ELECTRICAL INSTALLATION WITH A SOLID-STATE THERMAL ENGINE BASED ON SHAPE MEMORY ALLOYS FOR GENERATING ELECTRICITY FROM LOW-POWER HEAT SOURCES

The work is devoted to the study of processes of conversion of low-potential thermal energy into electrical energy using a solid-state heat engine based on shape memory alloys (SMA). The relevance of the topic is due to significant losses of low-temperature heat in industrial and energy systems and the need to improve the energy efficiency of autonomous power sources. NiTi alloy springs are used as drive elements, which implement reversible austenite-martensite phase transformations and ensure the direct conversion of thermal energy into mechanical work. The aim of the work is to develop a physically based mathematical and numerical model of a heat engine, taking into account cyclic heating and cooling, thermomechanical hysteresis, the inertia of the mechanical system and electromechanical interaction with the generator, as well as to evaluate the energy characteristics of the power generation plant. A three-level approach to modelling is proposed, including an analytical quasi-static model for engineering estimates, a quasi-stationary moment balance model for determining steady states, and a complete dynamic system of differential equations that takes into account non-stationary heat transfer, phase kinetics, and inertial effects. Numerical integration was performed in Py-thon using fourth- and fifth-order Runge–Kutta methods. The simulation results confirmed the adequacy of the pro-posed model and showed the formation of self-stabilised rotation modes and power saturation. It was found that simpli-fied approaches provide a conservative estimate of energy performance, while the full dynamic model more accurately reproduces transient processes and real operating characteristics; the discrepancy between the models does not exceed 15–20%. The influence of the bilateral shape memory effect, which in the temperature range of 70–80 °C can increase electrical power by 20–30 %, was investigated. The expediency of partial immersion of SMA elements in the coolant to ensure stable cyclic heat exchange was demonstrated. The results obtained confirm the prospects of using SMA engines for the utilisation of low-potential heat and the creation of compact autonomous systems for small-scale electricity generation. References 20, figures 7.