Solar-Powered Humidifier/Dehumidifier and Water Generator
Posted on July 25th, 2016
Note: This text would have been used in a patent application, but the Patent and Trademark Office has let us down. Lobbyists and Congress weakened patent protections with the America Invents Act, and patent trolls from big business simply litigate with individual inventors until they get what they want1. At this writing, the PTO averages 16.1 months before it takes the first action on a patent application, and 25.7 months to process the average application. Over 500,000 patent applications are now awaiting examination2.
Abstract of the Disclosure
A solar-powered system can provide humidification, dehumidification, and potable water. The sun’s energy is captured with twin-glass evacuated tubes and the heat is transferred to a freeze-resistant glycol/water mix. The hot glycol/water mix is directed either to a heat dissipater located inside the building (if heating and humidification are desired) or outside the building (if cooling and dehumidification are desired). The heat dissipater radiates the heat of the glycol/water mix through transfer fins that are bathed in a solution containing a reversible dehydrating agent. As it is heated, the dehydrating solution releases its adsorbed water. The dehydrating solution is pumped from inside the building to the outside and back with a small solar-powered pump. A still may be used in conjunction with the heat dissipater to produce distilled water from the adsorbed water. A logic system involving a controller, sensors, and solenoid valves directs the flow of the glycol/water mix to automatically accommodate humidification and dehumidification.
Field of the Invention
The present invention is in the field of humidity control, specifically a solar powered humidity control apparatus.
Background of the Invention
Humidity affects human comfort. Humans are sensitive to humidity because the human body’s primary temperature regulation mechanism uses evaporative cooling. When it is humid, perspiration evaporates more slowly. Humans perceive the rate of heat transfer from the body rather than temperature itself, so we feel warmer when the relative humidity is high than when it is low.
For example, if the air temperature is 75°F and the relative humidity is 0%, then the air temperature feels like 68°F . At the same air temperature, if the relative humidity is 100%, then we feel like it is 79°F . Thus by raising or lowering a building’s relative humidity, we adjust the apparent temperature, reducing heating or cooling costs and improving human comfort.
Indoor humidity control has other benefits apart from improving comfort and saving on heating and cooling costs.
High relative humidity at a surface — 70% or higher — can lead to problems with mold, corrosion, decay and other moisture-related deterioration. When relative humidity reaches 100%, condensation can occur on surfaces leading to a whole host of additional problems. An elevated relative humidity in carpet and within fabrics can lead to dust mite infestation and mildew. A consensus among microbiologists gives the critical relative humidity for adverse biological activity to occur on building envelope surfaces to be 70%.
Low humidity can have a variety of unwanted impacts. Breathing dry air is a potential health hazard which can cause such respiratory ailments as asthma, bronchitis, sinusitis, nosebleeds, and dehydration. Dry air can lead to sore eyes, dry skin, and dried mucosa. And low humidity can result in shrinkage of wood floors and wood furniture, cracking of paint on wood trims, and static electricity discharges.
When a room is uncomfortably cool, raising its humidity can make it comfortable, and if this can be done at a lower cost than raising its temperature, this may be preferable. Similarly, when a room is uncomfortably warm, lowering its humidity may make it comfortable, and might be economically preferable. When a room is hot and humid, one-third of the cooling load on an air conditioner comes from the removal of humidity.
Solar dehumidification has great potential to reduce energy use from air conditioning, and solar humidification has similar potential to reduce winter heating costs.
However, existing solar technologies have not produced systems that are economically competitive with conventional electrically driven systems. Solar systems have used two basic approaches in an attempt to capture the sun’s energy for cooling: thermal and photovoltaic.
Photovoltaic systems use photovoltaic panels to convert solar radiation directly into DC electricity. Photovoltaic systems have two major advantageous attributes: with an inverter to produce AC power, they can use conventional electrically driven humidifiers, and they can use the utility grid for backup power during dark or cloudy periods. Unfortunately, solar panels are expensive and do not store the surplus energy they capture. Storage batteries have a high initial cost, require periodic replacement, and normally use toxic and/or corrosive materials. These problems have prevented the use of photovoltaic systems in other than a few high-cost demonstration systems.
Thermal systems typically use a high-temperature flat-plate collector to supply heat to an absorption system. While thermal systems have the advantage of eliminating the need for expensive photovoltaic panels, they have proven bulky and inefficient.
Evaporative coolers are a related technology with a long history. Direct evaporative coolers consist of a means for moving air over a wet pad. Water evaporates from the pad and thereby humidifies the air. While they are intended for cooling the air, they also raise the humidity, raising the apparent temperature. Desiccant systems typically use a solid desiccant impregnated on a wheel of corrugated metal or plastic.
Some more obscure systems appear in the patent literature, but each has its own problems. U.S. Pat. Nos. RE 20,469,390, 4,660,390, and 4,854,129 describe regenerative indirect evaporative coolers that use a portion of the air exiting the dry cooler as inlet air to the wet side. U.S. Pat. No. RE 20,469 describes a cumbersome arrangement of coils and cooling towers that is complicated and expensive. U.S. Pat. No. 4,660,390 describes another system that uses tubes in a cross flow configuration to transfer heat between a wet side and a dry side. U.S. Pat. No. 4,854,129 also uses a system that uses a cooling coil with water from a cooling tower. U.S. Pat. No. 5,050,391 uses solid desiccant material and a true counter flow arrangement for the heat exchangers. It also has essentially a single stage of cooling which limits its performance and its ability to use inexpensive desiccant materials.
No commercially available system has been demonstrated that has the attributes that would be needed for commercially viable solar humidity control. Commercial success will require the system to have a low initial costs, small collector area, small storage size, backup capability, and the ability to both humidify and dehumidify.
The present invention can meet these requirements with no operating costs, lowering heating and cooling bills. As this invention removes water from the air, it creates potable water, a likely benefit in the warm climates where it is expected to be used.
Brief Summary of the Invention
The present invention uses solar power to manage indoor humidity, raising it (humidification) or lowering it (dehumidification) automatically as needed to maximize human comfort and minimize heating/cooling costs. When the system is actively involved in dehumidification, pure water is produced and captured as a byproduct. The process costs nothing to operate and uses the sun’s energy more efficiently than photovoltaic methods.
Brief Description of the Several Views of the Drawing
The present invention will become more fully understood from the detailed description given hereinafter and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention wherein:
Figure 1 is a schematic diagram showing the system when set to heat and humidify the building.
Figure 2 is a schematic diagram showing the system when set to dehumidify the building and generate potable water.
Figure 3 shows a heat dissipater, which is used to transfer this captured heat from a freeze resistant water mix to a desiccant mix inside or outside the building.
Detailed Description of the Invention
With reference to Figure 1, which shows the system in its heating/humidification mode, and Figure 2, which shows the system in its dehumidification/water generation mode, the system comprises one or more solar heat pipes placed in the sun on the outside of the building.
This invention uses the following components:
Heat Pipe (Location 5 in Figures 1 and 2). For the purposes of this invention, the Heat Pipe is any commercial product designed to create hot water from solar energy. Apricus Solar Co. offers one such product. The Apricus Evacuated Tube Solar Collector absorbs thermal energy from the sun and heats a freeze resistant water mix when can then be used to conduct the heat via insulated tubing to the selected Dissipater(s) (Figure 3 and at locations 1 and 2 in Figures 1, 2).
Heat Dissipater (Figure 3, and at locations 1, 2, and 3 in Figures 1 and 2). This is a radiator through which an uninsulated (metal) pipe carries the water mix from the Heat Pipe (Location 5 in Figures 1, 2). The pipe within the Heat Dissipater passes through heat transfer fins which conduct the heat away from the pipe, and to the liquid bath of the Desiccant Mix, which is pumped from location 1 to 2 (Figures 1 and 2) and back via a small water pump (Location 10 in figures 1 and 2).
Figure 3 shows details of the Heat Dissipater. The Heat Pipes send hot water (32) through aluminum heat transfer fins (31) as the power cable from the humidistat to the 3-way solenoid valve (30) so directs. The Desiccant mix bathes these heat transfer fins (31). Hot water is cooled within the Dissipater and returns to the storage tank (34). If the humidistat does not direct that hot water pass through the Dissipater, it follows the path shown in (33).
The outside Heat Dissipater (Location 1 in Figures 1, 2) is coupled with a still (Location 1 in Figures 1,2) in such a way that as water vapor is released from the Desiccant Mix, it is captured by the still, cooled by the surrounding air, and liquefied. This distilled water is then passed to a storage tank for future use.
The decision as to the routing of the water mix from the heat pipe (Location 5 in Figures 1, 2) is made by a humidistat (Location 3 in Figures 1, 2). When the indoor humidity is too low, this hot water mix is routed to the indoor heat dissipater (Location 2 in Figures 1, 2); when the indoor humidity is too high, this hot water mix is routed to the outdoor heat dissipater (Location 1 in Figures 1, 2). When used, one inside the building (Location 2 in Figures 1, 2) would cause the Desiccant Mix to release its adsorbed water, humidifying the room. When used, one outside the building (Location 1 in Figures 1, 2) would cause the Desiccant Mix to release its adsorbed water to the outside, dehumidifying the room.
The Heat Dissipaters connect via piping to the heat pipes (Location 5 in Figures 1, 2). They contain a freeze resistant water mix in a closed system that never comes into contact with the Desiccant Mix.
A hot water tank (Location 4 in Figures 1, 2) is used to store excess heat, allowing the system to operate both day and night, and during cloudy periods. Optionally, this tank may be conventionally heated (with natural gas, oil, etc.) as needed, allowing an additional source of energy to supplement the heating capabilities of the system permit operation during extended sunless periods.
Moisture Transport System
Desiccant Mix. This is a liquid comprising one or more hygroscopic (attracts water molecules) deliquescent (dissolves in water) chemicals dissolved in water. Such deliquescent chemicals might include calcium chloride (CaCl2), magnesium chloride (MgCl2), zinc chloride (ZnCl2), Carnalite (KCl*MgCl2*6H2O) and sodium hydroxide (NaOH). The choice of such chemicals would be made based on factors such as availability, cost, moisture adsorptive capacity, toxicity, stability, and willingness to release its adsorbed water at temperatures below that provided by the Heat Pipe.
The Desiccant Mix flows over the Heat Dissipater inside the building (Location 2 in Figures 1, 2), exposed to the ambient air. Here it adsorbs water vapor if the Heat Dissipater is unheated (room temperature), or releases water vapor if the Heat Dissipater is heated by the Heating System (Location 5 in Figures 1, 2).
The Desiccant Mix then flows outside the building, to the outside Heat Dissipater (Location 1 in Figures 1, 2), and is again exposed to the ambient air. Here it adsorbs water vapor if the Heat Dissipater is unheated (outside air temperature), or releases water vapor if the Heat Dissipater is heated gy the Heating System (Location 5 in Figures 1, 2).
Water from the outside Heat Dissipater (Location 1 in Figures 1, 2) is then returned via piping to the inside Heat Dissipater (Location 2 in Figures 1, 2).
Water movement for the Moisture Transport system is provided by a small pump (Location 10 in Figures 1, 2) that might be powered by a solar panel, wind turbine, or other means.
Humidistat (Location 3 in Figures 1, 2). This is a commercial humidity control unit that includes a sensing element and a relay amplifier. The humidistat determines whether the system will operate in humidification or dehumidification mode, directing the Desiccant Mix to a Dissipater inside the building or outside the building. The heat is directed to the inside Dissipater when the room needs to be heated and humidified, to the outside Dissipater when the room needs to be cooled and dehumidified.
Thermostat. A commercial thermostat is used to determine when the water of the Heating System has become too hot, directing it to the outside cooling Disssipater.
1.. A solar powered humidity control system, said system comprising:
- Twin-glass evacuated tubes for capturing heat from the sun and transferring it to a freeze resistant glycol/water mix;
- Heat dissipaters, located inside and outside a building, bathed in a solution containing a reversible dehydrating agent;
- A logic system involving a controller, sensors, and solenoid valves that direct the flow of the glycol/water mix to one of these heat dissipaters to automatically accommodate humidification and dehumidification requirements;
- A pump to move fluids from evacuated tubes to heat dissipaters and back, and to move the dehydrating solution from inside the house to outside and back.
2. The humidity control system of Claim 1 can both humidify and dehumidify the air.
3. The humidity control system of Claim 1 can produce potable water as a byproduct.
4. The humidity control system of Claim 1 can store excess captured solar energy, for use at night or during cloud cover.
5. The system is more energy efficient than one which uses solar panels.