Introduction

The conversion of energy, at any level, and around the world, involves a significant waste heat production (1200 TWh/year). Depending on the type of application, there are several ways to recover energy that depend on the space available at the installation site, heat transfer and conversion efficiency, and especially the difference between the highest and lowest temperature available. However, the main drawback of most used conversion tools in low temperature applications lies in their nature, namely that they are at solid state and are therefore less adaptable, flexible and resilient than liquid devices. The proposed system is designed to convert thermal energy into kinetic energy using thermomagnetic convection, a particular fluid motion allowed by the thermal gradient and a parallel static magnetic field.

Technical features

The proposed device includes a first and a second layer of heat-conductive material, and an intermediate layer of polymer material, placed inside the two layers and having lower thermal conductivity than both layers. In the latter is contained a plurality of channels, in which we can find a colloidal suspension based on a liquid solvent and a dispersion of nanoparticles of magnetite, called magnetic fluid. This fluid is able to flow along each of these channels as a result of a temperature gradient applied between the first and the second layer. Specific coils wound on the channels are used to extract the electromotive force by induction (Faraday-Neumann-Lenz law). This system has been shown to produce a small amount of energy with a corresponding small thermal gradient (10 pW/K). TRL 5/6.

Possible Applications

• Industrial field
• Automotive field
• Wearable devices

Advantages

• Greater adaptability and flexibility thanks to liquid state
• Relatively high efficiency and stability compared to known solutions
• High scalability compared to known solutions (energy recovery from 1ºC temperature difference up to 200 ºC)
• Simple, economical and the materials used have low toxicity and low environmental impact