Energy Conversion Materials Sample Clauses

Energy Conversion Materials. The efficient conversion of energy between heat, light and electricity plays an important role in the implementation of the Chameleon Suit concept. Thermoelectric elements must be able to remove sufficient amounts of heat from an astronaut to cool him in the hottest environments. Photovoltaic arrays have to capture enough solar energy to power the thermoelectrics and reduce the overall energy storage needs of the suit. Electrochromic layers must be able to modulate their infra-red emissivity levels across a large enough range to provide both effective insulation and rapid heat rejection. All of these materials will also have to be manufactured into the flexible, durable and space compatible suit layers. The desired properties for these energy conversion materials are beginning to be found in electrically conducting polymers and advanced thin film devices. Thermoelectrics Thermoelectrics are devices that directly use electrical energy to move heat from one side of the device to the other side. Conversely, they can be used to generate electricity from the movement of heat energy across the device. The primary advantages of thermoelectric devices is that they have no moving parts, can be made smaller and lighter than vapor compressor refrigeration systems, and have no expendables such as water for a sublimator. A thermoelectric cooling system for a space suit has other advantages as well. First, they can be run in reverse to provide heat when needed. They can be distributed over the suit to achieve direct, local thermal control. Finally, when they are not needed for heating or cooling, they can capture some of the thermal energy that escapes the suit and convert it to electrical energy. The performance of thermoelectric devices is typically measured with a dimensionless variable called its figure of merit: ZT. It is a measure of a material’s ability to generate a temperature difference across it at a particular temperature, when an electrical current is passed through it. α 2T ZT = ρK T Where α, Τ, ρ, KT are the Seebeck coefficient, absolute temperature, electrical resistivity and thermal conductivity, respectively (Reference 43). During the 1950’s and 1960’s there was a considerable effort to develop thermoelectric materials. Researchers at the time realized the great potential of thermoelectrics. However, the maximum ZT achieved at the time was 1.0, which does not compare favorably to more traditional ways of moving heat, except in relatively small devices ...