Manila (ISJ): Experts from the International Rice Research Institute (IRRI), Manila and the University of Hohenheim, Germany have developed a low-cost, state-of-the-art Solar Bubble Dryer to dry grains and prevent post-harvest losses. The dryer is suitable to dry rice, corn, coffee and other farm produces during both sunny and rainy days. The dryer is made of durable UV-resistant and water-repelling plastic material.
The commodities to be dried are enclosed in an inflatable bubble equipped with small ventilators to drive the moisture out, while keeping the bubble inflated. It is run on readily available power ? solar or grid, in both sunny and rainy days. The airflow removes water from inside the drying tunnel, where the grains are, and prevents overheating. The grain is stirred from time to time using a metal roller underneath the dryer to ensure grains dry evenly. It can dry rice grains to a moisture content level of 10-13 per cent, depending on the weather conditions. "We tried several designs when we started, not one of them was the bubble design," explained Ana Salvetierra, researcher and post graduate student from the University of Hohenheim, Stuttgart, Germany. By traditional practice of drying, the grain could germinate, crack or develop some kind of microbiological organisms and reduce the product quality. Moreover, a typical recirculating batch dryer requires at least 10 tonnes of rice for just one drying operation, whereas the solar bubble dryer has a capacity of 1 tonne, which it can dry in 1-2 days, depending on the weather. As the ventilators can be powered by photovoltaic solar panels, it is suited for farming villages that do not have access to electricity. The solar panels and battery can also be used for other purposes like lighting the house, when the dryer is not in use. It is fully collapsible and easy to transport and assemble. The Bubble Dryer is currently under evaluation in Cambodia, Myanmar, the Philippines, Vietnam and Africa. "We need to test it in different countries to optimise its design, its management, adapt it to local conditions, and minimise investment cost," said Martin Gummert, head of the IRRI Postharvest Unit. "The dryer is still a work-in-progress, but it has numerous advantages over a mechanical dryer for small farmers. It is affordable, easy to use, and is ideal for rural areas without a power grid or source of electricity."