NREL is a national laboratory of the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, operated by the Alliance for Sustainable Energy, LLC.

Evaluation of Maxim Module-Integrated Electronics at the DOE Regional Test Centers

40th IEEE PVSC, Denver, CO June 10, 2014 Chris Deline, Bill Sekulic, Stephen

Barkaszi, Jeff Yang, Seth Kahn NREL/PR-5J00-62171

2

Agenda

• DOE’s Regional Test Centers • Maxim PV power electronics • Inter-row shading experiment • Diffuse shading results

3

Agenda

• DOE’s Regional Test Centers • Maxim PV power electronics • Inter-row shading experiment • Diffuse shading results

4

• Partnering with National Labs: – Validate performance & reliability of PV components & systems

DOE’s Regional Test Centers

Photo credit: NREL, Sandia National Labs

5

• Partnering with National Labs: – Develop standards and methods to strengthen the

“bankability” of emerging PV technologies

DOE’s Regional Test Centers

6

Five RTC Sites = Climatic Diversity

7

Agenda

• DOE’s Regional Test Centers • Maxim PV power electronics • Inter-row shading experiment • Diffuse shading results

8

Recoverable vs. Non-recoverable loss in PV

0

10

20

Volts

Cur

rent

0 50 100 1500

500

1000

Pow

er

Global max [A]Local max [B]

• Partial shading leads to power loss from reduced irradiance (non-recoverable) and panel mismatch (recoverable)

•The better the peak-power tracking (MPPT) granularity, the higher the recoverable power

Mismatched panels in a series string. Either bypass diodes are turned on in the shaded panels (point [A]) or all panels operate at a low current (point [B])

C. Deline, B. Marion, J. Granata, S. Gonzalez. A Performance and Economic Analysis of Distributed Power Electronics in Photovoltaic Systems. NREL Report No. TP-5200-50003. Golden, CO: National Renewable Energy Laboratory, December 2010.

9

2.15 cm

Maxim’s approach to Smart Panels

Embedded electronics directly in the PV laminate • Replaces J-box bypass diodes • Buck DC-DC converter for every 10-20 cells

Credit: National Semiconductor, Tigo energy, Maxim Integrated

10

Inter-row shading benefit

1,200

1,300

1,400

1,500

1,600

1,700

0.00 0.20 0.40 0.60 0.80 1.00

PRO

DUCT

ION

(KW

H/KW

P)

GROUND COVERAGE RATIO

ANNUAL ENERGY - COLORADO RTC SITE

ConventionalVT8012

• Enables 10-20% tighter row pitch, -or- • 1-3% more energy / panel at the same row pitch

11

Agenda

• DOE’s Regional Test Centers • Maxim PV power electronics • Inter-row shading experiment • Diffuse shading results

12

Side-by side comparison

Photo credit: NREL

13

Side-by side comparison

Conventional strings

Maxim – equipped strings

Photo credit: NREL

One Maxim submodule

14

Side-by side comparison

3 row spacings

Photo credit: NREL

One Maxim submodule

15

Predicted annual performance

0%

10%

20%

30%

40%

0

20

40

60

80

100

120

140

160

MO

NTH

LY G

AIN

MO

NTH

LY P

RODU

CTIO

N (K

WH/

KWP)

MODELED ENERGY PRODUCTION

COLORADO RTC SITE WITH GCR = 0.54

VT8012ConventionalGain

• Shade occurs primarily in the Winter months • Maxim predicted improvement: 1%, 4%, 13% at 3 GCR values

16

Agenda

• DOE’s Regional Test Centers • Maxim PV power electronics • Inter-row shading experiment • Diffuse shading results

17

View factor loss of diffuse irradiance

0

0.25

0.5

0.75

1

-10% -5% 0%

HEIG

HT A

LON

G M

ODU

LE z/

L

DIFFUSE IRRADIANCE LOSS

GCR 0.54

GCR 0.65 GCR 0.45

D. Passias and B. Kallback, “Shading Effects in Rows of Solar Cell Panels,” Solar Cells 11 pp.281-291, 1983.

1 − cos2𝜓2 Diffuse loss =

𝜓 𝑧 = arctan𝐿 − 𝑧 sin𝛽

𝑅 − 𝐿 cos𝛽 + 𝑧 cos𝛽

Diffuse “screening angle” 𝜓

18

View factor loss of diffuse irradiance

0

0.25

0.5

0.75

1

-10% -5% 0%

HEIG

HT A

LON

G M

ODU

LE z/

L

DIFFUSE IRRADIANCE LOSS

GCR 0.54

GCR 0.65 GCR 0.45

D. Passias and B. Kallback, “Shading Effects in Rows of Solar Cell Panels,” Solar Cells 11 pp.281-291, 1983.

1 − cos2𝜓2 Diffuse loss =

𝜓 𝑧 = arctan𝐿 − 𝑧 sin𝛽

𝑅 − 𝐿 cos𝛽 + 𝑧 cos𝛽

Diffuse “screening angle” 𝜓

What is the link to Power loss?

19

Diffuse shade loss

-10%

-8%

-6%

-4%

-2%

0%

0.35 0.45 0.55 0.65

DIFF

USE

LOSS

REL

ATIV

E TO

RO

W 1

GROUND COVERAGE RATIO

Model - Best case

Model - Worst case

* in Denver, Diffuse irradiance makes up ~30% of total irradiance.

20

Diffuse shade loss

-10%

-8%

-6%

-4%

-2%

0%

0.35 0.45 0.55 0.65

DIFF

USE

LOSS

REL

ATIV

E TO

RO

W 1

GROUND COVERAGE RATIO

Model - Best case Conventional

Model - Worst case

Maxim

Maxim Maxim

* in Denver, Diffuse irradiance makes up ~30% of total irradiance.

21

Conclusion

• RTC sites provide validation and bankability o Leverage National Labs to provide climate diversity

• Maxim’s embedded DC converters predicted to improve performance at high GCR values o Validation still underway

• Diffuse irradiance losses match model o Match worst-case assumptions for diffuse loss

NATIONAL RENEWABLE ENERGY LABORATORY

Questions?

22

Acknowledgments This work was supported by the U.S. Department of Energy under Contract No. DOE-AC36-08GO28308 with the National Renewable Energy Laboratory and conducted under CRADA CRD-13-531 with Sandia National Laboratory and Volterra Semiconductor Corporation

Chris Deline chris.deline@nrel.gov Ph: (303) 384-6359