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

Current

0 50 100 150

0

500

1000 Power 

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

PRODUCTION (KWH/KWP) 

GROUND COVERAGE RATIO

ANNUAL ENERGY - COLORADO RTC SITE

Conventional

VT8012

• 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
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Predicted annual performance

0%

10%

20%

30%

40%

0

20

40

60

80

100

120

140

160

MONTHLY GAIN

MONTHLY PRODUCTION (KWH/KWP)

MODELED ENERGY PRODUCTION

COLORADO RTC SITE WITH GCR = 0.54

VT8012

Conventional

Gain

• 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%

HEIGHT ALONG MODULE 

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 − cos2 ψ

2 Diffuse loss = 

ψ z = arctan

L − z sin β

R − L cos β + z cos β

Diffuse “screening angle” ψ

 
18

View factor loss of diffuse irradiance

0

0.25

0.5

0.75

1

-10% -5% 0%

HEIGHT ALONG MODULE 

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 − cos2 ψ

2 Diffuse loss = 

ψ z = arctan

L − z sin β

R − L cos β + z cos β

Diffuse “screening angle” ψ

 

What is the link to Power loss?
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Diffuse shade loss

-10%

-8%

-6%

-4%

-2%

0%

0.35 0.45 0.55 0.65

DIFFUSE LOSS RELATIVE TO ROW 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

DIFFUSE LOSS RELATIVE TO ROW 1

GROUND COVERAGE RATIO

Model - Best case

Conventional

Model - Worst case

Maxim

Maxim Maxim

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