Simple design to make solar water heating affordable and compatible with conventional water heaters

Abstract

The objective of this invention is to make solar water heating affordable and compatible with conventional gas or electric water heaters. Solar energy is clean and renewable. However, solar water heating has not been in wide use in the US mainly due to two reasons: first, the cost of a current solar water heater is generally too expensive for an average household; second, a typical solar water heater uses ethylene glycerol as a heat transfer fluid to prevent freezing and needs additional space for an extra exchange tank. Our design includes evacuated tube collector panels for efficient collection of solar energy, utilizes two unique three-way adaptors to connect solar collector panels to a conventional water heater for storing solar hot water, and is operational even in freezing temperature. These improvements eliminate the need for an extra exchange tank and significantly reduce the cost of a solar water heater.

Description

Solar water heating is an efficient way to utilize energy from the Sun and is beneficial to the environment. However, solar water heating is not in wide use in the US because commercially available systems of solar water heating are too complicated and too expensive for ordinary people. The present invention relates to a simple design to make solar water heating affordable and compatible with conventional gas or electric water heaters.

This device is comprised of the following components:

• • A. Evacuated solar collector panels (collect solar energy to heat water passing through the collector panels)
  • B. Temperature sensors (detect the temperature at a certain location within the system).
  • C. Controller (receives information from the temperature sensors and decides whether to turn on/off the circulation pump).
  • D. Circulation pump (circulates water within the system).
  • E. Three-way adaptors (connect solar collector panels to the conventional water heater and the drain).
  • F. Expansion tank (relieves water pressure within the system).
  • G. Pressure/temperature relief valves (reduce high water pressure or temperature due to over-heating within the system).
  • H. Check valves (prevent back flow of water within the system).

After successful assembly and connection to the conventional water heater, these components work together in the following ways:

• • A. Turn the temperature setting on the existing gas or electric water heater to vacation or warm (This will depend on how much solar energy is available at a given location).
  • B. When the temperature at Sensor T1 (1a) near the solar collector panels is higher than temperature at Sensor T2 (1b) near the tank by a pre-set value (usually 20° C.) during the day, the Controller (2) will activate the Pump (3) to circulate hot water from the solar collector panels into the conventional water heater. Direction of the water flow is indicated by arrows in FIG. 1.
  • C. Once the temperature differential between Sensor T1 and Sensor T2 decreases to below a pre-set value (usually 10° C.), the Controller (2) will turn off the pump (3).
  • D. When hot water is drawn from the water heater at night, cold water flows into the tank as indicated by arrows in FIG. 2.
  • E. In the winter, outside temperature may fall below freezing at night.
  • When the pipeline temperature is below a pre-set point (usually 2° C.) near the collector panels at Sensor T3 (1c), the Controller (2) will activate the Pump (3) to re-circulate hot water collected during the day. Once the temperature reaches another pre-set value (usually 8° C.) at Sensor T3, the Controller (2) will turn off the Pump (3). Since the pipelines are well insulated within the system, minimal amount of circulation is able to prevent freezing.
  • F. Power supply to the system can be backed up by a battery bank equipped with an inverter to convert direct current to 110 volt alternating current in case of a power grid failure.
  • G. In extremely cold and cloudy winter when it is not sufficient for solar collector panels to heat the water, connection to the solar collector panels can also be cut off. This is done by un-plugging the power to the Controller (2), turning off the Ball Valves (4), and draining the system through the Sillcock Valves (5) as shown in FIG. 3.
  • H. The Expansion Tank (6) and the Pressure/temperature Relief Valve (7) are installed as precaution measures to protect the system from extreme water pressure and temperature due to over-heating.
  • I. The Check Valves (8) prevent hot water in the conventional water heater from escaping towards the solar collector panels in cold weather or at night.

The design may be used for solar heating of swimming pools and other sources of hot water with minimal modifications.

The design may not need all three temperature sensors in locations where freezing never occurs. The evacuated solar collector panels are modular in nature, two or more panels can be connected in tandem to increase the amount of solar energy collection.

DRAWING DESCRIPTIONS

FIG. 1 is a schematic diagram of the invention for collecting solar hot water during the day.

FIG. 2 is a schematic diagram of the invention for using solar hot water at night.

FIG. 3 is a diagram of the unique three-way adaptor.

Claims

1. The way this invention works is that the design includes evacuated tube collector panels for efficient collection of solar energy, utilizes conventional gas or electric water heater as the tank for storing hot water directly from the solar collector panels. When there is enough sunlight, hot water will be provided solely by the solar collector panels and stored in the conventional water heater. When there is not enough sunlight, water heating can also be supplemented by gas or electric heating in the conventional water heater.

2. Unique three-way adaptors that connect the solar collector panels to the conventional water heater through Ball valves and to the drain through Sillcock valves.