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Abstract The main objectives of the authors’ current paper include thermal sizing of a regenerative concrete heat exchanger for coupling of the biomass plants and the heat engine like ORC (Organic Rankine Cycles). The main challenge for regenerators is the temperature difference between charging and discharging process. Heat energy charging can be done by hot flue gas or high temperature fluid circulation through solid modules of storage. Optionally heat supply can be obtained by using of electrical energy. The concrete modules contain embedded piping for charging and discharging and definition of the geometric parameters like piping size and distance represented in current work. The application of unsteady heat transfer equations for heat storage description was checked by comparison with experimental and theoretical results. The paper offers equations for evaluation of storage efficiency for different heat transfer coefficient, dimensions of storage and time duration of warming and cooling process.

Abstract Thermal energy systems with phase change materials (PCMs) have been studied extensively within small scale experimental systems with different arrangements, which have not been scaled to the size that could be utilized. The aim of this paper is to design an experimental plan for studying the potential of PCM within real scale thermal storage with a volume of 367 litres. Previous research has shown that flow rate is one of the main parameters that impact the performance of the system and, since change in the size of the tank relates to changes in flow rate, an experimental study of a tank with the size similar to that of commercial tanks is necessary. Secondly, since multiple melting temperature PCMs will be used, the placement of PCM is focal. The chosen flow rates are 2, 6 and 10 l/min and three sets of placement – no PCM as a base scenario, 55 °C PCM at the top and as third, a placement of four melting temperature PCMs with the one with highest melting temperature at the top – 65, 55, 34, 24 °C. The main analysis parameters are collector efficiency, comparison of delivered solar energy to consumer (solar fraction), tank losses and additionally required energy to prepare water (auxiliary energy).

Main aspect when solar thermal energy storage (TES) is considered is thermal storage capacity in form of sensible heat, latent heat or chemical energy. In case of solar systems, solar TES provide a solution for mismatch between energy supply and energy demand. Higher capacity reduces the size of the system and increases overall efficiency [1]. Water is used in almost every system as working fluid due to characteristics like nontoxicity, abundance, high specific heat and suitability for wide range of heating applications [2]. Since the temperatures that occur in solar heat storage is above 0 °C and below 100 °C, no phase change of water can occur and energy is stored only as sensible heat. Wide variety of phase change materials (PCM) have been created and accepted as suitable to make use of latent heat storage (LHS). While use of phase change materials in latent thermal heat storage have been studied thoroughly, a lot less studies have been looking into use of different melting temperature phase change materials to enhance the efficiency of solar system. Solar systems in many cases are used in existing buildings where available space is limited. By increasing efficiency and energy density, it is possible to store more and take less space.

The paper reviews possibility to increase electricity production in co-generation plants in the time range, when electricity cost is high. Daily heat and electric load schedules are different, in order to get maximum efficiency the authors discusses the decisions on installing a heat storage for shifting the heat load. During the high price of electricity, cogeneration produces a maximum of electricity, and heat accumulates to heat storage with following heat discharge to the district heating system to consumers. Such a system allows you to create a smart grid between fuel consumption and heat/electricity production which will allow more efficient use of resources.

The present article describes the experience amassed in the operation of smart electric thermal storage (SETS) heaters within the RealValue project. The task of the project was to evaluate the possible benefits from centralised use of SETS by using the electricity market prices. This paper pays special attention to the operation of SETS at substations where there is no staff and a temperature of not less than 15 °C needs to be maintained. Also, there is a recommendation and calculations regarding the possibility of using storage devices for minimizing the heating costs for power substations.

The thermal energy storage (TES) system installation provides the optimization of energy source, energy supply security, flexibility of power plant operation and energy production. The aim of given research is feasibility analysis and evaluation of thermal energy storage system installation at Riga cogeneration heat power plant (CHPP) Nr. 2 with P el = 832 MW and Q th = 544 MW (cogeneration unit Nr. 1 and Nr. 2). The six modes were investigated: four for non-heating periods and two for heating periods. Different research methods were used: data statistic processing and analysis, forecasting, financial analysis, correlation and regression methods. Finally, the best mode was chosen with aim to increase of cogeneration unit efficiency during the summer period.

Abstract Solar technologies are flexible and can be used for both centralized and decentralized energy production. The main aim of this article is to compare different solar technologies and configurations for integration into the DH system. The multi-criteria analyses method is used to rank different alternatives based on several criterions. The evaluation of criterions has been based on previous studies conducted. The multi-criteria analyses allow to compare different solar system alternatives that cannot be compared directly due to differences in their scale, type of energy produced and consumed, investment levels, etc. For the particular DH system researched, the most desirable solution is the PVT panel integration with an area of 1000 m2 which is aligned with the actual DH company’s power consumption. However, the results are strongly impacted by the assumed investment levels, efficiency of the technologies and other assumptions that could be further analysed by the help of sensitivity analyses.