PV Geographic Smoothing Effect

Michael McCarty, Andu Nguyen, and Sarah WalingaGrid Engineering Solutions

May 10th, 2016EPRI-Sandia PV Systems Symposium

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SolarCity’s national scope and breadth of experience can help you save on energy costs.

2,000+ Commercial projects

1,600+ MW installed400+ School installations

26 States with installations

9 Years of experience

14,000+ Employees

$9 Billion+ Of solar projects

The national leader in solar, SolarCityhas:

SolarCity has experience addressing major challenges.

We reduce your energy expenses.Our customers buy energy from us at a lower rate than they currently pay for electricity from utilities, with no up front cost.

We offer predictable energy prices.You’ll be able to accurately predict and manage your energy costs for 20 or more years.

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Source: National leader according to the Q1 2015 GTM Research U.S. PV Leaderboard. “States currently served” data as of 8/11/15; “Facilities,” “Employees” and “MW Deployed” data as of 6/30/15; “School installations” data as of 9/24/14; “Commercial projects” data as of 4/22/15;  “Funds raised to finance solar projects” data as of 5/28/15.

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SolarCity Collaboration Projects

Transient Overvoltageand Hosting Capacity

DER Aggregation for Grid Support

Smart Inverter Field Demonstration

Multi-Inverter Anti-Islanding with Grid Support Functions

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• While cloud cover impacts PV generation output, cloud movement is not instantaneous and the way in which light reflects off of clouds results in a geospatial diversity at the ground level.

• Recent high resolution inverter output data from SolarCity validates this concept of geographic smoothing as it relates to distributed PV.

• Distribution planning typically relies on a diversity of load. Now it can rely on a geospatial diversity of distributed energy resources.

Executive Summary

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Agenda

• Previous Research

• SolarCity’s Distributed PV Generation Data

• Practical Implications

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EPRI Solar Calendar

Image Source: “Is the Grid Ready: Preparing for Solar.” Tom Key. Electric Power Research Institute. (2015)

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Sandia’s Ota City Study2 MW over 0.15 mi2 and 553 Homes

Image Source: “Ota City: Characterizing Output Variability from 553 Homes with Residential PV Systems on a Distribution Feeder.” Lave et al. Sandia National Labs. (2011)

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Agenda

• Previous Research

• SolarCity’s Distributed PV Generation Data

• Practical Implications

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SolarCity’s Distributed PV Generation Data

• Data was collected in San Jose from 4/01 to 4/22 at one to five second intervals.

Representing Radius (miles) Number of Inverters

AC Nameplate (kW)

Line Regulator 1.6 100 400Load Tap Changer 4 300 1300

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SolarCity’s Distributed PV Generation Data

: ⋯

⋯

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SolarCity’s Distributed PV Generation Data

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SolarCity’s Distributed PV Generation Data

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SolarCity’s Distributed PV Generation Data

• Per unit max output swing in any one minute decreases as the area covered increases.

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SolarCity’s Distributed PV Generation Data

• For the 1.6 mile radius in any one minute interval, a max output swing greater than 5% was seen only 234 times (1.5% of time studied).

• A max output swing greater than 10% was seen only 5 times (0.03% of the time studied).

Count of One Minute Intervals with a Maximum Output Swing > X%

> 5% > 10% > 15%1.6 Mile Radius 234 5 1

4 Mile Radius 7 0 0

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Agenda

• Previous Research

• SolarCity’s Distributed PV Generation Data

• Practical Implications

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Voltage Flicker

• Flicker, fluctuation, and deviation often used interchangeably.

• GE curve has been superseded, but flicker intensity is challenging to proactively determine.

Image Source: IEEE

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• When calculating voltage deviation or flicker, use a ΔP (kW) of less than 100% of nameplate.

• This is a worst case scenario. The change in voltage in modeling software will be less.

Voltage Flicker

100% ⇒ ∆ 3400

3 ∗ 1000 ∗ 121.9%

30% ⇒ ∆ 30%

330% ∗ 4003 ∗ 1000 ∗ 12

0.6%

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• Tap operations can be similarly smoothed.

• Due to the smoothing effect, regulator is more likely to remain at new tap position or reset.

Tap Operations

; 6

10%∆ ⇒ 10% ∗ 0.5 ∗ 6 0.3 0.75

50% ⇒ 0.5

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Michael McCarty, PEPrincipal Engineer, Grid Engineering SolutionsSolarCity

mmccarty@solarcity.comsolarcity.com/gridx

Questions?