Batch Solar water heaters

Batch solar water heaters (or ICS - Integrated Collector Storage - solar water heaters) are losing share to thermosyphon, drainback, active solar and glycol solar and other closed loop solar solutions.

Batch solar heaters combines a solar panel and a storage tank into one single unit (Integrated Collector Storage means it).

In its most simple version, a batch solar water heater is just a water tank within a glazed box, placed in a sun-facing surface (the south in the northern hemisphere, or the north in the southern hemisphere...). Batch solar water heater scheme

Image: EERE

Batch collectors and systems

Typical batch solar water heaters do not involve pumps or a separated storage tank, anti-freezing, heat exchangers, valves, sensors...

A batch panel is typically very similar to a flat-plate collector, with a greater depth (of at least 6 inches/15 cm). The water is heated directly in the collector (they are open-loop systems) and no pump is used to move the water (they are passive systems).

Its working principle is also very basic: when the homeowner requires hot water, that hot water comes from the top of the storage tank, while the cold water enters from the very bottom.

Advantages

Batch solar water heaters are a cheap option with almost no maintenance. They are a reliable technology in appropriate climate conditions.

Disadvantages

But batch solar water heaters lack versatility. Unless in favorable weather conditions family showers should be scheduled at different times of the day.

Heating the whole tank with hot water may take some hours, and the water should be used not long after the sun sets to avoid huge losses in temperature.

Batch technology isn't adequate in freezing and very hot climates. The efficiency of these collectors is very low in adverse climate conditions, and snow or very hot temperatures can damage the collector. To avoid it, the system has to be drained manually.

Batch systems weight is also a disadvantage. You can install a system of multiple panels to get a larger capacity (with the outlet of the first panel becoming the inlet of the following, to get higher temperatures). But that raises a problem: a batch solar heater system can easily weigh 200 pounds/90Kgs dry and 350-500 pounds (160-230 Kgs) filled, which obviously demands a sufficiently strong roof.

If you plan to install a batch solar collector system, pay attention to it. Call a roofing professional to assess and eventually reinforce your roof.

Uses and climate

Freezing is a major problem with batch solar water heaters. Since these systems usually have manual drain valves, you should drain the water in freezing conditions, to avoid damages.

Too hot conditions can also damage the system. If the water gets too hot, the collector can burst or get damaged, and you should also use the tempering valve to prevent overheated water from entering into your heating system.

Prices and capacity of batch systems

Batch solar water heater systems are simple and relatively cheap, but once the big players are out of the game, prices can be higher than expected.

Smaller units (3’ x 8’ units, holding 30 gallons of water/115 liters) may cost you $1,000 - $2,000, plus the cost of installation, pipes and hardware.