Update on Design and Development of a TEG Cogenerator Device Integrated in Self Standing Gas Heaters

The heating of environment through combustion of natural gas is widely used in both residential and industrial environments, using several different types of systems and plants. A relevant case is that of the gas stoves, where each heat-radiating unit includes the gas combustor and operates autonomously with local gas and, optionally, electrical feeding. In certain industrial or commercial environments, localized heating using this type of heaters is often preferred instead of heating the whole environment: in such situations, the use of independent units may be more flexible and efficient, or sometimes even the only option. As we started investigating in our previous work [1], for this type of autonomous gas heaters a thermoelectric generator (TEG) can be integrated within the heater and locally produced electrical power may allow unit's installation and operation without the need of a connection to the electrical grid, improving ease of installation and increasing the overall efficiency through reduction or elimination of electrical consumption for safety, monitoring and control systems and for ancillary or accessory functions like fan ventilation or illumination. Following the development plan introduced in [1], a new prototype of autonomous gas heater for outdoor commercial environments has been realized, integrating an improved TEG device, with simpler design, more robust and more easily operated by the end user. A small amount of heat is withdrawn by the device at the base of the combustion flame and is converted into electricity by providing self-sustained operation, the control of the safety valve of the gas with no current drain from the backup battery and, moreover, the charging of the battery itself and power for high efficiency LED lighting. With respect to the first prototype described in our previous report, the new one operates at a thermal regime that is more stable, more moderate and less subject to fluctuation or to the risk of overheating during real-world operation. This result permits a more consistent conditioning and a more efficient exploitation of the electrical output. Nevertheless the design requires further development in two possible directions: if current performance of the TEG are accepted, the maximum power output can only supply half of the desired power for high efficiency LED lighting but the requirements for some critical components (specially the TEG modules) can be downsized to match less severe operating conditions, permitting a simplification and a relevant cost reduction for the product (possibly using high-end Peltier modules which are commercially available); on the other hand, with the TEG modules already used there's still a wide margin of performance increase, by correcting the sizing of the heat collector and of the heat sinks.