Segmented Steam Generator Circuits for Solar Thermal Efficiency
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Solution Overview
Problem
Solar thermal power plants with molten salt heat storage face efficiency issues due to pinch limitations, leading to low steam pressure and potential freezing of molten salt, plugging, and damage to heat exchange components, particularly when reheating steam is avoided to prevent mixing of hot molten salt in the steam generator.
Innovation Solution
A solar thermal power system with a multistage steam turbine and primary and secondary steam generator arrangements that allow for variable pressure steam generation, eliminating the need for mixing hot molten salt and enabling reheating of steam to increase efficiency and prevent wetness issues at the low-pressure turbine exit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If reheat is removed to avoid mixing hot molten salt in the steam generator, then the complexity of the steam generator arrangement is reduced, but the steam pressure must be increased to compensate for efficiency loss, resulting in very high wetness at the low pressure turbine exit
Solution Approach 1:
The steam generator arrangement is segmented into multiple independent circuits (first circuit with first steam generator, second circuit with second steam generator) that operate in parallel. This segmentation allows each circuit to function independently without requiring mixing of hot molten salt, thereby reducing the complexity and reliability issues of a single integrated system while maintaining efficient steam generation.
2Reliability
If feed water temperature is maintained above 240°C to avoid freezing of molten salt, then the reliability of the thermal energy storage fluid is improved, but the steam pressure is limited to below 115 bars due to pinch limitation
Solution Approach 1:
The steam generation system is divided into multiple independent circuits, each with its own steam generator operating at different pressure levels. The first steam generator operates at high pressure (above 115 bars) while the second operates at lower pressure, allowing each circuit to optimize its operating parameters without being constrained by the pinch limitation of a single integrated system.
Solution Approach 2:
The system utilizes different operating parameters for different steam generator circuits. The first steam generator operates at high pressure and temperature conditions optimized for maximum efficiency, while the second steam generator operates at lower pressure conditions. This parameter differentiation allows the system to exceed the traditional 115 bar pressure limit while maintaining reliable molten salt operation through proper temperature control in each circuit.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system achieves higher efficiency and prevents issues like freezing and plugging by generating high-pressure steam and reheating intermediate-pressure steam, maintaining system operability without pinch limitations and reducing wetness problems.
Implementation Method 1
A solar thermal power plant based on Direct Steam Central Receiver (DSCR) includes a large field of heliostats and a solar receiver placed on a tower of substantial height. The heliostats focus direct sunlight on to the solar receiver to produce steam
Implementation Method 2
The present disclosure generally relates to the field of concentrated solar power, and more particularly, to a concentrated solar thermal power plant with molten salt heat storage that utilizes concentrated solar power to store heat energy
Implementation Method 3
The primary steam generator arrangement is utilized to supply a high pressure steam of a desired pressure, produced from the thermal energy storage fluid, to a high pressure turbine inlet of the multistage steam turbine
Implementation Method 4
a multistage steam turbine, and primary and secondary steam generator arrangements that allow for variable pressure steam generation, eliminating the need for mixing hot molten salt and enabling reheating of steam to increase efficiency
Data Source
AI summary
A solar thermal power system includes a solar receiver and a thermal energy storage arrangement including thermal energy storage fluid to be circulated through the solar receiver to store thermal energy. The system includes a multistage steam turbine operable on variable pressure steam generated by primary and secondary arrangements, by utilizing the fluid. The primary arrangement generates and supplies a high pressure steam to a high pressure turbine inlet, and exits from a high pressure turbine outlet. The secondary arrangement having a reheat assembly, to generate an intermediate pressure steam from the fluid, received from the storage arrangement through the reheat assembly. The intermediate pressure steam and released steam from a high pressure turbine outlet are mixed and reheated in the reheat assembly to be supplied to an intermediate pressure turbine inlet.