Modelling of the Expected

Yearly Power Yield on Building

Facades in Urban Regions by

Means of Ray Tracing

Hendrik Holst1

Matthias Winter2, Malte R. Vogt1,

Monika Sester3, Hai Huang3, Pietro P.Altermatt2

4th PV Performance Modelling and Monitoring Workshop

Cologne , 22.10 – 23.10.2015

1 Institute of Solar Energy Research Hamelin (ISFH) 2 Dep. Solar Energy, Inst. Solid-State Physics, Leibniz University of Hannover 3 Institute of Cartography and Geoinformatics, Leibniz University of Hannover

Overview

• Advantages of facades

• The ray tracing framework DAIDALOS

• Modelling daylight, including its spectral

and angular distribution

• Simulation of buildings in the urban hinterland

and in the city

[1] P. Redweik, C. Catita, M. Brito, Solar energy potential on roofs and facades in an urban landscape,

Solar Energy, Volume 97, November 2013, Pages 332-341

Advantages of facades ?

• City buildings provide large areas of facade space

(outnumbering the available roof area)

• Less prone to soiling by snow or dust

• Widening of the peak power interval by using east-

or west-oriented installations

• In winter, the best oriented facades provide a higher

power yield than the roof [1]

Daidalos

–

A modular ray tracer

Daidalos – A modular ray tracer

[1] Brendel, R., Sunrays: a versatile ray tracing program for the photovoltaic community, EUPVSEC 1994

[2] Cotter, J.E., RaySim 6.0: a free geometrical ray tracing program for silicon solar cells, PVSC 2005

[3] Holst, H et al., Application of a New Ray Tracing Framework to the Analysis of Extended Regions in Si Solar

Cell Modules, Energy Procedia, 2013

• Ray tracing is a well known approach for simulating solar cells

(e.g. SUNRAYS [1] , RAYSIM [2])

• DAIDALOS [3] provides a modular approach

[1] Brendel, R., Sunrays: a versatile ray tracing program for the photovoltaic community, EUPVSEC 1994

[2] Cotter, J.E., RaySim 6.0: a free geometrical ray tracing program for silicon solar cells, PVSC 2005

[3] Holst, H et al., Application of a New Ray Tracing Framework to the Analysis of Extended Regions in Si Solar

Cell Modules, Energy Procedia, 2013

Monolithic ray tracer

- Height of wafer

- Number of photons

- Geometry

- Hit search

• Ray tracing is a well known approach for simulating solar cells

(e.g. SUNRAYS [1] , RAYSIM [2])

• DAIDALOS [3] provides a modular approach

Daidalos – A modular ray tracer

• Ray tracing is a well known approach for simulating solar cells

(e.g. SUNRAYS [1] , RAYSIM [2])

• DAIDALOS [3] provides a modular approach

[1] Brendel, R., Sunrays: a versatile ray tracing program for the photovoltaic community, EUPVSEC 1994

[2] Cotter, J.E., RaySim 6.0: a free geometrical ray tracing program for silicon solar cells, PVSC 2005

[3] Holst, H et al., Application of a New Ray Tracing Framework to the Analysis of Extended Regions in Si Solar

Cell Modules, Energy Procedia, 2013

Monolithic ray tracer

- Height of wafer

- Number of photons

- Geometry

- Hit search

Daidalos

Lightsource Coating Geometry

Plugin management

Daidalos – A modular ray tracer

• Evaluation of the impact of the inter-cell gap [1]

• Ray tracing of modules under realistic day light conditions [2]

• Evaluation of heat sources in solar cell modules [3]

o See also the poster P4 of Malte Vogt

„ Modeling of c-Si PV modules by coupling

semiconductor and thermal equations”

[1] Holst, H et al., Application of a New Ray Tracing Framework to the Analysis of Extended Regions in Si Solar

Cell Modules, Energy Procedia, 2013

[2] Winter, M. et al.,Impact of Realistic Illumination on Optical Losses in Si Solar Cell Modules Compared to

Standard Testing Conditions, EUPVSEC, 2015

[3] Malte R. Vogt, Hendrik Holst, Matthias Winter, Rolf Brendel, Pietro P. Altermatt, Numerical Modeling of c-Si PV

Modules by Coupling the Semiconductor with the Thermal Conduction, Convection and Radiation Equations,

Energy Procedia, Volume 77, August 2015, Pages 215-224

Applications of DAIDALOS

Modelling of

daylight

Daylight

• Sun’s position (α,φ) changes during a

day and over the year

• Therefore, angular and specular

distribution is changing

• Clouds influence both distributions

by

o Shading the diffuse blue sky

o Reflecting direct light from the sun

in a diffuse manner

Irradiance measurements

• Global and diffuse irradiance are

measured at many locations

(e.g. see the National Solar Radiation

Database [1])

[1] http://rredc.nrel.gov/solar/old_data/nsrdb/

Irradiance measurements

Movable shade

Thermopile

sensor Glas bulb

• Global and diffuse irradiance are

measured at many locations

(e.g. see the National Solar Radiation

Database [1])

• Measured at ISFH during 14 years

(1992 – 2006) using a pyranometer

[1] http://rredc.nrel.gov/solar/old_data/nsrdb/

Irradiance measurements

• Global and diffuse irradiance are

measured at many locations

(e.g. see the National Solar Radiation

Database [1])

• Measured at ISFH during 14 years

(1992 – 2006) using a pyranometer

Movable shade

Thermopile

sensor Glas bulb

Problem

• No information about spectral

distribution

• No information about angular

distribution

[1] http://rredc.nrel.gov/solar/old_data/nsrdb/

Calculating spectral distribution

[1] Gueymard,C., SMARTS2, A Simple Model of the Atmospheric Radiative Transfer of Sunshine: Algorithms and

performance assessment, Techreport, Florida Solar Energy Center 1995

• SMARTS software [1] allows for calculation of

spectra for diffuse and direct light

Fdiff.(λ,α) and Fdir.(λ,α)

Altitude dependent photonfluxes

Calculating angular distribution

• SMARTS software [1] allows for calculation of

spectra for diffuse and direct light

[1] Gueymard,C., SMARTS2, A Simple Model of the Atmospheric Radiative Transfer of Sunshine: Algorithms and

performance assessment, Techreport, Florida Solar Energy Center 1995

[2] Gueymard, C., An anisotropic solar irradiance model for tilted surfaces and its comparison with selected

engineering algorithms, Solar Energy, 1987

Fdiff.(λ,α) and Fdir.(λ,α)

Altitude dependent photonfluxes

• Distribution on different solid angles by Gueymard [2]

o Direct light: Associated with the position of the sun

o Diffuse light: Distributed over the sky by a

distribution factor R(α,φ)

Calculating angular distribution

• SMARTS software [1] allows for calculation of

spectra for diffuse and direct light

[1] Gueymard,C., SMARTS2, A Simple Model of the Atmospheric Radiative Transfer of Sunshine: Algorithms and

performance assessment, Techreport, Florida Solar Energy Center 1995

[2] Gueymard, C., An anisotropic solar irradiance model for tilted surfaces and its comparison with selected

engineering algorithms, Solar Energy, 1987

[3] Winter, M. et al.,Impact of Realistic Illumination on Optical Losses in Si Solar Cell Modules Compared to

Standard Testing Conditions, EUPVSEC, 2015

Fdiff.(λ,α) and Fdir.(λ,α)

Altitude dependent photonfluxes

• Distribution on different solid angles by Gueymard [2]

o Direct light: Associated with the position of the sun

o Diffuse light: Distributed over the sky by a

distribution factor R(α,φ)

• For more details, see [3]

Angular distribution

Hamelin, Germany

52.07°N

9.35°E

Quelle: Google Maps

[1] Winter, M. et al.,Impact of Realistic Illumination on Optical Losses in Si Solar Cell Modules Compared to

Standard Testing Conditions, EUPVSEC, 2015

Extracted from [1]

altitude 57.5°

azimuth 177.5°

altitude 7.5°

azimuth 157.5°

altitude 57.5°

azimuth 2.5°

One spectrum per bin

Extracted from [1]

[1] Winter, M. et al.,Impact of Realistic Illumination on Optical Losses in Si Solar Cell Modules Compared to

Standard Testing Conditions, EUPVSEC, 2015

Daylight vs. AM1.5G

• Daylight scaled to 1000 W/m2 to match AM1.5G

[1] Winter, M. et al.,Impact of Realistic Illumination on Optical Losses in Si Solar Cell Modules Compared to

Standard Testing Conditions, EUPVSEC, 2015

Extracted from [1]

Artificial daylight sources

Quelle: Google Maps

Makoua, Africa

0.0°N

15.6°E

Artificial daylight sources

Quelle: Google Maps

JokkMokk, Sweden

66.58°N

19.82°E

Simulation of buildings

Collecting building geometry

Source: http://www.openclipart.org

Source: Manufacturer-Website

https://rieglusa.wordpress.com/tag/riegl-vmx-250/

Study „Vertikale Solarfassaden in Hannover“ on behalf of the region of Hannover for LiFE 2050.

The facade geometry of real buildings was collected by the

Institute of Carthography and Geoinformatics (IKG) of the

Leibniz University Hannover using laser scanning.

Assumptions

Module efficiency: 0.16

System efficiency: 0.85

Simulation process

Study „Vertikale Solarfassaden in Hannover“ on behalf of the region of Hannover for LiFE 2050.

Buildings in the urban hinterland

Study „Vertikale Solarfassaden in Hannover“ on behalf of the region of Hannover for LiFE 2050.

Buildings in the urban hinterland

Study „Vertikale Solarfassaden in Hannover“ on behalf of the region of Hannover for LiFE 2050.

Buildings in the urban hinterland

Study „Vertikale Solarfassaden in Hannover“ on behalf of the region of Hannover for LiFE 2050.

An urban building

Study „Vertikale Solarfassaden in Hannover“ on behalf of the region of Hannover for LiFE 2050.

An urban building and its neighbors

Study „Vertikale Solarfassaden in Hannover“ on behalf of the region of Hannover for LiFE 2050.

Conclusion

• Daylight light source + ray tracing allows

for realistic simulation of the expected

power yield

• Impact of shadowing obstacles are included

in a natural way

• Presented approach allows calculation

of angular and spectral distribution from

measured irradiances

• Using a ray tracing approach, our simulations

require about 5 to 15 minutes

Thank you for

your attention !

Hendrik Holst

Institute of Solar Energy Research Hamelin (ISFH)

E-Mail: holst@isfh.de

Tel.: +49-5151-999644