The object of the present invention is a plant or system for energy and heat cogeneration that makes it possible to vary the operating parameters of the cogeneration cycle according to which the same system operates, upon variation of the desired balance between useful energy, defined as energy output from the system not in the form of heat and thus for example as electrical power, and the heat output from the same system, involving lower costs compared to the currently known systems.

At present, systems for the cogeneration of useful energy and heat usually have a condensation circuit and a vapour circuit. These systems operate according to an operating cycle in accordance with which the working fluid leaves the evaporator in the form of vapour and thus in the gaseous state, and enters the turbine, where it undergoes a pressure and temperature drop, so as to produce useful energy as output from the same turbine and the same system. The working fluid then enters the condensation circuit where it is cooled so as to pass into the liquid state to produce heat as output from the system. Subsequently, the same working fluid is compressed by means of a pump to increase the pressure and temperature, so that it is subsequently subjected again to evaporation in the evaporator, so as to return to the gaseous state.

During the summer months, given that there is less demand for heat, increased thermodynamic efficiency of the cycle is sought, and upon the increase thereof, the useful energy or power output from the system is increased in relation to the energy or power input into the system. In particular, this useful energy or power can be of the electrical type, and it is defined as "useful" in the present description in that it is not in the form of heat.

The minimum temperature for the cycle in the summer months, or in any case when there is less demand for heat or thermal power output from the system, must thus be kept at the lowest possible level to increase thermodynamic efficiency, which increases proportionally to the ratio of the maximum temperature for the cycle, which is the evaporation temperature, to the minimum temperature for the cycle, which is the condensation temperature. The condensation temperature is that of the working fluid exiting the condenser or that of the working fluid exiting the condensation circuit.

In the winter months, however, as the demand for heat output from the cogeneration system is more pronounced, maintaining a higher minimum temperature for the cycle is sought. In fact, the coefficient of performance, and thus the ratio of heat output from the system to energy input into the system, increases with a decrease in the difference between the maximum temperature and minimum temperature for the cycle.

The variation of the condensation temperature determines a necessary variation of the pressure and/or temperature ratio at which the turbine must operate. Considering that the isentropic efficiency of the turbine varies as a function of the pressure ratio and thus of the temperature ratio between the outlet from and inlet to the turbine, the turbine is designed so that its isentropic efficiency, which can be considered as its intrinsic efficiency, is at a maximum level at a given optimal pressure or temperature ratio. In the case of the turbine, which is a working machine, the pressure ratio can be defined as the expansion ratio.

The deviation from the expansion ratio at which the turbine must operate, with respect to the optimal expansion ratio thereof, the deviation being caused, in turn, by the change in the condensation temperature, can lead to the increase in the cycle thermodynamic efficiency or the increase in its coefficient of performance being negatively compensated by a decrease in this intrinsic efficiency of the turbine.

At present, in large-scale systems, variable geometry turbines are thus used, which are therefore capable of keeping their intrinsic efficiency as constant as possible even upon variations in the condensation temperature for the cycle. Variable geometry turbines are very costly, particularly when the space available for the plant requires the use of turbines of small dimensions. The aim of the present invention is to develop a system or plant for the cogeneration of energy by means of which the balance between useful heat and energy output from the system can be varied, with lower costs compared to the currently known systems or plants for the cogeneration of energy.

This aim is achieved by means of a system in accordance with at least one of the claims appended to the present application, or in accordance with any combination of one or more of these claims.

The characteristics of the present invention can be clarified further by reading the following detailed description provided by way of non-limiting example of the concepts claimed.

The following detailed description refers to the attached figure, of which Figure 1 is a block diagram of a possible embodiment of a cogenerative plant or system according to the present system.

The system 1 comprises an evaporator circuit E, a generator unit G, a condensing circuit C and a pump P.

The generator unit G is suitable for producing useful energy or power as output from the system 1.

The condensation circuit C is suitable for producing heat or thermal power as output from the system 1.

The vapour circuit E comprises the actual evaporator, but it can also comprise the vapour circuit conduits and other components positioned on the same vapour circuit such as a preheater for example.

The vapour circuit E comprises the actual condenser, but it can also comprise conduits of the condensation circuit C and other components positioned on the condensation circuit such as compression means or exchangers or coolers.

The system 1 is configured to operate according to an operating cycle in which a working fluid sequentially passes through the vapour circuit E, the generator unit G, the condensation circuit C and the pump P, to then return to the vapour circuit E and thus repeat the cycle, according to the arrows in Figure 1 interposed between blocks G, C, P and E.

This working fluid can be a fluid comprising an organic substance, in which case this system 1 can be considered an Organic Rankine Cycle (ORC) machine.

Between the outlet from the condensation circuit C and the inlet into the vapour circuit E, and between the outlet from the vapour circuit E and the inlet into the condensation circuit C, the system 1 defines an intermediate circuit, which can be defined as a cooling circuit. For example, this intermediate circuit can be an HFC circuit and it is indicated by the number 2.

The working fluid enters the vapour circuit E in the liquid state and subsequently leaves the vapour circuit E in the gaseous state, to then re- enter the condensation circuit C after having passed through the generator unit G, while remaining in the gaseous state.

The fluid enters the condensation circuit G in the gaseous state and subsequently leaves the condensation circuit C in the liquid state, to then re-enter the vapour circuit E after having passed through the pump P, while remaining in the liquid state.

In the embodiment appearing in Figure 1 , the pump P and the generator unit G are located on two respective sections of the intermediate circuit 2. In the block representing the vapour circuit E, the condensation circuit C or the intermediate circuit 2, other components may be present, including for example valves, sensors, tanks, and heat exchangers, the latter for example being suitable for improving the efficiency of the operating cycle. For example, a regenerator can be present to act in such a manner that the fluid exiting the generator unit G contributes to heat the fluid exiting the pump P, and therefore in such a manner that the fluid exiting the pump P contributes to cool the fluid exiting the generator unit G. In the embodiment shown, the generator unit G comprises a first turbine T1 and a second turbine 12. The first turbine T1 and the second turbine T2 are in parallel.

The first turbine T1 and the second turbine T2 are in parallel in that, along the intermediate circuit 2, the generator unit G is interposed between a first point P1 of this intermediate circuit downstream of said vapour circuit E and a second point P2 of said intermediate circuit 2 upstream of said condensation circuit C.

Therefore, the generator unit G must operate at an expansion ratio equal to the ratio of the pressure at point P2 to the pressure at point P1 , short of relatively small losses in load that can have an influence on these pressures, and at a temperature ratio equal to the ratio of the temperature at point P2 to the temperature at point P1 , short of relatively small heat exchanges that can have an influence on these temperatures.

The system 1 comprises a selector unit 3 configured to select only said first turbine T1 or only said second turbine T2 so that once said fluid has entered said generator unit G, it passes alternatively through said first turbine T1 or said second turbine T2, respectively.

Therefore, this selector unit 3 is configured to act in such a manner that said fluid, in passing from said first point P1 to said second point P2, passes alternatively through the first turbine T1 or the second turbine T2. In an alternative embodiment, the selector unit 3 can also be configured so as to divide into parts the flow of fluid towards the first turbine T1 or the second turbine T", so as to vary the amount of fluid that is introduced into the first turbine T1 and the amount that is introduced into the turbine T2, so that these same turbines could also be operating simultaneously.

It should be noted that the first turbine T1 is configured and optimized to produce thermal energy output for winter operation. In other words, the first turbine T1 has an outlet in which thermal energy is produced (e.g. conduit with hot water or heat exchanger). The second turbine T2 is configured to produce electrical energy as output for summer operation. In other words, the second turbine T2 has an outlet in which electrical energy is produced (e.g. electric cable).

Should the fluid pass through this first turbine T1 and not the second turbine T2, the same first turbine T1 would be the one that produces the useful energy or power as output from the system 1 , and the second turbine T2 would be in the non-operative state. Should the fluid pass through this second turbine T2 and not the first turbine T1 , the second turbine T2 would be the one that produces the useful energy or power as output from the system 1 , and the first turbine T1 would be in the non- operative state.

The first turbine T1 differs from the second turbine T2 as concerns the efficiency trend of the respective turbine as a function of the expansion ratio and/or the temperature ratio of the turbine. In this manner, the decrease in the intrinsic efficiency of the generator unit G, due to the variation of the condensation temperature for the cycle, is significantly reduced or even completely eliminated. In fact, the first turbine T1 or the second turbine T2 can be selected by means of said selector unit 3, on the basis of which one of them has a greater efficiency for the expansion or temperature ratio at which the generator unit G must work, an expansion or temperature ratio that changes as a function of the change in the condensation temperature for the cycle of the system 1.

The efficiency of the turbine can be the isentropic efficiency, which varies upon variation of the expansion ratio, which is the ratio of the outlet pressure to the inlet pressure in the turbine, and thus also upon variation of the temperature ratio, which is the ratio of the outlet temperature to the inlet temperature in the turbine.

The selector unit 3 comprises an entry conduit 3a in said generator unit G. The selector unit 3 comprises a first inlet conduit 3b and a second inlet conduit 3c that branch off from said entry conduit 3a. The first inlet conduit 3b is suitable for directing the fluid towards the first turbine T1 and for introducing this fluid into this first turbine T1. The second inlet conduit 3c is suitable for directing the fluid towards the second turbine T2 and for introducing the fluid into this second turbine T2.

The first inlet conduit 3c has at least a first valve 3d located on this first inlet conduit 3b and that is suitable for enabling or preventing the entry of said fluid into the first turbine T1. The second inlet conduit 3d has at least a second valve 3e located on this second inlet conduit 3d and that is suitable for enabling or preventing the entry of said fluid into the second turbine T2.

One possible process for use of a system 1 according to the embodiment of the present invention shown in the attached figure comprises a first stage, an intermediate stage and a second stage.

In this first stage, the generator unit G produces useful energy by means of this first turbine T1 and the system 1 potentially produces heat by means of the condensation circuit C. In this first stage, the second turbine T1 is in a non-operative state. During this first stage, the selector unit 3 selects the first turbine T1 and therefore the second valve 3e is closed. The intermediate stage comprises varying the condensation temperature of the fluid at the outlet from the condensation circuit C and, by means of this selector unit 3, selecting the second turbine T2.

In this first stage, the generator unit G produces useful energy by means of this second turbine T2 and the system 1 potentially produces heat by means of the condensation circuit C. In this second stage, the first turbine T1 is in a non-operative state. During this second stage, the selector unit 3 selects the second turbine T2 and therefore the first valve 3d is closed. The generator unit G is preferably suitable for the production of electrical power as output from the system 1 , by means of at least one of either the first turbine T1 or the second turbine T2. The generator unit G is preferably associated with a connection point. These first T1 and second T2 turbines are both connected to this connection point by means of a single electrical energy converter (e.g. an inverter). In particular, it should be noted that the connection at the outlet of the two turbines T1 and T2 can be made by means of a parallel panel or another device not expressly indicated herein.

The operation of the system 1 in this first stage can be defined, for example, as winter operation. During the winter there is a greater demand for heat, so that it is important to obtain a good ratio of heat output from the system 1 to the energy or power that needs to be supplied to the system 1. With the maximum temperature for the operating cycle being equal, the condensation temperature, which is usually the minimum temperature for the cycle, is kept at a first level, which can be defined as the first condensation temperature. For example, this first condensation temperature can be equal to 63 degrees centigrade.

During winter operation, it is the first turbine T1 that operates to produce useful energy or power as output from the system 1 because this is the turbine that has, for example, higher efficiency for the expansion ratio or the temperature ratio deriving from the first condensation temperature, and at which the first turbine T1 must therefore operate in this first stage.

The operation of the system 1 in this second stage can be defined, for example, as summer operation. During the summer there is less demand for heat, so that it is important to obtain a good ratio of useful energy or power output from the system to the energy or power that needs to be supplied to the system 1. With the maximum temperature for the operating cycle being equal, the condensation temperature, which is the minimum temperature, is kept at a second level, which can be defined as the second condensation temperature. This second condensation temperature is lower than the first condensation temperature, so as to increase the thermodynamic efficiency of the cycle. For example, this second condensation temperature can be equal to 26 degrees centigrade.

During this summer operation, it is the second turbine T2 that operates to produce useful energy or power as output from the system 1 because this is the turbine that has, for example, higher efficiency for the expansion ratio or the temperature ratio deriving from the second condensation temperature, and at which the second turbine T2 must therefore operate in this second stage.

There could also be more than two turbines in the generator unit G, in which case the selector unit comprises a number of inlet conduits, each one being suitable for introducing the fluid into a respective turbine and each one being associated with a respective valve that is suitable for varying the flow rate of fluid entering the respective turbine, and thus also for eliminating this flow rate.

The system 1 can be associated with a control unit configured to control the selector unit 3.

The described embodiment according to the present invention makes it possible to develop an ORC machine that allows for selection between different turbines that operate in an optimal manner at different temperatures, according to the needs.