Concentrating solar thermal desalination: Performance limitation analysis and possible pathways for improvement

Highlights: • Cascading heating strategies are important for solar thermal desalination systems. • High-temperature systems may enable higher water production rate. • Heat exchange area and heat transfer coefficient are important for design. • Solar thermal desalination performance is susceptible to low recovery ratios. Solar thermal desalination is a viable approach for sustainable water production. Current thermal desalination technologies suffer from high specific energy consumption and energy mismatch. Concentrating solar collectors operate with high temperature energy and desalination systems operate with low temperature energy which leads to large exergy destruction. Herein, a thermodynamic model of an ideal concentrating solar-distillation process is developed to evaluate system integration and performance limitations (specific water production). Three different heating architectures are examined to understand how solar collector absorber temperature, concentration ratio, and recovery ratio impact system performance. A reversible solar distillation system operating with a concentration ratio of 10 at the optimal absorber temperature of 507 K can achieve a maximum specific water production of $~$166.3 gs⁻¹m⁻² as the recovery ratio (rr) approaches zero. An endo-reversible heat engine model was formulated to consider system irreversibilities. Systems with irreversibilities (R = 0.001 K/kW or 0.005 K/kW) experience a decrease in the water production rate to 8.8 g s⁻¹m⁻² (rr = 51.4%) and 1.9 g s⁻¹m⁻² (rr = 65.2%). For efficient integration of solar collectors with thermal desalination systems, it is critical to adopt appropriate heating configurations and control absorber temperatures, system recovery ratio, and system irreversibilities.