Batch Solar Water Heater
an Integral Collector Storage system

A batch solar water heater system is a clever way to combine the functions of heating water and storing water into one single integral system that has only one component.
In a nut shell, the storage tank is eliminated and the solar collector also stores the hot water.
This is the simplest and cheapest approach to water heating, however it is limited to sunny regions and to smaller families.
A primitive version of the batch solar system was commercially introduced to the US market in 1891 by Clarence Kemp, an entrepreneur in the areas of plumbing and heating. His product was called Climax and he sold a few hundreds system in California. The price tag was $15, the system suffered from the well known drawbacks of batch solar water heater systems as detailed bellow

The Integral Collector Storage Construction

The batch solar collector is simple, an inlet pipe comes from the cold water main supply and the outlet is connected to the hot water pipe (almost always through the conventional hot water heater). When hot water is drawn from the water heater by opening a hot water faucet, "new" hot water is supplied from the batch solar collector. Cold water flows in and refill the Integral Collector Storage

The integral collector storage solar water heating system consists of a series of long thick winded tubes mounted in a sealed rectangular box. The tubes are painted dark to absorb the sun radiation. A top glass plate prevents the infrared heat radiation to escape the box (greenhouse effect)
The water capacity is typically limited to 30 to 50 gallons, a storage capacity that fits the needs of smaller families.

Where and to Whom does the integral system fit?

This simple integral collector storage solar water heating system is typically used as:

  • a solar pre-heater to an existing electric or gas water heater (to save on fuel consumption)

  • Or used as a primary water heater in sunny regions for small family units

This simple solar water heating system can be used only in regions where the temperature is always above freezing (32 degrees) point. On the first instant of freezing, the water pipes will crack and the system is doomed.

The system main advantages are lowesr cost, simple construction, simple installation and very low maintenance efforts

Disadvantages of the batch solar water heater

One disadvantage is that the heating the water stored in the collector may take a few hours and the hot water should be used in a relatively short time after sunset, otherwise the temperature of the water might drop due to heat loss

Another disadvantage is the weight. Not like systems where the tank and collectors are separate and can be installed in different locations, when the integral system is filled with water - not every roof can hold the weight.


A small 30 gallons system can cost around $2,000 including installation.

More ICS related reading

What are solar hot water tanks: solar hot water tank

What are solar hot water collectors: solar hot water collectors

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