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  • 1.
    Paz, Ana
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Moisture content determination from dielectric properties of solid biofuels2010In: Aquametry 2010 Proceedings, Weimar, Germany, 2010, p. 318-325Conference paper (Refereed)
  • 2.
    Paz, Ana Marta
    Mälardalen University, School of Sustainable Development of Society and Technology.
    The dielectric properties of solid biofuels2010Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The use of bioenergy has been increasing due to efforts in fossil fuels replacement. Modern bioenergy technologies aim for high efficiency and low pollution levels, which increases the need for methods for the on-line characterization of biofuels.

    Dielectric methods have been identified as useful for the sensing of solid biofuels because they allow for rapid, nonhazardous, nondestructive, and bulk determination of material properties. The dielectric properties describe the interaction between the material and the electromagnetic waves. Dielectric properties are intrinsic of the materials and can therefore be used for the development of prediction models that can be applied regardless of the measurement technique. The study of the dielectric properties is also important as it improves the understanding of the dielectric behavior of the materials.

    This thesis focuses on the dielectric properties of solid biofuels and their use in the characterization of these materials. The work presented includes the development of new methods permitting the determination of the dielectric properties of solid biofuels with large particle size (waveguide method), broadband measurement of the dielectric properties (coaxial-line probe), and the use of a previously developed method for the accurate determination of the dielectric properties (free-space method). The results includes the dielectric properties of solid biofuels and their dependence on parameters such as frequency, moisture, density, and temperature.

    This thesis also presents semi-theoretical models for the determination of moisture content, which obtained a RMSEP of 4% for moisture contents between 34 and 67%, and an empirical model that resulted in a RMSEC of 0.3% for moisture contents between 4 and 13%.

    Finally, this thesis includes measurements of the influence of salt content on the dielectric properties and a discussion of its use for estimation of the ash content of solid biofuels.

    

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  • 3.
    Paz, Ana
    et al.
    Mälardalen University, Department of Public Technology.
    Nyström, Jenny
    Thorin, Eva
    2006 IEEE Instrumentation and Measurement Technology Conference Proceedings2006In: IEEE Instrumentation and Measurement Technology Conference Proceedings, 2006, p. 175-179Conference paper (Refereed)
    Abstract [en]

    A method that permits the determination of moisture content in biofuel in a fast and representative way is under development. Vie method uses radio frequency waves within the range of 310 MHz to 800 MHz and measures the reflection coefficient in samples with volume of about 0.1 m(3). The influence of sample temperature in the measurements is shown in this study. Two biofuel types were used, with moisture content varying between 31% and 63% and temperature varying between 1 degrees C and 63 degrees C. The data was evaluated with multivariate data analysis. Results show that it is not possible to identify the sample temperature as a principal component in a principal component analysis and partial least squares regression shows no correlation between temperature and the radio frequency data. For the frequency interval and the temperature range studied, it was not possible to detect any influence of sample temperature on moisture content prediction with the radio frequency method.

  • 4.
    Paz, Ana
    et al.
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Starfelt, Fredrik
    Dahlquist, Erik
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Thorin, Eva
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Yan, Jinyue
    Mälardalen University, School of Sustainable Development of Society and Technology.
    How to achieve a fossil fuel free Malardalen region2007In: Conference proceedings of 3rd IGEC-2007,, 2007Conference paper (Refereed)
  • 5.
    Paz, Ana
    et al.
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Thorin, Eva
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Dahlquist, Erik
    Mälardalen University, School of Sustainable Development of Society and Technology.
    A new method for bulk measurement of water content in woody biomass2008In: 3rd Conference on environmental compatible forest products, 2008Conference paper (Refereed)
  • 6.
    Paz, Ana
    et al.
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Thorin, Eva
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Nyström, Jenny
    Eskilstuna Energi och Miljö.
    Complex Permittivity of Woody Biomass at Radio FrequenciesManuscript (preprint) (Other (popular science, discussion, etc.))
  • 7.
    Paz, Ana
    et al.
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Thorin, Eva
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Nyström, Jenny
    Eskilstuna Energi och Miljö.
    Dielectric Properties of Woody Biomass at Radio Frequencies2009In: Proceedings of the 8th International Conference on. Electromagnenetic Wave Interaction with Water and Moist Substances, Helsinki, 2009Conference paper (Refereed)
    Abstract [en]

    Electromagnetic sensing has been found an interesting technique for the characterization of woody biomass. The knowledge of the dielectric properties is useful for this characterization and to improve the understanding of the dielectric behavior of the material. This study presents the dielectric properties of woody biomass at a center frequency of 555 MHz. A measurement system, previously developed, to determine the water content of biomass was used. This system uses a reflection method and measures a biomass volume of about 0.11 m3. The dielectric properties were extracted from attenuation and velocity of the electromagnetic waves in three types of woody biomass with varying water content.

  • 8.
    Paz, Ana
    et al.
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Thorin, Eva
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Topp, Clarke
    Agriculture and Agri-food Canada.
    Dielectric mixing models for water content determination in woody biomass2011In: Wood Science and Technology, ISSN 0043-7719, E-ISSN 1432-5225, Vol. 45, no 2, p. 249-259Article in journal (Refereed)
    Abstract [en]

    The aim of this study is to determine the dielectric constant of woody biomass at different water contents and describe its behavior with a dielectric mixing model. The use of the model for determination of water content is also verified. Dielectric constants were calculated from the travel times of electromagnetic waves with a center frequency of 555 MHz through collected biomass samples. The power law, Maxwell-Garnett, and Polder van Santen mixing models were applied to the experimental data. In the models, biomass was considered as a mixture of three phases: a solid solution composed of wood cellular material and bound water, free water, and air. The experimental data was found to be better described by the Maxwell-Garnett model. The use of this model along with an independent validation set for the determination of volumetric water content resulted in a root mean square error of prediction of 0.03 within the investigated volumetric water content range of 0.07-0.29.

  • 9.
    Paz, Ana
    et al.
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Trabelsi, Samir
    Nelson, Stuart
    Dielectric properties of peanut-hull pellets at microwave frequencies2010In: 2010 IEEE International Instrumentation and Measurement Technology Conference, I2MTC 2010: Proceedings, 2010, p. 62-66Conference paper (Refereed)
    Abstract [en]

    Peanut-hull pellets are obtained from a waste product, peanut hulls, which after pelleting can have several uses, namely as a renewable fuel. Rapid and nondestructive characterization of peanut-hull pellets is important for industrial utilization of this resource. Properties such as moisture content and bulk density are important for quality control and pricing and control of the energy conversion process. The dielectric properties of peanuthulls pellets can be used for the development of rapid and nondestructive sensors. In this study, the dielectric properties of peanut-hull pellets were measured at frequencies between 5 and 15 GHz, for moisture contents between 4% and 13%, temperatures between -15 °C and 38 °C, and bulk densities between 0.54 and 0.69 g·cm-3.

  • 10. Paz, Ana
    et al.
    Trabelsi, Samir
    Nelson, Stuart
    Thorin, Eva
    Influence of sodium chloride on sawdust dielectric propertiesIn: IEEE Transactions on Instrumentation and Measurement, ISSN 0018-9456, E-ISSN 1557-9662Article in journal (Refereed)
  • 11.
    Paz, Ana
    et al.
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Trabelsi, Samir
    ARS, USDA, Richard B Russell Agr Res Ctr, Athens, GA 30605 USA.
    Nelson, Stuart
    ARS, USDA, Richard B Russell Agr Res Ctr, Athens, GA 30605 USA.
    Thorin, Eva
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Measurement of the Dielectric Properties of Sawdust Between 0.5 and 15 GHz2011In: IEEE Transactions on Instrumentation and Measurement, ISSN 0018-9456, E-ISSN 1557-9662, Vol. 60, no 10, p. 3384-3390Article in journal (Refereed)
    Abstract [en]

    The aim of this paper was to measure the broadband dielectric properties of sawdust. Knowledge of dielectric properties is important in improving understanding of a material and can lead to the development of methods for determining physical properties such as moisture and salt content. The broadband dielectric properties of sawdust were measured with an open-ended coaxial-line dielectric probe. Measurements on granular materials with the dielectric probe are dependent on the density of the measured region, which may differ from the average density of the sample. In this paper, a method was developed for determining the actual density for measurements with the dielectric probe. It consists of measurement of the dielectric constant with a different method (in this instance, a free-space transmission method) at a frequency common to both methods and identifying a relationship between the measured dielectric constant and density. The dielectric properties of sawdust samples with moisture content levels between 13% and 45% are presented for frequencies between 0.5 and 15 GHz.

  • 12.
    Paz, Ana
    et al.
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Wester, Lars
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Combustion of rapeseed oil for heat production2007In: IGEC III Conf, 2007Conference paper (Refereed)
  • 13.
    Trabelsi, S.
    et al.
    Agricultural Research Service, U.S. Department of Agriculture.
    Paz, Ana Marta
    Mälardalen University, School of Business, Society and Engineering.
    Nelson, S. O.
    Agricultural Research Service, U.S. Department of Agriculture.
    Microwave dielectric method for the rapid, non-destructive determination of bulk density and moisture content of peanut hull pellets2013In: Biosystems Engineering, ISSN 1537-5110, E-ISSN 1537-5129, Vol. 115, no 3, p. 332-338Article in journal (Refereed)
    Abstract [en]

    A rapid dielectric-based method was used to non-destructively determine the moisture content and bulk density of peanut-hull pellets from free-space measurement of their dielectric properties at microwave frequencies. For moisture content determination, a permittivity-based function was used that permits moisture prediction independent of bulk density from measurement of the dielectric properties at microwave frequencies. For bulk density determination, an analytical expression was obtained from a representation of the dielectric properties in the complex plane. Results of moisture and density prediction from measurement of the dielectric properties are shown at 5, 10, and 15GHz at 22°C. •Dielectric properties of peanut hull pellets were measured in free space between 5GHz and 15GHz at 22°C. © 2013.

  • 14. Trabelsi, Samir
    et al.
    Paz, Ana
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Nelson, Stuart
    Dielectric-based method for determining moisture content and bulk density of peanut-hull pellets2010In: 44th Annual Microwave Symposium Proceedings, 2010, p. 190-196Conference paper (Refereed)
1 - 14 of 14
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