A feasibility study of pressure‐retarded osmosis power generation system based on measuring permeation volume using reverse osmosis membrane

Pressure Retarded Osmosis (PRO) power generation system is a hydroelectric power system which utilize permeation flow through a semi-permeable membrane. Permeation flow is generated by potential energy of salinity difference between sea water and fresh water. As membrane cost is expensive, permeation performance of membrane must be higher to realize PRO system. We have investigated Reverse Osmosis (RO) membrane products as semi-permeable membrane and measured permeation volume of a few products. Generation power by membrane area calculated from permeation volume is about 0.62W/m2. But by our improvements (more salt water volume, spacer of fresh water channel with a function of discharging concentrated salinity, extra low pressure type of membrane, washing support layer of membrane when generation power reduces to half), generation power may be 2.43W/m2. Then power system cost is about 4.1 million yen/kW. In addition, if support layer of membrane makes thinner and PRO system is applied to the equipment that pumping power on another purpose is avairable (wastewater treatment plant located at the seaside, thermal and nuclear power plant or sea water desalination plant), generation power may be more. By these improvements PRO system may be able to realize at the cost close to photovoltaic power system.

Overview of pressure-retarded osmosis (PRO) process and hybrid application to sea water reverse osmosis process

Integration and optimization of pressure retarded osmosis with reverse osmosis for power generation and high efficiency desalination

Comparison of fouling characteristics between reverse electrodialysis (RED) and pressure retarded osmosis (PRO)

Synthesis and characterization of high-performance novel thin film nanocomposite PRO membranes with tiered nanofiber support reinforced by functionalized carbon nanotubes

There is a natural tendency for salt solutions to be diluted by freshwater. This natural force appears as osmotic pressure. One process of capturing the energy released from the mixing of freshwater with saltwater is pressure‐retarded osmosis (PRO). In PRO, water from a low salinity solution permeates through a membrane into a pressurized, high salinity solution; effectively transforming water chemical potential into hydraulic head (i.e., potential energy). The combination of increased interest in renewable and sustainable sources of power production and the recent progress in membrane science has led to a spike in PRO interest in the past decade. This interest culminated in the first experimental “river‐to‐sea” PRO installation, which opened in Norway in 2009. Additional applications of PRO, including reverse osmosis (RO)–PRO systems and osmotic heat engines have since gained attention. Although river‐to‐sea PRO has the potential to be a reliable source of base‐load power, the higher salinity gradient available for power production in RO–PRO systems is likely to make them a more promising component of an alternative energy portfolio. While RO–PRO systems are in the early stages of development, the possibility of PRO to enable significant energy reductions in RO energy costs are driving interest in these systems. For all applications, development of optimized and inexpensive PRO membranes is necessary. This article will provide the theoretical foundation of the PRO process as well as the state of the art of the membranes used in this process. It will also outline the development of the river‐to‐sea PRO, RO–PRO, and osmotic heat engine systems and discuss their capabilities, limitations, and future as alternative energy sources.

Enhancing pressure retarded osmosis performance with low-pressure nanofiltration pretreatment: Membrane fouling analysis and mitigation

The development of renewable energy technologies is of global importance. To realize a sustainable society, fossil-resource-independent technologies, such as solar- and wind-power generation, should be widely adopted. Pressure retarded osmosis (PRO) is one such potential renewable energy technology. PRO requires salt water and fresh water, both of which can be found at seawater desalination plants. The total power generation capacity of PRO, using concentrated seawater and fresh water, is 3 GW. A large amount of energy is required for seawater desalination; therefore, the introduction of renewable energy should be prioritized. Kyowakiden Industry Co., Ltd., has been working on introducing PRO to seawater desalination plants since 2001 and is attracting attention for its ongoing PRO pilot plant with a scale of 460 m3/d, using concentrated seawater and treated sewage water. In this study, we evaluated the feasibility of introducing PRO in existing desalination plants. The feasibility was examined based on technology, operation, and economy. Based on the number of seawater desalination plants in each country and the electricity charges, it was determined whether the introduction of PRO would be viable.

Influence of membrane support layer hydrophobicity on water flux in osmotically driven membrane processes

Power generation with salinity gradient by pressure retarded osmosis using concentrated brine from SWRO system and treated sewage as pure water

A techno-economic process model for pressure retarded osmosis based energy recovery in desalination plants

Clean forms of renewable energy with low to no environmental impact are highly desirable. Pressure Retarded Osmosis (PRO) has been a growing form of “Blue Energy” [1], a renewable energy medium involving mixing bodies of salt and fresh water. PRO systems take advantage of the pressure difference seen between freshwater and seawater by forcing fresh water across a semipermeable membrane into a body of saltwater. This transfer, through the means of forward osmosis, yields an increase in pressure on the saltwater side of the membrane. This observable increase in pressure can be used for generating electricity. A popular thought proposed has involved taking a part of this newly created pressure and diverting it back into the system with the use of a pressure exchanger. Residual pressure would then be devoted to the generation of electricity. If done correctly, a net gain can be seen between the electricity gleaned from the output of the system, and the energy consumed to run the pumps necessary for operation. The group’s aim is to design and construct a variant of the traditional PRO system for the purpose of analysis in a laboratory setting. The design proposed consists of a compact, two-membrane system that allows for the testing and analysis of forward osmosis in a closed system. While the system is not intended for actual electrical generation, it provides a medium for future experimentation.

Pressure retarded osmosis: Advancement, challenges and potential

Energy recovery by pressure retarded osmosis (PRO) in SWRO–PRO integrated processes

Modeling and simulation of the dual stage pressure retarded osmosis systems