Direct Steam Generation in Solar Thermal Power Systems

Direct steam generation (DSG) in solar thermal power systems refers to the production of saturated or superheated steam directly within the receiver tubes of concentrating collectors, eliminating the need for an intermediate heat transfer fluid. By operating in a two-phase regime, DSG plants can achieve higher thermal efficiencies, reduced capital and operational costs, and simplified heat-storage integration. Typical configurations employ parabolic trough or linear Fresnel collectors arranged in series or dual-loop circuits to manage the pressure and temperature profiles required for stable steam production. The main technical challenges lie in controlling flow instabilities, phase transition dynamics and thermal stresses under variable solar irradiance. Advances in real-time monitoring, computational modelling and adaptive control have progressively addressed these issues, enabling commercial demonstration facilities in Europe, the Middle East and Asia. DSG plants play a growing role in renewable energy portfolios by offering dispatchable solar power, cogeneration for industrial heat and process steam for desalination. Their modularity and scalability make them particularly attractive for arid regions with high solar resource and constrained water supplies, where conventional rankine-cycle solar thermal plants face limitations.

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Direct Steam Generation in Solar Thermal Power Systems publication trend

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Technical terms

Direct Steam Generation (DSG): A technology in which water is converted to steam directly within the solar collector receiver, bypassing an intermediate heat transfer fluid.

Parabolic Trough Collector: A curved reflector that focuses sunlight onto a linear receiver tube, commonly used in DSG systems for its high optical efficiency and mature technology base.

Two-Phase Flow: A flow regime within the receiver tube where liquid water and steam coexist, requiring careful management of pressure, temperature and flow rate to avoid instabilities.

Thermal Storage Integration: The incorporation of heat storage media (e.g. molten salts) to decouple steam production from sunlight availability, enabling dispatchable power output.

Adaptive Control: Control strategies that adjust system parameters in real time to maintain stable steam conditions under fluctuating solar irradiance and operational disturbances.

References

1. Modeling of Solar Field in Direct Steam Generation Parabolic Trough Based on Heat Transfer Mechanism and Artificial Neural Network. IEEE Access (2020).
2. Establishment, Validation, and Application of a Comprehensive Thermal Hydraulic Model for a Parabolic Trough Solar Field. Energies (2019).