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• An unsteady model is proposed for osmotic energy conversion. • The variation of salt concentration during actual operation is considered. • The accuracy of model is verified by salinity-gradient power generation experiments. • A parallel encapsulation method is provided to enhance output power density. Converting the salinity-gradient into electricity via ion migration in nanoconfined channels driven by the salt concentration gap between sea and river water is an important renewable energy utilization method. The osmotic energy conversion device is regarded as a power source with constant voltage output in the conventional constant voltage source (V-source) power equivalent circuit model, which is based on a steady state with constant concentration on both sides of the membrane. In this study, an unsteady equivalent capacitor–capacitor/resistor (C-CR) power equivalent circuit model is proposed to consider the salt concentration variation during actual operation. The maximum relative deviation of the calculated short circuit current between the C-CR power equivalent circuit model and the measured experimental data is 7.06%. The maximum relative deviation of the predicted maximum output power density between the C-CR power equivalent circuit model and the measured experimental data is less than 14.22%, while the corresponding maximum deviation for the V-source power equivalent circuit model has an error of 38.14%. A parallel encapsulation method by embedding graphene oxide membranes (GOMs) into polydimethylsiloxane (PDMS) is provided to offer an extended accessible area for ion transport to enhance the ion flux and output power density. This method reveals a linearly increased output power with the number of GOMs, which provides convenience for increasing output power. This work provides an effective way to design integrated osmotic energy conversion devices, which promotes the development of salinity-gradient-driven energy conversion systems. [ABSTRACT FROM AUTHOR]

• A dynamic simulation model of a novel wind-to-heat system is built. • The energy conversion from wind to heat is explained by the model. • The model is verified within 10% average errors with the experimental results. • The heat production capacity of the system in one heating season is obtained. • For the first time match the wind-to-heat system heat production and the heat load. As a clean heating technology, the wind-to-heat system with shorter energy conversion and higher efficiency is proposed. The simulation model of the wind-to-heat system is built by combined wind turbine, drive chain and heat pump with the control strategy. The compressor torque characteristics are the key to matching the wind turbine and the compressor. The three-zone model is used to simulate the condenser and the evaporator. Compared with theoretical calculation research, the dynamic performance and the accuracy of the system can be studied and improved. The control strategy specifies the control objectives of the system at different wind speeds. Comparing the simulated heating capacity, shaft power and revolving speed with the experimental values at different wind speeds, the simulation results are verified with average errors within 10%. Considering the application scope of the system on the user side, the match between the heat production and heat load is carried out. The wind energy utilization hours, the loss of load probability and the average electric heat production are introduced as evaluation indexes. Under the conditions with or without energy storage, to ensure the maximum utilization of wind energy in the wind-to-heat system, different optimal number of villas are obtained. It can provide a reference for matching the system design and the user needs. [ABSTRACT FROM AUTHOR]