U.S. patent application number 13/385934 was filed with the patent office on 2013-09-19 for retrofittable tankless passive solar water heater.
The applicant listed for this patent is John David Grandinetti. Invention is credited to John David Grandinetti.
Application Number | 20130239951 13/385934 |
Document ID | / |
Family ID | 49156511 |
Filed Date | 2013-09-19 |
United States Patent
Application |
20130239951 |
Kind Code |
A1 |
Grandinetti; John David |
September 19, 2013 |
Retrofittable tankless passive solar water heater
Abstract
A tankless solar water heater for heating domestic pressurized
water having a flexible insulated heat exchanger housing that
contracts to accommodate volume reduction when the solar heating
fluid cools. A check valve releases gas and solar heating fluid if
interior pressure exceeds ambient pressure by more than one pound
per square inch, without admitting air into the container or the
heat exchanger when volume of the solar heating fluid reduces due
to cooling.
Inventors: |
Grandinetti; John David;
(Honolulu, HI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Grandinetti; John David |
Honolulu |
HI |
US |
|
|
Family ID: |
49156511 |
Appl. No.: |
13/385934 |
Filed: |
March 14, 2012 |
Current U.S.
Class: |
126/652 ;
126/663 |
Current CPC
Class: |
F24S 10/746 20180501;
F24S 80/54 20180501; Y02E 10/44 20130101; Y02B 10/20 20130101; F24S
10/45 20180501; F24S 60/30 20180501; Y02B 10/22 20130101 |
Class at
Publication: |
126/652 ;
126/663 |
International
Class: |
F24J 2/05 20060101
F24J002/05; F24J 2/24 20060101 F24J002/24 |
Claims
1. A tankless solar water heater for heating domestic pressurized
water, comprising: an insulated container, open at an upper end,
for solar heating and insulating a solar heating fluid; a flexible
insulated heat exchanger housing having heat exchange ports and a
check valve port, sealingly attached over said upper end, wherein
said check valve port is located at an uppermost location of said
heat exchanger housing; a check valve sealingly mounted in said
check valve port; heat exchanger tubing at least partially
contained within said heat exchanger housing, sealingly extending
through said heat exchange ports to exchange heat between said
solar heating fluid and said domestic pressurized water circulating
through said heat exchanger tubing when said solar heating fluid
fills said insulated container and said heat exchanger housing;
wherein said check valve releases air, and said solar heating fluid
and any gas therefrom, in said container and said heat exchanger
housing, when interior pressure in said container and said heat
exchanger housing is greater than approximately 1 pound per square
inch above ambient pressure, without admitting air into said
container or said heat exchanger housing when said interior
pressure is less than said ambient pressure due to volume reduction
of said solar heating fluid from cooling; wherein said heat
exchanger housing contracts to accommodate said volume reduction of
said solar heating fluid from cooling; and wherein said container
and said flexible heat exchanger are sufficiently insulated to
reduce cooling of said solar heating fluid in said heat exchanger
housing to 1 degree Fahrenheit per hour at 130 degrees
Fahrenheit.
2. A tankless solar water heater according to claim 1, wherein said
insulated container comprises an outer rigid transparent tube and
an inner opaque tube, with an insulating vacuum in the space
between said tubes.
3. A tankless solar water heater according to claim 1, wherein said
solar heating fluid comprises water.
4. A tankless solar water heater according to claim 1, wherein said
heat exchanger tubing is entirely contained within said heat
exchanger housing.
5. A tankless solar water heater according to claim 1, wherein said
check valve releases said solar heating fluid and any gas therefrom
if interior pressure in said container and said heat exchanger
housing exceed ambient pressure by more than one pound per square
inch, to minimize air and gas from said solar heating fluid in said
container and said heat exchanger housing, and to maintain said
interior pressure of said solar heating fluid in said container and
said heat exchanger housing at a maximum pressure of one pound per
square inch above ambient pressure.
6. A tankless solar water heater according to claim 1, wherein said
check valve vents said solar heating fluid and gas therefrom in
case of boiling.
7. A tankless solar water heater for heating domestic pressurized
water, comprising: a plurality of insulated solar heating tubes,
each having an upper end, for solar heating and insulating a solar
heating fluid contained therein; a flexible insulated heat
exchanger housing having heat exchange ports and a check valve
port, sealingly attached over each of said upper ends, wherein said
check valve port is located at an uppermost portion of each of said
heat exchanger housings; a check valve sealingly mounted in each of
said check valve ports; and heat exchanger tubing mounted at least
partially within each of said heat exchanger housings, each
sealingly extending through said heat exchanger ports; said heat
exchanger tubing in each of said heat exchanger housings being
connected in series with heat exchanger tubing in another of said
heat exchanger housings; whereby when solar heating fluid fills
said insulated tubes and said heat exchanger housings, heat is
exchanged between said solar heating fluid and said domestic
pressurized water circulating through said heat exchanger tubing;
whereby said flexible heat exchanger housings contract to
accommodate volume reduction when said solar heating fluid cools;
whereby said check valves release said solar heating fluid and any
gas therefrom if interior pressure in said tubes and said heat
exchanger housing exceed ambient pressure by more than one pound
per square inch, without admitting air into said tubes or said heat
exchanger when volume of said solar heating fluid reduces due to
cooling, to minimize air and gas from said solar heating fluid in
said tubes and said heat exchanger housings, to maintain said
interior pressure of said solar heating fluid in said tubes and
said heat exchanger housings at a maximum pressure of one pound per
square inch above ambient pressure, and to vent said solar heating
fluid and gas therefrom in case of boiling; and wherein said tubes
and said flexible heat exchangers are sufficiently insulated to
reduce cooling of said solar heating fluid in said heat exchanger
housing to 1 degree Fahrenheit per hour at 130 degrees
Fahrenheit.
8. A tankless solar hot water heater according to claim 3, wherein
said heat exchanger tubing comprises approximately 10 feet of 1/2
inch copper tubing in at least two loops, each approximately 20
inches long and approximately 3 inches wide.
9. A tankless solar water heater according to claim 3, wherein each
of said solar heating tubes comprises a transparent outer tube and
an opaque inner tube, with a vacuum between said inner tube and
said outer tube.
10. A tankless solar water heater for heating domestic pressurized
water, comprising: an insulated solar heating means, having an
upper end, for solar heating and insulating a solar heating fluid
contained therein; a flexible insulated heat exchanger housing
means having heat exchange ports and a check valve port sealingly
attached said upper end, wherein said check valve port is located
at an uppermost location of said heat exchanger housing, for
insulating said solar heating fluid contained therein and for
contracting to accommodate volume reduction when said solar heating
fluid cools; heat exchanger means mounted within said heat
exchanger housing means, sealingly extending through said heat
exchanger ports, for exchanging heat between solar heating fluid in
said heat exchanger means and domestic pressurized water
circulating through said heat exchanger means when said solar
heating fluid fills said insulated tubes and said heat exchanger
means; a check valve means sealingly mounted in said check valve
port for releasing air and said solar heating fluid and any gas
therefrom if interior pressure in said solar heating means and said
heat exchanger housing means exceeds ambient pressure by more than
one pound per square inch, without admitting air into said solar
heating means or said heat exchanger means when volume of said
solar heating fluid reduces due to cooling, whereby air and gas
from said solar heating fluid in said solar heating means and said
heat exchanger housing means is minimized, whereby said interior
pressure of said solar heating fluid in said solar heating means
and said heat exchanger housing means is maintained at a maximum
pressure of one pound per square inch above ambient pressure, and
whereby any gas from boiling of said solar heating fluid is vented
in case of boiling; and wherein said solar heating means and said
heat exchanger housing means are sufficiently insulated to reduce
cooling of said solar heating fluid in said heat exchanger housing
means to 1 degree Fahrenheit per hour at 130 degrees Fahrenheit.
Description
TECHNICAL FIELD
[0001] The present invention relates to a solar water heater for
heating pressurized domestic water that does not require a separate
large capacity hot water storage tank that occupies valuable living
space; is passive because it does not have any pumps or other
moving parts in normal operation, so that service life is
increased; and is retrofittable to use any smaller capacity hot
water tank from an existing electrical, gas, or other non-solar
domestic hot water heater.
BACKGROUND ART
[0002] In most developed countries, domestic water is required to
be pressurized by a central utility so that water flows through
pipes when a faucet is turned on. In conventional solar hot water
systems, domestic water is heated during the day by being pumped
(using a separate circulation pump) up to a solar panel on the roof
of a house, where it is heated, and then the heated water returns
to the house through insulated pipes, and is stored in a large
capacity insulated tank for future use, usually at night. This
insulated solar hot water tank must be of large capacity because
the solar panel only heats water during the day, when the sun is
shining, and does not heat water at night. This hot water tank
typically has a capacity based on expected hot water usage of 20
gallons for the first person, and 15 gallons per each additional
person in the household. Because of this size requirement, typical
solar hot water tanks have a capacity of 80 gallons or higher.
Solar hot water tanks eventually corrode, often in less than 10
years, and when they leak, large quantities of water are released
into the house, causing damaging flooding. Further, because of the
need for insulation and large capacity, conventional solar hot
water tanks occupy a large amount of valuable living space.
[0003] In conventional solar hot water systems, the panels on the
roof are not well insulated, so that they cool down at night. In
the morning, the panels are cold, and therefore cannot heat
water.
[0004] One problem with designing solar hot water systems is that
water expands when heated: 5 gallons of water increases by 1 pint
in volume from a 100 degree Fahrehnheit rise in temperature. The
maximum temperature in a properly operating solar heating system is
about 180 degrees Fahrenheit, so this increase in volume can easily
occur from the coldest temperature at dawn to the highest
temperature in the afternoon.
[0005] A conventional non-solar hot water system typically uses
electricity or natural gas to heat up water that is then stored in
a small capacity tank. For example, common sizes for the tanks of
conventional electric or gas water heaters are 30, 40 or 50
gallons. Because the heater can be turned on at any time (instead
of heating only during the day, as is the case with solar heating),
a conventional water heater can be turned on to heat more water
when the water in the tank becomes colder. Thus, when a
conventional solar water heater replaces a conventional non-solar
hot water system, both the non-solar heater and the existing small
capacity tank must be replaced, and a large insulated solar hot
water tank must be installed instead. Usually the solar hot water
tank is twice or three times the capacity of the existing small
capacity tank, so different or additional storage space within the
house must be found. Further, the cost for replacing a solar hot
water tank is usually at least twice the cost for replacing a
conventional heater's tank, due to the greater size and need for
specialized solar contractor to perform the replacement (normal
plumbers can replace conventional hot water heater tanks).
[0006] There are also tankless electric or gas heaters that can
heat sufficient water instantaneously so that no storage tank is
necessary.
[0007] Some companies combined solar water heaters (using
conventional solar hot water storage tanks) with gas or electric
tankless water heaters. For example, Bosch sold the Aquastar 1600PS
propane solar tankless water heater to receive preheated water from
a conventional solar heating system having a conventional solar hot
water tank.
[0008] U.S. Pat. No. 980,505 to Emmet discloses a series of tubes
with vacuum chamber jackets placed side by side, connected at their
open ends to a chambered header through which fluid flows into and
out of the tubes, absorbing heat as it goes. Page 2, lines 77-79,
state that it is difficult to make an air-tight joint or seal
between a metal vessel and an outer glass envelop.
[0009] U.S. Pat. No. 4,018,215 to Pei discloses a manifold for a
solar energy collector assembly in which the working media is a
liquid circulated through several tubular collectors in series.
Col. 1, lines 48-54, indicate thermal expansion differences cause
failure in glass to metal seals. FIGS. 7 and 8 show a single-acting
manifold.
[0010] U.S. Pat. No. 4,033,327 to Pei discloses a solar energy
collector apparatus having several double-wall glass tubular
elements connected on opposite sides of an elongated module. The
elements are sealed in oppositely facing metal cups and inside the
opposite elements is a cross supply tube. The cups are connected by
conduits for flow of a liquid through the collectors.
[0011] U.S. Pat. No. 4,043,318 to Pei discloses over-sized test
tubes having inner and outer walls, with the space between
evacuated. A working fluid circulates and is heated. Several of
these energy collectors are connected into a manifold for
circulation of working fluid.
[0012] U.S. Pat. No. 4,212,293 to Nugent discloses a solar energy
collector apparatus in which several double-wall glass tube
collectors, each with vacuum jacket, depend from opposite sides of
an elongated manifold. Several modules are inter-connectable to
desired capacity for a particular solar powered heating or cooling
system.
[0013] U.S. Pat. No. 4,440,156 to Takeuchi discloses a solar heat
collector including inner and outer substantially straight tubes
being closed at one end and open at the other end sealed at their
open ends with the space therebetween being evacuated. A hairpin
pipe for circulation of fluid media is disposed within the inner
tube and includes two substantially straight sections wherein both
or at least one is in surface contact with the inner surface of the
inner tube.
[0014] U.S. Pat. No. 4,554,908 to Hanlet discloses an
electromagnetic energy collector assembly in which a cylindrical
glass tube I sealed under vacuum at one end to an inner cylindrical
energy absorber having a plurality of grooves on the exterior
surface.
[0015] U.S. Pat. No. 5,931,156 to Wang discloses a heat-pipe type
solar collector that includes a heat absorber portion adapted to
absorb solar energy to evaporate a working fluid in heat tube
elements; and heat release portion communicating with the heat
absorber portion and having a body of a semi-annular or annular
cross-section. At night, the working fluid portion flows to the
heat absorber portion to generate a vacuum for heat insulating
purposes, thereby maintaining the temperature in the water
reservoir.
[0016] Dewars type vacuum tubes are tubes that are placed one
within the other, joined at the neck, with the space between the
tubes being evacuated.
[0017] However, the inventor is not aware of a tankless passive
solar water heater retrofittable to an existing domestic hot water
system using Dewars type large diameter vacuum tubes.
[0018] Accordingly, it is an object of this invention to provide a
solar water heater that avoids the need for a separate solar hot
water storage tank.
[0019] It is a further object of this invention to provide a solar
water heater that is passive, that is, has no moving parts during
normal operation, to provide a longer service life.
[0020] It is a still further object of this invention to provide a
solar water heater that is retrofittable to use a preexisting
conventional non-solar water heater and its small capacity
tank.
[0021] It is a still further object of this invention to avoid the
difficulties with existing glass to metal vacuum tubes,
specifically the problem of maintaining a vacuum between materials
with different thermal expansions.
DISCLOSURE OF THE INVENTION
[0022] The above and other objects are achieved by a tankless solar
water heater that includes an insulated container (open at an upper
end), for solar heating and insulating a solar heating fluid; a
flexible insulated heat exchanger housing sealingly attached over
the upper end; a check valve (a one way valve that allows fluid or
air to escape, but not to enter) sealingly mounted at an uppermost
location in the heat exchanger housing; and heat exchanger tubing
at least partially contained within the heat exchanger housing,
sealingly extending through heat exchange ports in the heat
exchanger housing to exchange heat between the solar heating fluid
and domestic pressurized water circulating through the heat
exchanger tubing. The check valve releases air (and the solar
heating fluid and any gas therefrom) when interior pressure in the
container and the heat exchanger housing is greater than
approximately 1 pound per square inch above ambient pressure,
without admitting air into the container or the heat exchanger when
the interior pressure is less than the ambient pressure due to
volume reduction of the solar heating fluid from cooling. The heat
exchanger housing contracts to accommodate the volume reduction of
the solar heating fluid from cooling. The container and the
flexible heat exchanger are sufficiently insulated to reduce
cooling of the solar heating fluid in the heat exchanger housing to
1 degree Fahrenheit per hour at 130 degrees Fahrenheit.
[0023] Preferably, the insulated container comprises an outer rigid
transparent tube and an inner opaque tube, with an insulating
vacuum in the space between the tubes, commonly called an all glass
solar vacuum tube, or a Dewar's type vacuum tube solar
collector.
[0024] Preferably, the heat exchanger tubing is entirely contained
within the heat exchanger housing.
[0025] Preferably, also, the check valve vents the solar heating
fluid and gas therefrom in case of boiling.
[0026] In a preferred embodiment, the invention has a plurality of
insulated solar heating tubes, preferably eight, each with a
flexible insulated heat exchanger housing sealingly attached over
each of the upper ends, with a check valve sealingly mounted in the
uppermost portions of the heat exchanger housings.
[0027] Heat exchanger tubing is mounted at least partially within
each of the heat exchanger housings, with the heat exchanger tubing
being connected in series between heat exchanger housings. In this
manner, when solar heating fluid filling the insulated tubes and
the heat exchanger housings is heated by the sun, heat is exchanged
between the solar heating fluid and domestic pressurized water
circulating through the heat exchanger tubing. The flexible heat
exchanger housings contract to accommodate volume reduction when
the solar heating fluid cools at night, and the check valves
releases solar heating fluid and any gas therefrom if interior
pressure in the tubes and the heat exchanger housings exceeds
ambient pressure by more than one pound per square inch, without
admitting air into the tubes or the heat exchangers when volume of
the solar heating fluid reduces due to cooling. The tubes and heat
exchangers are sufficiently insulated to reduce cooling of the
solar heating fluid in the heat exchanger housing to 1 degree
Fahrenheit per hour at 130 degrees Fahrenheit.
BRIEF DESCRIPTION OF DRAWINGS
[0028] FIG. 1 is a perspective exploded view of a presently
preferred embodiment of the present invention.
[0029] FIG. 2 is a side elevational view of a vacuum tube according
to the presently preferred embodiment of the present invention.
[0030] FIG. 3 is cutaway view of the vacuum tube of FIG. 2 along
the line A-A.
[0031] FIG. 4 is an exploded perspective view of a heat exchanger
housing and heat exchanger according to the presently preferred
embodiment of the present invention.
[0032] FIG. 5 is a side cutaway view of a presently preferred
embodiment of the check valve of the present invention.
[0033] FIG. 6 is a side elevational view of the vacuum tube of FIG.
2, the heat exchanger housing and heat exchanger of FIG. 4, and the
check valve of FIG. 5, in assembled configuration.
[0034] FIG. 7 is a top end view of the series of heat exchanger
housings on the vacuum tubes depicted in FIG. 1.
[0035] FIG. 8 is a perspective assembled view of the presently
preferred embodiment of the present invention.
BEST MODE FOR CARRYING OUT THE INVENTION
[0036] Referring to FIG. 1, shown is a perspective exploded view of
the presently preferred embodiment of a tankless solar water heater
according to the present invention 10, comprising eight cylindrical
vacuum tubes 20 with flexible heat exchanger housings 30 sealingly
attached to the upper ends 22 of each of the vacuum tubes 20.
Preferably, the heat exchanger housings 30 are received, aligned,
and retained in position in an insulated box 40 lined with
polyurethane, fiberglass, or other insulating material (not shown)
with an insulated lid 48. Preferably also, the lower ends 24 of the
vacuum tubes 20 are received, aligned, and retained in position by
a preferably aluminum bottom support holder 60 (comprising a base
62 and top 64, with split rubber hose bushings 66 and 68 to hold
the vacuum tubes), and covered by a bottom cover 70. The bottom
support bracket 60 and box 40 are preferably joined together by
angle members 80.
[0037] Referring to FIG. 2, shown is a side elevational view of a
vacuum tube 20, comprising a transparent outer tube 22 and a
coaxial opaque, preferably black (with a radiant energy absorbing
coating) inner tube 24. The space 26 between the outer tube 22 and
inner tube 24 is evacuated, to provide thermal insulation for the
inner tube 24. Preferably the inner tube 24 has a capacity of
approximately 3.5 gallons.
[0038] Referring to FIG. 3, shown is an end cutaway view of the
vacuum tube of FIG. 2 along the line A-A. As can be seen, the inner
tube 24 is coaxial with the outer tube 22, and the space 26 between
them is evacuated.
[0039] Referring to FIG. 4, shown is an exploded perspective view
of a heat exchanger housing 30 and heat exchanger tubing 32
according to the presently preferred embodiment of the present
invention. An adapter end plate 90, preferably of stamped brass, is
preferably sealingly attached to the upper end 34 of the heat
exchanger housing 30 (see FIG. 6), and has two heat exchanger ports
92, a check valve port 94, and an optional fill port 96 (which is
plugged, capped or otherwise closed after the heating fluid fills
the entirety of inner tube 24 and the heat exchanger housing 30,
with any dissolved or entrained air later being released through
the check valve as described below). The heat exchanger housing 30
must be made of a flexible material, such as silicon, to be able to
expand and contract to accommodate changes in volume due to heating
and cooling, as described below.
[0040] Preferably the heat exchanger housing 30 is approximately 20
inches long and has a capacity of approximately 1.5 gallons, so
that each combination of a vacuum tube 20 and heat exchanger
housing 30 has a combined capacity of approximately 5 gallons. This
will provide the ability to accommodate a change in volume of
approximately 1 pint for the 5 gallons. Preferably the heat
exchanger housing 30 is cylindrical and made from extruded
silicone, not press molded, in order to provide easier collapsing
or puckering when the volume of solar heating fluid cools down and
contracts. The heat exchanger tubing 32 is preferably made of
copper and is bent into two or three loops, with two preferred, to
reduce costs.
[0041] Preferably each heat exchanger housing 30 contains
approximately 10 feet of heat exchanger tubing 32, holding about
0.1 gallon. The ends of the heat exchanger tubing 36 extend through
the heat exchanger ports 92, as shown in FIG. 6.
[0042] Referring to FIG. 5, shown is a side cutaway view of a
presently preferred embodiment of the check valve 100 of the
present invention. As can be seen, a copper pipe nipple 104 is
brazed to and extends outwardly through the check valve port 94 in
the upper portion 102 of the adapter end plate 90 shown in FIG. 4.
Although not shown, a similar copper pipe nipple is brazed to and
extends outwardly through the fill port 96, and the ends of the
heat exchanger tubing 36 are also brazed to and extend through the
heat exchanger ports 92 by approximately the same distance as the
pipe nipples. Preferably, a silicone insert 106 is placed inside
the nipple 104 to retain a check valve 110, which has a barb end
112. As can be seen, the barb end 112 is inserted and retained in
the silicone insert 106. Inside the check valve 110, a chamber 114
contains an O ring at the bottom, and contains a stainless steel
spring 116 that biases a stainless steel ball 118 against the O
ring 119 to seal off the check valve 110. If pressure inside the
vacuum tube 20 and heat exchanger housing 30 overcomes the bias of
the stainless steel spring 116, then the contents of the heat
exchanger housing (air, the solar heating fluid (preferably water)
and gas from the solar heating fluid (preferably water vapor)) are
vented through the purge outlet 118. Preferably the stainless steel
spring 116 and stainless steel ball 118 are selected so that the
check valve 110 releases air, water and water vapor through the
purge outlet 118 when the interior pressure in the vacuum tube 20
and the heat exchanger housing 30 is greater than approximately 1
pound per square inch above ambient pressure, without admitting air
into the vacuum tube 20 or the heat exchanger housing 30 when the
interior pressure is equal to or less than the ambient pressure due
to volume reduction of the solar heating fluid, as described
below.
[0043] Referring to FIG. 6, shown is a side elevational view of the
vacuum tube 20, the heat exchanger housing 30, heat exchanger
tubing 32, and check valve 100, in assembled configuration, showing
the outer transparent tube 22, the inner opaque tube 24, the
evacuated space 26 between those tubes to form a vacuum, the heat
exchanger housing 30, the heat exchanger tubing 32 (illustrated
with only two loops in this embodiment), the heat exchanger ports
36, and the adapter end cap 90, showing the heat exchanger ports
92, check valve port 94 and optional fill port 96. The adapter end
cap 90 is retained inside the heat exchanger housing 30 by a
stainless steel clamp 97. As can be seen, the heat exchanger
housing 30 overlaps the upper portion 22 of the vacuum tube 20 and
is then clamped by a stainless steel clamp 120. The inner tube 24
is joined to the outer tube 22 at a lip 28. Preferably the inner
diameter of the inner opaque tube 24 is approximately 3.5 inches
and the outer diameter of the outer transparent tube is
approximately 4.75 inches.
[0044] Referring to FIG. 7, shown is a top end view of the heat
exchanger housings 30 on the top ends of the series of vacuum tubes
20 (not shown). As can be seen, the ends 36 of the heat exchanger
tubing 32 (not shown) extending from the heat exchanger ports 92
are connected in series, so that water circulates through all of
the heat exchanger tubing of each heat exchanger housing 30.
[0045] Referring to FIG. 8, shown is a perspective assembled view
of the presently preferred embodiment of the present invention,
which shows more clearly how the heat exchange tubing 32 of each of
the heat exchange housings 30 is connected in series, and how each
heat exchange housing 30 is clamped onto each vacuum tube 20 with a
stainless steel clamp 120, and how the adapter end plates 90 are
retained inside the top end of the heat exchanger housings 30 by
stainless steel clamps 97.
[0046] Operation of the tankless water heater of the present
invention will now be explained. After assembly of all the
components of the embodiment 10 shown in FIG. 1, each of the inner
tubes 24 and heat exchange housings 30 is completely filled with a
heating fluid, preferably water, optionally through fill ports 96.
The tankless solar water heater is then placed in the sun at an
appropriate orientation for maximum solar exposure, and with the
check valves 100 at the highest points. The pressurized domestic
water supply is then connected to the ends of the series-connected
heat exchanger tubing 32, so that the domestic water circulates
through the heat exchanger tubing 32 under the normal domestic
pressure. Thus, no pump is necessary, so that the system is not
vulnerable to shutdown because of a pump failure.
[0047] The radiant energy of the sun will heat the opaque inner
tubes 24, which will heat the solar heating fluid inside, up to a
maximum of approximately 180 degrees Fahrenheit. Preferably, an
optional anti-scalding valve is provided to prevent water of this
maximum temperature from entering the shower, bath, sink or other
fixture. The transparent outer tubes 22 form a vacuum 26 around the
opaque inner tubes 24, so that the solar heating fluid is insulated
against heat loss, much like a Thermos bottle. Because heat rises,
the heated solar heating fluid will rise to the top of the vacuum
tubes 20 and into the heat exchanger housings 30. Initially, this
heating will drive out air that has been entrained in the solar
heating fluid, which will then create outward pressure on the check
valve 100, which overcomes the urging of the stainless steel spring
116 and stainless steel ball 118 against the O ring 119. The air
will then vent through the purge outlet 118. The solar heating
fluid will also expand as it heats up, and may also generate gas,
and this will similarly be vented through the purge outlet. After
the solar heating fluid reaches its maximum temperature of about
180 degrees Fahrenheit, it will start to cool down when the sun
starts to go down. This cooling will cause the solar heating fluid
to contract, which will create negative pressure in the vacuum tube
20 and heat exchange housing 30. This negative pressure will urge
the stainless steel ball 118 against the O ring 119 even more
strongly, so that the check valve 100 will close even tighter.
Because the heat exchanger housing 30 is flexible, it will contract
by puckering inward to accommodate the volume reduction caused by
this cooling.
[0048] After perhaps a few weeks of operation, all entrained air
and excess solar heating fluid will be driven out of the vacuum
tube 20 and heat exchanger housing 30 by the expansion from the
maximum temperature achieved. The check valve 110 will then
effectively remain shut indefinitely, and the heat exchange housing
30 should now fill to its maximum capacity only when it again
achieves the highest temperature. At this point, the system is
completely closed to the atmosphere, except that, in the unlikely
event of boiling of the solar heating fluid, the check valve 100
will open.
[0049] The heat exchanger tubing 32 is preferably connected in
series, so that domestic hot water flows through approximately 10
feet of heat exchanger tubing, therefore becoming heated almost
instantaneously.
[0050] This construction allows the elimination of a solar hot
water tank because the vacuum tubes 20 and heat exchanger housings
30 are insulated, so they maintain the temperature of the solar
heating fluid for much longer than conventional uninsulated solar
panels. Heat loss at the maximum temperature of 180 degrees
Fahrenheit will occur at a rate of about 2 degrees Fahrenheit per
hour. Thus, from the maximum daytime temperature of about 180
degrees Fahrenheit, usage for heating water will cause the solar
heating fluid to cool to about 130 degrees Fahrenheit in the
evening. This is still a very substantial temperature, because the
maximum temperature desired to avoid scalding is about 120 degrees
Fahrenheit.
[0051] At a temperature of about 130 degrees Fahrenheit, the solar
heating fluid will cool at about 1 degree Fahrenheit per hour.
Thus, even throughout the night, the solar heating fluid will
maintain a satisfactory temperature. At this rate, by the time the
solar heating fluid cools down below 100 to 120 degrees
Fahreneheit, which is quite usable for domestic hot water purposes,
the sun will rise and warm the solar heating fluid again. Indeed,
the US Consumer Products Safety Commission's Document 5098 entitled
"Tap Water Scalds" recommends that hot water heaters be set to a
maximum temperature of 120 degrees Fahrenheit, but points out that
a five minute exposure to water at this temperature could result in
third degree burns.
[0052] Without a flexible, high temperature housing and check
valve, it would be necessary to incorporate external expansion
tanks, float valves and pressure relief valves for operation. In
areas where the temperature can fall below freezing, these exterior
components could freeze or suffer freeze damage.
[0053] Although a single set of 8 vacuum tubes can be used, it is
preferred that 2 or 3 sets of 8 tubes each be used in households
with 2 or more people.
[0054] This construction is advantageous for servicing, because the
components are all individually replaceable. For example, if a
vacuum tube 20 breaks, if a heat exchanger housing 30 fails, or if
heat exchanger tubing 32 leaks, each can be quickly removed and
replaced. The adapter end cap 90 and check valve 100 are removable
as well.
[0055] The construction is low profile and provides very good
weight distribution for support on roof structures.
[0056] This invention is preferably retrofittable to existing
conventional non-solar hot water heaters, using their existing
smaller capacity tanks for additional solar hot water storage, and
their electrical or gas heaters as backup heaters for prolonged
cloudy periods. In this arrangement, solar heated water from the
invention would flow into the existing tank and would be usable
directly. Because the water heats almost instantaneously in the
series-connected heat exchanger tubing 32, as described above, the
invention can continue to heat water as long as the working fluid
(preferably water) in the vacuum tubes 20 and heat exchanger
housings 30 remains hot enough. As explained above, the fluid in
the vacuum tubes 20 and heat exchanger housings 30 remains hot
enough overnight, until the sun heats them again. If, however,
there is a prolonged period of cloudy weather, then the existing
heater can warm the water in the tank.
[0057] Further, this invention can supply solar preheated water
into the tank of an existing conventional non-solar hot water
heater, which can dilute the preheated water's temperature to
reduce the chance of scalding, and also act as a backup in case
there are prolonged cloudy periods that prevent adequate solar
heating. It is preferred that the aggregate capacity of all the
vacuum tubes 20 and heat exchanger housings 30 be approximately
twice as much as the capacity of the conventional heater's
tank.
[0058] While the present invention has been disclosed in connection
with the presently preferred best mode described herein, it should
be understood that the best mode includes words of description and
illustration, rather than words of limitation. There may be other
embodiments which fall within this spirit and scope of the
invention as defined by the claims. Accordingly, no limitations are
to be implied or inferred in this invention except as specifically
and as explicitly set forth in the claims.
INDUSTRIAL APPLICABILITY
[0059] This invention is applicable whenever it is desired to
provide solar heating of water without using a solar hot water
tank.
* * * * *