Reed canary grass cultivation’s energy efficiency and fuel quality

ArticleThe 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

Contribution of pumped hydro energy storage for more RES utilization on autonomous power systems

ArticleThis 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

Retraction: Determination of efficiency in the design phase of the enterprise by the method of finite relations

Saabunud / Received 03.10.2019 ; Aktsepteeritud / Accepted 15.11.2019 ; Avaldatud veebis / Published online 29.11.2019 ; Vastutav autor / Corresponding author: Andres Annuk e-mail: [email protected] manuscript "DETERMINATION OF EFFICIENCY IN THE DESIGN PHASE OF THE ENTERPRISE BY THE METHOD OF FINITE RELATIONS" by Valerij Karpov, Artem Nemtsev, Toivo Kabanen and Andres Annuk was submitted to Agraarteadus on 3 November 2019, accepted on 15 November 2019 and published on In Press on 29 November 2019. In December 2021, we received expressions of concern from the Academic Ethics Commission of the Estonian University of Life Sciences about similarities with the article entitled "Determination of efficiency in the design phase of the enterprise by the method of finite relations" ("Opredelenie jenergeticheskoj jeffektivnosti na jetape proektirovanija predprijatija metodom konechnyh otnoshenij") [In Russian] https://cyberleninka.ru/article/n/opredelenieenergeticheskoy-effektivnosti-na-etape-proektirovaniya-predpriyatiyametodom-konechnyh-otnosheniy/pdf by Valerij Karpov and Artem Nemtsev submitted to Bulletin of MSTU, vol. 18, no. 4, 2015, pp. 709– 718 (Vestnik MGTU, tom 18, # 4, 2015 g. str. 709–718). The expert of the Academic Ethics Commission of the Estonian University of Life Sciences analysed articles for similarities. The analysis revealed that the two articles reported the same experiments and the same results. Small divergences existed in the list of authors, in the Introduction, and the References. These divergences, however, are minor and were explained by the corresponding author. The corresponding author admitted that he was not aware of a previously published article. As a result, the article in Agraarteadus, accepted at a later date, is considered a duplicate publication. On this basis, we have decided to retract the article

Energy efficiency of consumption – methods of analysis and evaluation

Saabunud / Received 16.10.2019 ; Aktsepteeritud / Accepted 15.11.2019 ; Avaldatud veebis / Published online 29.11.2019 ; Vastutav autor / Corresponding author: Annuk Andres e-mail: [email protected], economic, and social need to define and control the efficiency of energy usage – consumer energy efficiency implies the necessity to determine the exact contents of this new concept. A deeper analysis of a consumer energy system in order to support the consumer energy efficiency value appropriate for the contents should be carried out to find the factors that affect the value. This article shows that for the purposes of advanced energy consumption analysis, the consumer energy system becomes an integral part of the whole energy system (starting with the energy generation facility) which forms the demand for the produced energy and its usage efficiency. The consumer energy system is so important that in the course of developing and improving the electric supply and consumption systems, it questions the traditional priority of the first component (energy supply) and adaptive dependence of the second one. This article proves, inter alia, that manufacturers can raise their consumer energy efficiency by improving the production technology, using materials with new properties, modernizing the energy equipment, switching to automatic enterprise design systems and using other means commonly known as scientific and technical progress

Evaluation of the Accuracy of Different PV Estimation Models and the Effect of Dust Cleaning: Case Study a 103 MW PV Plant in Jordan

The estimation of PV production has been widely investigated previously, where many empirical models have been proposed to account for wind and soiling effects for specific locations. However, the performance of these models varies among the investigated sites. Hence, it is vital to assess and evaluate the performance of these models and benchmark them against the common PV estimation model that accounts only for the ambient temperature. Therefore, this study aims to evaluate the accuracy and performance of four empirical wind models considering the soiling effect, and compare them to the standard model for a 103 MW PV plant in Jordan. Moreover, the study investigates the effect of cleaning frequency on the annual energy production and the plant’s levelized cost of electricity (LCOE). The results indicate almost identical performance for the adopted models when comparing the actual energy production with R2 and RMSE (root mean square error) ranges of 0.93–0.98 and 0.93–1.56 MWh for both sub-plants, with a slight superiority of the models that incorporate wind effect. Finally, it is recommended in this study to clean the PV panels every two weeks instead of every three months, which would increase annual energy production by 4%, and decrease the LCOE by 5% of the two PV sub-plants

Possibilities for balancing wind generators’ output power

Wind is, compared to solar irradiation, a highly stochastic energy source; therefore forecasting wind generator output power is complicated. The aim of this study was how to better fit wind generators (their output power) into energy systems. We studied two options: cutting off wind parks output power chart peaks and combining wind generators with PV panels and batteries. The first way to reach to aim of this study was to analyse different wind park data for finding methods to correct forecast error of output power. Pakri and Aulepa wind parks were chosen. Pakri wind park is located in the best wind conditions in Estonia and Aulepa wind park is located in an average site in a coastal area. The second way to reach to aim of this study was increasing the proportion of renewable fraction, thereby reducing the need of obtaining electrical power from the grid, at different deviations of the unit consumer’s graph, but at the same time the average consumption of the year stays the same. The other important variable in the calculations is the battery size. The solar irradiation data was acquired from Estonian Meteorological and Hydrological Institute (EMHI) Tõravere database and wind data from Tiirikoja database

Wind Energy in Estonian Western Farmlands

Rosana G. Moreira, Editor-in-Chief; Texas A&M UniversityThis is a paper from International Commission of Agricultural Engineering (CIGR, Commission Internationale du Genie Rural) E-Journal Volume 7 (2005): Wind Energy in Estonian Western Farmlands by Teolan Tomson, Andres Annu

Modelling of Consumption Shares for Small Wind Energy Prosumers

This article describes a simulation of energy distribution in an average household where electricity is produced with a small wind generator or purchased from the public electricity grid. Numerical experiments conducted within an average of five minutes were performed using annual production and consumption graphs. Virtual storage devices, a water tank and a battery were used to buffer energy inside the household. The energy required for non-shiftable consumption and hot water consumption were taken directly from the utility grid. Surplus energy remaining from wind generator production after providing for consumption and storage needs were redirected there. A cover factor was used as a measure of the efficiency of energy distribution. One of the aims of the article was to determine by simulations the change of the cover factor in a virtually designed situation where the expected energy output of the wind generator was known in advance over one to three hours. The results found that for the configuration of the proposed nanogrid option, the positive results were readily achieved when the expected wind generator production was known an hour ahead. Then, the cover factor increased from 0.593 to 0.645. The side result of using projected/expected production is an increase in asymmetrical energy exchanges bilaterally between nanogrid and utility grid in favour of grid sales. Another finding was that the cover factor depended on the wind generator’s production intensity but less on the intensity of consumption within the household.It is hoped/expected that future research will address the prediction of output using mathematical methods

Determination of Low Power Boiler Efficiency and Harmful Emissions while Burning of Energy Plants

Analytical review and the results of experimental studies of plant biomass production and its usage as the environmentally-friendly local fuel is presented in this paper. The analytical review of experimental research results of energy plants preparation for burning and burning is given, evaluated and compared with the emissions of harmful substances into the air while burning these plants. There were presented and compared the experimental research results of determination the low power boiler efficiency and harmful emissions while burning of the energy plants, such as willows, black poplar and aspen hybrid, chopped by the drum choppers, and these plants burning was compared with ashen wood burning. The test is carried out in the laboratory low power boiler, which is designed to burn wood, wood briquettes and large chaff. After determination of harmful substances emissions into the environment it was concluded, that burning efficiency of energy plants was better and pollution concentration was lower when aspen hybrid and black poplar were used, bigger amount of pollutants were determined when willows was burned, and the biggest amount of pollutants was while burning of ashen woodVytauto Didžiojo universitetasŽemės ūkio akademij