The present invention relates to an apparatus and a related process for improving the energy efficiency of a water system.

More particularly, the apparatus according to the invention is capable of exploiting the residual heat contained in the grey water produced by a water system in order to heat the flow of water entering the system.

In this way, it is possible to almost completely eliminate the demand for energy from appliances, such as heaters, boilers or burners in general, which usually act as heating elements for the flow of white water supplied by the water supply system.

The apparatus is particularly useful if installed in water systems with single utility, such as a normal domestic system, and/or multiple utilities, such as residential buildings, gym showers, swimming pools and similar activities. Grey water is classified as the waste product, destined to be conveyed into the sewerage system, of all water utilities with the exception of toilet drains. In the case of water users such as showers, sinks and the like, at least a portion of the incoming water is usually heated by a burner and then mixed with a fraction of cold water to provide the user with a mixture of water at a temperature deemed ideal; this mixture then flows into the sewer.

The waste water, however, at this point still retains much of its temperature and, therefore, its thermal energy, which, however, is totally dispersed. Currently, there are water systems that provide for the possibility of installing systems to collect wastewater, and especially grey water, with the aim of reusing it, after a purification process, for irrigation purposes and/or for uses where clean water is not required, for example to feed the drains of sanitary services.

However, there are no known plants or equipment capable of recovering the heat contained in wastewater.

Therefore, there is a need in the industry for a solution that allows, in particular, to reuse grey water to lower the energy requirements of the heating system integrated with the water system and/or for energy recovery in general.

The main purpose of the present invention is, therefore, to provide an apparatus for improving the energy efficiency of a water system; in particular, the apparatus is capable of recovering the thermal energy of the hot water produced during the use of the utilities, in order to heat the incoming cold water.

In this way, it is possible to minimize the use, and therefore also the energy consumption, of the heating systems that are commonly used for this purpose.

A further scope of the invention is to produce an apparatus for the improvement of the energy efficiency of a water system that allows the recovery of the heat contained in the wastewater while keeping its flow separate and isolated from that of the incoming water, in order to avoid problems arising from contamination.

Another objective of the present invention is to provide a solution for energy improvement of water systems that is compact and easy to install.

Another purpose of the invention is to construct an apparatus of the said type that is cost-effective and easily implemented, due to the advantages achieved.

Finally, an objective of the invention is to provide an apparatus for the energy improvement of water systems that is usable in both domestic settings as well as in larger settings, such as residential buildings, swimming pools, gyms, etc. These and other purposes are achieved by an apparatus for energy improvement of water systems according to the appended claim 1 , and by a process for energy improvement of water systems according to the appended claim 10.

Additional detailed technical features of the invention are provided in the appended dependent claims. The present invention will now be described, by way of example but not as a limitation, according to some of its preferred embodiments, and with the use of appended figures, wherein:

- Figure 1 is a schematic representation of an apparatus according to the invention, which is in this case integrated into a water system having a single user;

- Figure 1 A is a detail of a component of the apparatus according to the present invention;

- Figure 2 is a schematic representation of an apparatus according to the invention integrated in a water system provided with multiple utilities.

With particular reference to Figure 1 , a schematic example of a water system is shown, to which an energy recovery apparatus according to the invention is integrated.

The apparatus shown includes a number of components, listed below;

- an inlet water treatment unit a;

- a first heat exchanger b, or main heat exchanger;

- a second heat exchanger c, or condenser;

- a third heat exchanger or evaporator d;

- a compressor e.

The exchangers are preferably of the coaxial counterflow tube type.

In addition, the system may include auxiliary components, for example;

- a heater or boiler f;

- a mixer g, electronically controlled and motorized;

- a heating element h;

- a collection tank i;

- a recirculation pump I for thermal disinfection;

- temperature sensors ST 1 , ST2, ST3, STx, STA1 , STA2, STA3, STB;

- at least one flowmeter FS1 , FS2;

- a set of EV1 , EV1 bis, EV2 solenoid valves;

- auxiliary pumps to move the fluid 12, and check valves 20, 21 ; - a central electronic control system used to receive the parameters detected by one or more sensors located in the apparatus and/or plant, to process the operating parameters of the apparatus and to adjust them.

In order to illustrate more clearly the structure and characteristics of the apparatus, an example of the operating cycle of the apparatus itself and of the heating system connected to it will be described; the description is substantially valid both in the case of apparatus for a single utility and for multiple utilities.

The apparatus can operate in two different modes; the first mode of operation is performed when the system is started up, for example when a user turns on the hot water tap of a shower.

At this point a transient state is established, in which, since no waste water is yet available from which to draw heat, initial heat must be supplied from boiler f. In particular, during the transient state, the water coming from the water mains (the inlet is indicated in figure 1 with the reference I) can cross, optionally, a treatment unit a, having functions of filtration, pressure regulation, addition of additives, such as polyphosphates or softeners for descaling, and/or other preliminary operations normally carried out. Subsequently, the water, having for example temperature T 1 equal to about 9-10 °C (temperature measured by temperature sensor ST1), may cross a flowmeter FS1 before entering the main exchanger b; in this preliminary step, such exchanger b cannot work yet, since the heat contribution of the hot stream is missing and for the moment it is simply crossed by the cold water stream.

Another temperature sensor STx is placed between the first exchanger b and the second exchanger or condenser c, to detect the water temperature between the two once the apparatus is in the second mode of operation, at steady state. At this point, the water flow is distributed between branches 1 and 2 of the respective pipes of the apparatus: branch 1 introduces cold water into boiler f so that it is brought to a higher TB temperature (the temperature is measured by an STB sensor positioned at the outlet of boiler f itself).

If necessary, in this branch 1 it can be installed a solenoid valve EV2 and a flowmeter FS2 or similar devices, capable of managing and measuring the passage of fluid in the branch 1 itself; under operating conditions, both in transient and steady state, the solenoid valve EV2 remains open, closing only when the apparatus is not used for maintenance purposes, as explained later.

Branch 2, on the other hand, conveys the flow of cold water exiting the condenser c first to a temperature sensor ST2, then to the mixer g.

For this purpose, a solenoid valve EV1 is installed upstream of the proper utility u, such as the shower head; during the transient state, valve EV1 remains closed in order to direct the flow of cold water from branch 2 to mixer g. A second solenoid valve EVIbis, positioned between mixer g and utility u, remains open during transient state.

Additional accessory devices that can be installed just upstream of utility u are:

- the heating resistor h, for the fine regulation of the temperature (this resistor h advantageously features an electronic control of the power delivered to compensate for any small fluctuations in the temperature T3 of use);

- a temperature sensor ST3 placed after the heating element h;

- a UV lamp 13 for sterilizing the water flow.

The water is then used and ends up in the user drain u, retaining much of its temperature and heat.

Instead of ending up directly in the sewer FGN, such hot wastewater is conveyed to a collection tank i; after being possibly treated and/or additivated (for example by means of filters 11 and/or devices for the administration 10 of detergents and/or descaling agents), the water is brought to the main exchanger b by means of a pump 12.

In detail, the filters 11 may be of the self-cleaning type depicted in Figure 1 A. This type of filter prevents wastewater coming from the utilities to convey solid and/or oily residues inside the exchangers b, d, thus avoiding their occlusion.

The filters generally comprise an enclosure 100 in which there is an inlet 150 from the collection tank i, or from the utilities u depending on whether or not the tank i is present, and two outlets.

A first outlet 160 is used to discharge the residue retained by the filter 11 to the sewer FGN, while a second outlet 170 conveys filtered hot wastewater free of the residue to the exchanger b.

The space within the enclosure 100 is divided into a first chamber 101 and a second chamber 102, separated by a separation wall 106, and extending in a direction from the inlet to the outlets previously described.

In particular, the first chamber 101 communicates only with the outlet 160 directed to the sewer FGN, while the second chamber 102 receives wastewater from the inlet 150 from the utilities u, and conveys it to the second outlet 170 to the exchanger b.

Along the partition wall 106, and in any case in a central position with respect to the chambers 101 and 102, a shaft 104 is positioned, which can be put into rotation by a motor 103 around an axis X.

Filtering surfaces 110, 120, 130 are attached to the shaft 104, at approximately regular distances from each other, and extend substantially across the entire width of the space inside the enclosure 100, so as to divide the chambers 101 and 102 into respective compartments.

Preferably, such surfaces are stainless steel discs, and have holes on their surface.

The filtering capacity of the surfaces 110, 120, 130 progressively increases in the direction towards the outlets (therefore the size of the holes of the respective discs decreases), so as to separate as much residue as possible from the wastewater passing through them.

This separation occurs, as mentioned, in the second chamber 102 as the wastewater consecutively passes through the surfaces and the residue is retained. The filtered water is conveyed to the second outlet 170, while the residue is retained and accumulates on the surfaces 110, 120, 130.

Periodically, the shaft 104 is rotated by the motor 103 in the direction of the arrow F and at a predetermined angle, bringing the "dirty" portion of the filtering surfaces 110, 120, 130 that has retained residue from the grey water, from the second chamber 102 to the first chamber 101.

Here, washout nozzles 105 emit high-pressure water that cleans the filtering surfaces, removing the residues and conveying them towards the outlet 160 and to the sewers. Oily or greasy buildup is removed by a flushing process with suitable degreasing-detergent liquids.

The process is repeated periodically depending on the amount of use of the plant or the amount of residue that builds up.

The installation of self-cleaning filters of the type described above solves the problem of frequent replacement, which is required in the case of conventional filters or disposable filters.

The temperature of the outgoing wastewater is measured immediately prior to entering exchanger b by a STA1 temperature sensor.

Upon entering exchanger b, the wastewater acts as a hot stream and begins to give up heat to the cold stream coming from the main water supply.

The temperature of the hot stream leaving the exchanger b is then measured by the sensor STA2, and the same hot stream is brought into the evaporator d.

This evaporator d is part of a heat pump cycle that also includes the condenser c and the compressor e; additional auxiliary devices may also be contemplated, such as a wattmeter w for measuring the power absorbed by the compressor e.

This heat pump acts, in a conventional manner, by using the remaining heat contained in the cold stream leaving the exchanger b to evaporate a gas at low pressure.

The gas is then compressed by the compressor e, which raises its temperature, and sent in a closed cycle to the condenser c, where it gives up its heat to the water stream of branch 2; this stream has already been partially heated in the main exchanger b.

The boiler f continues to supply heated water to the system, since the amount of heat given up by the wastewater is not yet sufficient to ensure an ideal temperature to the utility u; this temperature is preferably measured by the sensor ST2.

However, as more and more hot water reaches the collection tank i, and then ends up in the exchangers, the final temperature of the water increases until it reaches an optimum value, preferably around 40 °C. At this point, the apparatus enters the steady-state mode; in this condition, the boiler f shuts down, as it is no longer needed, and the cold water coming from the aqueduct is heated exclusively by the heat contained in the wastewater and by the heat pump.

The central electronic control system, acquiring the temperatures measured at the different points of the system, modulates the compressor power, so as to obtain a suitable temperature difference for the water leaving the condenser c.

In particular, the mixer g is electronically controlled by the central electronic control system, which, based on the temperature T3 of operation, which is set by the user on an interface display (and normally varies from 34 °C to 42 °C), and based on the temperature detected by the sensors ST2, STB and on the flows detected by the flowmeters FS1 , FS2, allows to proportionally mix the inlet flows to obtain the outlet flow towards the solenoid valve EV1 bis at the desired temperature. As an example, here are some approximate values of expected temperature, measured in steady state conditions at several points of the plant:

- T2 and T3 = 35-40 °C

- T1 = 10 °C;

- Tx = 35 °C;

- TA1 = 37-38 °C;

- TA2 = 12-13 °C; - TA3 = 9-10 °C.

By doing so, the apparatus is capable of supplying domestic hot water with a remarkably low consumption, due to the compressor being in operation. For example, with the temperature values T1 , T3 mentioned above and a flow of about 10 liters per minute, compared to a heat output from the shower of 21 KW, only 0.8 KW of primary electrical energy absorbed by the compressor is needed (about 4%) with a consequent energy saving of 96%. Optionally, depending on design and/or installation requirements, the following can be provided:

- an auxiliary inlet IA to the water mains, additional to the first inlet, for the boiler f;

- check valves 20, 21 ;

- a recirculation pump I.

This thermal disinfection procedure is periodically activated in an automatic way by the control system; it acts by taking water from the boiler f at a temperature of about 70 °C and pumping it into the pipes of the system to sterilize them.

Conveniently, the solenoid valve EV2 remains closed during this procedure, to avoid the creation of a closed circuit between the recirculation pump I and the main exchanger b.

With particular reference to Figure 2, a second realization variant of the apparatus according to the invention is schematically represented, in this case for connections to multiple utilities.

The components used are substantially similar in terms of characteristics, arrangement and operation.

In the system shown, each utility u has a motorized mixer g with dedicated electronic control; an additional cold water inlet from the water supply system is positioned upstream of the mixers g themselves.

In addition, there is a storage tank m for the heated water, located immediately after the last exchanger c crossed by the flow of water; since it is an apparatus intended to serve more than one utility, it is convenient to have a reserve of hot water to compensate for any increase in demand from utilities u.

For the same reason, a further pump 15 is positioned before the utilities u, so as to ensure the necessary head for the fluid to be transported. Specifically, the selection of a temperature value T3 (normally varying from 34 °C to 42 °C), which can be carried out by a user on a display located at the utilities u, is transmitted to the central electronic control unit, which, with the data measured by the temperature sensors ST 1 , STX, ST2, ST3, STA1 , STA2, ST A3, STB and by the flow meters FS1 , FS2 calculates the flow regulation of the mixer g and the power of the compressor and any fine regulation power of the heater h.

From this, the central electronic control unit determines whether or not to use the hot water stored in the boiler f and at what flow rate the pump 12 should operate.

In addition, the electronic control unit is able to determine when and how to operate disinfection and/or filtering of the clear and/or grey water hydraulic circuits.

Even in this form of embodiment, periodic execution of the thermal disinfection procedure may be provided.

Similarly to the first embodiment, it is contemplated that at least one heater or boiler f heats water to a temperature suitable for the elimination of pathogens, which is then circulated in the pipes of the system to sterilize them by means of at least one pump I.

Conveniently, the water system can be divided into sections by interposing valves in the connecting pipes, each provided with a boiler f and a pump I connected downstream of the boiler f itself.

In Figure 2, the system is divided into sections that can be sterilized individually or simultaneously.

A first section is defined by the piping and components between connections 80, 40, and 30; a second section is defined by the piping and components between connections 30, 40, 50, and 60; a third section is defined by the piping and components between connections 50, 60, and 70. To each section a boiler f, a pump I and a solenoid valve are connected, respectively indicated by reference EV01 , EV02 and EV03.

By closing one or more of these solenoid valves, it is possible to create a partial closed circuit in the water system and isolate the section to which the solenoid valves are connected.

Vice versa, opening them allows hot water to circulate in the pipes and in the components connected to them so that they can be sterilized.

For example, by leaving only solenoid valve EV01 open and by closing solenoid valves EV02 and EV03, boiler f 1 and pump 11 between connections 80, 40 and 30 can only disinfect exchangers b and c.

Alternatively, by leaving only EV02 or EV03 valve open, the second section (between connections 30, 40, 50, 60) or the third section (between connections 50, 60 70), then the storage tank m or mixers g and utilities u, can be sterilized by boilers f2 or f3 and pumps 12 or 13. In addition, two or more solenoid valves can be opened at the same time, to sterilize several sections by means of a single boiler.

The system configuration shown in figure 2 can also be implemented in the form of the embodiment shown in figure 1 , by interposing valves and, if necessary, additional boilers and/or pumps for recirculation. Advantageously, the apparatus which forms the object of the present invention can be implemented in the form of a single-piece unit, easily installable and applicable on already operating water systems, in both public and private contexts.

Moreover, the embodiments described herein represent two of the many possible variants of the apparatus object of the invention, and many modifications to the characteristics and arrangement of the components may be made by the skilled person, without departing from the scope of the appended claims.