Lelde Timma

System Dynamic Model for the Accumulation of Renewable Electricity using Power-to-Gas and Power-to-Liquid Concepts

Abstract When the renewable energy is used, the challenge is match the supply of intermittent energy with the demand for energy therefore the energy storage solutions should be used. This paper is dedicated to hydrogen accumulation from wind sources. The case study investigates the conceptual system that uses intermitted renewable energy resources to produce hydrogen (power-to-gas concept) and fuel (power-to-liquid concept). For this specific case study hydrogen is produced from surplus electricity generated by wind power plant trough electrolysis process and fuel is obtained by upgrading biogas to biomethane using hydrogen. System dynamic model is created for this conceptual system. The developed system dynamics model has been used to simulate 2 different scenarios. The results show that in both scenarios the point at which the all electricity needs of Latvia are covered is obtained. Moreover, the methodology of system dynamics used in this paper is white-box model that allows to apply the developed model to other case studies and/or to modify model based on the newest data. The developed model can be used for both scientific research and policy makers to better understand the dynamic relation within the system and the response of system to changes in both internal and external factors.

Methodologies Used for Scaling-up from a Single Energy Production Unit to State Energy Sector

Abstract In a well-functioning and sustainable national energy sector, each of its elements should function with maximum efficiency. To ensure maximum efficiency and study possible improvement of the sector, a scaling-up framework is presented in this work. The scaling-up framework means that the starting point is a CHP unit and its operation, the next step of aggregation is in a district heating network, followed by a municipal energy plan and finally leading to a low carbon strategy. In this framework the authors argue, that the successful, innovative practices developed and tested at the lower level of aggregation can be then transferred to the upper levels of aggregation, thus leading to a scaling-up effect of innovative practices. The work summarizes 12 methodologies used in the energy sector, by dividing these methodologies among the levels of aggregation in a scaling-up framework.

Full Factorial Design of Screening Experiments for Biosurfactant Enhanced Remediation of Hydrophobic Substances in Soil

This paper evaluates the cleaning efficiency of glycolipid-based anionic biosurfactant produced by a local company. Before practical application in removal of oil or other hydrophobic substances from soil, it is necessary to learn the behavior of the biosurfactant across different systems. As process variables, temperature of environment, contact time with dilution of biosurfactant, and concentration of biosurfactant in washing solution were modeled by applying full factorial design. As response variable, cleaning efficiency was obtained experimentally by a set of laboratory tests. Screening design is employed for evaluation of interactions between response variable and process variables. The cleaning efficiency showed various results depending on the initial values of variables. At the upper limit of variables (+ 35 oC temperature of environment, 15 minutes contact time with dilution of biosurfactant, and 0.3 wt% concentration of biosurfactant in washing solution) the cleaning efficiency was 99.32 %. The results showed that all variables had significant effects on the cleaning efficiency at 95 % confidence level.

The quality of pellets available on the market in Latvia: classification according en 14961 requirements

Abstract The objectives of the paper are to determine the quality of pellets available on the market in Latvia and to compare results with the European standard EN 14961-2:2011. The following parameters have been determined for samples of pellets: length, diameter, moisture and ash content, mechanical durability, lower calorific value and bulk density. The results showed that all samples confirm to the B class requirements of the standard. If one considers the A1 class - only 4 out of 9 samples fit the requirements. The paper emphasizes the need for the introduction of a quality control system for the wood pellets market in Latvia.

Thermal Performance Analysis of Solar Collectors Installed for Combisystem in the Apartment Building

Thermal Performance Analysis of Solar Collectors Installed for Combisystem in the Apartment Building The paper focuses on the application of wood pellet and solar combisystem for space heating and hot water preparation at apartment buildings under the climate of Northern Europe. A pilot project has been implemented in the city of Sigulda (N 57° 09.410 E 024° 52.194), Latvia. The system was designed and optimised using TRNSYS - a dynamic simulation tool. The pilot project was continuously monitored. To the analysis the heat transfer fluid flow rate and the influence of the inlet temperature on the performance of solar collectors were subjected. The thermal performance of a solar collector loop was studied using a direct method. A multiple regression analysis was carried out using STATGRAPHICS Centurion 16.1.15 with the aim to identify the operational and weather parameters of the system which cause the strongest influence on the collectors performance. The parameters to be used for the systems optimisation have been evaluated. Daudzdzīvokļu Ēkai Uzstādītās Kombinētas Sistēmas Saules Kolektoru Veiktspējas Analīze Rakstā aplūkota saules un granulu kombinētā sistēma, kas Ziemeļeiropas klimatiskajos apstākļos nosedz daudzdzīvokļu ēkas apkures un karstā ūdens slodzes. Pilotprojekts tika īstenots Siguldā (N 57° 09.410 E 024° 52.194), Latvijā. Sistēma izveidota un optimizēta, izmantojot datorsimulācijas programmu TRNSYS. Rakstā īstenota sistēmas darbības analīze pēc iekārtu uzstādīšanas, organizējot nepārtrauktu monitoringu. Analizēta siltumnesēja plūsmas un temperatūras līmeņu ietekme uz saules kolektoru veiktspējas rādītājiem. Regresijas analīze veikta STATGRAPHICS Centurion 16.1.15 vidē, lai noteiktu, kuri no darbības un klimatiskajiem apstākļiem visvairāk ietekmē saules kolektoru efektivitāti. Izvērtēti nepieciešamie sistēmas optimizācijas parametri. Iegūts empīriskais modelis saules kolektoru efektivitātes noteikšanai.

A methodology for forecasting hazardous waste flows

In previous years, great attention has been paid to the problem of hazardous waste management. “Prevention costs” of the activities concerned with hazardous waste (HW) are lower than “restoration costs” after damage is done. Within the scope of the paper the methodology for forecasting hazardous waste flows was elaborated. The methodology of the research included 6 modules: historical data, assumptions, choose of indicators, data processing, and data analysis with STATGRAPHICS, and forecast models. The proposed methodology was validated for the case for Latvia. A new type of the indicator based on the HW intensity within the Statistical Classification of Economic Activities in the European Community (NACE Rev. 2) sectors and households has been developed. The indicator allows for assessing the HW production intensity. The results of the study suggest that HW intensity in Latvia is forecasted to slowly decrease by 3.8% in next six years. The pessimistic prognosis (upper 95%) gives an increase in HW intensity by 44.5%, but the intermediate (upper and lower 50%) gives a corridor of +18.4% to –36.1%.