2

The Influence Of Thermochromic Glazing Parameters On Energy Saving And Comfort

Criteria Using Moment-independent Measure

Arthur Ah-Nieme

PhD candidate, M.Sc.Eng in Building SciencePIMENT Laboratory /University of La Réunion

3 Context

Global Warming

Building sector

Building envelope

performance (Pérez-Lombard and al.,

2008)

Transparent

surfaces (Bülow-Hübe, 2001)

4 Context

Windows is important to provide:

• An exterior view

• Daylight

Windows play an essential role in Architecture (Carmody et al., 2004)

And also to:

• Thermal and phonic insulation

• Solar control

• Air quality control

• Security

5

Vanadium Dioxide: 𝑉𝑂2• Thermochromic properties

(Morin, 1959)

• Transition temperature : 68°C (Granqvist, 2016)

• Doping with other metals :➢ In Li and al., 2012 :

• Increase of the visible transmittance

• Increase of the solar modulation

➢ In Dietrich and al., 2015 : • Decrease of the transition

temperature

Thermochromic Glazing (TC)Has the capability to modulate its thermo-optical properties dynamically and

reversibly when a change in its temperature occurs

Literature review

• In Saeli and al., 2010 : (Cairo, Palermo, Roma)▪ ~30-40 % of energy savings in comparison to a

simple clear glazing

• In Liang and al., 2015 : (London, Guangzhou)▪ Diminution of the cooling need

▪ ~10-15 % of energy savings in comparison to a double glazing

▪ Decrease of glare occurrence

• In Costanzo and al., 2016 : (Catania, Milan, Paris)▪ ~10% of discomfort time (Top>26°C) in

comparison to a double glazing

▪ ~25% of energy savings (max for hottest climate)

▪ Decrease of glare occurrence and improvement of illuminance distribution

6

• TC glazing for building application:

• Has to be doped with other metals to improve its properties• Transition temperature

• Visible Transmittance

• Solar modulation

• Has a potential to (Hoffmann et al., 2014)

• Reduce energy consumption

• Improve thermal and visual comfort

• Has a real efficiency for hot climates

Thermochromic Glazing (TC)

Literature review

7 Aim of the study

Identify the influence of thermochromic glazing parameters for hot climates using dynamic building simulations and sensitivity analysis techniques

❖ Thermal and daylighting simulations with EnergyPlus (DOE, 2010)

❖ Sensitivity analysis method with a Python code with the SAlib (Usher et al., 2016)

❖ Analysis on several indexes

❖ Study on 4 locations (hot tropical climates)

Saint-Denis

Chennai

Weipa

Townsville

Tropical savanna climate (Kottek and al., 2006)

8 Methodology

Hypothesis: (office building)▪ Dimensions: 6m x 5m x 3m▪ Glazed surface exposed to solar radiation and wind▪ Other surfaces are adiabatic▪ No exterior obstructions

▪ Occupation: (Hoffmann et al., 2014)

▪ 8am to 5pm

▪ activity: 240 W (2 people)

▪ Electric equipment loads: 150 W/person

▪ Artificial lighting: 8 W/m²

▪ If 𝐸𝑟𝑒𝑓𝑠 < 300 lux (CIE, 2002)

▪ Air conditioning :▪ 𝑇𝑠𝑒𝑡 = 24°𝐶

▪ Flow rate: 20 Τ𝑚3 ℎ per person

Simulations performed over an entire year

9 MethodologyThermochromic glazing model in EnergyPlus (DOE, 2010)

𝜏

T (° C)

𝜏𝑚𝑎𝑥

𝜏𝑚𝑖𝑛

∆𝜏

Ts

Δ𝑇𝑠

Initialize 𝑇𝑇𝐶𝑡

Find 𝜏𝑡+1

Solve heat balance and photometric model

𝑇𝑇𝐶𝑡+1

Number of states = 5

10 Sensitivity analysis

INPUT VARIABLES SYMBOL RANGE UNIT PROBABILITY

Building Orientation BO 0-360 ° Continuous; Uniform

Window to Wall Ratio WWR 5-99 % Continuous; Uniform

Insulation Thickness 𝜃𝑖𝑛𝑠 0.01-0.7 m Continuous; Uniform

Weather File wea 1-4 - Discrete; Uniform

Switching Temperature 𝑇𝑠 5-70 °C Continuous; Uniform

Switching Temperature range ∆𝑇𝑠 1-50 °C Continuous; Uniform

Solar Transmittance Max 𝜏𝑠𝑜𝑙,𝑚𝑎𝑥 0.3-0.9 - Continuous; Uniform

Solar Transmittance range ∆𝜏𝑠𝑜𝑙 0.01-0.5 - Continuous; Uniform

Visible Transmittance Max 𝜏𝑣𝑖𝑠,𝑚𝑎𝑥 0.3-0.9 - Continuous; Uniform

Visible Transmittance range ∆𝜏𝑣𝑖𝑠 0.01-0.5 - Continuous; Uniform

Number of states state 2-20 - Discrete; Uniform

Moment-independent measure (Borgonovo, 2007)

𝛿𝑖 =1

2𝑬𝑋𝑖 න 𝑓𝑌 𝑦 − 𝑓𝑌|𝑋𝑖 𝑦

Distribution and sampling of the parameters

Simulation of each parameters set

𝐼

Analysis of Delta on the output

4096 simulations

11

Energy consumption index

• Sum of the final energy consumed in one year

• Cooling and artificial lighting

Normalized output indexes

Model Outputs

Thermal comfort index (Costanzo and al., 2016)

• % of time when the temperature is below 26°𝐶

Visual comfort index (David and al., 2011)

• % of time when the illuminance reference points are between 300 and 2000 lux

12 Results

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4

Insulation thickness

Switching temperature range

Visible transmittance range

Number of states

Visible transmittance max

Switching temperature

Solar transmittance range

Weather File

Solar transmittance max

Orientation

Window-to-Wall Ratio

delta

Iec

Ith

Iv

τ

T (°C)

𝜏𝑚𝑎𝑥

𝜏𝑚𝑖𝑛

∆𝜏

Δ𝑇𝑠

Ts

Energy index

Thermal index

Visual index

Delta Moment measure analysis

13

• Filtering model outputs according to a criteria

• Sorting given inputs by glazing size (small, medium, large)

Distribution of input parameters

Results

Output distribution Input distribution after filtering

14

Energy consumption: [0; 0.40]

Distribution of input parameters

Results

WWR[5% - 35%[

WWR[35% - 65%[

WWR[65% - 99%]

𝑇𝑠 [°C]𝜏𝑠𝑜𝑙,𝑚𝑎𝑥 Δ𝜏𝑠𝑜𝑙

Fre

quency

15

Visual comfort : [0.70; 1]

Distribution of input parameters

Results

WWR[5% - 35%[

WWR[35% - 65%[

WWR[65% - 99%]

𝑇𝑠 [°C]𝜏𝑣𝑖𝑠,𝑚𝑎𝑥 Δ𝜏𝑣𝑖𝑠

Fre

quency

16 Limitations and drawbacks

• The TC glazing model used in EnergyPlus

▪ Step function : not representative of the real thermal behaviour (Mlyuka and al., 2009)

• The geometry and building configuration

• The input uniform probability

17 Conclusion

• Impact of several input variables on several model outputs

• Designers should pay attention to

▪ The glazing area size

▪ Building orientation

▪ Climate conditions

• TC glazing parameters values to obtain the best suitable scenario

• New data that lead to more accurate design strategies for low-energy office building in cooling-dominated climates

• Results could also serve as guidelines for the improvement of TC thin coating materials

▪Solar transmittance

▪Visible transmittance

▪Transition temperature

18 Future works

• Study of the optimal parameters that reduce energy and improve

comfort using optimization techniques

• Study of this method using passive cooling and natural ventilation for

office buildings in hot tropical climates

• Need to add new input, such as air flow rate and new output indexes

19

Thank you for your attention

20 BibliographyBorgonovo, E., 2007. A new uncertainty importance measure. Reliab. Eng. Syst. Saf. 92, 771–784. doi:10.1016/j.ress.2006.04.015

Bülow-Hübe, H., 2001. Energy Efficient Window Systems. Effects on Energy Use and Daylight in Buildings. Lund University, Sweden.

Carmody, J., Selkowitz, S., Lee, E., Arasteh, D., Willmert, T., 2004. Window systems for high-performance buildings. Norton New York.

CIE, S., 2002. 008/E: 2001: Joint ISO/CIE Standard: Lighting of Work Places–Part 1: Indoor [incl. Technical Corrigendum ISO 8995: 2002/Cor. 1: 2005 (E)]. Vienna Austria Comm. Int. L’Eclairage.

Costanzo, V., Evola, G., Marletta, L., 2016. Thermal and visual performance of real and theoretical thermochromic glazing solutions for office buildings. Sol. Energy Mater. Sol. Cells 149, 110–120. doi:10.1016/j.solmat.2016.01.008

David, M., Donn, M., Garde, F., Lenoir, A., 2011. Assessment of the thermal and visual efficiency of solar shades. Build. Environ. 46, 1489–1496. doi:10.1016/j.buildenv.2011.01.022

Dietrich, M.K., Kramm, B.G., Becker, M., Meyer, B.K., Polity, A., Klar, P.J., 2015. Influence of doping with alkaline earth metals on the optical properties of thermochromic VO2. J. Appl. Phys. 117, 185301. doi:10.1063/1.4919433

DOE, U., 2010. Energyplus engineering reference. Ref. EnergyPlus Calc.

Granqvist, C.G., 2016. Recent progress in thermochromics and electrochromics: A brief survey. Thin Solid Films. doi:10.1016/j.tsf.2016.02.029

Hoffmann, S., Lee, E.S., Clavero, C., 2014. Examination of the technical potential of near-infrared switching thermochromic windows for commercial building applications. Sol. Energy Mater. Sol. Cells 123, 65–80. doi:10.1016/j.solmat.2013.12.017

Li, S.-Y., Niklasson, G.A., Granqvist, C.G., 2012. Thermochromic fenestration with VO2-based materials: Three challenges and how they can be met. Thin Solid Films, 7th International Symposium on Transparent Oxide Thin Films for Electronics and Optics (TOEO-7) 520, 3823–3828. doi:10.1016/j.tsf.2011.10.053

LIANG, R., WU, Y., WILSON, R., 2015. Thermal and visual comfort analysis of an office with thermochromic smart windows applied, in: Proceedings of International Conference CISBAT 2015 Future Buildings and Districts Sustainability from Nano to Urban Scale. LESO-PB, EPFL, pp. 71–76.

Mlyuka, N.R., Niklasson, G.A., Granqvist, C.G., 2009. Mg doping of thermochromic VO2 films enhances the optical transmittance and decreases the metal-insulator transition temperature. Appl. Phys. Lett. doi:10.1063/1.3229949

Morin, F.J., 1959. Oxides Which Show a Metal-to-Insulator Transition at the Neel Temperature. Phys. Rev. Lett. 3, 34–36. doi:10.1103/PhysRevLett.3.34

Pérez-Lombard, L., Ortiz, J., Pout, C., 2008. A review on buildings energy consumption information. Energy Build. 40, 394–398. doi:10.1016/j.enbuild.2007.03.007

Saeli, M., Piccirillo, C., Parkin, I.P., Binions, R., Ridley, I., 2010. Energy modelling studies of thermochromic glazing. Energy Build. 42, 1666–1673. doi:10.1016/j.enbuild.2010.04.010

Usher, W., Herman, J., Whealton, C., Hadka, D., xantares, Rios, F., bernardoct, Mutel, C., Engelen, J. van, 2016. SALib/SALib: Launch! doi:10.5281/zenodo.160164

21 Questions and discussions

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