During the summer, the regional hospital in Sundsvall in central Sweden requires 1000 MW h of cooling with a maximum cooling power 1500 kW. From the summer of 2000, seasonally stored snow will be utilised to meet the cooling demand. A storage area of 140×60 m with a capacity for 60,000 m3 (40,000 tons) of snow was constructed in 1999. Initially, about half of this volume will be stored. The storage consists of a shallow pit made of watertight asphalt. A layer of wood chips covering the snow reduces the natural melting to 20–30% of the total volume. Meltwater from the snow storage is pumped to the hospital. After cooling the hospital, the heated meltwater is re-circulated to the snow storage. When all the snow has melted, the wood chips will be burnt in a local heating plant. Luleå University of Technology is responsible for the scientific evaluation of the project. This paper describes the construction and the simulated operation of the snow storage system.
Due to the growing population and scarcity of fresh water it is increasingly important to produce potable water by desalination of saline water. However, desalination requires energy and in a sustainable world it has to be based on renewable energy. Condensation irrigation (CI) is a method that combines desalination and irrigation. In such systems solar energy could be used to provide needed energy. By letting air flow over the water surface in a solar still with saline or polluted water, the air is humidified. The vapor-saturated airflow is then lead into buried pipes, where the air gradually cools and the water precipitates along the pipe surface. In current field study perforated PVC pipes were used i.e. the condensed water left the pipe through its walls and irrigated the surrounding soil. In PVC pipes without perforations the produced water was collected at the pipe outlet. A fan was used to force the air through the 25 m pipes of the CI system. The resulting amount of produced water per 8 hours for drinking water and irrigation was 4.0 and 6.0 l, respectively.
Condensation irrigation (CI) combines desalination with subsurface irrigation. Here, solar stills are used to heat and humidity air, which is condensed in underground drainage pipes to irrigate the soil, directly in the root zone. This article describes and evaluates a CI field test at Shahid Chamran University of Ahvaz in Iran. The objective was to gain a deeper understanding of the CI system in the production of drinking and irrigation water and to do a detailed assessment of heat and moisture transfer in the soil. Perforated and unperforated PVC pipes were used in two separate experiments while airflow properties, soil temperature and humidity, and ambient air temperature were monitored. The system produced 6 kg of irrigation water during eight hours, in the 25 m long pipe. When using an unperforated pipe, 4 kg of freshwater was collected at the pipe ending after eight hours of operation. The preliminary economic analysis of irrigation system indicates a payback time of less than 6 years.