Deviceless cement-based structures as energy sources that enable structural self-powering

Abstract

The use of large deviceless structures present in the civil infrastructure of any city to generate electricity is revolutionary. Cement-based structures are dominant in the civil infrastructure. This paper addresses the feasibility of using cement-based structures without poling or any particular admixture as energy sources. This enables structural self-powering, with applicability to existing and new structures. This performance of the basic cement-based material (cement paste) is reported. It is a true electret (a permanent electric dipole requiring no poling). The DC electric field E in the electret increases with inter-electrode distance l, thus larger structures are more effective. For l = 20 mm, E = 1.4 V/m and the electret discharges upon short-circuiting and charges upon open-circuiting, giving power density 1.9 × 10−4 W/m3, energy density 3.7 × 10−3 J/m3, current density 1.4 × 10−4 A/m2, participating carrier density 4.5 × 1017 m−3 and discharge time 570 s. For large l, large volume, and 72 discharge-charge cycles per day, the energy from a cement-based slab is estimated to be high enough to power dozens of households. With the start of discharge occurring at different times for different parts of a structure, energy can be provided continuously. Pyropermittivity and pyroelectret (effects of temperature on permittivity and E, respectively) enable thermal energy harvesting. Per heating cycle (20–70 °C), the pyropermittivity-based and pyroelectret-based energy densities are 7.9 × 10−7 and 2.5 × 10−8 J/m3, respectively. Pyropermittivity, pyroelectret and pyroresistivity enable temperature self-sensing, with pyroelectret being most sensitive. Upon heating, the 2-kHz permittivity and E increase reversibly by 20% and 120%, respectively, while the DC resistivity decreases reversibly by 80%.