US20180231332A1

US20180231332A1 - Renewable energy heater

Info

Publication number: US20180231332A1
Application number: US15/431,616
Authority: US
Inventors: Momoe ANNO; Miri YASUDA; Nidhi JAJU; Mai MORITA; Youkie SHIOZAWA
Original assignee: Individual
Current assignee: Individual
Priority date: 2017-02-13
Filing date: 2017-02-13
Publication date: 2018-08-16

Abstract

A portable heating device that includes a phase changing material mixture to absorb and release thermal energy and warm a space via convection heating. The phase changing material mixture includes sodium sulfate decahydrate, sodium chloride, and sodium polyacrylate. The phase changing material mixture is contained in portable aluminum capsules. A holder, also made of aluminum, can be used to carry one or more of the aluminum capsules.

Description

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a renewable energy heater and uses and manufacture thereof.

Discussion of the Related Art

It is essential for humans to have a heating system, whether they live in temperate climates where heating is necessary only during the winter, or they live in cold climates where heating is desired year-round. The kind of heating system each person needs depends on several factors such as what general climate they live in, the size of the room they wish to heat, and how many people are in the room. Unfortunately, most conventional heating systems that are used around the world depend on the use of fossil fuel, a nonrenewable resource that is not environmentally friendly and that can contribute to global warming.
Although recently there has been an interest in developing heating systems that are more environmentally friendly, the current heating systems' ability to promote more environmentally friendly habits has not been fully realized because of the unrestrained usage of fossil fuel, the unsecured access to non-renewable energy, and the high cost of alleged “green” heaters. Thus, a need exists for an alternative to the current heating systems' dependency on fossil fuel, an alternative that can provide a much more economical, portable, and environmentally friendly heater that promotes the reduction, reuse, and recycle for a greener world.
There are various ways renewable resources can be used in a heating and/or cooling system using Phase Change Materials (PCM) to emit heat to the surroundings. PCMs are used to store heat energy by alternating between two phases, for example between a solid and liquid state. When sufficient heat is supplied, the PCM melts into a liquefied form and stores heat energy that can later be released while the PCM solidifies.
Some exemplary applications of PCM use include heating systems that burn biomass, such as charcoal, biofuels, and bio gases, as fuel to supply the heat energy to melt and thus “charge” the PCM. These systems however, although green in that they use biomass, still require energy to burn the biomass and thus can have a negative environmental impact, in addition to being limited to being tethered to a power supply and typically involving expensive equipment.
Another exemplary application has involved solar radiation, a form of solar thermal energy, that can be collected from the sun using solar panels and iron plates. The heat collected can again be provided to the PCM causing it to melt and thus store the heat energy for later use. For example, Roof-Integrated Solar Air Heating and Storage Systems have been developed to collect solar radiation in order to heat air and a thermal storage unit to store heat. An advantage of this system is its high ventilation. However, solar panels do have their drawback, for example the solar energy availability is weather dependent and thus can be unreliable. Also, in some instances, the solar systems may need assistance from external power sources to assist in the melting of the PCM. Moreover, solar panels are generally expensive and most often are stationary fixtures that cannot easily be relocated.
Geothermal Heat Pumps are another exemplary heating and cooling system for homes. Geothermal pumps use the geothermal energy in the ground to provide and absorb heat energy to heat and cool a home. Like solar panels, geothermal heat pumps can be used directly to heat and cool a home or can be coupled with the use of PCM as means to store heat energy. Geothermal heat pumps also have the additional ability to heat water in the house and also tend to be more reliable than solar panels. On the other hand, geothermal pumps often require electricity for operation, and have the disadvantage of only coming in large scale systems that tend to be very expensive to install.
Two exemplary products that use PCM to store and release energy on a much smaller and thus more portable scale include the Hand Heater (See e.g., Chinese Patent Number CN2092981U, incorporated herein by reference) and the ClickHeat hand warmer.
The Hand Heater is a portable heater that uses PCM to store and release heat energy. This product generally includes a casing, coils, automated circuit breaks, an integrated circuit, a plug, an electrical wire, a switch, and a light bulb. When plugged into an outlet the coils are heated. The heat generated by the coils causes the PCM to melt and thus store heat energy. When the coils and the PCM are heated to about 70-80° C., the automated circuit breaks will turn the machine off and the PCM inside begins to cool down. As the PCM cools, it releases heat energy providing warmth to its surroundings. Two light bulbs signal when the machine is charging. Once charged, the heater can stay warm for about 3-4 hours before recharging is necessary. Because of its small size, the hand heater has the advantage of being portable.
A large disadvantage of the hand heater, however, is its constant need to be recharged using an electrical source. This requirement restricts the use of the hand heater to areas where electricity is readily available. Also, though the hand heater is not directly burning coal or fossil fuel to create heat, finite resources are most likely used to generate the electricity necessary to charge the heater. Thus, although it may seem that the hand heater is eco-friendly, the use of electrical energy may still be contributing to global warming and similar environmental issues. Moreover, the hand heater is a small device that is designed to warm a person's hands and thus only capable of a limited amount of heat.
ClickHeat is a reusable heat pack created by an English Company also called ClickHeat. This product is mainly a thermo therapy tool that can be used to ease pain, reduce muscle stiffness, decrease muscle spasms, and increase blood flow to area in need of healing. The heat pack uses super-cooled sodium acetate, a phase change material, to heat the ClickHeat to an average temperature of 54° C. In its normal state, the super-cooled sodium acetate remains in liquid form. A clicking metal disk is provided in the pouch containing the liquid sodium acetate. When the metal disk is clicked it provides a nucleation site for the sodium acetate thus causing it to crystallize. As the sodium acetate crystallizes, it emits heat. Once the sodium acetate has fully crystallized it stops emitting heat. To cause the sodium acetate to return to its liquid form, the pouch containing the sodium acetate must be placed in boiling water. Thus, energy to boil water and access to boiling water are required for the proper utilization of this product. Like the hand heater, the ClickHeat is also designed to provide localized heating for personal use and not to heat a home or a room.
Thus, although systems like the Roof-Integrated Solar Air Heating and Storage System use renewable energy to heat and recharge a PCM, they are inconvenient, non-portable, expensive and often require a supplemental power source to heat charge the PCM or to release heat from the PCM. Small scale, portable known heating devices that use PCM like the Hand Heater and the ClickHeat also require the use of electrical energy or non-renewable energy source to provide sufficient heat to liquefy the PCM and thus recharge the heating devices. A need therefore exists for a device that can have the advantage of small size and portability of devices like the Hand Heater, without requiring the electrical energy or non-renewable energy to recharge the PCM, that can also provide sufficient heat to warm large areas but without depending only on solar energy, geothermal energy, or energy obtained by burning biomass fuel.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a renewable energy heater that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
An advantage of the present invention is that it is particularly suitable for areas with relatively temperate climates where there is a need for cost effective heating systems for the winter. The present invention can also be used in places where traditional heating systems are prevalent to complement the fossil fuel based heating systems to thus lessen the use of fossil fuels and in turn lessen the harmful effects to the environment.
An advantage of exemplary embodiments of the present invention is to provide an alternative method to heat houses, workplaces, and other locations, by replacing heating methods that use energy produced by fossil fuel. This promotes conservation of fossil fuel and helps reduce pollution.
Also, exemplary embodiments of the present invention provide an economical and environmentally friendly alternative to conventional heating systems. This can aid in addressing the problem of low-income households not being able to have access to heating systems where there may not be access to electricity.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, a heating device having a PCM mixture of sodium sulfate decahydrate, sodium chloride and sodium polyacrylate. The sodium sulfate decahydrate and the sodium chloride in the mixture are present at a 1:1 molar ratio. The PCM mixture includes about 2.5% wt of sodium polyacrylate. At least one capsule houses the PCM mixture. The capsule can be made of aluminum. A holder can be provided having a base that houses at least one capsule. The base can have at least one wheel. A retractable handle can be connected to the base.
In another aspect of the present invention, a portable heating device having a portable container, a PCM mixture contained inside the portable container, and a holder for the portable container, the holder having a handle.
The portable container can be cylindrical. The portable container can be made of aluminum. The PCM mixture can include sodium sulfate decahydrate, sodium chloride, and a polyacrylate. The holder can be made of aluminum.
In yet another aspect of the present invention, a method of heating including placing one or more portable heating capsules into a room, each capsule containing a PCM mixture, allowing the PCM mixture to absorb heat from the environment surrounding the one or more portable heating capsules while the environment is at a temperature above a melting temperature of the PCM mixture, and allowing the PCM mixture to release heat into an environment surrounding the one or more portable heating capsules when a temperature of the environment is below the melting temperature of the PCM mixture. At least five portable heating capsules are placed into a room. The PCM mixture can include sodium sulfate decahydrate, sodium chloride, and sodium polyacrylate. The one or more portable heating capsules can be made of aluminum.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention.

In the drawings:

FIG. 1 is an illustrative embodiment of the internal dimensions of a capsule in accordance with the present invention.

FIG. 2 is an illustrative embodiment of a capsule of the present invention having a wall thickness.

FIG. 3 is an illustrative embodiment of a capsule containing a PCM mixture in accordance with aspects of the present invention.

FIG. 4 is an illustrative embodiment of a holder carrying five capsules in accordance with aspects of the present invention.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Reference will now be made in detail to an embodiment of the present invention, example of which is illustrated in the accompanying drawings.
Exemplary embodiments provide efficient heating devices that effectively utilize the latent heat properties of a PCM to heat or maintain the temperature of a room through convection heating without requiring assistance of electrical power, biomass fuel, fossil fuel, solar or geothermal heat mining. Exemplary embodiments of the invention can also provide a regenerative source of energy that can easily be relocated.
The PCM is provided so that it can change to a first state when absorbing heat energy, and to switch to a second state when releasing heat. The first and second states are not particularly limiting and can include gas, liquid, and solid. In exemplary embodiments the first state is liquid and the second state is solid. In alternative embodiments, the first state can be gas and the second state can be liquid or solid. For purposes of this disclosure, the term “solid” is used herein to also refer to gel.
The PCM used in exemplary embodiments can be any PCM that has a high latent heat of fusion. For purposes of this application, “high” latent heat of fusion is one that is at least about 140 KJ/Kg.
The PCM can be either a single material component or a mixture of materials. In an exemplary embodiment, the PCM may include a mixture of a phase changing material component and a salt. The mixture can be for example one including a phase changing material component and salt. The phase changing material component and salt mixture may further include a polymer.
An exemplary PCM material that can be used in embodiments of the present invention is a mixture of sodium sulfate decahydrate and sodium chloride. An alternative exemplary PCM is calcium chloride hexahydrate. Another exemplary PCM is glycerin. Also, n-hexadecane may also be used as a PCM. Although not necessarily in mixture forms, each of these materials are commercially available for example from Sigma-Aldrich (St. Louis, Mo.). The latent heat of fusion of the above materials is provided in Table 1 below. It should be noted that the PCM is not limited to these materials.

TABLE 1

Sodium Sulfate	Calcium
Decahydrate +	Chloride
Sodium Chloride	Hexahydrate	Glycerin	n-Hexadecane

Safety	Non-toxic, but	Severe eye	Non-toxic, but	Non-toxic, but
	may cause eye	irritation;	can cause skin	can cause skin
	irritation and	burns skin;	and eye irritation;	irruption and
	temporary	inflammation	may combust at	eye irritation;
	asthma	from inhalation	high temperature	combustible

Melting	18°	C.	24°	C.	17.9°	C.	17°	C.
Point
Latent Heat	286	kJ/Kg	140	kJ/Kg	198.7	kJ/Kg	237	kJ/Kg
of Fusion

Cost (from	$80-$100 per	$220-$250 per	$500-$600 per	$5000 per
alibaba.com)	metric ton	metric ton	metric ton	metric ton

In preferred embodiments, the PCM used is also generally non-toxic, and can be handled safely. Also, it is generally preferable to use a low cost PCM to make the heating device more affordable. Accordingly, preferred embodiments described herein use the mixture of sodium sulfate decahydrate (Na₂SO₄.10H₂O) and sodium chloride (NaCl).
In exemplary embodiments the mixture of sodium sulfate decahydrate and sodium chloride will also include a polyacrylate. An exemplary polyacrylate that can be used is sodium polyacrylate (C₃H₃NaO₂). Other polyacrylate can also be used. The polyacrylate may be in its pure form or may include some impurities as long as the impurities do not negatively affect the properties of the PCM mixture.
In exemplary embodiments the molar ratio of the sodium sulfate decahydrate to the sodium chloride will be approximately 1:1. It was found that this 1:1 ratio provides the proper melting temperature for the PCM mixture. Exemplary PCM mixtures will include about 80% wt to 85% wt of sodium sulfate decahydrate, about 14% wt to 17% wt of sodium chloride, and about 1% wt to 3% wt of polyacrylate. In a preferred embodiment the PCM mixture will include about 82.9% wt sodium sulfate decahydrate, about 15% wt sodium chloride, and about 2.1% wt of sodium polyacrylate.
The mixture of sodium sulfate decahydrate, sodium chloride and a polyacrylate as the PCM is particularly advantageous. Sodium sulfate decahydrate is a phase changing material that has a high latent heat of fusion of about 252 kJ/Kg. The addition of sodium chloride salt, at the appropriate 1:1 molar ratio discussed earlier, provides the benefit of increasing the latent heat to 286 kJ/Kg, thus allowing the mixture to store more heat. The addition of sodium chloride at the 1:1 molar ratio also lowers the melting point to 18° C. from the otherwise 32° C. This allows the heating element to be used in cooler environments where heating is desired. The addition of the small amount of polyacrylate does not affect these properties of the PCM mixture. However, the polyacrylate provides a great ability to absorb water. For example, sodium polyacrylate can absorb 800 times its weight in water. The absorbent property of the polyacrylate allows it to readily absorb the initial water separated from the sodium sulfate decahydrate, and in doing so it can also prevent an excessive amount of water from being separated from the sodium sulfate decahydrate. This allows the PCM mixture to properly cycle through phase changes between the heated state to the cool state. After testing the mixture using sodium polyacrylate for at least 15 phase change cycles, it was confirmed that the mixture can go through numerous cycles without excessive water separation.
It is noted that when using the PCM mixture of sodium sulfate decahydrate, sodium chloride and polyacrylate, the PCM mixture is in the liquid state at room temperature. Thus, for purposes of discussion in this application, the first state for this PCM, i.e. when heat energy is stored, is the liquid state. When the heat energy is released, the PCM mixture changes to a solid. Thus, the solid state is the second state of this PCM mixture.
The amount of PCM mixture to be used is not particularly limited. The containers or capsules described below can be made to size to accommodate any desired amount of PCM mixture. In exemplary embodiments, the heating device or heating system is intended to be portable. As such, in exemplary embodiments the heating system can include multiple portable capsules each sized to contain an amount of PCM that is not too heavy for transport. In alternative embodiments, the heating system can be made as a permanent fixture. In such embodiments, the system can be designed to contain large amounts of PCM. Likewise, exemplary embodiments can include large heating capsules designed to be relocated using mechanical equipment like a crane or forklift. In such embodiments the capsules can be designed to house large quantities of PCM.
The amount of PCM used in a heating system or heating device, whether the PCM is contained in a single capsule or a plurality of capsules, can be dependent on the size of the area to be heated, the temperature to maintain and the level of insulation available for the space to be heated. PCM heating is based on the storage and release of energy governed by the latent heat of fusion properties of the PCM. The latent heat equation can provide the amount of energy required to change phase, the equation is:
Q=Lm
where Q is the amount of energy required to change state, L is the latent heat of the material, and m is the mass. The values of the latent heat of fusion for exemplary materials are provided in Table 1.
The quantity of PCM necessary to heat a given volume of dry air can be approximated by using the specific heat equation:
Q=C _p mΔT
where Q is the amount of thermal energy required to change the temperature (ΔT), of a material; C_pis the specific heat of the material to be heated; and m is the mass of the material to be heated.
According to the above equation, if one were to attempt to increase the temperature of 1 m³of dry air from 15° C. to 16° C., the energy required would be:
Q=(1.005 kJ/kg° C.)(1.225 kg)(1° C.)
Q=1.231 kJ
where the specific heat of air at 15° C. at sea level is about 1.005 kJ/Kg° C., and the density of dry air at 15° C. at sea level is 1.225 Kg/m³(thus resulting in 1 m³of dry air having a mass of 1.225 Kg).
In accordance with the above, it is therefore known that it will take 1.231 kJ of thermal energy to raise the temperature of dry air by 1° C., assuming no loss of heat. Assuming one is to heat the air of a thermally insulated room, how much PCM is required to increase the air temperature can be determined based on the amount of temperature change desired and the amount of air.
For example, assuming that one desires to heat dry air by 3° C., according to the above, this will require three times the energy necessary to raise the temperature by one degree. Thus, the total energy necessary to increase the temperature by 3° C. is 3×1.231 kJ, which equals 3.693 kJ. Earlier it was discussed that the latent energy of a PCM mixture of sodium sulfate decahydrate, sodium chloride and a polyacrylate is 286 kJ/Kg. Thus, to increase the air temperature by 3° C., one would need only 0.0129 Kg, or 12.9 g of the PCM mixture.
Alternatively, one can determine the size of a space that could be heated with the same PCM mixture. As discussed, the latent heat of the PCM mixture is 286 kJ/Kg. One kilogram will provide 286 kJ, dividing this by 3.693 kJ, the energy required to raise by 3 degrees Celsius 1 m³of dry air, results in 77.44 m³. Thus, one kilogram of PCM mixture can raise the temperature of 77.44 m³of dry air by 3° C.
In exemplary embodiments, the heating system or device can include a single capsule containing 1 kg of PCM or PCM mixture. In the alternative, the single capsule may contain more than 1 kg of PCM or PCM mixture and release more energy, thus able to exert more thermal energy to warm the dry air in the space. It may also be possible to use multiple capsules of similar or different PCM or PCM mixture amounts to increase the efficacy of the heating system or device.
It should be understood, however, that the energy provided by the PCM or PCM mixture will not be able to increase the temperature above that at which point the PCM or PCM mixture will change state. Thus, in embodiments where a PCM or PCM mixture has a melting point of 18° C., the heating device or system will only be able to raise the temperature of the air to a maximum of 18° C. At any temperature higher than the state changing temperature of the PCM or PCM mixture, for example at temperature higher than its melting temperature, the PCM or PCM mixture will start changing state and thus absorb heat rather than release heat. Accordingly, as an additional advantage of the present invention, the heating system or device can act as a self-governing thermostat that will attempt to keep the air in a given space at the temperature at which the PCM or PCM mixture changes states. In exemplary embodiments, that temperature would be about 18° C.
In addition to the above, it is further noted that the PCM or PCM mixture will also be able to release thermal energy even when not transitioning between phases. The amount of heat released can be approximated by the specific heat equation using the specific heat information for the PCM or PCM mixture. For example, if the PCM or PCM mixture is heated a temperature much higher than its melting temperature, the PCM or PCM mixture will become warmer and store extra heat that will be released as the PCM or PCM mixture is left to cool. For example, if the PCM mixture of sodium sulfate decahydrate, sodium chloride and sodium polyacrylate is heated to 23° C., i.e. 5° C. above its melting point, then, based on its specific heat, the PCM mixture will store the energy required to increase its temperature by five degrees. The PCM mixture will be able to release this thermal energy as it cools down to 18° C. The PCM mixture will also be able to release heat after phase transition as it cools further. This specific heat energy will be in addition to the latent heat energy otherwise released.
Table 2 below further demonstrates a tabulation of possible arrangements of one or more capsules each with 1 Kg of PCM mixture of sodium sulfate decahydrate, sodium chloride and a polyacrylate. The table provides the size of the space or volume of dry air in cubic meters that each arrangement would be able to maintain at about 18° C.

TABLE 2

					4 Cap-	5 Cap-
		1 Capsule	2 Capsules	3 Capsules	sules	sules
		Energy	Energy	Energy	Energy	Energy
T of	ΔT to	Release	Release	Release	Release	Release
Room	Achieve	286 kJ	572 kJ	858 kJ	1144 kJ	1430 kJ

(° C.)	18° C.	Volume of Dry Air in Cubic Meters

17	1	232.33	464.66	696.99	929.33	1161.66
16	2	116.17	232.33	348.50	464.66	580.83
15	3	77.44	154.89	232.33	309.78	387.22
14	4	58.08	116.17	174.25	232.33	290.41
13	5	46.47	92.93	139.40	185.87	232.33
12	6	38.72	77.44	116.17	154.89	193.61
11	7	33.19	66.38	99.57	132.76	165.95
10	8	29.04	58.08	87.12	116.17	145.21
9	9	25.81	51.63	77.44	103.26	129.07
8	10	23.23	46.47	69.70	92.93	116.17
7	11	21.12	42.24	63.36	84.48	105.61
6	12	19.36	38.72	58.08	77.44	96.80
5	13	17.87	35.74	53.61	71.49	89.36
4	14	16.60	33.19	49.79	66.38	82.98
3	15	15.49	30.98	46.47	61.96	77.44
2	16	14.52	29.04	43.56	58.08	72.60
1	17	13.67	27.33	41.00	54.67	68.33
0	18	12.91	25.81	38.72	51.63	64.54
−1	19	12.23	24.46	36.68	48.91	61.14
−2	20	11.62	23.23	34.85	46.47	58.08
−3	21	11.06	22.13	33.19	44.25	55.32
−4	22	10.56	21.12	31.68	42.24	52.80
−5	23	10.10	20.20	30.30	40.41	50.51
−6	24	9.68	19.36	29.04	38.72	48.40
−7	25	9.29	18.59	27.88	37.17	46.47
−8	26	8.94	17.87	26.81	35.74	44.68
−9	27	8.60	17.21	25.81	34.42	43.02
−10	28	8.30	16.60	24.89	33.19	41.49
−11	29	8.01	16.02	24.03	32.05	40.06
−12	30	7.74	15.49	23.23	30.98	38.72
−13	31	7.49	14.99	22.48	29.98	37.47
−14	32	7.26	14.52	21.78	29.04	36.30
−15	33	7.04	14.08	21.12	28.16	35.20

According to the above, a heating system having five capsules of 1 kg of PCM mixture of sodium sulfate decahydrate, sodium chloride and a polyacrylate, would be able to absorb and then release sufficient thermal energy to heat a space of 35.20 m³from −15° C. to 18° C.
The efficiency of the heating system or device can also be affected by the design and material of the capsules used to contain the PCM mixture. The material used for the capsules is not particularly limited, however, in preferred embodiments the material should be a good thermal conductor. The material should also preferably be resilient to everyday use. The material should have sufficient structural integrity to safely hold the PCM mixture. The material should also be one that does not react with the PCM mixture. The material should preferably be one that can withstand corrosion from the PCM mixture and from the surrounding elements in which the capsule is to be used. The material may also have a low thermal expansion coefficient that it can retain structural stability over a wide temperature range. The material can preferably be economical. In exemplary embodiments the material can also be recyclable. In preferred embodiments, the material is also lightweight so that a capsule can easily be transported. Although not limited to a particular material, exemplary capsule materials include aluminum, steel, copper and brass. Properties of these materials are provided below in Table 3.

TABLE 3

Aluminum	Steel	Copper	Brass

Melting Point	660.323°	C.	1412.5°	C.	1084.62°	C.	887.5°	C.
Density	2.70	g/cm³	7.74	g/cm³	8.96	g/cm³	8.55	g/cm³
Thermal	205.0	W/mK	50.2	W/mK	385.0	W/mK	109.0	W/mK
Conductivity

Hardness	99-101	137-595	80-85	192-202
(Brinell Scale)
Thermal	23	13	17	19
Expansion
Coefficient
(10⁻⁶m/m ° C.))
at 20° C.
Cost per metric	$1517.00	$170.00	$4672.00	$2975.00
ton

Exemplary embodiments use capsules made of aluminum. The advantages of aluminum are its availability and affordability.
The shape and size of the capsules is also not limited to a particular design. However, it is preferable that the capsules be formed so as to be easy to handle, provide a large surface area to promote heat transfer, and maintain sufficient structural integrity to hold the PCM or PCM mixture. Possible capsule shapes can include cubes, prisms, cylinders, as well as non-geometric shapes. In a preferred embodiment the capsules have a cylindrical shape. The rounded contour of the cylinder provides larger area for heat transfer. The cylindrical shape is also easy to carry.
FIG. 1 provides an exemplary embodiment of a capsule 100. As illustrated, the capsule is of a cylindrical shape, having a height 101 and a base diameter 102. In exemplary embodiments, the capsules are airtight.
The size of the capsule can be set in accordance with the desired capacity. Accordingly, the size of the capsule is not particularly limited. In exemplary embodiments, the capsules are portable and thus sized accordingly so that they can easily be transported. It should be recognized that the volume of the PCM or PCM mixture to be housed in a capsule will also vary with temperature, especially as the PCM or PCM mixture transitions from a first state to a second state. Accordingly, the capsule preferably can be sized to have a volume that is about 5% to 30% larger than the volume of the PCM or PCM mixture to be contained in the capsule. In exemplary embodiments the capsule can have a volume of about 10% to 25% larger than the volume of the PCM or PCM mixture to be contained therein. The extra volume provided in the capsule, referred herein as the headspace, can be filled with air, inert gas, or any other gas species or mixture that does not react with the PCM mixture or any component thereof. In exemplary embodiments, the headspace cannot be filled with a liquid or even water, as such could interfere with the functioning of the PCM or PCM mixture. For example, added water in the headspace when using the PCM mixture of sodium sulfate decahydrate, sodium chloride, and sodium polyacrylate, could cause more of the sodium sulfate decahydrate to become sodium sulfate, which would not be able to release thermal energy.
In alternative embodiments, the capsule may be designed to expand as the PCM or PCM mixture expands thereby preventing breakage of the capsule walls. Also, the added volume, or headspace, or the ability to expand would provide for a better containment of the PCM or PCM mixture and maintenance of the pressure inside the capsule to safe levels.
In preferred embodiments, the capsule will have an internal volume defined by an internal height of about 16 cm, and an internal base diameter of 8 cm. In alternative embodiments, the internal height can vary from 5 cm to 100 cm, and the internal base diameter can vary from 2 cm to 100 cm. Larger or smaller sizes can also be used.
Another consideration for the capsule is the thickness of the wall. The thickness of the wall can be determined based on the thermal conductivity of the material and the materials' structural integrity. In exemplary embodiments, the thickness 103 of the material used to construct a capsule will vary from 0.2 cm to 10 cm. In an embodiment using aluminum, the thickness 103 can be within the range of 0.5 cm and 5 cm. In a preferred embodiment, as illustrated in FIG. 2, the thickness 103 of the aluminum layer is 0.5 cm.
The thickness of the wall of the capsule would also increase the overall size of capsule. In an exemplary embodiment, the total outside dimension of a capsule having an internal height of about 16 cm, an internal base diameter of about 8 cm and a wall thickness of 0.5 cm, will be an outer height of about 17 cm and an outer diameter of about 9 cm.
In addition to size, shape and wall thickness, the surface of the capsules can also be treated to improve heat absorption efficiency. For example, although aluminum is a preferred material to use for capsules, this material tends to be highly reflective. Accordingly, it is preferable to treat the outer surface area of an aluminum capsule to decrease its reflectance and thus increase heat absorption, especially if a source of heat is to be sunlight. Various surface treatment that decrease reflectance can be used including application of antireflective coatings, paints, or other similar materials. The outer surface of the capsule may also be treated mechanically and/or chemically to reduce its reflectance. In an exemplary embodiment, the outer surface of the aluminum capsule can be painted of a dark color. For example, the outer surface may be coated with a black material. The black material may be black paint. The coating material should preferably not interfere with the heat transfer of the capsule. In exemplary embodiments, the outer dark coating can be a very thin layer of material. For example the coating may have a thickness ranging from 0.05 cm to 0.0001 cm.
The amount of PCM or PCM mixture to be stored in the capsule is also not particularly limited as the capsule can be made of varying sizes. In an exemplary embodiment as shown in FIG. 3, a cylindrical capsule having a wall thickness 103 of about 0.5 cm, and an internal volume defined by an internal height 101 of about 16 cm and an internal base diameter 102 of about 8 cm, and thus of about 804 cm³, can be used to contain about 1 Kg of PCM mixture 200 containing sodium sulfate decahydrate, sodium chloride and polyacrylate as discussed earlier. The density of 1 Kg of powder PCM mixture 200 as described earlier, i.e. including sodium sulfate decahydrate, sodium chloride and sodium polyacrylate, is about 1.567 g/cm³, thus 1 Kg of PCM mixture would require about 638 cm³of volume. This volume is likely subject to a 10% increase when in the liquid phase and thus about 702 cm³. As such, the PCM mixture volume ranges between 20% and 8.7% of the volume of capsule depending on the phase of the PCM mixture. The extra volume of the capsule, therefore, is adequate to contain the PCM mixture in either phase and also allow room for accommodate any pressure differential.
The capsule may also be equipped with a resealable cap or opening to allow one to add the PCM or PCM mixture to the capsule or to drain the capsule of its contents. The caps may be screw on caps. Alternatively, the caps may be rubber caps that seal the capsule through a tight fit. Alternatively, the caps can be secured to the capsules using fasteners such as clamps. Also, magnetic caps can be used. The capsule may also be equipped with sensors and safety devices. For example, the capsules may be equipped with thermal sensors such as thermometers, thermocouples or like device. Capsules may also be equipped with pressure sensors. Thermal and pressure sensors can be designed to provide information regarding the PCM or PCM mixture inside the capsule and/or the condition at the wall of the capsule. The capsules can also be equipped with digital screens and processors that can monitor, calculate and provide information regarding the internal state of the PCM or PCM mixture as well as other information such as thermal heat transfer, room temperature and the like. The capsules may also be equipped with safety features such as escape valves or reinforced ribs. A safety valve may allow escape of the PCM or PCM mixture or other contents of the capsule in the event of overheating. The reinforced ribs may provide additional structural integrity and strength to withstand any pressure the PCM or PCM mixture can exert on the capsule from the inside. The reinforce ribs may also protect the capsule from outside forces.
The number of capsules to use in a given environment will depend on the conditions of that environment. Any number of capsules of varying sizes and shapes can be provided in accordance with the intended use. As provided in Table 2, earlier, in exemplary embodiments, five capsules of 1 Kg PCM mixture each can provide a large enough amount of heat energy to properly heat a given space.
In exemplary embodiments, a holder can be provided to easily place, hold, carry and/or relocate one or more capsules. The holder can thus also be a portable structure. In exemplary embodiments, the holder and the capsules are each an independently portable structure. An exemplary embodiment of a holder is illustrated in FIG. 4. The holder 300 can include a handle 310 and a base 320.
The handle 310 can be of a fixed length. Alternatively, handle 310 can be a retractable handle that can be extended only when desired. At one end handle 310 can be connected to a handlebar 311. The handlebar 311 can make it easier for a user to grab the handle 310 when relocating the holder 300. At the opposite end from the handlebar 311, the handle 310 can be connected to a base 320. The connection between handle 310 and base 320 can be a permanent connection or a releasable connection. In exemplary embodiments, handle 310 can be detached from base 320.
Base 320 can be shaped and sized to hold one or more capsules. Each capsule can be secured to base 320 using one or more sockets 324. In exemplary embodiments, a socket 324 can be sized to fit one capsule. In alternative embodiments, base 320 includes only one socket 324 sized to fit multiple capsules. The one or more capsules can be mounted on socket 324 by a tight fit so as to keep the capsules in place. The socket 324 may also be equipped with one or more fasteners such as straps, clamps, fittings, magnets or the like to securely, yet releasably, hold the capsule.
For further structural integrity and safety, base 320 may also be equipped with one or more racks 323. A rack 323 can include a frame that surrounds the one or more capsules placed in the base. Rack 323 may also include rails, bars or like structure that individually surrounds each of the one or more of the capsules in the base 320. In exemplary embodiments, the rack 323 can be designed to be opened or loosened to allow for the insertion and extraction of the capsules.
Base 320 can further include its own handle 321. Handle 321 can extend from one side of the base to the other side. Handle 321 can be used as a typical bucket handle to carry the base 320. Handle 321 may further comprise a grip 322. The grip can be designed for easy handling and to secure a tight grasp of the handle.
In exemplary embodiments, the base 320 can also be equipped with one or more straps that can allow one to carry the base 320. The one or more straps can be designed to go around one's waist and/or over one's shoulders.
Base 320 may further include one or more wheels 325 or other motion mechanism that can allow the base 320 to more easily be moved about. In exemplary embodiments, the base 320 may also be equipped with motorized wheels. In yet alternative embodiments, the motorized wheels can be remote controlled. In exemplary embodiments, the base 320 can include a processor that can communicate wirelessly or via a wired connection with one or more controllers located in the one or more capsules. Through the use of controllers, the base 320 can be designed to move about a given space to better improve heating of the room.
Holder 300, including handle 310, base 320 and components therein can be made of any suitable materials for their intended use. In exemplary embodiments holder 300 does not include materials that would interfere or greatly interfere with the heat transfer to and from the PCM or PCM mixture inside the one or more capsules. Also, the material used for holder 300 and its components would preferably be one that can maintain structural integrity at least within the temperature range intended for operation. The holder 300 can be made of the same material as the one or more capsules 100. In alternative embodiments, the holder 300 is made of a material different from the one or more capsules 100. In an exemplary embodiment, at least handle 310, handlebar 311, socket 324, rack 323, and handle 321 are made of aluminum. Other materials such as steel, copper and brass may also be used to form holder 300.
In exemplary embodiments, the heating system disclosed herein can be set in a given space that is desired to be heated. For example, the holder 300 can be used to hold, for example five or six capsules. A PCM mixture, for example about 1 Kg of PCM mixture, can be poured into each capsule. Each capsule can, for example, have a volume of about 804 cm³thus leaving some headspace after the PCM mixture has been poured in. Each capsule can then be capped, such as by using a screw cap, to form a sealed contained. Each capsule can thus be provided to contain, for example, 1 Kg of PCM mixture. The PCM mixture can be, for example, a mixture of sodium sulfate decahydrate, sodium chloride, and a sodium polyacrylate. The portable heating system having one or more portable capsules, for example five or six capsules, can be set in the room while the room temperature is above the melting point of the PCM mixture, for example, above 18° C. The source of the heat in the room is not limiting to the invention. The heat can be ambient temperature due to weather conditions, solar energy, geothermal energy, or any other type of heat that can occur either naturally or artificially through heat generating means. In such an environment, the PCM mixture will heat up to a temperature above 18° C. and thus fully achieve a first state, for example a liquid state. The portable heating system can then remain in that location if that is the place to be heated, or it can be moved to an area that requires heating. As the temperature of the location in which the heating system is located drops to below 18° C., the PCM mixture will commence to release the energy stored and commence to change into a second phase, for example a solid phase. As the energy is released, it is transferred through the capsules' walls and into the surrounding environment, thereby warming the surrounding environment through convection heating. In so doing, the temperature of the surrounding environment will commence to increase. The maximum temperature the surrounding environment can achieve is the melting temperature of the PCM mixture, for example 18° C. Assuming no heat loss from the surrounding environment, the heating system is expected to function as an automatic thermostat maintaining the temperature at the melting temperature of the PCM mixture. The maximum amount of heat energy the heating system will be able to release is the amount of energy loss required for the PCM mixture to fully change to the second state, for example the solid state.
It will be apparent to those skilled in the art that various modifications and variation can be made in the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.

Claims

What is claimed is:

1. A heating device comprising:

a PCM mixture of sodium sulfate decahydrate, sodium chloride and sodium polyacrylate.

2. The heating device of claim 1, wherein the sodium sulfate decahydrate and the sodium chloride in the mixture are present at a 1:1 molar ratio.

3. The heating device of claim 1, wherein the PCM mixture includes about 2.5% wt of sodium polyacrylate.

4. The heating device of claim 1, further comprising at least one capsule housing the PCM mixture.

5. The heating device of claim 4, wherein the capsule is made of aluminum.

6. The heating device of claim 5, further comprising a holder having a base that houses the at least one capsule.

7. The heating device of claim 6, wherein the base further comprises at least one wheel.

8. The heating device of claim 6, further comprising a retractable handle connected to the base.

9. A portable heating device comprising:

a portable container;

a PCM mixture contained inside the portable container;

a holder for the portable container, the holder having a handle.

10. The portable heating device of claim 7, wherein the portable container is cylindrical.

11. The portable heating device of claim 7, wherein the portable container is made of aluminum.

12. The portable heating device of claim 7, wherein the PCM mixture comprises sodium sulfate decahydrate, sodium chloride, and a polyacrylate.

13. The portable heating device of claim 7, wherein the holder is made of aluminum.

14. A method of heating comprising:

placing one or more portable heating capsules into a room, each capsule containing a PCM mixture;

allowing the PCM mixture to absorb heat from the environment surrounding the one or more portable heating capsules while the environment is at a temperature above a melting temperature of the PCM mixture;

allowing the PCM mixture to release heat into an environment surrounding the one or more portable heating capsules when a temperature of the environment is below the melting temperature of the PCM mixture.

15. The method of claim 14, wherein at least five portable heating capsules are placed into a room.

16. The method of claim 14, wherein the PCM mixture comprises: sodium sulfate decahydrate, sodium chloride, and sodium polyacrylate.

17. The method of claim 14, wherein the one or more portable heating capsules are made of aluminum.