Kan Weimin

Study on the mathematical model and primary frequency regulation characteristics of combined cycle plants

Combined cycle plants have significant impact on the primary frequency regulation stability of a power system. Because of the complexity and non-linearity of combined cycle plants, the modeling is very challenging. It is important to propose a simplified mathematical model for studying primary frequency regulation characteristics of combined cycle plants. In this paper, an appropriately simplified model is proposed based on classical model of a combined cycle plant. This model is suitable for power system analysis on primary frequency regulation stability. Parameters of the proposed model are identified by a method based on genetic algorithm. With all parameters identified, this dynamic model is applied to simulate a real 400MW combined cycle plant. The simulated results and the measured responses are in favorable agreements, indicating the feasibility of the proposed model. The results may be helpful for further studies on the primary frequency regulation of combined cycle plants.

Capillary-driven seawater desalination

We demonstrate a novel capillary-driven seawater desalination system. The essence of the system is an open loop heat pipe. Seawater is evaporated at the outer surface of the wick structure of the “heat pipe”, where a capillary pressure is developed as the driving force to ensure the continuous operation of the system. The produced vapor is then condensed into fresh water in a condenser. The difference from a regular heat pipe is that the evaporator is not fed back with the condensed water, but with seawater instead. With a heat source at 40℃, the fresh water production rate is achieved up to 91.8 g/h for an effective evaporation area of 50.24 cm2. The TDS (total dissolvable solids) of the produced water is less than 30 mg/L, far beyond the standard for drinking water. For wide operation temperature adaptability, particularly, at low temperatures, the presented desalination technique may have big potentials for the use of low-cost and low-grade heat energy to produce fresh water.