Jaroslav Jerz; Arun Gopinathan; Jaroslav Kováčik
Abstract
The structure of aluminium foam is highly porous consisting of aluminium (or its alloy) filling up the space among gas pores. Although pores formed during foaming of aluminium melt are closed, there are always microscopic cracks in the walls of solid foam, so that the porosity is predominantly ...
Read More
The structure of aluminium foam is highly porous consisting of aluminium (or its alloy) filling up the space among gas pores. Although pores formed during foaming of aluminium melt are closed, there are always microscopic cracks in the walls of solid foam, so that the porosity is predominantly open. This preference of aluminium foam allows to fill pores with a Phase Change Materials (PCMs) capable repeatedly to store and release a huge amount of latent heat of phase transition from solid to liquid state and vice versa. The excellent thermal conductivity of the aluminium, forming the pore walls, predetermines aluminium foam castings for the production of highly efficient heat exchangers in various industrial sectors, especially in the building industry. The most promising technique for the production of near-net-shaped structural components containing a dense aluminium surface skin and porous inner foamed aluminium structure is powder metallurgical route. Lightweight self-supporting interior ceiling panels impregnated by PCM presented in this contribution, utilize their high mechanical stiffness and their ability to store large amounts of latent heat at a constant temperature. The application of foamed aluminium appears to be very promising also for heat exchangers covering the entire pitched roof of the building which provides not only the better recovery of the heat from the building surroundings but also the dissipation of unwanted excess heat from the interior when needed.
Mariya Aleksandrova
Abstract
Portable and smart electronic devices are powered by batteries whose life is limited. On the other hand, in recent years the idea of renewable energy and methods of its obtaining by environmentally friendly technologies gained popularity. The conversion of energy from various sources in the surrounding ...
Read More
Portable and smart electronic devices are powered by batteries whose life is limited. On the other hand, in recent years the idea of renewable energy and methods of its obtaining by environmentally friendly technologies gained popularity. The conversion of energy from various sources in the surrounding environment (energy harvesting) solves the problem of battery-less power supply and satisfies the modern concepts of "clean" energy. One of the mechanisms for electrical energy generation is the piezoelectric effect, which relies on mechanical activation (vibrations, pressure, force) and the corresponding devices are piezoelectric energy harvesters. This article has overviewed the global situation, efforts, and prospects of the development of piezoelectric materials and harvesting devices in terms of research interest, industrial implementation, sectors of application and market forecasts.