Renewable energy generator set with steam engine and Stirling engine

Abstract

Title: Renewable Energy Generator Set with Steam Engine and Stirling Engine The invention relates to a generator set comprising: - a renewable energy boiler (1) producing high-pressure steam (101) from liquid water (100); - a steam engine (3) rotating a first transmission shaft (31) from the high-pressure steam (101); - a Stirling engine (4) rotating a second transmission shaft (41), the Stirling engine (4) using the steam exiting the steam engine (3), referred to as low-pressure steam (103), as the heat source for the Stirling engine (4); - at least one generator (6) to which the first transmission shaft (31) is coupled for producing electricity, and the second transmission shaft (41) for producing electricity. Figure for the abstract: Fig. 1

Description

Title of the invention: Renewable energy generator set with steam engine and Stirling engine

[0001] The field of the invention is that of the design and manufacture of generator sets.

[0002] The invention relates more particularly to a generator set using renewable energy.

[0003] Generator sets make it possible to produce electricity autonomously, and are widely used for example in agricultural settings because farms are often at the end of the power line and are subject to short but relatively frequent power cuts, or on construction sites without access to electricity.

[0004] In the field of the invention, there is known the French patent published under No. FR2869095 which describes a wood heating installation producing hot water and steam, the latter turning an alternator via a piston engine.

[0005] It is also known: - the patent document published under No. W02007079561, which describes a micro-power plant using the combustion of biomass to produce steam which turns a turbine to power a generator; - the French patent published under No. FR2901350, which describes a wood heating installation producing hot water and steam, the latter turning an alternator via a Stirling engine and the steam then being condensed and recycled; - the Taiwanese patent published under No. TW200819617, which describes a device converting biomass into electricity via a Stirling engine whose hot source is directly the combustion chamber, then using the remaining heat to produce steam for later use.

[0006] These devices do not, however, provide satisfactory yields, and more particularly in relation to their size.

[0007] The invention aims in particular to overcome this drawback of the prior art.

[0008] More specifically, the invention aims to provide a generator set with a better efficiency than what is permitted by the prior art.

[0009] The invention also aims to provide such a generator set which has a better performance / size ratio than is permitted by the prior art.

[0010] These objectives, as well as others that will appear subsequently, are achieved thanks to the invention, which relates to a generator set comprising: - a renewable energy boiler producing high-pressure steam from water; - a steam engine driving a first transmission shaft in rotation from high-pressure steam; - at least one generator to which the first transmission shaft is coupled to produce electricity; characterized in that it also includes a Stirling engine driving in rotation a second transmission shaft coupled to the generator(s) to produce electricity, the Stirling engine using steam from the steam engine, called low-pressure steam, as the hot source of the Stirling engine.

[0011] The generator set according to the invention has improved efficiency thanks to the additional mechanical energy provided by the Stirling engine which uses the steam coming out of the steam engine.

[0012] According to an advantageous feature, the generator set includes a condenser receiving water vapor under low pressure and producing liquid water, the Stirling engine being associated with the condenser to use the low-pressure steam located in the condenser as a heat source.

[0013] Combining the Stirling engine with the condenser makes it possible to obtain liquid water at the outlet of these two elements, without requiring a condenser with large dimensions.

[0014] The overall size of the generator set, in relation to its efficiency, is notably more advantageous than that of a generator set which would not have a Stirling engine, and which would include a more massive condenser to produce liquid water.

[0015] According to a preferred design, the boiler includes a heat exchanger in which liquid water is intended to be evaporated, and the liquid water from the condenser is sent into the heat exchanger.

[0016] The water used in the generator set thus circulates in a closed circuit.

[0017] It is then not or hardly necessary to supply additional water to the generator set during its operation.

[0018] According to an advantageous embodiment, the generator set comprises an airlock between the condenser and the heat exchanger, the airlock comprising an intermediate volume framed by two valves, one of which, called the cold valve, is located between the intermediate volume and the condenser, and the other, called the hot valve, is located between the intermediate volume and the heat exchanger. and the condenser, the airlock, and the heat exchanger form a flow path gravity towards the heat exchanger.

[0019] In this way, the replenishment of the heat exchanger with liquid water from the condenser is carried out in a simple and energy-efficient manner.

[0020] According to a particularly advantageous embodiment, the generator set includes a storage of combustible biomass in the form of particles, preferably in the form of pellets, and in that the boiler is a biomass boiler and includes a furnace fed with combustible biomass from the biomass storage via a conveyor, preferably a screw conveyor.

[0021] Thanks to this embodiment, the generator set does not use a fossil fuel such as gasoline or diesel, or gases, as an energy source.

[0022] The biomass used may correspond to shredded wood, or preferably, for example, to wood pellets.

[0023] A preferred feature, the generator set includes an automaton controlling an air supply and a biomass fuel supply to the biomass boiler according to a setpoint.

[0024] Such an automated system facilitates the implementation of the generator set and its regulation.

[0025] Preferably, the generator set includes an electric accumulator buffer associated with the generator.

[0026] It is thus possible to compensate for the inertia of the generator set in order to vary its water vapor production to rapid fluctuations in electricity consumption.

[0027] The invention also relates to a method for producing electricity from renewable energy in a generator set, comprising: - a stage of producing high-pressure steam from liquid water in a renewable energy boiler; - a stage of transforming high-pressure water vapor into a first mechanical movement by a steam engine; - a stage of electricity generation at least from the first mechanical movement resulting from the transformation stage; characterized in that it also includes: - a complementary step of transforming some of the calories contained in the low-pressure water vapor from the transformation step into a second mechanical movement, by a Stirling engine and in that during the electricity generation stage, electricity is also generated from the second mechanical movement.

[0028] This process has the same advantages as the generator set previously described.

[0029] Advantageously, the process includes, concurrently with the complementary step transformation, a step of condensation of water vapor under low pressure from the transformation step.

[0030] Preferably, the liquid water from the condensation step is reused for the high-pressure steam production step.

[0031] Other features and advantages of the invention will become more apparent upon reading the following description of various preferred embodiments of the invention, given by way of illustrative and non-limiting examples, and the accompanying drawings, among which: • [Fig.1] [Fig.1] is a schematic representation of an electric generator according to the invention; • [Fig.2] [Fig.2] is a schematic representation of an airlock between a condenser and a heat exchanger of a boiler of the electric generator according to the invention.

[0032] As can be seen on

[0033] With reference to [Fig.1], a generator set according to the invention is shown.

[0034] The generator set includes a renewable energy boiler 1 which produces high-pressure steam 101 from liquid water 100.

[0035] The boiler 1 includes a heat exchanger 11 in which liquid water 100 is evaporated.

[0036] According to a possible embodiment not shown, the renewable energy boiler 1 is a solar boiler, and uses solar radiation to evaporate liquid water 100.

[0037] According to the present embodiment, the renewable energy boiler 1 is a biomass boiler 1. The boiler 1 then comprises a furnace 12 in which the biomass is burned, and which is associated with the heat exchanger 11 to allow the evaporation of the liquid water 100.

[0038] For this purpose, the generator set includes a storage 2 for combustible biomass 20 in the form of particles. Preferably, the combustible biomass 20 in the form of particles consists of wood pellets. The storage 2 is then formed by a silo into which the wood pellets are fed and which flow to the bottom of the silo under the effect of gravity.

[0039] The generator set also includes a conveyor 21 which allows the furnace 12 to be supplied with combustible biomass 20 from storage 2.

[0040] This conveyor 21 can take the form of a screw driven into rotation by means of a motor.

[0041] Boiler 1 further comprises: - an air supply 13 including for example a motor whose rotation propels a flow of air (illustrated by the dotted arrow) into the oven 12; - means of ash removal 14.

[0042] The boiler 1 produces high-pressure steam 101, for example at a temperature of 200°C and a pressure of 20 bar.

[0043] The generator set, as illustrated by [Fig.1], also includes a steam engine 3.

[0044] This steam engine 3 drives a first transmission shaft 31 in rotation thanks to the high-pressure steam 101 produced by the boiler 1.

[0045] This steam engine 3 can, for example, take the form of a piston engine. The steam engine 3 can also take the form of a steam turbine.

[0046] Upon exiting the steam engine 3, the water vapor is under low pressure. In other words, the water vapor has been decompressed by its work in the steam engine 3.

[0047] For example, low pressure water vapor 103 can be at a pressure of 5 bar.

[0048] The generator set further includes a Stirling 4 engine. Stirling 4 engines are well known prior art engines, and correspond to external combustion engines with a closed-cycle working fluid, using a hot source and a cold source.

[0049] This Stirling engine 4 drives a second transmission shaft 41 in rotation thanks to the calories present in the low-pressure water vapor 103.

[0050] The low-pressure water vapor 103 thus forms the hot source of the Stirling engine 4.

[0051] The cold source is formed by the ambient air surrounding the Stirling engine 4.

[0052] To this end, this Stirling engine 4 includes a radiator assembly, advantageously provided with cooling fins. A fan can advantageously be integrated into the generator set in order to send an airflow over the cooling fins.

[0053] The Stirling engine 4 may also include a heat transfer fluid circuit associated with the radiator component in order to optimize cooling, and thus maintain a stable temperature of the cold source formed.

[0054] According to the present embodiment, the generator set includes a condenser 5.

[0055] This condenser 5 receives water vapor under low pressure 103 and produces liquid water 100.

[0056] As illustrated, the condenser 5 is associated with the Stirling engine 4. The Stirling engine 4 thus uses the low-pressure steam 103 located in the condenser 5 as a heat source.

[0057] The Stirling engine 4 thus participates in the condensation of water vapor under low pressure 103 into liquid water 100.

[0058] According to one conceivable embodiment, the generator set also includes means for heat exchange serving as an interface between the low-pressure steam 103 and the Stirling engine 4.

[0059] These means of heat exchange may include a heat transfer fluid circuit, for example an oil circuit.

[0060] In this case, the Stirling engine 4 uses low-pressure steam 103 as a heat source indirectly through the oil circuit which serves as an interface.

[0061] This oil circuit can be integrated into the condenser 5.

[0062] The heat exchange means may also include transfer fins extending into the condenser. These transfer fins may be traversed by the heat transfer fluid circuit, or extend from a block incorporating the heat transfer fluid circuit.

[0063] According to the present embodiment, the liquid water 100 from the condenser 5 is sent into the heat exchanger 11 of the boiler 1.

[0064] As a result, the water circulates in the generator set in a closed circuit.

[0065] To send the liquid water 100 from the condenser 5 to the heat exchanger 11, the generator set includes an airlock 9 between the condenser 5 and the heat exchanger 11.

[0066] With reference to [Fig.2], the airlock 9 includes an intermediate volume 91 which is framed by two valves: a cold valve 92, and a hot valve 93.

[0067] These valves are in particular solenoid valves which include an open port O and a closed port F.

[0068] The cold valve 92 is located between the intermediate volume 91 and the condenser 5.

[0069] The hot valve 93 is located between the intermediate volume 91 and the heat exchanger 11.

[0070] As illustrated by [Fig.2], the axis of gravity F and its direction are represented by an arrow.

[0071] The condenser 5, the airlock 9, and the heat exchanger 11 form a gravity flow path G towards the heat exchanger 11. This gravity flow path G extends along the gravity axis F in the direction of gravity, and preferably parallel to the gravity axis F.

[0072] According to one conceivable embodiment, the generator set could include a pump for injecting the liquid water 100 produced by the condenser 5 into the heat exchanger 11.

[0073] An operating cycle of the airlock 9 is described below.

[0074] The valves are initially in a closed state. The intermediate volume 91 then comprises high-pressure steam 101.

[0075] First, the cold valve 92 opens. The pressures then equalize between the intermediate conduit and condenser 5, and intermediate conduit 91 fills with liquid water 100 from condenser 5, and empties with high-pressure water vapor 101.

[0076] The cold valve 92 is then closed, and then the hot valve 93 is opened. Pressure equalization occurs between the intermediate pipe 91 and the heat exchanger 11 of the boiler 1, and the intermediate pipe 91 empties its liquid water 100 into the heat exchanger 11 and fills with high-pressure steam 101.

[0077] The hot valve 93 can then be closed.

[0078] With reference to [Fig. 1], the generator set comprises at least one generator 6 to which is coupled the first transmission shaft 31, and the second transmission shaft 41 to produce electricity.

[0079] According to the present embodiment, the generator set comprises a generator 6 for each transmission shaft.

[0080] According to one conceivable embodiment, the first transmission shaft 31 and the second transmission shaft 41 are formed by a single transmission shaft and the generator set then includes transmission means allowing the mechanical movements from the steam engine and the Stirling engine to be adapted to each other, and this single transmission shaft is coupled to a generator 6.

[0081] The generator set also includes: - an electric buffer accumulator 7 associated with the generator(s) 6; - means of supplying electricity 8 including an inverter and / or a voltage regulator, associated with the generators 6 and the electric buffer accumulator 7.

[0082] In order to adjust the generator set's consumption to demand, the generator set includes an automated system (not shown)

[0083] This automaton includes an electronic processing unit, sensors and actuators enabling the control and modification of the operating parameters of the generator set.

[0084] The automaton performs in particular a control of the air supply 13 and the fuel biomass supply 20 of the biomass boiler 1 according to a setpoint, and more specifically by modifying the rotation speed of the air supply motor, and of the motor driving the rotation of the biomass supply screw.

[0085] This setpoint can be predefined via a human-machine interface, or it can be automatically adjusted by the PLC, for example, based on the operating parameters detected from the power supply means 8 and / or the electric buffer accumulator 7. For example, detecting an increase in electricity consumption and a decrease in the charge of the electric buffer accumulator 7 is likely to lead to an increase supplying furnace 12 with biomass and air to increase the heat produced.

[0086] The various parts of the generator set described above are advantageously designed to be integral with a chassis. This chassis allows the generator set to be transported as a whole. For example, the chassis can be attached to a vehicle or a trailer.

[0087] The chassis can also be self-supporting to allow the generator set to be placed at a place of use using lifting means.

[0088] The generator set described above implements a process for producing electricity from biomass in a generator set, comprising: - a stage of producing high-pressure steam 101 from liquid water 100 in a renewable energy boiler 1, and more specifically from biomass such as wood pellets; - a step of transforming water vapor under high pressure 101 into a first mechanical movement by a steam engine 3, this first mechanical movement corresponding to the rotation of the first transmission shaft 31; - a complementary step of transforming part of the calories contained in the low-pressure steam from the transformation step into a second mechanical movement, by a Stirling engine 4, this second mechanical movement corresponding to the rotation of the second transmission shaft 41; - a stage of generating electricity from the first mechanical movement from the transformation stage, and also from the second mechanical movement from the complementary transformation stage.

[0089] Furthermore, concurrently with the additional transformation step, the process includes a step of condensing the low-pressure steam 103 produced by the transformation step. This produces liquid water 100 which is advantageously reused for the step of producing high-pressure steam 101.

[0090] The characteristics of the generator set described above are applicable to the electricity production process.

Claims

Claims

1. Generator set comprising: - a renewable energy boiler (1) producing high-pressure steam (101) from liquid water (100); - a steam engine (3) rotating a first transmission shaft (31) from the high-pressure steam (101); - at least one generator (6) to which the first transmission shaft (31) is coupled to produce electricity; characterized in that it also comprises a Stirling engine (4) rotating a second transmission shaft (41) coupled to the or one of the generators (6) to produce electricity, the Stirling engine (4) using the steam leaving the steam engine (3), called low-pressure steam (103), as a heat source for the Stirling engine (4).

2. Generator set according to the preceding claim, characterized in that it comprises a condenser (5) receiving the low-pressure water vapor (103) and producing liquid water (100), the Stirling engine (4) being associated with the condenser (5) to use the low-pressure water vapor (103) located in the condenser (5) as a heat source.

3. Generator set according to the preceding claim, characterized in that the boiler (1) comprises a heat exchanger (11) in which liquid water (100) is intended to be evaporated, and in that the liquid water (100) from the condenser (5) is sent into the heat exchanger (11).

4. Generator set according to the preceding claim, characterized in that it comprises an airlock (9) between the condenser (5) and the heat exchanger (11), the airlock (9) comprising an intermediate volume (91) framed by two valves, including one valve, called the cold valve (92), located between the intermediate volume (91) and the condenser (5), and one valve, called the hot valve (93), located between the intermediate volume (91) and the heat exchanger (11), and in that the condenser (5), the airlock (9), and the heat exchanger (11) form a gravity flow path (G) towards the exchanger (11).

5. Generator set according to any one of the preceding claims, characterized in that it comprises a storage (2) of combustible biomass (20) in the form of particles, preferably in form of pellets, and in that the boiler (1) is a biomass boiler (1) and comprises a furnace (12) supplied with combustible biomass from the biomass storage (2) via a conveyor (21), preferably a worm screw.

6. Generator set according to the preceding claim, characterized in that it comprises an automaton controlling an air supply (13) and a supply of combustible biomass to the biomass boiler (1) according to a setpoint.

7. Generator set according to any one of the preceding claims, characterized in that it comprises an electrical buffer accumulator (7) associated with the generator(s) (6).

8. Method for producing electricity from renewable energy in a generator set, comprising: - a step of producing high-pressure steam (101) from liquid water (100) in a renewable energy boiler (1); - a step of transforming the high-pressure steam (10) into a first mechanical movement by a steam engine (3); - a step of generating electricity at least from the first mechanical movement resulting from the first transformation step; characterized in that it also comprises: - a complementary step of transforming a portion of the calories contained in low-pressure steam (103) resulting from the transformation step, into a second mechanical movement, by a Stirling engine (4), and in that during the electricity generation step, electricity is also generated from the second mechanical movement.

9. Method according to the preceding claim, characterized in that it comprises, concomitantly with the complementary transformation step, a step of condensation of the low-pressure water vapor (103) resulting from the transformation step.

10. Method according to the preceding claim, characterized in that the liquid water (100) resulting from the condensation step is reused for the step of producing high-pressure water vapor (101).

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