Thermal performance of solar cooker with special cover glass of low-e antimony doped indium oxide (IAO) coating

Accepted Manuscript Research Paper Thermal performance of solar cooker with special cover glass of low-e antimony doped indium oxide (IAO) coating S.S. Ghosh, P.K. Biswas, S. Neogi PII: DOI: Reference:

S1359-4311(16)32865-4 http://dx.doi.org/10.1016/j.applthermaleng.2016.10.185 ATE 9387

To appear in:

Applied Thermal Engineering

Received Date: Revised Date: Accepted Date:

25 June 2016 6 October 2016 29 October 2016

Please cite this article as: S.S. Ghosh, P.K. Biswas, S. Neogi, Thermal performance of solar cooker with special cover glass of low-e antimony doped indium oxide (IAO) coating, Applied Thermal Engineering (2016), doi: http:// dx.doi.org/10.1016/j.applthermaleng.2016.10.185

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Thermal performance of solar cooker with special cover glass of low-e antimony doped indium oxide (IAO) coating S. S. Ghosh1, P. K. Biswas2,*, S. Neogi1 1

School of Energy Studies, Jadavpur University, Kolkata 700 032, West Bengal, India

2

Department of Physics, Indian Institute of Technology Roorkee, Roorkee 247 667, Uttarakhand, India

Abstract Indium, cadmium and tin based transparent conducting oxide (TCO) films have low thermal emissivity values and these are suitable for energy efficient applications where controlling of thermal effect is an important factor. Among these films antimony doped indium oxide (IAO) coated glass has been explored to have resistivity ~2 X 10 -2 Ω cm. The film is homogeneous and good adherence to glass even in large dimensions [500 mm X 500 mm]. This film possesses emissivity ~0.63 and it has been taken as the standard for the calculation of solar factor (g i) and absorbed solar energy reradiated and convected indoors (E i) of transparent conducting oxide (TCO) films of 32 types. As calculated, the gi and Ei values of a TCO films are in the ranges 0.77 to 0.02 and 2.9 to 59 Wm-2 respectively. Attempt has been made to use the IAO coated glass to improve glazing system in solar cooker with the principle that lowering of gi and Ei values would correspond to significant increase of heat insulation property. The thermal performance of solar cooker box having a cover of single layer low-e IAO coated glass was compared with the solar cooker box having a cover of uncoated double glaze soda lime silicate (SLS) glass initially and finally with the same solar cooker box with evacuated glazed cover maintaining vacuum (10-3 atm.) in the glazing system. Thermal performance of the solar cookers at ambient condition differs due to the variation of heat flow through glass cover with different glazing 1

systems. The performance was promising for the solar cooker box with the cover of single glazed low-e IAO coated glass. The added advantages for domestic usage are low cost of production, relatively light weight and high mechanical durability along with relatively high thermal output.

Keywords: Solar cooker, Solar factor; Solar energy admittance; Thermal efficiency; Antimony doped indium oxide (IAO) coated glass, Low-e glass

*Corresponding author: Honorary Fellow, IITR, Roorkee-247667 India, Ph: +91 1332 286678 (O), +91 9433011304(M), e-mail: [email protected], [email protected], formerly Chief Scientist, CSIR‐CGCRI; †major work was executed at CSIR-CGCRI, India in collaboration with the School of Energy Studies, Jadavpur University, Kolkata-700032

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1. Introduction With the increasing crisis of fossil fuel, scientists are looking for renewable energy sources for various applications. Amongst all renewable energy sources, solar energy is the major and most abundant source of energy which has versatile scope in the surface irrigation [1-3], specially agricultural [4,5] purpose. We have the specific energy requirement [6] for evapotranspiration [7,8] processes which can be fulfill by utilization of renewable energy resources. Various types of devices have already been developed to transfer solar energy into other form of energy resources considering the local ambient condition [9] for practical application regarding the prosperity of social-economic life [10,11]. As for example, solar cooker is an important device which can be used widely for domestic purpose and it is effective for tropical countries, where abundant solar energy is available throughout the year. Such device is found to be convenient in domestic houses for heating, boiling and baking materials utilizing the normal solar radiation. Attempts have been made by various authors for modeling of box type [12,13], parametric [14] and mathematically designed [15] solar cookers. Design parameters have also been modified [16,17] to achieve improved performance [18] of solar cooker in stationary mode. Solar cookers are found to be widely used device in Egypt [19], Brunei [20], Turkey[21] etc.. Suitably doped and undoped cadmium oxide [22-26], indium oxide [27-31] and tin oxide [32-34] semiconductors deposited on glass as thin films have low thermal emissivity (low-e) application (Table-1). These types of films are transparent in the visible range and opaque (after plasma wavelength) to IR (infra red) radiation. Both the emissivity and the optical transmission of the films are relatively low with respect to those of uncoated soda lime silica glass. These create lower value of solar heat gain factor in the films. Moreover, increase in electrical 3

conductivity value with the decrease in plasma wavelength reflects the films to behave as more NIR (near infra red) opaque resulting in the utilization of solar radiation of NIR range. Different types of low-e films have been developed till date, which are been applied in window glazing [35], OLED [36], thin film photovoltaic [37] etc. In our earlier works the authors have established that antimony doped indium oxide film (IAO) with low-emissive property have potential application as transparent conducting oxide material [31] and can effectively be used as a heat absorbing material in window glazing[38]. In the present work the authors tried to reveal the potential application of IAO film as cover in solar cooker box. Based on the idea of heat reflecting property of low-e film, which is better than uncoated SLS glass, can be useful for commercial utilization and replacement of uncoated glass in solar cooker box. The application of low-emissive film as cover in solar cooker box is a new approach and need to reveal specially in the area of thermal engineering. In principle, solar cooker allows the visible solar radiation to enter the system through its cover and subsequently this visible radiation is converted to heat after absorption by the absorbing surface. As the cover glass is opaque to IR radiation, it entraps heat within the cooker [39]. This entrapped heat increases the inside temperature of the cooker which is thus utilized for cooking [40]. Researchers have attempted to compare the thermal performance of solar cooker box by changing design parameters [41, 42], tracking equipments [43-45] and also the materials [46,47]. In this report the authors have compared the performances of solar cookers having different types of covers with a variation of temperature gain inside the cooker. The present research work emphasizes on the calculation of solar factor (from BS & ISO)[48,49] and absorbed solar energy reradiated and convected indoors (from ASTM)[50] of 4

the films along with measurement of electrical conductivity leading to the determination of most effective low-e values of the films as these are applicable for understanding the useful thermal effect of solar cooker glass cover. 2. Experimental The authors have concentrated on the soft chemistry based sol-gel processing for the material development as this has several advantages. A number of transparent conducting oxide (TCO) coatings on glass have been prepared by sol-gel dip coating process to perform low-emissivity and wide band gap semiconducting properties. The general flow diagrams of TCO film preparation are given in the following Sections.

2.1 Preparation of host metal sol Host metal salt was dissolved in solvent or mixture of solvents with stirring. Sol may be heated if required. Stirring was continued for 1 hour by magnetic stirrer for better homogenization. The final sol was designated by Sol A.

Host metal salt

Solvent or mixture of solvents

Heating (if required) Host metal sol

stirring

stirring

Sol A

2.2 Preparation of doped metal sol Doped metal salt was dissolved in solvent or mixture of solvents with stirring. Sol may be heated, if required. Stirring was continued for 1 hour by magnetic stirrer for better homogenization. The final sol was designated by Sol B.

5

Doped metal salt

Solvent or mixture of solvent

Heating (if required) Doped metal sol

stirring

Sol B

stirring

2.3 Preparation of precursor sol Sol A and Sol B were mixed quantitatively with constant stirring. Stirring was continued for 1 hour more to homogenize the mixture. Then quantitative amount of solvent or solvent mixture was added to the stirring solution slowly to maintain concentration. Complexing agent may be added according to requirement. Finally requisite quantity of wettable agent was added to the above suspension to make it clear and good wettable nature over glass substrate. The stirring was continued for next 5-7 hrs. The precursor sol of desired concentration of equivalent mixed oxide of host and doped (atomic ratio, 90-99:10-01) was then ready for its use in the coating operation. Sol A + Sol B

Solvent mixture Mixture sol stirring

Complexing agentstirring

Dispersed Wettable agent stirring sol

Wettable precursor

stirring Final precursor sol (ready for coating)

2.4 Formation of gel film

Ultrasonically cleaned sodalime silicate (SLS) glass slides were dipped in and lifted from into the precursor bath at 8 cm/min in a dip coater in open atmosphere of 1000 scale clean room laboratory. 2.5 Formation of film The samples were then placed inside the atmosphere controlled furnace and heating started in air/oxygen/nitrogen/mixture gas (Ar+H2 mole ratio 95:5) atmosphere from room temperature, 250C - 300C to 5000C (±100C). The rate of heating was maintained at 5-60C/min. 6

When the targeted temperature reached, samples were soaked for 1 hr. After soaking, cooling started at the rate 5oC/min. When the temperature reached in the range, 150 0C - 2000C, the gas purging was stopped. The furnace temperature was left to cool down to room temperature, 250C - 300C. The samples were then taken out of furnace and preserved. The acronyms of 32 types of TCOs are written in Table 2. Among them the most conducting IAO-7 film coated glass of dimension 500 mm X 500 mm was used as glass cover in solar cooker. The details of conductivity of IAO film has already been discussed in our earlier work[31]. 2.7 Thermal performance of solar cooker The experiments with solar cookers were performed at Calcutta (22°37′ N, 88°23′ E), India. For the determination of inside temperature of solar cookers, different temperature sensors were used. Suitable sensor was placed inside solar cooker which was provided with 500mm X 500mm uncoated double glass cover, evacuated glazed cover and indium antimony oxide (IAO) coated low-e glass cover and the tests were performed following Indian Standard (IS-13429) [51]. The detailed method of fabrication of evacuated glazing is already presented [52, 53] and glass coating by indium antimony oxide (IAO) as low-e application is described in our previous work [31]. The instrumental errors of the temperature sensors are as given by the company specifications. These error ranges do not alter with the reading of data. Hence, the authors need to minimize the errors generated while recording the temperature data as per given specification. Initially the authors have placed both the sensors within solar cooker with low-e IAO coated single glass cover. The temperatures were recorded manually. The curves show there will be 7

difference in temperature ~5.8°C after steady state reached [Figure 1]. Similar observations were recorded for solar cooker with evacuated double glaze cover. As a result the authors need to add up 5.8°C with dial gauge reading to have comparable reading to that of recorded by resistance temperature detector (RTD). For the comparison, sensor 1 (dial gauge) was placed inside solar cooker with uncoated double glaze cover and sensor 2 (RTD) was placed inside the solar cooker having evacuated glazed cover [Figure 2]. The test was performed on 2 nd February, 2014. The temperature readings of the individual sensors were recorded with certain time intervals and it was continued until a steady state reaches. The data of sensor 1 was then added up by 5.8°C to have the comparable reading to that of sensor 2 to minimize error. The position of temperature sensors within the solar cooker box are shown in the Figure 2. The calibrated curves are shown in the Figure 3. In each case, the sensors were placed at same position expecting the data collected for each system would be evolved out experiencing similar geometric feature around the tip of the sensor. It may also be expected that similar error may be developed for each case, but the comparative data may enlighten about the quality of performance for each system. All the data are practically relative with respect to each system. Similarly, another experimental set up was developed where one sensor 1 (dial gauge) was placed inside solar cooker with uncoated double glaze cover and sensor 2 (RTD) was placed inside solar cooker having low-e (IAO coated) glass cover. The test was performed 11 th April, 2014. The sensor readings were recorded and the data was then converted as per calibration described earlier. The position of temperature sensors within the solar cooker box are shown in the Figure 4. The calibrated curves are shown in the Figure 5.

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For closure monitoring of temperatures three thermocouples were calibrated. Among them thermocouple 219 and 220 (as identified earlier) were used for solar cookers and another for the measurement of ambient temperature. These thermocouples were calibrated against thermometer reading. The resulting regression lines are nearly rectilinear. From the calibrated equations the authors have converted the data into equivalent temperatures and minimized the errors in temperature readings. For the comparison of thermal performance between solar cooker with evacuated glazed cover and low-e IAO coated single glass cover, the authors used same solar cooker with continuous monitoring of temperature by calibrated thermocouples. The hot junctions of thermocouples were placed within the cooker in the same manner as described in the earlier section. The thermocouples were designated as 219 and 220 for recording of temperatures within cooker box having evacuated glazed cover and low-e IAO coated single glass cover respectively. In the final set up the authors attempted for closer monitoring of temperature data of both the cookers and record simultaneously throughout the day with change in solar insolation and ambient temperature. Four different calibrated thermocouples were utilized for determination of solar insolation, ambient temperature, inside cooker temperature having evacuated glazing and low-e glass cover. The test was performed following Indian Standard (IS) on 25th April, 2014. Individual thermocouple readings were transformed to equivalent temperature using calibration equation and plotted against daytime [Figure 6]. The output data were characterized and discussed as followed.

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3. Characterization In the present study the simple box type of solar cookers are used with different top cover configuration & balance of the system remains unaltered. Several temperature sensors were used in the experimental work to determine the inside temperature of solar cooker box. Among which thermocouple was best suited temperature sensing device [54] considering better sensitivity and closure monitoring. As specified by the standard test methods (ASAE S580, 2003; IS 13429, 2000) [55,51], the cookers were tested without the reflector for evaluating its performance[56]. The RTD is Pt-100 digital thermometer with model no. BPO/195 of accuracy 0.2% of FSR and working under 9V potential difference. The dial gauge is made of SuKuGu having temperature sensitivity range 0°C to 160°C. The thermocouples are set up with ‘hp’- data logger model 34970A with continuous monitoring using hp bench link data logger software. The solar pyranometer was made by Water Technologies with serial no. 007164.

4. Results and discussion From ISO and BS calculation solar factors of 32 coatings were determined. Table 3 shows glasses of lower emissivity which have relatively low solar factor values. The authors considered IAO-7 coated glass as standard sample which has emissivity, ϵ= 0.63, lower than that of SLS glass (ϵ= 0.84). Calculation for the determination of solar factor is shown in annexure I, establish the model as qualitatively validated. ASTM model is based on the absorbed radiation, which is reradiated and convected inside. From the ASTM calculation, amount of heat transfer inside the room is shown in the Table 4 and the calculation for amount of quantitative heat transfer towards inside is shown in the Annexure II. 10

The experiment which was performed on 2nd February, 2014, the temperature sensors were placed inside the solar cooker containing uncoated double glaze and evacuated glaze cover, as discussed earlier. The resultant curve shows steady state reaches within one hour [Figure 3]. In that condition, the temperature in the evacuated glaze system is ~7°C more than that of uncoated due to convective heat transfer between two glass panes is less in vacuum [40] than in air filled double glaze SLS glass. Similarly, 7 at.% antimony doped indium oxide (IAO-7) coated low-e glass was set as cover glass in solar cooker and the temperature profile was recorded on 11 th April, 2014, and this was compared with that of uncoated double glaze system. The detail of the experimental set up has already been discussed in the previous section. From the temperature data of two sensors, the calibrated temperature readings were plotted against time [Figure 5]. The curves show (except little fluctuation in readings) the heat gain in the unsteady state, in case of low-e coated glass, is more than that of uncoated glass. The temperature lag in the unsteady state is due to the heat transfer through low emissive glass is relatively low with respect to that of uncoated glass [37]. This temperature lag is finally compensated in the steady state region by retention of more heat within the uncoated double glaze system and there would be no significant difference of temperature observed once the steady state is reached. Both the applied glazing systems (evacuated and low-emissive) were needed to be closer monitoring of temperature. Hence, the corresponding temperatures and radiation data were plotted against time [Figure 6] using thermocouples, as experimented on 25th April, 2014, at Calcutta (22°37′ N, 88°23′ E). The curves show temperature rise within evacuated glazed system is more than that of the low-e coated glass used as cover for solar cooker. The difference in

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temperature is ~10°C in the steady state and both are enough to reach boiling water temperature (table-5). The authors can judge the thermal performance of solar cooker from figure of merit [23], which is defined as in the equation (i) , F=[ Optical efficiency/ overall heat loss coefficient] = (TP - TS)/Is ……………………………….(i) Where, F is figure of merit (Km2w−1), Tp is absorber plate temperature (∘C), Ta is ambient temperature (∘C), and I s is insolation on a horizontal surface (Wm−2). From the equation, the authors calculate, for maximum insolation, the figure of merit for uncoated double glazed, evacuated glazed and low-e glass are 0.07 Km2W−1, 0.09 Km2W−1 and 0.08 Km2W−1 respectively. It signifies both the solar cooker are of grade B type [3]. Though considering cost, fabrication, handling and utility of solar cooker, low-e glass cover is more effective. Annexure I Qualitative analysis from BS EN 410:2011 [48] and ISO/DIS 9050- 1987 [49] Solar factor gi= τe + qi

……………………………….(ii)

Heat flux inside qi= αe X f

……………………………….(iii)

αa=23 Case I (high emissive glass, ϵ= 0.84) αi=3.5+ 5.4 X0.84=3.5+4.54=8.036 f=αi/(αi+αa)

……………………………….(iv)

= 8.036/(8.036+23) =8.036/31.036 =0.259 Case II (low emissive glass, ϵ=0.63) αi=3.5+ 5.4 X0.63=3.5+3.4=6.9 12

f= αi/(αi+αa)

……………………………….(iv)

=6.9/(6.9+23)=6.9/29.9=0.23 where ,

τe = direct solar transmission (%), ρe = direct solar reflection (%), αe = direct solar

absorption (%), ϵ = emissivity, αi = direct solar absorption inside, αa= direct solar absorption outside, f= constant for a sample Annexure II Quantitative analysis from ASTM E-424-71 – 2007[50] absorbed solar energy reradiated and convected indoors = 230 ASET(%) hi (hi + ho)/100 …..(v) =75.29 ASET(%)/100 hi (hi + ho)= 1.46/4.46=0.3274, as hi=1.46 (from standard) and ho=3(assumption) Total solar energy flux on earth= 435 Btu hr. -1 ft-2 =1372Wm-2 From Table 4 for low emissive IAO-7 glass absorbed solar energy reradiated and convected indoors Ei = 2.9 Btu hr.-1 ft-2 = 9.17 Wm-2 Where, TSET (%) = Total solar energy transmission (%), RSET (%) = Total solar energy reflection (%), ASET(%) = 100 - TSET (%) - RSET (%),hi = heat transfer coefficient towards inside, ho= heat transfer coefficient towards outside Low-e glass behaves differently to that of uncoated double glass. The uncoated double glass entraps air within the double glass pane, which restrict conductive heat transfer. The solar cookers with IAO coated single glass cover have no such effect. Rather, low-e film has lower value of cut off wavelength in the IR range than that of uncoated glass, which reduces loss of heat due to internal reflection in the IR range. The authors have observed both the systems generate equivalent amount of heat within box cooker under similar circumstances, as

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temperature gain in the steady state reaches the same value [Figure 4], can be identical to each other regarding thermal performance of solar cooker box. Whereas, solar cookers with evacuated glaze cover performs little better than solar cookers with low-e IAO coated single glass cover, which is identical to solar cooker box with uncoated double glass cover. Our experiment shows temperature rise in both the systems exceeds 100°C [Figure 6] which is enough for boiling of water and use in commercial purpose [for solar cookers with evacuated glazed cover, maximum temperature rise ~125°C and to that of low-e IAO coated single glass cover ~118°C]. The solar cookers with evacuated glazed cover is less preferable over solar cookers with low-e IAO coated single glass cover due to difficult to manufacture, high cost of production, more weight and tough to handle (table-5). Hence, solar cookers with low-e IAO coated single glass cover, which is identical to uncoated double glass covered solar cooker box regarding thermal performance, is considered to be more preferable for domestic usage rather than solar cookers with evacuated glazed cover. As the plasma wavelength of low-e IAO glass is less than uncoated SLS glass, the radiative heat loss becomes more restricted for the cooker box having low-e IAO glass cover than uncoated SLS glass cover. In comparison, evacuated glazed performs differently than low-e glass. The level of vacuum maintained within the glass panes of evacuated glazing system signifies less amount of convective heat transfer occur than usually used non-evacuated system as less amount of particles present within the annular space of glass sheets in the evacuated system. Though, the radiative heat transfer in these two cases is identical. As low-e glass and evacuated glazed system performs differently, initially authors tried to compare these two systems with uncoated double glaze covered cooker box separately. These experiments were performed manually with different sensors, which 14

were later conducted by replacing uncoated glass for both the cases in a single experiment. In the later work, multiple calibrated thermocouples were utilized to measure ambient temperature and the change of temperature of the cooker boxes having evacuated glaze cover and low-e IAO coated single glass cover with solar radiation. The comparative thermal performances have already been discussed in the previous section. Though, low-e double layer IAO coated SLS glass can give better result than the single later as used in the present system. Further research work is going on these areas which are needed to be characterized and compare with various glazing system for the development of better performing solar cooker.

5. Conclusion There are certain advantages to use single glass pane rather than double glass pane, which are, i) less in weight, ii) ease of handling, iii) lower materials cost than evacuated glaze and iv) the chances of rupture due to thermal shock is less. Experiment shows both the solar cooker with uncoated double glass pane cover and solar cookers with low-e IAO coated single glass cover have similar thermal performances. Hence, solar cookers with low-e IAO coated single glass cover is better preferable over other two types of double glass pane covered solar cooker due to above reasons. In the paper work the authors have experimented with single side IAO coated glass. The both side IAO coated glass can be used for better thermal performance, which cause rise in materials cost. As a result, single side IAO coated glass is convenient, enough and sufficient for domestic use (as temperature of cooker box rise above 100°C) over commercially used box type solar cookers having double glass pane cover.

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The low-e coated glass performs similar to that of uncoated double glazing SLS glass when steady state reached. Whereas, evacuated glazed double pane SLS glass conceives nearly ~10°C more temperature than low-e coated glass. Low-e coated single glass pane is less weighty sometimes more economic than double glazing SLS glass. Low-e glass is selected considering better utility in solar cooker. But evacuated glazed double pane SLS glass is selected considering better thermal performance. From Table 3, the authors can observe the reduction of emissivity (from 0.84 to 0.63) which reduces gi value. Whereas Table 4 shows absorbed solar energy reradiated and convected indoors is less in IAO-7 coated films than that of uncoated glass. Though, less conducting, the other films show good result regarding lower value of g i and Ei, which was not taken to the consideration duo to film inhomegenity and poor adherence. Researches on other types of low value of gi and Ei may develop promising results, which is out of the scope of the present work.

Acknowledgements Authors acknowledge the Director of CSIR-CGCRI for providing instrumental facilities to characterize the developed materials. One of the authors (SSG) gives special thanks to CSIRHRDG for offering him fellowship (CSIR-SRF).

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[25] H. M. Ali, H. A. Mohamedy, M. M. Wakkad, M. F. Hasaneen, Optical and electrical properties of tin-doped cadmium oxide films prepared by electron beam technique, Jap. J. of App. Phys. 48 (2009) 041101:1-7 [26] T. J. A. R. Hitch, C. L. Honevboume, Vapour sensing properties of a cadmium oxide– antimony oxide system ceramic Cd2Sb2O6.8, J. Mater. Chem. 6 (1996) 285-288 [27] M.A. Flores, C.R. Pérez, G.T. Delgado and O.Z. Angel, Cadmium oxide, indium oxide and cadmium indiate thin films obtained by the sol–gel technique, Thin Solid Films. 518 (2009) 1114–1118 [28] S. Kundu and P. K. Biswas, Synthesis and photoluminescence property of nanostructured sol–gel indium tin oxide film on glass, Chem. Phys. Lett. 414 (2005) 107–110 [29] P. K. Biswas, A. De, N. C. Pramanik P. K. Chakraborty, K.Ortner, V. Hock, S. Korder, Effects of tin on IR reflectivity, thermal emissivity, Hall mobility and plasma wavelength of sol- gel indium tin oxide films on glass, Mater. Lett. 57 (2003) 2326 -2332 [30] J. Choisnet , L. Bizo, R. Retoux, B. Raveau, Antimony and antimony–tin doped indium oxide, IAO and IATO: promising transparent conductors, Solid State Sci. 6 (2004) 1121–1123 [31] S.S. Ghosh, S. Neogi, P.K. Biswas, Microstructural and optical characterizations of sol–gel based antimony doped indium oxide coatings on glass, J. Sol Gel Sci. and Technol., 71 (2014) 530-539 [32] F.de Moure-Floresa, J.G. Qui˜nones-Galván, A. Hernández-Hernández, A. GuillénCervantes, M.A. Santana-Aranda, M. de la L. Olvera, M. Meléndez-Lira, Structural, optical and electrical properties of Cd-doped SnO2 thin films grown by RF reactive magnetron co-sputtering, App. Surf. Sci. 258 (2012) 2459– 2463 [33] P.K. Manoj, Benny Joseph, V.K. Vaidyan, D.S.D. Amma, Preparation and characterization of indium-doped tin oxide thin films, Ceramics International 33 (2007) 273–278 [34] C.C. Terrier, J. P. Chatelon, J.A. Roger, Electrical and Optical Properties of Sb:SnO 2 Thin [35] Jeffrey Rissman, Hallie Kennan, Low-emissivity windows, Case studies on the government’s role in energy technology innovation, American energy innovation council (2013) [36] Vandana Singh, C.K. Suman, Satyendra Kumar, Indium Tin Oxide (ITO) films on flexible substrates for organic light emitting diodes, ASID, New Delhi (2006) 388-391

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[37] Frank U Hamelmann, Transparent Conductive Oxides in Thin Film Photovoltaics, Journal of Physics: Conference Series, INERA Workshop of ISCMP2014, 559 (2014) 012016 [38] S.S. Ghosh, P.K. Biswas, S. Neogi, Effect of solar radiation at various incident angles on transparent conducting antimony doped indium oxide (IAO) film developed by sol–gel method on glass substrate as heat absorbing window glass fenestration, Solar Energy, 109(2014)54–60 [39] V. John, R. Jagadeswaran, K.G. Satyanarayana, A solar cooker for the common man, Res. and Ind. 30 (1985) 1-5. [40] F. Joshua, Performance evaluation of a double-glazed box-type solar oven with reflector, J. of Ren. Energy, 184352 (2013) 1-8. [41] K.S. Malhotra, N.M Nahar, B.V.R. Rao, An improved solar cooker, Int. J. of Energy Res 6 (1982) 227-231. [42] R.S. Mishra, S.P.S.J. Prakash, Evaluation of solar cooker thermal performance using different insulating materials, Int. J. of Energy Res. 8 (1984) 393-396. [43] M. Balakrishnan, A. Claude, D.R.K. Arun, engineering, design and fabrication of a solar cooker with parabolic concentrator for heating, drying and cooking purposes, Archives of App. Sci. Res. 4 (2012) 1636-1649 [44] S. John, N.V. Shanmugam, E. Vidyasagaran, Studies on a new combined concentrating oven type solar cooker, Energy Conv. and Man. 32 (1991) 537-541. [45] J.D. Walton, Development of a solar cooker using the spiral Fresnel concentrator, Appropriate Technol. 10 (1983) 27-29. [46] N.M. Nahar, R.H. Marshall, B.J. Brinkworth, Studies on a hot box solar cooker with transparent insulation materials, Energy Conv. and Man. 35 (1994) 787-791. [47] N.M. Nahar, Design, development and testing of a double reflector hot box solar cooker with a transparent insulation material, Ren. Energy. 23 (2001) 167-179. [48] ISO/DIS9050, Glass in building- Determination of light transmittance, direct solar transmittance, total solar energy transmittance nd ultraviolet transmittance, and related glazing factors, 1987 [49] BS EN 410, Glass in building. Determination of luminous and solar characteristics of glazing, 2011

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[50] ASTM E-424-71, Standard test methods for solar energy transmittance and reflectance (terrestrial) of sheet materials, 2007 [51] IS 13429, Solar cooker-box type-specification, part 3, 2000. [52] A. Ghosh, J.H. Trevor, S. Neogi, Thermal characterization of process control parameters for the fabrication of evacuated glazing, Int. J. of Emer. Technol. and Adv. Eng, ICERTSD 2013, 3 (2013) 305-310. [53] S. bhattacharya, Development of advance glazing system for energy efficient windows, M.Tech thesis, Energy Science and Technology, Jadavpur University, Kolkata, 2011 [54] C. D. Henning, R. Parker, Transient response of an intrinsic thermocouple, J. Heat Transfer 89 (1967) 146-152 [55] ASAE S580, Testing and reporting of solar cooker performance, 2003. [56] M.N. Ozisik, Heat Transfer, McGraw-Hill Book Co, 1994

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List of Tables Table 1: Comparison among various TCO properties of metal oxide semiconductors as thin film/pellet having different dopant contents at different annealing temperatures. Table 2: Details of sample ID Table 3 : Calculation of direct solar transmission, reflection and solar factor from BS EN 4101998 [48] and ISO/DIS 9050- 1987 [49] Table 4: Calculation of total energy gain by inside window glazing from ASTM E-424-71 – 2007 [50] Table 5: Comparative analysis among different type covers of solar cooker to focus prospective commercial application of cookers

22

List of Figures Figure 1: Temperature recorded using dial gauge and RTD within same solar cooker box with low-e IAO coated single glass cover Figure 2: Experimental set up of solar cookers with uncoated glass and evacuated glaze Figure 3: Temperature in solar cooker using evacuated glaze and uncoated double glaze as on 2nd February, 2014 Figure 4: Experimental set up of solar cookers with uncoated glass and also with low-e (IAO-7) coated glass Figure 5: Temperature in solar cooker using IAO-7 low-e window glass and uncoated double glaze as on 11th April, 2014 Figure 6: Thermal performance of double glaze film and IAO coated glass in solar cooker under solar radiation on 25th April, 2014

23

80

5.8 C

Temperature (deg. C)

75 0

70 65 60 55 50 45

Dial gauge reading RTD reading

40 35 30 25 0

10

20

30

40

50

60

Time to solar radiation (Minutes)

Figure 1: Temperature recorded using dial gauge and RTD within same solar cooker box with low-e IAO coated single glass cover

24

Evacuated glaze

Glass Sample sensor 1

sensor 2

Figure 2: Experimental set up of solar cookers with uncoated glass and evacuated glaze

25

80 Unsteady Zone

Temperature (deg. C)

75 70 65 Steady Zone

60 55 50 2

uncoated double glaze, R = 0.98887 2 3 -4 y = 46.05404 + 1.95271 x -0.05299 x + (4.93661 x )10 2 evacuated glaze, R = 0.97391 2 3 -4 y = 46.29812 + 2.18675 x -0.05384 x + (4.50232 x )10

45 40 35 0

10

20

30

40

50

Time to solar radiation (Minutes)

Figure 3: Temperature in solar cooker using evacuated glaze and uncoated double glaze as on 2nd February, 2014

26

Glass Sample IAO-7 Sample

Figure 4: Experimental set up of solar cookers with uncoated glass and also with low-e (IAO-7) coated glass

27

Temparature (deg. C)

100 90 80 70 60 50 2

IAO coated glass, R =0.98857 2 3 4 -5 y = 30.22225+ 7.1253x -0.30852x + 0.00593x - (4.15471x ) 10 2 uncoated double glaze, R = 0.99819 2 3 -4 4 -6 y = 29.79252+ 3.89118x -0.08607 + (7.9265E x ) 10 - (2.01381x ) 10

40 30 0

10

20

30

40

50

Time to solar radiation (minute) Figure 5: Temperature in solar cooker using IAO-7 low-e window glass and uncoated double glaze as on 11th April, 2014

28

Day time (hrs.) 9:47:03

11:27:03

13:07:03

14:47:03

900

O

800 700

300

600 500

Evacuated glaze IAO-7 coated glass solar radiation ........ Ambient temperature

200

400 300

100

200

2

Solar Radiation (W/m )

Solar Cooker Temp ( C)

400

100 0 0

5000

10000

15000

20000

0 25000

Cumulative time (seconds)

Figure 6: Thermal performance of double glaze film and IAO coated glass in solar cooker under solar radiation on 25th April, 2014

29

Table 1: Comparison among various TCO properties of metal oxide semiconductors as thin Dopant (~at. %) In(21)

Host metal Cd

Method of preparation Electron beam evaporation Sol-gel

Annealing Temp.(ºC) 350

Sn(5-20)

Electron beam evaporation

150-500

Sb(33)

Screen printing

250-500

Sol-gel

350

Sn(10)

Sol-gel

500

Sb(5)

Ceramization

600

resistivity 1.6 X 10-3 Ω cm

Sol-Gel

500

resistivity 1.5 X 10-2 Ω cm

RF reactive magnetron co-sputtering technique Sputtering technique

500

i) T 80-90% ii) Sheet resistence 373 Ω/□ iii) optical band gap ~4eV

400

Sol-gel

500

i) T 72.5%(550 nm) ii) resistivity 73.9 × 10-3 Ω cm iii) optical band gap 3.46eV resistivity 4.5 × 10-3 Ω cm

In(0-10)

Cd(16)

Cd(7)

In(10)

Sb(10)

In

Sn

350

Important Property(s)

Application

Reference

i) T 92% (NIR), 82% (vis) ii) resistivity ~10−1 i cm iii) optical band gap 3.4eV i) T >85% ii) resistivity 6.3×10−4 icm iii) optical band gap 3.1eV i) T 83-93% ii) resistivity 2.4X10-3 Ωcm to 4.4 X10-4 Ωcm iii) carrier conc 10 to 20cm-3 iv) mobility 10 to 45cm2 V-1s-1 v) optical band gap 3.1-3.3eV ‘chiral’ responses exhibited by Cd2Sb2O6.8 to limonene and pinene i) T >80% ii) resistivity 8×10−4 Ω cm to 106 Ω cm. i) resistivity 5 X 10-3 Ω cm ii) optical band gap 3.6eV

Transparent conducting oxide Transparent conducting oxide Transparent conducting oxide

[22]

Vapour sensing

[26]

Transparent conducting oxide Transparent conducting oxide (promising ) Transparent conducting oxide (promising) Transparent conducting oxide (promising) Transparent conducting oxide

[27]

Moderate electronic conductivity Transparent conducting oxide

[33]

film/pellet having different dopant contents at different annealing temperatures.

30

[23,24]

[25]

[28, 29]

[30]

[31]

[32]

[34]

Table 2: Details of sample ID

Sample ID CAO1 CAO4 CAO7 CAO10 CIO1 CIO4 CIO7 CIO10 CTO1 CTO4 CTO7 CTO10 IAO1 IAO4 IAO7 IAO10 ICO1 ICO4 ICO7 ICO10 TAO1 TAO4 TAO7 TAO10 TCO1 TCO4 TCO7 TCO10 TIO1 TIO4 TIO7 TIO10

Host metal ion cadmium cadmium cadmium cadmium cadmium cadmium cadmium cadmium cadmium cadmium cadmium cadmium indium indium indium indium indium indium indium indium tin tin tin tin tin tin tin tin tin tin tin tin

Doped metal ion antimony antimony antimony antimony indium indium indium indium tin tin tin tin antimony antimony antimony antimony cadmium cadmium cadmium cadmium antimony antimony antimony antimony cadmium cadmium cadmium cadmium indium indium indium indium

Host metal conc.(at %) 99 97 94 90 99 97 94 90 99 97 94 90 99 97 94 90 99 97 94 90 99 97 94 90 99 97 94 90 99 97 94 90 31

Doped metal conc.(at%) 1 4 7 10 1 4 7 10 1 4 7 10 1 4 7 10 1 4 7 10 1 4 7 10 1 4 7 10 1 4 7 10

Table 3 : Calculation of direct solar transmission, reflection and solar factor from BS EN 4101998 [48] and ISO/DIS 9050- 1987 [49] ϵ=0.84 ϵ=0.63 Sample %gi ρe τe αe ID qi gi=qi+τe qi gi=qi+τe reduce CAO1 7.42 71.87 20.72 5.37 77.23 4.76 76.63 0.78 CAO4 8.54 79.93 11.53 2.99 82.92 2.65 82.58 0.40 CAO7 7.99 82.12 9.89 2.56 84.68 2.27 84.39 0.34 CAO10 9.46 82.62 7.92 2.05 84.68 1.82 84.44 0.27 CIO1 3.97 73.56 22.47 5.82 79.38 5.17 78.72 0.82 CIO4 5.11 78.92 15.97 4.14 83.06 3.67 82.59 0.56 CIO7 5.38 66.23 28.39 7.35 73.59 6.53 72.76 1.12 CIO10 3.59 70.74 25.67 6.65 77.39 5.90 76.65 0.96 CTO1 3.86 76.21 19.93 5.16 81.38 4.58 80.79 0.71 CTO4 7.28 81.39 11.33 2.93 84.32 2.61 83.99 0.39 CTO7 6.85 77.31 15.84 4.10 81.41 3.64 80.95 0.56 CTO10 7.18 74.31 18.51 4.79 79.11 4.26 78.57 0.68 IAO1 14.42 81.68 3.90 1.01 82.69 0.89 82.58 0.14 IAO4 6.45 62.92 30.62 7.93 70.86 7.04 69.97 1.25 IAO7 10.39 79.21 10.40 2.69 81.89 2.39 81.59 0.37 IAO10 5.29 72.56 22.15 5.74 78.29 5.09 77.65 0.82 ICO1 11.20 77.77 11.02 2.85 80.63 2.54 80.31 0.39 ICO4 17.73 80.68 1.59 0.41 81.09 0.37 81.05 0.06 ICO7 9.88 63.19 26.93 6.98 70.17 6.19 69.39 1.11 ICO10 17.6 76.62 5.78 1.49 78.12 1.33 77.95 0.21 TAO1 8.94 82.87 8.19 2.12 84.99 1.88 84.75 0.28 TAO4 10.72 83.36 5.92 1.53 84.89 1.36 84.72 0.20 TAO7 14.18 82.40 3.42 0.89 83.29 0.79 83.19 0.12 TAO10 14.31 84.86 0.83 0.21 85.07 0.19 85.05 0.03 TCO1 14.44 79.78 5.78 1.49 81.28 1.33 81.11 0.21 TCO4 12.44 80.71 6.85 1.77 82.49 1.58 82.29 0.25 TCO7 11.65 81.49 6.87 1.78 83.26 1.58 83.06 0.24 TCO10 15.19 78.12 6.68 1.73 79.85 1.53 79.66 0.24 TIO1 17.29 70.71 12 3.11 73.82 2.76 73.47 0.47 TIO4 16.54 71.96 11.5 2.99 74.94 2.65 74.60 0.45 TIO7 21.22 70.07 8.72 2.26 72.32 2.00 72.07 0.35 TIO10 20.68 76.73 2.59 0.67 77.40 0.59 77.33 0.09 For the spectral data wavelength ranges 350-2100nm; all parameters are identified in the annexure -I

32

Table 4: Calculation of total energy gain by inside window glazing from ASTM E-424-71 – 2007 [50] Sample ID

T SET

R SET

T SET (%)

RSET (%) ASET(%)

absorbed solar energy reradiated and convected indoors (Ei) (W m-2) CAO1 740.67 7178.44 7.41 71.78 20.81 520.73 49.41 CAO4 850.4 7978.78 8.5 79.79 11.71 578.79 27.8 CAO7 795.52 8186.67 7.96 81.87 10.18 593.87 24.17 CAO10 944.66 8253.75 9.45 82.54 8.016 598.76 19.04 CIO1 406.44 7381.07 4.06 73.81 22.12 535.42 52.54 CIO4 512.87 7904.83 5.13 79.05 15.83 573.43 37.574 CIO7 547.81 6655.20 5.48 66.55 27.96 482.78 66.42 CIO10 363.49 7145.35 3.63 71.45 24.91 518.33 59.17 CTO1 386.82 7639.52 3.87 76.39 19.74 554.19 46.87 CTO4 739 8110.62 7.39 81.11 11.50 588.35 27.32 CTO7 695.39 7687.67 6.95 76.88 16.17 557.69 38.39 CTO10 724.57 7366.59 7.25 73.67 19.09 534.38 45.33 IAO1 1488.25 8202.04 14.88 82.02 3.09 595 7.35 IAO4 663.49 6552.48 6.63 65.52 27.84 475.34 66.11 IAO7 1089.89 7968.83 10.89 79.69 9.41 578.06 22.35 IAO10 557.03 7352.62 5.57 73.53 20.9 533.37 49.64 ICO1 1099.65 7775.15 10.99 77.75 11.25 564.03 26.72 ICO4 1816.24 8059.61 18.16 80.59 1.24 584.66 2.95 ICO7 1018.75 6477.41 10.19 64.77 25.04 469.88 59.46 ICO10 1813.3 7645.59 18.13 76.46 5.41 554.63 12.85 TAO1 870.11 8288.29 8.7 82.88 8.41 601.2 19.99 TAO4 1076.34 8303.69 10.76 83.04 6.19 602.35 14.72 TAO7 1391.57 8221.99 13.92 82.22 3.86 596.45 9.18 TAO10 1410 8470.33 14.1 84.7 1.19 614.46 2.84 TCO1 1447.09 7961.83 14.47 79.62 5.91 577.56 14.04 TCO4 1240.83 8059.33 12.41 80.59 6.99 584.63 16.62 TCO7 1152.84 8147.34 11.53 81.47 6.99 591.03 16.62 TCO10 1515.59 7821.3 15.16 78.21 6.63 567.37 15.75 TIO1 1667.82 7060.67 16.68 70.61 12.71 512.18 30.19 TIO4 1686.35 7130.83 16.86 71.31 11.83 517.26 28.09 TIO7 2133.82 6974.63 21.34 69.75 8.92 505.96 21.17 TIO10 2098.61 7693.17 20.99 76.93 2.08 558.07 4.94 For the spectral data wavelength ranges 350-2100nm; all parameters are identified in the annexure -II 33

transmitted solar energy (Btu hr.-1 ft-2)

Table 5: Comparative analysis among different type covers of solar cooker to focus prospective commercial application of cookers Samples Parameters Cost of production Maximum average temperature (°C) Fabrication technique Weight Handling Figure of merit (Km2w−1)

Uncoated double glazing low T

Evacuated glazing high T+15

Low emissive glass medium T

Nil ~4.8 kg Moderate easy 0.07

Critical ~5 kg tough 0.09

Easy ~2.4 kg easy 0.08

34

Highlights



Evacuated glaze covered solar cooker has better thermal performance than uncoated



32 different types of TCOs were experimented for high thermal insulation properties



Low-e IAO coated single glass covered solar cooker can be used



For domestic purpose, usage of low-e IAO glass is preferable specially in summer



Mainly due to low cost and ease of handling low-e IAO glass can be commercialized

35