Final Report Summary - TERMOGLAZE (Production of thermochromic glazings for energy saving applications)
Glazed surfaces are increasingly adopted in buildings but are responsible for the highest part of the energy needs of building (about 25-30 %), which constitute 40 % of total energy consumption in Europe. In a moderate climate, typical of European countries, buildings are subjected in some seasons to overheating, while high solar gains are desired to support space heating during other seasons. An optimal glazing should then have high solar transmittance in winter to enhance passive solar energy utilisation, while a low transmission in the solar infrared region in summer to avoid overheating or high cooling loads.
The aim of the TERMOGLAZE project was to realise a durable product and a cost effective production process for thermochromic glazed surfaces, with transition temperature and specifications optimised for different climatic conditions and different applications: glazed surfaces for buildings and greenhouses.
TERMOGLAZE aimed to realise:
1. A thermochromic glazing to be used as smart window for building application that adapts itself to the external climatic condition in order to optimise its behaviour, behaving like:
- a clear surface below the transition temperature:
a) high shading coefficient (i.e. high heat gain due to solar radiation)
b) high visible transmittance;
- a spectrally selective surface above transition temperature:
a) low shading coefficient (i.e. low heat gain)
b) high visible transmittance, hence without losing too much visibility to the outside.
The aim of the TERMOGLAZE project was to develop such an innovative product and an affordable and low cost production process.
2. A thermochromic pigment to be used on polycarbonate for greenhouse application to reduce energy consumption.
The main objectives of project were:
a) to define the expected requirements of the TERMOGLAZE and the specifications for the optical properties for the application to building and greenhouses;
b) to evaluate the influence of doping, the film thickness and the layer microstructure on the transition temperature and the optical properties of the glaze in the two physical states, and optimise these values for the application to building;
c) to evaluate the pigments to be used for greenhouses, study of degradation and influence of the binders;
d) to define the optimal process for the deposition of the TC layer onto a glazed surface: APCVD or a combination of CVD and PVD. To study the influence of the operative conditions and process parameters and evaluate the scale up and industrial feasibility;
e) to model the optical properties of the TC glazing, in particular with respect to layer thickness, to predict optimised thickness and to develop a simulation model for the application of TERMOGLAZE to building, in order to evaluate the energy consumption and predict the performance of the product;
f) to test stability of the TERMOGLAZE coating through forced ageing and scratch tests and test prototypes (both TC coating and pigments) under solar radiation, to verify the energy performances.
Main results achieved for the production process of TERMOGLAZE coatings:
- Undoped and metal doped VO2 thin films were deposited by AACVD, APCVD and DC magnetron sputtering.
- The films produced through APCVD and AACVD methodologies share many similarities such as growth method, adhesion and optical properties. Both the CVD methodology can be applied on a larger industrial scale. There are however some marked differences:
a) The crystallite size of the AACVD films is smaller than that of the APCVD produced films; this may lead to an additional drop in transition temperature for the AACVD films, although it is worth noting that the temperature drop per % tungsten doping is not dissimilar.
b) The main difference is that APCVD affords faster growth rates, which make this methodology more suitable for online coating applications; additionally the APCVD produced films were more uniform across the substrate than the AACVD produced films.
- AA / AP CVD hybrid technique was used to deposit Au@VO2 coatings. The presence of the nanoparticles changed remarkably the films colour, therefore solving one of the problems associated with the commercialisation of the product.
- Optimum processing conditions to form W doped films through DC magnetron sputtering with appropriate switching temperatures (20-30 degrees Celsius) and maximum transmittance ranging 40 % in the visible were established.
- First trials with a pulsed DC power supply, instead of continuous DC current, were successful in what concerns to the formation of VO2(M) films. However, an improvement of the VO2 properties is required.
The aim of the TERMOGLAZE project was to realise a durable product and a cost effective production process for thermochromic glazed surfaces, with transition temperature and specifications optimised for different climatic conditions and different applications: glazed surfaces for buildings and greenhouses.
TERMOGLAZE aimed to realise:
1. A thermochromic glazing to be used as smart window for building application that adapts itself to the external climatic condition in order to optimise its behaviour, behaving like:
- a clear surface below the transition temperature:
a) high shading coefficient (i.e. high heat gain due to solar radiation)
b) high visible transmittance;
- a spectrally selective surface above transition temperature:
a) low shading coefficient (i.e. low heat gain)
b) high visible transmittance, hence without losing too much visibility to the outside.
The aim of the TERMOGLAZE project was to develop such an innovative product and an affordable and low cost production process.
2. A thermochromic pigment to be used on polycarbonate for greenhouse application to reduce energy consumption.
The main objectives of project were:
a) to define the expected requirements of the TERMOGLAZE and the specifications for the optical properties for the application to building and greenhouses;
b) to evaluate the influence of doping, the film thickness and the layer microstructure on the transition temperature and the optical properties of the glaze in the two physical states, and optimise these values for the application to building;
c) to evaluate the pigments to be used for greenhouses, study of degradation and influence of the binders;
d) to define the optimal process for the deposition of the TC layer onto a glazed surface: APCVD or a combination of CVD and PVD. To study the influence of the operative conditions and process parameters and evaluate the scale up and industrial feasibility;
e) to model the optical properties of the TC glazing, in particular with respect to layer thickness, to predict optimised thickness and to develop a simulation model for the application of TERMOGLAZE to building, in order to evaluate the energy consumption and predict the performance of the product;
f) to test stability of the TERMOGLAZE coating through forced ageing and scratch tests and test prototypes (both TC coating and pigments) under solar radiation, to verify the energy performances.
Main results achieved for the production process of TERMOGLAZE coatings:
- Undoped and metal doped VO2 thin films were deposited by AACVD, APCVD and DC magnetron sputtering.
- The films produced through APCVD and AACVD methodologies share many similarities such as growth method, adhesion and optical properties. Both the CVD methodology can be applied on a larger industrial scale. There are however some marked differences:
a) The crystallite size of the AACVD films is smaller than that of the APCVD produced films; this may lead to an additional drop in transition temperature for the AACVD films, although it is worth noting that the temperature drop per % tungsten doping is not dissimilar.
b) The main difference is that APCVD affords faster growth rates, which make this methodology more suitable for online coating applications; additionally the APCVD produced films were more uniform across the substrate than the AACVD produced films.
- AA / AP CVD hybrid technique was used to deposit Au@VO2 coatings. The presence of the nanoparticles changed remarkably the films colour, therefore solving one of the problems associated with the commercialisation of the product.
- Optimum processing conditions to form W doped films through DC magnetron sputtering with appropriate switching temperatures (20-30 degrees Celsius) and maximum transmittance ranging 40 % in the visible were established.
- First trials with a pulsed DC power supply, instead of continuous DC current, were successful in what concerns to the formation of VO2(M) films. However, an improvement of the VO2 properties is required.
