PERGAMON Renewable Energy 16 (1999) 652-655 zyxwvutsrqponmlkjihgfedcbaZYXWV PERFORMANCE ENHANCEMENT OF AN INTEGRATED COLLECTOR STORAGE HOT WATER SYSTEM Soteris .A Kalogirou Higher Technical Institute. Department of Mechanical Engineering. P 0. Box 423. Nicosia. Cyprus ABSI’RACT !ntegrated collector storage (ICS) systems offer a solution to reduce the height of the conventional flat-plate rhermosiphon type collectors The initial system developed had an aperture area of i.77 m*, a receiver diameter of 200 mm. a concentration ratio of 1.47 and total water storage volume of 65 litres The main dlsadvanta!e of the ICS systems comes from their design, i.e, because the collector absorber is also the storage cyhnder it is not possible to insulate it properly and therefore there are significant losses during the night. The main cause of these losses is the convection currents created during the night, circulating around the top glass cover Another disadvantage of the system is its draw-off characteristics. Because the water cylinder/absorber is horizontal there is very little stratification of the water in the cylinder. It is suggested that a primary 1 IO mm diameter cylinder is introduced at the space between the main cylinder and the glass The cold water is introduced directly to the primary cylinder. which feeds the main cylinder. With this modification the convection currents are drastically reduced due to the obstruction created by the primary vessel, thus reduciny the night thermal losses Also as the cold water is introduced first to the primary cylinder there is no direct mixing of the two streams thus greatly improving the system draw-off characteristics. This modification creates an 8% increase in the total cost of the system, which is reasonable, if the above benefits are considered 0 1998 Elsevier Science Ltd. All rights reserved. KEYWORDS Integrated collector storage system, hot water production. convection suppression INTRODI!CTION Low temperature water heating is usually satisfied by flat-plate thermosiphon solar collectors The development of simpler and cheaper solar energy devices will help in the spread of solar energy as a means of producing hot water. The main disadvantage of the flat-plate collectors is that they are comparatively tall units and this makes them not very attractive aesthetically. In Cyprus, as a result of intermitted water supply, a cold water storage tank is installed on top of the solar collector, supplying both the hot water cylinder and the cold water needs of the house, thus making the collector unit taller and even less attractive. The main disadvantage of the ICS systems is the high thermal losses from the storage tank to the surroundings since most of the surface area of the storage tank cannot be thermally insulated as it is 0960-1481/99/$-see front matter @ 1998 Elsevier Science Ltd. All rights reserved. PII: SO960-1481(98)00245-6