Electrochromic Glass

Sustainable Built Environments | College of Architecture + Planning + Landscape Architecture

The University of Arizona

Armando Lagunas

Mentor: Colby Moeller AIA, LEED AP

May 4, 2017

Abstract

Electrochromic glass is a type of smart glass, a new technology that has potential to

reduce the amount of sunlight entering a building by changing its physical properties. The

purpose of this study is to understand the properties of electrochromic glass and determine if it is

a viable alternative to conventional single pane and double pane glass in the Tucson area. Using

research and statistics from smart glass production companies, a comparative analysis will be

done using the building simulation software Energy-10. It was found that when compared to

single pane glass, double pane glass had a decrease of 7.21% in energy cost and electrochromic

glass had a decrease of 9.81%. For the used building model, this meant a return investment in 30

and a half years. While electrochromic glass is a new clean method of energy usage reduction, it

currently cannot return the consumers initial investment within a desirable time span.

Table of ContentsIntroduction…………………………………………………………………………….....……4What is Smart Glass?. ……………………………………………………………….........…6- Three Types of Smart Glass…………………………………………………..…………6

o Electrochromic Glass………………………………………………….…………6o Suspended Particle Glass………………………………………………….……8o Polymer Dispersed Liquid Crystal (PDLC) Glass ………………………….…9

Methodology……………………………………………………………………………………10Literary Review…………………………………………………………………...……………11- Service Life…………………………………………………………………………………12- Maintenance……………………………………………………………………………..…12- Drawbacks…………………………………………………………………………….……13Data………………………………………………………………………………………..…….14- Building Model………………………………………………………………………..….…16- Comparison………………………………………………………………………...…....…15Discussion………………………………………………………………………………...….…18Conclusion………………………………………………………………………………………19Limitations……………………………………………………………………….………………19Recommendations for Future Study…………………………………………………….……20References………………………………………………………………………………………22- Additional Resources………………………………………………………………………22

Introduction

One of the biggest issues the city of Tucson, Arizona faces in becoming a more

sustainable city is the sun. With temperatures reaching over 100 degrees Fahrenheit and limited

cloud cover, the sun impacts all aspects of life from the roads needing constant repair, to the

city’s water supply becoming even more hampered, and more energy has to be used in order to

keep people in an appropriate thermal comfort zone. The Intergovernmental Panel on Climate

Change (IPCC) forecasts the temperature rise from 2.5 to 10 degrees Fahrenheit over the next

century (Climate, 2017). For buildings, two of the biggest issues are regulating the amount of

sunlight and daylight that enters from windows. In order to address this issue, many homeowners

will install windows with multiple panes or tint that may be highly reflective. While a reasonable

thought, such actions may cost them more in the long run than the amount they save from the

reduced energy usage.

Windows are great in the way they allow light and heat to enter buildings when we need

it, yet they are also bad because they allow light and heat in when it should not be. This means

we must provide shading in order to reduce the amount of light entering and use more energy for

air-conditioning. However, smart glass may provide a solution. What makes smart glass special

is electrochromism, which changes the color of the coated thin layer of metal-oxide material

from transparent to opaque when an electrical voltage is applied across the pane.

In the darkened state, smart glass can reflect up to about 98% of all light falling on it,

which drastically reduces the amount of energy used for air-conditioning (Clayton, 2011). Since

they are electrically operated, they can be controlled by a switch, a smart-home system, or a

sunlight sensor, which does not require people to be inside the building. The amount of

electricity required to switch 100 windows from light to dark equates to the same amount of

energy needed for a single incandescent lamp (Woodford, 2017). According to scientists at the

US Department of Energy’s National Renewable Energy Laboratory (NREL), these windows can

save up to 8% of the building’s total energy consumption. Aside from this, smart glass also

provides privacy almost instantly compared to using curtains or blinds. This privacy is a

convenience not available with standard glass. Additionally, smart glass is highly reliable due to

their simplistic design. This capstone, will be proposing the use of electrochromic glass or “smart

glass” as a more practical and efficient substitute to traditional windows. To do so this study will

analyze the overall cost of electrochromic glass to determine how much energy and money can

be saved through their installation in the Tucson area. Then, it will compare the results to other

types of glass to determine how it ranks in comparison.

What is Smart Glass?

Smart glass, or switchable glass, is glass whose transparent properties can be altered with

the introduction of a voltage charge (Wong and Chan, 2014). By being able to change from being

transparent to opaque, this means that the windows themselves can reduce the amount of light

and heat entering a building without the need for curtains or blinds. The reason this is significant

is that this reduces the cost in heating, air-conditioning, and lighting while maintaining an

optimal human thermal comfort zone. By introducing smart glass, a building can minimize glare,

maximize daylighting, and protect interior furnishings and artwork. Smart glass comes in

different forms which are electrochromic glass, suspended particle glass, and polymer dispersed

liquid crystal (PDLC) glass.

Three Types of Smart Glass

Electrochromic Glass

Electrochromic glass is the most common type of smart glass seen on the market. Its

manufacturing process is relatively simple due to its layered structure and the materials

necessary are not too expensive. While producing high performance electrochromic glass can

have a higher cost due to its high-performance materials such as In2O3 (ITO). Electrochromic

glass is a glass pane with electrochromic materials within it. These materials are able to change

optical properties due to electrochemical redox reactions with the introduction of electric current

across it (Wong and Chan, 2014). By being introduced to glass, the reflectivity, emissivity,

transmissivity, and absorptivity of light that passes through the glass can now be controlled with

a voltaic charge. Due to these properties, electrochromic glass is the more prominent form of

smart glass seen on the market (Wong and Chan, 2014).

Electrochromic glass consists of five layers which are placed on glass substrate or within

two glass substrates as seen in Fig. 1. The center layer is composed of an ion conductor that

allows the flow of small mobile ions such as H+ and Li+ ions. This center layer is placed

between an electrochromic film and an ion storage film. Tungsten oxide is typically used for the

electrochromic film layer. The reasoning behind this is tungsten oxide is a transition metal,

meaning that it has electrochromic properties which allows it to easily undergo redox reactions

(Wong and Chan, 2014). When voltage is applied, ions are introduced and expand the

geometrical arrangement of the tungsten oxide while electrons modify the electronic structure,

overall changing the optical properties. On both sides of these three layers are transparent

conductors. In today’s industry, tungsten oxide film is being used as a standard for

electrochromic film while In2O3 (ITO) is used for the transparent conducting film for high-end

purposes. For more general purposes such as window glass, tin oxide is used due to its lower cost

(Wong and Chan, 2014).

To alter the optical properties

of the glass, a voltage is applied

across the transparent conductors. In

this process ions are transferred

between the ion storage and the

electrochromic film. By controlling

the amount of voltage applied to the

transparent conductors, the degree to

which the properties are altered is

also controlled. In simply removing Figure 1 Electrochromic Glass Source: Emaze

any voltage to the glass, it will return to its original transparent state. The applied voltage also

allows for the oxidation reduction of the metal oxide electrochromic film. The voltage changes

the redox state of the glass by introducing the energy needed for the change to occur. Each redox

state having its own electronic absorption spectra. This change in spectra then changes the

optical properties of the entire electrochromic glass.

Suspended Particle Glass

Suspended particle glass, or electrophoretic glass, uses a device that also changes its

optical properties similarly to electrochromic glass. Much like electrochromic glass, suspended

particle glass requires voltage to alter its optical properties (Wong and Chan, 2014). Yet the

reason why it is not as popular as electrochromic glass is that it requires a voltage source to

maintain transparent and is opaque without.

Suspended particle glass consists of three layers, although ones with five layers have also

been made. As seen in Fig. 2 the center layer of this glass is an organic fluid or gel that suspends

needle shaped particles. These needle shaped

particles are usually made of polyiodides

(dihyrocinchonidine bisulfite polyiodide) or

paraphathite (Wong and Chan, 2014). Holding

the central layer together is two transparent

conductors which act as electrodes. Two glass

substrates are then placed on both sides of these

three layers, forming the suspended particle

glass. Figure 2 Suspended Particle Glass Source: VisualMechanical

When voltage is applied to this glass, the needle shaped particles rotate and align to form

a minimum energy state which allows light to pass through the layers and glass. Once this

voltage is removed the particles will then randomly relocate and absorb the light instead. With

applied voltage, the allowed transmission may range from about 20-60%. While the amount

voltage required varies depending on the thickness of the glass but will generally be around 20-

150 V (Wong and Chan, 2014).

Polymer Dispersed Liquid Crystal (PDLC) Glass

Similar to electrochromic and suspended particle glass, PDLC glass is designed to change

its transparency when voltage is applied. As seen in suspended particle glass, PDLC glass uses

suspended particles which rotate when voltage is applied, changing the optical properties of the

PDLC glass. Another similarity to suspended particle glass is that it requires voltage in order to

remain in its transparent state. Thus, the reasoning why it is not as commonly used as

electrochromic glass. PDLC glass also has a long transition period from either the opaque or

transparent state, which may have a duration of up to 15 min (Wong and Chan, 2014). Putting it

behind even suspended particle glass on the market.

PDLC glass consists of three layers. The center layer of which being composed of liquid

crystal droplets that are applied to a polymer matrix which is then cured. A transparent electrical

conductor film is placed on both sides of this layer, acting as electrodes. Glass substrates are then

placed on both sides of these three layers, forming the PDLC glass. An illustration of PDLC

glass can be seen in Fig. 3.

Much like suspended particle glass, when voltage is applied to PDLC glass the liquid

crystal molecules become aligned to allow light to pass through the glass. Then when the voltage

is gone, they will randomly relocate

themselves making the glass opaque.

The amount of voltage required is

dependent on the thickness of glass

and type of crystal polymer used.

When using a film with around 50%

liquid crystal droplets, the PDLC glass

will appear to be a milky white (Wong

and Chan, 2014).

Methodology

This paper, proposes the use of electrochromic glass as a more practical and efficient

substitute to traditional glass. Traditional glass being single pane and double pane glass

windows. To do so this study will be analyzing the overall cost of electrochromic glass,

including cost of purchasing, installation, maintenance, and money saved. Using data on smart

glass production company SAGE. Then comparing that cost to traditional glass cost to determine

if electrochromic glass is viable in the Tucson area. There are various ways to produce smart

glass, so each method will be analyzed in order to determine the most effective glass. Once these

values are determined Energy-10, a powerful energy simulation tool for buildings and homes,

will be used to determine if electrochromic glass is more efficient than single or double pane

glass.

Figure 3 Polymer Dispersed Liquid Crystal (PDLC) Glass Source: Glazette

Literary Review

Smart Glass and Its Potential Energy Savings by Wong and Chan was published in 2014

and is a comprehensive analysis of the various forms of smart glass and their real-world

application. In this paper, Wong and Chan discuss how smart glass differentiates itself from

other glass alternatives in the way that they can alter their physical properties to become more

efficient where they are utilized. This change is properties is engineered to alter the amount of

heat energy that can penetrate the glass, providing heating, cooling, and lighting cost savings as

only a desired amount of sunlight enters the building (Wong and Chan, 2014). Smart glass can be

classified under 3 types; electrochromic, suspended particle, and polymer dispersed liquid crystal

(PDLC). Each have their own mechanisms, advantages, and disadvantages.

Control criteria of electrochromic glasses for energy savings in Mediterranean buildings

refurbishment was written by authors Tavares, Bernardo, Gaspar, and Martins (2016). Revised

and accepted in 2016, the main focus of this publication is to determine the most suited control

strategy for electrochromic glass and their influence on internal loads in the Mediterranean

climate, while also taking into account influences on facade orientation (Tavares et al., 2016). To

do so they compare electrochromic glass to other glass alternatives using the ESP-r building

energy simulation software. This differentiates this study from others, as the goal of some

publications is to maximize the thermal comfort and the use of daylighting without regard to

reducing the energy consumption. While others are to maximize daylighting, and minimize the

electrical energy consumption for lighting.

Room temperature processing for solid-state electrochromic devices on single substrate:

From glass to flexible plastic is an article written by authors Cossari, Cannavale, Gambino, and

Gigli in 2016. These authors propose an alternative method of creating electrochromic glass that

is adopting a low-cost, eco-friendly, and has an effortless fabrication process. This new

electrochromic glass is fabricated on a single substrate and is composed of glass along with

flexible plastic (Cossari et al., 2016). That is how this article differentiates itself from others,

where instead of discussing existing types of smart glass, it proposes a new means of production.

While this article states how more efficient this new single substrate electrochromic glass is, it

does not state the actual difference in cost in fabrication or utilization compared to standard

electrochromic glass.

Service Life

Currently it is unknown what the estimated service life of smart glass is. According to the

smart glass manufacturer, The LTI Group, they have been testing the glass by turning it on and

off over 7 million times in the time span of ten years and still counting (LTI, 2017). Generally,

the life span depends on the amount of cycles, on and off, that the glass will go through, although

recent advances in productions technology have increased this shelf life to almost infinite (Wong

and Chan, 2014).

Maintenance

Maintaining smart glass is very similar to maintaining conventional glass except it

requires more care. It has a transparent coating on the external surface that keeps it cleaner for a

longer duration of time (Clayton Glass). It is crucial when cleaning this glass to use a non-

abrasive sponge, non-metal window squeegee, a clean lint-free cloth, or chamois leather. If there

is any dirt or abrasive particles used when cleaning, the glass may scratch or there may be

damage on the coating. For cleaning products, soft water or mild glass-cleaning products should

be used. In cases where there are tough marks on the glass, vinegar is recommended, although

vinegar should not be used as a regular cleaning method (Clayton Glass). It is important to not

use chemical products, products with silicones or abrasive particles, and to always apply water

first before cleaning.

Drawbacks

As good as smart glass seems, it also comes with its drawbacks. Its main handicap being

its need for a power or voltage source. This alone has prevented the large-scale integration of

smart glass as a replacement to traditional glasses. What makes the replacement process difficult

is the need for additional wiring and circuitry to be added. Where without an energy source, the

overall effectiveness of smart glass is reduced significantly.

Smart glass is designed to reduce the transmittance of light in a designated area. When

used on a building, the cost of heating and air conditioning can be reduced based on the

utilization which is largest motive of its implementation (Wong and Chan, 2014). The amount of

voltage required to power smart glass is relatively low, although can be ‘on’ for long durations of

time depending on the location. Smart glass also has a shelf life, where it will fade over time.

This shelf life is dependent on how frequent it is used, although in recent years, new technology

has increased the shelf life to be almost infinite (Wong and Chan, 2014).

Being a new product, manufacturing and installation of smart glass is still picking up.

With only a few companies that specialize in smart glass, more companies in this technology

need to be developed in order to create a large-scale market possible. With more companies

producing smart glass, the overall cost of manufacturing and implementation will decrease.

Data

Building Model

To compare the different type of glass to determine which one is the most efficient, this

study will be using a residential house as the building model. The information gathered on this

house is from an energy audit report (Levya, 2016). This house is in Organ Pipe Cactus National

Monument and is a single-family home. This house lies in the same 2009 IECC Climate Zone as

Tucson which is 2B. The front faces north-east with a grass lawn and mesquite and palo verde

trees covering a patio. While the back has an attached patio, covered by a wooden awning,

protecting the house from direct sunlight. On the north side of this house there is an attached

garage which provides shade to the driveway.

Below in Fig. 4, the location and surrounding area is showed. This is crucial in

understanding what the surrounding area of the house looks like and any objects that may

obstruct direct sunlight from entering. Fig. 5 and Fig. 6 show a 3D model representation of the

house at different corners of the house. This is simply to help visually illustrate what the house

looks like and where the windows are located. Fig. 7 is the building schedule of the house. The

key elements to take away from this in terms using this house as a standard to residential houses

in Tucson is the house orientation, volume of conditioned space, area of walls and windows on

each side, composition of walls, floor, and roof, and its mechanical components.

Figure 4 House Location Source: (Levya, 2016)

Figure 5 3D Model of House, North-East corner Source: (Levya, 2016)

Figure 6 3D Model of House, South-West corner Source: (Levya, 2016)

House Building Schedule1 Building: Name: House 39 Address: 39 Organ Pipe Dr, Ajo, AZ 853212 City: Location: Organ Pipe Cactus National Monument

Degree Days: HDD65=1,678 & CDD50=6,921 Utility Rates: Electric=0.06$/KWh

3 Climate Zone: 2009 IECC Climate Zone 2B4 Orientation 45°East of South5 Volume

Conditioned Space 17062.5ft^36 Areas

Roof NorthRoof SouthConditioned Floor AreaExposed Concrete AreaCarpeted AreaTiled AreaWalls South West North East Total WallsWindows South West North East Total WindowsDoorsPerimeter

812.5ft^2812.5ft^21625ft^2379ft^2520ft^2733ft^2

526ft^2215ft^2526ft^2215ft^21482ft^2

87ft^211ft^2105ft^230ft^2233ft^2146ft^2186ft 4in

7 RatiosTotal Glass to Floor AreaSouth Glass to Floor AreaSurface to Volume Area

0.140.050.18

8 Insulation Roof: tin sheet, 2x4 wood frame, 16” o.c., built up, R-11 continuous insulation, no rad. barrierWalls (Exterior): 1: 2x4, 16” o.c., 2: red brick, 3: slump block, insulatedWalls (Interior): 8in brick, dry wallSlab: 6” earth contact slab on grade, no perimeter insulation (carpeted and no carpet)Doors: R-1.69 (U-value=0.59)Windows: dbl clear, fiberglass w/o brk, U-value=0.55 all, S.C.=0.68, VT=0.61, frame width=1.3”, SHGC=0.6 (all)

9 ShortwaveReflectance

Roof: medium abs=0.56, Walls: medium abs=0.5

10 Infiltration 1 Air Change per Hour11 Mechanical Air conditioner + Gas Furnace + Evaporative Cooler

Efficiency: Cooling: SEER=14.0, Heating: AFUE=80%Evaporative Cooler: CFM=7000Thermostat: Occupied: Cool=77F, Heat=70F Setback: Cool=80F, Heat=68FOccupancy: 3 Residents

Figure 7 House Building Schedule Source: (Levya, 2016)

Comparison

Using the physical properties of the different types of glasses in Fig. 8, a simulation was

run using Energy-10, a powerful energy simulation tool for buildings and homes. The goal is to

determine how efficient electrochromic glass is compared to single and double pane glass. This

can be done by knowing the U-factor, solar heat gain coefficient (SHGC), and the visual

transmittance of the different glasses.

Properties SingleClear

DoubleClear

Double EC SAGE (Smart Glass)Clear Coloured

U(Btu/hr-ft^2-F) 1.03 0.48 0.29 0.29

SHGC 0.82 0.76 0.48 0.09

T-vis 0.89 0.81 0.62 0.035

Figure 8 Glass Physical Properties Source: (Levya, 2016)

After running the simulation over a timespan of a year, there is a clear deviation in

energy use (kBtu) and energy cost ($) for the different types of glass. Compared to using single

pane clear glass, there is a 5.52% percent decrease in energy use (kBtu) if double pane clear

glass is used. While there is an 8.78% decrease if Double EC SAGE glass is used. For energy

cost ($) there is a 7.21% decrease in using double pane clear glass instead of single pane clear

glass. While there is a 9.81% decrease if Double EC SAGE glass is used. The total savings in

using double pane clear glass is $93 annually and the total savings in using Double EC SAGE

glass is $126 annually.

Figure 9 Energy Use (kBtu)

Single Clear Double Clear Double EC SAGE1050

1100

1150

1200

1250

1300

Energy Cost ($)

Single Clear Double Clear Double EC SAGE72000

74000

76000

78000

80000

82000

84000

86000

Energy Use (kBtu)

Single Clear Double Clear Double EC SAGE1050

1100

1150

1200

1250

1300

Energy Cost ($)

Figure 100 Energy Cost ($)

Discussion

The goal of this paper was to determine if using electrochromic glass was more efficient

than conventional single and double pane glass in the Tucson area. In order to do so, this study

first identified what smart glass was and the various forms it comes in. Once obtaining the

physical properties of electrochromic glass, single pane, and double pane glass, the building

simulation software Energy-10 was used to obtain the efficiency of each glass. Using a building

model from Organ Pipe National Monument as my residential house model since it lies in the

same 2009 IECC Climate Zone as Tucson, which is 2B.

As shown in Fig. 9 and Fig. 10, upon running the simulation, it was found that Double

EC SAGE glass was the most efficient out of the three with an 8.78% decrease in energy use

(kBtu) and a 9.81% decrease in energy cost ($) compared to single pane clear glass. This comes

out to an annual savings of $126 if electrochromic glass is used in place of single pane glass. The

general cost of electrochromic glass is $100 for an 1x1 sq. ft^2 area. For the model used, this

comes out to a total of $3,849. Which for the model used, this would mean a return investment in

roughly 30 and a half years, excluding installation cost. The general rule of thumb when for

green building retrofit projects to save on energy is that they must have a return investment

within 7 years (USGBC). The current lifespan of electrochromic glass is unknown considering it

is a new technology but the smart glass manufacturer, The LTI Group, has stated that they have

been testing the glass by turning it on and off over 7 million times in the time span of ten years

and still counting (LTI, 2017).

Conclusion

Electrochromic glass, a type of smart glass, is a new technology that can be used in place

of conventional glass in order to save on energy usage and overall cost in electricity. This is

significant to the Tucson area as it has limited cloud coverage and long summer months. After

running the building simulation software Energy-10, it was found that electrochromic glass had a

9.81% decrease in energy cost compared to single pane glass. Resulting in a savings of $126

annually. While this seems good, the return investment is roughly 30 and a half years. With the

general rule of thumb for return investment being within 7 years, it is not recommended to

implement electrochromic glass in the Tucson area. Being a new technology, there is still more

room for improvement as more companies enter this field and new discoveries are being made.

With that bringing the cost of production to decline and its efficiency to increase. Meaning that

with time this new technology may become the new standard for conventional glass.

Limitations

The purpose of this study was to compile information on electrochromic glass and

determine if it is a viable alternative to current traditional windows. There is currently few

companies which produce smart glass such as SAGE Glass, meaning there is limited amount of

data available on electrochromic glass efficiency. In order to obtain the cost of installation a

quote from a smart glass company is needed, upon contacting various companies to obtain a

quote for this paper I was denied considering I am not a home owner actually looking to install

smart glass. Being a new technology, there is no proven track record of electrochromic glass,

making it hard to prove cost benefits (Malins, 2014).

Recommendations for Future Study

1) Electrochromic Glass Installation Quote

a. What is the cost of Installation?

b. New construction vs. conventional glass replacement?

c. Residential vs. commercial building?

2) Lifespan

a. Once it is discovered, what is the estimate lifespan?

b. What is the associated cost of replacing?

c. End cost comparison to conventional glass.

d. Durability in Tucson climate compared to different climate zones.

3) Cost Reduction

a. Change in the number of electrochromic glass production companies.

b. Is there a change in cost with more competition?

c. Any new methods of producing a more efficient and cheaper smart glass?

4) Case Studies

a. Obtain change in energy usage and cost from buildings that have implemented

electrochromic glass.

b. Due a comparison from different locations to determine if some electrochromic

glass is more efficient in other climate zones.

References

Clayton Glass. (2011). Smart Glass Self-cleaning glass. Tanfield Lea Industrial Estate. Retrieved: https://claytonglass.files.wordpress.com/2011/09/sgg-smartglass-b1.pdf

Cossari, P., Cannavale, A., Gambino, S., Gigli, G. (2016) Room temperature processing for solid-state electrochromic devices on single substrate: From glass to flexible plastic. Solar Energy Materials and Solar Cells.

Levya, A., Eda, J., Lagunas, A., Wang, Y., Welch, M. (2016) Organ Pipe Cactus National Monument Energy Audit.

LTI Smart Glass, Inc. (2017) The LTI Group: World Leader in Security, Architectural and Decorative Glass.

Malins, L. (2014) Glass of the Future. Burnham-Moores Center for Real Estate. University of San Diego.

SAGE Electrochromics, Inc. (2010) Performance Assessment of Sage Glass Electrochromic Coatings and Control Scenarios. Paladino and Company.

Tavares, P., Bernardo, H., Gaspar, A., Martins, A. (2016) Control criteria of electrochromic glasses for energy savings in Mediterranean buildings refurbishment. Solar Energy.

Wong, K., Chan, R. (2014) Smart Glass and Its Potential Energy Savings. Journal of Energy Resources Technology.

Woodford, C. (2017) “Smart” windows (electrochromic glass). Retrieved from http://www.explainthatstuff.com/electrochromic-windows.html.

Additional Resources

https://climate.nasa.gov/effects/ http://www.usgbc.org/articles/green-building-facts http://www.glazette.com/ https://www.emaze.com/ http://www.visualmechanical.com/ https://modernize.com/home-ideas/32437/smart-windows-cost?v2