A novel solar-driven direct contact membrane-based water desalination system

Strategies to improve the thermal performance of heat pipe solar collectors in solar systems: A review

Thermodynamic performance of a hybrid power generation system using biomass gasification and concentrated solar thermal processes

The relevance of the problem of energy and environmental security is increasing every year. Therefore, in the energy sector, the improvement of renewable energy sources is extremely important. The comprehensive development of optimal technological processes that are cost-effective and allow increasing the efficiency of wind-solar installations is an important problem today. The article discusses issues related to the use of renewable energy sources. An energy system has been created that combines wind and solar energy. Its design includes a horizontal axis wind turbine and solar panels. The blades of a wind turbine are made of polyvinyl chloride. The project presents modeling of two new energy supply systems using renewable energy sources: solar and wind. The energy produced by both sources was combined using a charge controller and then transferred to the inverter. The resulting energy was used to provide electricity to residential premises. The prototype demonstrates an evaluation of the effectiveness of a combined solar and wind system to provide essential home comfort needs such as lighting, fans, etc. In addition, the wind turbine is able to operate at lower wind speeds, which increases the overall efficiency of the system. This prototype was tested in combination with photovoltaic panels to verify the power output and overall efficiency of the integrated system. The comparison between the proposed and current systems confirmed many advantages of the proposed configuration. The efficiency of the wind turbine has been improved during its manufacturing process, especially when used in conjunction with photovoltaic panels, significantly increasing overall productivity

Solid Oxide Fuel Cell (SOFC) has attracted huge scientific attentions lately, as it is a promising power production technology that can reduce user’s dependency on electricity-grid. SOFC system can generate electricity by using liquid or gaseous fuels. Small volume and external fuel storage make SOFC technology more compatible, and it can easily be adjusted for different industry power plant scales. Moreover, SOFC operates at high temperature (700 0C), and it cogenerates high-quality heat or steam, which can be used as a heat source within the system. As maximum fuel utilization for SOFC is around 85%, a burner is required for the combustion of unconverted fuels. The burner provides additional heat to the SOFC system, at the same time, it generates more CO2.In order to meet “net zero” emission target for greenhouse gases in the year 2050, it is essential to introduce Carbon Capture and Storage (CCS) technology that can retrieve most of the produced CO2 from emission intensive activities and store it permanently in nature (e.g, sequestration and mineralization), leading to an almost carbon neutral activity. The stored CO2 can also be used in methanation process, to convert it into green methane. By integrating an existing CCS technology with SOFC, and using biofuels as energy source, SOFC system can be considered as a carbon negative technology. The most common and widely used CCS technology is Chemical Absorption (CA). The CA process presents good retrofitting options. However, corrosion and degradation are major issues.The high efficiency of SOFC system is however penalised by the fact that the flue gases contain typically a mix of CO2 and N2, which makes it difficult and expensive to separate/capture the produced CO2. There is a possibility of directly injecting pure oxygen to the burner. For industrial scale, cryogenic distillation is commonly used air separation technology for producing O2. Cryogenic distillation is an energy intensive technology, and it is not suitable for small scale O2 production. In the recent times, other technologies such as Pressure Swing Adsorption (PSA) and membrane have evolved for O2 production from air. The non-cryogenic technologies for air separation are preferred to their lower operating cost and easier integration with other processes. PSA is usually suited for medium-range production capacity, and it can produce O2 with 94 % purity. However, it is still necessary to improve performance by reducing energy consumption. The energy consumption is 3.211 MJ/kg-O2 for PSA to produce oxygen. In the oxygen production process, energy consumption accounts for more than 90% of the operating cost.This study considers integration of a SOFC system with PSA, which consists of a SOFC stack, balance of plant components for SOFC system, PSA bed and auxiliary components for PSA. The PSA produces O2 from air, that is injected to the combustion chamber (or burner). In the integrated system, the energy needed for the PSA directly comes from SOFC system. The right amount of oxygen is used to complete the oxidation of the unconverted fuel from the anodic side of SOFC, and CO2 is separated automatically after water condensation. Figure 1 shows layout of integrated system. The performance of PSA is explored for different materials, different pressure ratio and temperature, to achieve minimum energy consumption. Moreover, heat integration has been studied for SOFC system, the integrated system has waste heat available, especially at the downstream of the burner. In order to valorize the waste heat of the system, a steam cycle has been integrated for producing extra amount of electricity, to improve the overall efficiency of the system. Finally, the performance of integrated system has been optimized for maximization of electrical efficiency and minimization of exergy distraction, via multi-objective optimization.In this study, the net electricity output from SOFC-PSA system is around 9 kW. The SOFC produces 9.8 kW electricity, and about 8% electricity is consumed by the PSA for producing O2 that is required for the combustion of unconverted fuel. The integrated system has an overall efficiency of more than 55%. A steam cycle has been integrated for producing extra amount of electricity, and it produces additional 2.5 kW of electricity. Hence, the overall efficiency of the integrated system reaches above 70% with automatic CO2 separation. Figure 1

Water and energy are two inseparable issues that play an important role in human life. The oceans are massive resources of water, but the main problem is their high salinity. Solar desalination systems have been considered as a suitable solution to solve the problem of water deficit and to overcome the environmental problems caused by the conventional water desalination plants. One of the important points in raising the efficiency of solar water desalination systems is increasing the evaporation rate in a system with specified dimensions. The direction of the spraying of seawater in the chamber is one of the effective parameters in elevating the discharged rate of vapor in solar desalination systems. In this study, the effects of other parameters including injection pressure, nozzle outlet diameter, nozzle type, and relative humidity inside the chamber were investigated in both upward and downward injection directions by a mathematical model. The results of the model indicated variations in the rate of vapor generation in upward and downward directions. Also, the effects of other important parameters were studied including injection pressure (in the range of 1 to 5 bar), outlet diameter of the nozzle (in the range of 0.9 to 1.1 mm), type of nozzle (long cone orifice, drilled steel orifice, and sapphire orifice) and relative humidity (within the range of 20% to 60%). Overall, the results indicated increased vapor production at an injection pressure of 5 bar, nozzle outlet diameter of 0.9 mm, long cone orifice nozzle, a relative humidity of 20%, and upward direction.

A self-sustainable solar desalination system using direct spray technology

Solar desalination system with a focal point concentrator using different nanofluids

Multi-criteria evaluation of a novel micro-trigeneration cycle based on α-type Stirling engine, organic Rankine cycle, and adsorption chiller

The influence of using MWCNT/ZnO-Water hybrid nanofluid on the thermal and electrical performance of a Photovoltaic/Thermal system

An innovative hybrid power generation system involving a structure‐solid oxide fuel cell (SOFC) and a proton‐exchange membrane fuel cell (PEMFC) is established. A high‐temperature SOFC is not only used to produce electricity, but also supplies the reformed gas to a PEMFC to generate extra electricity simultaneously. A steady‐state thermodynamic model of the SOFC‐PEMFC hybrid system is verified based on the mass and energy balance and the electrochemistry theory. A parametric study is carried out to analyze the effects of various parameters on the performance of the hybrid system. The SOFC operating temperature and the steam‐to‐carbon ratio have a positive impact on the power output and overall efficiency of the system. The operating pressure benefits the system power output but not the overall efficiency. An optimum SOFC fuel utilization factor exists at the highest value of the power output and overall efficiency of the hybrid system.

With the progress of technology and the fast growing demand for ubiquitous high-speed wireless services, flexible resource sharing is widely seen to be an important feature for the deployment of beyond 3G systems. Therefore, a migration from fixed allocations to a more flexible spectrum management has to be taken into account. In this context, inter-operator resource sharing in a broadband network is considered in this paper. A packet-based cellular network is developed, emphasizing the shift in the telecommunications industry towards IP-based services. We show that we can improve the overall efficiency of the system by sharing different resources in the network between several operators. Moreover, big and small operators, in addition to customers are altogether satisfied. In this paper, we use the term "resource" to not only account for spectrum sharing but also towers, base stations and time slots sharing. In our framework, we will use a physical layer cellular model with idealistic resource management, where we quantify the achievable sharing gains. We compare the performances for the non sharing case, the case where the base stations decide to share the resources as a "last resort", and also when the mobile stations always connect to the best base station, regardless of the operator. Finally, We analyze these gains in terms of quality of service, number of operators and different service classes.

Solid Oxide Fuel Cell (SOFC) integrated with a Gas Turbine (GT) is a highly efficient way to convert chemical energy of hydro carbon fuel into electrical energy. SOFC-GT is a high temperature, high pressure system and features a fuel flexibility, which makes it easier to retrofit into the existing power plants. A lot of research had already taken place to make SOFC-GT more fuel efficient and cost effective as well. SOFC-GT is a complex thermodynamic electro-chemical system that has numerous input variables that affect the overall efficiency of the system. In order to further develop the SOFC-GT technology and future research, clear understanding is required to analyze relationship between the input and output parameters. One way to analyze the input/output relationship over the range of parameter variations is to conduct a probabilistic sensitivity analysis. A probabilistic sensitivity analysis of 19 input variables has been conducted to understand how each variable would affect the net power output and overall efficiency of a SOFC-GT system.

Unidirectional inductive power transfer systems allow loads to consume power, while bidirectional inductive power transfer (BIPT) systems are more suitable for loads requiring two-way power flow such as vehicle to grid applications with electric vehicles. Many attempts have been made to improve the performance of BIPT systems. In a typical BIPT system, the output power is controlled using the pickup converter phase shift angle, while the primary converter regulates the input current. This paper proposes an optimized phase-shift modulation strategy to minimize the coil losses of a series–series compensated BIPT system. In addition, a comprehensive study on the impact of power converters on the overall efficiency of the system is also presented. A closed-loop controller is proposed to optimize the overall efficiency of the BIPT system. Theoretical results are presented in comparison to both simulations and measurements of a 0.5 kW prototype to show the benefits of the proposed concept. Results convincingly demonstrate the applicability of the proposed system offering high efficiency over a wide range of output power.

An innovative combined hydraulic and gear-train power transmissions system for Mega-Watt scale wind turbines is proposed herein. The proposed concept targets large-scale wind turbines for an efficient and reliable conversion of the mechanical power of the rotating blades to electrical power. The novel hybrid system presented in this approach takes advantage of the benefits of both hydraulic and conventional gearbox systems, without introducing their potential inherent undesirable attributes at large scale. The proposed design first converts the mechanical power of the turbine blades to hydraulic power at a relatively high-pressure (about 2,500 psi) under a relatively low-speed (about 4 in/sec). The hydraulic fluid exiting the discharge port of the low-speed hydraulic pump is branched out into plurality of hydraulic lines for the purpose of dividing the total mechanical power of the wind turbine into multitude of lower hydraulic power lines. Each hydraulic line then delivers its hydraulic power into the corresponding intake port of a hydraulic motor having a low-speed-high-torque output shaft. The output shaft of each of the hydraulic motors then drives the input shaft of a mechanically matched gearbox to increase the rotary speed. Finally, the high-speed output shaft of each gearbox (about 1800 RPM) drives a corresponding matched electric generator. A preliminary design for a variable displacement vane pump has been proposed in this paper. This work includes a theoretical analysis of the overall efficiency of the system. The combined volumetric, mechanical, and overall efficiency of a typical proposed system was shown to be about 98%.

One important objective in measuring efficiency is to find the factors that cause inefficiencies so that its performance can be improved. The conventional data envelopment analysis approach is able to decompose the overall efficiency of a system into the product of the technical and scale efficiencies when the internal structure is ignored. For two-stage systems, where the inputs are supplied to the first process to produce intermediate products for the second process to produce the final outputs, the system efficiency can be decomposed into process efficiencies. This paper further decomposes each process efficiency into the product of the technical and scale efficiencies via an input-oriented model for the first process and an output-oriented one for the second. The decomposition also reveals that the overall efficiency of the two-stage system, when the operations of the two processes are considered, is still the product of the technical and scale efficiencies. The concept is illustrated using an example of 24 non-life insurance companies in Taiwan.KeywordsData envelopment analysisTwo-stage systemScale efficiencyTechnical efficiency