CN-122026334-A - Method for predicting generated energy of photo-thermal power generation system

CN122026334ACN 122026334 ACN122026334 ACN 122026334ACN-122026334-A

Abstract

The invention relates to the technical field of new energy power generation and intelligent prediction, and discloses a power generation amount prediction method of a photo-thermal power generation system. The method comprises the steps of obtaining historical operation data, real-time weather and numerical weather forecast data, constructing a three-dimensional unsteady heat conduction-convection coupling control equation set of the heat storage tank, introducing a phase change latent heat item, solving a temperature field and a phase change interface by adopting a finite volume method by taking measured fused salt inlet and outlet parameters as boundary conditions, combining heliostat field focusing energy input, predicting available heat energy in the future in a forward iteration mode, and converting the heat energy into an electric energy output sequence according to a turbine thermodynamic efficiency curve. According to the invention, through multi-physical field coupling modeling, the prediction accuracy of the generated energy is remarkably improved, the average absolute percentage error of 4-hour prediction is lower than 3%, and the prediction accuracy is improved by more than 40% compared with the traditional method.

Inventors

GAO BO
WANG YANZHE
HONG KUNPENG
JIANG XIANGJU

Assignees

兰州交通大学

Dates

Publication Date: 20260512
Application Date: 20260410

Claims (10)

1. A method for predicting power generation capacity of a photo-thermal power generation system, comprising: Acquiring historical operation data, real-time meteorological observation data and numerical weather forecast data of a target photo-thermal power station within 24 hours in future; Extracting molten salt inlet and outlet temperature, flow and liquid level change sequences of the heat storage tank under different heat charging and discharging working conditions based on the historical operation data; Constructing a three-dimensional unsteady heat conduction-convection coupling control equation set in the heat storage tank, wherein the equation set comprises an energy conservation equation, a momentum conservation equation and a mass conservation equation, and introducing a phase change latent heat term to represent the energy absorption and release process of molten salt in a solid-liquid two-phase region; Inputting the molten salt inlet and outlet temperature, flow and liquid level change sequence as boundary conditions into the control equation set, and discretizing and solving the temperature field inside the heat storage tank by adopting a finite volume method to obtain real-time temperature distribution and phase change interface positions of a plurality of temperature area units divided along the height direction; calculating the focusing energy input power of the heliostat field in a future period based on the direct normal irradiance, the ambient temperature, the wind speed and the cloud cover parameters in the numerical weather forecast data; Taking the focusing energy input power as a heat source item, driving the three-dimensional unsteady heat conduction-convection coupling control equation set to perform forward time step iterative solution, and predicting the temperature evolution track and the total amount of available heat energy of each temperature zone unit in a future preset time window; And converting the total amount of available heat energy into a corresponding electric energy output power sequence according to a thermodynamic cycle efficiency curve of the steam turbine generator unit, and generating a final generating capacity prediction result.
2. The method for predicting the power generation capacity of a photo-thermal power generation system according to claim 1, wherein constructing a three-dimensional unsteady-state heat conduction-convection coupling control equation set inside the heat storage tank specifically comprises: Defining a geometric domain of the heat storage tank as an axisymmetric region under a cylindrical coordinate system, wherein the radial coordinate range of the geometric domain is 0 to the radius in the tank body, and the axial coordinate range is from the tank bottom to the tank top; setting physical property parameters of molten salt as a function of temperature, including density, specific heat capacity, heat conductivity coefficient and dynamic viscosity; Introducing a phase change latent heat term into an energy conservation equation, wherein the phase change latent heat term is characterized by adopting an enthalpy-porosity model, and the solid phase fraction is determined by the relation between the local temperature and the molten salt phase change temperature interval; the momentum conservation equation adopts Boussinesq to approximate the buoyancy lift term so as to reflect the natural convection effect; the mass conservation equation assumes that the molten salt is an incompressible fluid and the right side of the continuity equation is 0.
3. The method according to claim 2, characterized in that inputting the molten salt inlet-outlet temperature, flow rate, and liquid level change sequence as boundary conditions to the control equation set specifically includes: Applying a first type of boundary condition at the inlet at the bottom of the heat storage tank, setting the inlet temperature to be equal to the actually measured cold molten salt temperature, and calculating the inlet speed by dividing the actually measured flow by the inlet sectional area; applying a second type boundary condition at the outlet of the top of the heat storage tank, setting the outlet pressure as atmospheric pressure, and determining the outlet temperature by calculating an internal flow field; Applying a third type of boundary condition on the wall surface of the tank, wherein the convective heat transfer coefficient is calculated according to the external environment wind speed and the thermal resistance of the thermal insulation layer of the tank body, and the environment temperature is obtained from real-time meteorological observation data; the level change is achieved by dynamically adjusting the height of the computational domain, updating the free level position per time step based on the net inflow volume.
4. The method for predicting the power generation capacity of a photo-thermal power generation system according to claim 3, wherein the discretizing the temperature field inside the heat storage tank by using the finite volume method specifically comprises: dividing a calculation domain into structured hexahedral grids, setting at least 10 layers of grids in the radial direction, encrypting according to temperature zones in the axial direction, and enabling the size of the grids of the phase change area to be not more than 5 cm; The time step adopts a self-adaptive strategy, the initial value is 10 seconds, and when the temperature change of two adjacent steps exceeds a preset threshold value, the time step is automatically halved; solving the pressure-speed coupling by adopting a SIMPLE algorithm; the energy equation and the momentum equation are iterated by adopting an alternate direction implicit format until the residual error is smaller than 。
5. The method for predicting power generation capacity of a photo-thermal power generation system according to claim 4, wherein calculating the focused energy input power of the heliostat field in the future period of time comprises: calculating the zenith angle and azimuth angle of the sun according to the geographical position, date and time of the power station; combining heliostat field layout parameters and a tracking error model, and determining effective reflection area and pointing deviation of each heliostat; simulating the energy flux distribution of sunlight on the surface of a receiver after being reflected by a heliostat by utilizing a ray tracing method; after the atmospheric attenuation, mirror pollution and optical shielding loss are deducted, the net incident thermal power is obtained; The net incident thermal power is used as a volume heat source item and is uniformly distributed in a computing unit corresponding to the molten salt runner in the receiver.
6. The method for predicting the power generation capacity of a photo-thermal power generation system according to claim 5, wherein predicting the temperature evolution track and the total amount of available heat energy of each temperature zone unit within a future preset time window specifically comprises: taking the three-dimensional temperature field at the current moment as an initial condition, and advancing and solving the control equation set step by step; identifying all temperature zone units with the temperature higher than the minimum steam inlet temperature threshold value of the steam turbine at each prediction time point; integrating the heat energy of the temperature area units, wherein the calculation formula is to sum the products of the volumes of the units multiplied by the density, the specific heat capacity and the difference between the temperature and the reference temperature; The reference temperature is taken as the cold melting salt return tank temperature; The total amount of available heat energy is the integration result.
7. The method for predicting power generation capacity of a photo-thermal power generation system according to claim 6, wherein converting the total amount of available thermal energy into a corresponding electrical energy output power sequence according to a thermodynamic cycle efficiency curve of a turbo-generator set specifically comprises: Thermoelectric conversion efficiency of the turbo generator set under different main steam temperatures, pressures and load rates is calibrated in advance; establishing a mapping relation table between efficiency and available heat energy input rate; inquiring the mapping relation table at each prediction time point according to the total amount of currently available heat energy and the change rate thereof, and interpolating to obtain instantaneous thermoelectric conversion efficiency; the electrical energy output power is equal to the available thermal energy input rate multiplied by the instantaneous thermoelectric conversion efficiency; and carrying out time integration on the electric energy output power in a prediction time window to obtain a total power generation quantity predicted value.
8. The method of claim 1, wherein the historical operating data comprises heat storage system operating parameters recorded every 5 minutes over the past 30 days, the heat storage system operating parameters comprising inlet and outlet temperatures of the hot and cold molten salt tank, main line flow, pump stack start and stop status, and level gauge readings.
9. The method of claim 1, wherein the numerical weather forecast data includes direct normal irradiance, total cloud cover, boundary layer height, and near-ground wind farm data updated at 15 minute intervals within a future 24 hours.
10. The method for predicting power generation capacity of a photo-thermal power generation system according to claim 6, wherein the minimum steam inlet temperature threshold of the steam turbine is 290 ℃ and the cold molten salt return tank temperature is 290 ℃.

Description

Method for predicting generated energy of photo-thermal power generation system Technical Field The invention belongs to the technical field of new energy power generation and intelligent prediction, and particularly relates to a power generation amount prediction method of a photo-thermal power generation system. Background Photo-thermal power generation is used as an important technical path in the field of renewable energy sources, solar energy is converted into heat energy through a condensation heat collection system, and stable output of electric energy is achieved by utilizing a heat storage medium. The method has the core advantages of large-scale energy storage capacity and power grid dispatching friendliness, and is particularly suitable for power systems accessed by high-proportion renewable energy sources. In the technical system, the heat storage system bears key functions of energy buffering and power regulation, and the performance of the heat storage system directly determines the power generation efficiency, the operation stability and the economy of the power station. Currently the mainstream heat storage medium comprises molten salt and solid material, and its heat storage and release process involves complex heat transfer, phase change and ageing behaviour of the material. The prediction of the generated energy of the heat storage system is a precondition for realizing optimal scheduling and energy management of the photo-thermal power station. Accurate prediction relies on fine modeling of the internal thermodynamic state of the heat storage unit, in particular on dynamic evolution rules of temperature distribution, heat loss rate and material circulation durability during charging and discharging. The existing prediction method is mostly based on a simplified heat balance model or an empirical regression formula, and is difficult to describe the multi-physical field coupling characteristic of the heat storage medium under the unsteady state working condition. In the prior art, a heat storage tank is generally regarded as an ideal temperature homogenizing body which is completely mixed, the obvious temperature layering phenomenon caused by natural convection inhibition, uneven inlet flow velocity distribution or phase change interface movement is ignored, meanwhile, the dynamic hysteresis effect and microstructure degradation of a phase change material in repeated melting-solidification circulation are not fully considered in a traditional model, and the estimation of heat capacity attenuation, heat conductivity change and heat stress accumulation is seriously deviated from the actual estimation. In addition, although the data driving method can fit historical operation data, the method lacks physical mechanism constraint, and the generalization capability is insufficient when the method faces extreme weather, equipment aging or operation strategy mutation and other unseen scenes. The defects cause the existing prediction model to have obvious deviation in the aspect of long-period and high-precision power generation capacity prediction, and the existing prediction model is difficult to support the fine requirements of the photo-thermal power station for participating in the power market bidding and auxiliary service scheduling. Therefore, a method for predicting the unbalanced state thermodynamics by combining multiple physical field mechanisms and data intelligence is needed to realize high-fidelity characterization of the dynamic behavior of the heat storage system and accurate look-ahead of the generated energy. Disclosure of Invention The invention provides a method for predicting the generated energy of a photo-thermal power generation system, which aims to solve the problem that the traditional heat storage model is insufficient in the prediction accuracy of the generated energy caused by neglecting internal temperature layering and material phase change hysteresis due to the fact that a heat storage tank is a completely mixed uniform temperature body. According to the method, a dynamic heat storage state model with multiple physical field coupling is constructed, real-time meteorological data, solar irradiation tracks and molten salt flow characteristics are combined, high-resolution modeling is conducted on a three-dimensional temperature field and a phase change interface in a heat storage tank, therefore, heat energy which can be scheduled in a future period is accurately deduced, and finally, a power generation prediction result with high confidence coefficient is generated. According to one aspect of the invention, the invention provides a generating capacity prediction method of a photo-thermal power generation system, which comprises the steps of obtaining historical operation data, real-time meteorological observation data and numerical weather forecast data within 24 hours in future of a target photo-thermal power station, extracting molten salt inlet and outlet tempera