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ICS stands for Integral Collector Storage. In an ICS unit, the solar hot-water-storage tank is the solar absorber. The tank (or tanks) is mounted in an insulated box with glazing on one side and is painted black or coated with a selective surface. The sun shines through the glazing and hits the black tank, warming the water inside the tank. Some models feature a single large tank (30 to 50 gallons) while others feature a number of metal tubes plumbed in series (30- to 50-gallon total capacity). The single tanks are typically made of steel, and the tubes are typically made of copper. These collectors weight 275 to 450 pounds when full, so wherever they are mounted, the structure has to be strong enough to carry this significant weight.

Figure 3.3: Tank type ICS collector

Figure 3.4: Tube type ICS collector

ICS collectors are widely used around the world in climates that never experience freezing conditions. They work great, given their climatic restrictions. They are a direct type of system, as the water you use is actually heated in the collector. They do not suffer from hard-water problems nearly as much as do flooded collectors (collectors with water in them at all times) because all waterways in the collector are very large and also because the collector never gets hot enough to precipitate minerals out of solution, and their simplicity makes them a very affordable choice.

ICS collectors are also used in seasonal applications such as campgrounds and summer homes, where they are used only during the warm months of the year and are drained before freezing conditions occur. Bob has sold many of these collectors with excellent results.

As mentioned above, these collectors are heavy, so if they will be mounted on a roof, make sure that roof is strong enough to hold their weight. You may have to reinforce an existing roof to make it acceptable. These collectors should always be tilted so they will properly drain.

The tube type of ICS collector will outperform the tank type because more surface area is exposed to the sun. Another advantage of the tube type is that its profile is much smaller, which affects aesthetics. On the other hand, tube type collectors cool off more quickly at night because of their larger surface area. On cool nights, the water stored in these collectors will cool off, so they lose efficiency. You can maximize this kind of system’s efficiency by using as much hot water as you can during the day and early evening hours.

Another kind of collector system often classified as an ICS system is called a thermosiphon type system. These use a flat plate or evacuated tube collector mounted directly to a storage tank that is located directly above and attached to the collector. They use a heat transfer fluid that flows through the collector or uses a heat pipe to deliver heat from the collector to the storage tank. These systems are very popular in southern Europe, Asia and areas of Australia where freezing conditions never occur. These systems do not lose heat during the evening hours as quickly as the tank type collectors do because the storage tank is better insulated.

Figure 3.5: Thermosiphon type ICS collector

All ICS systems are plumbed in series, with the backup water heater acting as a pre-heater. Very often they can provide 100 percent of the daily domestic hot water when installed in hot, sunny climates or during the summer months when the sun shines most days.