Solar hot water has long been the redheaded stepchild of photovoltaics.
PV panels are instantly recognized around the world as devices that provide free electricity from the sun; solar hot water, on the other hand, usually receives comments like “what the heck is that” or “does that even work”. Although the technology of solar hot water has been around longer than its sibling, it doesn’t get the respect it deserves.
This technology was around in Rome when Caesar was dating Cleopatra. In ancient times, the Romans were heating rooms by running water heated by the sun through copper pipes in the walls. Even the public baths and steam rooms were built to utilize passive solar.
Solar hot water has come a long way. The traditional collector was a box with a serpentine of copper pipe inside known as a flat plate collector. Although it worked very well, it was limited by the intensity of energy it could produce, thus limiting its range of uses. The new look of this proven technology is in the form of evacuated tubes (ET). Even under cloudy skies ET collectors will provide substantial assistance to the hot water needs of a dwelling. The future will be in the ET’s ability to generate higher temperatures than its counterpart, the flat plate. With the capacity to produce more BTUs, the ET opens itself up to a wider range of industrial and residential applications.
Some of the potentials for these ET systems include solar air conditioning, thermal dehumidification, space heating and industrial food processing applications. The coolest of these possible applications is solar air conditioning. Combining an absorption chiller with an evacuated tube system seems to make for the perfect year-round system. In the hot days of summer the system supplements the chiller to provide cooling. In the winter it aids the boiler to offset heating cost in the home. It seems as though the capabilities of the evacuated tubes open up and wide array of possibilities.