PV water heater with adaptive control

Abstract

A photovoltaic water heater includes a tank containing water and a heater element, a solar module, and a control circuit coupling the solar module to the heater element. One or more transducers in the system produce signals indicative of water usage. A microprocessor is programmed to produce a model of water usage from the signals and cause the heater element to heat water in accordance with the model.

Description

FIELD OF THE INVENTION[0001]This invention relates to solar powered water heaters and, in particular, to a water heater powered by electricity from a photovoltaic solar panel and controlled by a system that adapts to the consumption patterns of the user.BACKGROUND OF THE INVENTION[0002]The number of solar water heaters in use is less than one percent of the total number of water heaters. This is due to problems of durability, difficulty of installation, weight, and relatively high initial cost. Durability includes problems with freezing, leakage, pump failure, and hard (mineral bearing) water. Installation has often proved difficult, requiring roof penetrations for the plumbing that transports water to and from solar collectors (arrays of pipes containing water that is heated by the sun).[0003]U.S. Pat. No. 5,293,447 (Fanney et al.) discloses a water heating system intended to avoid the problems associated with solar thermal water heaters. Photovoltaic modules generate direct curren...

AI Technical Summary

Benefits of technology

[0011]Another object of the invention is to improve the efficiency of known PV water heaters.

Problems solved by technology

This is due to problems of durability, difficulty of installation, weight, and relatively high initial cost.

Durability includes problems with freezing, leakage, pump failure, and hard (mineral bearing) water.

Installation has often proved difficult, requiring roof penetrations for the plumbing that transports water to and from solar collectors (arrays of pipes containing water that is heated by the sun).

If the hot water in a water heater is not used for extended periods of time and is maintained at a set temperature, stand-by losses account for substantially all the energy consumed by the appliance.

A problem with most dual tank systems is that one cannot tell whether the hot water being drawn was heated in the solar preheat tank or in the conventional water heater.

If a dual tank system is idle for extended periods of time, then it can experience the same standby losses as a conventional water heater alone.

If the losses occur overnight and if peak usage is in the early morning hours, it is possible that a properly operating and otherwise efficiently designed two tank system will actually not provide any appreciable energy savings.

Thus, such timers are not very energy efficient because they generally require a water heating system to operate for long periods during the day when no hot water is needed, resulting in unnecessary energy consumption due to standby losses.

As with any timer, efficiency depends upon the user accurately estimating periods of use and the estimates may not be accurate.

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