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2017

Selle valdkonna püsiv URIhttp://hdl.handle.net/10492/5357

Sirvi

Sirvi 2017 Autor "Annuk, Andres" järgi

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  • Pisipilt
    Kirje
    Contribution of pumped hydro energy storage for more RES utilization on autonomous power systems
    (2017) Katsiagiannis, Y.; Annuk, Andres; Karapidakis, E.S.; Estonian University of Life Sciences. Institute of Technology. Department of Energy Engineering
    This paper addresses the performance issues of autonomous power systems under high renewable energy sources (RES) penetration. Renewable energy sources could be the main option for isolated power generation at remote locations in case that energy storage introduced. At the moment, pumped hydro storage (PHS) units and batteries storage systems (BSS) represent the most mature technologies for large scale energy storage. The basic criteria for this kind of energy storage unit installations include, (a) the existence of an autonomous power system with local power stations, (b) the high electricity production cost, (c) the potential of renewable energy sources (mainly wind and solar), and (d) the non-flat terrain morphology (for PHS). Greek islands represent ideal cases for large scale energy storage installations, as they fulfil all the above criteria. This paper shows the effect of the installation of a planned PHS unit in Crete island. The calculations are based on real data provided by the Cretan power system operator, whereas the results show the effect of energy storage units operation on the energy mix, as well as the economic viability of the project, which is combined with significant environmental benefits.
  • Pisipilt
    Kirje
    Reed canary grass cultivation’s energy efficiency and fuel quality
    (2017) Annuk, Andres; Allik, Alo; Annuk, Karl; Estonian University of Life Sciences. Institute of Technology. Department of Energy Engineering; Estonian University of Life Sciences. Institute of Agricultural and Environmental Sciences
    The article discusses the energy yield and yield capacity of reed canary grass stands in semi-natural and cultivated meadows with edaphic conditions most favourable for species growing on fertile soil. Energy grass production yields have been assessed with respect to the issues of precipitation, sunshine, and frozen ground. In Estonia, a dried matter level of 4.2– 8.5 t ha-1 of reed canary grass may produce 72.91–147.56 GJ ha-1 gross energy by using 1.48– 3.06 GJ ha-1 input energy, which consequently nets 71.44–1,445.00 GJ ha-1 . The above finding indicates that 1 MJ input energy enables the production of 2.8 kg dry matter. The efficiency of energy production (ratio of energy returned on energy invested) depends on the amount of input energy used to grow and harvest reed canary grass. The input energy payback ratio for the given case was 48.2–49.4, which was higher than cases with lower and higher dry matter yield levels. Precipitation during the second part of the Estonian summer, heavy winter snow cover and a simultaneous frequent lack of frozen ground reduce the productivity of reed canary grass as energy hay because the winter or early spring harvest cannot be used.