2.1 System description

efficient biomass advanced cookstove technology is necessary. An accurate inbuilt electricity generation unit to drive forced draft combustion fan/blower, to optimise

For the previous two decades, the use of thermoelectric generators and its applications have been investigated and improved worldwide due to its significant advantages of straight conversion of thermal energy into electricity with minimum/ no moving parts and reduced noise. Hence, newly developed thermoelectric generators (TEGs) are accepted as green sustainable technology and are widely used as flexible generators for a diversified applications [1, 2]. A combined advanced micro-gasifier cookstove with the TEG for heat and power cogeneration from a

Champier et al. [3] have developed a prototype of a biomass cookstove with a higher-efficient combustion chamber (CC), and TEG modules are attached to either side of the cookstove. It was found from the experimental investigations that 6 W of electrical power was generated from four numbers of TEG. Experimental analysis was performed by Nuwayhid et al. [4] on the biomass domestic wood stove coupled with natural convection-cooled thermoelectric generator. It was obtained from the results that about 4.2 W of power was produced from each component. Kraemer et al. [5] built an innovative solar flat thermal panel for electricity generation adopting Seebeck effect concept with higher thermal concentration. There was an interesting result obtained from the study that an electrical convention efficiency of 4.6% for 1000 W/m<sup>2</sup> solar conditions is about eight times much more powerful than the other systems. Omer and Infield [6] proposed a conceptual model of a TEG for the estimation of an optimal device in power production. By means of using their developed model, four different TEGs were compared. Besides, they have developed a two-stage solar concentrator for a cogeneration system (combined heat and power from the thermoelectric modules). It was proven from the studies

conducted by Omer and Infield [7] that an improvement of thermal efficiency as well as overall characteristics of the solar thermal concentrator for combined heat and thermoelectric power generation can be achieved using second stage concentrator. Atik [8] studies the thermoelectric performances of the concentrating collector, receiver and TEG modules. The electric power generation efficiency, system efficiency and surface area temperature of the receiver system were obtained from the

suggested a model to examine the conceptual efficiency of solar thermoelectric generators (STEGs), which includes thermal concentration as well as optical concentration. It was obtained from his study that the component efficiency increases with increase in hot side temperature, but thermal efficiency decreases with increasing hot side temperature. Furthermore, he stated that the STEG efficiency can be improved when it has been maintained under evacuated condition.

Manikandan and Kaushik [1] performed the energy and exergy study of the solar annular thermoelectric generator (SATEG) in view of the impact of Thomson effect in concurrence with Peltier effect, Joule effect and Fourier heat conduction. Their study proposed annular thermoelectric generator as an alternative for flat thermoelectric generator (FTEG) to increase the cross-sectional area along the radial direction. They have established that the power output (W) and whole exergy efficiency (%) of the SATEG were 1.92 W and 5.02%, respectively, which was established to be 0.52 and 0.40% greater than that of SFTEG. They suggested that this SATEG system could be effectively used as the thermal insulation material as it offered better heat transfer characteristics; it was simple to drive and maintain

From an in-depth literature survey, it is established that there are certainly no research studies available on CHP system in cookstove and an ATEG. Studies have

compared to the solar flat plate thermoelectric generator.

) and from different concentration ratios. Chen [9]

performance with high efficiencies, is proposed in this current study.

Biomass for Bioenergy - Recent Trends and Future Challenges

single system is presented here.

different solar radiation (W/m<sup>2</sup>

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The design and fabricated CC of the proposed biomass advanced micro-gasifier cookstove [10–15] are clearly depicted in Figure 1. The CC is fabricated using carbon steel with an inner diameter of 110 mm and an inner height of 155 mm. By means of increase in the proportion percentage (%) of carbon content, the cylinder material becomes harder and stronger providing higher creep properties. Carbon steel with high carbon content has been used to ensure it can withstand high temperatures.

The secondary air (combustion air) injection of the proposed cookstove is skewed to an angle of 45° towards bottom grate [11, 12, 16]. This is to confirm the better turbulence in the course of volatile combustion and for the period of char combustion. Exfoliated vermiculite mineral matter of 93% with glass wool of 2%

Figure 1. Model of the proposed cookstove.

and Portland cement of 5% altogether by weight is moulded into a mixture for the preparation of the thermal protection lining material inside the concentric cylindrical CC. The air gap between two concentric cylindrical rings of the CC is filled with the same refractory composite paste. The thermal conductivity (k) of the prepared composite blend slab is calculated to be about 0.047 W/m°C by performing steadystate thermal conductivity test, as suggested by BIS-IS 9489 [17]. Due care is taken to ensure the total absence of any bypass channels due to the faulty lining of the thermal composite insulation material in the gasification and combustion air paths. A blower of the capacity 12 V DC is fitted below the combustion chamber of the cookstove. It tends to force the ambient air upwards along the way through the side of the CC; gasification and combustion ducts of diameter 4 and 3 mm provide the needed gasification and combustion air.

In the advanced micro-gasifier cookstove-based ATEG system, the exterior surface of the CC is in connection with the hot side junction of the GATEG. Hence, the waste heat ejected or lost is effectively used by the ATEG for the generation of electric power. The remaining heat energy available at the cold side junction of ATEG is exploited for preheating the secondary combustion air. The primary heat generated by the advanced micro-gasifier system is used for cooking food on the stove. This combined cogeneration cookstove system can deliver both electric power to drive fan/blower (also lighting, micro-charger applications) and cooking applications in rural areas from biomass energy. The graphical illustration of the combined biomass advanced micro-gasifier cookstove with ATEG system is shown in Figure 2(a and b).
