Innovative electrochromic devices: Energy savings

4 downloads 0 Views 682KB Size Report
All the analyses were carried out using the free simulation tool EnergyPlus v. .... each reference point as reported in the Engineering reference Manual of ..... 2016;155. 24. ASHRAE. Standard 189.1-2009 -- Standard for the Design of ...
Missing:
ScienceDirect ScienceDirect Energy Procedia 00 (2018) 000–000

Available online at www.sciencedirect.com

Availableonline onlineatatwww.sciencedirect.com www.sciencedirect.com Available Energy Procedia 00 (2018) 000–000

ScienceDirect ScienceDirect

www.elsevier.com/locate/procedia www.elsevier.com/locate/procedia

Energy (2018) 000–000 900–907 EnergyProcedia Procedia148 00 (2017) www.elsevier.com/locate/procedia 73rd Conference of the Italian Thermal Machines Engineering Association (ATI 2018), 12–14 September 2018, Pisa, Italy 73rd Conference of the Italian Thermal Machines Engineering Association (ATI 2018), 12–14 September 2018, Pisa, Italy

Innovative electrochromic devices: Energy savings and visual effects Innovative devices: Energy savings and visual The electrochromic 15th Internationalcomfort Symposium on District Heating and Cooling comfort effects a Alessandro *, Ubaldo Ayrathe , Francesco Martellottaa Assessing the Cannavale feasibility of using heat demand-outdoor a a Italy Department of Civil Engineering and Architecture (DICAR), Ayr Politecnico di Bari, via Orabona 4, 70125 Bari, Alessandro Cannavale Ubaldo , Francesco Martellotta temperature function for aa*,long-term district heat demand forecast a

Department of Civil Engineering and Architecture (DICAR), Politecnico di Bari, via Orabona 4, 70125 Bari, Italy

a

Abstract

I. Andrića,b,c*, A. Pinaa, P. Ferrãoa, J. Fournierb., B. Lacarrièrec, O. Le Correc

a IN+ Center for Innovation, Technology and(EC) Policysmart Research - Institutorepresent Superior Técnico, Av. Rovisco Pais 1,of1049-001 Adaptive facades, like electrochromic windows, the next generation glazingLisbon, with Portugal dynamic Abstract b

Veolia Innovation, 291 Dreyfous Limay, France buildings. A study is modulation cof transparency, toRecherche suitably& modulate theAvenue daylight and Daniel, solar 78520 energy entering Département Systèmes Énergétiques et Environnement IMT Atlantique, 4 rue Alfred Kastler, 44300 Adaptive facades, electrochromic (EC)effects smart windows, represent the nextofgeneration of Nantes, glazingFrance with dynamic reported, dealing like with the manifold of building integration an innovative solid-state EC modulation of transparency, to building suitably energy modulate the daylight and solar energy entering buildings. A Daylight study is device, assessing effects on the balance and daylighting performance, in terms of Useful Illuminance (UDI) and Glare Index All the analyses wereofcarried out using the experimental reported, dealing withDiscomfort the manifold effects(DGI). of building integration an innovative solid-state EC results, reporting effects the main of merit of EC devices an input forperformance, building simulations, in Useful the EnergyPlus device, assessing on figures the building energy balance andasdaylighting in terms of Daylight Abstract Illuminance (UDI) and Discomfort Glare Index (DGI). All the analyses were carried out using the experimental software. results, reporting the main figures of merit of EC devices as an input for building simulations, in the EnergyPlus District heating networks are commonly addressed in the literature as one of the most effective solutions for decreasing the software.

greenhouse gas emissions from the building sector. These systems require high investments which are returned through the heat © 2018 The Authors. Published by Elsevier Ltd. Due to the changed climate conditions renovation policies, heat demand in the future could decrease, ©sales. 2018 The Authors. by Elsevier Ltd. and building This is an open accessPublished article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0/) prolonging theaccess investment This is an open articlereturn underperiod. the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0/) Selection and peer-review under © 2018 The Authors. Published by responsibility Elsevier Ltd. of the scientific committee of the 73rd Conference of the Italian Thermal Selection peer-review underisresponsibility of the scientific committee the 73rd Conference of the Italian Thermal Machines The mainand scope of this paper to assess the feasibility of using the heatof demand – outdoor temperature function for heat demand This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0/) Machines Engineering Association (ATI 2018). Engineering Association 2018). forecast. The district of(ATI Alvalade, located in Lisbon (Portugal), was used as a case study. The district is consisted of 665 Selection and peer-review under responsibility of the scientific committee of the 73rd Conference of the Italian Thermal buildings that vary in both construction period and typology. Three weather scenarios (low, medium, high) and three district Keywords: Smart windows; Machines Electrochromic Engineering Association (ATISolid-state; 2018). Building-integration; Energy balance; Visual comfort; Control strategy. renovation scenarios were developed (shallow, intermediate, deep). To estimate the error, obtained heat demand values were compared with results from a dynamic heat demand model, previously developed and validated by the authors. Keywords: Electrochromic Smart windows; Solid-state; Building-integration; Energy balance; Visual comfort; Control strategy. The results showed that when only weather change is considered, the margin of error could be acceptable for some applications 1. Introduction (the error in annual demand was lower than 20% for all weather scenarios considered). However, after introducing renovation scenarios, the error value increased up to 59.5% (depending on the weather and renovation scenarios combination considered). 1. Introduction Electrochromic windows, also on known as within “smartthe windows”, represent “green” nanotechnology (1). They The value of slope (EC) coefficient increased average range of 3.8% up toa 8% per decade, that corresponds to the are capable of regulating the throughput of solar during radiation in dynamic glazing and yielding better energy decrease in the number of heating hours of 22-139h the heating seasontintable (depending on the combination of weather and Electrochromic windows, known as function “smart windows”, represent “green” nanotechnology (1). They renovation scenarios(EC) considered). On also the other hand, intercept increased for a7.8-12.7% per decade (depending on the are capable of regulating the throughput of solar radiation in dynamic tintable glazing yielding better energy coupled scenarios). The values suggested could be used to modify the function parameters for and the scenarios considered, and improve the accuracy of heat demand estimations. * Corresponding author. Tel.: +39 0805963718.

© E-mail 2017 The Authors. Published by Elsevier Ltd. address: [email protected] Peer-review under responsibility of the Scientific Committee of The 15th International Symposium on District Heating and * Corresponding author. Tel.: +39 0805963718. Cooling. 1876-6102 © 2018 The Authors. Published by Elsevier Ltd. E-mail address: [email protected]

This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0/) Keywords: Heat demand;under Forecast; Climate change Selection peer-review of the scientific 1876-6102and © 2018 The Authors. responsibility Published by Elsevier Ltd. committee of the 73rd Conference of the Italian Thermal Machines Engineering Association (ATI 2018). This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0/) Selection and peer-review under responsibility of the scientific committee of the 73rd Conference of the Italian Thermal Machines Engineering Association (ATI 2018). 1876-6102 © 2017 The Authors. Published by Elsevier Ltd. 1876-6102 © 2018 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the Scientific Committee of The 15th International Symposium on District Heating and Cooling. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0/) Selection and peer-review under responsibility of the scientific committee of the 73rd Conference of the Italian Thermal Machines Engineering Association (ATI 2018). 10.1016/j.egypro.2018.08.096

2

Alessandro Cannavale et al. / Energy Procedia 148 (2018) 900–907 Author name / Energy Procedia 00 (2018) 000–000

901

efficiency than static solutions (2). EC behavior is shown by several materials, like transition metal oxides (typically subdivided into two kinds: cathodic and anodic, showing a complementary fashion), but also organic ECs (especially conjugated polymers and small molecules) (3). Tungsten oxide (WO3) is the most investigated cathodic EC material; on the other hand, a typical anodic, inorganic EC oxide is nickel oxide (NiO). The reversible EC coloration/bleaching process, for the above mentioned inorganic oxides, is explained by means of two simple redox reactions (4). EC devices based on transition metal oxides typically show a multilayered, battery-like architecture (5). They generally contain transparent conductive substrates, an interposed (liquid, gel or solid) electrolyte and two complementary EC materials. Electron insertion (extraction, if anodic EC materials are considered) from the transparent conductive oxide and the consequent intercalation (de-intercalation, in the anodic EC case) of charge balancing cations from the electrolyte cause the modulation of optical absorption. Conventional liquid or gel electrolytes generally suffer from poor structural stability, tendency to leak and evaporate, with irregularities and non-uniform coloration (6). For this reason, this relevant component is undergoing a research effort, worldwide, to produce innovative solid electrolytes, overcoming these drawbacks. Solid polymer electrolytes (SPE) and solid-state devices are currently under study to achieve low processing costs, electrochemical stability, flexibility, easy scalability (7), but also higher duration, architectural simplification and reduction of impacts and costs (8). One of the authors (9) reported a newly designed robust and full solid-state EC device fabricated on a single substrate, adopting a thin Nafion film (8 μm thick) as a suitable solid electrolyte, sharing its interfaces with a WO 3 layer and a highly transparent and conductive RF-sputtered ITO film, deposited at room temperature with values, to our knowledge, among the best found for solid-state EC devices (10–13). Building integration of smart glazing in the architectural envelope may lead to manifold advantages in terms of energy savings on real buildings as well as visual comfort enhancements: the dynamic modulation of the energy throughput of glazing affects energy consumption in summer, cutting out a large part of undesired solar gains; furthermore, it influences visual comfort indoor by maximizing the use of daylighting and reducing the use of artificial lighting. Lampert (14) explained that EC smart glazing require powering only upon switching, with small voltages and generally show durable memory (up to 48 h), also being compatible with large-area fabrication. DeForest et al. (15) adopted the EnergyPlus software platform to simulate annual energy performance of a dualband EC glazing capable of modulating, separately, visible and near infrared radiations, in three building types and several US climate regions. They estimated the savings potential of such windows, capable of achieving annual primary energy savings between 6 kWh/ft2yr and 30 kWh/ft2yr per window area, reducing heating, cooling, and lighting. In a previous work (16), they found that the conventional EC windows were suitable for “cooling dominated” climates, like the Mediterranean area, outperforming near-infrared switching EC glazing. Lee et al. (17) studied visual comfort and energy implications of EC windows equipped with overhangs, finding significant reductions of average annual daylight glare index (DGI) and relevant energy savings (10%) with high Window-to-Wall-Ratio (WWR). Peak electric demand can be reduced by 14–16 % for large-area windows in either climate. The same group (6) reported results from a full-scale demonstration of building-integrated large-area ECs, (WWR of 0.40). As a result EC windows provided greater energy efficiency and improve environmental quality, if compared to conventional window systems generally adopted in buildings. Lighting energy savings reached 91%, compared to the existing lighting system in a conference room in Washington, simulated using Energy Plus platform to estimate annual energy savings (48%) and peak demand savings (35%) (18). Tavares et al. carried out an energy performance simulation of buildings in Mediterranean climates, comparing three glazing options: single glass, conventional double glazing and EC glazing, finding energy savings of 20.28 and 36.94 kWh/m2yr per windows surface in the east/west facades, showing that the EC glasses might be an energyefficient solution for buildings, also in case of refurbishment (19). Other relevant studies were reported by Aldawould (20) and by Syrrakou et al. (21). The latter carried out an eco-efficiency analysis on an EC prototype, showing that cost and environmental efficiency could be achieved at the same time by adopting this technology in buildings: EC glazing theoretically reduce the building energy requirements by 52%, in cooling dominated areas. In a recent work, we studied the energy and visual comfort performance of a reference office building equipped with different glass technologies on the façade (clear glass, solar control, EC glasses), in different climates (Rome, London and Aswan). The new EC technology presented, also used in this study, outperformed all the others, with overall yearly energy savings as high as 40 kWh/m2yr (referred to window surface) in the hottest climates, assuming

902

Alessandro Cannavale et al. / Energy Procedia 148 (2018) 900–907 Author name / Energy Procedia 00 (2018) 000–000

3

the clear glazing as benchmark. Daylighting performance was also improved using innovative solid-state EC devices: 82.7% of hours achieved optimal illuminance conditions on an annual basis, in the best case (22). 2. Methodology The EC devices (later on referred as CNR-EC) were fabricated on a single substrate, made of glass or flexible plastics, with a simplified architecture based on substrate/ITO/WO 3/Nafion/ITO configuration, in which a Nafion film (with a thickness of 8 µm) tightly shares its interfaces with the WO 3 layer and the highly transparent and conductive RF-sputtered ITO film [10].

Fig. 1. (Left) Transmittance spectra of device under bleached and colored conditions in the range wavelength between 400 nm and 1500 nm. (Middle) CNR_EC Device in bleached and colored conditions. (Right) Test room used as a building model in this work.

The whole fabrication process of this innovative compact and lightweight device (Figure 1 – middle) was completely carried out at room temperature, as described elsewhere (23). The electro-optical and electrochemical properties of the devices, assessed by spectrophotometry (transmittance and kinetic spectra) reported coloration efficiency of 139 cm2/C, and an optical contrast of 49 % (at 650 nm – Figure 1, left), with a switching response time of 30 s and a very low electric energy absorption (of about 80 mJ/cm2) required to achieve a complete and homogeneous coloration (90% of maximum optical modulation). The building model used in this study (Figure 1, right) was a test room having a size compatible with an office (4.0 m x 5.0 m x 3.5 m) and a high value of WWR = 0.42. The façade equipped with one South exposed stripped window (4.0 m x 1.5 m). Detailed simulations were carried out with reference to Rome (Mediterranean climate, Csa according to Koppen-Geiger classification) using the IWEC (International Weather for Energy Calculations) database developed by ASHRAE within the Research Project 1015. All the analyses were carried out using the free simulation tool EnergyPlus v. 8.9 developed by the U.S. Department of Energy’s Building Technology Office, for modeling thermal loads and performing energy analysis of whole buildings or single building zones. EnergyPlus models are defined by building geometry, envelope characteristics, mechanical system characteristics, and occupancy and setpoint schedules. In order to determine the heating and cooling energy consumptions in a simple and straightforward way, and also avoid making assumptions on more detailed plant characteristics, an “IdealLoadAirSystem” with no outdoor air was considered. This EnergyPlus object provides both the heating and cooling energy required to meet the temperature set-points that have been provided by the relevant schedules. As the IdealLoadAirSystem returns exactly the thermal energy that must be provided, to convert such value into electrical energy, a constant COP of 3 was assumed for both heating and cooling modes. Heating was assumed to be turned on during working hours and off during nights and holydays and limited to a period from November 1st to April 15th (Climatic area D, Rome), while cooling was turned on from June 1st to September 30th. Envelope thermal resistance was 0.56 m 2K/W for ground floor, 1.45 m2K/W for roof, and 0.46 m2K/W for walls. Daily internal load condition and pattern fraction of occupants, lighting,

4

Alessandro Cannavale et al. / Energy Procedia 148 (2018) 900–907 Author name / Energy Procedia 00 (2018) 000–000

903

and equipment were 10.76 W/m2 for both lighting and equipment loads in the office building and an occupancy rate of 18.58 m2/person. Fenestration was assumed to have thermal–optical properties of a simple double-pane glazing system (6 mm-clear glass/20 mm-air gap/6 mm-clear glass) as a baseline model, ideally representing existing building conditions. Clear glass pane was a 6 mm Clear Glass. However, the use of this kind of glazing is being discouraged by energy saving regulations in many countries, and was considered as a reference for “Refurbishment Scenario”, whereas a spectrally selective glazing (SGG Cool-Lite KN-155) was considered as representative of New Buildings Scenario. More data are reported in Table 1. Data used to simulate EC glazing were calculated starting from spectral data collected by the authors and the required input values were then calculated. Table 1. Optical data about glazing technologies adopted. Glazing features as modelled. Parameter values were calculated using LBNL Window 7.5 software starting from glazing features. For Electrochromic glaz- ings values pertaining to bleached and fully tinted configuration are given.

Window type Clear Glass (Refurbishment Scenario) Selective Glass (New Building scenario) CNR-EC

Visible transmittance (Tvis)

U-Factor (W/(m2K))

SHGC

0.787

2.720

0.716

0.470

1.900

0.360

0.409, 0.027

1.980

0.439, 0.113

Within the model, one sensor was placed in a median position, for the evaluation of natural lighting metrics, on the longitudinal axis of the test room, set to minimum illuminance of 300 lx. This is a value corresponding to the de facto standard for screen-based office tasks, though lower than the value prescribed by international standards (24). Therefore, the EC system always operated in order to achieve this lighting requirement on the work plan. Two comfort parameters chosen for assessing the visual comfort benefits of building integrated EC glazing were Useful Daylight Illuminance (UDI) and Discomfort Glare Index (DGI), employing the output from EnergyPlus software. The UDI parameter, developed by Nabil et al. (25), considers absolute daylight illuminance levels on hourly-based meteorological data, over a period of a full year. UDI are defined as percentages of time in which sensors’ illuminances fall within a range of values that is considered comfortable by the users. According to previous literature reviews (based on occupants’ preferences and behaviors) (26,27), a range of 300–3000 lx has been considered suitable. Daylight illuminances lower than 300 lx are generally considered insufficient; daylight illuminances higher than 3000 lx are likely to produce visual or thermal discomfort. On the other hand, glare indeed represents a critical factor affecting the level of visual comfort in daylit office spaces. DGI was then estimated at each reference point as reported in the Engineering reference Manual of EnergyPlus (28), Chapter 7, paragraph 7.3.4. Recommended value here adopted for maximum allowable DGI, referred to activity and zone type, was 22 for daylit offices, as reported in Table 2. 28 of the Input Output Reference Documentation of EnergyPlus (28). Analyses were carried out with reference to working hours only (from 8:00 AM to 6:00 PM). With reference to the electrochromic glazing, various transmission strategies have been hypothesized for their control. The first one was based on the illuminance measured on the sensor, positioned in the center of the room. According to this criterion, the transparency of the CNR EC glazing was directly dependent on the illuminance on the work table, set at a minimum value of 300 lx. The second management strategy was based on the value of the DGI measured in the sensor, setting a threshold value of 22. Finally, a further possible strategy of dynamic management of transparency was adopted, depending on the value of solar irradiation outside the electrochromic glass, thus aiming to separate the system operation from the actual amount of daylighting entering indoor. For this purpose, three threshold values have been adopted for irradiation on the external wall (200 W/m2, 250 W/m2, 300 W/m2). In glare and irradiancebased scenarios, artificial lighting was used in order to reach the setpoint value of 300 lx, in the sensor. 3. Results and discussion Table 2 shows a comparison between the total annual electricity consumption in the test room, in different scenarios. The table admits two possible comparisons, allowing to verify the benefits in terms of yearly energy

Alessandro Cannavale et al. / Energy Procedia 148 (2018) 900–907 Author name / Energy Procedia 00 (2018) 000–000

904

5

savings both in a Building Refurbishment scenario (energy retrofit of the building) and in a New Building scenario (embodying glazing complying with current standards). For this reason, the comparison was performed between a test room equipped with CNR_EC glazing and a test room equipped with a transparent common glass, but also with one employing high performance selective glass. In parallel, the energy and daylighting performance of the CNR_EC glazing was further analyzed according to the control strategy of dynamic transparency, in order to reveal how different management strategies may affect energy consumption and visual comfort as well. The relevance of the EC management strategy was demonstrated by the fact that either the best and the worst energy performance were obtained precisely using the EC glass with different strategies, respectively based on the work plane illuminance (575 kWh/yr) and the control of glare (971 kWh/yr), to be compared with the reference scenario (730 kWh/yr). The unfavorable result obtained using the glare-control strategy was due to extra uses of energy for lighting and heating. Then, notwithstanding the attainable relevant savings in cooling during the summer season, a net increase of 33% in total yearly electric energy uses was observed. Quite predictably, the operation of dynamic screening during winter (using a glare control strategy) leads to a reduction of solar gains and therefore determines on the one hand the increase in the number of hours in which artificial lighting is used and, on the other, an increase in energy consumption for heating. Better results can be achieved with a strategy control based on the work plan illuminance monitoring (set at 300 lx). In this case, the increase in consumption for artificial lighting was reduced to 20 %, while consumption for winter heating was 29 % higher than the value observed in the Refurbishment scenario (clear glass). Table 2 also allows to check the amount of energy saving for cooling in summer mode. The most performing strategy was decidedly the one based on the work plan illuminance. The overall energy saving compared to the Refurbishment scenario was in the order of 13% (8%, compared to New building scenario). On the other hand, the management strategy based on the irradiance impinging the external façade of the South exposed window, whatever the value of the irradiance threshold set for the activation of the dynamic transmittance control (200 W/m2, 250 W/m2, 300 W/m2), did not offer newsworthy performance: in the best case, the overall yearly energy consumption was the same observed in the reference case, due to the poor performance observed in lighting consumption (+ 75%) and heating (+29%). The reason for this result, somewhat disappointing, lies in the decoupling between the active control of the transparency of the EC glass and the actual illuminance conditions on the sensor placed on the work plan (set at 300 lx): this inevitably leads to an increase in the hours when artificial lighting is on. This point suggested to use a “rolling” CNR_EC device, fabricated on a PEN film, to be conveniently dropped into the glass only during the summer season (from June 1st to September 30th): in this way, in the winter season, all the solar gains can be conveniently exploited, so as to reduce heating loads and limit artificial lighting. Under this configuration, the CNR_EC outperforms all the other technology configurations and management strategies, on an annual basis. The total energy savings achievable with the latter solution reached 21% compared to the reference Refurbishment Scenario. This strategy combines the benefits deriving from the availability of full transparency of glass in the winter to the advantage of a dynamic management of transparency in the summer. Table 2. Overall yearly energy consumption.

Clear Glass (Refurbishment Scenario)

150

126

454

Overall yearly energy consumption (kWh) 730

Selective Glass (New Building scenario)

161

141

394

697

-5

CNR_EC_Illuminance controlled

180

163

294

636

-13

CNR_EC_Illuminance controlled – Summer use

155

126

294

575

-21

CNR_EC_glazing_Glare controlled

491

169

311

971

+33

CNR_EC_Irradiance_controlled (200W/m2)

274

163

309

746

+2

CNR_EC_Irradiance_controlled (250W/m2)

263

163

309

735

+1

CNR_EC_Irradiance_controlled (300W/m2)

252

163

310

725

-1

Overall yearly energy consumption

Lighting (kWh/yr)

Heating (kWh/yr)

Cooling (kWh/yr)

Difference in total energy consumption (%) -

Author name / Energy Procedia 00 (2018) 000–000 Alessandro Cannavale et al. / Energy Procedia 148 (2018) 900–907

6

905

Values reported in Table 3 show the results obtained simulating seven different scenarios of daylighting penetration in the test room, so as to provide an assessment of the UDI level on a yearly basis, in office hours. What can be clearly observed is that all the hypothesized strategies offer highly heterogeneous values in the penetration of daylighting on an annual basis during office hours. In particular, it is observed that, in all cases, the percentage of hours in which the illuminance value falls within the UDI range (i.e. between 300 lx and 3000 lx) spanned between 0.2% (CNR_EC Glare controlled) and 78.3% (New Building Scenario): once again, the best performing management strategy for CNR_EC was the illuminance-based one (68.5% of hours in UDI range). The irradiancebased strategy performance, quite predictably, reported high percentages of poorly illuminated hours (between 46.8 and 52.3%). Table 3. UDI distribution in the reference scenarios. Evaluated Scenario

Low Illuminance (< 300 lx)

UDI (between 300 lx and 3000 lx)

Refurbishment (Clear glass)

15.5

64.6

19.9

New building (Selective glass)

20.1

78.3

1.7

EC Illuminance controlled

31.5

68.5

0

EC Glare controlled

99.8

0.2

0

EC Irradiance controlled (setpoint 200 W/m2)

52.3

47.7

0

EC Irradiance controlled (setpoint 250 W/m2)

48.8

51.2

0

EC Irradiance controlled (setpoint 300 W/m )

46.8

53.2

0

2

High Illuminance (>3000 lx)

The further comparison, examining the DGI figure of merit (Figure 2), provided additional elements for checking the levels of visual comfort obtained adopting various strategies, mutually compared, within the test room. In particular, the results obtained showed that the best performance were achieved by adopting the glare-based strategy (100% of hours with DGI< 22) and the illuminance-based strategy (61.1% of hours with DGI< 22). This analysis confirmed that the best management strategy for CNR-EC glazing was by far represented by the illuminancecontrolled one. This work has allowed us to verify the benefits that can be obtained by integrating the innovative solid-state CNR_EC technology developed by one of the authors, ascertaining, moreover, what the best control strategy can be, in order to mitigate energy consumption, on the one hand, and to guarantee, on the other hand, the best use of daylighting in the confined space.

Fig. 2. Histograms showing the percentage of hours with DGI values lower than 22, according to the selected simulation scenario.

Alessandro Cannavale et al. / Energy Procedia 148 (2018) 900–907 Author name / Energy Procedia 00 (2018) 000–000

906

7

4. Conclusions In this paper, experimental data resulting from the fabrication and electro-optical characterization of a solid state EC device were used as an input for simulation activities (in EnergyPlus environment) oriented to assess the manifold benefits associated with of building integration of EC devices in architectural glazing, according to the control strategy adopted. For this purpose, various control strategies of the EC function were compared, based respectively on the work plane illuminance (setpoint: 300 lx), on glare control (DGI