WO2013130562A1

WO2013130562A1 - Solar powered direct current building heating and cooling system

Info

Publication number: WO2013130562A1
Application number: PCT/US2013/027964
Authority: WO
Inventors: Namir FAIDI
Original assignee: Hilos Ventures
Priority date: 2012-02-28
Filing date: 2013-02-27
Publication date: 2013-09-06

Abstract

A solar powered heating and cooling unit is disclosed. The solar powered heating and cooling unit comprises a solar panel array, an energy reservoir, and a heat pump unit. The heat pump unit is configured to operate on direct current from the solar panel array without an inverter. The energy reservoir is charged by the solar panel array and provides additional energy to the heat pump unit to assist with start-up and other situations in which the heat pump unit may need more energy than that being generated by the solar panel array. A solar charge controller may be coupled between the heat pump unit, the solar panel array and the energy reservoir to regulate the voltage and current being generated by the solar panel array.

Description

SOLAR POWERED DIRECT CURRENT BUILDING HEATING AND COOLING

SYSTEM

TECHNICAL FIELD

In general, the invention relates to building heating and cooling systems, and in particular, to solar-powered heating and cooling systems.

BACKGROUND OF THE INVENTION

Modern heating, cooling, and ventilation systems have been a major boon to modern societies. Effective, efficient heating and air conditioning have allowed extensive development and habitation, and a consequent increase in population, in areas of the world that regularly have extremes of heat and cold. Even where climate is relatively mild, heating and cooling systems can increase comfort and productivity.

Heating and cooling are typically energy-intensive endeavors. For example, a typical 10,000 BTU/hr window air conditioner (i.e., an air conditioning unit that moves 10,000 BTU (about 2.9 kW) of heat from the interior to the exterior of a building per hour) consumes about 1 kW of energy per hour to run. For that reason, heating and cooling systems are most often found in countries and areas with developed and reliable power grids, and relatively cheap power.

Unfortunately, the areas of the world that most need heating and cooling are often the areas of the world with the least developed and least reliable power grids. Thus, the options for installing heating and cooling systems in these areas are often limited.

SUMMARY OF THE INVENTION

One aspect of the invention relates to a solar powered air conditioning and heating system. The air conditioning and heating system includes a heat pump with indoor and outdoor portions. The heat pump is configured to use direct current (DC) and is powered by a set of solar panels, such that the system does not include an inverter to convert alternating current (AC) to DC. An energy reservoir is provided in the circuit to store energy generated by the solar panels and provide extra power during start-up and other non- steady state operating conditions. The energy reservoir may be, for example, a set of capacitors or a set of batteries. A solar charge controller controls the charging of the energy reservoir and the flow of power to the heat pump.

Another aspect of the invention also relates to a heating and cooling system. In embodiments of heating and cooling systems according to this aspect of the invention, the heating and cooling system also includes a heat pump with indoor and outdoor portions, a set of solar panels, and an energy reservoir. The heat pump is adapted to operate using DC power, without first converting that power to AC.

However, the heat pump also includes a transformer-rectifier and is thus adapted to accept AC power from a power grid, if one is available and to convert that AC power to DC power at an appropriate voltage. The heating and cooling system may use AC power from a power grid selectively, for example, if the solar panel array and energy reservoir cannot supply sufficient power to operate. In some embodiments, the output power from the transformer-rectifier may be used to charge the energy reservoir.

Other aspects, features, and advantages of the invention will be set forth below.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

The invention will be described with respect to the following drawing figures, in which like numerals represent like features throughout the invention, and in which:

FIG. 1 is a schematic diagram of a heating and cooling system according to one aspect of the invention;

FIG. 2 is a schematic diagram of the indoor unit of the heating and cooling system of FIG. 1;

FIG. 3 is a schematic diagram of the outdoor unit of the heating and cooling system of FIG. 1; and

FIG. 4 is a schematic diagram of a heating and cooling system according to another embodiment of the invention.

DETAILED DESCRIPTION FIG. 1 is a schematic diagram of a heating and cooling system, generally indicated at 10, according to one embodiment of the invention. The heating and cooling system 10 includes a heat pump, generally indicated at 12, with an indoor unit 14 and an outdoor unit 16; a solar panel array 18; an energy reservoir 20; and a solar charge controller 22.

The size, power, and other characteristics of the heating and cooling system 10, and of the heat pump 12 itself, will vary with the size of the room or enclosure that is to be heated and cooled, its level of insulation, its exposure to sun and other forms of radiant heat, and the temperatures to which and from which it is to be heated and cooled. As those of skill in the art will understand, larger rooms and poorly insulated rooms will require more powerful versions of the heating and cooling system 10.

In the heating and cooling system 10, the solar panel array 18 provides the primary power source for powering the heating and cooling system 10. The number and size of solar panels will depend on the size and amount of power required by the heat pump 12 and the efficiency of the solar panels themselves under ambient conditions where they are installed. The solar panel array 18 may be installed some distance from the other components of system 10. For example, in a home installation, the solar panel array 18 may be located on a roof or another structure that is directly exposed to sun. Any conventional factors may be considered in the placement of the solar panel array 18. Additionally, the solar panel array 18 may be located at greater distances from the other components of the system 10 as long as appropriate steps are taken to mitigate the effects of power loss caused by

transmission over a distance. In some embodiments, manual or automatic equipment may be used to allow the solar panel array 18 to track the position of the sun.

The solar charge controller 22 receives power generated by the solar panel array 18 and regulates the voltage and current flowing from the solar panel array 18 to the energy reservoir 20 to levels appropriate for the energy reservoir 20. It may also cut or redirect the flow from the solar panel array 18 when the energy reservoir 20 is full or allow the solar panel array 18 to power the heat pump 12 directly under certain conditions.

The energy reservoir 20 provides energy storage capabilities for periods when the heat pump 12 requires greater amounts of energy. Depending on the embodiment, the energy reservoir 20 may comprise a number of capacitors, a group of batteries, or any other appropriate components capable of storing energy. For example, the energy reservoir may comprise four 12V batteries, each of which is rated for 60 Amp-Hours. It should also be understood that although one advantage of the heating and cooling system 10 is its ability to operate using solar power alone, in some embodiments, if a connection to an existing power grid or generator is available, that component may serve alone or in combination with other components as an energy reservoir 20.

As one example of the sizing and power requirements of a heating and cooling unit 10 according to an embodiment of the invention, the heat pump 12 may draw about 570-900 Watts (W) in cooling and about 600-900 W in heating. The heat pump may be rated to draw 10-19 Amps of current, and to operate at a direct current (DC) voltage of about 48 volts (V). The electronics of the heat pump 12 may be configured to operate in a range from about 42VDC to about 60VDC, with 48VDC being optimal.

Preferably, the heat pump 12 is adapted to operate using direct current, rather than alternating current (AC). If the heat pump 12 operates on direct current, then it can accept power directly from the solar panel array 18 and the power reservoir 20 as needed. This means that the heat pump 12 can operate without the use of an inverter to convert DC to AC. Ultimately, the lack of an inverter allows the heat pump 12 to operate more efficiently while using less power, since inverters are often relatively inefficient, typically wasting 20-50% of the incoming energy.

The heat pump unit may have a maximum coefficient of performance of at least about 4 W/W, e.g., about 4.96 W/W for cooling and about 4.5 W/W for heating. Suitable models of compressors may include the Panasonic Model Nos.

5RS080XBD01 and XB208Z48 (Panasonic Wanbao Appliances Compressor Co. Ltd., Guangzhou, China).

Given those values and power requirements, the heating and cooling system 10 may be powered by, for example, three conventional solar panels, each rated to produce about 200 W, for a total of 600 W. If desired, larger solar panel arrays 18 may be used to ensure that adequate power is available, particularly in areas where full sun is not always available.

The indoor unit 14 and the outdoor unit 16 of the heat pump 12 also have fans, which are also configured to operate at a voltage of 48 VDC. They may be of sufficient size and characteristics to provide an air flow of, for example, 450 m³ per hour. The indoor and outdoor units may also have any conventional components, including transformers, expansion valves controlled by stepper motors, room temperature and humidity sensors, and any other conventional components. FIGS. 2 and 3 are schematic electrical diagrams for the indoor unit 14 and the outdoor unit 16 of the heat pump 12, respectively. As those of skill in the art will understand, the conventional heat pump implements a refrigeration cycle. A compressor compresses a refrigerant, which requires an energy input. The refrigerant leaves the compressor superheated and flows in vapor phase to a condenser, which lowers its temperature by removing heat and condenses some of the refrigerant by removing additional heat at constant temperature and pressure. The refrigerant then passes through an expansion valve, in which is pressure decreases, causing the refrigerant to evaporate immediately and cool. The cooled refrigerant passes through an evaporator, where it absorbs heat (and thereby cools the room), before returning to the compressor. In the heating and cooling system 10, the compressor and condenser are located in the outdoor unit 16 and the evaporator is located in the indoor unit 14. The refrigerant may be, for example, R-134a. The precise details of the heating and cooling components are not critical to the invention, so long as those components are adapted to operate on DC current.

The indoor unit 14 includes a fan motor 24 that powers a circulating fan or blower that blows warm air over the evaporator to cool it and a stepper motor 26 that controls the size of the aperture of the expansion valve. The airflow into the fan or blower may be protected by an air filter that is positioned so as to be user removable and replaceable.

The indoor unit 14 also includes a receiver 28 that allows the indoor unit 14 to receive commands via remote control. The receiver 28 may be an infrared receiver, a radio frequency receiver, or some other type of receiver. A room sensor 30 provides an indication of the ambient temperature, which can be compared to a setpoint temperature by a processor or thermostat to determine whether the heat pump 12 should be turned on. In embodiments of the invention, other types of sensors may be included, for example, ambient humidity sensors. Additionally, the heat pump 12 may include whatever sensors are necessary or desirable for monitoring its own performance.

As shown in FIG. 3, the outdoor unit 16 includes the compressor 32 and a driver 34 for the compressor 32. The outdoor unit also includes its own fan or blower with a fan motor 38 and a four- way valve 40. In addition to temperature -based controls, the heat pump 12 may have any other form of controls. For example, the heat pump may include a timekeeping device and controls that allow it to turn on and off at specified times.

As those of skill in the art will realize, the specific heating and cooling abilities referred to above, as well as the specific power requirements and efficiencies, relate to one particular example. Implementations of system 10 may be made with different heating and cooling abilities. For example, 12,000 BTU, 14,000 BTU, 18,000 BTU, and 20,000 BTU units may be made. In some cases, this may involve using larger or higher-capacity compressors, fans, and other components. In other cases, increasing the total heating and/or cooling ability may involve arranging a number of smaller-capacity components to work cooperatively (e.g., in series or parallel).

In the case of larger units with more heating and/or cooling ability, the amount of power produced by the solar panel array 18 and the amount of energy storable in the energy reservoir 20 would be larger in order to produce and store the additional power needed to drive the larger units 14, 16. As those of skill in the art will understand, a simple and typical way to increase the power output of the solar panel array 18 is to increase the surface area of the solar cells in the solar panel array 18; however, in some embodiments, more efficient solar panels may be used instead of increasing the surface area of the solar panel array 18, or in order to minimize the degree to which the solar panel array 18 is increased in size. To make the capacity of the energy reservoir 20 larger, larger capacity batteries or larger capacitors may be used. The amount of power actually required for any particular implementation of system 10 will depend on the desired heating and cooling power of system 10, the efficiencies of the units 14, 16, and on other factors.

Although the heating and cooling system 10 is particularly adapted for use with a solar panel array 18, systems according to embodiments of the invention need not be limited to using solar power or direct current. FIG. 4 is a schematic diagram of a system, generally indicated at 100, according to another embodiment of the invention. System 100 of FIG. 4 has many of the components of system 10, including a solar panel array 18, solar charge controller 22, and energy reservoir 20. However, in system 100, the heating and cooling unit 102 is adapted to use AC as well as DC.

Specifically, as shown in FIG. 4, the outdoor unit 104 includes a transformer 106 that accepts AC at a standard household voltage (e.g. 110 VAC, 220-240 VAC, etc.), steps the voltage down, and converts it to DC. (Typically, the transformer 106 would include a rectifier or other components to make the AC-to-DC conversion.) As those of skill in the art will understand, although the transformer 106 is shown as a part of the outdoor unit 104, it may be a part of the indoor unit 108 in some embodiments.

With the transformer 106 present, the user has the option of connecting the heating and cooling unit 102 to a power grid if a suitable one exists. The connection may be hardwired or made via a traditional electrical outlet. As shown, the transformer 106 may be connected to the energy reservoir via a connection 110, allowing the energy reservoir 20 to be charged from the power grid if the heating and cooling unit 102 is connected to one.

In some embodiments, the heating and cooling unit 102 may also be equipped with a processor, or software routines for an existing processor, that allow it to determine whether a power grid is present and, if so, whether to draw power from that power grid or from the solar panel array 18. For example, if a power grid is available, the heating and cooling unit 102 may draw power from it if the voltage provided by the solar panel array 18 and energy reservoir 20 is too low to allow the unit 102 to operate. In addition to checking the voltage state of the energy reservoir 20, the decision to take power from the power grid may be based on monitoring the voltage of the AC power from the power grid to determine if the voltage is consistent and whether or not any potentially deleterious voltage surges or dips are present.

Alternatively, power from the power grid may be used only to charge the energy reservoir 20 and not for operating power. In some cases, an AC power source that is determined by a processor in system 100 to be too unreliable to provide operating power (e.g., because of intermittent availability or voltage irregularities) could still be used to charge the energy reservoir 20 when it is available.

While the invention has been described with respect to certain embodiments, the description is intended to be illustrative, rather than limiting. Modifications and changes may be made within the scope of the invention, which is defined by the following claims.

Claims

WHAT IS CLAIMED IS:

1. A heating and cooling system, comprising:

a solar panel array;

an energy reservoir coupled directly or indirectly to the solar panel array and being in electrical communication therewith such that the solar panel array charges the energy reservoir; and

a heat pump unit in electrical communication with the solar panel array and the energy reservoir, the heat pump unit having an indoor portion and an outdoor portion and being configured to operate on direct current (DC) without an inverter to convert direct current to alternating current (AC).

2. The heating and cooling system of claim 1, further comprising a solar charge controller coupled to the solar panel array, the energy reservoir, and the heat pump unit, the solar charge controller being configured and adapted to control the charging of the energy reservoir and to regulate the voltage and current of energy flowing to the heat pump unit.

3. The heating and cooling system of claim 1, wherein the energy reservoir comprises one or more capacitors.

4. The heating and cooling system of claim 1, wherein the heat pump unit has a coefficient of performance in heating and cooling greater than about 4 W/W.

5. The heating and cooling system of claim 4, wherein the heat pump unit has a coefficient of performance in cooling of about 4.96 W/W.

6. The heating and cooling system of claim 4, wherein the heat pump has a coefficient of performance in heating of about 4.5 W/W.

7. The heating and cooling system of claim 1, wherein the heat pump unit is adapted to operate in a voltage range of about 42-60 volts of direct current.

8. The heating and cooling system of claim 7, wherein the heat pump unit is adapted to operate at a voltage of about 48 volts of direct current.

9. The heating and cooling system of claim 1, wherein the solar panel array supplies at least about 600 W of power.

10. The heating and cooling system of claim 1, wherein the heating and cooling unit is adapted to be connected to a power grid and further comprises a transformer-rectifier to convert AC power from the power grid to DC power at a voltage useable by the heating and cooling unit.

11. The heating and cooling system of claim 10, wherein the transformer- rectifier of the heating and cooling unit is connected to the energy reservoir to charge the energy reservoir.

12. The heating and cooling system of claim 10, wherein the heating and cooling unit is adapted to draw power from a power grid if a voltage provided by one or both of the energy reservoir and the solar panel array is below a threshold.