Analytical model for electric back-up power estimation of solar box type cookers

The major hindrance in popularization of box type solar cookers (SBCs) is cooking incapability of these appliances in low availability of sun light and in night. This paper introduces a new parameter “required electric back-up power (Prb)” for SBCs to remove this limitation. An analytical model is presented here to derive Prb for SBCs under different weather and cooking time conditions. To validate proposed model, a Solar cum Electric Cooker (SEC) has been fabricated as per Prb value estimated via analytical model. SEC has been tested under different conditions. Experimental results are in support to the analytical approach. SEC is capable for cooking of 1.2 kg food load under indoor and outdoor. For outdoor, cooking time on sunny day without back-up is recorded between 1.5 and 2.5 h. The cooking time on scattered cloudy day with back-up is found to be 100 min (back-up is 0.12 kWh that is 82% less than the conventional electric heater). For indoor, cooking time is found to be 85 min (with 0.23 kWh electric back-up). Paper also reveals that electric back-up in SBC also reduces its payback period and increases its net present value (NPV) in respect to different cooking fuels.