The increase of micro and nano devices has led to the miniaturization and multi-functionalisation of micro-mechanical, communication, imaging, sensing, chemical analytical and biomedical devices. The devices so mentioned above need power sources that are portable, have short charging time, longevity, high energy density and are environmentally friendly. Chemical batteries hitherto used to be the major power source for these devices but have a drawback of having low energy density. The energy density of the most improved lithium-ion battery was in the region of 0.2 kWh/kg. Another problem of chemical batteries is the mode of disposal, which pose major environmental concern. They also have long charging time. Combustion based power generators have been proposed as alternatives to the chemical batteries by taking advantage of the high energy density of hydrogen and hydrocarbon fuels. These combustion based micro-power generators have energy densities of about 12 kWh/kg, which is way above that of chemical batteries. The major concern is the conversion of the vast chemical fuels into electricity in an efficient manner and in the millimeter scale.
　　The Micro-Thermophotovoltaic (MTPV) as an example of a power generating machine which uses thermal energy to heat the outer surface of the micro-combustor and other components such as the optical element and the TPV cells. The thermal energy is obtained from the combustion of hydrocarbon fuels in the combustor and as a result, electricity can be generated when photons with high energy reaches the TPV cells. The MTPV as compared to other power generating devices have the advantages of having no moving parts and easy to assemble. By modifying the structure of a previous planar combustion system, a novel porous media based MTPV system is proposed in this work. Methodical researches have been carried out through experimental and numerical analysis, and some achievements with scientific significance and values have been obtained as follows:
　　1. The links of energy conversion was investigated for the planar MTPV system. These include heat transfer and combustion coupling process, flow, radiation process of the combustor’s outer wall and the photoelectric transformation process. Based on the non-uniformity of temperature distribution of the walls of the combustor, a three-dimensional energy transition computational model was constructed through combining the software of Fluent and Matlab which described the whole transition process of chemical energy to electricity. The model was validated with experimental results.
　　2. Porous media combustor was designed with the dimensions;length–15 mm, width–10 mm, height–1 mm and wall thickness of 0.5 mm. The influence of key parameters on porous media combustion were numerically investigated and the results showed reduction in combustion efficiency when inlet velocity increased. The average wall temperature decreased with increase in the solid matrix thermal conductivity.
　　3. Using a micro combustor with micro pin-fin arrays inserted, it was observed the fins widened the region of combustion and extended the blow-off limit in the combustor. The fins exerted great influence on combustion as flow rate increased and thus improved the temperature distribution of the wall. The combustor with fins possessed higher heat flux in comparison with combustor without fins. There was combustion stability at inlet velocity of 4 m/s making the micro pin-fin array configuration ideal for MTPV application.
　　4. Influencing factors on the performance of the MTPV system were investigated and it came up that, increment in cell temperature decreased the forbidden band whiles the cut-off wavelength increased. Variations in temperature of the TPV cell caused the output power to decline by 35%. For any 10 K increase in cell temperature, the cell efficiency and power output reduced by 7%and 0.14 W respectively.
　　5. The effects of changes to key parameters of the system were investigated. The distance between the outside wall of combustor and the TPV cell was fixed at 1 mm. Variation in distance from 1 -6 mm between the outside wall of the combustor and the TPV cell caused a reduction of 13.75% and 1.4% in radiation heat transfer efficiency and TPV cell conversion efficiency respectively. An increase in the mixture flow rate from 300 mL/min to 1800 mL/min caused an increase in the radiation heat transfer efficiency, TPV cell conversion efficiency and the total system efficiency. As the flow rate increased, the system’s power output also increased. At 600 mL/min, the output power was 560 mW but rose to 3.2 W at the flow rate of 1800 mL/min. The cooling load of the system showed a linear growth as the flow rate increased. At 1800 mL/min the cooling load of the system was 12.4 W which is three times the cooling load at 900 mL/min.
　　6. The entire PMC arrangement recorded power output of 2.7 W and power density of 0.72 Wcm-2. In the case of the combustor with micro pin-fin arrays, the output power recorded was 1.94 W and the power density was 0.54 Wcm-2.
　　7. The MTPV system was optimized and incorporating frequency selective filter and emitter into the system witnessed an enhancement in the system output power and efficiency.