## 1 Introduction  
Tropical regions are famous for producing different kinds of nuts and beans, but the majority of these produces are exported to industrialized countries in perishable form without any subsequent post-harvest processing [1; 2]. The growers of developing countries are facing a challenging scenario for adding value to their agricultural products due to insufficient on-farm processing facilities and inaccessibility to the centralized electricity grid, particularly in rural and far-flung areas. According to Renewable Energy Policy Network for 21 st Century (REN21), about 16% of the global population (1.2 billion) lack access to electricity while 38% (2.7 billion) are living without clean heating facilities [3]. In the past few decades, increased annual usage of fossil fuels in agriculture sector has been trended in Asia, South and Central America, and Africa. This energy deficient scenario uplifts the overall consumption of carbon-based fuels to meet the energy needs and ultimately contribute towards environmental degradation. The importance of agricultural processing cannot be deprived in developing countries as it has set a rising association from the farm gate to the supermarket shelf nowadays. From the past decades,the restructuring of agricultural processing played an essential role in the transformation of agricultural products from perishables to value added categories [4]. Energy is very essential for every step involved in value-addition to agricultural products. Various value adding processes such as drying, roasting, pasteurizing, distillation, chemical extraction operations, curing of food products, lie in the main low to medium temperature range (60-260 \({}^{\circ}\)C) [5]. In total, one third of final global energy demand is consumed in agri-food sector, making it responsible for contributing a 35% share in global greenhouse gas (GHG) emissions [6]. Roasting is a noteworthy value adding phenomenon to various nuts and beans in agricultural processing and defined as the process of acquiring characteristics like aroma, flavor, color, and texture at a relatively high temperature [7]. Among the nuts, groundnuts (_Arachis hypogaea L_.) offer a potent source of high-quality edible oil and dietary protein and nearly one-third of its global production is utilized in the confectionery products. As a first step, the kernels of groundnut are processed thermally (roasted) in a range between 110-180 \({}^{\circ}\)C to attain desired crunchy characteristics and crispy texture, either for oil extraction or manufacturing of other value-added products [8; 9]. Traditionally, groundnuts are roasted in large iron pans or clay pots at farm and vendor scale which are being exposed to heat from bottom by burning of wood, kerosene, charcoal or gas. The kernels are placed (directly or with sand-bath) and stirred manually in the heated pans. These conventional methods of roasting are uncontrolled, inefficient, energy and time consuming and provide a very un-hygienic environment to the operators such as direct exposure to heat radiations and smoke. On an industrial scale, groundnuts are roasted either using gas-fired revolving oven or continuous or batch type roasters which offer more flexible options for precisely controlling the process conditions like temperature, time and product flow rate, ensuring a uniformly processed product [10]. However, these large scale units are economically out-of-reach for small to medium scale farming communities accompanied by the additional burden of escalating fossil fuel prices that upsurges the processing cost. Although many technological efforts have been made to facilitate the rural communities by mechanizing the roasting process [11; 12; 13], all were fossil fuels or electricity dependent. In a nutshell, there is a strong need of devising self-sufficient, economically viable, and environment friendly off-grid solutions for medium to high range temperature agricultural processing particularly in remote areas of tropical regions, i.e., solar power.