Rovas

Dimitrios Rovas
Title: Mr.
Country of residence: Greece
Institution: Aristotle University of Thessaloniki
Address: 53-55 AGIAS MARINIS ST., ANO TOUMPA, THESSALONIKI, 54351, GREECE
Telephone: +30 6974879714, +30 2310995968
Date of birth: 26/12/1978
Early Stage Researcher: Yes
Sex: Male
MC Member: No
WG membership:
2

Dimitrios Rovas received his diploma in Mechanical Engineering in 2003 from the Aristotle University of Thessaloniki and since 2005 he is working as a research associate, with Prf. Christopher Koroneos, at the Laboratory of Heat Transfer and Environmental Engineering. He works in the areas of renewable energy sources, environmental management, life cycle assessment and exergy analysis. Currently he is investigating the exergy optimization of an energy autonomous residence that utilizes multiple RES. His future work will be oriented on the potential implementation of small Organic Power Cycles in Urban and Metropolitan Areas, that will utilize Solar energy or low enthalpy energy sources (Waste heat, Geothermal).

Publications
  • Koroneos Christopher and Rovas Dimitrios, (2012) “A review on Exergy Comparison of Hydrogen Production Methods from Renewable Energy Sources”, Energy Environ. Sci., 2012, 5 (5), 6640 - 6651. Hydrogen is an important energy carrier which could play a very significant role in the reduction of emissions of greenhouse gases. The route by which hydrogen is produced is the determining factor for its environmental performance. Hydrogen can be produced through methane reforming or through the electrolysis of water with the use of electricity or it can be produced directly by gasification from biomass. Renewable energy sources (RES) could be the feedstock for the two methods previously mentioned. The objective of this work is the comparison of hydrogen (H2) production processes using various renewable energy sources. This comparison is based on the exergy efficiency of each process. The renewable energy sources that have been used are: wind power, solar energy, hydroelectric power, and biomass. The solar energy systems that are used are photovoltaic and thermal. The biomass systems are divided into two categories: (a) electricity production through biomass combustion, (b) biomass gasification for the direct production of hydrogen. When in any of the processes electricity is produced, this electricity is used for the electrolysis process of water to produce hydrogen (and oxygen). Because hydrogen is transported in a liquid form, the liquefaction process is also taken into consideration in this work. The liquefaction process is very energy intensive and as a consequence it requires a lot of exergy. It has been found that the hydrogen production process with the highest exergy efficiency is the electrolysis using electricity from hydro power. This efficiency is 5.6%. The process with the lowest exergy efficiency is the one with electrolysis driven by electricity from solar energy photovoltaics. The efficiency of this process is 1.0%.
  • Christopher J. Koroneos, Dimitrios C. Rovas, (2010) “Carbon Sequestration. A Comparative Analysis”, Global Warming, Green Energy and Technology, Engineering Solutions, pp. 281-294. Springer, ISBN: 978-1-4419-1016-5. Carbon sequestration refers to the provision and safe storage of carbon dioxide that otherwise would be emitted to the atmosphere. The basic idea is the retention, isolation, and final storage of the produced carbon dioxide, utilizing biological, chemical, or mechanical routes. Some methods retain the carbon from the exhaust gas before it is emitted. The retained carbon then can be deposited in underground geological repositories or in the oceans. Additionally, chemical and biological processes can transform carbon into solid products or they can enhance the natural terrestrial cycle. Carbon sequestration can be a useful tool in the minimization of the carbon emissions from fossil fuel combustion and it can be significant in the stabilization of the atmospheric CO2 concentration.
  • Polyzakis, A.L.; Koroneos, C.J.; Malkogianni, A.K.; Rovas, D.C.; Karmalis, J. (2008): “Utilization of Geothermal Energy for District Heating and Cooling”, Computing and Computational Techniques in Sciences. Selected Papers from the WSEAS Conferences in Spain, Santander, Cantabria, Spain, September 23-25, WSEAS Press, ISBN 978-960-474-009-3. Renewable energy sources are becoming more and more attractive solutions for clean and sustainable energy needs. The innovation and diffusion of renewable energy technologies can play a major role in the mitigation of climate change. Geothermal energy utilization has a great variety, from residential heating to electricity production, and it is so vast that could supply all the energy needed by humanity. Additionally the geothermal energy in regions close to volcanoes is close to the surface and easy to use economically. Thus, the exploitation of the geothermal hot water sources can eliminate the energy use from hydrocarbons and minimize the environmental impact. The objective of this work is to investigate the potential of the utilization of the existing geothermal potential of Nisyros Island located in the south-east Aegean Sea. Geothermal energy will be exploited in a district heating and cooling system, in a way that all the cooling and heating load of the island, throughout the year, would be covered with no additional use of fossil fuels. The technology for the exploitation of geothermal energy, in cooling mode, is the Single Effect Absorption Chiller. Additionally, the environmental performance of this projected will be presented in terms of CO2 minimization, due to the avoidance of the fossil fuel consumption. This work is to determine and demonstrate the feasibility of a heating and cooling district system protecting the fragile island environment.
  • Christopher Koroneos, Foteini Anastasiou, Rovas Dimitrios, (2008), “A comparative Life Cycle Assessment of Liquid Biofuels Production”, Computing and Computational Techniques in Sciences. Selected Papers from the WSEAS, Conferences in Spain, Santander, Cantabria, Spain, September 23-25, WSEAS Press, ISBN 978-960-474-009-3. Nowadays, the majority of the fuel use in transport comes from fossil fuels. Although there was an import of natural gas in public transportation, the gasoline and diesel oil remain the dominant vehicles’ driving force. In the European Union it is estimated that almost 21% of the greenhouse gases are produced from the transportation. The oil price continuous increase adds economics constrains besides the environmental problems. The objective of this work is the environmental comparison of the biofuels production routing from four different biomass forms, utilizing the life cycle assessment analysis. The impact category to be investigated is the greenhouse effect while the biomass forms used in the biofuels production is the rapeseed, the sunflower, the wheat and the sugar beet. The life cycle stages under study start at the cultivation and end at the combustion of the produced biofuels in vehicles. Although biofuels require a lot of primary energy from fossil fuels, the sum of produced emissions of equivalent CO2 from them is much smaller.
  • Koroneos, C. and Rovas, D. (2007) “A solar thermal power system in the city of Thessalonica with the use of the Pinch method for entropy minimisation”, Int. J. Exergy,Vol. 4, No. 2, pp.134–150. The objective of this paper is to create a small power plant, (producing 2 MW annually), which will be using solar energy as a driving fuel. The system is made up of three sub-systems: a set of Solar Collectors (SCS), a Rankine power cycle and a Heat Exchanger Network (HEN). Two cases with variations in the operation of the solar collectors and the heat exchanger network will be examined. The Pinch analysis methodology is used in their design. This will lead to minimum and hence a minimum entropy production. The exergy gains from the low entropy production techniques will be calculated.
  • C.J. Koroneos, A.J. Argyropoulos, D.C. Rovas (2006), “Measures to reduce emissions in the city of Athens”, presented in Towards In the City of Tomorrow on June 8-9 2006, Diplomatic Academy Vienna, Austria, published in Towards In the City of Tomorrow Conference Proceedings, Annex: Posters Accepted for Publication. Three Case Studies have been elaborated about the reduction of carbon emissions in Athens. Two of them concern public works that were constructed before the Olympics. One is the solar village, an experimental project with target to show how different energy sources can cooperate in order to produce electricity causing fewer emissions in a real living environment. The other one is Athens Metro (Attiko) which is one of the greatest public works ever in Greece. Its purpose is not only to promote sustainable transportation, but also to decrease emissions. Finally there is a study about the replacement of diesel buses with buses that use Compressed Natural Gas (CNG) as fuel. Two scenarios will be investigated. The first scenario involves the replacement of half the buses and the second is the replacement of the whole fleet of buses that use diesel as fuel with buses and the second is the replacement of the whole fleet of buses that use diesel as fuel with buses that use CNG.
  • Christopher Koroneos, Rovas Dimitrios, “Exergy Analysis of Geothermal Electricity Using the Kalina Cycle”, International Journal of Exergy. The geothermal energy that is stored in the earth is so vast that could supply all the energy needed by humanity. The difficulty in tapping this energy lies in its diffusivity. The geothermal energy in regions near volcanoes is close to the surface and easy to use economically. In this paper a vapor dominated system will be examined. The electricity that is produced from such a system is economically and environmentally in a better position than the electricity produced from coal or diesel. The Kalina cycle will be used in this system and an exergy analysis is performed. The Kalina cycle is a new concept in power generation and uses a mixture of 70% ammonia and 30% water as the working fluid with the potential to increase the exergy efficiency over the Rankine cycle. The exergy analysis will provide a qualitative and quantitative picture of the process.