Optimum operation of a prototypical pyroelectric energy converter for harvesting waste heat

This paper is concerned with direct energy conversion of waste heat into electricity using pyroelectric materials. The pyroelectric effect refers to the flow of charges to or from the surface of a material upon heating or cooling. The present study investigates the design and operation of a pyroelectric converter assembly based on the Olsen cycle using multistage pyroelectric elements and heat regeneration. Cooling and heating cycles of the pyroelectric elements are achieved by oscillating the working fluid between hot and cold sources tinder laminar flow conditions. Multistaging consists of placing different pyroelectric elements in series with increasing Curie temperatures from the cold to the hot sources. Moreover the heat required to increase the temperature of the lattice is regenerated back and forth between the working fluid and the pyroelectric elements instead of being lost to the heat sink. A prototypical pyroelectric converter is simulated by solving the two-dimensional mass, momentum, and energy equations using finite element methods. The pumping power and the heat transfer rate required for the cycle as well as the electrical power generated are estimated from the computed pressure, temperature, and velocity. Finally, the overall thermodynamic efficiency of the system is calculated and compared with reported experimental data.