Integral Collector Storage

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Integral collector storage (ICS) solar hot water systems are the cheapest, simplest installations. Consequently, they have more limitations than other, more robust setups but are a lot easier to set up and maintain. They are open, passive systems.

ICS systems only work in climates where there are no freezes, so they are a great choice for people living in the extreme southern USA or in tropical climates. Freezing weather can catastrophically affect an ICS installation by causing burst damage to pipes and the tank.

The only exception to the "no freeze" rule is if the solar thermal system is drained in cold weather and used only in warm or hot seasons, such as in vacation homes or on recreational facilities like summer camps and parks.

Some people are tempted to install an ICS in areas where freezes are rare, but do occur. They find the low cost too attractive to pass up, so they tell themselves that they'll simply drain the system if freezing weather is forecast and everything will be fine.

In theory, this is true... and, in fact, ICS systems are fairly resistant to a short, minor freeze. The water in the tank retains a great deal of latent heat and will take a long time to freeze enough to burst the sides (unless the temperature drops a long way below zero). It's the pipes that are the main concern: an insulated, standard ¾-inch copper pipe at 29°F (-1.5°C) will freeze in only five hours!

Of course, in the real world, the weather does unexpected things and people who take the risk are likely to find themselves with a bill for a complete refit, in addition to replacing everything damaged by escaping water. Play safe: even the most expensive solar thermal installation pays for itself over time.

ICS systems can also deal with all but the hardest water supplies. They cope very well with soft and normal levels of hard water because they frequently use very wide waterways and rarely heat to the extreme temperatures experienced in other systems.

The biggest problem with ICS installations is their weight. Because the water tank is also the collector, which is usually mounted on the roof, you need to check that your building can support such a massive load. Water weighs over 8lbs per gallon (1kg per liter), so a relatively small 30-gallon tank can weight around 500lbs when full (around 225kg).

Most homes can handle such a weight, but you don't want to find your water tank downstairs in the kitchen one day, so get it checked by a professional!

Because ICS systems heat the water supply directly, they work best when hot water is used at the end of the day, after the tank has gathered as much of the sun's radiation as possible. Therefore, they may require a change in hot water usage habits to get the best return on investment.