accordance with 110.21(B).
¾ The connection between the PV electric supply station and the system operated by a utility for the transfer of electrical energy shall be through medium- or high voltage switch gear, substation, switch yard, or similar methods whose sole purpose shall be to safely and effectively interconnect the two systems.
¾ The electrical loads within the PV electric supply station shall only be used to power auxiliary equipment for the generation of the PV power.
¾ Large-scale PV electric supply stations shall not be installed on buildings.
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Key Provisions of 691 – Engineered Design
¾ 691.6 Engineered Design. Documentation of the electrical portion of the engineered design of the electric supply station shall be stamped and provided upon request of the AHJ. Additional stamped independent engineering reports detailing compliance of the design with applicable electrical standards and industry practice shall be provided upon request of the AHJ. The independent engineer shall be a licensed professional electrical engineer retained by the system owner or installer. This documentation shall include details of conformance of the design with Article 690, and any alternative methods to Article 690, or other articles of this Code.
¾ 691.7 Conformance of Construction to Engineered Design. Documentation that the construction of the electric supply station conforms to the electrical engineered design shall be provided upon request of the AHJ. Additional stamped independent engineering reports detailing the construction conforms with this Code, applicable standards and industry practice shall be provided upon request of the AHJ. The independent engineer shall be a licensed professional electrical engineer retained by the system owner or installer. This documentation, where requested, shall be available prior to commercial operation of the station.
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Key Provisions of 691 – Details
¾ 691.8 Direct Current Operating Voltage. For large-scale PV electric supply stations, calculations shall be included in the documentation required in 691.6.
¾ 691.9 Disconnection of Photovoltaic Equipment. Isolating devices shall be permitted to be more than 1.8 m (6 ft) from the equipment where written safety procedures and conditions of maintenance and supervision ensure that only qualified persons service the equipment. Buildings whose sole purpose is to house and protect supply station equipment shall not be required to comply with 690.12.
¾ 691.10 Arc-Fault Mitigation. PV systems that do not comply with the requirements of 690.11 shall include details of fire mitigation plans to address dc arc-faults in the documentation required in 691.6.
¾ 691.11 Fence Grounding. Fence grounding requirements and details shall be included in the documentation required in 691.6.
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NESC Key Sections to Emerging Technologies
¾ Section 1 – Scope and Application
¾ Section 2 – Definitions (dozens)
¾ Section 9 – Grounding
¾ Part 1. Safety Rules for the Installation and Maintenance of Electric Supply Stations and Equipment– Section 11 - Protective Arrangements in Electric
Supply Stations (Recent Fence Grounding IR submitted for PV Systems)
– Section 14 – Storage Batteries – Section 15 – Transformers and Regulators– Section 16 – Conductors– Section 17 – Circuit Breakers, Reclosers, Switches,
and Fuses– Section 18 – Switchgear and Metal-Enclosed Bus
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¾ Part 2. Safety Rules for the Installation and Maintenance of Overhead Electric Supply and Communication Lines
¾ Part 3. Safety Rules for the Installation and Maintenance of Underground Electric Supply and Communication Lines
¾ Part 4. Work Rules for the Operation of Electric Supply and Communications Lines and Equipment
Conclusion
¾ Renewable Energy is becoming has become mainstream energy
¾ NESC needs to include provisions for renewables to ensure the safe construction, operation and maintenance of renewable generating assets
¾ Alignment with certain aspects of 691 is a good starting point for the 2022 code– There are many other opportunities to change the code to provide improved safety
for utility scale renewables
¾ Close cooperation with NEC will be very valuable in improving the Code
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Contact Information
Lee Kraemer
First Solar28101 Cedar Park BlvdPerrysburg, OH 43551T: 419-662-6206
www.firstsolar.com
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Greg Ball
SolarCity161 Mitchell Blvd.San Rafael, CA 94903T: 415-915-4943
www.solarcity.com
