Solar heating systems with integrated circulator control

Abstract

Solar heating systems are provided which transfer heat from a solar thermal energy source to a hot water heating system, e.g., a domestic hot water system or a radiant heating loop. These systems utilize a circulator pump with an integrated controller which provides solar differential temperature control, optimizing functioning of the solar heating system.

Description

TECHNICAL FIELD

This invention relates to solar heating systems.

BACKGROUND

Solar energy, for example energy collected in a roof-mounted solar collector, may be used as a heat source for various types of household or industrial heating, for example radiant heating systems and domestic hot water heating. A radiant heating system is composed of tubing embedded in flooring, walls, or ceilings of the area to be heated, with heated water being pumped through this tubing to raise the temperature of the surface (thermal mass). A typical domestic hot water system includes a domestic hot water heater which supplies potable hot water to a household.

Solar thermal energy is a renewable energy source, and thus utilization of solar thermal energy in heating systems is highly desirable from an environmental perspective. As concern regarding global warming and other undesirable environmental affects of fossil fuels increases, it will become ever more important to provide viable alternative energy sources.

SUMMARY

In one aspect, the present invention features a method of supplying heat to a solar heating system, including: (a) heating liquid using a solar heat source; (b) delivering the heated liquid to a storage reservoir; (c) circulating the heated liquid through the storage reservoir and back to the solar heating unit using a circulator pump; (e) determining the temperature differential between the temperature of the liquid exiting the solar heating unit and the temperature of the liquid after it has exited the storage reservoir; and (f) controlling circulation of the liquid based on the temperature differential using a controller. Advantageously, the controller is integrated with the circulator pump, allowing easy repair of the system and replacement of the pump and controller.

For example, the circulator pump and controller may be integrated in a single, unitary fixture.

In some implementations, the method includes one or more of the following features. The method further includes turning off operation of the pump when the temperature differential exceeds a predetermined setpoint. The method further includes turning off operation of the pump when the temperature in the reservoir exceeds a predetermined maximum. The method further includes turning off operation of the pump when the temperature at the exit of the solar heat source falls below a predetermined minimum. The method further includes activating a heat dump pump when the predetermined maximum is exceeded, and diverting liquid from the solar heat source to a heat dump. The system further includes a supplemental heat source, and the method further comprises activating a supplemental pump when the temperature at the exit of the solar heat source falls below a predetermined minimum, to deliver heated liquid through a supplemental loop from the supplemental heat source to the reservoir.

In another aspect, the invention features a solar heating system comprising: (a) a solar heat source configured to heat a fluid; (b) a reservoir for storage of the heated fluid; (c) a path for circulation of fluid from the solar heat source to the reservoir and back to the solar heat source; (d) a pump configured to circulate fluid through the path; and (e) a controller, integrated with the pump, configured to control the operation of the pump in response to variations in the temperature of the liquid in the storage reservoir.

The system may further include a tank sensor configured to measure the temperature of liquid exiting the storage reservoir and a source sensor configured to measure the temperature of liquid exiting the solar heat source. The controller may be configured to calculate the temperature differential between the temperature measured by the tank sensor and the temperature measured by the collector sensor.

In some cases, the system may include a supplemental heat source, and a supplemental pump configured to deliver heated liquid from the supplemental heat source to the storage reservoir, and the controller may be configured to control operation of the supplemental pump.

The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.

DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic of an arrangement for heating domestic hot water using heat from a solar heat source.

FIG. 2 is a schematic of an alternative arrangement for heating domestic hot water using heat from a solar heat source, including a heat dump.

FIG. 3 is a schematic of yet another alternative arrangement for heating domestic hot water with heat from a solar heat source, including a supplemental heat source.

FIG. 4 is a schematic of a further alternative arrangement for heating domestic hot water with heat from a solar heat source, including a heat exchanger.

DETAILED DESCRIPTION

There are a great many possible implementations of the invention, too many to describe herein. Some possible implementations that are presently preferred are described below. It cannot be emphasized too strongly, however, that these are descriptions of implementations of the invention, and not descriptions of the invention, which is not limited to the detailed implementations described in this section but is described in broader terms in the claims.

The descriptions below are more than sufficient for one skilled in the art to construct the disclosed implementations. Unless otherwise mentioned, the processes and manufacturing methods referred to are ones known by those working in the art.

FIG. 1 shows a system 10 for heating domestic hot water using a solar heat source. System 10 include a heating circulator pump P1 circulating water from a solar collector 11 through a tank 12, e.g., of a domestic water heater. The system 10 also includes a controller 16, a collector sensor 17 and a tank sensor 19. Together, these components optimize the functioning of the pump P1, providing optimized differential temperature control to compensate for changes in the heat supplied by the solar collector under varying weather conditions. The controller 16 may be, for example, a standard microprocessor programmed to perform the functions described above. The sensors may be standard temperature sensors. Advantageously, the controller 16 is integrated into a single fixture with the heating circulator pump P1, allowing the pump and controller to be easily removed for repair or replacement. The controller may be, for example, integrated into the circuit box for the pump.

FIG. 2 shows an alternative system 10′ for heating domestic hot water having a solar heat source. In the implementation shown in FIG. 2, there are two independent circulator pumps: a heating circulator pump P1 circulating water from a solar collector 11 through a tank 12, e.g., of a domestic water heater, and a heat dump circulator pump P2 for circulating water from the solar collector through a heat dump 110. The heated water in the water heater exits the water heater through an outlet line 13 which delivers the hot water to a domestic hot water supply or other use of the hot water, such as a heating system. As discussed above, the system 10′ includes a controller 16, a collector sensor 17 and a tank sensor 19. The system may also include an optional return sensor 18. In this implementation, these components control the functioning of both pumps, P1 and P2.

The differential temperature control system provided by the controller 16 will now be described in detail.

Controller 16 operates to maintain a setpoint temperature differential (ΔT_s) between the solar collector and the water heater (e.g., a direct fired water heater) and to maintain the temperature at the tank output below a predetermined maximum tank temperature setpoint (T_max). The tank sensor 19 is mounted on the hot water discharge (outlet to line 13) of the water heater. When the actual temperature differential (ΔT_a) between the collector and tank (measured by the collector sensor 17 and tank sensor 19) is greater than ΔT_s the controller 16 turns on the water heater pump P2 and the variable speed collector pump P1. The controller 16 operates the collector pump P1 at the minimum speed that will transfer heat from the collector 11 to the water heater 12. As the temperature at the tank sensor 19 approaches T_max, the controller reduces the output speed of P1. If the temperature measured by the tank sensor rises above T_max, the controller turns off both P1 and P2. The controller will also shut off both pumps if the temperature measured by the collector sensor 17 falls below a predetermined minimum collector temperature setpoint (T_min). This prevents circulation of water through the collector loop that has not been adequately heated in the collector. If the return sensor 18 is provided it can be used, with a flow meter, to calculate thermal energy produced by the collector.

Referring again to FIG. 2, when the temperature at the tank exceeds the predetermined value T_max, discussed above, water is circulated through the heat dump 110, e.g., a large thermal mass, by the heat dump circulator pump P2. Thus, if the temperature measured by the tank sensor 19 rises above T_max, the controller 16 turns off P1, operates a diverting valve V1, and turns P2 on. If the controller 16 receives a “shut-off” demand (e.g., a signal from a sensor 21 associated with the heat dump) while operating P3, the controller turns P1 and P2 off. During heat dump operation, the controller operates P1 (or shuts P1 off) as dictated by the actual temperature differential (ΔT_a) between the collector and tank, as discussed above.

In some cases, it may be desirable to supplement the heat supplied by the solar collector with a back-up heat source. A system 120 employing a back-up heat source is illustrated in FIG. 3. System 120 includes, in addition to the heating loop described above, a supplementary heat loop S. If during operation the temperature measured by the collector sensor 17 falls below the predetermined minimum collector temperature setpoint (T_min) the controller turns off pump P1, as discussed above. When this has occurred, once the temperature measured by the tank sensor 19 drops below the minimum tank temperature setpoint T_min, the controller turns on supplement pump P2. Pump P2 circulates water from a back-up heat source, e.g., a boiler 122, to the tank 12. If the boiler 122 is not already on, the controller 16 will activate the boiler. Pump P2 will remain on until the predetermined tank setpoint is reached, or until the temperature at the collector sensor indicates that the collector loop can be reactivated.

In another implementation, shown in FIG. 4, a collector circulator pump P1 circulate water from the solar collector 11 through a solar collector loop, and a water heater circulator pump P2 circulates water through the water heater 12. The water in the two loops flows through two sides of a heat exchanger 14, in the directions indicated by the arrows in FIG. 4, causing heat to transfer from the water entering the heating loop from the outlet of the solar collector, to the water returning from the water heater 12.

In all of the implementations discussed above, the controller 16 is advantageously integrated with the pump P1.

The circulator pumps are typically of the wet rotor circulator type. The pump impeller is received in a mating cavity known as a volute. Typically, the volute is surrounded by a flange to which the pump is attached. When the pump is installed, and the impeller thereby positioned within the volute, water enters the pump through an inlet at the center of the volute, and exits through an outlet in the periphery of the volute.

A number of embodiments of the invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, other embodiments are within the scope of the following claims.

Claims

1. A method of supplying heat to a solar heating system, the method comprising:

(a) heating liquid using a solar heat source;

(b) delivering the heated liquid to a storage reservoir;

(c) circulating the heated liquid through the storage reservoir and back to the solar heating unit using a circulator pump;

(e) determining the temperature differential between the temperature of the liquid exiting the solar heating unit and the temperature of the liquid after it has exited the storage reservoir; and

(f) controlling circulation of the liquid based on the temperature differential, using a controller that is integrated with the circulator pump.

2. The method of claim 1 wherein the circulator pump and controller are integrated in a single, unitary fixture.

3. The method of claim 1 further comprising turning off operation of the pump when the temperature differential exceeds a predetermined setpoint.

4. The method of claim 1 further comprising turning off operation of the pump when the temperature in the reservoir exceeds a predetermined maximum.

5. The method of claim 1 further comprising turning off operation of the pump when the temperature at the exit of the solar heat source falls below a predetermined minimum.

6. The method of claim 4 further comprising activating a heat dump pump when the predetermined maximum is exceeded, and diverting liquid from the solar heat source to a heat dump.

7. The method of claim 1 wherein the system further includes a supplemental heat source, and the method further comprises activating a supplemental pump when the temperature at the exit of the solar heat source falls below a predetermined minimum, to deliver heated liquid through a supplemental loop from the supplemental heat source to the reservoir.

8. A solar heating system comprising:

(a) a solar heat source configured to heat a fluid;

(b) a reservoir for storage of the heated fluid

(c) a path for circulation of fluid from the solar heat source to the reservoir and back to the solar heat source;

(d) a pump configured to circulate fluid through the path; and

(e) a controller, integrated with the pump, configured to control the operation of the pump in response to variations in the temperature of the liquid in the storage reservoir.

9. The heating system of claim 8 further comprising a tank sensor configured to measure the temperature of liquid exiting the storage reservoir.

10. The heating system of claim 9 further comprising a source sensor configured to measure the temperature of liquid exiting the solar heat source.

11. The heating system of claim 10 wherein the controller is configured to calculate the temperature differential between the temperature measured by the tank sensor and the temperature measured by the collector sensor.

12. The heating system of claim 8 wherein the solar heat source comprises a solar collector.

13. The system of claim 8 wherein the storage reservoir comprises a direct fired water heater.

14. The system of claim 8 wherein the storage reservoir comprises a storage tank for a heating system.

15. The system of claim 8 further comprising a supplemental heat source, and a supplemental pump configured to deliver heated liquid from the supplemental heat source to the storage reservoir.

16. The system of claim 15 wherein the controller is configured to control operation of the supplemental pump.