Roughly a third of humanity still cooks on biomass. The thermodynamics are brutal: a flame at well over 1,000 K is used to warm a pot to 373 K, and almost all of the fuel's work potential is annihilated in the temperature drop. This open access IntechOpen chapter examines a device that recovers a sliver of that loss — an advanced micro-gasifier cookstove fitted with an annular thermoelectric generator, analysed as a combined heat and power system for rural villages.
The measured performance
The proposed cookstove-based annular thermoelectric generator produces 10 W of electrical power, at an electrical energy efficiency of 6.78% and an exergy efficiency of 15%. The maximum hot-side temperature without annulus gain is 275 °C. For comparison within the same analysis, the stove alone is measured at 17.3% exergy efficiency, and a comparable annular generator elsewhere in the literature reaches 6.76% at 149 W heat input and 0.8 A working current.
The annular geometry is the engineering point. Wrapping the thermoelectric modules cylindrically around the combustion chamber increases the heat transfer area on both the hot and cold faces relative to a flat generator of the same footprint, which raises the heat throughput each module sees and therefore its output. The chapter notes that energy efficiency for the stove considerably exceeds its exergy efficiency, because the energy extracted into hot water is worth far less than its quantity suggests once the temperature constraint is applied.
What 10 W buys
Ten watts is not electrification. It is enough for LED lighting, a phone charge and a fan to drive the gasifier's own combustion air — which is the real prize, since forced draught cuts particulate emissions sharply and removes the need for a separate power source in an off-grid household.
The exergy view
The gap between 6.78% electrical and 15% exergy efficiency is the whole story of cogeneration in one pair of numbers: crediting the useful heat as well as the electricity roughly doubles the figure, because the heat is genuinely wanted here. Even so, 15% means five-sixths of the fuel's work potential is still destroyed, and the stove alone at 17.3% shows that the thermoelectric is harvesting from a stream that was already largely spent. The lesson is not that thermoelectrics are inefficient — it is that combustion for cooking destroys the exergy long before any recovery device sees the heat. The largest gain available in this duty is not a better generator but a smaller temperature drop.
