Energy system for buildings.

The present patent application for industrial invention relates to an energy system for buildings.

The instantaneous hourly consumption of thermal energy in a house depends on the external conditions, on the time of the year and on the presence or absence of final users. Amongst the unknown factors, the presence of users is the most complicated one to be estimated. In order to solve this problem, two different installation solutions have been adopted.

The first solution is a generation system with thermal power higher than the maximum instantaneous requirement per year to satisfy the thermal requirement in a short time.

The second solution is a thermal generation system coupled with thermal storage. In the latter case the advantage is that the production of heat from the actual use, bearing the cost of a volume used as tank, which represents the thermal storage,

No solution is better than the other because each technology (boiler, heat pump, water heater) is more inclined to one of the aforementioned solutions.

The same is not true for the generation and use of electrical energy because the national electrical mains can be considered as a real electrical energy storage. Therefore the produced energy is often sold to the mains regardless of the generally very low sales price. On the contrary, in such a case, an electrical storage would maximize the energy saving in energy bills because of the self-consumption of the generated electrical energy, thus minimizing the sale to the mains.

Another peculiarity of the electrical storage is the reduction of the electrical power that is instantaneously requested , therefore preventing the national mains from isolating the load, if consumption is higher than the electrical power at the meter. The technologies able to generate both thermal and electrical energy are cogenerator and trigenerators. The difference between them is that cogenerators do not produce cold water, whereas trigenerators also produce cold water.

Although a specific reference is made to cogenerators in the following description, the present invention also relates to trigenerators, the only difference being the presence of a refrigerating machine and of an additional cold water tank, in addition to the software adapted to the specific case.

A cogenerator without thermal and electrical storage would be impaired by operation problems because during the year the thermal requirement is not always proportional to the electric load and vice versa. As a proof of the above, it is simply necessary to consider that instantaneous electrical and thermal peaks are almost always independent.

It is therefore mandatory to give electrical energy to the mains at a less advantageous price or disperse thermal energy in the environment. In order to solve this problem, it would be simply necessary to provide at least a thermal storage and also an electrical storage, if possible.

The electrical and thermal power of a large number of cogenerators is too high event in a block of flats, although generally speaking thermal power must be considered in order to estimate the actual convenience of a cogenerator, in addition to the global electrical output. The lower the thermal power at the partial loads, the more hours/year the cogenerator will operate, and the more electrical energy will be produced.

However, especially in case of high thermal peaks, the high number of operating hours requires a cumbersome thermal storage. So, it is necessary to choose a cogenerator with higher power, increasing the switch-on and switch-off cycles of the cogenerator, or to accept the volume increase of the tank of a thermal storage.

During the dimensioning of the energy system, the power of the cogenerator and the volume of the thermal storage must be considered together with the payback time of the solution. The purpose of the present invention is to eliminate the drawbacks of the prior art by disclosing an energy system for buildings that is efficient, efficacious, functional, versatile, not cumbersome and able to provide energy autonomy to the user, minimizing or eliminating energy expenses.

These purposes are achieved by the present invention with the characteristics of the independent claim 1 .

Advantageous embodiments will appear from the dependent claims.

The energy system for buildings of the invention provides for a cogenerator, one or more heat pumps, a sensible thermal energy storage, an electrical storage and a latent thermal energy storage by using phase change materials (PCM).

PCMs can store a large amount of thermal energy during the phase change and can release it afterwards. Therefore, with the same amount of thermal energy stored, PCMs take a much lower space.

However, PCMs have a very low thermal exchange coefficient and therefore the charge and discharge time is not instantaneous. For these reason, sensible thermal energy storage must be provided, which are able to provide hot water ready for use.

The electrical storage comprises one or more salt battery packs that are managed by an energy storage and management system, which is hereinafter defined as management system, such as the one disclosed in the Italian patent application No. 102015000021343 in the name of UNENDO ENERGIA ITALIANA SPA.

The electrical storage preferably comprises Ni-Sodium salt batteries that are basically similar to Na-S batteries in terms of performance, but intrinsically safer.

Considering that the operating temperature of this battery is about 300°C, the battery casing is characterized by a suitable thermal insulation to minimize the energy that is necessary to heat and keep the elements hot and reduce the thermal exchange with the surrounding environment.

Moreover, the energy system for buildings of the present invention can integrate a renewable source, such as for example photovoltaic, mini-wind or mini-hydro, in direct current with charge regulators that work directly charging the batteries. The purpose of this optional provision is to minimize the electrical consumption of the users because of the autonomy guaranteed by the battery pack.

The management system is the core of the energy system of the invention because it has the following functions:

- it manages and optimizes the production and energy flows of the cogenerator when the internal and external conditions change,

- it stores the excessive electrical energy in the batteries and supplies it in presence of higher electrical consumption at the user points,

- it insulates the user points from the electrical mains when it can satisfy the electrical consumption, otherwise it connects them to the electrical mains.

The type of cogenerator is a solid oxide fuel cell (SOFC) with a higher electrical output than the thermal one, i.e. with a generated electrical power higher than the supplied electrical energy. This type of fuel cell uses natural gas or, by means of internal reforming, it divides it into hydrogen that will produce electrical energy because of a solid oxide membrane and an exothermic reaction. The cogenerator totally produces more thermal energy than the amount required to maintain the reactions.

The main problems of this technology are the 8-hour switching-on time and the lower number of switch-on and switch-off cycle every year. According to the energy system of the invention, the cogenerator operates uninterruptedly throughout the year, modulating its thermal and electrical power when the external and internal conditions change.

Another characteristic of the energy system of the invention is that the cogenerator operates in parallel with one or more heat pumps. A control logic of the management system considers the type of heat pump installed, the end terminals at the user point and the external and internal conditions.

In order to satisfy the thermal requirement with solid oxide fuel cells only, cumbersome thermal energy storage tanks are necessary, in spite of the presence of PCMs and the payback time is very high. In order to solve such a drawback, the energy system of the invention comprises a heat pump that can use the electrical energy that is instantaneously produced by the cogenerator and produce thermal energy for heating and/or sanitary hot water. The heat pump does not necessarily need to be in the proximity of the cogenerator and of the two thermal energy storages (latent thermal storage with PCMs and sensible storage with hot water) and can be installed also in the proximity of the user point beside the sensible thermal energy storage of the user point. All hot water tanks (distributed sensible thermal energy storages) are in communication, although connections vary from case to case.

In view of the above, an algorithm has been developed for the optimization of the thermal energy generated by the heat pump in order to satisfy the hourly load for every day of the year. The software allows the cogenerator to make the users consume, instant after instant, more than 99% of the electrical energy generated during the year.

Because of the contribution of the heat pump and of its proper operation, in order to satisfy the thermal requirement, the cogenerator consumes less gas than a condensation boiler; the same is true also for the electrical requirement where the electrical energy required from the mains is very limited.

Additional features of the invention will appear evident from the detailed description below, which refers to a merely illustrative, not limiting embodiment, as illustrated in the attached figures, wherein:

Fig. 1 is a complete diagram block of the energy system for buildings according to the invention, which shows the water connections and the electrical connections for transmitting the electrical energy;

Fig. 2 is a block diagram that shows a user point of the system of Fig. 1 in detail;

Fig. 3 is a block diagram that shows the water connections of the centralized part of the system of Fig. 1 in detail, and;

la Fig. 4 is a block diagram of the system of Fig. 1 that only shows the electrical connections for the control signals. With reference to the figures, the energy system for buildings according to the innovation is disclosed, which is generally indicated with reference numeral (100). In the Figures, the water pipes to be heated are shown in black.

With reference to Figs. 1 and 2, the system (100) is applied to a plurality of user points (8), such as apartments.

The energy system (100) comprises:

- a cogenerator (1 ) intended to generate thermal energy and electrical energy,

- an electrical storage (3) to store electrical energy,

- a latent thermal energy storage (4) that is hydraulically connected to the cogenerator (1 ) to store the thermal energy produced by the cogenerator

(1 ) ,

- a centralized sensible thermal energy storage (5) that is hydraulically connected to the cogenerator (1 ) and to the latent thermal energy storage (4) to store the thermal energy produced by the cogenerator (1 ) or stored in the latent thermal storage (4),

- a heat pump (7) disposed in each user point (8) to generate thermal energy,

- a distributed sensible thermal energy storage (9) disposed in each user point (8), the distributed sensible thermal energy storage (9) being hydraulically connected to the centralized sensible thermal energy storage (5) and to the heat pump (7) in order to receive thermal energy from the centralized sensible thermal energy storage (5) and/or from the heat pump (7),

- a management system (2) electrically connected to the cogenerator

(2) , to the electrical storage (3) and to electric loads (82) of the user points (8) in order to receive the energy produced by the cogenerator (2) and use said electrical energy to load the electrical storage (3) and/or power the electric loads (82) of the user points.

The management system (2) is electrically connected to the electrovalves of a hydraulic circuit that connects the cogenerator (1 ), the latent thermal energy storage (4) and the centralized sensible thermal energy storage (5) to the heat pumps (7), as well as ambient sensors (87, 88) to control the thermal energy exchange according to the data detected by the ambient sensors.

With reference to Fig. 2, each user point (8) has an internal space (80) and an external space (81 ). A heat pump (7) is installed in each user point and is hydraulically connected to the distributed sensible thermal energy storage (9). Each heat pump has an internal unit (70) disposed in the internal space (80) and an external unit (71 ) disposed in the external space (81 ).

The distributed sensible thermal energy storage (9) is disposed in the internal space (80) of the user point and is hydraulically connected to the internal unit (70) of the heat pump. The user point (8) comprises electric loads (82), such as household appliances and devices that need to be electrically powered, among them the heat pump (7).

The ambient sensors comprise internal sensors (88) disposed in the internal space of each user point to detect the ambient conditions of the user point, as well as external sensors (87) to detect the ambient conditions of the external space. The ambient sensors (87, 88) are connected to the management system (2) by means of a signal line (26) (see Fig. 4)

With reference to Figs. 1 and 2, the cogenerator (1 ) simultaneously produces electrical and thermal energy.

The thermal energy produced by the cogenerator (1 ) is sent to the latent thermal energy storage (4) and/or to the centralized sensible thermal energy storage (5).

By means of an electrical cable (1 6), the electrical energy produced by the cogenerator (1 ) is sent to the management system (2) that converts it into electrical energy intended to power the battery pack (3) and feed the electric loads (82) of the user points by means of an electrical cable (25).

The control and the optimization of the energy flows, both in thermal and electrical terms, are made by a software implemented in a control logic (20) installed at the management system (2) following to an immediate or future request of energy from the heat pumps (7) and from the electric loads (82) of the user points (8).

Each user point (8) has its own heat pump (7). The internal unit (70) of the heat pump is coupled with the distributed sensible thermal energy storage (9).

The electrical storage (30) comprises a pack of primary batteries (30) to electrically power the electric loads of the user points, as well as a pack of support batteries (31 ) that are electrically connected to the management system (2) in order to switch the cogenerator (1 ) on.

The cogenerator (1 ) is an electrochemical device that produces electricity and heat without combustion. Advantageously, the cogenerator (1 ) is a solid oxide fuel cell (SOFC) cogenerator.

It must be considered that each type of fuel cell needs hydrogen to operate and this makes commercial diffusion difficult. However, unlike the other fuel cells, SOFCs do not need pure hydrogen because by operating at a high temperature (higher than 600°C) an internal reforming of the hydrocarbon takes places during the reactions and hydrocarbon is dissociated in hydrogen and carbon dioxide. Therefore SOFCs can directly use the mains gas (methane).

Therefore, in addition to fuel (methane), the complete reaction requires water vapor, oxygen and thermal energy and provides water, carbon dioxide, electrical and thermal energy. The reaction is fed automatically in presence of fuel because it generates more heat than requested to support the reactions.

As mentioned earlier, the only drawback of this technology is the switch-on time, which is approximately 8 hours. The problem can be solved by operating the cogenerator (1 ) in continuous mode, thus maximizing operation hours and reducing the number of switch on-off cycles.

The total efficiency of the cogenerator (1 ) can be higher than 90%, of which 50% is electrical and the remaining 50% is thermal. The electrical output is higher than any other generator of electrical energy from a thermoelectric source also because only chemical reactions - and not combustion - take place inside the cogenerator. In order to avoid wasting energy and money, the heat produced daily by the cogenerator (1 ) must not be higher than the heat requested by the user points (8). However, during the year, the demand for heating and sanitary hot water changes significantly from season to season, and the cogenerator is operated at a lower value than the operating power. However the capacity of the cogenerator to generate electrical and thermal energy at partial loads up to 30% makes it suitable for fulfilling the annual thermal demand of the user points.

Considering that thermal loads for heating are null in summer, and only the thermal loads for sanitary hot water are present, the cogenerator must be dimensioned suitably to satisfy the minimum requirement when operating at minimum partial loads (therefore slightly higher than 30%).

With reference to summer cooling, the cogenerator is not able to produce cooling energy. Therefore, if required by the users, the heat pump (7) of each user point must be reversible or the energy system (100) must comprise a refrigerating machine and a cold storage.

With reference to Fig. 3, the cogenerator (1 ) comprises:

- a gas inlet pipe (1 1 ) connected to the gas distribution mains,

- a fume discharge conduit (12) in communication with the outside, - a delivery pipe (13) in communication with the latent thermal energy storage (4) in order to send hot water to the latent thermal energy storage (4),

- a return pipe (14) connected to the centralized sensible thermal energy storage (5) in order to return the water from the centralized sensible thermal energy storage,

- a drain pipe (15) for condensed water.

With reference to Fig. 1 , the cogenerator (2) comprises:

- an outgoing electrical cable (1 6) connected to the management system (2) in order to send the electrical energy produced to the management system (2),

- an ingoing electrical cable (17) connected to the management system

(2) in order to switch the cogenerator (1 ) on by means of the support battery (31 ). The cogenerator may comprise a wireless transceiver for a remote control system with GPRS 2G/3G coverage.

The cogenerator (1 ) operates directly with the mains gas at the ordinary operating pressure. Instead, the water to be heated circulates in a closed hydraulic circuit in communication with the latent thermal energy storage (4) and/or with the sensible thermal energy storage (5). For this purpose, the system (100) comprises flow switch valves (V1 , V2) disposed in the delivery pipe (13) and in the return pipe (14) and managed by the control logic (20).

The electrical connections (1 6) of the cogenerator (1 ) reach the control system (2) that manages the electrical energy produced to charge the battery pack (3, 30), or transforms the electrical energy from direct to alternate for the electric loads (82) of the user points (8).

In compliance with the technical standards, the room where the cogenerator (2) is installed must be provided with suitable safety devices, such as for example gas detectors, a NC safety electrovalve installed on the natural gas power line, an accessible shut-off valve with manual actuation installed upstream the system.

Advantageously, the latent thermal energy storage (4) is a heat exchanger comprising phase change materials (PCM). PCMs do not have the only purpose of accumulating a large amount of heat. In fact, during the winter, PCMs can provide thermal energy together with the heat generators represented by the cogenerator (1 ) and/or the heat pumps (7). Therefore, the sum of the two thermal powers to be generated can be lower than the one that is requested instantaneously, with a consequent saving on the electrical consumption of the heat pump (7).

Moreover, the management system (2) is used to select the privileged electric loads and ensure that the power limit at the meter of the electricity supplier of the user point is not exceeded.

When they reach the melting or freezing temperature, many PCMs continue on either storing or yielding heat, always remaining at the same temperature. When the phase change material is completely liquid or completely solid, the temperature of the body will increase or decrease again.

In addition to the melting (or freezing) temperature, other important measures are:

- high latent melting heat by unit of volume;

- low costs and availability in nature or on the market;

- high specific heat to increase the quantity of sensible heat stored;

- material not flammable, explosive, poisonous or corrosive for the container;

- small or null volume variations during the phase change;

- chemical stability without decomposition also with high numbers of thermal cycles completed.

As mentioned above, when choosing a PCM, the most interesting measure is the melting temperature. This is because the melting temperature of phase change materials must be:

- higher by at least 10°C than the temperature used for the centralized sensible thermal energy accumulation (5), which will then feed the distributed sensible thermal energy storage (9) of the user points.

- lower by at least 10°C than the maximum temperature of the hot water coming from the delivery pipe (13) of the cogenerator.

Moreover, almost all phase change materials have a certain number of charge and discharge cycles after which the PCM must be replaced because it is chemically unstable or because its melting (or freezing) heat has decreased excessively. Therefore, in consideration of the cost and the deterioration of some of these materials for the high number of charge/discharge cycles, it is recommended to suspend (especially in summer) the operation days of the latent storage (4) in such manner to optimize the useful life of the PCMs. Therefore, in summer, the cogenerator (1 ) will directly heat the centralized sensible storage (5) by means of the shut- off valves (V1 , V2) that will be completely closed towards the latent thermal energy storage (4). The melting temperature of the PCMs is also very important because it affects the actual efficacy of the latent thermal energy storage (4). If the melting temperature is too high or too low, this affects the charge time and the PCMs are not efficacious.

The latent thermal energy storage (4) is provided with the following water connections:

- a first inlet (42) of hot water coming from the delivery pipe (13) of the cogenerator (1 );

- a second inlet (44) of water to be heated coming from a conduit (54) connected to the centralized thermal energy storage (5), wherein a first shut- off valve is installed (11 );

- a first outlet (43) of water to be heated directed to the cogenerator (1 ), by means of a conduit (46) connected to the second 3-way valve (V2);

- a second outlet (45) of heated water towards the centralized thermal energy storage (5), by means of a conduit (47) connected to the centralized sensible storage (5), wherein a second shut-off valve is installed (12);

The 3-way valves (V1 , V2) and the shut-off valves (11 , I2) are electrovalves controlled by the control logic (20) (as shown in Fig. 4)

The shut-off valves (11 , I2) are closed when the cogenerator (2) is directly connected to the sensible thermal energy storage (5), in such manner to by-pass the latent thermal energy storage (4).

The centralized sensible thermal storage (5) comprises:

- a first hot water inlet connected to the conduit (47) coming from the latent thermal energy storage (4),

- a second hot water inlet connected to the by-pass conduit (58) connected to the first 3-way valve (V1 ) in order to let the hot water from the cogenerator (2) enter;

- a first outlet of water to be heated connected to the conduit (54) connected to the inlet (44) of the latent thermal energy storage (4) to send water to be heated to the latent thermal energy storage,

- a second outlet of water to be heated connected to the return pipe (14) with the second 3-way valve (V2). - a third outlet connected to an outlet conduit (51 ) for hot water directed towards the distributed sensible thermal energy storage (9);

- a third inlet connected to an inlet conduit (52) coming from the distributed sensible thermal energy storage (9).

The centralized sensible thermal energy storage (5) does not provide for heat exchange coils to use the heat stratification properties of water. Moreover, this guarantees that the heat-carrying fluid that provides heat to the end terminals is the same for the entire useful life of the heating system, without the need of being continuously filtered as it happens when the sanitary hot water and the heating water are mixed.

At the end of the heating period, the outputs for the end terminals are closed and the hot water from the centralized sensible thermal energy storage (5) is pumped into the distributed sensible thermal energy storages (9). The distributed sensible thermal energy storages (9) are provided with one coil heat exchanger (91 ). The circuit of the exchanger contains water that, when heated to the desired temperature, is sent as sanitary hot water. Therefore the sanitary hot water circuit (89) is insulated from the heating circuit of the apartment.

The volume of hot water required by the user points (8) is variable throughout the year and on a hourly basis. For this reason, the distributed sensible thermal energy storage (9) is provided in each user point (8), which is able to supply sanitary hot water and heating water for the apartment.

The distributed sensible thermal energy storage (9) is a puffer disposed under or near each heat pump (7) used for the user points (8). The distributed sensible thermal energy storages (9) are connected to the centralized sensible thermal energy storage (5) by means of corresponding conduits (51 ).

In necessary, the hot water coming from the centralized sensible thermal energy storage (5) is either completely or partially conveyed to the distributed sensible thermal energy storages (9) so that the latter can supply the thermal energy required by the user point (8). In particular, with reference to Fig. 2, each distributed sensible thermal energy storage (9) comprises:

- the coil heat exchanger (91 ) used to heat the sanitary hot water;

- a first inlet connected to the conduit (51 ) of hot water coming from the centralized sensible thermal energy storage (5);

- a first outlet connected to the conduit (52) of water to be heated and directed to the centralized sensible thermal energy storage (5);

- a second inlet connected to a conduit (92) of hot water coming from the internal unit (70) of the heat pump;

- a second outlet connected to a conduit (93) of water to be heated that is directed towards the internal unit (70) of the heat pump.

The two inlets and the two outlets of the distributed sensible thermal energy storage are not provided with heat exchange coils in order to use the heat stratification property of water.

The heat pumps (7) depend on the type of end terminals, i.e. on the type of internal unit (70). In fact, in case of radiators, high-temperature heat pumps are provided, whereas, in case of fancoils and radiant panels, medium temperature or geothermic heat pumps are provided.

Considering that the performance of air-water heat pumps worsens when the external temperature decreases, systems to pre-heat the air that enters the heat pump (7) can be provided and used in the hottest times of the day, storing the heat produced in the centralized sensible thermal energy storages (9).

Moreover, the importance of the heat pump (7) consists in that if all thermal energy is produced only by multiple cogenerators (1 ), a higher gas consumption and a production of electricity generally much higher than consumption is generally obtained . In such a case, the user point (8) returns a high amount of electrical energy into the electrical mains (Mains) and profit from such a sale of electricity is lower than the cost borne for the extra gas consumption. In view of these considerations, it has been decided to use the energy system (100) of a heat pump (7) for each user point, in such manner that the gas consumed by the cogenerator (1 ) is even lower than the benchmark (condensation boiler) and the electrical energy produced by the cogenerator (1 ), net of the quantity self-consumed by the heat pump (7), reduces as much as possible the electrical consumption of the electric loads (84) of the user point (8).

In addition to the internal hydraulic circuit composed of the conduits (92 and 93) that connect the internal unit (70) to the distributed sensible thermal energy storage (9), every heat pump (7) has an external hydraulic circuit that comprises a delivery pipe (75) and a return pipe (76) between the internal unit (70) and the external unit (71 ) of the heat pump.

The heat pump (7) has an electrical connection (73) to satisfy its own energy consumption and a control connection (74) (see Fig. 4) for the control logic (20) that manages the switch-on and the switch-off of the heat pump (7) when the internal and external conditions detected by the ambient sensors (88, 87) change.

The installations designed to use renewable energy and cogeneration for residential and industrial use that are currently available on the market are characterized by the common feature of introducing all the energy produced, net of self-consumption, in the public electrical mains. Such a configuration is known as "mains-connected installation"; therefore, the users self-consume only part of the produced energy and the remaining part is introduced in the mains where the total community of consumers will use the introduced energy.

By using the control system (2), each user point (8) can increase its self-consumption of electrical energy because the cogenerator (1 ) can reduce by itself the energy taken from the mains. Because of the control logic (20) of the management system (2) the energy taken from the mains is further reduced. In such a way, the public mains is used only when the sum of the electrical energy produced by the cogenerator (1 ) and the electrical energy stored in the batteries (3) is lower than the instantaneous electric load of the user point.

The management system (2) manages the production, optimization and storage of thermal and electrical energy. Its main purpose is to store the electrical energy produced by the cogenerator (1 ) in the salt batteries during high-production time and make such electrical energy available during high- consumption time, such as in the evening or at night or to give higher power to the load, such as the heat pump.

Each user point (8) comprises a 3-way relay (83) connected to the electrical power supply coming from the management system (2), to the electrical mains (Mains) and to the electric loads (82) of the user points. The 3-way relay (83) is connected to the logic (20) of the management system to switch and manage the electrical consumption.

In presence of sufficient energy produced by the cogenerator (1 ), the management system (2) switches the relay (83) in such manner to insulate the mains and power the electric loads of the user points (8) with the energy produced by the cogenerator, increasing direct self-consumption with the maximum efficiency. In this case the management system (2) is in BY-PASS state.

When the management system (2) is in BY-PASS state, it can be switched to STORAGE mode and take energy from the cogenerator (1 ), in a modulated coordinated way with the management system in order to load the electrical storage (3), still satisfying the electric load of the user points (8).

If the batteries of the electrical storage (3) are completely charged and the requested electric load is lower than the electrical production of the cogenerator (1 ), the management system (2) can no longer self-consume all the produced energy, and operates one or more heat pumps (7) if more thermal energy must be produced to satisfy the daily thermal demand. In this case the control system (2) goes to FEED-IN status.

When the instantaneous electric load is higher than the electrical energy produced by the cogenerator (1 ), the management system (2) checks that the energy available in the salt batteries (30) is sufficient and in such a case goes from STORAGE or FEED-IN state to power supply state in order to support the missing part of the electrical energy demand. So the management system (2) goes to INVERTER state, providing all the power requested by the user points (8) through the electrical storage (3), net of the electrical energy produced by the cogenerator (1 ). Otherwise, when the batteries (30) are not able to supply the missing part of the electrical energy demand, the management system (2) switches one or more relays (83) of the user points (8) that cannot feed, starting to take the energy from the electrical mains and no longer from the energy system (100) to feed the user points that require energy. The management system (2) goes to PARTIAL OR TOTAL MAINS state.

When switching the relays (83), the energy system is completely insulated from the electrical mains, with a system configuration of TN-S type (locally earthed neutral) in such manner to keep the functions of the differential protections and of all household appliances that need a neutral referred to earthing and not a floating one. In such a way, the user has a continuous service for all types of electric loads, including the most sensible ones, because energy can be instantaneously taken from the electrical mains.

For the connection in alternate current (AC) to the relay (83), the system needs three single-phase inlet/outlet lines with earthing, neutral and phase conductors, for a total of 9 connections. The inlet lines have access to the control and connection panel from the bottom of the battery compartment through three different lines, which are protected with Diflex-type spiral sheath with 1 6 mm diameter. The terminal board for connection of these lines can have max. no. 2 cables with 6mm2 section for each pole of the 3 lines.

The electrical storage (3) advantageously comprises Ni-Sodium salt batteries. In terms of performance, the Ni-Sodium battery is basically similar to the Na-S battery, but it is intrinsically safer. In fact, the reactions that occur inside the battery do not determine gas production, preventing any gas leakage. In such a way, it is not necessary to provide a ventilation system in the battery room because there are no dangerous emissions to be diluted.

In the Ni-Sodium battery the two electrodes are in melted state and divided by a separator made of ceramic material, β-alumina that allows the ionic passage. The positive electrode is composed of nickel chloride and is immersed in a liquid electrolyte composed of a sodium tetrachloroaluminate (with respect to which it is insoluble), whereas the negative electrode is composed of sodium.

The electromotive force of a sodium/nickel chloride cell at an operating temperature of 300°C is 2.58 V and is independent from the charge status of the cell.

In order to obtain a homogeneous reliable structure the elementary cell is generally of small dimensions, thus having a small capacity. Therefore, in order to obtain a battery with a certain total capacity and a certain voltage at the terminals, it is necessary to connect a very high number of elementary cells in series and parallel mode. Each element is hermetically closed in steel containers and insulated with a double mica layer to prevent short circuits. Three protection levels are provided by the stainless steel, namely the single cell container, the cell container and the external case.

The battery casing is characterized by a suitable thermal insulation to minimize the energy that is necessary to heat and keep the elements hot and reduce the thermal exchange with the surrounding space. The cooling system is not necessary, the external temperature of the battery is only a few degrees higher than the ambient temperature.

The performance of the Ni-Sodium battery is very similar to the Na-S battery. The modules that are available on the market, which comprise heating system, insulation and BMI (Battery Management Interface), have a specific energy of 100 -130 Wh/kg (which corresponds to an energy density of 1 60 -190 Wh/I) and to a specific power of 1 60 - 190 W/kg (approximately 260 - 290 W/l).

The energy output of the battery is very high, with values around 80 -

93 % according to the work cycle. Like the Na-S battery, the performance of the battery is not affected by the ambient temperature, as a consequence of the high thermal insulation, and the amperometric output is practically unitary.

In addition to the battery pack (30) for the user points (8), also a small support battery pack (31 ) is provided, with the purpose of satisfying the electric load required by the cogenerator (1 ) during the switch-on. Both batteries (30, 31 ) are managed by the control logic (20). The energy system (100) must adapt to the climatic conditions and to the end terminals (internal unit (70) of the heat pump) that are variable from case to case. The main purpose of the control logic (20) is to manage the energy flows and produce the amount of heat or thermal energy that is necessary to the total demand of the user (8). The software of the control logic (20) is based on mathematical formulas that guarantee the simple implementation in the control logic (20).

The axioms of the software are:

- the sum of thermal energy generated by the cogenerator (1 ) and by the heat pump (7) must be equivalent to the daily thermal requirement and simultaneously the electrical energy produced by the cogenerator (1 ) must follow the electric load (82) required by the user point (8) and by the heat pump (7) that is suitably modulated instant by instant;

- the thermal energy generated by the cogenerator (1 ) must provide heat to the latent thermal energy storage (4) and/or to the centralized and distributed storage (5 and 9) if, for example, the phase change materials (PCM) of the latent thermal energy storage (4) are already completely charged;

- the thermal energy generated by the heat pump (7) must heat the distributed thermal energy storages (9) for sanitary uses and heating;

- if the temperature of the centralized thermal energy storage (5) is under a preset lower limit, the latent thermal energy storage (4) provides the requested thermal energy;

- the PCMs contained in the latent thermal energy storage (4) can be simultaneously charged and discharged;

- if the heat pump (7) is air-water, it must be operated in the hottest times of the day to increase its COP and consequently decrease the gas consumption of the cogenerator (1 ), increasing cost saving;

- if the total electric load is lower than the electrical energy produced by the cogenerator (1 ), the electrical storage (3) is recharged and discharged if the requested load is higher than the electrical production (until a preset limit); - if the total electric load is higher than the sum of the electrical energy produced by the cogenerator (1 ) and the energy supplied by the electrical storage (3), one or more end user points (8) are connected to the electrical mains instead of in island configuration (i.e. by the cogenerator (1 ) and by the salt batteries (3) through the management system (2)).

The initial inputs to be provided to the software in order to adjust with a proper starting accuracy are:

- number of user points (8) to be served;

- average number of people estimated in each user point (8);

- position and climatic conditions of the place where the user points are installed;

- thermal requirement of each user point;

- rated power of each heat pump (7) and minimum power at partial loads of each heat pump;

- COP of the heat pump declared in the data sheet;

- maximum energy that can be stored by the PCMs in the latent thermal energy storage, as well as charge and discharge time;

- maximum energy that can be stored by the salt batteries of the electrical storage (3).

The hardware has been designed taking into consideration these algorithms and the variable requirements. The firmware for the microcontroller of the management system (2) has been integrated with communication protocols with control units, GSM module and amperometric transformers, and with an optimized charge/discharge algorithm of the electrical storage (3). To collect the data provided from the control units, a database on a web server has been implemented, which may provide remote control by the user points.

Numerous variations and modifications can be made to the present embodiments of the invention, which are within the reach of an expert of the field, falling in any case within the scope of the invention as disclosed by the attached claims.