Photovoltaic-powered Reverse Osmosis Research Articles

Practical design of a small-scale PVRO desalination unit using longtime measured water quality reports: A case study for Khuzestan, Iran

This study aims to present a practical design of a small-scale photovoltaic-powered reverse osmosis desalination unit (PVRO) based on a local river’s 9-year measured water analysis reports for Buzi-ye Seyf village. After preprocessing the dataset, we used WAVE software to design the RO system, considering nine scenarios containing the most extreme possible situations regarding feed water total dissolved solids (TDS) and temperature. Next, considering negligible desalination electricity tariffs in Iran, the photovoltaic system was designed using PVSOL software with two targets: CO2 reduction and peak shaving in daytime peak hours during spring and summer. During these seasons' 184-day period, the PV system managed to meet the energy demand for 154 days, exporting 2332.86 kWh to the grid and importing only 136.8 kWh from the grid on days when energy fell short. It was found that in the feed water TDS of 3035 mg/L, every 10 degree elevation in the feed water temperature results in an 83.33 Wh/m3 reduction in the SEC and a 70.49 mg/L rise in the permeate water TDS. Analyzing the scenarios demonstrated that the influence of increasing TDS had a more significant effect on SEC compared to the reduction in temperature. In addition, the PV system was shown to successfully achieve the task of peak-shaving for the investigated period while preventing 15467 kg of CO2 emissions per year. Thus, the designed system provided a practical way of solving the drinkable water issue in Buzi-ye Seyf and areas with similar conditions.

A feasibility study of a small-scale photovoltaic-powered reverse osmosis desalination plant for potable water and salt production in Madura Island: A techno-economic evaluation

• Techno-economic analysis of a small-scale PV-RO desalination plant in Madura Island. • Potable water production of 11.6 m 3 /day with an annual solar contribution of 84 % • The levelized cost of water production using PV-RO desalination plant is 9.0 USD/m 3. • Payback period of PV-RO plant is 4 years for plant lifetime of 25 years. • PV-RO plant usage can increase salt production effectiveness of the salt farmers. The use of reverse osmosis (RO) desalination plant powered by a photovoltaic (PV) system is an attractive solution for small-scale applications in Madura Island (Indonesia). In this paper, the techno-economic feasibility of a small-scale grid-connected PV-RO desalination plant has been carried out in Madura Island for a plant capacity of 11.6 m 3 /day. The RO brine concentrate is utilized for valuable salt production-via-evaporation ponds that allowed the reduction of the required size in the conventional salt evaporation ponds. The steady-state numerical model of the RO desalination plant was used to predict the plant's performance using the characteristics of commercial RO elements. The PV array simulation was carried out using a dynamic modelling and simulation program based on weather data of Madura Island. The result illustrates that the production of potable water and salt using a community-scale grid-connected PV-RO plant is economically viable to be implemented in the region. The payback period of this PV-RO plant is around 4 years for a considered plant lifetime of 25 years with an annual solar contribution of 84 %. The Levelized cost of water production using the PV-RO plant is about 9.0 USD/m 3 which is more cost-effective than the current cost of potable water in the region. Besides, the use of solar-assisted RO desalination plants in water-stressed regions such as Madura Island allows for mitigating the greenhouse gas emissions associated with seawater desalination.

Techno-Economic Optimization of a Solar–Wind Hybrid System to Power a Large-Scale Reverse Osmosis Desalination Plant

Solar-wind hybrid systems have grown to become a pivotal option for powering membrane desalination processes, especially because they have zero harmful emissions. In this work, solar photovoltaic (PV) and horizontal wind turbine (HWT) systems were used to drive a reverse osmosis (RO) desalination process to produce large-capacity fresh water. Moreover, an investigation into a hybrid PV–HWT system combined with RO was also conducted. The proposed systems are compared technically and economically with the solar organic Rankine cycle (SORC) for RO. Technical and analytical optimization methods were performed to minimize the unit product cost (USD/m3). The results revealed that photovoltaic-powered RO is recommended over wind energy operations. However, for large capacities, both thermal and wind farms dominate.

Real-time computational imaging of reverse osmosis membrane scaling under intermittent operation

Small-scale photovoltaic-powered reverse osmosis (PVRO) could be a game-changer for off-the-grid water-stressed communities. However, cost and maintainability issues, due to membrane fouling, remain potentially major limitations of intermittently run PVRO. In particular, there is a common perception that this intermittent operation causes premature membrane degradation but has not been fully evaluated to date. This study seeks to understand the impacts of intermittent operation on mineral scaling propagation in PVRO through real-time imaging and post-operation morphological analysis of the scales. Lab-mixed synthetic groundwater, supersaturated with CaSO4, was used as the feedwater to scale BW30 RO membranes. Then, scaling growth on a statistically significant portion of a spacer-filled RO crossflow channel was imaged in real-time. Comparison between continuous (24 h) and intermittent (8 h/d × 3 d) experiments did not indicate any negative effect of periodic shutdowns on flux decline, which is contrary to the perception that intermittent operation decrease membrane permeability. In-situ imaging further supported this observation and highlighted a slower growth of intensive scaling spots under intermittent operation. After intermittent shut-off periods, the scaling distribution on the membrane appeared thinner and more uniform, hinting a momentary osmotic backflow at the end of each intermittent cycle. Scanning electron microscopy also confirmed the reduced CaSO4 scale growth and a different morphological structure of the scales under intermittent RO operation. This macro-scale imaging and postprocessing approach can aid in the development of optimized backwash and rinsing cycles, reducing fouling-related irreversible damage to the membrane and increasing the accessibility of PVRO for remote communities.

Renewable Energy Powered Membrane Technology: Electrical Energy Storage Options for a Photovoltaic-Powered Brackish Water Desalination System

The potential for lithium-ion (Li-ion) batteries and supercapacitors (SCs) to overcome long-term (one day) and short-term (a few minutes) solar irradiance fluctuations with high-temporal-resolution (one s) on a photovoltaic-powered reverse osmosis membrane (PV-membrane) system was investigated. Experiments were conducted using synthetic brackish water (5-g/L sodium chloride) with varied battery capacities (100, 70, 50, 40, 30 and 20 Ah) to evaluate the effect of decreasing the energy storage capacities. A comparison was made between SCs and batteries to determine system performance on a “partly cloudyday”. With fully charged batteries, clean drinking water was produced at an average specific energy consumption (SEC) of 4 kWh/m3. The daily water production improved from 663 L to 767 L (16% increase) and average electrical conductivity decreased from 310 µS/cm to 274 μS/cm (12% improvement), compared to the battery-less system. Enhanced water production occurred when the initial battery capacity was >50 Ah. On a “sunny” and “very cloudy” day with fully charged batteries, water production increased by 15% and 80%, while water quality improved by 18% and 21%, respectively. The SCs enabled a 9% increase in water production and 13% improvement in the average SEC on the “partly cloudy day” when compared to the reference system performance (without SCs).

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.

Autonomous operation and maintenance of small-scale PVRO systems for remote communities

Solar-powered reverse osmosis desalination (Photovoltaic-powered reverse osmosis [PVRO]) is a technically feasible method of providing fresh water to many remote communities with saline water sources. To be practical, these systems must be well operated and maintained by non-experts. Their productivity is a complex function of their locations, water chemistry and demand, and the solar radiation history at their locations, which is quite variable with time. A key aspect of the maintenance program is the cleaning of the reverse osmosis (RO) membranes, including system flushing and chemical cleaning. Guidelines for cleaning from membrane manufacturers do not consider the complex, variable operating conditions for these small solar-powered systems. Local operators do not have the expertise to determine how and when cleaning should be done. While cleaning will generally improve clean water production, it is costly, requires the system to be shut down, and uses some of the clean water produced. Here, simple, physics-based models of RO membrane fouling and remediation are used to find maintenance schedules that maximize water produced by a small-scale PVRO system under deterministic conditions, such as found in large RO plants using conventional grid power. However, it is shown that for small PVRO systems working in remote locations, the large uncertainties have a significant impact on optimal cleaning schedules.

Reverse-Osmosis Desalination of Water Powered by Photo-Voltaic Modules

The rising of the world’s population leads automatically to the rising of water demand. As a consequence the lack of drinking water increases. Currently, approximately 1.2 billion people globally (one-sixth of the world’s population) do not have access to adequate clean water. Since a large part of the world’s population is concentrated in coastal areas, the desalination of seawater seems to be a promising solution, especially in our Arab world. An innovative stand-alone solar desalination system could be used to produce drinking water from seawater or any brackish water sources. The great advantage of such a system is that it combines efficient desalination technology, reverse osmosis, with a renewable energy source; the main goal is improving the technical feasibility of such systems. There are many advantages of this coupling with RE resources; first of all we separate the drinking water from the electricity grid and its faults, save the burning fossil fuel and its emissions and can provide fresh water to remote communities that do not have sufficient traditional energy sources; but as we see in the thesis we don’t have economic benefit; because these projects depend on the electricity cost in each country and its location and its solar specifications. We design and implement a small laboratorial model for PV-RO (Photo-Voltaic Powered Reverse Osmosis) to recognize the its performance for seawater and brackish water; many of the problems are interrupted such as embargo on Syria; so we see this project has to be done according to affordable local potentialities, but we crave to keep the principle of operation, so we make it for the tap water which close to brackish.

Thermal control to maximize photovoltaic powered reverse osmosis desalination systems productivity

Photovoltaic-powered reverse osmosis (PV/RO) is a practical method for desalinating water, especially for many small, remote, off-grid communities. It is shown here that thermal control can increase its productivity, making it more economically attractive. A solar panel produces more power at lower cell temperatures and an RO unit produces more fresh water for a given power with increasing water temperature. These complementary behaviors are exploited by cooling the solar panel using the RO feed water, which warms the water. Cooling the solar panel also permits the use of concentrating mirrors, which further increases system production. The control must also prevent overheating of the panel and the RO unit, and to balance the pressures in the system. Here, a controller is designed to meet these objectives. The effectiveness of controller design is verified in simulation and experiment.

Photovoltaic reverse osmosis — Feasibility and a pathway to develop technology

Small-scale photovoltaic-powered reverse osmosis (PVRO) desalination plants can provide fresh water to remote communities that do not have sufficient natural sources. For these systems to be practical, they must be both technically and economically feasible. This paper presents a research program that is focused on improving the feasibility of PVRO systems. As the first step in this pro gram, a methodology to evaluate the economic feasibility was developed. The results, reviewed here, show that the economic feasibility is a strong function of location. The results also show that increasing the efficiency of PVRO systems can extend their feasibility to currently marginal or un feasible locations. A focus of this research program is the development of smart control algorithms to increase system efficiency and improve feasibility. This paper presents PVRO system models which have been developed to evaluate the smart control algorithms. These models are verified using an experimental system also described here. Early experimental results are presented that show good agreement with the analytical models.

On the feasibility of community-scale photovoltaic-powered reverse osmosis desalination systems for remote locations

This paper presents a generalized methodology to evaluate the feasibility of photovoltaic-powered reverse osmosis (PVRO) systems for small, remote communities in challenging environments. The economic feasibility is determined by comparing the cost of water from a photovoltaic reverse osmosis system with the cost of water obtained using conventional diesel-powered reverse osmosis. For PVRO systems, the feasibility is a function of location due to variation in solar resource, water type, system demand and local governmental policies. A series of sample cases were analyzed to demonstrate the method. Analysis for community-scale seawater reverse osmosis systems was carried out for various locations using Geographic Information System (GIS) data. A site-specific analysis has been completed for seawater and brackish water reverse osmosis systems. It was found that photovoltaic-powered reverse osmosis is feasible for the majority of remote locations with a large solar resource.

Optimization of solar-powered reverse osmosis desalination pilot plant using response surface methodology

A solar thermal and photovoltaic-powered reverse osmosis (RO) desalination plant has been constructed and optimized for brackish water desalination. The central composite experimental design of orthogonal type and response surface methodology (RSM) have been used to develop predictive models for simulation and optimization of different responses such as the salt rejection coefficient, the specific permeate flux and the RO specific performance index that takes into consideration the salt rejection coefficient, the permeate flux, the energy consumption and the conversion factor. The considered input variables were the feed temperature, the feed flow-rate and the feed pressure. Analysis of variance (ANOVA) has been employed to test the significance of the RSM polynomial models. The optimum operating conditions have been determined using the step adjusting gradient method. An optimum RO specific performance index has been achieved experimentally under the obtained optimal conditions. The RO optimized plant guarantees a potable water production of 0.2 m 3/day with energy consumption lower than 1.3 kWh/m 3.

Small-scale photovoltaic-powered reverse osmosis plant without batteries: Design and simulation

A small-scale photovoltaic (PV) powered reverse osmosis (RO) plant is designed to operate at variable flow/pressure conditions for stand-alone applications in equatorial areas to desalinate brackish water. Two operation strategies for a PV array of 165 Wp (3 modules of 55 Wp) are simulated and compared: Plant 1 uses two modules for the RO pump and one module for the well pumping; Plant 2 uses the three modules for both applications. A DC–DC buck converter with maximum power point tracking (MPPT) was developed especially for Plant 2. Results show that Plant 2 has a better performance, such as: increase of 60% in the daily permeate production and of 32% in the daily operation period, 1.57 kWh.m −3 of average specific energy consumption and a PV power-permeate daily production rate of 0.64 Wp.L −1 for a feed water with 800 mg.L −1 of total dissolved solid.

Solar-driven desalination with reverse osmosis: the state of the art

Solar-driven reverse osmosis desalination can potentially break the dependence of conventional desalination on fossil fuels, reduce operational costs, and improve environmental sustainability. The experience with solar desalination is investigated based on the analysis of 79 experimental and design systems worldwide. Our results show that photovoltaic-powered reverse osmosis is technically mature and — at unit costs as low as 2–3 US$ m –3 — economically cost-competitive with other water supply sources for small-scale systems in remote areas. Under favourable conditions, hybrid systems with additional renewable or conventional power sources perform as good as or better than photovoltaic-powered reverse osmosis. We suggest that in the short-term, solar RO desalination will gain shares in the market of small-scale desalination in remote areas. Concentrating solar power technologies have the highest potential in the medium-term for breakthrough developments in large-scale solar desalination.

Stand-alone groundwater desalination system using reverse osmosis combined with a cooled greenhouse for use in arid and semi-arid zones of India

In many areas of northern India, salinity renders groundwater unsuitable for drinking and even for irrigation. Though membrane treatment can be used to remove the salt, there are some drawbacks to this approach e.g. (1) depletion of the groundwater due to over-abstraction, (2) saline contamination of surface water and soil caused by concentrate disposal and (3) high electricity usage. To address these issues, a system is proposed in which a photovoltaic-powered reverse osmosis (RO) system is used to irrigate a greenhouse (GH) in a stand-alone arrangement. The concentrate from the RO is supplied to an evaporative cooling system, thus reducing the volume of the concentrate so that finally it can be evaporated in a pond to solid for safe disposal. Based on typical meteorological data for Delhi, calculations based on mass and energy balance are presented to assess the sizing and cost of the system. It is shown that solar radiation, freshwater output and evapotranspiration demand are readily matched due to the approximately linear relation among these variables. The demand for concentrate varies independently, however, thus favouring the use of a variable recovery arrangement. Though enough water may be harvested from the GH roof to provide year-round irrigation, this would require considerable storage. Some practical options for storage tanks are discussed. An alternative use of rainwater is in misting to reduce peak temperatures in the summer. An example optimised design provides internal temperatures below 30EC (monthly average daily maxima) for 8 months of the year and costs about €36,000 for the whole system with GH floor area of 1000 m2 . Further work is needed to assess technical risks relating to scale-deposition in the membrane and evaporative pads, and to develop a business model that will allow such a project to succeed in the Indian rural context.

The Brazilian experience with a photovoltaic powered reverse osmosis plant

AbstractThis article describes a system that combines the technologies of reverse osmosis and photovoltaics to realize a pioneer project for drinking water supply to a rural community in semi‐arid Brazil (latitude 3°44′S), with a local yearly average temperature of 28°C and a yearly solar potential of about 2000 kW h m−2. Two strategies are investigated: first the PV‐RO (photovoltaic powered reverse osmosis) plant is equipped with a DC motor; and second, a three‐phase induction motor is used. Through the analysis of the stored data the second option is chosen as the better alternative. This strategy has a specific electrical consumption (energy required to produce 1 m3 drinking water) of 3·03 kW h m−3, a recovery ratio of 27% (relation between drinking water product flow and brackish water input flow) and a drinking water cost of US$ 12·76 per m3. Copyright © 2004 John Wiley & Sons, Ltd.