5 hartmut nussbaumer, bifi psda, antofagasta (chile) 2015

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


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





• Focus

Silicon Wafer Solar cell Module System Integration, Batteries


Increasing share of PV

Lost energy or energy storage


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


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?”


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


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


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?


Solution 2 ?: East/west orientation ofbifacial modules

N

W


Bifacial ModuleMeasurement - Setup

• Bifacial: vertical - azimuth 90° Pn1=255.6 / 232.6 WSTC

• Bifacial: 30° inclination / azimuth 0° Pn2=255.3 / 231.7 WSTC


Bifacial module east/westMeasurement results: +8.4% Power @ 2014-05-18

5 8 11 14 817 20

IrradiancePower East/WestPower South


=> 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?


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


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


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


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


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%


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!


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


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


Acknowledgement

Many thanks to our friends at the ISC for the good cooperation

and for your attention!

Presentations & Public Speaking

5 hartmut nussbaumer, bifi psda, antofagasta (chile) 2015