Security of Energy Supply to the Canteen

The scale of the problems that the canteen faced on a daily basis was staggering. The local culture required that freshly cooked and piping hot food be served. The main staple was cooked rice, of which we needed on average, 10 oz. per employee. About 1500 meals were served in each batch.

The rice was cooked in large electrically-heated cookers mounted on trunnions. Each batch had to be cooked in 20 minutes, and the vessel cleaned and ready for the next batch in 5-10 minutes. The water temperature had to be raised from the ambient 60-70°F to 212°F, and this could take 10-12 minutes. The canteen manager was visibly under stress. If there was any glitch, food could not be served—to at least 1500 and possibly up to 4500 waiting people!

The electrical cooking system was excellent, but consumed significant amounts of energy. Because sunshine was available in plenty, we planned to install solar water heater panels on the concrete roof of the canteen. Each panel would be about 120 square feet in area. With four of them in series, even on a cloudy day we could get the water to 150-160°F in about 10 minutes. We decided to install two banks of four panels each along with an insulated hot water storage tank. This allowed us to supply hot water rapidly, and stored enough water for the second and third shifts as well. A structural de?sign check of the roof confirmed that it was suitable for the additional roof loads.

The project costs were in the medium range. Delivery of the solar panels would take 6-8 months, so we phased the project into the second year. The primary purpose was to get rapid supplies of fairly hot water to the cooking vessels, so that cycle time could be reduced. This would give recovery time to the canteen staff in the event of a power supply glitch. The bonus was that electrical energy savings made it economical as well. The project was justified as a welfare item.

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