Low Cost Plug and Play Solar Photovoltaics for Residential Households. Dr. David Lubkeman FREEDM Systems Center North Carolina State University

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1 1 Low Cost Plug and Play Solar Photovoltaics for Residential Households Dr. David Lubkeman FREEDM Systems Center North Carolina State University

2 2 Acknowledgement Acknowledgment: This material is based upon work supported by the Department of Energy under Award Number DE-EE Disclaimer: This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.

3 3 Outline Residential PV System Installation Trends Plug and Play (PnP) Initiative PnP General Requirements NCSU PnP System Future Work

4 Installation (MWdc) 4 PV Installation Trends PV Installations by Market Segment, Residential Non-Residential Utility Increase in PV Installations over past 3 years for both Utility and Residential scale. Not shown, but Residential installs surpassed Commercial in Q Source:

5 Installed Price ($/Wdc) 5 PV System Pricing Trends Average Installed Price by Market Segment Q Q Utility PV system price declined by nearly 50% since Residential PV system price declined by about 30% in same time period. 0 Q Q Q Q Utility Residential

6 System Cost ($/W) 6 Cost Breakdown for Residential PV Total PV system price and SunShot target for 5kW residential PV $6.60 $5.22 $ SunShot 2020 Target Other Soft Costs Permitting, inspection, and interconnection Installation Labor Customer Acquisition Soft costs are substantial percentage of residential system cost. Soft cost includes sales tax, supply chain, installer profit, indirect costs. SunShot goal to substantially reduce soft costs. Source: Benchmarking of Non-Hardware Balance-of-System (Soft) Costs for U.S. Photovoltaic Systems, Using a Bottom-Up Approach and Installer Survey, NREL/TP-6A

7 7 Residential PV System Layouts Central Inverter PV panels connected to racking systems involving roof penetrations. AC or DC wiring from roof to service panel. Addition of circuit to existing service panel. Micro Inverter

8 8 Plug and Play PV Reduce soft costs by designing: Simple mechanism for attaching PV panels to roof, preferably avoiding roof penetrations. Lightweight roof modules. DC and AC wiring connections made by plug and play cable kits. System interconnects to household service similar to an appliance plugin without modifying household wiring. Elimination of need for AHJ Inspection. Automation of Utility Interconnection. Enhanced Safety Features. Metrics are $/Wdc, Time to acquire, Time to install, Skill level of installers

9 9 Code Requirements Category Equipment Specifications Cabling Protection Protection Protection Operations Requirement Proper listings for all DC and AC equipment and connection boxes Adequate wire size and weather-rated insulation Proper listings and ratings for DC and AC overcurrent protection AC and DC ground fault protection DC Arc Fault Detection for voltages of 80 V or greater Rapid shutdown, AC and DC systems deenergized on demand

10 10 AHJ Permit & Inspection Requirements Category Plans Listings Installation Cabling Grounding Signs and Labels Requirement Site Plan, One-Line Diagram, Attachment Details PV panels listed to UL Standards, Inverters listed to UL Standards Installed system (equipment, wiring, location, etc.) matches approved plans Proper cable routing, cable protection, use of strain reliefs and attachment at minimal intervals Equipment (modules, inverter, racking) grounded in accordance with manufacturer instructions Proper markings on disconnects, conduits, raceways, etc

11 11 Interconnection Requirements Category Plans System Location, Size and Configuration Protection Protection Grid-Tie Requirement System built to AHJ approved requirements Relevant data provided to utility IEEE 1547 Compliant Anti-Islanding Protection AC Current Limiting Screens for interconnection passed: Feeder DG limit, customer transformer capacity, customer service capacity

12 12 Installation Requirements Category Installation Wiring Configuration Commissioning Requirement Lightwide modules easily carried up to roof No field wiring required, system plugs in like an appliance System self configures once all modules are interconnected together System preforms self-diagnostics, produces report and does not operate if diagnostics fail and a fault condition is detected

13 13 New Plug and Play Features Feature Category Present Systems Plug and Play System Power Electronics Switch/Fuse Holders Standards Household Connection Single inverter connected to high-voltage dc source Separate switch/fuse boxes UL approved individual components Modification of household wiring Multi-Port Inverter Building Blocks Integrated into building block structure UL approved subsystems Installation of external plug-in port for PV System Inspection Utility Interconnection On-site Inspection needed to verify system wired properly Maximum Peak Power Tracking (MPPT) compliant to existing IEEE 1547 standard Self-diagnostics used to verify system wired correctly and safefly New grid friendly functionality for voltage control and event ridethrough

14 14 NCSU PnP Demonstration System PnP Compliant PV System PV Utility Interface (PUI) PV MPBB MPBB to PUI Wiring Meter Base Grid PV Meter Parallel Connection Option PV PV Plug Auto-Interconnect Logic Auto-Commission Logic PV Metering Permit & Interconnection Certificate (Optional) Utility AHJ PV Localized Signaling for Diagnostics Inverter Interface Communications Interface Commission/Interconnect Report

15 15 Power Conversion Options Options Currently Deployed String PV Inverter system Multi-Port Building Blocks PUI PUI Lowest cost per Watt, Simplest Wiring MPPT Issues, DC Arc Concern PV Microinverter System PUI Better cost per Watt Simple wiring No MPPT issue No DC arc concern Best flexibility, No DC arc issue, No MPPT issue Cost concern

16 16 Photovoltaic Utility Interface Inserted between Meter Socket and Meter. Special Connector with Mechanical Interlock. Electronic Disconnect. Processor for Hosting Logic. Ground Fault Protection. Power Line Carrier interface to MPBBs.

17 17 Residential Home Installation Utility or Contractor installed PUI. MPBB mounted in power strip connects 4 8 PV Panels. Standardized Module to Plug Cabling. Plug Interlocking with PUI.

18 18 Next Steps Solicit Feedback from Utilities and AHJs regarding PnP Requirements and Features. Multi-Port Building Block Prototyping. Commissioning and Interconnection Hardware and Software for PUI. Working Demonstration System.