Examples
ATTENTION: You are using a browser that is out of date and not supported. Please note that the page may not display properly. It is recommended that you upgrade your browser to its most recent version.
TEAM Projects - International Initiatives
Multi-country solar drying
A promising application for active solar heating is the commercial crop drying operations (e.g. coffee, tea, and rice) where fossil fuels are the prominent energy source. It has been estimated that the potential energy that could be displaced using solar in this market is between 216 PJ and 770 PJ annually.
TEAM provided financial support to Conserval Engineering to demonstrate its Solarwall product's effectiveness to be used by medium- to large-scale commercial crop drying operations to dry a variety of crops. Solarwall is a high-tech building cladding system that captures energy from the sun and converts it into a current of warm air. The warm air produced by the Solarwall product will not burn or harm many delicate foods, which may happen with steam heated or fossil-fuel heated air. Additionally, the solar technology can be upwards of 40% more efficient and 25% cheaper than other solar heating technologies, allowing it to compete with traditional fossil-fuel energy sources.
The two and a half year project concentrated on displacing fuel-fired dryers for crops like tea, coffee, fruit, spices, rice, and nuts that are dried at temperatures less than 50ºC. Conserval targeted existing commercial drying operations because they can be retrofitted with Solarwall panels on nearby roofs and walls, and the panels then connected to the intake of the drier fans.1 In new facilities, the drying chambers can be designed for solar heating with the entire roof and walls of the chambers, as well as production buildings, covered with the Solarwall panels.
The projects in Panama, India, China, and Costa Rica served to demonstrate the viability of this solar technology for agricultural drying applications worldwide. Conserval saw an opportunity to penetrate the largely undeveloped market for solar energy use in these industries and exploit it. This successful project helped Conserval overcome a number of barriers to solar crop drying which included 1) lack of awareness, 2) lack of technical information, and 3) lack of local practical experience.
Coffee Drying Costa Rica
http://www.iea-shc.org/task29/coffee_drying_costa_rica.htm
Early in the year an agreement to install a solar system on an existing coffee drying facility was reached with the cooperative Coopeldos in the western mountains of Costa Rica. The coffee beans go through a primary drying phase (60% - 35% moisture content) in the vertical dryers and then a secondary drying (30% - 12% moisture content) in a series of guardiolas, rotating horizontal drums. Based on the results of a feasibility study, 690 m2 of Solarwall collector were installed on the roof and the design air flow calculated to be 28 l/s/m2. The collector efficiency was predicted to be 59% and the total system was predicted to deliver 1,993 gJ per year. This performance will save over 300 tonnes of wood per year.
The system was monitored by Task experts during the 2004/05 drying season. Early analysis indicated that there was significant air leakage in the furnace and ductwork. Remedial measures were taken but there were still certain openings which were manually operated to control air flow. It was recommended that automatic equipment be installed to increase efficiency but this was not implemented during the time frame of the Task.
Due to the air leakage and the plant operating below full capacity during periods in the season, the air flow through the collectors was much less than anticipated. The collectors, however, did perform as predicted for the reduced air flow. Over the season, the system displaced over 440 gJ of energy resulting in a saving of over 22,700 kg of wood.
Solar collectors on roof of drying facility. Duct from solar collector entering furnace.
Metal “hats” hold perforated solar panel of roof and form the air space from which the solar heated air is drawn.
Modified: 06-13-2008
