Latent Thermal Energy Storage Technologies and Applications: A Review

The achievement of European climate energy objectives which are contained in the European Union's (EU) “20-20-20” targets and in the European Commission's (EC) Energy Roadmap 2050 is possible, among other things, through the use of energy storage technologies. The use of thermal energy storage (TES) in the energy system allows to conserving energy, increase the overall efficiency of the systems by eliminating differences between supply and demand for energy. The article presents different methods of thermal energy storage including sensible heat storage, latent heat storage and thermochemical energy storage, focusing mainly on phase change materials (PCMs) as a form of suitable solution for energy utilisation to fill the gap between demand and supply to improve the energy efficiency of a system . PCMs allow the storage of latent thermal energy during phase change at almost stable temperature. The article presents a classification of PCMs according to their chemical nature as organic, inorganic and eutectic and by the phase transition with their advantages and disadvantages. In addition, different methods of improving the effectiveness of the PCM materials such as employing cascaded latent heat thermal energy storage system, encapsulation of PCMs and shape-stabilisation are presented in the paper. Furthermore, the use of PCM materials in buildings, power generation, food industry and automotive applications are presented and the modelling tools for analysing the functionality of PCMs materials are compared and classified

Technology of Multistage Hydraulic Fracturing in Horizontal Wells: Development Experience of Shaly Carbonates in the US and Its Adaptation for the Fields of the Republic of Tatarstan

The paper considers efficient development of Domanic reservoirs in Tatarstan using multistage fracturing technology in horizontal wells, based on the analysis of developing Shaly Carbonates in the United States, which are the closest in terms of geological and physical characteristics. Simulation in the software product GOHFER was carried out. Three types of multistage fracturing were considered: acid, proppant, and combined. Calculations show that practically all types of multistage fracturing with 5 stages are either not profitable, or are on the verge of profitability. Acid and combined multistage fracturing are the most effective at 10 stages; net discounted income for 5 years of operation is 90-100 million rubles. All three types of multistage fracturing are effective at 20 stages; acid and combined multistage fracturing are also characterized by the biggest net discounted income of 240-280 million rubles

Investigating the Feasibility of Energy Harvesting using Material Work Functions

There is an on-going search for miniaturized efficient energy harvesting devices which will capture energy from the environment and transform and supply enough electrical power for the autonomous operation of small low power-demand electronic devices [1]. The concept of energy harvesting is especially attractive as it could be applied when battery replacement is difficult or when recharging in a conventional sense may prove to be not cost effective. Also this concept could be used successfully when continuous operation without maintenance is required. Electronic devices, with low power demand, can be energized using vibration energy harvesters which gather and transform energy from mechanical vibrations. This investigation looks at the feasibility of a method of energy harvesting from mechanical vibrations using the naturally occurring charging phenomenon within a system of two bodies which possess different work functions. A work function is defined as the minimum thermodynamic work (i.e. energy) needed to remove an electron from a solid to a point in the vacuum immediately outside the solid surface. A work function is not a characteristic of the bulk material but rather is a property of the surface of the material and depends on the material crystal face and presence of contaminants. The critical difference between a work function energy harvester (WFEH) and the electrostatic energy harvester is that the former does not require any electrets (dielectric materials that has a quasi-permanent electric charge or dipole polarisation) or external power sources. In this work, a brief review of similar technologies, namely piezoelectric, electromagnetic and electrostatic energy harvesters is first given. This is followed by the development of a theoretical model and an investigation of different WFEH operation modes and miniaturization of a WFEH, with conclusions on a possible optimum mode of operation and method of miniaturization. The design of an experiment to test the developed theory is then presented followed by some preliminary results. Generally it is found that WFEH has potential for use in energy harvesting applications with the possibility of giving equal or better output power when compared to traditional electrostatic harvesters