2014 PV Performance Modeling Workshop: PVSim Update: Mike Anderson, SunPower Corporation

PVSim Update

Mike Anderson

Presented at the 2014 Sandia PV Performance Modeling Workshop

Santa Clara, CA. May 5, 2014 Published by Sandia National Laboratories with the Permission of the Author

2 © 2013 SunPower Corporation

Recent Updates

Updated the Soiling Loss Model

Added new Snow Loss Model

• SunPower-designed simulator

• Free web-based access to:

– SunPower employees

– Partners and dealers

– External parties (upon request)

3 © 2013 SunPower Corporation

Dynamic Soiling Loss Model

Previous Model New Model

Environment User selection

(NorCal/SoCal/Central,

Urban/Suburban/Rural)

Based on Lat/Lon (Koppen-

Geiger classification)

- allows for user adjustment

System type No distinction System tilt dependence

Coverage California Global

Validation basis 46 systems, 1 year 150 systems, 6 years average

(~20x more data)

4 © 2013 SunPower Corporation

Soiling Loss Model

Central California

Hawaii

5 © 2013 SunPower Corporation

Soiling Loss Model

6 © 2013 SunPower Corporation

Snow Loss Model

Accumulation ∆𝑆𝐷𝑃𝑉𝑎𝑐𝑐𝑢𝑚= ∆𝑆𝐷𝐺 × 𝑐𝑜𝑠𝛽 (∆𝑆𝐷𝐺> 0)

Where:

∆𝑆𝐷𝐺 = change in snow depth on the ground, and

𝛽 = slope of the PV from horizontal

Melting ∆𝑆𝐷𝑃𝑉𝑚𝑒𝑙𝑡= ∆𝑆𝐷𝐺𝑚𝑒𝑙𝑡 ×𝑐𝑜𝑠𝜃

𝑐𝑜𝑠𝜃𝑧 (∆𝑆𝐷𝐺< 0)

Where:

𝜃 = incidence angle between the sun and normal to the PV (at solar noon)

𝜃𝑧 = incidence angle between the sun and normal to the ground (zenith angle) (at solar noon)

Combined 𝑆𝐷𝑃𝑉 = 𝑆𝐷𝑃𝑉𝑝𝑟𝑒𝑣𝑖𝑜𝑢𝑠 +∆𝑆𝐷𝑃𝑉𝑎𝑐𝑐𝑢𝑚 + ∆𝑆𝐷𝑃𝑉𝑚𝑒𝑙𝑡

Where:

𝑆𝐷𝑃𝑉 = current snow depth on the PV

𝑆𝐷𝑃𝑉𝑝𝑟𝑒𝑣𝑖𝑜𝑢𝑠 = previous snow depth on the PV (last iteration)

7 © 2013 SunPower Corporation

Snow Loss Model

Sliding

𝛽𝑐𝑟𝑖𝑡 = 𝑡𝑎𝑛−1 𝜇𝑠 = ~8

Angle of repose for snow is approximately 38 -assumed 45 shed pile

Coefficient of

static friction

Coefficient of

dynamic friction

Waxed wood on wet snow 0.14 0.1

Waxed wood on dry snow 0.04

Non-waxed wood on snow 0.5 0.3

8 © 2013 SunPower Corporation

Snow Loss Model

• Validation based on 3 years of operation at 21 sites (60 systems)

– Tracker systems

– Fixed ground and roof systems ranging from 0 to 25 degrees

9 © 2013 SunPower Corporation

Snow Loss Model

T0 Tracker

10 © 2013 SunPower Corporation

Snow Loss Model

Fixed 0 degrees