Electricity without Fuel

Abstract

Most power plants produce electricity by converting a mechanical motion into alternating current (AC). Photovoltaic solar panels convert an electromagnetic flux of light into direct current (DC). In general, electric energy can be harvested from a flux in the environment or from a change of the environment itself. One can produce electricity from mechanical, chemical, thermal, electromagnetic (light), or another physical flux, or from a change of temperature, chemical composition, or a physical field: gravitational, magnetic, electric, mechanical stress and strain, etc. Flux examples are mechanical motions of air and water, surface waves and tides, heat fluxes due to a temperature gradient, solar light, and a chemical flux (such as humidity propagation in the atmospheric air or diffusion of salt in water due to a gradient of salinity at the mouth of a fresh-water river flowing into an ocean). Environmental changes are under-used in energy production, although people are exposed to daily and seasonal changes of the environment, which include changing air temperature, pressure, humidity, and composition, tidal changes of the gravitational field, and less periodic changes of the geo-magnetic and electric fields. Production of electricity without fuel from the environmental changes and fluxes requires a durable infrastructure for a costeffective utilization of the "semi-perpetual" energy resources.

Viable Materials with a Giant Magnetocaloric Effect

“…One can see trends towards increasing MCE, replacing toxic elements, and eliminating expensive and critical elements, leading to a cost reduction of the best-in-class materials [30,31,296]. Discussed applications of magnetocaloric materials include cooling and heat pumping [2-8,299-301], as well as energy generation [1]. MCE can be used for the thermo-magneto-electric energy transformations, such as conversion of energy into a temperature change [3][4][5][6], or conversion of a changing temperature [1] into a changing magnetic field, which generates voltage in a coil [18].…”

“…Discussed applications of magnetocaloric materials include cooling and heat pumping [2-8,299-301], as well as energy generation [1]. MCE can be used for the thermo-magneto-electric energy transformations, such as conversion of energy into a temperature change [3][4][5][6], or conversion of a changing temperature [1] into a changing magnetic field, which generates voltage in a coil [18].…”

“…Magnetization in the FM state and magnetic entropy in the PM state correlate with the amplitudes of atomic moments M a , which are large near half-filling of f or d band (e.g., in Gd or Mn in a neutral state). Electronic entropy correlates with electronic DOS at E F , which is large near 1 4 or 3 4 filling of f or d band. Thus, elemental abundance, toxicity, safety, electronic structure, and magnetism impose constraints on composition of magnetocaloric materials, viable for industry.…”

“…A change of temperature T can be converted to electricity [1]. A significant fraction of consumed electricity is used for heat pumping, which results in a targeted cooling or heating [2].…”

“…A solid-liquid phase transition in isentropically compressed Helium-3 is used for Pomeranchuk cooling to sub-Kelvin temperatures [14,15]. Solid-solid phase transitions in magnetocaloric materials can be used for energy transformations: for cooling and heat pumping [10,16,17] at various T, including cryogenic and room temperature (RT), as well as for generating electricity from a changing temperature [1,18]. There is a hope that use of caloric materials will lead to a more cost-effective, energy-efficient, and environmentally friendly alternative to the traditional vapor-compression refrigeration [3].…”