A solar‐driven membrane‐based water desalination/purification system

Lack of fresh water has turned into one of the major challenges of the world in the present century. Desalination of brackish or seawater has been proven to be one of the best solutions to cope with this global challenge. Among all the desalination methods, Membrane Distillation (MD) is well known as a cost effective and profitable technology for treating saline water. However, higher energy consumption compared to other separation techniques has been reported as MD’s main drawback. That is why the application of solar energy to provide the thermal energy requirement of MD modules has been the focal point of research in this field in recent years. Despite many studies and efforts that have been conducted to date, solar driven membrane based systems have still many undiscussed aspects. Integrating solar energy and membrane technology is not yet a straightforward matter and has many opportunities for technical and economic improvements. Utilizing new solar technologies, their combination with thermal driven membrane modules, and trying to improve thermal and overall efficiency of this integration can be the bedrock of novel researches. Furthermore, most of the previous studies and research activities have been focused on desalination systems, while the proposed systems have been either inefficient or energy intensive, and other sources for improving water quality such as wastewater is completely under-researched. That is why, this study proposed a novel integrated solar membrane-based desalination and wastewater treatment system taking advantage of technologies such as heat pipes, vacuum tubes, and direct contact membrane distillation (DCMD) modules. A theoretical study was considered to firstly investigate the performance and feasibility of the proposed system and secondly to obtain the optimum physical and operational characteristics of both solar and desalination systems. The theoretical analysis was performed by using appropriate energy and exergy equations which were solved in Matlab software. Heat and mass transfer equations along with energy and mass balance equations were considered in this study. A new multi-step theoretical approach was proposed and developed to model the DCMD unit, while the thermal resistance network method was applied in the simulation of the solar system including vacuum glasses, heat pipes, and manifold. Based on the optimum data obtained from the mathematical models, an experimental rig was designed, manufactured, and tested under different climatic and operational conditions. The system was controlled using a central control unit including a control unit, a National Instrument Data Acquisition (NI-DAQ) system, and a power unit. An application program interface (API) was programmed in the LabVIEW 2014 software to record the data at 10- second intervals. Climatic data including solar radiation, ambient temperature, and wind velocity were collected from the weather station located at Edith Cowan University, Joondalup Campus which is located 23 km north of Perth business district. The comparison of the theoretical and experimental results revealed the capability of the developed model to accurately predict the performance of the proposed system. In addition, the optimum characteristics of the system, including the optimum solar collector’s surface area, feed and permeate streams mass flow rates and temperatures, were determined. The results revealed that the application of this nanofluid as the solar working fluid along with implementing a variable mass flow rate technique significantly improved the overall efficiency of the solar system. Sodium Dodecyl BenzeneSulfonate (SDBS) at 0.1 wt.% was the optimum concentration of SDBS for 0.05 wt.% Al2O3/DI water nanofluid exhibiting the highest stability and thermal conductivity enhancement. The results also showed the high dependency of the DCMD module to the physical (e.g., length) and operational (e.g., feed and permeate mass flow rates) parameters, while its performance was independent of salinity. The highest freshwater production rates in hot and cold seasons were observed to be 3.81 and 2.1 L/m2h, respectively. Moreover, the maximum gained output ratios of the system were around 0.79 and 0.58 in hot and cold seasons, respectively. The results also indicated that the gained output ratio and overall efficiency of the system improved upon application of a cooling unit in the permeate flow loop of the system, indicating the effectiveness of the proposed configuration. In addition, the freshwater production increased up to 37% when the system was equipped with a cooling unit. However, the economic feasibility of implementing the cooling unit needs further investigations. Moreover, the proposed system effectively removed the contaminating metals from wastewater by showing the removal percentage of 96, 89, 96, 100, 100, and 94% for Fe, Mn, Cu, Na, K, and Ca, respectively

Evaluation and improvement of energy flexibility and performance of building heating, ventilation, and air-conditioning systems

The foreseen reduction of available fossil fuels, the continued increase in global energy demand, and the irrefutable evidence of climate change, along with the implementation of a global commitment to achieve a net-zero emissions target, have greatly sharpened commercial interest in using renewable energy resources (RER). However, the high penetration of RER-based stochastic power generation systems has resulted in a significant requirement for increased flexibility on the demand side that can allow buildings to adapt to increasingly dynamic energy supply conditions to support power grid operation and optimization. Failure to adapt may carry serious electrical blackouts and can compromise the safety of the supply side. The building sector accounts for a substantial amount of global energy usage and offers great opportunities for energy flexibility. Building energy flexibility is an important and emerging concept in the modern energy landscape, which can support the sustainable transition of the power sector. Building heating, ventilation, and air-conditioning (HVAC) systems are one of the leading energy consumers in buildings, which can be used as a key flexible source. The HVAC systems with integrated thermal energy storage (TES) can further enhance building energy flexibility. This thesis contributes to the evolving field of demand flexibility and introduces methodologies to evaluate and improve energy flexibility and performance of building HVAC systems

A Review of Photovoltaic Thermal (PVT) technology for residential applications: performance indicators, progress, and opportunities

Solar energy has been one of the accessible and affordable renewable energy technologies for the last few decades. Photovoltaics and solar thermal collectors are mature technologies to harness solar energy. However, the efficiency of photovoltaics decays at increased operating temperatures, and solar thermal collectors suffer from low exergy. Furthermore, along with several financial, structural, technical and socio-cultural barriers, the limited shadow-free space on building rooftops has significantly affected the adoption of solar energy. Thus, Photovoltaic Thermal (PVT) collectors that combine the advantages of photovoltaic cells and solar thermal collector into a single system have been developed. This study gives an extensive review of different PVT systems for residential applications, their performance indicators, progress, limitations and research opportunities. The literature review indicated that PVT systems used air, water, bi-fluids, nanofluids, refrigerants and phase-change material as the cooling medium and are sometimes integrated with heat pumps and seasonal energy storage. The overall efficiency of a PVT system reached up to 81% depending upon the system design and environmental conditions, and there is generally a trade-off between thermal and electrical efficiency. The review also highlights future research prospects in areas such as materials for PVT collector design, long-term reliability experiments, multi-objective design optimisation, techno-exergo-economics and photovoltaic recycling

Thermal management solutions for battery electric buses in cold climates

In many cities around the world, electric buses including battery electric buses have been replacing traditional diesel-powered buses because of their benefit for the urban environment. Cabin thermal management is one of the prominent issues that prevent battery electric buses being widely used in cold climate such as Finland. Current solutions such as heat pumps and fuel burning air heaters could not totally satisfy the needs. The thesis evaluates several innovative thermal management solutions with the objectives of improving the cabin heating performance and driving range in cold conditions. In the thesis, a system-level battery electric bus simulation model was developed using the Siemens AMESim software, based on the electric bus prototype e-Muuli of VTT. The simulation model uses multi-level simulation approach and focuses on the details of thermal simulation; the model includes a detailed cabin thermal model as well as a heating, ventilation and air conditioning (HVAC) system model. The powertrain, cabin, and HVAC simulation models are validated by experiments carried out on e-Muuli. Based on the battery electric bus simulation model, several innovative thermal management solutions are developed, including positive temperature coefficient (PTC) heater, powertrain waste energy harvesting through the chiller (liquid-to-air heat pump), and thermal energy storage using phase change material (PCM). Different configurations are tested in real-world driving cycles in different ambient temperature from -20℃ to 40℃. Some other factors, such as air flow through doors, passenger load, and heat generation from passengers are also considered in the simulation. The simulation results show that low ambient temperatures will result in higher energy consumption and lower driving range. Compared to 20 ℃, the driving range is reduced by 40% while using heat pump in -20 ℃. Using PTC heater with heat pump will improve cabin heating performance but further reduce range. Combining a heat pump with the chiller, PCM, chiller and PCM respectively will improve the driving range by 8%, 23%, 24% in -20 ℃. The simulation results also showed that frequent opening of bus doors will cause a significant difference in energy consumption for cabin heating, which is a factor that previous studies have not considered

Innovative solar energy technologies and control algorithms for enhancing demand-side management in buildings

The present thesis investigates innovative energy technologies and control algorithms for enhancing demand-side management in buildings. The work focuses on an innovative low-temperature solar thermal system for supplying space heating demand of buildings. This technology is used as a case study to explore possible solutions to fulfil the mismatch between energy production and its exploitation in building. This shortcoming represents the primary issue of renewable energy sources. Technologies enhancing the energy storage capacity and active demand-side management or demand-response strategies must be implemented in buildings. For these purposes, it is possible to employ hardware or software solutions. The hardware solutions for thermal demand response of buildings are those technologies that allow the energy loads to be permanently shifted or mitigated. The software solutions for demand response are those that integrate an intelligent supervisory layer in the building automation (or management) systems. The present thesis approaches the problem from both the hardware technologies side and the software solutions side. This approach enables the mutual relationships and interactions between the strategies to be appropriately measured. The thesis can be roughly divided in two parts. The first part of the thesis focuses on an innovative solar thermal system exploiting a novel heat transfer fluid and storage media based on micro-encapsulated Phase Change Material slurry. This material leads the system to enhance latent heat exchange processes and increasing the overall performance. The features of Phase Change Material slurry are investigated experimentally and theoretically. A full-scale prototype of this innovative solar system enhancing latent heat exchange is conceived, designed and realised. An experimental campaign on the prototype is used to calibrate and validate a numerical model of the solar thermal system. This model is developed in this thesis to define the thermo-energetic behaviour of the technology. It consists of two mathematical sub-models able to describe the power/energy balances of the flat-plate solar thermal collector and the thermal energy storage unit respectively. In closed-loop configuration, all the Key Performance Indicators used to assess the reliability of the model indicate an excellent comparison between the system monitored outputs and simulation results. Simulation are performed both varying parametrically the boundary condition and investigating the long-term system performance in different climatic locations. Compared to a traditional water-based system used as a reference baseline, the simulation results show that the innovative system could improve the production of useful heat up to 7 % throughout the year and 19 % during the heating season. Once the hardware technology has been defined, the implementation of an innovative control method is necessary to enhance the operational efficiency of the system. This is the primary focus of the second part of the thesis. A specific solution is considered particularly promising for this purpose: the adoption of Model Predictive Control (MPC) formulations for improving the system thermal and energy management. Firstly, this thesis provides a robust and complete framework of the steps required to define an MPC problem for building processes regulation correctly. This goal is reached employing an extended review of the scientific literature and practical application concerning MPC application for building management. Secondly, an MPC algorithm is formulated to regulate the full-scale solar thermal prototype. A testbed virtual environment is developed to perform closed-loop simulations. The existing rule-based control logic is employed as the reference baseline. Compared to the baseline, the MPC algorithm produces energy savings up to 19.2 % with lower unmet energy demand

IEA ECES Annex 31 Final Report - Energy Storage with Energy Efficient Buildings and Districts: Optimization and Automation

At present, the energy requirements in buildings are majorly met from non-renewable sources where the contribution of renewable sources is still in its initial stage. Meeting the peak energy demand by non-renewable energy sources is highly expensive for the utility companies and it critically influences the environment through GHG emissions. In addition, renewable energy sources are inherently intermittent in nature. Therefore, to make both renewable and nonrenewable energy sources more efficient in building/district applications, they should be integrated with energy storage systems. Nevertheless, determination of the optimal operation and integration of energy storage with buildings/districts are not straightforward. The real strength of integrating energy storage technologies with buildings/districts is stalled by the high computational demand (or even lack of) tools and optimization techniques. Annex 31 aims to resolve this gap by critically addressing the challenges in integrating energy storage systems in buildings/districts from the perspective of design, development of simplified modeling tools and optimization techniques

Energy Storage for Water Desalination Systems Based on Renewable Energy Resources

Recently, water desalination (WD) has been required for the supply of drinking water in a number of countries. Various technologies of WD utilize considerable thermal and/or electrical energies for removing undesirable salts. Desalination systems now rely on renewable energy resources (RERs) such as geothermal, solar, tidal, wind power, etc. The intermittent nature and changeable intensity constrain the wide applications of renewable energy, so the combination of energy storage systems (ESSs) with WD in many locations has been introduced. Thermal energy storage (TES) needs a convenient medium for storing and hence reuses energy. The present work provides a good background on the methods and technologies of WD. Furthermore, the concepts of both thermal and electrical energy storage are presented. In addition, a detailed review of employing ESSs in various WD processes driven by RERs is presented. The integration of energy storage with water desalination systems (WDSs) based on renewable energy has a much better capability, economically and environmentally, compared with conventional desalination systems. The ESSs are required to guarantee a constant supply of fresh water over the day

Low-Temperature Technologies and Applications

This book on low-temperature technology is a notable collection of different aspects of the technology and its application in varieties of research and practical engineering fields. It contains, sterilization and preservation techniques and their engineering and scientific characteristics. Ultra-low temperature refrigeration, the refrigerants, applications, and economic aspects are highlighted in this issue. The readers will find the low temperature, and vacuum systems for industrial applications. This book has given attention to global energy resources, conservation of energy, and alternative sources of energy for the application of low-temperature technologies