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Performance, Energy Consumption and Energetic Efficiency Analysis of 25 Solar Sludge Dryers

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By the end of the year 2003 at least 48 solar sludge-drying plants will be operated worldwide. About 65 % of these plants are located in Germany, Austria and Switzerland, with others in France, the USA, Italy and Australia. An analysis of 25 of the European solar plants, ranging from a capacity of 1 000 to 300 000 inhabitant equivalent showed, that between 0,6 and 1 ton of water could be evaporated per m2 of drying area. With a backup heating system this value increased to up to 3,5 tons of water per m2. In solar dryers for sludge which was not mechanically dewatered the performance was generally higher. Without a backup heating system 2 to 3 tons of water were evaporated per m2 and year. The higher performance is due to drainage of water by a drainage floor, which is integrated in this type of dryer. The costs of the solar drying process were mainly associated with the cost of the investment. The operation cost played a noticeably less important role with only 10 to 25 % of the total costs. Depending on the process, the type of construction, the extent of mechanization and the size of the plant, the cost for drying mechanically dewatered sludge was in a range between 30 and 60 per ton of evaporated water under German, Austrian and Swiss conditions. This is significantly lower than the usual costs for conventional drying processes in these countries. Depending on local climate and construction costs this value is lower for solar dryers in warmer regions of Australia and the USA.

Document Type: Research Article


Publication date: January 1, 2003

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