Development and characterization of a multifonctional window for energy savings and indoor air quality – WINFIL

Two types of ionizer (wire-plates and needles / optics), different geometries of collector, and several installations of the ESP were considered based on airflow simulations in the parieto dynamic window. Each configuration has been tested on a dedicated test rig with controlled airflow rate. KCl (mainly submicronic) and alumine (micronic) particles were generated at the device inlet. The most suitable system design will be determined based on measurements of the spectral filtering efficiency of the window, pressure drop, and the amounts of by-products formed. Then, a comprehensive parametric study of the influence of airflow rate, air temperature and humidity, and polarity / voltage of the ionizer and collector will be carried out. The data will be used to develop a black box model of particles, ozone and NOx transfers through the WINFIL window. The latter will be implemented into a transient IAQ model accounting for internal emissions, advective transports, deposition onto materials and coagulation processes. Numerical simulations using time series of outdoor concentrations and internal emissions as inputs will make it possible to compare the occupants' chronic and acute exposures with WINFIL or regular windows installed in a specified building. Finally, on-site measurements over long times, with the ESP turned on and off, will allow to higlight possible discrepancies between lab measurements and numerical simulations on the one hand, and real operation conditions on the other hand. These discrepancies may for instance result from uncontrolled changes in the chemical composition of the outdoor aerosol, or dust accumulation on the collector.

Various ESP design have been tested on a dedicated test bench. The results are promising since efficiencies greater than 90% have been measured for a wide range of particle sizes, with low electric power and pressure loss. Unlike the wire-plate technology, ionization by the needle / optical technology generates small amounts of ozone and nitrogen oxides in the circulating air.

The next step of the study will be to decide the final design and position of the ESP within the window. A comprehensive study of parameters influencing the device performance will be carried out. Besides, on site measurements will be achieved to show the IAQ improvement by the WIINFIL window in real conditions, and validate the model.

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The WINFIL project combines industrial and fundamental research with a view to developing and characterizing the efficiency of an innovative window having an electrostatic precipitator filter on the fresh air inlet. The window in which the filtering system will be implemented is a brand new airflow window with improved parieto-dynamic effect; it has advanced energy and acoustic properties. The implementation of an efficient and easy to maintain particle filter will lead to an integrated product which will meet the current challenge of designing energy efficient and healthy buildings. The WINFIL window will contribute to energy savings by decreasing the energy loss and pre-heating the fresh air. In addition it will also significantly improve the occupants’ exposure to fine and coarse particles in urban and suburban areas. These are is major health, social and economic concerns in France.
Two electrostatic filtration technologies will be optimized and evaluated. In the first, the charge of particles will be provided by a wire-plate system, as conventionally found in the electrostatic precipitators. In the second, the discharge electrodes will be needles, such as those used in the portable air ionic cleaners.
The project has been divided into 3 steps.
• The first task will consist in defining the technical specifications of the filtering system in view of its implementation in the existing airflow window. The experimental methodology will also be defined.
• The second task will consist in developing and optimizing the WINFIL window from experiments on a test bench (air line with controlled conditions and concentration measurements upstream and downstream of the windows); various technical configurations of the filter and environmental conditions at the filter inlet will be tested. The particle collection efficiency will be measured for a wide range of diameters (20 nm to 20 µm) under operating conditions representative of atmospheric air in urban areas. In addition, the ozone and nitrogen dioxide emission rates and energy consumption will be measured. Beyond the initial performance of the device, the impact of the fouling of the collection electrodes will also be evaluated by performing experimental tests with high particle concentrations and long experimental time.
• The indoor air quality improvement resulting from the implementation of the innovative window in a building will then be assessed by two methods (task 3): 1/ measurements of particle, ozone and nitrogen oxide concentrations inside and outside a scale-1 experimental room, and 2/ numerical simulations of the indoor air quality in buildings equipped with the window and operating in various representative configurations of outdoor particle concentrations and ventilation pattern. Experiments in a test chamber will also be carried out to characterize the coagulation kinetics and the deposition of charged particles in indoor environments. The modelling of these phenomena is a key issue in the dynamic modelling of particle transports from outdors to indoors, through the WINFIL window, and therefore in an accurate prediction of the occupants' exposure.