Description Field of the art

This invention relates to a cogeneration plant (or system). More specifically, a plant for supplying electrical or thermal energy to private homes, public buildings, offices, laboratories, hotels or industrial sheds. More specifically, this invention is intended for cogeneration plants with an output of less than or equal to 50 kW, better known in technical jargon as "micro-cogenerators" or "micro- cogeneration plants".

Cogeneration means the simultaneous production of various forms of energy (typically electrical energy and thermal energy) starting from a single source (generally a fossil gas or biogas). The principle on which the cogeneration is based is that of recovering the heat generated during the production of electrical energy, otherwise dispersed into the environment, and re-using it as thermal energy. The cogeneration plants comprise an endothermic engine or gas turbo-generator which, by the combustion of the fuel used, generates mechanical energy and heat. The mechanical energy is transferred to an alternator for producing electricity, whilst the heat (for example from the exhaust fumes) enters into a heat exchanger which transfers it to a water circuit.

The water heated in this way may be used for household or industrial purposeT ^{^} a^ording to requirements. Cogeneration is cun-ently ^" used ^~ irT many energy production fields. The same thermoelectric power stations have cogeneration cycles in which the water is heated and successively introduced into a circuit for the remote heating of small urban centres located close to the power station. These plants are able to produce megawatts of power, both electrical and thermal.

The plant according to this invention can be applied in more localised environments requiring smaller outputs. Consequently, this invention finds a particular use for the supply of electrical or thermal energy for private homes, public buildings, commercial premises, offices, laboratories, hotels or industrial sheds. Typically, these plants are positioned on the roofs of buildings or in basements, or in rooms used as thermal power stations, or in the open air, at the edge of the buildings to be supplied. The plants such as that of this invention are connected downstream of the electricity mains supply (for example, the ENEL grid) in parallel operation and to an accumulation of hot water fed by the heat of a heat exchanger; the cogeneration plant is powered by mains fuel (for example, methane gas), or by stored fuel (an LPG bottle, biogas storage, etc...)- The electrical energy produced by the cogeneration plant supplies the electrical equipment which is at that time requesting power, whilst the water heated by the plant is circulated in the water supply network for heating the building itself or for sanitary purposes. Taking as an example the case of a hotel, the cogeneration plant will cover the basic electricity and thermal energy consumptions, or it may modulate the energy production according to the instantaneous requirements of the building for electricity and/or hot water (electrical and/or thermal tracking). These cogeneration plants comprise an endothermic engine with one or more gas cylinders, a generator operated by the endothermic engine for producing electricity, a heat exchanger located between the cooling circuit of the engine and, in general, another heat exchanger connected to the building's water system. Lastly, these cogeneration plants preferably comprise an electronic control system for control of the mechanical, electrical and thermal functions. The electricity produced may be introduced into the grid directly (with a synchronous or asynchronous generator) or through an inverter. More specifically, inverter means a "rectifier-inverter" conversion unit supplied by the alternating current developed by the alternator. The inverter is used to vary the voltage and frequency of the alternating current at the input relative to the output.

The electricity produced by^he cogeneration plant has the characteristics required by the regulations for parallel operation with the public grid.

Description of the Prior Art

The prior art cogeneration plants have various drawbacks. In the case in which a single cogeneration unit does not have the necessary power to satisfy the specific needs, two or more twin units are installed.

This means that the prior art plants can be modulated, in that each single unit constitutes a module which may be repeated various times according to the needs. Disadvantageous^, this solution multiplies the number of components (two alternators, two heat exchangers, etc ..) and multiplies the overall dimensions.

Large spaces are not always available for installing more than one cogenerator unit. Moreover, this solution is very costly as in order to satisfy the energy requirements the user is forced to purchase several complete units and then connect them, thus multiplying all the system connections.

The prior art plants typically comprise an internal combustion engine designed for motor vehicles and then adapted for operation for a cogenerator. It is evident, therefore, that these engines, since they are not specifically designed for the cogeneration plants but for locomotion, cannot have the efficiency, compactness and output required for energy production.

The technical purpose which forms the basis of this invention is to propose a cogeneration plant that overcomes the above mentioned drawbacks of the prior art.

Summary of the Invention

More specifically, the aim of this invention is to provide a cogeneration plant which allows various configurations on the basis of the production of the desired power without having to install more than one complete cogeneration unit.

Another aim of the invention is to provide a cogeneration plant that can be configured relative to the power and having a compact structure with minimum dimensions.

Yet another aim of this invention is provide a cogeneration plant which has an extremely high thermal efficiency, minimising dissipation of the heat produced by the internal combustion engine.

The technical purpose indicated and the aims specified are substantially achieved by a cogeneration plant comprising the technical features described in one or more of the appended claims. Brief Description of the Drawings

Further features and advantages of the invention are more apparent in the non-limiting description which follows of a preferred non-limiting embodiment of a cogeneration plant illustrated in the accompanying drawings, in which:

Figure 1 shows a schematic block diagram of a plant according to this invention in a possible operating configuration;

Figure 2 shows a perspective view of a plant according to this invention; Figure 3 shows an exploded perspective view of a driving unit of the plant according to this invention;

Figure 4 shows the crank mechanisms and a distribution system of two driving units and the relative connections between the parts; Figure 5 shows a pan for the lubricating oil of the endothermic engine and a heat transmission device for transferring the heat from the oil to a thermal carrier liquid;

Figure 6 shows an intake manifold for supplying the driving units of the endothermic engine.

Description of the Preferred Embodiments of the Invention

With reference to the accompanying drawings, the numeral 1 in Figure 1 denotes a cogeneration plant (or system).

The plant 1 comprises an endothermic engine, that is, an internal combustion engine 2. The engine 2 is specially designed for the application in the cogeneration plant 1 according to this invention and is powered preferably by methane gas, LPG or biogas. The engine 2 operates according to a four-stroke cycle with controlled ignition. The distribution system operates with rods-rockers, which is an extremely reliable construction solution. It must be considered that this engine 2 is designed for thousands of hours of continuous operation, so all its components must guarantee a high level of reliability.

A distinctive feature of this engine 2 is that it comprises one driving unit 3 which may be connected to another driving unit 3, preferably identical to the first, for obtaining a predetermined total power from the engine 2. This is possible because the single driving unit 3 comprises connecting means 4 for connection to a further driving unit 3 for obtaining a predetermined total power from the engine 2. In other wordsTthe possibility of connecting several driving units 3 together makes the engine 2 modulable in power according to the specific needs of the cogeneration plant 1 and its application.

In the minimum configuration the engine 2 comprises a single driving unit 3, in the other configurations the engine 2 may comprise, two, three or four driving units 3 connected to each other. Each single driving unit 3 comprises two cylinders 20 positioned opposite each other, that is, positioned at an angle of 180°, forming two combustion chambers 21. In other words, the single driving unit 3 is a two- cylinder unit in a boxer configuration. The displacement of the single cylinder 20 may vary between 50cc and 400cc. Preferably, the cylinder 20 has a displacement of 200cc, so the single driving unit 3 has a displacement of 400cc. The driving unit 3 comprises an engine casing 22 which constitutes the supporting structure for the entire driving unit 3. The driving unit 3 also comprises a crankshaft 23 for transferring the mechanical power generated by the engine 2. The crankshaft 23, which is rotatably associated in the engine casing 22, moves a connecting rod 24 connected to a piston 25, which is slidably associated with the cylinder 20. The crankshaft 23, the connecting rod 24 and the piston 25 define the crank mechanisms 5 of the driving unit 3. The boxer configuration means that it is not necessary to house a balancing countershaft in the engine casing 22. Due to their spatial positioning, the counteropposing cylinders 20 automatically balance the angular accelerations generated by the crank mechanisms 5, thereby producing fewer vibrations compared with other configurations.

The structural connection made by the connecting means 4 on each driving unit 3 allow the engine casing 22 of the single driving units 3 to be connected. In the preferred embodiment, the connecting means 4 of a first driving unit comprise a flange 26 which can be connected, by tightening means, preferably bolts, to a further flange 26 made on a further driving unit 3. The single driving units 3 are also connected at the crankshafts 23. More specifically, a crankshaft 23 of a driving unit 3 can be connected to a further crankshaft 23 of a further driving unit 3. The mechanical power produced by the combustion in the combustion chambers 21 of the single driving unit 3 is transmitted to the crankshaft 23 which is thereby rotated. By connecting several driving units 3, the crankshafts 23 are also connected in such a way that the power produced by the single driving units 3 is conveyed to a single crankshaft 23 for transmitting the mechanical power produced by the engine 2. The engine casing 22 is preferably made from aluminium alloy to make the engine 2 ^" ighTm weightT

The driving unit 3 comprises a distribution system 16 which in turn comprises a rods-rockers device 17 for moving the valves 18 driven by a camshaft 19. The camshaft 19 is connected to the crankshaft 23 and this drives the rods-rockers 17 and, therefore, the valves 18. Thus, as is the case for the crankshaft 23, the camshaft 19 of a driving unit 3 can also be connected to a further camshaft 19 of a further driving unit 3.

Thus, the engine 2 may comprise, in an embodiment, a plurality of driving units 3 aligned with each other. The driving units 3 extend at different heights along a main direction of extension "P". Thus, the driving units 3 are lined up with each other along the main direction of extension "P" which is substantially vertical. Advantageously, this allows the surface dimensions of the cogeneration plant 1 to be kept unchanged with variations to the size of the engine 2. In other words, the plant 1 has a standard (lateral) size irrespective of the size of the engine, which may also be varied during the life of the plant according to changes to the users without adversely affecting the surrounding buildings.

Advantageously, too, the number of connections to the outside (electrical, thermal, fuel supply and exhaust gases) is maintained substantially unchanged.

It should be noted that the main direction of extension "P" coincides with the axis of rotation of the crankshafts 23 of the various driving units 3 and that direction defines an extension in height of the entire engine 2.

The engine 2 comprises a liquid cooling circuit 28. More specifically, the cooling circuit 28 operates on each driving unit 3. The cooling liquid passes through the sleeves of the cylinders 20 removing in part the heat produced by the combustion. After collecting the heat from the cylinders 20 the cooling liquid enters a heat exchanger 6 connected to the cooling circuit 28 and connectable to an existing water circuit in the building in which the cogeneration plant 1 is installed. In other words, the heat exchanger 6 is operatively associated with the engine 2 for recovering in part the heat produced by the engine 2.

The engine 2 also comprises a pan 10 for the lubricating oil.

Obviously, all the parts moving relative to each other need lubricating to achieve a longer working life of the engine 2. Therefore, all the crank mechanisms 5, the combustion chambers 21 defined by the cylinders 20, the pistons 25 and the engine casings 22 are lubricated by the engine oil contained in the pan 10. The pan 10 is therefore in fluid connection with each driving unit 3. More specifically, the

the driving units 3, depending on the configuration. Yet more specifically, the pan 10 is connected to the lowest driving unit 3 along the main direction of extension P and positioned beneath it. In other words, the pan 10 is positioned beneath the driving unit 3 of the lowermost engine 2.

The pan 10 also comprises a heat transmission device 11 which is operatively associated with the water circuit of the building for transferring heat from the oil to the water circuit. More specifically, the heat is exchanged between the engine oil and the thermal carrier liquid. The thermal carrier liquid may be conveyed in the heat exchanger 6. Generally, the thermal carrier liquid may be a predetermined heat exchange liquid which is circulated inside the heat exchanger 6. The thermal carrier liquid may be directly that contained in the water circuit of the building. In this latter case, the thermal carrier liquid is generally the water which, after being heated in the cogeneration plant 1 , is introduced into the water circuit of the building.

This heat transmission device 11 is positioned on a base surface 13 of the pan 10 having the lowest height along the aforementioned main direction of extension P. In other words, the heat transmission device 11 is positioned on the lower base surface 13 of the pan 10 in such as way as to collect the heat from the oil contained in the pan 10. More specifically, the heat transmission device 11 comprises a coil 12 for transit of the thermal carrier liquid and it extends on the base surface 13 of the pan 10. The coil 12 is formed by a shaped body 14 which is comprised in the heat transmission device 11. The shaped body 14 is positioned on the base surface 13 of the pan 10 and it is made in one piece with the pan 10. Lastly, the heat transmission device 11 comprises a cover 15 connected to the pan 10 at its base surface 13. The cover 15 is operatively associated with the coil 12 for forming a thermal carrier liquid transit channel, that is, the coil 12.

The heat transmission device 11 is integrated in the oil pan 10. The device 11 is made by two aluminium shells coupled by a gasket. The cavities for transit of the thermal carrier cooling liquid (typically water), which is obviously different from the lubricating liquid, are made on the faces of the two shells.

With regard to powering the engine 2, each driving unit 3 comprises a tubular portion 30 which can be connected to a further tubular portion 30 of a further driving unit 3 for forming an intake manifold 35. Each driving unit 3 also comprises at least two ducts 31 in fluid connection with the tubular portion 30 at one end and with the combustion chambers 21 of the cylinders 20 at another end, for introducing an air/gas mixture into the combustion chambers 21. The tubular portion 30 is connectable to an air filter (not illustrated) for introducing air necessary for the combustion into the combustion chambers 21. The tubular portion 30 comprises connecting means 32 for connecting to the further tubular portion 30 of the further driving unit 3. In other words, the modularity in the structural and operational connection of the single driving units 3 is also found in the system for powering the driving units 3. The single tubular portions 30, connected to each other, constitute a power supply manifold 35 of the engine 2. The power supply manifold 35 is designed for distributing the incoming air (from a single intake) guiding it towards the mixture through modular elements. Preferably, the manifold 35 has a plurality of metal separators for distributing the flow. The connecting means 32 may comprise an abutment shoulder 33 connectable to the corresponding one of a further tubular portion 30 using threaded elements, typically bolts. Each single tubular portion 30 comprises a separator 36 inside it where the ducts 31 are connected, for separating the flow of mixture entering the single ducts 31.

The engine 2 comprises a silencer 40 for the exhaust of the burnt gases, connected to each driving unit 3. The silencer 40 in turn comprises a device 41 for recovery of the heat from the burnt gases which performs a heat exchange between the burnt gases and a relative thermal carrier liquid. The thermal carrier liquid may be that used as heat exchange liquid in the heat exchanger 6. The thermal carrier liquid may be that circulating in the water circuit of the building. The recovery device 41 is operatively associable with the water circuit of the building for transferring the heat from the combustion gases to the water circuit. The association of the recovery device 41 with the water circuit of the building may be direct, or it may take place by transit of the relative thermal carrier liquid in the heat exchanger 6.

In other words, the recovery device 41 is a further heat exchanger for recovering the heat produced by the combustion and re-using the heat to increase the temperature of the thermal carrier liquid. The recovery device 41 may be connected to the heat exchanger 6.

The cogeneration plant 1 comprises a control unit C for controlling the combustion in the combustion chambers 21. The control unit C acquires various data regarding, for example, air/gas mixture, temperature of engine oil, temperature of cooling circuit, outside temperature and quality of combustion using a lambda sensor located on the silencer 40 for determining the optimum timing of the combustion ihTthe combustion ^Hambers ^~ 21 and lherefore obtain a greater output from the engine 2. This data is collected by various sensors, non illustrated, positioned on each driving unit 3.

Conveniently, the control unit C is able to process the data coming from the sensors in every configuration of the engine 2. More specifically, it may be configured in such a way that it may be adequately programmed to manage and process the data coming from the sensors in every configuration of the engine 2, for example with a single driving unit 3, with two, three of four driving units connected together. Alternatively, or in addition, the control unit C may also be modularly expanded, again in such a way that it may manage and process the data coming from the sensors in every configuration of the engine.2, for example with a single driving unit 3, with two, three of four driving units connected together. In one embodiment, several control units C may be used for control of the engine 2 under the control of a single processor.

In other words, the modularity of the engine 2 is also found in the control unit C for controlling the engine 2, preferably in terms of re-programmability (if the control unit C is sufficiently powerful), or internal expandability of the control unit C. In one embodiment, as mentioned, the modularity of the control of the engine 2 may be obtained by using, under the control of a single processor, several control units C.

The cogeneration plant 1 also comprises a power generator 7 connected to the engine 2 for producing a predetermined quantity of electric power.

More specifically, the power generator 7 may be a synchronous or asynchronous alternator for generating alternating current electric power. The generator 7 is connected, preferably coaxially, to a driving unit 3 and it is aligned relative to it. The generator 7 is positioned, along the main direction of extension P, at a height higher than the driving unit 3, and, therefore, higher than the engine 2. In other words, the generator 7 is, following the direction of extension P, the component positioned the highest, followed by the engine 2 in its various configurations of driving unit 3 and, lastly, by the oil pan 10, which is positioned the lowest. Preferably, the power generator 7 comprises a plurality of modules 7a connected to each other by suitable reversible connecting means (not illustrated).

It should be noted that the number of modules 7a depends on the size of the engine 2 in order to generate power in proportion to the power generated by the engine 2.

Pre ^{^} ferably ^~ ^ach¾ ^~ 0dule ^~ 7a ίΓ sized for generating a power corresponding ^{^} to that of the single driving unit 3.

Advantageously, in this way the number of driving units 3 of the engine 2 corresponds to the number of modules 7a of the generator 7.

Preferably, the generator 7, consisting of one or more reversible electrical machines (which may operate both as generator and as engine), is also designed for starting the engine 2.

Consequently, the engine 2, whatever its modular configuration, starts with the same (modular) electrical machine 7 which subsequently acts also as generator. For the starting it will be necessary to draw a small quantity of electricity from the public electricity grid; once the engine 2 has been started, an electrical switching system allows the generator 7 acting as an engine to be disconnected from the grid and to reconnect it as soon as the conditions for parallel operation and introduction of electricity are created.

As shown, for example, in Figure 2, the generator 7 may be air cooled, using a suitable finning on its outer surface. As illustrated schematically in Figure 1, the generator 7 may, preferably, be liquid cooled. More specifically, the generator 7 may be coupled to a cooling device 70 comprising a relative cooling circuit in which a thermal carrier liquid circulates and which may be operatively coupled with the thermal carrier liquid used in the building. The cooling circuit of the cooling device 70 may be connected to the circuit of the thermal carrier liquid of the building either directly or, preferably, through the heat exchanger 6. The cooling device 70 is used to obtain a further recovery of heat from the cogenerator 1.

In certain cases, for example depending on the type of generator 7 used, the cogeneration plant 1 could also comprise an inverter 8 operatively connected to the power generator 7. The inverter 8 consists of a rectifier-inverter system for varying the voltage and frequency of the alternating current at the input relative to the output.

The cogeneration plant 1 in general comprises means of treating the electrical signal generated by the cogeneration plant 1, for synchronising the electrical signal with the signal of the electricity supply grid so as not to create unbalances and malfunctions. The means of treating the electrical signal may be comprised in the inverter 8.

The cogeneration plant 1 also comprises an electronic control system 9. The electronic control system is interfaced with a control panel 90. The control system 9 receives as input the electrical signals of the machine sensors and commands as output the necessary corrections. More specifically, the electronic control system is connected to the unit C for controlling the engine 2. In one embodiment, the control unit C of the engine 2 may be integrated in the control system 9. The control system 9 comprises a grid interface 91 which, after measuring the signal coming from the supply grid, is able to synchronise the introduction of signal/power into the grid and to disconnect the generator in the case of non-compliant parameters (voltage and frequency).

The control system 9 may be operatively connected to the inverter 8 and process the signal. The control system 9 manages the distribution of the supply of electric power from the cogenerator to the building and/or to the electricity supply grid on the basis of the load requested by the building and/or other use parameters. For this purpose, the control system 9 may use the grid interface 91. The building with its user devices is located downstream of the control system 9 (more specifically, downstream of the grid interface 91).

The control panel 90 may also be used as a user interface, for entering the parameters for operating and/or controlling the cogeneration plant 1.

The cogeneration plant 1 comprises a box-shaped body 50 whose inside forms a compartment 51 for receiving the engine 2 in any configuration.

In a first embodiment, the layout of the compartment 51 is provided with a "free" space along the direction of extension "P" of the engine 2, in which it is possible to introduce or remove driving units 3 for varying the size of the engine 2.

In other words, the compartment 51 has a standard size, substantially unique for all the embodiments of the plant 1 in which a sector 51a extending along the main direction of extension "P" of the engine 2 is sized for containing a plurality of driving units 3 in line with each other.

Thus, the sector 5 la is sized to house the engine 2 in any configuration.

Alternatively, the box-shaped body 50 has a modular configuration.

More specifically, the box-shaped body comprises a base 50a, a cover 50b both having predetermined surface dimensions and a plurality of auxiliary modules 50c interposed between the base 50a and the cover 50b (that is, which may be aligned with each other) for allowing the height of the box-shaped body 51 (and of the compartment 51) to be varied depending on the number of driving units 3 of the engine 2 and/or modules 7a of the generator 7.

Preferably, each auxiliary module 50c has at least one peripheral joining portion (preferably a plurality) which can be connected to a respective peripheral

with it.

The joining portions are formed by a snap fitting element and/or screwing elements or the like.

Preferably, in any event, the joining portions are reversibly connected to each other for allowing an installer to vary the output of the plant even during its service life.

Advantageously, in this way, the working space inside the box-shaped body

50 is maximised, reducing to a minimum the wasted space.

It should be noted that these modules all have substantially equivalent surface dimensions, in such a way that the variation in the number of modules does not influence in any way surface (lateral) dimensions of the plant 1.

The box-shaped body 50 also houses the control system 9 (and, if necessary, if present, the control panel 90 and/or the grid interface 91 and/or the inverter 8) for protecting it against the weather conditions, as the cogeneration plant is typically installed outside the buildings.

The invention described achieves the above-mentioned aims and has the above-mentioned important advantages.

The cogeneration plant according to this invention allows various configurations on the basis of the production of the desired power without having to install more than one complete cogeneration unit. The presence of a combustion engine consisting of one or more driving units which may be connected together allows the production of more or less power depending on the specific uses of the plant. The power generator guarantees the production of electricity which can be immediately used by the user in the same way that the heat exchanger recovers the heat produced by the combustion of the engine for heating the water of the water system of the building in which the cogeneration plant is installed. These components are such that the cogeneration plant has a high efficiency, using and recovering almost entirely the potential energy of the fuel used for the operation.