Back-up Boiler System for Solar Thermal Power Plants
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Solution Overview
Problem
Conventional solar thermal power plants using molten salt technology face efficiency limitations due to the dissociation of heat transfer media at high temperatures and operational constraints related to the availability of solar radiation, leading to suboptimal electricity generation and high capital investment in thermal storage systems.
Innovation Solution
A back-up boiler system with a combustion chamber and convection section, featuring heat exchangers for molten salts and boiler feed water, allows for selective heat transfer using flue gas, enabling continuous operation and temperature control, independent of solar radiation availability, and includes valve and temperature control mechanisms for efficient heat distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional heat transfer media (oil) are used in solar thermal power plants, then the system can operate at lower temperatures with simpler materials, but the overall efficiency is limited to less than 32% due to temperature constraints
Solution Approach 1:
The patent changes the operating temperature parameter from conventional low-temperature oil-based systems to high-temperature molten salt systems (500-1000°C). This parameter change enables higher efficiency electricity generation while using molten salts as the heat transfer medium, resolving the contradiction between material simplicity and efficiency by selecting a different thermal fluid with appropriate high-temperature properties
Solution Approach 2:
The patent employs composite material strategies by using molten salt mixtures (combinations of different salts) as the heat transfer medium, and by implementing a dual-tower storage system with different salt compositions optimized for specific functions. This allows the system to achieve both high-temperature operation and manageable material properties
2Duration of action of moving object
If molten salt storage systems are added to extend operation time, then continuous power generation is enabled, but a substantial part of capital investment is absorbed by the storage system
Solution Approach 1:
The patent makes the molten salt system multi-functional by using molten salts simultaneously as the heat transfer medium in the solar collector and as the storage medium in the thermal storage towers. This eliminates the need for separate storage fluids and reduces system complexity while enabling continuous operation through the dual-tower storage architecture
3Device complexity
If solar thermal power plants operate without back-up systems, then the system structure is simpler, but operation is limited by the occasional absence of solar radiation
Solution Approach 1:
The patent implements preliminary action by using molten salt thermal storage towers that pre-store thermal energy during periods of high solar radiation. This stored energy is then released during periods of low or no solar radiation, ensuring continuous operation without requiring complex back-up generation systems
Solution Approach 2:
The patent achieves continuity of useful action through the dual-tower molten salt storage system, where one tower stores hot salt and the other stores cold salt, enabling continuous heat extraction for power generation regardless of solar radiation availability. This maintains operational reliability while keeping the overall system structure relatively simple
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 back-up boiler system enhances electricity generation efficiency, extends plant operation time, and maintains stable steam and boiler feed water temperatures, allowing for continuous power generation and desalination, even at night or during low solar radiation, thereby improving overall plant efficiency and economics.
Implementation Method 1
a combustion chamber (70) for burning of fuel
Implementation Method 2
at least a first heat exchanger (92) that is operatively coupled to a heat transfer fluid circuit
Implementation Method 3
a convection section (80) in fluid connection with said combustion chamber
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
A back-up boiler system for a solar thermal power plant (201) for transferring solar energy into electricity, said back-up boiler system comprising a combustion chamber (70) and a convection section (80) in fluid connection with said combustion chamber (70), wherein in the convection section (80) at least a first heat exchanger (92) is provided for heating a molten salts mixture of the solar thermal power plant and a second heat exchanger (90) for pre-heating boiler feed water of the solar thermal power plant, wherein the back-up boiler system (25) is configured to allow selection between only providing heat to the first heat exchanger (92), only providing heat to the second heat exchanger (90) and providing heat to both heat exchangers (90, 92), preferably dependent on availability of solar radiation and/or dependent on demand of power generation. The invention also relates to a solar thermal power plant (201) for transferring solar energy into electricity and a method for operating a solar thermal power plant.