New energy coupled combined heat and power system

Abstract

The application discloses a new energy coupling type combined heat and power system and belongs to the technical field of distributed energy and combined heat and power. The system comprises a renewable energy power generation unit, a solar light and heat unit, a high-temperature heat storage unit, a biomass heat source unit, a steam generation and mixing device, a back pressure steam turbine generator unit, an electric heating and heat storage unit and a control unit. Solar heat collection heat is directly supplied to a steam generator through heat conduction oil or stored in a double-tank molten salt heat storage system, heat storage and heat release can supplement insufficient biomass steam, and the excess wind and light power drives a heat pump to heat and store heat, indirectly participates in steam circulation and realizes deep coupling of electricity-heat-steam cross media. The control unit adopts a hierarchical model predictive control to globally coordinate. The application greatly reduces the renewable energy power abandonment rate, guarantees continuous and stable operation of a steam turbine, flexibly adjusts a heat and power ratio in a range of 0.3-1.5 and significantly improves comprehensive energy utilization efficiency.

Description

Technical Field

[0001] This invention relates to the field of distributed energy and combined heat and power (CHP) technology, specifically to a new energy coupled CHP power system. Background Technology

[0002] Currently, the mainstream solutions for combined heat and power (CHP) systems are gas turbines or gas-fired internal combustion engines for combined cooling, heating and power (CCHP) and coal-fired back-pressure units, which are highly dependent on fossil fuels. In order to increase the proportion of renewable energy, a variety of new energy coupling schemes have been proposed, but there are still obvious defects in practical applications: (1) Insufficient coupling between renewable electricity and heat production, resulting in a high curtailment rate. The existing "wind and solar + electric boiler / thermal storage" scheme only converts curtailed electricity into low-grade heat, resulting in large losses and failing to solve the problem of long-term continuous heating; simple battery storage is costly and has limited capacity, leading to a curtailment rate of 20% to 40%. (2) Poor stability of solar thermal utilization and high cost of thermal storage. Independent solar thermal power plants need to be equipped with large-capacity thermal storage to maintain the continuous operation of the turbine, resulting in a sharp increase in initial investment. Even with thermal storage, continuous cloudy days will still lead to shutdown or reliance on fossil fuel backup boilers, resulting in low system utilization and frequent turbine start-ups and shutdowns, which reduce economic efficiency and lifespan. (3) Inflexible regulation of biomass direct combustion CHP, resulting in low overall efficiency. Biomass power plants are constrained by fuel supply and cannot flexibly adjust the heat-to-power ratio to respond to real-time fluctuations in wind and solar power. Moreover, the energy conversion efficiency of steam generated by biomass combustion alone is low, and the waste heat loss of flue gas is large. (4) Lack of multi-timescale thermo-electric decoupling and coordinated control. The subsystems of the existing coupled system often operate independently, without comprehensive modeling and coordinated scheduling of thermal storage, electric heating, biomass combustion, and the thermal inertia of the steam turbine. The equipment utilization rate is low and the energy supply cost is high. Summary of the Invention

[0003] The technical problem to be solved by this invention is to provide a new energy coupled cogeneration power system that can efficiently absorb wind and solar power curtailment, ensure continuous and stable operation of steam turbines, flexibly adjust the heat-to-power ratio, and has high overall energy utilization efficiency.

[0004] To solve the above-mentioned technical problems, the technical solution provided by the present invention is: a new energy coupled cogeneration power system, comprising:

[0005] A renewable energy power generation unit includes a wind turbine generator and a photovoltaic array, wherein the output terminals of the wind turbine generator and the photovoltaic array are connected to an AC bus via a converter;

[0006] A solar thermal unit includes a parabolic trough collector array, wherein heat transfer oil is circulated inside the collector array, and the outlet of the heat transfer oil is connected to an oil-salt heat exchanger and an oil-steam heat exchanger.

[0007] The high-temperature thermal storage unit includes a high-temperature molten salt tank, a low-temperature molten salt tank, a molten salt pump, and the oil-salt heat exchanger, forming a dual-tank thermal storage circuit;

[0008] The biomass heat source unit includes a biomass gasifier, a gasification fuel purification device, and a gas-fired steam boiler. The gas-fired steam boiler has a superheater, an evaporator, and an economizer arranged sequentially at its tail end.

[0009] The steam generation and mixing device includes a saturated steam passage generated by the oil-steam heat exchanger and a superheated steam passage generated by the biomass gas boiler. The two passages converge into a steam mixing header, and the mixed steam is sent to the steam turbine.

[0010] The heat-power conversion and heating unit includes a back-pressure steam turbine generator set, the exhaust port of which is connected to a shell-and-tube heat exchanger, and the secondary side of which is connected to a heating network.

[0011] The electric heating and heat storage unit includes at least one electric compression heat pump and a hot water storage tank. The heat pump absorbs ambient heat or waste heat, and the hot water generated is fed into the heating network or stored in the hot water storage tank. It can also be selectively used to preheat the feedwater of the steam generator.

[0012] The control unit collects meteorological data, load data, and equipment status data, runs a model predictive control algorithm, and dynamically adjusts the flow rate of heat transfer oil, the speed of molten salt pump, the supply of biomass fuel, the power of heat pump, and the charging and discharging commands of the storage battery.

[0013] The heat from the solar thermal unit is directly supplied to the steam generator via the heat transfer oil, or stored in the high-temperature thermal storage unit via the oil-salt heat exchanger. When the high-temperature thermal storage unit releases heat, it heats the feed water to generate steam to supplement the insufficient steam from the biomass heat source unit. The excess electricity from the renewable energy power generation unit drives the heat pump to generate heat, which enters the hot water storage tank or the feed water system and indirectly participates in the steam cycle, realizing cross-media coupling of electricity, heat, and steam.

[0014] As an improvement, the renewable energy generation unit also includes a battery energy storage device for responding to power curtailment absorption and short-term power smoothing.

[0015] As an improvement, the molten salt in the high-temperature thermal storage unit is solar salt, which is composed of 60% sodium nitrate and 40% potassium nitrate. The operating temperature of the high-temperature molten salt tank is 380°C, and the operating temperature of the low-temperature molten salt tank is 290°C.

[0016] As an improvement, the biomass raw material in the biomass heat source unit is wood chips or straw briquettes, and the moisture content of the biomass raw material does not exceed 25%; the gas-fired steam boiler adopts a dual-pressure steam drum natural circulation structure, with a designed steam production capacity of 12t / h and main steam parameters of 3.82MPa and 400℃.

[0017] As an improvement, in the steam generation and mixing device, the oil-steam heat exchanger is a shell-and-tube heat exchanger, and the heat transfer oil flows through the tube side to heat the boiler water on the shell side to generate saturated steam; the flue gas from the biomass gas boiler sequentially washes over the superheater tube bundle and the evaporator tube bundle, and the generated saturated steam is superheated to 400°C by the superheater; the saturated steam generated by the solar thermal unit is superheated by the biomass gas boiler and then mixed with the superheated steam generated by the biomass gas boiler in the steam mixing header.

[0018] As an improvement, the electric heating and heat storage unit also includes an electric boiler, which is an electrode boiler used to generate steam during peak periods of power curtailment.

[0019] As an improvement, the control unit adopts a hierarchical model predictive control structure, including an upper optimization layer and a lower real-time adjustment layer. The upper optimization layer optimizes the thermal storage charging and discharging plan and the biomass fuel supply plan based on weather forecasts and load predictions with a 6-hour cycle. The lower real-time adjustment layer adjusts the start-up and shutdown of the heat pump and the charging and discharging of the battery based on real-time power fluctuations with a 5-minute cycle.

[0020] As an improvement, the back-pressure steam turbine generator set has an inlet steam pressure of 3.5 MPa, an inlet steam temperature of 395°C, an exhaust steam pressure of 0.6 MPa, and a rated power generation of 2.0 MW; the shell-and-tube heat exchanger provides 0.6 MPa saturated steam to the outside.

[0021] As an improvement, the electric compression heat pump is an air source heat pump with a heating capacity of 3×400kW, a rated performance coefficient of 3.2, and an outlet water temperature of up to 80℃.

[0022] As an improvement, the system allows for flexible adjustment of the heat-to-electricity ratio within the range of 0.3 to 1.5 by adjusting the heat release rate of the high-temperature thermal storage unit, the combustion rate of the biomass heat source unit, and the power of the heat pump.

[0023] The advantages of this invention compared to the prior art are:

[0024] By converting abandoned electricity into adjustable hot water and integrating it into the heating network or storing heat through electric heat pumps, and combined with short-term damping by batteries, the abandoned electricity rate has been reduced from about 28% in conventional systems to less than 5%, achieving low-cost, long-term energy storage substitution.

[0025] Molten salt thermal energy storage and biomass gasification furnace together form a stable heat source. Even if there is no sunlight for two consecutive days, the turbine can still be maintained to run continuously at a load of more than 65%, avoiding start-up and shutdown. The annual average equipment utilization rate has increased from 30% of solar thermal energy alone to more than 75%, reducing the dependence on a single large-capacity thermal energy storage.

[0026] The system's overall energy utilization efficiency can reach over 87%, which is about 15 percentage points higher than that of traditional biomass direct combustion cogeneration. At the same time, the heat-to-power ratio can be flexibly adjusted within the range of 0.3 to 1.5, enabling it to respond to grid peak shaving and heat load fluctuations.

[0027] The hierarchical model predictive control takes into account the turbine's thermal inertia, thermal storage capacity, and electricity price signals, optimizing the joint operation of the electric heat pump and thermal storage. The average annual utilization rate of the equipment can be increased to 82%, and the energy supply cost is significantly reduced. Attached Figure Description

[0028] Figure 1 This is a framework diagram of the new energy coupled cogeneration power system of the present invention. Detailed Implementation

[0029] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention. Example

[0030] This embodiment was constructed in an industrial park in northern China, and the system structure is as follows: Figure 1 As shown in the figure, the park's heating load is mainly 0.6MPa, 160℃ process steam, with an average consumption of 8t / h; the average power supply load is 2.0MW.

[0031] The renewable energy generation unit comprises two 2MW permanent magnet direct-drive wind turbine generators and a 1.5MWp fixed-tilt photovoltaic array, with their outputs connected to the AC bus via a converter. The unit also includes a 2MW / 2MWh lithium iron phosphate battery energy storage system for responding to curtailment and short-term power smoothing.

[0032] The solar thermal unit employs a parabolic trough collector array with a total open area of ​​approximately 10,000 m², consisting of six loops. It internally circulates biphenyl-diphenyl ether heat transfer oil, operating within a temperature range of 290–390°C. The heat transfer oil outlets are connected to an oil-salt heat exchanger and an oil-steam heat exchanger, respectively.

[0033] The high-temperature thermal storage unit is a dual-tank molten salt thermal storage system, using solar salt (60% NaNO3 + 40% KNO3) as the storage medium. The high-temperature molten salt tank is maintained at 380℃, and the low-temperature molten salt tank is maintained at 290℃, with a thermal storage capacity of 12 MWh. Heat transfer oil charges the thermal storage system through an oil-salt heat exchanger, and during heat release, the molten salt heats the feedwater through the heat exchanger to generate steam.

[0034] The biomass heat source unit includes a fixed-bed gasifier, a purification unit, and a gas-fired steam boiler. The raw material is wood chips or straw briquettes with a moisture content not exceeding 25%, and a daily consumption of approximately 30 tons. The calorific value of the gasified fuel is 5.0 MJ / Nm³. 3 The gas is burned in the gas-fired boiler to produce flue gas at 850℃. The boiler has a dual-pressure steam drum and natural circulation structure, with a designed steam production capacity of 12t / h and main steam parameters of 3.82MPa and 400℃. The superheater, evaporator, and economizer are arranged sequentially at the tail end.

[0035] In the steam generation and mixing unit, the oil-steam heat exchanger is a shell-and-tube type. Heat transfer oil flows through the tube side to heat the boiler water on the shell side, generating saturated steam. This saturated steam, along with the saturated steam generated by the biomass gas boiler evaporator, enters the boiler's superheater section and is superheated to 400°C. The superheated steam from both sources converges in the steam mixing header, where it mixes to form qualified steam with parameters of 3.5 MPa and 395°C, which is then fed into the back-pressure turbine generator set. The turbine exhaust pressure is 0.6 MPa, with a rated power output of 2.0 MW. The exhaust steam enters a shell-and-tube heat exchanger, where it condenses and releases heat to provide 0.6 MPa saturated steam. The condensate is recycled.

[0036] The electric heating and heat storage unit includes three air-source heat pumps with a heating capacity of 400kW each, a rated COP of 3.2, and an outlet water temperature of up to 80℃. The heat pumps absorb ambient heat and use excess renewable electricity to produce hot water, which is then directly connected to the heating network or stored in a 500m³ reservoir. 3 The hot water storage tank can also be used as feedwater for the preheating steam generator. The unit is also equipped with an 800kW electrode-type electric boiler, which is only started to produce supplementary steam during peak periods of power curtailment.

[0037] The control unit employs hierarchical model predictive control (MPC). The upper optimization layer, with a 6-hour cycle, continuously optimizes the charging and discharging plans of the high-temperature thermal storage unit and the biomass fuel supply plan based on weather forecasts and heat and electricity load predictions. The lower real-time adjustment layer, with a 5-minute cycle, adjusts the start-up and shutdown of the air source heat pump, the charging and discharging of the battery, and the speed of the molten salt pump based on real-time power fluctuations.

[0038] During operation, solar thermal energy can be directly supplied to generate steam or stored in a high-temperature thermal storage unit via an oil-salt heat exchanger. When sunlight is insufficient, molten salt releases heat to heat the feedwater and generate steam, supplementing the insufficient steam from the biomass side. Excess electricity from wind and solar power drives a heat pump to generate heat, which is stored in a hot water storage tank or feedwater system, indirectly participating in the steam cycle, thus achieving deep coupling of electricity, heat, and steam across media. By comprehensively adjusting the molten salt heat release rate, biomass combustion rate, and heat pump power, the system can flexibly adjust the heat-to-power ratio within the range of 0.3 to 1.5 to meet different energy supply needs.

[0039] Actual operation has verified that the system's renewable energy supply accounts for more than 78%, the annual comprehensive energy utilization efficiency reaches 87%, the curtailment rate is less than 5%, and the annual utilization hours of the steam turbine are more than double those of the independent solar thermal system. All indicators have met expectations.

[0040] The present invention and its embodiments have been described above. This description is not restrictive, and the accompanying drawings are only one embodiment of the present invention; the actual structure is not limited thereto. In conclusion, if those skilled in the art are inspired by this description and design similar structures and embodiments without departing from the spirit of the invention, such designs should fall within the protection scope of the present invention.

Claims

1. A new energy coupled cogeneration power system, characterized in that, include: A renewable energy power generation unit includes a wind turbine generator and a photovoltaic array, wherein the output terminals of the wind turbine generator and the photovoltaic array are connected to an AC bus via a converter; A solar thermal unit includes a parabolic trough collector array, wherein heat transfer oil is circulated inside the collector array, and the outlet of the heat transfer oil is connected to an oil-salt heat exchanger and an oil-steam heat exchanger. The high-temperature thermal storage unit includes a high-temperature molten salt tank, a low-temperature molten salt tank, a molten salt pump, and the oil-salt heat exchanger, forming a dual-tank thermal storage circuit; The biomass heat source unit includes a biomass gasifier, a gasification fuel purification device, and a gas-fired steam boiler. The gas-fired steam boiler has a superheater, an evaporator, and an economizer arranged sequentially at its tail end. The steam generation and mixing device includes a saturated steam passage generated by the oil-steam heat exchanger and a superheated steam passage generated by the biomass gas boiler. The two passages converge into a steam mixing header, and the mixed steam is sent to the steam turbine. The heat-power conversion and heating unit includes a back-pressure steam turbine generator set, the exhaust port of which is connected to a shell-and-tube heat exchanger, and the secondary side of which is connected to a heating network. The electric heating and heat storage unit includes at least one electric compression heat pump and a hot water storage tank. The heat pump absorbs ambient heat or waste heat, and the hot water generated is fed into the heating network or stored in the hot water storage tank. It can also be selectively used to preheat the feedwater of the steam generator. The control unit collects meteorological data, load data, and equipment status data, runs a model predictive control algorithm, and dynamically adjusts the flow rate of heat transfer oil, the speed of molten salt pump, the supply of biomass fuel, the power of heat pump, and the charging and discharging commands of the storage battery. The heat from the solar thermal unit is directly supplied to the steam generator via the heat transfer oil, or stored in the high-temperature thermal storage unit via the oil-salt heat exchanger. When the high-temperature thermal storage unit releases heat, it heats the feed water to generate steam to supplement the insufficient steam from the biomass heat source unit. The excess electricity from the renewable energy power generation unit drives the heat pump to generate heat, which enters the hot water storage tank or the feed water system and indirectly participates in the steam cycle, realizing cross-media coupling of electricity, heat, and steam.

2. The new energy coupled cogeneration power system according to claim 1, characterized in that, The renewable energy generation unit also includes a battery energy storage device, which is used to respond to power curtailment absorption and short-term power smoothing.

3. The new energy coupled cogeneration power system according to claim 1, characterized in that, The molten salt in the high-temperature thermal storage unit is solar salt, which is composed of 60% sodium nitrate and 40% potassium nitrate. The operating temperature of the high-temperature molten salt tank is 380°C, and the operating temperature of the low-temperature molten salt tank is 290°C.

4. The new energy coupled cogeneration power system according to claim 1, characterized in that, The biomass raw material in the biomass heat source unit is wood chips or straw briquettes, and the moisture content of the biomass raw material does not exceed 25%; the gas-fired steam boiler adopts a dual-pressure steam drum natural circulation structure, with a designed steam production capacity of 12t / h and main steam parameters of 3.82MPa and 400℃.

5. The new energy coupled cogeneration power system according to claim 1, characterized in that, In the steam generation and mixing device, the oil-steam heat exchanger is a shell-and-tube heat exchanger. The heat transfer oil flows through the tube side and heats the boiler water on the shell side to generate saturated steam. The flue gas from the biomass gas boiler sequentially washes over the superheater tube bundle and the evaporator tube bundle, and the generated saturated steam is superheated to 400°C by the superheater. The saturated steam generated by the solar thermal unit is superheated by the biomass gas boiler and then mixed with the superheated steam generated by the biomass gas boiler in the steam mixing header.

6. The new energy coupled cogeneration power system according to claim 1, characterized in that, The electric heating and heat storage unit also includes an electric boiler, which is an electrode boiler used to generate steam during peak periods of power curtailment.

7. The new energy coupled cogeneration power system according to claim 1, characterized in that, The control unit adopts a hierarchical model predictive control structure, including an upper optimization layer and a lower real-time adjustment layer; the upper optimization layer optimizes the thermal storage charging and discharging plan and the biomass fuel supply plan based on weather forecasts and load predictions with a 6-hour cycle; The lower real-time adjustment layer adjusts the start / stop of the heat pump and the charging / discharging of the battery based on real-time power fluctuations in a 5-minute cycle.

8. The new energy coupled cogeneration power system according to claim 1, characterized in that, The back-pressure steam turbine generator set has an inlet steam pressure of 3.5 MPa, an inlet steam temperature of 395℃, an exhaust steam pressure of 0.6 MPa, and a rated power generation of 2.0 MW; the shell-and-tube heat exchanger provides 0.6 MPa saturated steam to the outside.

9. The new energy coupled cogeneration power system according to claim 1, characterized in that, The electric compression heat pump is an air source heat pump with a heating capacity of 3×400kW, a rated performance coefficient of 3.2, and an outlet water temperature of up to 80℃.

10. The new energy coupled cogeneration power system according to claim 1, characterized in that, The system allows for flexible adjustment of the heat-to-electricity ratio within the range of 0.3 to 1.5 by regulating the heat release rate of the high-temperature thermal storage unit, the combustion rate of the biomass heat source unit, and the power of the heat pump.

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