ES2365281A1 - System of hot water sanitary for solar energy with recovery of residual energy. (Machine-translation by Google Translate, not legally binding) - Google Patents

Abstract

System of sanitary hot water by solar energy that includes, at least: A plurality of deposits (1,2,3) placed in series, generally two or three; in such a way that the hot water (11) that leaves the plurality of solar collectors (4) goes through the first tank (1), and from there to the second (2) and the third (3), to the last tank (3) ) is maintained at a lower temperature than the first (1) and second (2) tanks, said last tank (3), furthermore, includes a heat exchanger (71) through which the gray water (10) passes, yielding its heat . (Machine-translation by Google Translate, not legally binding)

Description

Domestic hot water system for energy solar with recovery of residual energy.

Object of the invention

The object of the present invention is to a solar hot water system with solar energy waste energy recovery and application with high efficiency of complementary energy.

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Field of the Invention

The field in which the invention is framed is in that of the domestic hot water systems that they use renewable energies for its operation.

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Background of the invention

Obtaining hot water at temperatures below 70ºC, from the direct application of energy solar, has long been one of the practices of use of the sun's most widely used radiation, due to the competitiveness of said system in relation to the conventional sources; this is thanks to the high performance that for these temperatures they have the sensors, as well as the reduced investment involved in this use.

Hot water applications at low temperature are very varied, and range from heating to pools, where it is necessary to keep the water in the glass at about 25ºC, until use as domestic hot water in homes, hospitals, etc., where temperatures of up to 50ºC are required, going through industrial applications and those corresponding to low temperature heating.

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(A) Components of a solar system for (to obtain domestic hot water

Focusing on the issue of obtaining water sanitary hot, where the advantages described above are joins that of its use throughout the year, the components that are likely to become part of a system of solar energy utilization, both for hot water sanitary as for heating, are included in the subsystems of collection, distribution, exchange, of accumulation, support and regulation energy.

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(i) Capture subsystem

It is formed by the field of solar collectors that collect solar radiation and transmit heat energy to fluid flowing through them.

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(ii) Distribution Subsystem

Set of pipes through which the Different types of fluids. The circulation can be by thermosiphon, but it is more efficient to use pumps that can regulate much better system operation.

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(iii) Exchange Subsystem

When in the solar harvesting system the consumption fluid does not circulate through the collectors, it must there is an exchanger, where the heat transfer takes place from heat transfer fluid to consumption fluid.

In small installations the heat exchanger is included in the accumulator tank, yielding heat directly to the consumption fluid contained in the accumulator. This type of exchangers generally adopts two configurations: coil, with possibility of galvanic corrosion by use of different metals, and the envelope chamber, which solves this problem, even when it has a lower performance.

For more important installations they are used the exchangers outside the accumulator tank, being the most used the tubular and the plates.

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(iv) Accumulation subsystem

It is formed by the deposit (s) accumulators, which stores hot water, usually by stratification, and allows the use of hot water even when there is no solar radiation, so that it achieves the adequacy of the intermittent and variable characteristics of the solar radiation, to those of consumption. Stratification before mentioned is achieved through the appropriate connections between collectors and accumulator; these connections must be established meeting the following conditions:

The entrance to the collector, which must be done by the lower part must be connected to the lower part of the accumulator, where the coldest water is located.

The exit of the collector, which must be done by the upper part must be connected to the upper part of the accumulator, where the hottest water is located.

Cold water inlet from the network to the accumulator It must be done from the bottom.

The hot water outlet of the accumulator for The consumption must be made from the top.

If several deposits are placed, as in the proposal of this patent, would not work by stratification if not that each tank would accumulate at a different temperature, with a greater efficiency

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(v) Subsystem of auxiliary or support energy

Since generally the system of solar utilization will not cover 100% of the needs of domestic hot water, not to be interesting from the point economic view and the permanent overheating of the installation, when the temperature that is required in the water of consumption is not achieved with this system it will be necessary to install a auxiliary system that, by using another source energy, usually conventional, allow to obtain the required consumption temperature.

There are different methods of incorporating auxiliary energy to preheated water through a system solar; the most commonly used consist of water heating contained in the accumulation tank of the solar system, in the water heating of a support accumulation tank or in heating to the passage at the outlet of the accumulator.

These types of support can be done with any type of energy, whether obtained from fuels solids, liquids or gaseous, of electricity or of another system alternative. Support systems that require an installation expensive will only be profitable in the case of large consumption energetic; by cons in facilities of reduced size, calculated to obtain maximum profitability, which in our latitudes reach a percentage of solar energy contribution between 55 and 85% of the total needs, this auxiliary contribution is obtained from gas, mainly in heating applications to the step, for being instantaneous and abundant, and, more and more, from electrical energy with use nocturnal, by introducing an immersion resistor in the upper part of the accumulator, if it is the first method before described, or in the lower part of the support accumulator if it is the second. Generally the electrical support allows access to systems with lower initial cost, but similarly offers in the most of the cases the highest energy costs.

In the present patent the Need for this support system or reduced to the maximum.

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(vi) Regulation and control subsystem

It is formed by the set of elements (thermostats, pressure gauges, probes, etc.) which, according to the temperatures of the subsystems of collection, exchange and accumulation, allow the start-up or stop of the system.

Generally the control of a solar system is performed by comparison, with a differential thermostat, between the temperatures in the collectors and in the tank accumulator, measures with any type of immersion probe or contact If the temperature of the collectors is higher in certain degrees to the accumulator, the thermostat puts on the circulation pump runs so that the fluid travels through the sensors, while if that temperature is found by below a few degrees, also previously adjusted, the bomb.

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(B) Systems based on heat transfer fluid

The basic classification of water systems sanitary hot is established from the fluid that circulates to through the sensors and the way this is done circulation between the collection and accumulation subsystems.

According to the heat transfer fluid, which circulates by the collectors, be the same drinking water or establish a exchange between the heat obtained by the heat transfer fluid and the of consumption, originate two types of systems: the direct, where the drinking water acts as a heat transfer fluid, and the indirect one, where the heat transfer fluid gives heat in the exchanger to that of consumption.

The direct system, also called of open circuit, presents problems derived from the possibilities of freezing of water, both in the collectors, and in the network of primary distribution, corrosion production and inlay formation.

The risk of freezing can be avoided by the application of various methods, which go from the emptying of the installation in case the outside temperature drops by certain level, until the placement of electrical resistors in the water heating circuit, going through the method most common consisting of circulating hot water from the accumulator through the collectors, which causes large energy losses, but that solves the problem of increasing volume of the fluid when freezing occurs.

Regarding the risks of corrosion and inlays, both can be avoided by treating fluid and with the careful choice of the materials of the installation.

In the indirect or closed circuit system, establishes a heat exchange between the heat transfer fluid and the consumption, and therefore consists of a primary circuit between collectors and exchanger, which gives heat to a secondary circuit where the drinking water circulates. This improvement eliminates the drawbacks of the direct system at the cost of raising the price of the installation and decrease system performance due to heat exchange On the other hand, it eliminates the risk of freezing when possible to use antifreeze in the circuit primary.

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(C) The systems depending on the type of circulation of the fluid: natural circulation

According to the circulation being established so natural or forced distinguish two types of systems, called also of natural and forced circulation.

In the gravity circulation system, also called convection, passive or thermosiphon, the water that has been heated in the collector rises by decreasing its density and being lighter than cold water, at equal volume. This system is the simplest, since its operation is automatic and does not require a circulation pump or any type of control; nevertheless, to be able to use it, it is necessary, on the one hand, that the accumulator tank is located higher than that of the solar collectors, and on the other, that the heating of the water is sufficient to overcome the resistances that oppose the circulation of the water, or losses of load due both to the friction of the water on the internal wall of the pipe and to the accidents of its route (elbows, curves, valves,
etc.).

The pressure will be higher and therefore faster the circulation of water, the greater its heating, or what it is the same, solar irradiance, and the higher the height, with the except that this increase in height causes greater losses of load and increases in the cost of the system.

Thermosiphon systems are usually marketed as compact equipment consisting of one or two flat collectors, on which an accumulator tank is located isolated, connected to them, and mounted both on a structure which stiffens the assembly and allows its placement on surfaces horizontal. The use of the system directly or indirectly it will depend on the type of installation that is carried out, in function of the forecasts of use of said system.

The main limitations derived from the use of the domestic hot water system by thermosiphon se They can summarize in the following four points:

(i) The distribution network must be carried out with the lowest possible head losses, since otherwise They would be defeated by convection.

(ii) The accumulator tank must be located by on top of the collectors and next to them, which can cause problems, both for the aesthetics that the system offers in its integration with the building, as per the technical difficulties derived from said situation, and by the heat losses of said accumulator.

(iii) The connection of series sensors does not It can be applied to a thermosiphon system, due to the large resistance to the circulation of water that occurs when crossing all the fluid all the sensors.

(iv) Temperature control in the Storage of such systems is difficult and expensive, so which generally is not placed, and its absence allows to reach fluid temperatures above 60 ° C, which favors inlays that hinder its circulation.

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The main current limitations of the technique refer to the solar systems for preparation of domestic hot water, whether flat solar collectors, vacuum collectors or any other type of collector, is dimensioned under amortization and performance premises economic. Another determining factor for its dimensioning is the avoid having the oversized installation part of the year, which It would involve excess heat that could damage the system.

In these cases, to prevent the problem, empty the installation, totally or partially, it is divided or dissipates heat outward, air, earth, a pool, a well, etc. All this represents a great discomfort so facilities tend to be sized so that they only cover a fraction of the total needs. This fraction may vary. between 30 and 70%.

The remaining percentage must be provided by a conventional heating system, electricity or a boiler combustion, or it must be accepted that the temperature to be obtained from system in many moments will not be the desired one to use, which should be around 40 ° C.

On the other hand, the collector systems solar need an accumulation tank to accumulate all the energy captured in the moments of solar irradiation and power dispose of it in the rest of the day. This deposit must be related to the catchment surface. The optimum is estimated between 50 and 100 liters per square meter of collection.

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Description of the invention

The system object of the invention consists of a sanitary hot water preparation system using energy solar that also uses the residual energy of gray water hot of the building once these have been used, with the intention that the installation covers 100% of the needs without be oversized in no time. If the installation has of a catchment area that is too low, the 100% but conventional energy will be significantly reduced specified. The system object of the invention comprises, at less:

A plurality of accumulation deposits placed in being him, where the last one receives the energy residual gray water, which are those from washing machines, dishwashers, sinks, sinks and showers, used before expel them out of the building;

And where the first deposits will receive the heat input from solar collectors by an exchanger located in each of them, connected in series or in parallel to a plurality of thermostatic valves, so, that, initially, all the hot water that comes out of the collectors pass or heat the first deposit, and then through the second.

The last of the deposits, the one that keeps lower temperature, has another exchanger through which water passes Hot gray, giving up its heat.

The first deposit must have the capacity corresponding to the peak moments; usually in the morning, when the showers are concentrated. Being a deposit with a capacity smaller than that corresponding to the optimum for the installed collector surface, can be easily reached The temperature of consumption at all times. If not reached, by correspond to a day with little solar radiation, the contribution of conventional energy would be just the right one to meet the demand immediate. The rest of the energy, if it exists, will pass to the second tank, since the exchanger located in the first tank, at have the same water temperature, stop giving it up and send the energy remaining to the second. This deposit will only be tempered, if the Surplus is small, or it will heat up completely if there is no consumption or the irradiance is high. In this second deposit will occur the contribution of wastewater energy that, as it will take a temperature clearly higher than that of the tank It will give up heat easily. This may also occur in a possible third deposit that will also serve to temper the water.

If the energy transferred by the recuperator is elevated, the water will reach the previous tank at the temperature of consumption or close to it, so the solar system will not require give up almost heat by passing all the energy to the rest of the deposits.

The system ensures a temperature of consumption at peak times equal to that desired without the need for provide conventional reheating energy, in most the cases, all because the deposit is smaller than the theoretically optimal relationship.

Instead of having a single deposit at a average temperature lower than desired, you have a first deposit at the desired temperature and a second or third deposit at a lower temperature than would be obtained in the case of a deposit only.

This fact, instead of being a defect is a achievement, because when establishing a greater thermal jump between the gray water temperature from which you want to recover the heat and the deposit, the transfer of energy is greater.

If the temperature of the first tank exceeds that of consumption, you must proceed to create a bypass to the second and distribute its energy among the rest of the tanks. There are two options: a three-way valve that directly drifts the water to the second tank, or a double connection to the second tank, inlet-outlet, which is the simplest and recommended system; In this option, when the operating temperature is exceeded, the water will be mixed with that of the second tank until the appropriate temperature is reached.

If necessary, have energy conventional support, very unfavorable weather conditions or innate with poor catchment surface, the contribution of Energy must be produced in the first deposit. That way you only know provides what is needed and avoids having hot water without use for too long, which always represents losses of hot.

The main advantages of the system object of The invention are as follows:

The system will never be overheated because at sizing below consumption needs will never be given that situation. This will avoid having to incorporate a system additional heat dissipation and allow amortization of the investment in a shorter period of time.

If all deposits are heated to the proper temperature, residual energy will not be used eliminating with gray water naturally.

If the proper temperature is not reached in some deposit will be completed with the energy obtained from the waters gray

If it is still not enough (conditions adverse weather conditions) the support system will only heat the specific amount of consumption avoiding waste of Energy.

Its application is for all those buildings where there will be consumption of domestic hot water or water hot for bithermal appliances, washing machines and dishwasher, With this system the consumption temperature is reached without incorporating any conventional support system, with the consequent energy saving. The installation is done with a tight and amortizable investment, and avoiding that it is necessary dissipate excess heat at any time of the year.

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Brief description of the figures

Then it goes on to describe very brief a series of drawings that help to better understand the invention and that expressly relate to an embodiment of said invention presented as a non-limiting example of is.

Figure 1.- Schematic view of the system object of the invention, with the tanks placed in series and support of energy in the form of electrical energy to the first deposit of the installation.

Figure 2.- Schematic view of the system object of the invention in a low climatic situation solar radiation, in the case where there is not enough temperature in The first deposit.

Figure 3.- Schematic view of the system object of the invention in a low climatic situation solar radiation where the energy contribution of Support exclusively to the first deposit.

Figure 4.- Schematic view of the system object of the invention in a low climatic situation solar radiation where it is shown as after consumption, the second tank has received preheated water in the third tank.

Figure 5.- Schematic view of the system object of the invention, in a climatological situation with radiation sufficient solar, where it is shown that the adequate temperature in the first tank.

Figure 6.- Schematic view of the system object of the invention, in a climatological situation with radiation sufficient solar, where the situation is shown where it is not the auxiliary support energy needed.

Figure 7.- Schematic view of the system object of the invention in a climatological situation with radiation solar higher than necessary, where the situation is shown where the proper temperature has been reached in the first Deposit.

Figure 8.- Schematic view of the system object of the invention in a climatological situation with radiation solar higher than necessary, where the situation is shown where auxiliary support energy is not necessary.

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Preferred Embodiment of the Invention

As can be seen in Figure 1, the solar hot water system with solar recovery of residual energy from the hot gray waters of the building once these have been used includes at least:

a plurality of accumulation deposits (1, 2, 3) placed in series, usually two or three (as represented in figure 1), configured so that:

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he last of the deposits (3) receives the residual energy of the waters gray (10);

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he first deposit (1) and the second deposit (2) receive the contribution of heat from a plurality of solar collectors (4), to through a plurality of heat exchangers (5, 6, 7) located in each of said deposits (1, 2, 3); and where said exchangers (5, 6, 7) are connected, either in being, or in parallel, to a plurality of thermostatic valves (8);

such that all the hot water (11) that leaves the plurality of solar collectors (4) passes through the first deposit (1), and from there to the second (2) and the third (3);

and because the last of the deposits (the third deposit (3) in this embodiment) is maintained at a lower temperature than in the first (1) and second (2) deposits, said last tank (3) further comprising an exchanger of heat (71) through which gray waters pass (10) yielding their hot.

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The first deposit (1) has the capacity corresponding to peak moments and less than optimal for collector surface (4) installed, so that it is reached with ease the temperature of consumption, and where not to reach said temperature, the contribution of conventional energy (20) It would only be accurate to reach immediate demand.

The excess energy passes to the second deposit (2) and from there to the third (3) (in the case of two deposits it will pass directly to the last one) because the first exchanger (5) located in the first tank (1), having the same temperature as  the water will cease and send the excess energy to the following deposits (2, 3).

In the last deposit (3), in this embodiment the third, the contribution of water energy is produced grays (10), which will give heat to the tank through the third heat exchanger (71), for being the water temperature gray higher than the third tank (3), and where if the energy assigned by the third exchanger (71) of the third tank (3) is elevated, the water will reach the previous tank (the second tank (2)) at or near the temperature of consumption, so that collectors (4) will not need to give heat to this last tank (3).

Thus, the system thus described allows ensure a consumption temperature at peak times equal to the desired without providing conventional reheating energy, since the first deposit (1) is smaller than the theoretically ratio optimal Therefore, instead of having a single deposit to a average temperature lower than desired, you have a first deposit (i) at the desired temperature and one last tank (3) at a lower temperature so that when a jump is established higher temperature between the temperature of the gray water and the Last deposit, the transfer of energy is greater.

If the temperature of the first tank (1) exceeds that of consumption, a bypass is created to the second, and distributes its energy among the rest of the tanks (2, 3), where said by-pass is constituted in a way selected from:

(a) a three way valve;

(b) a double connection entrance exit.

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The contribution of conventional energy (20) is produced in the first deposit (1).

In the present practical embodiment of the invention, the characteristics of the components are the following:

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Two o three heat-insulated tanks (1, 2, 3). They can be metallic, from reinforced polyester or any other heat resistant material Able to store water.

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He first tank (1) comprises a first exchanger (5) at primary system, connection to the second tank (2), simple (of inlet) or double (inlet and outlet) and water outlet at consumption.

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A last tank (3) with a double exchanger (7, 71), with the primary in second instance and with the heat recuperator, connection with the second tank (2), single (outgoing) or double (of inlet and outlet) and network water inlet (30) and water outlet cold gray (40).

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Yes there is an intermediate deposit, this second deposit (2) will carry a exchanger (6) with the primary in second instance, connection with the first deposit (1), single (outbound) or double (inbound and output) and input connection with the last tank (3).

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Support energy input in the first tank (1), already by means of an electrical resistance (21), if the installation is small, or with a heat exchanger at a conventional installation (combustion boiler or heat pump), If the installation is large.

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The dimensions of the components of the system, in this practical embodiment are the following:

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First Deposit: Equivalent to the peak consumption of the building where it is located and maximum 20 liters per square meter of surfaces installed collectors.

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Second deposit: If there is a third The second deposit will be identical to the previous one. If it does not exist, it will have between 30 and 60 liters per square meter of collector surfaces installed.

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Third Deposit: Your capacity must be such that you complete, taking into account installed in the two previous deposits, a minimum of 50 liters per square meter of installed collector surfaces and a maximum of 100 liters per square meter of surfaces of installed collectors, the quantity of 75 liters being recommended per square meter of surface of installed collectors.

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Finally regarding the behavior of system object of the invention in this practical embodiment, the solar hot water preparation facilities don't dimensioned to produce 100% of the needs of the building for two reasons: because the installation would be oversized for almost the entire year and that represents an excessive investment, and, secondly, because that excess energy must be dissipated to prevent the installation from damage, and requires a specific device or will require a maintenance and continuous control, such as partial emptying of the installation.

For these reasons the traditional installation covers a percentage of the demand, between 40 and 75%, usually, and conventional support energy must be provided It ensures the temperature of consumption.

On the other hand, almost all of the energy used in the preparation is pulled with the evacuation of the water once used, that is, gray water.

The designed device does not require energy from support, ensures the temperature of consumption, uses energy residual gray water, and avoid devices or actions of system overheating control.

In Figures 2, 3 and 4 the system is represented object of the invention in the event of low weather solar radiation, where in Fig. 2 it is shown as there is no sufficient temperature in the tank 1. Do not therefore receive anything at tank 2. Tank 3 is preheated with energy residual.

In Fig. 3 it is shown how the supply of support energy exclusively to tank 1, for ensure the desired consumption temperature without spending more energy That the essential for the consumption of the moment.

In Fig. 4 it is shown how after consumption the tank 2 has received the preheated water that was in the tank 3. Tank 1 is ready to heat with solar energy. Tank 3 is ready to collect energy of the gray waters that have just been consumed.

Figures 6 and 6 show the operation of the system object of the invention in a weather situation with enough solar radiation. So, for example, we have to in the In the case of Fig. 5, it can be seen how the adequate temperature in tank 1. Tank 2 comes some excess energy Tank 3 is preheated with energy residual. In Fig. 6 it is shown how energy is not necessary support assistant After consumption, deposit 1 has received the preheated water that was in tank 2, and tank 2 the preheated that was in tank 3. Tank 1 is prepared to complete the heating with a small amount of solar energy. Deposit 3 is ready to pick up the gray water energy that has just been consumed.

Finally, in figures 7 and 8 you can observe the operation of the system object of the invention before a weather situation with solar radiation higher than the necessary. Thus, in Fig. 7 it is observed how the proper temperature in tank 1. At tank 2 you may enough solar energy arrives to also reach the adequate temperature Tank 3 is preheated with energy residual and perhaps with excess solar energy. On the other hand, in the Fig. 8 no auxiliary support energy is necessary. After consumption the tank 1 has received hot water at the right temperature that was in tank 2, and tank 2 the preheated one that it was in deposit 3. Deposit 1 is ready for consumption and tank 2 to complete the heating with energy solar. Tank 3 is ready to collect energy from the gray waters that have just been consumed, and perhaps solar energy surplus.

Claims (4)

1. Solar hot water system with recovery of residual energy from the hot gray waters of the building once they have been used, characterized in that it comprises at least: a plurality of deposits (1, 2, 3) of accumulation placed in series, configured so that:

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he last of the deposits (3) receive the residual energy of the waters gray (10);

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he first deposit (1) receive the heat input from a plurality of solar collectors (4), through a first heat exchanger (5) located in said tank (1); and where said first exchanger (5) is connected, either in series, or in parallel, to a plurality of thermostatic valves (8);

and because all the hot water that comes out of the plurality of solar collectors (4) passes through the first tank (1), and from there to the last deposit (3), either directly or through a second intermediate tank (2); and because the last deposit (3) it contains cold water from the network (30) is kept at a lower temperature than the first (1) and second (2) deposits, further comprising a heat exchanger (7) through which gray water passes (10) giving up its heat.

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2. System according to claim 1 characterized in that the first tank (1) has the capacity corresponding to peak moments and less than the optimum for the installed collector surface (4), such that the consumption temperature is reached, and where said temperature is not reached, the contribution of conventional energy would only be the one required to reach immediate demand. 3. System according to previous claims characterized in that if the temperature of the first tank (1) exceeds that of consumption, a bypass is created towards the rest of the tanks (2, 3) and where said bypass is constituted in a way selected from: (a) a three way valve; (b) a double input - output connection.

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4. System according to previous claims characterized in that the conventional energy supply (20) is produced in the first tank (1).