A computer model was developed to simulate the performance of an integrated 14 solar thermal driven direct contact membrane distillation (DCMD) system for seawater 15 desalination using recorded weather data. The results highlight the importance of simulating the 16 DCMD process together with the energy source. Indeed, when considered in isolation from the 17 thermal energy source, increasing water cross flow velocities in the feed and distillate channels 18 results in an increase in water flux and thermal efficiency of the DCMD module. By contrast, 19 when coupling the DCMD module with the solar thermal collector, increasing water cross flow 20 velocities reduces both the process water flux and thermal efficiency. This is because of the 21 limited supply of solar thermal at any given time, and hence the feed temperature decreases when 22conditions. This is equivalent to a daily distillate production rate of 19.7 kg per m 2 of membrane 30 or 6.3 kg per m 2 of solar thermal collector. 31Keywords: membrane distillation (MD); seawater desalination; solar thermal energy; 32 simulation; process optimisation. 33 3 Introduction 34Membrane distillation (MD) has significant potential for small-scale solar thermal seawater 35 desalination in remote coastal areas. In the MD process, a microporous hydrophobic membrane is 36 used to facilitate the transport of water vapour while retaining liquid water and hence all non-37 volatile substances and dissolved salts; therefore, ultrapure water can be obtained from seawater 38 MD desalination [1, 2]. Unlike pressure-driven membrane desalination processes such as reverse 39 osmosis (RO), MD utilises a vapour pressure gradient induced by a temperature difference across 40 the membrane as the driving force for water transfer. Thus, water flux in MD is not affected by 41 the feed water osmotic pressure [3, 4]. 42 MD is arguably the most suitable platform for small-scale and off-the-grid seawater 43 desalination applications [5][6][7][8][9]. MD is less susceptible to membrane fouling than RO given the 44 absence of a high hydraulic pressure and the discontinuity of the liquid phase across the 45 membrane. As a result, MD can be operated without feed water pre-treatment, making it an ideal 46 process for small and stand-alone seawater desalination applications. Furthermore, MD systems 47

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This paper presents a model-based optimal control strategy for ground source heat pump systems with integrated solar photovoltaic thermal collectors (GSHP-PVT). The control strategy was formulated using simplified adaptive models and a genetic algorithm (GA) to identify energy efficient control settings for GSHP-PVT systems. The simplified adaptive models were used to predict the system energy performance under various working conditions and control settings, and the model parameters were continuously updated using the recursive least squares (RLS) estimation technique with exponential forgetting. The performances of the adaptive models and the control strategy were evaluated based on a virtual simulation system representing a GSHP-PVT system for residential applications. The performance of the major adaptive models was also validated using the experimental data. The results showed that the simplified adaptive models used were able to provide acceptable energy performance prediction. The optimal control strategy can save energy consumption by 7.8%, 7.1% and 7.5%, and increase electricity generation by 4.4%, 6.2% and 5.1%, during the whole cooling, heating and transition periods considered, respectively, in comparison to a conventional control strategy. The findings obtained from this study could be potentially used to drive the development of advanced control strategies suitable for real-time applications.

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a b s t r a c tThis paper presents a numerical heat transfer model for vertical U-tube Ground Heat Exchangers (GHE). This model is uniquely able to take into to account different initial soil temperatures and physical properties at different depths. The model has been validated based on an experimental case study and has been used to simulate the thermal performance of GHEs. The simulation results show that for a 100-m vertical GHE, the first 70 m of the vertically buried GHE has a higher heat transfer capability than its last 30-m section. In addition, the validated model is used to investigate the optimal depth of vertical GHEs in five case studies ranging from 60 to 100 m length. Among them, the simulation results demonstrate that the GHE with buried depth of 70 m is able to provide the highest heat exchange rate per unit depth (54.1 and 47.0 W/m under heat rejection/extraction mode). It consequently results in shortest total GHE length of 11,388 m and the minimum cost of 1.82 million Yuan. However, a larger area is needed for boreholes and GHEs installation. Therefore, the optimal buried depth of the vertical U-tube GHEs for the studied case is 70 m on the condition of allocation of an abundant area to set up the boreholes.