Performance analysis of a small wind powered reverse osmosis plant

A stand-alone systems analysis approach has been taken to the performance assessment of a small wind powered reverse osmosis plant. The study is concerned with the sensitivity of operation to key parameters: wind speed, battery storage capacity and reverse osmosis operating pressure. It is demonstrated that the results of such a system analysis can be inconsistent with more simplistic approaches sometimes adopted in this applications area. A provisional calculation of annual expected water delivery has also been undertaken. Detailed modelling results are presented and discussed. Given that only discrete sizes of reverse osmosis equipment are in practice available, it is concluded that the ideal operational pressure is not always the maximum design pressure, but can depend on the site wind speed. Since water storage is far cheaper than electricity storage, there is motivation to minimise the capacity of the battery store. The most effective battery capacity would seem to be in the range of 4 to 8 h at nominal rated load for the reverse osmosis plant, with the actual value critically dependent on wind speed at the site.     

Energy and exergy analysis of solar PV powered reverse osmosis desalination

In the current paper presented short review of the state of the art of solar powered reverse osmosis (RO) desalination systems, basic parameters, energy demand of RO process and also exergy analysis. In order to identify the main energy losses in desalination processes, to improve their performances from a thermodynamic point of view, there is a need for exergy analysis. The exergy analysis or second law analysis involves a comparison of exergy input and exergy destruction along various desalination processes. Using the exergy analysis methodology, presented in the current paper, the specific exergy and exergy flow rates at various points of a RO system can be evaluated. Once exergy flow rates are available, exergy destroyed within any component can be determined from exergy balance.     

Effect of feed pressure on the performance of the photovoltaic powered reverse osmosis seawater desalination system

This paper describes the potential of the development of a seawater desalination system that combines the technologies of reverse osmosis (RO) and photovoltaic (PV) to deliver 100 m³/day of sweet water. Silicon cells are chosen for the PV array and the polyamide thin-film composite seawater Filmtec membranes are selected for the RO system. The software ROSA is adopted to study the influences of the feed pressure on the performance of the system. It is found that as the feed pressure increases, the specific energy of the plant decreases but the percentage of recovery increases.     

Performance of reverse osmosis pilot plant powered by Photovoltaic in Jordan

This paper presents the work performed within ADIRA project funded by European Union as a consortium of many countries to boost the integration of desalination units with renewable energy in rural areas. The work focused on the study of Water desalination by Reverse Osmosis (RO) and electricity generation using Photovoltaic Technology (PV) with additional battery storage. RO-PV system has been successfully designed, installed and tested in Hartha Charitable Society in northern part of Jordan as part of the ADIRA project. The system is composed of PV panels (433 Wp), softener and compact RO unit with typical daily water production of 500 L. The system produced clean drinking water from a salty water feed with salt content up to 1700 mg/L. The technical details of the RO plant, the energy supply and the operation strategies of the system are presented in this study. The effect of meteorological data like solar insolation, ambient temperature, daily sunshine hours on the performance of the RO-PV system are studied. Furthermore, effect of operating pressure and temperature on recovery percentage, salt rejection and specific energy consumption in addition to details about the PV current and voltage are also discussed.     

基于超级电容的风光互补反渗透水处理系统的设计

为降低风/光供能波动对水处理反渗透膜组件的危害,设计了基于超级电容的风光互补反渗透水处理系统。超级电容阵列作为缓冲装置加入供电电路中,以化解前端的电压波动,又能为后端水处理模块提供稳定的输出电压;根据水处理模块的运行特点,设计了合理的控制策略,解决该模块与供能及储能模块的供求不匹配问题;利用atmega328p-au单片机以及树莓派(raspberry pi B+)等硬件设备,实现各模块参数的在线显示与实时控制,数据的采集、转换、存储及远程监控。     

Design and experimental performance of brackish water reverse osmosis desalination unit powered by 2 kW photovoltaic system

Small-scale brackish water reverse osmosis (BWRO) desalination units are not a major commercial success compared to its large-scale counterpart. Integrating renewable power systems with small-scale units would theoretically aid in their deployment and subsequent commercial success. In fact, RO units are constructed using a modular approach; this would allow them to adapt to a renewable power supply. Small-scale PV-RO would be a promising form of desalination system in remote areas, where BW is more common. The aim of this study is to quantify the effect of climatic-design-operation conditions on the performance and durability of a PV-BWRO desalination system. A small-scale unit is designed, constructed, and tested for 6 months. The design was limited to a 2 kWp PV power system, five different membranes, a feed TDS of 2000 mg/l, and a permeate TDS of less than 50 mg/l. Data pertaining to solar radiation and temperature were subsequently analyzed to determine their respective influences on current and future operations of the unit. The results showed that the optimum RO load, membrane type, and design configuration were 600 W, (4″x40″ TW30-4040), and a two-stage configuration, respectively. The PV system was able to supply the load without any significant disturbances; while the RO unit showed stable levels of permeate flow and salinity. Operating the PV-BWRO system for 10 h during the day would produce 5.1 m3 of fresh water at a specific energy of 1.1 kWh/m3. It was confirmed that there are many hours of high temperatures during the operation of the PV module (exceeding 45 °C) and battery room conditions (exceeding 35 °C), both of which could negatively affect the power output and battery autonomy. This negative effect is compounded annually; therefore, optimizing thermal regulation of PV modules and battery bank room conditions is essential in maintaining excellent operating temperatures.     

Solar electric powered reverse osmosis water desalination system for the rural village,Al Maleh: design and simulation

Desalination of brackish water by using reverse osmosis (RO) system powered by solar PV has not been tried and examined in Palestine until now. This paper proposes rural village Al Maleh for erection and testing of the first PV-powered RO system. Al Maleh is highly qualified for testing of such systems since it has a lot of mineral hot water springs of about 3400?ppm salinity. Based on the climate conditions in Al Maleh, the paper presents the design of the PV-powered RO water desalination system. The obtained design results can be used for an economic feasibility study of this technology [Mahmoud, M. Techno-economic feasibility of PV-powered water desalination in Palestine. Special Case: Al Maleh Village (to be published).]. The performance of the designed system is investigated by software simulation. The obtained results show that a daily production of 1?m³ from the brackish water in Al Maleh would require about 820 peak watt of PV generator.     

An optimization algorithm-based pinch analysis and GA for an off-grid batteryless photovoltaic-powered reverse osmosis desalination system

Freshwater pinch analysis (FWaPA) as an extended pinch analysis technique has been proposed for retrofitting the off-grid batteryless photovoltaic-powered reverse osmosis system (PVS-RO) with a water storage tank to minimize the required outsourced freshwater. The freshwater composite curve (FWaCC) as the graphical tool, and freshwater storage cascade table (FWaSCT) as the numerical tool of the FWaPA are introduced to determine the optimal delivered electricity to the RO system, water storage tank capacity, and wasted electricity in each time-interval with minimized outsourced freshwater. A multi-objective optimization algorithm by combining FWaPA numerical tool and genetic algorithm (FWaPA-GA) minimizes three objective functions including required outsourced freshwater during first operation year, outsourced freshwater during normal operation year, and total annual cost of the system to obtain the optimal number of PV panels, membranes, and capacity of water storage tank. The FWaPA-GA was implemented to find optimal design of an off-grid PVS-RO-WT system for a case study in Kish island, Iran. The results clearly represented that the FWaPA-GA can be used to grassroots design of the desalination systems with renewable energy sources, where the designed PVS-RO-WT system for the case study needs 178.5 m³ freshwater to provide 10 m³/d freshwater-on-demand with the total annual cost of 13,652 $/year.     

Large-scale time evaluation for energy estimation of stand-alone hybrid photovoltaic–wind system feeding a reverse osmosis desalination unit

In this study, energy and water production estimation on a large-scale time from Photovoltaic–Wind hybrid system coupled to a reverse osmosis desalination unit in southern Tunisia has been elaborated. The use of a hybrid system for desalination appears nowadays as a very promising solution for remote and arid areas. The produced energy is used for potable water production. For energy production, metrological data (wind speed, solar irradiance…) and steady-state models have been used. The obtained results show that the hybrid solution (solar and wind) gives an energy availability during the year, despite changing energy according to daytime, season and year. The reverse osmosis desalination unit powered by Photovoltaic–Wind hybrid system for producing potable water from brackish water is an appropriate solution to southern Tunisia (salinity about 6 g/l). For this, compositions of brackish feed water in Djerba region were selected. Double stage configuration in the desalination process using spiral modules is adopted extensively and validation of the steady-state models is presented.     

Review of brackish water reverse osmosis (BWRO) system designs

Brackish water are any water sources with TDS between 1000 and 15 000 mg/L. Brackish water cannot be consumed by us directly due to its high salinity. According to World Health Organization (WHO), water with salinity below 500 mg/L is acceptable as drinking water. There are quite a large number of research that had been done on BWRO. Each of them has agreed with a common design on optimum BWRO design with a slight modification in order to improve more and make a better BWRO system. BWRO systems which have been tested in real situation agree that the single stage system with module connected to reject water is the most optimum system both economically and environmentally. There is some improvement done to the design by using SWRO membrane at the second stage. This improvement increases recovery rate to about 83% and reduces boron concentration at the same time. Another design is by using hybrid combination of ultra-low and conventional RO membranes. Hybrid improves permeate quality. It is also possible to create a hybrid array by mixing membrane element types within a pressure vessel itself. Co-operating an efficient module arrangement into a complete BWRO system will reduce energy consumption. Energy-recovery device is a component that must be included in any small or large-scale systems. A small-scale RO system, without energy recovery, would typically consume two to three times more energy. This will be more for large-scale systems. While single stage system with module connected to reject water is preferred by researchers who have done real environment testing, simulation prefers to add another membrane to the reject water of the second module. This system is yet to be tested in real environment to prove its standing.     

Second law analysis of reverse osmosis desalination plants: An alternative design using pressure retarded osmosis

A second law analysis of a reverse osmosis desalination plant is carried out using reliable seawater exergy formulation instead of a common model in literature that represents seawater as an ideal mixture of liquid water and solid sodium chloride. The analysis is performed using reverse osmosis desalination plant data and compared with results previously published using the ideal mixture model. It is demonstrated that the previous model has serious shortcomings, particularly with regard to calculation of the seawater flow exergy, the minimum work of separation, and the second law efficiency. The most up-to-date thermodynamic properties of seawater, as needed to conduct an exergy analysis, are given as correlations in this paper. From this new analysis, it is found that the studied reverse osmosis desalination plant has very low second law efficiency (<2%) even when using the available energy recovery systems. Therefore, an energy recovery system is proposed using the (PRO) pressure retarded osmotic method. The proposed alternative design has a second law efficiency of 20%, and the input power is reduced by 38% relative to original reverse osmosis system.     

Economic evaluation of reverse osmosis desalination system coupled with tidal energy

A reverse osmosis (RO) desalination system coupled with tidal energy is proposed. The mechanical energy produced by the tidal energy through hydraulic turbine is directly used to drive the RO unit. The system performances and the water cost of the conventional and tidal energy RO systems are compared. It is found that the proposed tidal energy RO system can save water cost in the range of 31.0%-41.7% in comparison with the conventional RO system. There is an optimum feed pressure that leads to the lowest water cost. The tidal RO system can save more costs at a high feed pressure or a high water recovery rate. The optimum feed pressure of the tidal energy RO system is higher than that of the conventional RO system. The longer lifetime of the tidal energy RO system can save even more water cost. When the site development cost rate is lower than 40%, the water cost of the tidal energy RO system will be lower than that of the conventional RO system. The proposed technology will be an effective alternative desalination method in the future.     

Exergy analysis of micro-organic Rankine power cycles for a small scale solar driven reverse osmosis desalination system

Exergy analysis of micro-organic Rankine heat engines is performed to identify the most suitable engine for driving a small scale reverse osmosis desalination system. Three modified engines derived from simple Rankine engine using regeneration (incorporation of regenerator or feedliquid heaters) are analyzed through a novel approach, called exergy-topological method based on the combination of exergy flow graphs, exergy loss graphs, and thermoeconomic graphs. For the investigations, three working fluids are considered: R134a, R245fa and R600. The incorporated devices produce different results with different fluids. Exergy destruction throughout the systems operating with R134a was quantified and illustrated using exergy diagrams. The sites with greater exergy destruction include turbine, evaporator and feedliquid heaters. The most critical components include evaporator, turbine and mixing units. A regenerative heat exchanger has positive effects only when the engine operates with dry fluids; feedliquid heaters improve the degree of thermodynamic perfection of the system but lead to loss in exergetic efficiency. Although, different modifications produce better energy conversion and less exergy destroyed, the improvements are not significant enough and subsequent modifications of the simple Rankine engine cannot be considered as economically profitable for heat source temperature below 100 °C. As illustration, a regenerator increases the system’s energy efficiency by 7%, the degree of thermodynamic perfection by 3.5% while the exergetic efficiency is unchanged in comparison with the simple Rankine cycle, with R600 as working fluid. The impacts of heat source temperature and pinch point temperature difference on engine’s performance are also examined. Finally, results demonstrate that energy analysis combined with the mathematical graph theory is a powerful tool in performance assessments of Rankine based power systems and permits meaningful comparison of different regenerative effects based on their contribution to systems improvements.     

如何估算风电场的装机容量

随着矿物能源资源的有限性和全球环境压力的不断增加,世界上许多国家都承担起了节能减排的义务,认识到了可再生能源特别是风力发电的重要性,并相继出台了一系列政策、法规以促进其发展.     

反渗透海水淡化系统中的能量回收技术及装置研究进展

反渗透法是海水淡化的主要方法之一，能量回收是降低其淡化成本的主要手段。综合介绍了反渗透海水淡化系统中的主要能量回收技术，并对相应的能量回收装置的原理、性能以及应用等做了介绍和比较。     

Operating results of a wind–diesel system which supplies the full energy needs of an isolated village community in the Canary Islands

Following is a discussion of the operational strategies of a wind–diesel system which has been installed in an isolated fishing village community on the island of Fuerteventura in the Canarian Archipelago. The project was implemented with the aim of meeting the complete energy requirements of the community: street lighting and domestic consumption, desalination plant, freezer plant, sewage water purifier, hydrocompressor for the supply of potable water and a winch for small vessels. An analysis is also made of the results which were obtained with respect to the quality of the service supplied, the percentage of wind penetration in the system, fuel savings and the decrease of CO₂ emissions into the atmosphere. A comparison of these results has also been made with the corresponding estimated figures for the performance of the system when originally designed. The conclusion is drawn that, from a technical point of view, the system that has been developed supplies all the service needs of the community on a regular basis with an acceptable level in the quality of the energy and a substantial improvement in the quality of the environment. This is a contributing factor to providing a satisfactory level in the quality of life for the inhabitants of the community.     

Electricity generation cost in isolated system: The complementarities of natural gas and renewables in the Canary Islands

The Canary Islands offer an example of an isolated electric grid of relative important size within the EU. Due to its peculiarities, the role of renewable energies and their complementarity with fossil fuels offers a solid path to achieving the main energy policy goals of the Islands. The purpose of this paper is to assess the current situation and the energy objectives proposed in the Energy Plan of the Canaries (PECAN, 2006) for the electricity industry, taking into account the average cost and the risk associated with the different alternatives for generating electricity by means of the Mean–Variance Portfolio Theory. Our analysis highlights the inefficiency of the current electricity generating mix in terms of cost, risk and lack of diversification. Shifting toward an efficient system would involve optimizing the use of endogenous energy sources and introducing natural gas to generate electricity. This scenario would mean reducing both cost and risk by almost 30% each, as well as atmospheric CO₂ emissions. Our results agree with the PECAN philosophy.     

Exergetic analysis of an innovative small scale combined cycle cogeneration system

The purpose of this paper has been to carry out an exergetic analysis of an innovative natural gas (NG) combined cycle cogeneration system (150-kW_e, 192-kW_t). The combined cycle is composed of a reciprocating Internal Combustion Engine (ICE), which is used as the topping cycle, and a water Rankine cycle (RC), which operates on the exhaust gases from the ICE, as the bottoming cycle.     

Thermal analysis for system uses solar energy as a pressure source for reverse osmosis (RO) water desalination

As Natural resources are becoming limited and energy price dramatically increased, energy utilization with efficient systems is essentially required to be used in desalination technologies. The use of solar energy in desalination processes is one of the most promising applications of renewable energies. The primary focus on desalination by solar energy is suitable for use in remote areas. A proposed desalination system uses solar radiation, which concentrated by parabolic dish to heat up the working fluid in a closed space. Then the generated pressure in this space used to push salt water into RO module.Daily production rate of fresh water quantity for suggested system compared with other solar techniques is a promising rate for each m² of solar radiation collecting surface. The production rate for one operation cycle could reach to 1800 L/cycle of fresh water at low water salinity (Brackish water with 5000 ppm) and 55 L/cycle at highest water salinity (sea water salinity with 42,000 ppm). The required energy needed to produce 1 kg of fresh water is also promising even when in case of using another type of energy, also operating cycle has ability of repetition according to salinity concentration through sunny hours.