Research Outputs

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Now showing 1 - 10 of 20
  • Publication
    Development of a Ti-doped Sodium Alanate Hydrogen Storage System
    (2009) ;
    Reissner, Alexander 
    ;
    Dudzinski, Piotr 
    ;
    Tajmar, Martin 
    A trade-off analysis regarding power supply on satellites, which was performed for the European Space Agency (ESA), suggested that fuel cells might be an interesting candidate to replace secondary batteries on satellites. The Austrian Research Centers (ARC) decided to approach this topic by combining a fuel cell with innovative chemical hydrogen and oxygen storage as well as integrating the oxygen storage system into a form that can be used as a structural element. Also an integration of the fuel cell into the hydrogen tank, and the resulting storage of dissipation heat, results in a reduction of the necessary thermal control system. These advantages are very interesting in order to obtain higher weight efficiencies, which are especially important for space and automotive applications. The complete system includes a hydrogen storage tank based on Ti-doped sodium alanate and a novel oxygen tank based on YBaCo4O7 developed at ARC. Water tanks and a micro-fluidic system connected to the fuel cell have been considered as well in order to provide a completely reversible system, competitive to batteries. For the hydrogen storage, a finite elements model has been developed, implementing the reaction kinetics of the storage process, in order to predict the thermal mechanisms during adsorption and desorption of hydrogen in sodium alanate. The present paper discusses these simulations, the development of an experimental hydrogen storage tank and the proposed concepts of a battery replacement system.
      97
  • Patent
      220  200
  • Publication
    Metal Hydrides as Hydrogen and Heat Storage System for Satellite Applications
    (2013-06-16)
    Reissner, Alexander 
    ;
    ;
    Hummel, Stefan 
    ;
    Scharlemann, Carsten 
    ;
    Tajmar, Martin 
      122
  • Publication
    Characterization of the Reversible Hydrogenation Properties of Sodium Alanate under various contaminated Hydrogen Conditions
    (2013-06-17)
    Reissner, Alexander 
    ;
    ;
    Hummel, Stefan 
    ;
    Scharlemann, Carsten 
    ;
    Tajmar, Martin 
      122
  • Publication
    Radiation Shielding Using Micro Cavities Filled with Highly Pressurised Gas
    (2012-11-29)
    Usually, hydrogen is stored under high pressure, in chemical compounds or in its liquid state requiring very low temperatures. Gaseous hydrogen can be stored in hollow glass microspheres (5 μm to 200μm diameters) under high pressure (350 bar to 700 bar). The sphere-wall is impermeable for hydrogen at ambient temperature; the heating of the spheres increases the diffusion of hydrogen through the wall. The Aerospace Engineering group of the FOTEC GmbH developed an innovative process for the European Space Agency that combines the storage concepts of hollow glass microspheres with chemical hydrogen storage. The combination of these two principles provides the advantages of both but cancels their respective drawbacks. Our analysis shows that such a system can reach hydrogen storage capacities of up to 10wt% in theory. This value depends on the sphere dimensions, the weight of the spheres, the hydrogen pressure, and the nature of the utilised hydride. The expertise gained in the course of the extensive research on gas storage in hollow microspheres lead to new applications for such a system. One of these applications is the use of microspheres filled with highly pressurized gas as radiation shielding material. Since hydrogen is very effective in absorbing the energy of highly energetic particles with minimal generation of secondary particles, it is particularly suitable for radiation shielding. Effective radiation shielding materials therefore often incorporate high concentrations of hydrogen. By using glass microspheres, it becomes possible to collect large amounts of hydrogen atoms with a relatively high gravimetric as well as volumetric density. It is also possible to store other light gases in the microspheres like deuterium or helium, in order to customize the absorption properties of the material. Preliminary calculations show that this technique can be used as radiation shielding with significant mass savings in respect to conventional materials. In comparison to aluminium for example, the hydrogen filled microspheres can shield high-energy protons and ions with 30% to 40 % increased efficiency. Also bremsstrahlung, secondary neutrons and gamma rays can be significantly reduced. Due to the fact that the material can be easily adapted to any given form, the possible terrestrial applications include: radiation shielding of aircrafts, shielding of computer and electronics, radiation shielding in research facilities as well as on medical sites, but also protective clothing for PCRs (Competent Person in Radioprotection). Considering the possibility to produce large amounts of such a material with relatively low cost, a broad industrial interest for such a light-weight and ultra-dense radiation shielding material can be expected. Also, the considered material is easy to handle with respect to safety and flexibility. Space technology could be used to protect the environment and the population against radiation. To make this technology available for terrestrial applications, the first step is the detailed assessment of the physical processes of gas-filled microspheres in a radioactive environment. It is then possible to investigate the best combination of gas species, microsphere properties, coating layer and support structure or binding material for different applications. The second step is the production of a prototype layer material based on filled microspheres and the testing of the radiation shielding properties of the new material. The Aerospace Engineering group is specialised in the development of micro propulsion and gas storage systems for space application. It has a long record of successful projects performed on behalf of the European Space Agency. As research and service provider of the University of Applied Sciences Wiener Neustadt, it is the ideal hub for educational, industrial and scientific projects. A test facility to test the catalyst efficiency and the thermal properties of the coated microspheres as well as filling the microspheres with different gases is available.
      96
  • Publication
    Micro-Propulsion and Power Developments at AIT
    (2009-01-12) ;
    Tajmar, Martin 
    ;
    Scharlemann, Carsten 
    The increasing application of micro-satellites (from 10 kg up to 100 kg) as well as CubeSats for a rising number of various missions demands the development of miniaturized propulsion systems. The Austrian Institute of Technology is developing a number of micropropulsion technologies including both electric and chemical thrusters targeting high-performance at small scales. Our electric propulsion developments include FEEP thrusters with thrust ranges from μN to mN using highly-integrated clusters of indium Liquid-Metal-Ion Sources providing ultralow thrust noise and long-term stability, as well as the development of a micro PPT thruster enabling pointing capabilities for CubeSats. For chemical thrusters, we are developing novel micro-monopropellant thrusters with several hundred mN as well as a 1-3 N bi-propellant micro rocket engine using green propellants and high specific impulse performance. This paper will give an overview of our micropropulsion developments highlighting performance as well as possible applications.
      102
  • Publication
    Optimization of a container design for depositing uniform metal coatings on glass microspheres by magnetron sputtering
    (Elsevier, 2010-08-24)
    Schmid, G. 
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    Eisenmenger-Sittner, C. 
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    Hell, J. 
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    Horkel, M. 
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    ;
    Mahr, H. 
    Coating granular substrates by PVD methods like magnetron sputtering is a very challenging process. Although many of such substrates may also be coated by other means like the sol gel method, there are coating materials (e. g. refractory metals) for which PVD processes are the method of choice. One of these substrates is hollow glass microspheres with 2–80 μm diameter which can be used for hydrogen storage if a proper catalytic film is applied. To achieve a uniform film by magnetron sputtering on all the spheres a special apparatus was used which basically consists of rotating vessels positioned beneath the target. The arising problems of agglutination of the powdery substrate were solved by designing a special coating vessel, where the spheres are contained during deposition. For testing the system first copper was used as a target material, which was then replaced by platinum since the glass microspheres are used for a catalytic application. The film thickness on the spheres was determined by optical absorption and matches well with the thickness calculated for the special vessel geometry. Additionally it is shown that the glass microspheres can be coated with a uniform layer by magnetron sputtering whereas coatings produced by a chemical deposition process are not continuous.
      70Scopus© Citations 17
  • Publication
    Innovative Hydrogen Storage in Microspheres
    (2008-02-20) ;
    Tajmar, Martin 
      107
  • Patent
      185  235
  • Publication
    Development of a µ-scale Turbine Expander for Energy Recovery
    (American society of mechanical engineers, 2009) ;
    Dudzinski, Piotr 
    ;
    Tajmar, Martin 
    ;
    Willinger, Reinhard 
    ;
    Käfer, Klaus 
    Waste heat is a primary source of energy loss in many applications. A number of developments around a micro rocket engine at the Austrian Research Centers (ARC) promise innovative energy recovery and micro power generation solutions. Here we focus on the investigation of micro technologies for application in HVAC (heating, ventilating, and air conditioning) systems. The use of μ-scale turbine expanders for work recovery in transcritical CO2 heat pump processes has been identified as most interesting and promising for the application in HVAC cases. One of the main drawbacks of transcritical CO2 heat pumps is the lower COP (coefficient of performance) compared to conventional heat pump systems which originates from the non isothermal heat rejection in the gas cooler. This drawback can be compensated by utilizing the pressure difference between the high pressure and low pressure part of the heat pump for work recovery. This is feasible as the pressure difference is considerably larger in case of CO2 heat pumps compared to conventional systems. Work recovery can be realized by substituting the expansion valve between the high and low pressure side by an expansion machine. Due to the low flow rate of the working fluid, the turbine type is based on the Pelton turbine with specific two phase flow turbine blades. In addition to the turbine part a magnetic coupling, miniature bearings and a small scale generator are important parts of the system. Thermodynamic simulations showed an absolute microturbine power yield between 60 W and 150 W for a 2 kW heating system.
      109