The topic of present study is a novel design of double-circulation water-flow window which combines the functions of solar thermal collector, indoor cooling/heating terminal and sun shading. Simulation program is developed and used to evaluate the year-round performance. For cooling dominant region, the window is efficient in solar thermal collection while making use of low-grade geothermal energy to provide additional heating/cooling in winter/summer. With flow rate of 0.005 kg/s, the window is capable of collecting 21.25% of total incident solar energy, which can be further enhanced to 28.76% by utilizing colored water with higher solar absorptance. Meanwhile, the window utilizes 174.27 and 64.76 kWh geothermal energy annually for indoor cooling and heating per unit area. The present work introduces a feasible way to model and evaluate the overall performance of an active window, which combines the utilization of both solar energy and geothermal energy in single building envelop. Moreover, the authors emphasized on beneficial indoor heat gain/loss through window which favors the energy saving in air-conditioning system, rather than the window component itself. The numerical model can be inserted into building energy simulation tools and provide assistance in green building design. (C) 2020 Elsevier Ltd. All rights reserved.