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Bobinaite V.,Lithuanian Energy Institute | Bobinaite V.,Institute of Physical Energetics of Latvia
Renewable and Sustainable Energy Reviews | Year: 2015

Abstract The Baltic States realize the necessity to develop wind electricity sectors. This comes from the Baltic States concern of energy security, competitiveness and sustainable development of energy sectors. The paper deals with the financial aspects of sustainability of wind electricity sector. Namely, it aims at performing a comparative analysis of financial sustainability of companies producing electricity from wind resources in the Baltic States during 2009-2013. The financial statement analysis method is employed and the financial ratio technique is used. Altman, Liss and Tafler bankruptcy forecasting models are used to show both "health" and viability of the companies. 4 groups of financial ratios are computed: financial leverage, profitability, liquidity and assets utilization. Support schemes are recognized as a relevant factor influencing on the financial sustainability. The results of the analysis revealed that financial sustainability of the companies is moderate in the Baltic States. Lithuania and Estonia use high share of debt (80-85%) to finance economic activity, whereas Latvian companies use relatively high share of equity capital (35-40%). This shows that credit risk is available in the companies. Liquidity of the companies decreases. Operational efficiency is higher in Estonia and Lithuania than in Latvia, when profitability indicators are analyzed. During the latter several years efficiencies of assets utilization were similar in the Baltic States. The efficiency of current assets utilization is higher compared to efficiency of non-current assets utilization. Companies in Latvia demonstrate middle but increasing and in Estonia - high but reducing bankruptcy probabilities. Lithuanian case reveals that bankruptcy probability varies from high to low depending on the financial ratios analyzed, however, bankruptcy probability reduces. Companies should make liquidity, solvency, efficient use of assets and profitability management as a part of their corporate management policy framework. © 2015 Elsevier Ltd. All rights reserved.

Priedite I.,Institute of Physical Energetics of Latvia
Engineering for Rural Development | Year: 2014

The paper illustrates economical assessment of the grid-connected onshore micro wind turbines. The calculation is based on onshore wind speed hourly minimum value of 4 m height in Latvia approximated according to each wind turbine tower height. The result shows that increase in annual expenditure on electricity produced by onshore micro wind turbines is more than 264 %.

Purvins A.,European Commission | Papaioannou I.T.,European Commission | Oleinikova I.,Institute of Physical Energetics of Latvia | Tzimas E.,European Commission
Energy | Year: 2012

The present article analyses the effects caused by variable power. The analysis concerns a country-scale electricity system with a relatively high penetration of seasonally variable hydro power plants and wind farms in the total electricity generation in 2030. For this purpose, the Latvian electricity system was chosen as an appropriate case study, as around half of its electricity is already generated from hydro power and numerous wind farm installations are planned for 2030. Results indicate that in such systems high renewable power variations occur between seasons causing a high probability of power deficit in the winter and power surplus in the spring. Based on the results, the wind farms' influence on the power deficit and surplus occurrences are discussed in detail. Wind farm generation decreases the probability of the electricity system being in power deficit, but increases the probability of the system being in power surplus. In the latter situation, the maximum value of power surplus increases since it is enhanced by the wind farm generation. Probability equations to express these changes are provided. © 2012 Elsevier Ltd.

Arina D.,Latvia University of Agriculture | Orupe A.,Institute of Physical Energetics of Latvia
Environmental and Climate Technologies | Year: 2012

The article presents the results of experimental work in the first waste mechanical Pre-treatment Centre in Latvia Daibe. The goal - to detect the main parameters for sorted waste parts and to compare them with parameters stated for refuse derived fuel (RDF) in a cement plant in Latvia (Cemex). Samples were taken in four fractions-coarse, medium, fine, metal. The parameters - upper, lower heating values, moisture, ash content, S, Cl, metals were determined. Results-coarse fraction has greater potential of the production of the RDF, but reduction of its content of Cl would be necessary.

Kroics K.,Institute of Physical Energetics of Latvia
Vide. Tehnologija. Resursi - Environment, Technology, Resources | Year: 2013

This paper represents a design and implementation of a digital control of variable frequency interleaved DC-DC converter using a digital signal processor (DSP). The digital PWM generation, current and voltage sensing, user interface and the new period and pulse width value calculation with DSP STM32F407VGT6 are considered. Typically, the multiphase interleaved DC-DC converters require a current control loop in each phase to avoid imbalanced current between phases. This increases system costs and control complexity. In this paper the converter which operates in discontinuous conduction mode is designed in order to reduce costs and remove the current control loop in each phase. High current ripples associated with this mode operation are then alleviated by interleaving. Pulse width modulation (PWM) is one of the most conventional modulation techniques for switching DC-DC converters. It compares the error signal with the sawtooth wave to generate the control pulse. This paper shows how six PWM signals phase-shifted by 60 degrees can be generated from calculated values. To ensure that the measured values do not contain disturbances and in order to improve the system stability the digital signal is filtered. The analog to digital converter's (ADC) sampling time must not coincide with the power transistor's switching time, therefore the sampling time must be calculated correctly as well. Digital control of the DC-DC converter makes it easy and quickly to configure. It is possible for this device to communicate with other devices in a simple way, to realize data input by using buttons and keyboard, and to display information on LED, LCD displays, etc. © Rēzeknes Augustskola.

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