On the design, modelling and analysis of multi-shelf inclined solar cooker-cum-dryer

A novel design of multi-shelf side loading inclined solar cooker-cum-dryer (ISCCD) is designed using single reflector North Facing Booster Mirror (NFBM) to improve the performance of both cooking and drying operations particularly in winter months. Innovative parallelepiped shape vessel (PSV) is designed (having longest inclined south facing wall) to further enhance the performance of ISCCD in cooking mode. Solar radiation capture model by ISCCD is used in developed thermal model for various interactive components such as; glass covers, chamber air, absorber plate, cooking vessel and vessel water while considering the effect of NFBM and experimentally validated at Ludhiana climate (30°N latitude), India. Volume to aperture area ratio along with size of PSV is optimized in such a way that ISCCD with three-shelves is capable of cooking three times more food as compared to the conventional horizontally placed solar cooker (HPSC). Due to optimized vessel design and NFBM effect, ISCCD can be effectively used in extreme winter conditions when maximum temperature during the day hovers around 15-20 °C (on sunny days) at latitudes >30°N for both cooking as well as drying operation when conventional HPSC and dryer (generally not fitted with booster mirror) do not perform well due to lower solar radiation availability. Stagnation test (first figure of merit F1) and sensible heat test (second figure of merit F2) were also computed and compared with HPSC to ascertain the performance of ISCCD. In drying mode, ISCCD was tested for drying gooseberry (Emblica officinalis) (local name amla) under natural as well as forced convention modes with and without the effect of NFBM. The Logarithmic drying model was found to be the best fit for drying gooseberry. Techno-economic analysis showed that in cooking mode ISCCD can be used to cook at least one meal per day for a joint family of 10 persons during 280 days in a year and can recover its cost within 65 months if compared with wood burning costs besides having the advantage of being used as an efficient dryer thereby saving the cost of second gadget. In terms of savings in biomass fuel burning, ISCCD can mitigate much higher CO2 emissions as compared to conventional HPSC.