System for making hybrid heating systems more efficient

Abstract

The present invention relates to a system (100) for making hybrid heating systems more efficient, characterized in that it comprises a combustion heat generator (20) adapted to be powered by a fuel mixture comprising or consisting of hydrogen or a mixture of hydrogen and oxygen, an electrolyser (30) adapted to produce said mixture of hydrogen and oxygen, a heat pump (10) comprising a low-temperature heat source, at least one heat exchanger (40) connected to said electrolyser (30) and to said heat pump (10), said exchanger being adapted to recover the waste heat from said electrolyser (30) and to transfer it to an evaporator of said heat pump (10), an accumulation tank (70) for storing a thermal fluid produced by said heat generator (20) and / or by said heat pump (10), temperature sensing means, and a memory and a control unit connected to said temperature sensing means and to said memory in which the value of a maximum ambient temperature Tamb, a maximum temperature of the accumulation tank Tam, a minimum operating temperature of the heat pump Tmin and a maximum operating temperature of the heat pump or of the thermal fluid Tmax is saved, said control unit being configured to acquire the values of the temperature of said accumulation tank Tacc, of said low-temperature heat source of said heat pump TE and of the temperature of the environment to be heated TA by means of said temperature sensing means, check if said temperature of the environment to be heated TA is lower than said maximum temperature of the environment Tamb and said temperature of said accumulation tank Tacc is lower than said maximum temperature of the accumulation tank Tam and, if so, generate a signal to switch on said combustion heat generator (20) and said electrolyser (30), and check if said temperature of the low-temperature heat source of the heat pump TE is higher than the minimum operating temperature of the heat pump Tmin and said temperature of said accumulation tank Tacc is lower than the maximum operating temperature of the heat pump or of the thermal fluid Tmax and, if so, generate a signal to switch on said heat pump (10). The present invention also relates to a method for controlling a system for making hybrid heating systems more efficient.

Description

[0001] System for making hybrid heating systems more efficient

[0002] The present invention relates to a system for making hybrid systems for heating and the production of domestic hot water more efficient.

[0003] As is known, those systems where the generation of heat takes place through at least two distinct devices that work together and which are respectively defined as first heat source (or primary source or primary generator) and second heat source (or secondary source or secondary generator), such as for example a fuel heat generator and a heat pump are defined as hybrid systems. The devices of a hybrid heating system may also be multiple and comprise devices for heating from renewable sources such as solar thermal panels, as shown in figure 1 .

[0004] An example of a system for making hybrid systems more efficient is described in German patent application DE3413772 A1.

[0005] Current hybrid systems are provided with complex electronic control and regulation units. In the hybrid systems with different heat sources, such as a gas boiler and a heat pump, a particular temperature value, defined as the bivalence temperature, plays an important role. By correctly setting a bivalence temperature, also called a bivalence point, the optimal moment for switching on or off the second heat source can be ensured; or, if possible, the modulation thereof.

[0006] Preliminarily, it is possible to set a minimum value of external temperature, below which the heat pump must be deactivated. Heating will therefore be the exclusive responsibility of the secondary source (e.g. gas boiler). This makes sense because heat pump efficiency decreases with low external temperature values.

[0007] In addition, the bivalence temperature defines the temperature below which a second heat source is activated in tandem with the heat pump. In particular, in the range between the minimum external temperature and the bivalence temperature, both heat generators work in parallel. Above the bivalence temperature, the second heat source is switched off.

[0008] In addition, there are proposals in the prior art to use the heat produced by large electrolysers to increase energy efficiency. These are large systems that work many hours to produce hydrogen which is then stored to be sent to users. An example provided by the Siemens group is shown in figure 2.

[0009] In these systems, hydrogen is produced by the electrolysers regardless of the amount that users require at any given time and therefore must be stored. In addition, the dimensions of the electrolysers are such that the heat produced by them is considerable and is therefore associated with industrial users or coupled to district heating networks. In these contexts, the heat pumps of the hybrid systems are always of the water-water type and of great power. The investments required for this size of systems are considerable and the main reason for increasing the energy efficiency of hydrogen production lies in the need to reduce the return time of these investments.

[0010] There is, therefore, a need in the specific sector for a system capable of producing hydrogen and oxygen in the same place where the users of these chemical elements are, which are heat generators powered by fuel or biofuel.

[0011] In addition, there is a need in the specific sector for a system capable of allowing the simultaneous operation of heat sources regardless of the external temperature.

[0012] The aim of the present invention is thus to provide a system which makes it possible to overcome the limits of the systems according to the prior art and to achieve the technical results previously described.

[0013] A further aim of the invention is that said system can be produced at substantially low costs, both as regards the production costs and as regards the operating costs.

[0014] Yet another aim of the invention is to propose a system that is simple safe and reliable.

[0015] It is therefore a specific object of the present invention a system for making hybrid heating systems more efficient, characterized in that it comprises a combustion heat generator adapted to be powered by a fuel mixture comprising or consisting of hydrogen or a mixture of hydrogen and oxygen, an electrolyser adapted to produce said mixture of hydrogen and oxygen, a heat pump, at least one heat exchanger connected to said electrolyser and to said heat pump, said heat exchanger being adapted to recover the waste heat from said electrolyser and to transfer it to an evaporator of said heat pump, an accumulation tank for storing a thermal fluid produced by said heat generator and / or said heat pump, temperature sensing means, and a control unit connected to said temperature sensing means and to a memory in which the value of a maximum ambient temperature Tamb, a maximum temperature of the accumulation tank Tam, a minimum operating temperature of the heat pump Tmin and a maximum operating temperature of the heat pump or of the thermal fluid Tmax is saved, said control unit being configured to acquire the values of the temperature of said accumulation tank Tacc, of the low-temperature heat source of said heat pump TE and of the temperature of the environment to be heated TA by means of said temperature sensing means, check if said temperature of the environment to be heated TA is lower than said maximum temperature of the environment Tamb and said temperature of said accumulation tank Tacc is lower than said maximum temperature of the accumulation tank Tam and, if so, generate a signal to switch on said combustion heat generator (20) and said electrolyser (30), and check if said temperature of the low-temperature heat source of the heat pump TE is higher than the minimum operating temperature of the heat pump Tmin and said temperature of said accumulation tank Tacc is lower than the maximum temperature of the thermal fluid Tmax and, if so, generate a signal to switch on said heat pump (10).

[0016] A further object of the present invention is a method for controlling a system according to any one of the preceding claims, characterized in that it comprises the following steps:

[0017] A. reading the temperature of the internal environment TA and the temperature of said accumulation tank Tacc, and if said internal ambient temperature TA is lower than said maximum ambient temperature Tamb and said temperature of the accumulation tank Tacc is lower than said maximum temperature of the accumulation tank Tam, performing the following step

[0018] B. switching on said combustion heat generator and said electrolyser, otherwise performing step A,

[0019] C. reading the temperature of the heat pump TE and the temperature of said accumulation tank Tacc, and if said temperature of the heat pump TE is higher than the minimum temperature of the heat pump Tmin and said temperature of said accumulation tank Tacc is lower than the maximum temperature of the thermal fluid Tmax performing the following step

[0020] D. switching on said heat pump, otherwise performing step A.

[0021] The present invention will now be described, by way of non-limiting illustration, according to a preferred embodiment thereof, with particular reference to the figures of the appended drawings, in which:

[0022] - figures 1 -4 show the construction diagrams of a device according to the prior art,

[0023] - figure 5 shows a first schematic view of the system according to the present invention,

[0024] - figure 6 shows a functional diagram of the operating logic of the system according to the present invention,

[0025] - figure 7 shows a second schematic view of the system according to the present invention, and

[0026] - figure 8 shows a schematic view of a second embodiment of the system according to the present invention.

[0027] Referring to figures 5 and 7, a system for efficiency gain is indicated with reference 100.

[0028] In particular, said system 100 comprises at least one heat pump 10 (e.g. “Pdc” for “Heat pump” ) and at least one fuel heat generator 20. Alternatively, said heat pump 10 is an air-air, air-water or even water-water type heat pump. The operation of a heat pump 10 is well known and is illustrated in figure 3.

[0029] In particular, said heat pump 10 comprises: an evaporator 11 adapted to absorb heat from a low-temperature source by transferring heat to a refrigerant fluid that evaporates generating a refrigerant vapour, a compressor 12 that increases the pressure and temperature of the refrigerant vapour generated in said evaporator 11 , a heat exchanger 13 in which the refrigerant vapour, by condensing, releases heat to a thermal fluid, and an expansion valve 14 adapted to expand the flow of condensed refrigerant, further reducing its temperature before the refrigerant fluid is again sent to the evaporator 11 .

[0030] Furthermore, always referring to figure 3, said heat pump 10 comprises a tank 15 for the storage of said thermal fluid used for the utilities. Preferably, in embodiments not shown, said fuel heat generator 20 is a boiler, a hydrogen or oxygen (Brown gas) catalytic cogenerator, an internal combustion engine-based cogenerator or other device having the characteristic of benefiting from the addition of hydrogen to the primary fuel.

[0031] Furthermore, the primary energy source of said heat generator 20 may be natural gas / methane, biogas / biomethane, bioethanol / biomethanol, LPG, naphtha or diesel. In particular, said fuels are provided on-demand, i.e. in the quantity that the heat generator 20 requires at any given time. This type of model does not have a minimum size for it to be economically sustainable, and can be applied starting from the individual real estate units that today use autonomous heating.

[0032] Furthermore, still referring to figures 5 and 7, said system 100 comprises an electrolyser 30 for local use, which allows the simultaneous operation of the fuel heat generator 20 and the heat pump 10 regardless of the external temperature.

[0033] In particular, said electrolyser 30 allows to replace in whole or in part the fossil fuel that feeds the heat generator 20, and to improve the coefficient of performance (COP) of the heat pump 10 by recovering the heat produced during water electrolysis.

[0034] In particular, the hydrogen or a mixture of hydrogen and oxygen produced by said electrolyser 30 is sent as fuel to said fuel heat generator 20.

[0035] Thus, in the present invention, the two components of the hybrid system, i.e. fuel heat generator 20 and heat pump 10, work together and simultaneously instead of one at a time as in the prior art.

[0036] For the purposes of applying innovation, it is not relevant which type of electrolyser 30 is used, as long as the process involves the need to dispose of the heat generated. Similarly, it is not relevant that only hydrogen or a mixture of hydrogen and oxygen is supplied to the fuel heat generator 20. This depends on the technical characteristics of the fossil fuel heat generator 20 which also influences the choice of the type of electrolyser 30 to be used. However, the electrolyser 30 may be of any type except those at high temperature to which heat is to be supplied rather than recovered.

[0037] In the context of the present invention, efficiency gain is understood to mean the presence of at least one of the following two effects:

[0038]

[0001] increase in environmental efficiency through decarbonization, obtained by feeding the heat generator 20 with a percentage of hydrogen produced locally by said electrolyser 30 in replacement of all or part of the fossil fuel;

[0039] [2] improvement of the coefficient of performance COP of the heat pump 10 by raising the temperature of the external fluid, through heat exchange with the cooling circuit of the electrolyser 30.

[0040] In particular, in the system according to the present invention, the production of hydrogen takes place locally with a system without accumulation. In fact, the supply of hydrogen to the heat generator 20 by means of cylinders, both at low and high pressure, requires the supply of thermal energy during dispensing operation, which is therefore not available to obtain the effect of improving the COP (coefficient of performance).

[0041] Figure 4 shows the energy behaviour of a heat pump 10 as a function of the construction characteristics of the various types of heat pumps and of the thermal difference between the temperature of the external air and the supply water.

[0042] In particular, the coefficient of performance COP is defined as the ratio between energy yield (heat transferred to the environment to be heated) to electricity consumed. In figure 3, COP is equal to 4. As can be seen from figure 4, the temperature of the supply water is set - which depends on the type of thermal elements to which the heat must be provided (radiators, radiant floor, fan coils, domestic hot water, etc.) - the COP is higher the smaller the temperature difference. It is interesting to note that the COP increases rapidly - for the various types of machines available on the market - when the temperature difference becomes less than 30°C. In these cases, the efficiency gain is also of the economic type: the decrease in electricity consumption is greater than the increase in consumption due to electrolysis for the production of hydrogen.

[0043] Furthermore, the efficiency of a heat pump 10 that has air as an external source, thus an air-air or air-water heat pump, is not only affected by the external temperature but also by the relative humidity. With temperatures close to 0°C, the conditions are created for the formation of frost with consequent momentary interruption of the operation of the machine to implement the so-called defrosting. Also from this point of view, the heating of the air, before coming into contact with the evaporator 11 , entails a benefit: the operating conditions are distanced from the frost point.

[0044] Furthermore, referring to figures 5-7, said system 100 comprises a control logic unit 60. In particular, differently from the prior art, said control logic unit 60 allows the fuel heat generator 20 and the heat pump 10 to work simultaneously.

[0045] On the one hand, the addition of hydrogen reduces the carbon footprint that currently requires the fuel heat generator 20 to run as little as possible. On the other hand, the exploitation of the heat developed by the production of hydrogen improves the COP of the heat pump 10 by extending the operating range regardless of the external temperature.

[0046] In order to achieve the highest degree of energy efficiency, the criteria for Class VI and VIII thermoregulation systems according to European Directive ERP 813 / 2013 published in Italy with the commission 2014 / C307 / 02 are respected. With the options available in classes VI and VIII, it is possible to associate a 4% and 5% contribution to energy efficiency, respectively. This contribution, added to that of the other products of a heating system, favours the achievement of the efficiency class of the entire energy label. Consequently, the proposed system provides a series of sensors and probes for the detection of temperatures essential for proper operation, so as to fall within the aforementioned classes VI and VIII.

[0047] Still referring to figure 5, said system 100 comprises an accumulation tank 70 for storing said thermal fluid.

[0048] Figure 6 shows a flowchart of the operating logic of the system according to the present invention.

[0049] For simplicity of reading, in the diagram in figure 6 the representations of the logics relating to multiple environmental probes and the compensations for climatic curves and thermal inertia parameters of the system have been omitted. These follow the prior art.

[0050] In particular, the control logic is managed by two fundamental loops: the first one controls the ambient temperature TA with respect to a maximum value of ambient temperature Tamb defined and saved in the control logic unit 60, above which it is not necessary to provide heating, the second one controls the temperature Tacc of the accumulation tank 70 with respect to the maximum temperature value in the accumulation tank Tam defined and saved in the control logic unit 60.

[0051] When both these two conditions occur, i.e. when TA<Tamb and Tacc<Tam the system is switched on, i.e. the heat generator 20 and the electrolyser 30 are switched on. Furthermore, the control logic provides for a further loop to control the temperature TE at the outer side of the heat pump 10, i.e. the temperature of the source that transfers heat to the refrigerant fluid in the evaporator of the heat pump. In particular, the control logic provides for a control on the temperature TE and optionally waits for the heat recovered from the cooling of the electrolyser 30 to bring this temperature beyond the value Tmin, i.e. the minimum operating temperature of the heat pump 10. This Tmin value is set according to the technical characteristics of the heat pump 10 and the climatic zone where the system is installed.

[0052] When the temperature TE exceeds the minimum value Tmin, the control logic provides for a further control on the temperature Taco of the accumulation tank 70 with respect to the maximum temperature value for the operation of the heat pump 10. When both conditions occur, the heat pump is switched on and kept switched on until the temperature Tacc becomes higher than the temperature Tmax. As the temperature Tacc rises until it reaches the maximum temperature value in the accumulation tank Tam, this means that Tmax is also the maximum temperature of the thermal fluid used for utilities, which is therefore set not only based on the characteristics of the individual heat pump 10 but also on the characteristics of the utility-side heating system. Therefore, when the temperature Tacc becomes higher than the temperature Tmax, the heat pump is switched off by the control logic.

[0053] Ultimately, the range Tmin - Tmax is the temperature range for the operation of the heat pump 10. With modern inverter heat pumps the power is modulated based on the difference between the temperature Tmax and the temperature T of the thermal fluid.

[0054] Still referring to figure 7, the principle of operation of the present invention to obtain efficiency gain described above is illustrated in detail in said figure. In addition, the system shown in figure 7 is the system representation of the functional diagram shown in figure 5. The principle consists in replacing a part of the traditional fuel with hydrogen or, as shown in figure 7, with a mixture of hydrogen and oxygen, also called Brown gas (H2+O2). The percentage of fuel that can be replaced is very variable and depends on the combination of the type of heat generator and the type of fuel. In any case, the principle that a part of molecules containing carbon is replaced with the hydrogen molecule that is devoid of it applies. The possible simultaneous supply of oxygen aims at limiting the formation of nitrogen oxides that would result from oxidising hydrogen with atmospheric air. Furthermore, the cost of an electrolyser without a separator membrane is considerably lower than the cost of an electrolyser with a separator membrane, which would be necessary to oxidize hydrogen with air.

[0055] Still, in the embodiment shown in figure 7, said system 100 comprises a second heat exchanger 40 adapted to cool the electrolyser 30. Said second exchanger 40 is positioned in front of the evaporator 11 of the heat pump 10. Constructively, this can be achieved with a series of technical solutions whose details are not relevant for the purposes of this innovation. They will be chosen each time according to the different operating parameters of the selected electrolyser.

[0056] In the embodiment shown in figure 7, said heat exchanger 40 is of the fluidair type and comprises an air conveyor.

[0057] Further, the electrolytic solution circulating in said electrolyser 30 is sent to said second heat exchanger 40 to be cooled. In addition, the hydrogen or the mixture of hydrogen and oxygen is sent to the heat generator 20. The system of the present invention does not comprise a hydrogen tank to avoid the presence of tanks under pressure that could be dangerous in the boiler room.

[0058] For illustrative purposes - and without prejudice to the generalization in the application of innovation to concrete cases - one can imagine that said second heat exchanger 40 is a radiator provided with an electric fan. In particular, the external air is sucked in by the electric fan and the flow is conveyed through the radiator where the temperature increases before coming into contact with the surface of the evaporator 11 . The rest of the circuits of the heat pump 10 remain unchanged.

[0059] The embodiment shown in figure 7 may comprise a water-water type heat pump 10. In this embodiment it is possible to exploit geothermal energy, i.e. the heat of groundwater or soil.

[0060] In the present invention, instead of the groundwater or circulating water in the geothermal probes, the water of the cooling circuit of the electrolyser 30 is circulated. Since the temperature of the cooling circuit of the alkaline electrolysers / PEM / AEM is comprised in the range 50°C-70°C, a much lower amount of water is sufficient than in the geothermal case, where the temperatures are in the range 5°C-15°C.

[0061] Water-to-water heat pumps are generally larger than air-air or air-water heat pumps. They are used in larger systems, such as a building with dozens of apartments, a hotel, an office complex or a shopping centre. As a result, the fuel heat generators will also be larger and the electrolysers will also be cascade-like. These will frequently be of the membrane type, with separation of hydrogen from oxygen. The cooling circuit is then likely to be separate for the cathode compartment and for the anode compartment. In addition, the operating temperature of the electrolytic cells is higher with the consequent need to cool both hydrogen and gaseous oxygen.

[0062] Figure 8 shows a second embodiment of the present invention, in which the production of hydrogen and oxygen and their simultaneous separation take place. In particular, said embodiment is preferably applicable with water-water heat pumps. In said embodiment, the system 100 comprises four heat exchangers 50, respectively for cooling: the electrolyte circulating in the anode compartment (anolyte), the electrolyte circulating in the cathode compartment (catholyte), the hydrogen gas and the oxygen gas.

[0063] The fluid circuit that, by cooling the aforementioned four heat exchangers 50, acquires heat is connected to another heat exchanger 40 where it transfers the acquired heat to the fluid of the heat pump 10 that expands in the evaporator 11 . In this case the heat exchanger 40 is of the fluid-fluid type.

[0064] The present invention has been described by way of non-limiting illustration according to preferred embodiments thereof, but it is understood that variations and / or modifications may be introduced by the person skilled in the art without going outside the relevant scope of protection, as defined by the appended claims.

Claims

CLAIMS1 ) A system (100) for making hybrid heating systems more efficient, characterized in that it comprises a combustion heat generator (20) adapted to be powered by a fuel mixture comprising or consisting of hydrogen or a mixture of hydrogen and oxygen, an electrolyser (30) adapted to produce said mixture of hydrogen and oxygen, a heat pump (10) comprising a low-temperature heat source, at least one heat exchanger (40) connected to said electrolyser (30) and to said heat pump (10), said exchanger being adapted to recover the waste heat from said electrolyser (30) and to transfer it to an evaporator of said heat pump (10), an accumulation tank (70) for storing a thermal fluid produced by said heat generator (20) and / or by said heat pump (10), temperature sensing means, and a memory and a control unit connected to said temperature sensing means and to said memory in which the value of a maximum ambient temperature Tamb, a maximum temperature of the accumulation tank Tam, a minimum operating temperature of the heat pump Tmin and a maximum operating temperature of the heat pump or of the thermal fluid Tmax is saved, said control unit being configured to acquire the values of the temperature of said accumulation tank Tacc, of said low-temperature heat source of said heat pump TE and of the temperature of the environment to be heated TA by means of said temperature sensing means, check if said temperature of the environment to be heated TA is lower than said maximum temperature of the environment Tamb and said temperature of said accumulation tank Tacc is lower than said maximum temperature of the accumulation tank Tam and, if so, generate a signal to switch on said combustion heat generator (20) and said electrolyser (30), and check if said temperature of the low-temperature heat source of the heat pump TE is higher than the minimum operating temperature of the heat pump Tmin and said temperature of said accumulation tank Tacc is lower than the maximum operating temperature of the heat pump or of the thermal fluid Tmax and, if so, generate a signal to switch on said heat pump (10).2) A method for controlling a system (100) according to the preceding claim,and characterized in that it comprises the following steps:A. reading the temperature of the internal environment TA and the temperature of said accumulation tank Tacc, and if said internal ambient temperature TA is lower than said maximum ambient temperature Tamb and said temperature of the accumulation tank Tacc is lower than said maximum temperature of the accumulation tank Tam, performing the following stepB. switching on said combustion heat generator (20) and said electrolyser (30), otherwise performing step A,C. reading the temperature of the low-temperature heat source of said heat pump TE and the temperature of said accumulation tank Tacc, and if said temperature of the low-temperature heat source of said heat pump TE is higher than the minimum temperature of the heat pump Tmin and said temperature of said accumulation tank Tacc is lower than the maximum temperature of the thermal fluid Tmax, performing the following stepD. switching on said heat pump (10), otherwise performing step A.

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