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A variant analysis of a potential configuration of a peak-load system which is based on SOE/SOFC module and hydrogen storage is presented in this article. The most rational configuration of the power plant with the SOE/SOFC appears to reach a high total electricity-to-electricity conversion rate with small and medium size plants. The system contains the minimum amount of devices where the anode side of the SOFC is exposed to the hydrogen storage directly. In this solution no compressors or pumps are needed and the system has no moving parts. Oxygen is then released to the surrounding environment or can be stored in an additional tank. In theory, it is possible to obtain higher efficiencies, but this requires much higher capital expenditures (additional heat exchangers, gas turbines, set of heat regeneration heat exchangers, etc.) and much higher parameters of working media in the system (1400 C, 30 bar). The absolute efficiency of the system depends on the assumptions made and the way in which the mathematical model was developed. It may change due to them, hence the presented analysis is qualitative rather than quantitative.

Small and micro energy sources are becoming increasingly important in the current environmental conditions. Especially, the production of electricity and heat in so-called cogeneration systems allows for significant primary energy savings thanks to their high generation efficiency (up to 90%). This article provides an overview of the currently used and developed technologies applied in small and micro cogeneration systems i.e., Stirling engines, gas and steam microturbines, various types of volumetric expanders (vane, lobe, screw, piston, Wankel, gerotor) and fuel cells. Their basic features, power ranges and examples of implemented installations based on these technologies are presented in this paper.

This paper presents the model of compressed air energy storage (CAES) expansion part with flue gas recovery. The model is built based on classic CAES expansion part and supplemented with heat recovery steam generator and steam turbine. The model is built in the GateCycle software and tested based on real data acquired from one of existing CAES plant. As a result the influence of air inlet pressure on power and efficiency of such a system is presented.

In the paper The Liquid Air Energy Storage (LAES) technology is described. The LAES can be constructed in every place, bases on well-known components and is dedicated for system scale and short-term energy storage. The most important issue is to increase the energy storage efficiency and its economic attractiveness. For that purpose the Organic Rankine Cycle application was proposed. The new variant of the Liquid Air Energy Storage with Organic Rankine Cycle (LAES-ORC) was developed, including technical analysis, the mathematical model implementation description, simulation results and its analysis.

The paper presents the influence of selected components parameters on the performance of supercritical carbon dioxide power unit. For this analysis mathematical model of supercritical recompression Brayton cycle was created. The analysis took into consideration changes in the net cycle power and efficiency for different compressor inlet temperatures. The results were obtained for a fixed minimum pressure of 7.4 MPa and fixed recompression split ratio. The studies conducted in this paper included also consideration of sensitivity of the cycle efficiency to a change in recuperators heat transfer area. In order to determine how each recuperator influences the cycle performance, an analysis of efficiency dependence on the recuperators area was made. Another parameters that were investigated are to a change in turbine and compressors isentropic efficiency and their influence on the cycle efficiency. In the reference cycle, isentropic efficiencies were set up as 88% for both the main and recompression compressor, and 90% for the turbine. Since isentropic efficiency is a sort of measure of broadly defined quality of a turbine or compressor, including airfoil shape, sealing, etc., it may be a significant cost factor that should be considered during cycle design. Therefore, a sensitivity analysis of cycle efficiency to both compressors and turbine isentropic efficiencies was conducted.

This article presents an analysis on possible ways of utilizing low-temperature waste heat. If well-designed, this could contribute to increasing the efficiency of power plants without introducing many complex changes to the whole system. The main analysis focuses on the location of the regenerative heat exchanger in the facility. This could differ with varying temperatures of working media in the system. The base for investigations was a 800 MW-class power unit operating in off-design conditions and supplied with steam from an BB2400 boiler. Modifications to the model were made using commercially available software and by applying the Stodola equation and the SCC method. It allowed to determine the most suitable position for installing the low-temperature heat exchanger. Calculations for off-design conditions show that, after making some modifications to the system, both heat and electricity generation could be increased through the addition of a low-temperature heat exchanger.

The paper presents a variant analysis of the structure of SOFC hybrid system. The systems are divided into two gropus: atmospheric and pressurized. The main parameter of such systems are indicated and commented. The comparison of various configurations is shown in a view of efficiency obtained. The ultra high efficiency (65% HHV, 72% LHV) of electricity production seems to be possible by systems like these.

The paper aims to compare the models of working fluids against experimental data for carbon dioxide close to its critical conditions. Fortunately, most of the work is already done and published where the authors compared the models based on the equation of the state (EoS). There are a few other models which were not investigated, thus we would like to add a few new results here and focus only on near-critical properties where the biggest deviation between experimental and calculated properties can be observed. The area of interest was pressure range of 7.39 – 20 MPa and temperature range of 304-340 K just above fluid critical point (7.39 MPa, 304.25 K). Model validation was performed for density and heat capacity as one of the most important parameters in preliminary cycle analysis.

An MCFC model concept is presented. The MCFC model was built in HYSYS.Plant environment is based on its standard libraries. The main elements of the MCFC model and chemical reactions are presented. Selected performance characteristics at the design point of MCFC are presented. A new equation is given to define MCFC voltage, which was obtained based on new assumptions and which can be used instead of the classical approach.