Design and Testing of a Plastic Bubble-Film Covered Shallow Solar Pond

A shallow solar pond was designed from inexpensive plastic materials and tested during the summer months. The bag containing the water consisted of a black polyethylene bottom (1.5 mil) covered with a clear polyvinylchloride top (4 mil) and a layer of polyethylene bubble-film on the top of the PVC bag. The bubble-film material is of the type commonly used for protection of breakable goods during shipment. The bubble-film material provided an inexpensive and effective upper glazing for the bag assembly. The bag was insulated from bottom losses by placing it on a 2.22-cm (0.875-in.)-thick layer of polystyrene foam. Tests were performed during May, June, and July 1980. These tests were performed by batch-filling the bag in the morning with a measured quantity of water and measuring the temperature rise of the water during the day. Measurement of water quantity, initial temperature, final temperature, and total incident radiation allowed for calculation of a daily efficiency for the pond. Tests were made for water depths of 5.2 and 10.2 cm (2.05 and 4 in.). Maximum daily efficiencies of up to 63 percent were recorded during the testing. Daily efficiency was determined by dividing the total daily heat collection of the pond by the total radiation incident on the pond for the day. Maximum water temperature of 67°C (152°F) was reached during the testing program. Temperature rise in the pond assembly was typically on the order of 33–39°C (60–70°F) during clear days.