FR2521270A1 - Variable volume hot water storage for solar heater - uses variable volume tank with the entry of cold water controlled by a solenoid valve which is operated by a water temperature transducer - Google Patents

Abstract

A variable water volume is established to maintain the water at constant temperature, and prevent the admission of cold water if the stored water temp. is not sufficiently high. The upper surface of the tank (2) has for its upper surface (1) a piston or membrane. A solenoid valve (4) is used to control water entry into the tank, and is controlled (3) by the temp. of the water. When the water is hot the solenoid valve admits more cold water, this process continuing while heating energy is available or until the maximum tank capacity is attained. When energy is no longer available there is no more cold water admitted when hot water is drawn off. A tap (9) can be used to bypass the solenoid valve to get the system started from cold.

Description

 The present invention relates to hot water tanks (water heaters, bath heaters according to their name). It is interesting mainly with the use of discontinuous energies such as solar which will be taken as an example.

 In the current state of the art (fig. 1) a water tank (2) is heated by a primary circuit. This primary circuit is composed of a solar collector (6) and a heat exchanger (7). The liquid contained in the primary circuit heats up in the collector thanks to solar radiation then will cool in the exchanger by yielding its calories to contained in the balloon.

 During periods when the energy received by the collectors is low (winter, spring, autumn) the contents of the tank are fully heated but the temperature inside the tank rises only a few degrees.

Let us take for example a balloon of two hundred liters whose water is at 80 celoius at the start of a day with little sunshine, in the evening the temperature of the two hundred liters of water will rise for example to 280. At this temperature the water cannot be used for the intended domestic or industrial use. I1 would be in this ca "much more interesting during this same day to obtain oient liters of water at 480 or einquante liters at 880 (the losses not being taken into account).

 In short, it would be interesting to use the energy received to heat water to a predetermined temperature even if it means obtaining a limited quantity. Hence the variable volume balloon process.

 This tank must have a movable part to increase or decrease the volume of water to be heated.

 Many methods can be used to meet this requirement. Two examples will be presented.

-A- THE VOLUME BALLOON} VARIABLE THANKS TO AN ELASTIC MEBrsBRllE (fig. 2)
The balloon is divided by a membrane (1) which can deform under pressure either upwards and therefore increase the volume or downwards and reduce the volume until complete expulsion of the water if necessary. For this improvement to be viable some small transformations are necessary compared to the classic balloon
a) fix the membrane in the balloon tightly
b) regulate the water inlet as a function of the internal temperature of the tank. To do this, an aquastat, a thermostat or a control panel (3) gives the signal to the electro valve (4) to open and let the water enter when the temperature of the water in the tank is higher than the chosen temperature. As soon as the temperature of the water contained in the tank returns by adding fresh water below the selected temperature, the solenoid valve closes and so on. If there is no more water in the tank, the heat of the water in the exchanger (7) will trigger the opening of the solenoid valve (4) as soon as the temperature of the primary circuit is adequate.

 It would be appropriate for the cold water in the tank to be fitted with a simple system which, thanks to the pressure, would make it possible to mix the water contained in the tank with a view to thermal homogenization providing greater accuracy of the regulation. This system could be a sprinkler head outlet, a fin outlet, involving a rotational movement in cold water.

c) the hot water outlet pressure can be caused by
- the waterfall If the balloon is located high
- The introduction above the membrane of a gas (5), for example nitrogen if the balloon cannot be located high or if the falling pressure is insufficient. The pressure of this gas will be adjusted according to the installation.

- d) hot water will come out from the bottom of the tank to allow all the water to be used. If it is deemed necessary to keep a permanent quantity of water in the balloon (for example to leave the aquastat in aqueous contact), it will be possible to introduce a grid at the bottom of the balloon preventing the membrane from deforming completely towards the bottom and increase the height of the hot water outlet tubing
e) the heat exchanger t73 will be concealed on the walls of the tank to allow the membrane (1) to deform downwards without encountering any obstacle.

-B- BALLOON WITH VARIABLE VOLUKE GXhCE HAS A PISTON OR FLOAT (fig. 3 &)
The balloon is made up of two parts: a body (2) and a movable float or piston element (1) which under pressure or depression will rise or fall in the body increasing or decreasing the volume of the balloon. For this ball to drink functional some improvements are necessary
a) the seal between the float and the body will have perfect title, the current technique gives us many processes such as joint, segment ...

 b) adjust the water inlet according to the internal temperature of the tank. To do this, an aquastat, a thermostat or a control panel (3) gives the signal to the solenoid valve (4) to open when the temperature of the water contained in the balcony is higher than the chosen temperature. As soon as the temperature becomes, by the supply of clean water, lower than the selected temperature the solenoid valve closes and so on.

 The cold water (10) under pressure entering the balloon will raise the piston (1) until the solenoid valve closes. When the piston is at the bottom of its stroke there remains an unusable water guard in this example (vacuum effect), it goes without saying that by giving a concave shape to the piston we can reduce this water guard in this in this case, it will be necessary to move the exchanger or opt for a tank without a primary circuit 11 water from the tank being directly heated in the collector.

 c) the hot water outlet pressure is carried out by the weight of the piston surmounted by a tare (8). This tare allows the pressure to be adjusted according to the installation. The weight of the piston and the tare should not be too great to avoid preventing the piston from rising under cold water pressure.

d) provide a system allowing the device to be charged with water when it is put into service, such as a charging tap (9) by bypass on the electro-valve (4) or an aquastat adjustable at low temperature,
e) note that a chemical or mechanical periodic descaling is necessary for a good seal between the piston and the body.

 With regard to these two examples of variable volume balloons, it is worth noting the characteristics and advantages of all the balloons of this type.

 These balloons allow the energy received to be used to heat a quantity of water that is certainly variable but usable grtGe at its high temperature rather than heating a large quantity of water unusable because of its low temperature.

 They allow the use of discontinuous energy sources such as solar, heat pumps, methane by anaerobic fermentation, etc.

for a longer period of the year than in classic balloons.

 In variable volume tanks it is the quantity of water to be heated which oscillates according to the energy received and not the temperature.

 They make it possible not to cool the hot water which is not used by an untimely arrival of cold water as in the conventional tank thus making possible the storage of this hot water.

 They make it possible to take larger capacity tanks that can exceed the average hot water requirements, no longer being limited by the risk of not being able to heat all the water to a suitable temperature.

 When the energy source is abundant, they allow operation identical to conventional balloons: solenoid valve permanently open, element movable in the high position.

 They allow, as in conventional balloons to connect all the equipment and devices already known such as pressure reducing safety group, gauge, installation in cascade or coupled with continuous energy etc ...

 They allow even with continuous energy such as electricity, gas, fuel oil to quickly heat a small amount of water (pending a larger one) to the chosen temperature and therefore to be able to quickly use l hot water without waiting for full heating of the entire capacity of the tank.

Claims (8)

 1) Hot water tank characterized in that it comprises a movable part (membrane or piston) making it possible to vary the volume of water to be heated.  2) Hot water tank according to claim 1 characterized in that nu'il comprises a solenoid valve, regulating the entry of cold water and by the same the variation in the volume of water to be heated, controlled by an aquastat in function of the temperature of the water in the balloon and consequently as a function of the energy received.  3) Hot water tank according to claims 1 and 2 characterized in that the pressure is applied by the movable part either by its own weight or by a gas which can,  4) Hot water tank according to all the preceding claims characterized in that it comprises a hot water outlet pipe in the low position.  5) Hot water tank according to all of the preceding claims characterized in that it may include a heat exchanger located outside the travel of the movable part of the tank.

 6) Hot water tank according to all of the claims / characterized in that it can include a pipe, allowing the initial charge of water in the tank during its commissioning, which can in particular be between a bypass with a tap shutdown on the solenoid valve.  7) Hot water tank according to claim 2 characterized in that S can include a water mixing device which can notably be located on the cold water inlet (canary apple, fin outlet).  11 - Hot water outlet  10 - Cold water supply  9 - Charging tap in bypass on the solenoid valve  8 - Tare  7 - Heat exchanger  6 - Energy source (solar collectors, boilers, heat pumps ...)  5 - Gases under pressure (for example nitrogen N 2)  4 - Eleotrovanne  3 - Aquastat  2 - Balloon body  1 - Movable part allowing the volume to be varied (membrane or piston) FIG. 4: Variable volume balloon thanks to a piston or float (low position) FIG. 3 s Variable volume tank thanks to a piston or float (high position) FIG. 2: Variable volume balloon thanks to an elastic membrane  technical) FIG. 1: Msllon of water heated by solar collector (current state of  L E G N D s