5 hartmut nussbaumer, bifi psda, antofagasta (chile) 2015
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Zürcher Fachhochschule
New opportunities of grid integration by the use of bifacial modules
H. Nussbaumer, T. Baumann, F. Carigiet, N. Keller, D. Schär, F. Baumgartner
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ZHAW –SoE - IEFE PV
• ZHAW = Zurich University of Applied Sciences• Close to 11.000 students• School of Engineering located in Winterthur (~15km
away from Zurich)• IEFE = Institute of Energy Systems and Fluid
Engineering
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ZHAW –SoE - IEFE PV
• Focus
Silicon Wafer Solar cell Module System Integration, Batteries
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Power distribution / storage
In the near future many regions will face the problem of an over PV capacity during midday and too low capacity in the evening
We do not only have to think about the maximum energy harvest but also about the load profile!
We need energy storage or have to adapt the energy production profile on the load profile
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Load distribution, example Chile
• If we want to supply energy to a copper mine we have to ask:
• “What is the load profile of a copper mine?”
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Solution:Energy storagePeak shift - battery storage & costs
N. Kreutzer, C. Allert, J. Weide, M. Rothert, F. Thim; 4BV.1.3125th European Photovoltaic Solar Energy Conference /5th World Conference on Photovoltaic Energy Conversion, 6-10 September 2010, Valencia, Spain
produce it
0.18 USD/kWh
store it
> 0.42 USD/kWh+ =use it
> 0.60 USD/kWh
4 person household5kW PV20% to 40%PV self consumption
0.74€/kWh; F. Baumgartner et. al. EUPVSEC 2012, Plenary Talk, www.zhaw.ch/~bauf
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Solution: Energy storagePeak shift - battery storage & costsCopper mine
Power
Load profile copper mine
PV power generation profile
Transfer this energy adds significant cost
Time
store it
> 0.42 USD/kWh
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Solution: Energy storagePeak shift - battery storage & costs
Energy storage significantly increases the cost of generated PV energy
Due to large scale production of batteries cost of storage tend to go down but even, if they were cut by half, the cost of generated kWh of PV will by at least doubled-
Can we modify the PV energy generation profile?
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Bifacial ModuleMeasurement - Setup
• Bifacial: vertical - azimuth 90° Pn1=255.6 / 232.6 WSTC
• Bifacial: 30° inclination / azimuth 0° Pn2=255.3 / 231.7 WSTC
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Bifacial module east/westMeasurement results: +8.4% Power @ 2014-05-18
5 8 11 14 817 20
IrradiancePower East/WestPower South
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=> With a bifacial module in east/west orientation you would need less peak shift, if your load is in the morning and the evening!
• What happens in the PV system?
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PV System bifacialsouth orientation
d𝑓 = 𝑏/𝑑 b
Characteristics:
• Depending on mounting height and albedo higher energy harvest as compared to standard modules
• Energy peak during midday• Shading losses below 5% (Zurich) for f = 0.5
south
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PV system bifacialeast/west
Characteristics:
• Broader distribution of the daily energy production• Very low chance of soiling• Possibility of using alternative, maybe cheaper, mounting systems• Chance of further enhancing the energy harvest by use of reflective underground• Higher energy harvest as compared to south oriented module but• Enhanced shading losses based on the same degree of land utilisation as
compared to south orientation
S
E
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Simulation with PVSyst
• Simulation parameters– 2 standard modules = 1 bifi module– Variation of tilt angle and azimut– Albedo = 0.2, model Perez
• Degree of area utilization 𝑓 = 𝑏/𝑑
• Limitation: No complete row of modules as shading barrier
Bifi Module simulated
d = Distance between modules
S
b
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First Simulation results using PVSyst
Using a standard utilization factor of 0.5 a relative difference of 10% in shading is observed- but?
0%
5%
10%
15%
20%
25%
30%
35%
1,00 0,50 0,33 0,25
Lo
ss i
n P
erc
en
t
Degree of area utilization
Bifacial east/westorientation
South 37°
South 30°
Shading losses resulting from neighbored modules
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Simulation with PVSyst
A PV System consisting of east/west bifacial modules can be superior to monofacial modules with the same area utilization rate, if a reflective material is positioned in between the modules- this overcompensates the higher shading by far!
First measurements with a white foil have shown an increase of power by ~60% (no shading)
f=0.5 PR
Monofacial 30° South oriented, Albedo 0.2 100.8%
Monofacial 30° South orientated Albedo 0.85 101.2%
Bifacial East/West orientated 90° Albedo 0.2 96.4%
Bifacial East/West orientated 90° Albedo 0.85 126.8% 2
_
/1 mkW
PE
E
PRN
InputSolar
AC
-5%+25%
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Simulation with PVsyst
Albedo 0.26 8:45 16:3014
Measured data
Power
Simulated data
=>The simulation with PVsyst does not show a good fit to the measured data!
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Conclusion
• There is a need for PV power generation profiling in order to adapt to the power load
• Bifacial modules in east/west orientation are a possible solution if the highest load is in the morning and evening
• Shading has a severe impact on the energy harvest for PV systems with east/west oriented modules for high area utilization rates.
• Using a reflective ground in between the modules can have a significant impact on the energy harvest, especially for east/west oriented modules
• The most economic solution for a certain energy system using PV depends on– Energy load distribution– Cost for energy storage– Area related costs– Conditions for soiling– Wind loads– Reflectivity of the ground
Designing a PV system isgetting more complex
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Outlook
• Simulation models have to be adapted to bifacial modules in order to give better predictions
• Measurement on real bifacial PV systems with east/west orientation will be made and compared to simulated data using various reflective undergrounds, heights of the modules, area utilization ratios
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