Power engineering - energy supply

During coal mining some dangerous and explosive gases are released. Due to safety reasons the mines should be intensively ventilated. Much of the released gas at coal mining is methane. Released gases are vented to surroundings with ventilation air and therefore the methane is not profitable used. One of the potential beneficial utilization of methane in ventilation air is the utilization as a power station air intake. This paper analyzes the possibility of using the ventilation air from the Velenje Coal Mine as an air intake for power plant Šoštanj Unit 5. The analysis shows that this utilization would have a positive effect in environmental and energy aspect.

LACKO, R., DROBNIČ, B., MORI, M., SEKAVČNIK, M.
PLANNING OF A SELF-SUFFICIENT ENERGY SYSTEM WITH 100% RENEWABLE ENERGY SOURCES AND HYDROGEN STORAGE
KOMUNALNA ENERGETIKA / POWER ENGINERING, 17

abstract

A potential solution for stand-alone power generation is to use a hybrid energy systems with hydrogen energy storage. In this paper, a pre-feasibility study of using 100% renewable hybrid energy system (using solar and wind energy source) with hydrogen technologies (electroyser, hydrogen tank, fuel cell) for a reference household application in Portorož, Slovenia is explained. HOMER software tool is used for simulations and optimal energy system determination, where geographical location and availability of energy sources, load dynamics, component technical and economical characteristics were considered. A remote household with electricity consumption of 11 kWh/day with a 3,8 kW peak power demand was considered as the stand alone load. Results show the optimal feasible system with lowest total net present cost. It was found that almost a ten-fold (34 kW) renewable technology capacity is required to meet the demand.

PIRC, A., DROBNIČ, B., MORI, M., SEKAVČNIK, M.
PLANNING OF A SELF-SUFFICIENT ENERGY SYSTEM WITH INTERNAL COMBUSTION ENGINE
KOMUNALNA ENERGETIKA / POWER ENGINERING, 9

abstract

The paper presents method of optimization of a self-sufficient energy system configuration. At the beginning an optimisation method for advanced planning of energy supply systems is presented. Secondly, Mathwork’s Simulink was used to describe dynamic mathematical model consisting of energy user, energy production unit (internal combustion engine - ICE), energy saving capacities (battery) and regulation. At the end optimal system was found through a series of simulations which ensures stable and rational energy supply with respect to different rules of operation, particular sub-system’s sizes and economical aspects. At the end, results, appropriate diagrams and future guidelines are shown.

MORI, M., SEKAVČNIK, M.
EMPIRICAL MODEL FOR CONVECTIVE HEAT TRANSFER IN ROTATING AXIAL CASCADE
KOMUNALNA ENERGETIKA / POWER ENGINERING, 13

abstract

This paper presents a method of combining numerical and experimental results and empirical model for convective heat transfer in rotating axial cascade. The method is a combination of infrared thermography and numerical simulations and is useful in rotating environments, which are highly problematic to implement any measurement. The method represents a considerable simplification of the acquisition of the distribution of Nusselt numbers at the observed surface and allows the study of convective heat transfer. The observed surface temperature is measured by infrared thermography. Experimentally obtained temperature distributions are evaluated by numerical obtained by using statistical method. To calculate the Nu number is further used numerically calculated heat flux and measured temperature distribution for the known geometry of the axial cascade. The results are presented as a 2D distribution of Nu numbers for different flow conditions (Re) and at different rotational speeds (Ro). The empirical model is derived, which gives the dependence of Nu number distribution from the influence of rotation (Ro) and flow conditions (Re).

SENEGAČNIK, A., GLAVINA, U., SEKAVČNIK, M.
ORC – ORGANIC RANKINE CYCLE ALSO IN SLOVENIA
KOMUNALNA ENERGETIKA / POWER ENGINERING, 15

abstract

The article deals with ORC (Organic Rankine Cycle) process. This is a thermodynamic power cycle for conversion low temperature heat into mechanical work. The working media is an organic refrigerant. Operating parameters are lower than in water cycle. Due to specific properties of refrigerant also the ORC process has some peculiarities. The article presents the ORC process, which is applied in the Slovenian industry. Generator power is 125 kW, working media is HFC245 fa (R245 fa). Some specific features and operating experience of ORC processes are addressed in this article.

SENEGAČNIK, A., SEKAVČNIK, M.
REPOWERING OF WASTE HEAT USING ORC IN SLOVENIA
KOMUNALNA ENERGETIKA / POWER ENGINERING, 6

abstract

The article deals with ORC (Organic Rankine Cycle) process. This is a working cycle for conversion of low temperature heat into mechanical work. The working fluid is an organic refrigerant. Due to specific properties of refrigerant also the ORC process has some peculiarities. The article presents the ORC process, which will be applied in the Slovenian industry providing a generator power of 120 kW. Some specific features of ORC processes are addressed and the impact of implementation of heat exchangers is analysed. Analysis of the impact of cooling water temperature on the operation of ORC process is also provided.

PIRC, A., SEKAVČNIK, M.
ANALYSIS OF ENERGY SUPPLY SYSTEMS DECENTRALIZATION IN URBAN AREA
KOMUNALNA ENERGETIKA / POWER ENGINERING, 7

abstract