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Gkatzikis L.,University of Thessaly | Koutsopoulos I.,Center for Research and Technology Hellas | Salonidis T.,IBM
IEEE Journal on Selected Areas in Communications | Year: 2013

The design of efficient Demand Response (DR) mechanisms for the residential sector entails significant challenges, due to the large number of home users and the negligible impact of each of them on the market. In this paper, we introduce a hierarchical market model for the smart grid where a set of competing aggregators act as intermediaries between the utility operator and the home users. The operator seeks to minimize the smart grid operational cost and offers rewards to aggregators toward this goal. Profit-maximizing aggregators compete to sell DR services to the operator and provide compensation to end-users in order to modify their preferable consumption pattern. Finally, end-users seek to optimize the tradeoff between earnings received from the aggregator and discomfort from having to modify their pattern. Based on this market model, we first address the benchmark scenario from the point of view of a cost-minimizing operator that has full information about user demands. Then, we consider a DR market, where all entities are self-interested and non-cooperative. The proposed market scheme captures the diverse objectives of the involved entities and, compared to flat pricing, guarantees significant benefits for each. Using realistic demand traces, we quantify the arising DR benefits. Interestingly, users that are extremely willing to modify their consumption pattern do not derive maximum benefit. © 1983-2012 IEEE. Source


Koutsopoulos I.,Center for Research and Technology Hellas
Proceedings - IEEE INFOCOM | Year: 2013

Participatory sensing has emerged as a novel paradigm for data collection and collective knowledge formation about a state or condition of interest, sometimes linked to a geographic area. In this paper, we address the problem of incentive mechanism design for data contributors for participatory sensing applications. The service provider receives service queries in an area from service requesters and initiates an auction for user participation. Upon request, each user reports its perceived cost per unit of amount of participation, which essentially maps to a requested amount of compensation for participation. The participation cost quantifies the dissatisfaction caused to user due to participation. This cost is considered to be private information for each device, as it strongly depends on various factors inherent to it, such as the energy cost for sensing, data processing and transmission to the closest point of wireless access, the residual battery level, the number of concurrent jobs at the device processor, the required bandwidth to transmit data and the related charges of the mobile network operator, or even the user discomfort due to manual effort to submit data. Hence, participants have strong motive to misreport their cost, i.e. declare a higher cost that the actual one, so as to obtain higher payment. We seek a mechanism for user participation level determination and payment allocation which is most viable for the provider, that is, it minimizes the total cost of compensating participants, while delivering a certain quality of experience to service requesters. We cast the problem in the context of optimal reverse auction design, and we show how the different quality of submitted information by participants can be tracked by the service provider and used in the participation level and payment selection procedures. We derive a mechanism that optimally solves the problem above, and at the same time it is individually rational (i.e., it motivates users to participate) and incentive-compatible (i.e. it motivates truthful cost reporting by participants). Finally, a representative participatory sensing case study involving parameter estimation is presented, which exemplifies the incentive mechanism above. © 2013 IEEE. Source


Xydis G.,Center for Research and Technology Hellas
Journal of Cleaner Production | Year: 2015

Abstract The wind potential in a mountainous area of northern Greece close to an intensively exploited agricultural area has been studied via an experimental study aiming at identifying the wind farm (WF) development potentials of the area based on wind energy penetration/integration criteria. The first priority of the independent power producer (IPP) is to sell the generated electricity into the grid. However, the energy needs of the agricultural area are to be met using the non absorbed wind power. The study is a qualitative approach and examines ways for the load shed of a wind farm to be used for agricultural purposes and meet the demand and at the same time "offer" to the grid a less fluctuating electricity production signal. Based on the integration and wind resource analyses results, the final wind farm optimized layout can be decided. © 2013 Elsevier Ltd. All rights reserved. Source


Iliopoulou E.F.,Center for Research and Technology Hellas
Current Organic Synthesis | Year: 2010

Biomass represents the type of renewable energy source that will play a substantial role in the future global energy balance, as it is the only renewable source with the potential to be converted to liquid, solid and gaseous fuels. Today lignocellulosic biomass appears to be the cheapest and most abundant biomass feedstock, yet no economically and technologically feasible process is developed for its conversion to fuels, at least competitive with the currently used petroleum fuels. Biomass pyrolysis is an emerging thermochemical conversion process that leads to the production of bio-oil. Bio-oil however, presents several undesired properties that do not permit its direct exploitation. On the other hand, sugars derived from lignocellulosic biomass make up the predominant class of compounds, also exhibiting undesired properties. In both cases presence of oxygen in biomass derived copounds seems the major problem. Recently the targeted pathways for the conversion of lignocellulose-derived carbohydrates to liquid transportation fuels involve the partial removal of oxygen, C-C bond formation of functional molecules, and removal of the remaining oxygen. The formation of C-C bonds between these oxygenated molecules can take place by aldol condensation, alkylation, or ketonization as will be described in the present review study. © 2010 Bentham Science Publishers Ltd. Source


Darzentas N.,Center for Research and Technology Hellas
Bioinformatics | Year: 2010

Summary: We present Circoletto, an online visualization tool based on Circos, which provides a fast, aesthetically pleasing and informative overview of sequence similarity search results. © The Author 2010. Published by Oxford University Press. All rights reserved. Source

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