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Development and evaluation of a hybrid photovoltaic reverse osmosis system for treating brackish groundwater

Project ID: 1340
Principal Investigator: Katherine Guerra
Research Topic: Desalination and Water Treatment
Priority Area Assignments: 2014 (Advanced Water Treatment), 2015 (Advanced Water Treatment)
Funded Fiscal Years: 2014
Keywords: renewable energy, solar powered desalination, integrated membrane system

Research Question

The following research questions will be addressed in this research project:

System design:
How should each component of the hybrid system be sized? For example, more PV means more power which can be used to operate the reverse osmosis (RO) at a higher pressure, charge a battery, or run the system at a lower pressure for more hours of the day. What are general guidelines for designing PVRO systems, i.e. how large should the PV system be? How many hours should the PV be sized to operate the high pressure pump of the RO?

Operational considerations:
What unique membrane operational strategies can be employed to make these systems more efficient and cost effective? For example, what pressure/recovery is optimal from an energy efficiency standpoint? Should the operating pressure be altered during operation as a function on incoming power?

Implementation:
How can integrated, renewable energy hybrid systems be implemented for small scale systems to reduce the external energy requirements and cost of developing new water supplies? Are these systems robust and easy to maintain and operate?

How can communities decide between different types of renewable energy or off-grid desalination technologies? How does PVRO compare to solar distillation?

What are the locations within the US that are candidates for applying an integrate PV-RO system?

What are the key system performance and cost parameters that can be compared to other competing technologies?

Can the PV-RO serve as the current industry standard for off-grid desalination systems?

What is necessary for PV/RO systems to be commercially available?

Need and Benefit

In rural areas of the Western United States, there is a need to develop robust, affordable desalination systems powered by renewable energy sources. Environmental conditions in many locations within the southwestern US have abundant solar energy resources, making photovoltaic-desalination hybrid technologies an attractive solution for desalination in rural, off-grid areas.

As a result of limited water and power supply, residents of some remote communities rely on hauling water long distances from centralized treatment facilities or fresh water sources. Hauling water is expensive and inefficient. Therefore, there is an immense need to implement small-scale integrated renewable energy-desalination systems in the remote areas of the Western United States.

While much attention has been raised for areas such as the Navajo Nation in Arizona, a need exists all across the Western United States for rural water solutions. The states of South Dakota, Wyoming, Nebraska, Kansas, Colorado, New Mexico, Oklahoma, and Texas have a need for small scale, off-grid treatment systems due to impaired water quality.

This study will focus on developing an off-grid solution for treating brackish groundwater. Therefore, reverse osmosis will be studied as the desalination technology. RO will be considered because it is the most widely used desalination technology and is also well established. Combining photovoltaic power generation and reverse osmosis makes use of two established technologies. This allows us to characterize a baseline to which novel technologies can be compared and allows us to focus on design, optimization, and evaluation of this process as a proposed solution rather than developing a new desalination technology.

Currently, to the best of our knowledge, there are no commercially available systems available on the market for PVRO. Solar distillation is the most widely available off-grid desalination technology. This project will utilize data from other research projects funded by New Mexico State University and the DWPR program investigating solar distillation to compare to PVRO.

While other research has been published on PVRO, there are two major deficiencies identified in past work*:
1. many published studies present the results of modeling efforts, not actual operation of a PVRO system. One paper that did actual testing identified that modeling efforts can over-predict performance by up to 70%.
2. The few published studies that present actual testing data focus on demonstrating one system that is sized arbitrarily and do not focus on RO operational strategy. This effort will improve upon past work by combining RO experts with electrical design experts to optimize system designs to increase the performance and affordability of these systems for rural communities.

*A literature search has been conducted in this area as part of other work, but due to the limitations of the prop c system, citations, figures, equations, and lengthy text cannot be provided. Literature review can be made available upon request.

This information was last updated on September 30, 2014
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