Time filter

Source Type

Dortmund, Germany

Spitalny L.,TU Dortmund | Myrzik J.M.A.,TU Dortmund | Mehlhorn T.,RWE Effizienz GmbH
Applied Thermal Engineering | Year: 2014

In order to reduce the impact of the anthropogenic climate effect, the transition to a highly efficient and sustainable energy system is needed. In particular, the heating sector shows a large potential for efficiency measures. Besides increasing requirements for the thermal insulation of buildings, in order to reduce the residential thermal energy demand, more efficient technologies such as micro combined heat and power generation units as well as heat pumps become increasingly important in the German households sector. Accordingly, this is a very dynamic market with uncertainties about the diffusion of these technologies for residential applications. Furthermore, forecasts of the development just focus on historical market trends. In order to forecast the possible market diffusion of the considered technologies until the year 2020 a new approach is developed based on the status of the residential building sector in Germany. Thereby, the possible market diffusion is based on the amount of units that are economically viable for the users, the so called economic addressable market. The analysis shows that the new construction of single family houses has the highest addressable market for heat pumps. The improvement of existing heating systems by heat pumps is only cost efficient, if an existing oil-based heating system is replaced. The use of micro-CHP units has the highest potential in multifamily houses. This applies for existing buildings as well as for the case of new construction. Nevertheless, the results just can indicate a tendency, how the market will develop in future. © 2013 Elsevier Ltd. Source

Bergner A.,Ruhr University Bochum | Westermeier M.,Ruhr University Bochum | Westermeier M.,RWE Effizienz GmbH | Ruhrmann C.,Ruhr University Bochum | And 2 more authors.
Journal of Physics D: Applied Physics | Year: 2011

An atmospheric pressure argon arc is operated with dc currents of different amplitudes in a model lamp between electrodes made of pure and thoriated tungsten. Temperature measurements are performed at these electrodes with a CCD camera being calibrated at =890nm in absolute units of surface radiance and an interference filter for this wavelength. Temperature distributions are deduced from the CCD camera records of the electrodes assuming that they are grey body radiators. The records show a diffuse mode of attachment at the cathode. Doping the electrode with ThO 2 causes a reduction in the cathode temperature by an amount of the order of 1000K. On the other hand the anode temperature is weakly increased by a doping with ThO 2. A reduction in the work function of the cathode from 4.55 to 3eV is found by a comparison with cathode temperatures obtained by a numerical simulation of the diffuse mode of arc attachment with a well established cathode boundary layer model. Moreover, it is noted that the reduction is independent of the amount of ThO 2 by which the electrode material is doped indicating that the work function of thoriated cathodes is the result of a self adjustment to the work function minimum at a thorium coverage of 0.5. The weak influence of ThO 2 on the anode temperature shows that the average work function of the anode does not depend on the thorium content of the electrode. The results are explained by a thorium ion current, by which evaporated thorium is repatriated to the cathode surface. © 2011 IOP Publishing Ltd. Source

Ruhrmann C.,Ruhr University Bochum | Westermeier M.,Ruhr University Bochum | Westermeier M.,RWE Effizienz GmbH | Hobing T.,Ruhr University Bochum | And 5 more authors.
Journal of Physics D: Applied Physics | Year: 2013

Presently, most high intensity discharge (HID) lamps contain mercury to generate a high pressure buffer gas and thereby an appropriate power input into the arc. Due to its toxicity, the replacement of Hg is of particular interest in recent research on HID lamps. Up to now, the emission coefficient of an atomic Hg double line is widely used to determine the plasma temperature Tpl in HID lamps. Tpl is needed to calculate the total density of atoms and ions of elements inside these lamps. A combination of optical emission and broadband absorption spectroscopy allows us to evaluate Tpl independently of Hg emission lines. The method is required for a determination of Tpl if the Hg line intensity within the investigated lamp is too low, is superimposed by other lines or if environmental-friendly Hg-free lamps are developed. Within this work, phase-resolved plasma temperatures are determined in front of the electrode of Hg-containing MH lamps by emission spectroscopy at atomic Hg lines. Above all, temperatures are measured by a combination of emission and absorption spectroscopy at atomic rare earth lines, namely Dy and Tm. A comparison of Tpl determined by both methods agree within an error margin of <10%. Total phase-resolved rare earth atom densities are obtained by means of the measured ground state densities and Tpl. The combination of emission and absorption spectroscopy is also applied to the bulk plasma of lamps where the intensity of the Hg emission lines is too low for plasma temperature measurements or Hg is absent. It provides the partial rare earth pressure and by comparison with thermodynamic data cold spot temperatures within the lamps. © 2013 IOP Publishing Ltd. Source

Westermeier M.,Ruhr University Bochum | Westermeier M.,RWE Effizienz GmbH | Ruhrmann C.,Ruhr University Bochum | Bergner A.,Ruhr University Bochum | And 4 more authors.
Journal of Physics D: Applied Physics | Year: 2013

The lowering of the gas phase emitter effect of Dy in ceramic metal halide lamps by the admixture of TlI and NaI to the rare earth iodide salt DyI 3 is investigated at lamps with different additives. The arcs are operated in an Hg buffer gas atmosphere of 2 MPa between rod-shaped pure tungsten electrodes within transparent YAG lamp tubes with a switched-dc current at operating frequencies from 1 Hz to 1 kHz. The atomic ground state density of Dy is measured phase resolved half way between the electrodes and in front of an electrode by broad band absorption spectroscopy, the Dy ion density in front of an electrode by emission spectroscopy and the electrode tip temperature pyrometrically within lamps seeded with differently composed fillings. The measurements confirm that a strong reduction in the electrode tip temperature is correlated with a high Dy ion density in front of the electrode within the cathodic half period. The Dy ion density is depressed predominantly and with it the reduction in the electrode tip temperature by a competing ionization of Tl, and in addition by a lowering of the Dy vapour pressure above the pool of molten salt by TlI. The influence of Na is of minor importance. © 2013 IOP Publishing Ltd. Source

Reinelt J.,Ruhr University Bochum | Reinelt J.,RWE Effizienz GmbH | Westermeier M.,Ruhr University Bochum | Ruhrmann C.,Ruhr University Bochum | And 3 more authors.
Journal of Physics D: Applied Physics | Year: 2011

Phase-resolved temperature distributions are determined along a rod-shaped tungsten electrode, by which an ac arc is operated within a model lamp filled with argon. Switched dc and sinusoidal currents are applied with amplitudes of several amperes and operating frequencies being varied between 10 Hz and 10 kHz. The temperature is deduced from the grey body radiation of the electrode being recorded with a spectroscopic measuring system. Phase-resolved values of the electrode tip temperature Ttip and of the power input Pin are determined comparing the measured temperature distributions with the integral of the one-dimensional heat balance with these parameters as integration constants. They are supplemented by phase-resolved measurements of the sum of cathode and anode fall called the electrode sheath voltage. If a switched dc current is applied it is found that both quantities are within the cathodic phase only marginally higher than for a cathode being operated with a dc current. Ttip and Pin start to decrease for low currents and to increase for high currents at the beginning of the anodic phase. But with increasing operating frequency the deviations from the cathodic phase are reduced until they cannot be resolved for frequencies of several kHz. A more pronounced modulation, but the same tendencies, is observed with a sinusoidal current waveform. For 10 kHz a diffuse arc attachment with an almost phase-independent electrode tip temperature, which deviates only marginally from that of a dc cathode, and an electrode sheath voltage proportional to the arc current is established with both current waveforms. © 2011 IOP Publishing Ltd. Source

Discover hidden collaborations