Solar Desalination Using Pressurized Single-Phase Fluid Storage
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Solution Overview
Problem
Current thermal desalination systems using concentrated solar power (CSP) face challenges in operating continuously during night due to lack of affordable thermal energy storage, especially for high-salt groundwater desalination which requires thermal energy to overcome membrane fouling and brine disposal issues.
Innovation Solution
The use of single-phase fluid (SPF) as a thermal energy storage medium and heat transfer fluid, which is pressurized and heated to critical and supercritical temperatures, allowing for efficient steam generation and condensate storage during the day for nighttime operation, enabling continuous desalination without phase segregation and reducing investment and maintenance costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If thermal energy storage (TES) is implemented using conventional media, then continuous nighttime operation is enabled, but investment and maintenance costs increase significantly
Solution Approach 1:
The patent changes the physical parameters of the storage medium by using pressurized liquid water at elevated temperatures (above 100°C but below critical point) instead of conventional TES media. This parameter change allows water to remain in liquid phase at storage temperatures, eliminating phase segregation and enabling simpler storage tank design without requiring phase change material containment structures.
Solution Approach 2:
The patent introduces a heat exchanger as an intermediary between the stored hot liquid water and the desalination unit. This intermediary allows thermal energy transfer without direct contact between the storage medium and the desalination process, enabling flexible heat extraction while maintaining system pressure and temperature control.
2Quantity of substance
If multi-phase storage media are used, then high energy density is achieved, but phase segregation occurs causing operational instability
Solution Approach 1:
The patent maintains the storage medium in a single liquid phase by controlling temperature and pressure parameters. The liquid water is heated above 100°C but kept below the critical point (374°C), and stored under pressure to prevent boiling. This parameter control ensures homogeneous composition without phase segregation while achieving high energy density through elevated temperature storage.
3Productivity
If conventional thermal desalination is used, then fresh water is produced, but operation must stop during nighttime without TES
Solution Approach 1:
The patent implements preliminary action by storing thermal energy in the form of hot pressurized liquid water during daytime when solar energy is available. This pre-stored thermal energy is then utilized during nighttime to continue desalination operations without interruption, effectively decoupling the desalination process from immediate solar irradiance.
4Productivity
If high-salt groundwater is treated with membrane desalination, then desalination is achieved, but membrane fouling occurs reducing efficiency
Solution Approach 1:
The patent replaces the membrane-based mechanical separation system with a thermal separation system. Instead of using membranes that are susceptible to fouling from organic and inorganic components, the invention uses heat-driven evaporation and condensation processes that are not affected by the presence of foulants in high-salt groundwater.
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
This solution allows for efficient and cost-effective continuous operation of thermal desalination units at night, achieving higher performance ratios and reducing the capacity and cost of CSP and storage systems, while providing fresh water from high-salt groundwater, especially in remote arid areas.
Implementation Method 1
The use of single-phase fluid (SPF) as a thermal energy storage medium and heat transfer fluid, which is pressurized and heated to critical and supercritical temperatures
Implementation Method 2
The water in single-phase in the pressurized liquid water region and in the supercritical water region is used as a TES medium and HTF
Implementation Method 3
The SPF is used as a TES medium and HTF for the solar desalination system by generating both steam for utilization of latent heat
Implementation Method 4
generating both steam for utilization of latent heat and steam condensate for sensible heat
Implementation Method 5
The SPF is used as a TES medium and HTF for the solar desalination system by generating both steam for utilization of latent heat and steam condensate for sensible heat
Data Source
AI summary
A single-phase fluid (SPF) storage is introduced for desalination of high-salt water using thermal energy from a concentrated solar power (CSP) unit. The SPF having a specific volumetric enthalpy higher than that of water at critical point in the operating ranges from 20 to 300 bar in pressure and 190 to 400 C in temperature is used as a new type of thermal energy storage (TES) medium and heat transfer fluid (HTF). It produces wet steam of a quality required by the desalination unit generating both steam for utilization of latent heat and condensate for sensible heat when its pressure is reduced to lower operating pressures. With a MED-TVC unit by using the steam as motive steam, the capacity of the CSP unit and SPF storage can be reduced as much as the energy recycled in the desalination unit.