PV water heating system

Abstract

A system for heating water includes a first tank, a solar panel, a control circuit, and a second tank for receiving water from the first tank. There is a first resistive heating element in the first tank and a second resistive heating element in the second tank. The control circuit couples power from the solar panel to the second resistive heating element unless the water in the second tank is at a preset maximum temperature, then the control circuit couples power to the first resistive heating element. If the water in the second tank is below a preset maximum temperature and above a preset minimum temperature, then the control circuit couples power from the solar panel to both the first heater element and the second heater element. If the temperature of the water in the second tank is below a preset minimum temperature, then the control circuit turns on conventional heating means in the second tank. Water is withdrawn from the second tank for use.

Description

FIELD OF THE INVENTION[0001]This invention relates to water heaters and, in particular, to a water heating system powered by electricity from a photovoltaic (PV) solar panel.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. Of these, the vast majority are solar thermal water heaters. That is, solar energy directly heats water in a collector containing a plurality of pipes containing water. It is also known to convert solar energy to electricity and use the electricity to heat the water. This is PV water heating.[0003]Solar thermal water heaters are not widely used because of 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 collect...

AI Technical Summary

Benefits of technology

[0013]Another object of the invention is to improv...

Problems solved by technology

Solar thermal water heaters are not widely used because of 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).

Basically, the demand for hot water and the demand for solar energy do not match.

A demand for large amounts of hot water, especially around sunrise, can significantly outstrip supply.

Increasing the size of the tank does not overcome the problem of limiting water temperature and introduces its own problem of having a larger mass of water to heat.

Except for special cases where usage is limited or in hot climates where the cold water is already quite warm, PV solar systems are severely tested to provide enough energy at the right time to be the sole source of energy for heating water.

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