• The KSFM Journal of Fluid Machinery
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• v.16 no.1
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• pp.61-65
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• 2013

Water is an integral part of energy production because it is used directly in many power generation systems such as hydroelectric power plants and thermoelectric power plants. Water is also used extensively in energy-resource extraction, oil, natural gas, and alternative fuels refining and processing. Recently, osmotic power systems using seawater and freshwater has been also investigated to produce electricity in a sustainable way. This study focused on the use of RO and PRO for the mutual conversion of water and energy. This system allows the production of water from seawater if there is not enough water. It can also generate electricity from salinity gradient of brine water and fresh water if there is not enough energy. To demonstrate the feasibility of this technology, a set of laboratory-scale experiments were carried out using a specially-designed RO/PRO system. The efficiency of energy conversion was theoretically estimated based on the results from the experiments. The results indicated that water and energy could be easily converted using a single device. Nevertheless, a lack of optimum membrane for this purpose was identified as a major barrier for practical application.

• Journal of Korean Society of Water and Wastewater
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• v.30 no.3
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• pp.299-312
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• 2016

The main objective of this paper is to develop computer simulation program for performance evaluation and cost estimation of a reverse osmosis (RO) and pressure-retarded osmosis (PRO) hybrid process to propose guidelines for its economic competitiveness use in the field. A solution-diffusion model modified with film theory and a simple cost model was applied to the simulation program. Using the simulation program, the effects of various factors, including the Operating conditions, membrane properties, and cost parameters on the RO and RO-PRO hybrid process performance and cost were examined. The simulation results showed that the RO-PRO hybrid process can be economically competitive with the RO process when electricity cost is more than 0.2 $/kWh, the PRO membrane cost is same as RO membrane cost, the power density is more than $8W/m^2$ and PRO recovery is same as 1/(1-RO recovery).

• Membrane Journal
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• v.25 no.2
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• pp.132-143
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• 2015

Water is an essential resource for humans, but fresh water becomes scarce due to population growth and contamination of limited resources. Membrane technology has been widely used for water treatment, and forward osmosis is a process which does not need high hydraulic pressure for the operation. However, there are needs for (1) development of novel draw solutes causing low internal concentration polarization and reverse salt flux for high water flux, and (2) development of economic recovery method of the draw solutes in the diluted draw solution. Previous researches on the draw solute include $NaHCO_3$ which can be regenerated by about $60^{\circ}C$ heating, sucrose which can make potable water without additional process, and magnetic nanoparticles which can be regenerated by external magnetic field. Using the principles of forward osmosis process, sea water desalination, wastewater treatment, refinement of proteins, energy generation using pressure retarded osmosis process, preparation of diluted fertilizer, and growing algae for biofuel can be conducted. This paper summarizes characteristics of ideal draw solutes, recovery method of the draw solutes, and various application examples.

• Journal of Korean Society of Water and Wastewater
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• v.30 no.4
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• pp.401-408
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• 2016

Desalination is getting more attention as an alternative to solve a global water shortage problem in the future. Especially, a desalination technology is being expected as a new growth engine of Korea's overseas plant business besides one of the solutions of domestic water shortage problem. In the past, a thermal evaporation technology was a predominant method in desalination market, but more than 75% of the current market is hold by a membrane-based reverse osmosis technology because of its lower energy consumption rate for desalination. In the future, it is expected to have more energy efficient desalination process. Accordingly, various processes are being developed to further enhance the desalination energy efficiency. One of the promising technologies is a desalination process combined with Pressure Retarded Osmosis (PRO) process. The PRO technology is able to generate energy by using osmotic pressure of seawater or desalination brine. And the other benefits are that it has no emission of $CO_2$ and the limited impact of external environmental factors. However, it is not commercialized yet because a high-performance PRO membrane and module, and a PRO system optimization technology is not sufficiently developed. In this paper, the recent research direction and progress of the SWRO-PRO hybrid desalination was discussed regarding a PRO membrane and module, an energy recovery system, pre-treatment and system optimization technologies, and so on.

• Journal of Korean Society of Environmental Engineers
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• v.38 no.5
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• pp.255-268
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• 2016

Climate change has increased the need to secure a new water resource in addition to the traditional water resources such as surface water and ground water. The seawater desalination market is growing sharply in accordance with this situation in Korea, "seawater engineering & architecture of high efficiency reverse osmosis (SEAHERO)" program was launched in 2007 to keep pace with world market trend. SEAHERO program was completed in 2014, contributed to turn the domestic technology in evaporative desalination technology to RO desalination technology. Currently, it is investigated that the average specific energy consumption of the whole RO plant is around $3.5kWh/m^3$. The Busan Gi-jang plant has shown $3.7{\sim}4.0kWh/m^3$, including operational electricity for plant and maintenance building. Although not world top level, domestic RO technology is considered to be able to compete in desalination market. Separately, many researchers in the world are developing new technologies for energy savings. Various processes, forward osmosis (FO), membrane distillation (MD) process are expected to compete with RO in the future market. In Korea, FO-RO hybrid process, MD and pressure retarded osmosis (PRO) process are under development through the research program in Ministry of Land, Infrastructure and Transport (MOLIT). The desalination technology level is expected to decrease to $2.5kWh/m^3$.