• Energy Research

Abstract Some of the heat sources (such as e.g. waste or renewable), are characterized by floating thermal and output characteristics. Thus, their application for powering vapour power plants, such as ORCs, which should utilize the heat sources having steady thermal and output characteristics is difficult. The floating heat source characteristics may potentially be improved using the heat storage devices providing the thermal energy accumulation at stable output and temperature level. Heat storage device can be adopted as a e.g. steady-level heat source for ORC system. In this paper different applications of the heat storage devices in ORCs were proposed and the results of experiments on powering the ORC system via heat storage device are presented. Moreover, the modelling of ORC system operating time for various types of the heat storage devices was carried out. The results showed that adopting the heat storage devices for powering the ORC systems is possible and it is a promising way of utilizing the waste and renewable heat sources featuring floating characteristics.

Some of the heat sources (such as e.g. waste or renewable), are characterized by floating thermal and output characteristics. Thus, their application for powering vapor power plants, such as ORCs, which should utilize the heat sources having steady thermal and output characteristics is difficult. The floating heat source characteristics may potentially be improved using the heat storage devices providing the thermal energy accumulation at stable output and temperature level. Heat storage device can be adopted as a e.g. steady-level heat source for ORC system. In this paper different applications of the heat storage devices in ORCs were proposed and the results of experiments on powering the ORC system via heat storage device are presented. The results showed that adopting the heat storage devices for powering the ORC systems is possible and it is a promising way of utilizing the waste and renewable heat sources featuring floating characteristics.

This paper concerns the issue of the proper selection of the operating parameters of the fluidised desiccant cooler. Despite the fact that fluidised desiccant cooling technology is being reported in the literature as an efficient way to provide cooling for the purposes of air-conditioning, the improper control of its operation can lead to a significantly worse performance than expected. The objective of the presented theoretical study is to provide guidelines on the proper selection of such operating parameters of a fluidized desiccant cooler, such as superficial air velocity, desiccant particle diameter, bed switching time, and desiccant filling height. The influence of the chosen operating parameters on the performance of fluidised desiccant cooling technology is investigated based on their impact on electric and thermal coefficients of performance (COP) and specific cooling power (SCP). Moreover, the influence of the outlet air temperature, humidity, and desiccant water uptake on the adsorption/desorption characteristics was investigated, contributing to better understanding of sorption processes.

Gas pressure reduction stations are commonly applied to decrease the pressure of natural gas in the transmission pipelines. In such stations, natural gas is expanded in throttling valves without producing any energy. Through the use of expander in natural gas pressure reduction stations, it is possible to recover the pressure energy of the natural gas during expansion, and drive the electrical generator. Possible solutions include turbines and volumetric expanders. However, turbines are complicated and expensive, while volumetric expanders are simple and cheap. This paper presents an analytical modeling of rolling piston expander work conditions when adopted to natural gas expansion. The main objective of this research was therefore a comprehensive analysis of influence of varied sizes of the expander components and natural gas thermal properties at the inlet and at the outlet of the expander, on the expander output power. The analysis presented in this paper indicates that the rolling piston expander is a good alternative to the turbines proposed for energy recovery in natural gas pressure reduction stations.

This paper reviews the applications of the multi-vane expanders in ORC (organic Rankine cycle) systems. The operating principle and design of the ORC systems are addressed in the introduction. Then, there is a brief review of the expanders applied in small-power and micro-power ORCs, and a discussion of the multi-vane expander design and operating principle as an introduction to a comprehensive review on the applications of the multi-vane expanders in ORC systems. The different features of the multi-vane expanders—i.e., the design of the expander, its geometrical dimensions and operating conditions, durability, applied working fluid, obtained power output, and efficiency—are analyzed in this paper. This review clearly indicates that multi-vane expanders are a promising alternative to the different types of the expanders applied in ORC systems.

Abstract Small- and micro-power ORC systems designed for domestic use by prosumers should be cheap and reliable. The main part of the ORC system cost is the price of heat exchangers and the expander. Multi-vane expanders are positive displacement volumetric machines which are nowadays considered for application in micro-power domestic ORC systems. The multi-vane expander design is very simple, which translates into low production costs. Compared to the other types of volumetric machines and micro turbines, which are adopted in micro-power domestic ORC systems, multi-vane machines feature a lower gas flow capacity, lower expansion ratios, and an advantageous ratio of the power output to the external dimensions. These machines are insensitive to the negative influence of the gas-liquid mixture expansion. Moreover, the multi-vane expander can be easily hermetically sealed, which is one of the key issues in the ORC system design. Multi-vane expanders feature power outputs of several hundred W to approximately 5 kW. Maximum gas pressure on the inlet to multi-vane expander reaches approximately 10 bar. The issues concerning the application of multi-vane expanders in such systems are innovative and not fully scientifically described. The solution of these problems requires comprehensive study and experimental analysis. This paper reports the results of experimental investigations carried out on domestic CHP ORC system adopting multi-vane expander under varied operating conditions. The experimental results showed that the expander indicated work varies in the range of 0.96—4.18 kJ/kg while its internal efficiency varies in the range of 17.2—58.3 % depending on the experimental conditions. Moreover, the results of numerical investigations on multi-vane expander operating conditions are presented. The numerical model of the expander was validated using the data obtained from the experiment and analyses were performed in ANSYS CFX software. The results proved that multi-vane expanders are suitable for domestic ORC systems and are a promising alternative to the other types of volumetric expanders used in such systems.

Abstract Air pollution with dust is particularly noticeable in winter. This problem is visible especially in those living areas in which furnaces fed by low-quality fuels are used for heating houses and flats. One of the possible ways of limiting the number of used furnaces may be heating and powering of the housing estates and villages by specially designed combined heat and power (CHP) steam (or vapor) power plants. To be competitive to other heating technologies these systems should be cheap, reliable and easy to operate. Therefore, their design should be as simple as possible. Steam or organic Rankine cycle (ORC) energy conversion systems utilizing simple volumetric expanders, which can be applied for distributed power generation are meeting these conditions. The article presents literature review as well as selected thermodynamic and design issues concerning these systems. Literature review gave an outlook on the modeling, experiments, operating conditions and possible configurations of steam and ORC CHP systems. Then, model of the CHP system was implemented in computer software. Thanks to the positive technical features and ability to operate with wet gas the screw machine was selected as the system’s expander. Selected experimental data obtained from the literature review were used for system modeling. Especially the operating conditions of the selected expander (i.e., maximum mechanical power, maximum inlet pressure, expansion ratio and internal efficiency) were assumed based on the experimental results, technical data and information reported in different papers. Expander’s operating conditions and technical data (in particular the value of maximum working fluid pressure allowable at the inlet to the expander) were the basis for pre-selection of working fluids which are possible to apply in the modelled system and selection of the heat source thermal parameters. Modeling was proceeded for different conditions and the results show that depending on the operating conditions and applied working fluid electric power output of the CHP system ranges between 1570 and 2511 kWe (for heat source temperature of 200 °C) and between 1583 and 2631 kWe (for heat source temperature of 150 °C). However, not only maximum power output should be considered as the selection criteria of the system design and working fluid choice. The other important criteria are related to maximization of the obtained electric power, minimization of the vapor pressure at the outlet of the vapor generator and at the inlet to the expander, minimization of the working fluid flow, minimization of fuel consumption and maximization of the temperature of the working fluid at the outlet of the expander. The modeling results show that from all cases studied the ORC CHP power plant utilizing screw expander, using MD2M as working fluid and featuring the electric power of 1570 kWe fed by rapeseed oil is the best possible solution if technical assessment criteria are taken into consideration. Such a system can cover the heating demands of ca. 9615 flats.