Thermal energy storage unit

The disclosure is of a thermal storage assembly comprising a housing in which are mounted a plurality of plastic containers of chemical salts of a type which can store thermal energy. Separators are provided to space the containers from each other, and a source of vapor is provided to maintain a vapor pressure in the housing which in turn maintains the moisture content of the salts in the containers.

BACKGROUND OF THE INVENTION 
The present invention relates to thermal energy (heat or cold) storage 
devices, especially for solar systems, which generally comprise huge 
containers of rocks; smaller, but still large, containers of water; or 
still smaller housings of metal tubes which contain chemicals which can 
absorb and give up heat as the system operates. For strength and to 
provide the desired self-support, these metal tubes must be relatively 
thick-walled so that they are too expensive for widespread use. 
Many advantages would accrue if the industry could use thin sheets of 
plastic as containers for thermal storage chemicals. One proposed 
structure uses individual plastic tubes as chemical carriers. However, no 
simple and inexpensive support means is known for such individual tubes. 
An improved thermal storage system using plastic chemical carriers is 
described and claimed in copending application Ser. No. 920,962, filed 
June 30, 1978 now U.S. Pat. No. 4,287,942 granted Sept. 8, 1981. This 
application describes various basic concepts in plastic chemical carriers 
and support therefor, and the invention described herein relates generally 
to improvements in this basic invention.

DESCRIPTION OF THE INVENTION 
A thermal energy storage apparatus 10, especially for use in solar energy 
systems, is shown in FIG. 1 and includes a housing 20 of any suitable 
material having an inner storage area 30, an air transport pipe 40 at its 
upper end which comes from the solar collector (not shown) which is 
exposed to the sun at a remote location, and an air outlet pipe 50 at its 
upper end which goes to the building area to be heated. A pipe 52 returns 
to the solar collector. An air inlet pipe 60 is at the bottom of the 
housing and is a return pipe from the building area. Controllable dampers 
64 are provided as required. Any suitable air flow arrangement may be 
used, as will be understood by those skilled in the art. 
The housing 20 contains a plurality of thermal storage units 80 and, as 
described in the above-mentioned application, the storage units are made 
up of sheets 90 of synthetic resinous material, such as polypropylene, 
which may have a thickness of as little as about 5 mils or so, secured 
together to form parallel tubular pockets 100 in which chemical salts 101 
(FIGS. 2 and 3) are packed. The ends of the pockets are sealed to hold the 
salts in place in the pockets. The salts are of a type which can absorb, 
store, and give up thermal energy. The tube sheets 90 are preferably 
coated with an impervious layer 102 (FIG. 3) of paint, such as aluminum 
paint, or other material to retain moisture within the pockets 100. 
The storage units 80 are secured at their upper ends to horizontal rods 104 
which themselves are suitably supported on opposite side walls 22 and 24 
of the housing 20. The storage units 80 are parallel to each other and 
hang vertically. 
The storage units 80 are positioned so that, considering adjacent units, 
the tubular pockets 100 of one are disposed adjacent to the spaces 110 
between two tubular pockets of the adjacent unit. Thus, a sinuous laminar 
air flow path is provided upwardly, or downwardly, as desired, through the 
housing between each pair of storage units, and this provides optimum air 
turbulence and thermal transfer between the flowing air through the sheets 
90 and the chemical salts in the pockets 100 of the storage units. 
According to one aspect of the invention, the thermal storage units 80 are 
maintained properly spaced from each other by means of spacers disposed 
between the storage units. In one arrangement, the spacers comprise 
strings or ropes 120 (FIG. 1) disposed between the storage units. One or 
more of the strings 120 may be provided, and they may be secured to the 
rods 104 and hang downwardly therefrom. If desired, the spacers may 
comprise integral ribs 121 formed in the walls of the storage units 
transverse to the pockets, as shown in FIG. 3. 
According to another aspect of the invention, means are provided for 
maintaining a pressure of water vapor in the housing 20 to prevent 
moisture loss from the salts in the storage units 80. In one suitable 
arrangement, this means comprises a plurality of apertured pipes 130 
disposed horizontally parallel to and above the support rods 104 and 
positioned to provide a spray or mist of water or other fluid in the 
housing between the heat storage units. In one arrangement, the water 
pipes 130 are disposed between the support rods 104. In another 
arrangement, the support rods themselves may be the apertured water pipes, 
or both arrangements may be used in combination. 
The water pipes 130, whatever arrangement is used, are coupled to a 
suitable manifold 134 and to an inlet pipe 140, to which a pump 150 is 
coupled and to a collector or reservoir 160 disposed on the floor of the 
housing to collect any water which condenses in the housing. An inlet 
water pipe 170 is connected to the reservoir to admit water thereto from a 
water source, and, if desired, a level control 180 is provided in the 
reservoir 160 in conjunction with the inlet water pipe. 
An optional air guide member is provided in the housing, and this member 
comprises a large-area flat duct 190 disposed horizontally above the 
reservoir 160 and beneath the storage units 80 and having the air inlet 
pipe 60 coupled to one end thereof. The duct 190 includes large-area top 
and bottom plates or walls 192 and 194, the top plate having a plurality 
of apertures 196, through which air flows. The bottom plate also includes 
apertures 196 so that condensed fluid in the duct can fall into the 
reservoir 160. 
The water spray is represented by numeral 123. 
In a modification of the invention, illustrated schematically in FIG. 5, 
the fluid spray is not employed, but the housing 20 is filled with water 
200 or other fluid in which the storage units 80 are embedded. The fluid 
200 is circulated through the thermal collection and distribution system 
to provide the desired thermal distribution from sun to home. 
In a modification of the storage units 80, thermal conductivity may be 
improved by including, in the chemical salts, metal particles or mesh 202 
of aluminum or the like as illustrated in FIG. 3. Also, any suitably 
shaped metal insert 204 (FIG. 2) may be included with salt. 
In a modification of the invention, the elongated spacers 120 are made of a 
flexible material such as rubber, or some kind of synthetic material. For 
optimum operation, perhaps three such straps should be provided, one near 
each edge of the assembly of tubes and one generally in the middle, as 
shown in FIG. 6. 
Using a flexible material for the spacers 120 has the advantage that the 
spacers conform closely to the surfaces of the pockets 100 in the units 80 
and thus insure optimum heat transfer, with minimal lateral losses up and 
down the unit 80. The flexible spacers 120 may be circular in 
cross-section or have any other suitable cross-section. 
In addition, each salt-carrying unit 80 may carry a stiffening rod 211 in a 
pocket at its upper end, and the upper end of each unit may be provided 
with strap loops 213 which can be placed around pegs 215 provided in the 
upper end of the housing 20 in which the units 80 are supported. The strap 
loops 213 support the units 80.