@article{AlexopoulosBreitbachHoffschmidtetal.2008, author = {Alexopoulos, Spiros and Breitbach, Gerd and Hoffschmidt, Bernhard and Stobbe, P.}, title = {Computational fluid flow of porous resic ceramic filtering modules and optimization of the channel edge form geometry}, series = {Proceedings : April 14 - 18, 2008, Leipzig, Germany / hosted by VDI, Society for Chemical and Process Engineering . Vol 2}, journal = {Proceedings : April 14 - 18, 2008, Leipzig, Germany / hosted by VDI, Society for Chemical and Process Engineering . Vol 2}, publisher = {Filtech Exhibitions}, address = {Meerbusch}, pages = {300 -- 304}, year = {2008}, language = {en} } @article{AlexopoulosBreitbachHoffschmidtetal.2008, author = {Alexopoulos, Spiros and Breitbach, Gerd and Hoffschmidt, Bernhard and Stobbe, P.}, title = {Optimization of the geometry of porous SiC ceramic filtering modules using numerical methods}, series = {Developments in porous, biological and geopolymer ceramics : a collection of papers presented at the 31st International Conference on Advanced Ceramics and Composites, January 21 - 26, 2007, Daytona Beach, Florida ; [papers presented at the Symposium on Porous Ceramics: Novel Developments and Applications] / ed.: Manuel Brito ... Vol. ed.: Jonathan Salem ... The American Ceramics Society}, journal = {Developments in porous, biological and geopolymer ceramics : a collection of papers presented at the 31st International Conference on Advanced Ceramics and Composites, January 21 - 26, 2007, Daytona Beach, Florida ; [papers presented at the Symposium on Porous Ceramics: Novel Developments and Applications] / ed.: Manuel Brito ... Vol. ed.: Jonathan Salem ... The American Ceramics Society}, publisher = {Wiley}, address = {Hoboken, NJ}, isbn = {9780470196403}, pages = {95 -- 104}, year = {2008}, language = {en} } @article{AlexopoulosHoffschmidt2010, author = {Alexopoulos, Spiros and Hoffschmidt, Bernhard}, title = {Solar tower power plant in Germany and future perspectives of the development of the technology in Greece and Cyprus}, series = {Renewable Energy . 35 (2010), H. 7}, journal = {Renewable Energy . 35 (2010), H. 7}, isbn = {0960-1481}, pages = {1352 -- 1356}, year = {2010}, language = {en} } @article{AlexopoulosHoffschmidt2010, author = {Alexopoulos, Spiros and Hoffschmidt, Bernhard}, title = {Solarthermische Kraftwerke mit thermischen Speichern}, series = {Chemie Ingenieur Technik. 82 (2010), H. 9}, journal = {Chemie Ingenieur Technik. 82 (2010), H. 9}, isbn = {1522-2640}, pages = {1606 -- 1606}, year = {2010}, language = {de} } @article{GoettscheHoffschmidtAlexopoulosetal.2008, author = {G{\"o}ttsche, Joachim and Hoffschmidt, Bernhard and Alexopoulos, Spiros and Funke, J. and Schwarzb{\"o}zl, P.}, title = {First Simulation Results for the Hybridization of Small Solar Power Tower Plants}, series = {EuroSun 2008 : 1st International Conference on Solar Heating, Cooling and Buildings, 2008-10-07 - 2008-10-10, Lissabon (Portugal). Vol. 1}, journal = {EuroSun 2008 : 1st International Conference on Solar Heating, Cooling and Buildings, 2008-10-07 - 2008-10-10, Lissabon (Portugal). Vol. 1}, publisher = {Sociedade Portuguesa De Energia Solar (SPES)}, address = {Lisbon}, isbn = {978-1-61782-228-5}, pages = {1299 -- 1306}, year = {2008}, language = {en} } @article{Alexopoulos2012, author = {Alexopoulos, Spiros}, title = {Biogas systems: basics, biogas multifunction, principle of fermentation and hybrid application with a solar tower for the treatment of waste animal manure}, series = {Journal of Engineering Science and Technology Review}, volume = {5}, journal = {Journal of Engineering Science and Technology Review}, number = {4}, issn = {1791-2377}, pages = {48 -- 55}, year = {2012}, abstract = {Two of the main environmental problems of today's society are the continuously increasing production of organic wastes as well as the increase of carbon dioxide in the atmosphere and the related green house effect. A way to solve these problems is the production of biogas. Biogas is a combustible gas consisting of methane, carbon dioxide and small amounts of other gases and trace elements. Production of biogas through anaerobic digestion of animal manure and slurries as well as of a wide range of digestible organic wastes and agricultural residues, converts these substrates into electricity and heat and offers a natural fertiliser for agriculture. The microbiological process of decomposition of organic matter, in the absence of oxygen takes place in reactors, called digesters. Biogas can be used as a fuel in a gas turbine or burner and can be used in a hybrid solar tower system offering a solution for waste treatment of agricultural and animal residues. A solar tower system consists of a heliostat field, which concentrates direct solar irradiation on an open volumetric central receiver. The receiver heats up ambient air to temperatures of around 700°C. The hot air's heat energy is transferred to a steam Rankine cycle in a heat recovery steam generator (HRSG). The steam drives a steam turbine, which in turn drives a generator for producing electricity. In order to increase the operational hours of a solar tower power plant, a heat storage system and/ or hybridization may be considered. The advantage of solar-fossil hybrid power plants, compared to solar-only systems, lies in low additional investment costs due to an adaptable solar share and reduced technical and economical risks. On sunny days the hybrid system operates in a solar-only mode with the central receiver and on cloudy days and at night with the gas turbine only. As an alternative to methane gas, environmentally neutral biogas can be used for operating the gas turbine. Hence, the hybrid system is operated to 100\% from renewable energy sources}, language = {en} } @article{KluczkaEcksteinAlexopoulosetal.2014, author = {Kluczka, Sven and Eckstein, Julian and Alexopoulos, Spiros and Vaeßen, Christiane and Roeb, Martin}, title = {Process simulation for solar steam and dry reforming}, series = {Energy procedia : Proceedings of the SolarPACES 2013 International Conference}, volume = {49}, journal = {Energy procedia : Proceedings of the SolarPACES 2013 International Conference}, publisher = {Elsevier}, address = {Amsterdam}, issn = {1876-6102 (E-Journal)}, doi = {10.1016/j.egypro.2014.03.092}, pages = {850 -- 859}, year = {2014}, abstract = {In co-operation with the German Aerospace Center, the Solar-Institut J{\"u}lich has been analyzing the different technologies that are available for methanol production from CO2 using solar energy. The aim of the project is to extract CO2 from industrial exhaust gases or directly from the atmosphere to recycle it by use of solar energy. Part of the study was the modeling and simulating of a methane reformer for the production of synthesis gas, which can be operated by solar or hybrid heat sources. The reformer has been simplified in such a way that the model is accurate and enables fast calculations. The developed pseudo-homogeneous one- dimensional model can be regarded as a kind of counter-current heat exchanger and is able to incorporate a steam reforming reaction as well as a dry reforming reaction.}, language = {en} } @article{Alexopoulos2015, author = {Alexopoulos, Spiros}, title = {Simulation model for the transient process behaviour of solar aluminium recycling in a rotary kiln}, series = {Applied Thermal Engineering}, volume = {78}, journal = {Applied Thermal Engineering}, publisher = {Elsevier}, address = {Amsterdam}, issn = {1359-4311}, doi = {10.1016/j.applthermaleng.2015.01.007}, pages = {387 -- 396}, year = {2015}, language = {en} } @article{AlexopoulosHoffschmidt2017, author = {Alexopoulos, Spiros and Hoffschmidt, Bernhard}, title = {Advances in solar tower technology}, series = {Wiley interdisciplinary reviews : Energy and Environment : WIREs}, volume = {6}, journal = {Wiley interdisciplinary reviews : Energy and Environment : WIREs}, number = {1}, publisher = {Wiley}, address = {Weinheim}, issn = {2041-840X}, doi = {10.1002/wene.217}, pages = {1 -- 19}, year = {2017}, language = {en} } @article{GoettscheAlexopoulosDuemmleretal.2019, author = {G{\"o}ttsche, Joachim and Alexopoulos, Spiros and D{\"u}mmler, Andreas and Maddineni, S. K.}, title = {Multi-Mirror Array Calculations With Optical Error}, pages = {1 -- 6}, year = {2019}, abstract = {The optical performance of a 2-axis solar concentrator was simulated with the COMSOL Multiphysics® software. The concentrator consists of a mirror array, which was created using the application builder. The mirror facets are preconfigured to form a focal point. During tracking all mirrors are moved simultaneously in a coupled mode by 2 motors in two axes, in order to keep the system in focus with the moving sun. Optical errors on each reflecting surface were implemented in combination with the solar angular cone of ± 4.65 mrad. As a result, the intercept factor of solar radiation that is available to the receiver was calculated as a function of the transversal and longitudinal angles of incidence. In addition, the intensity distribution on the receiver plane was calculated as a function of the incidence angles.}, language = {en} }