Hydraulic switch-mode power transformer for wave powered desalination plants

Efficient hydraulic power-take-off circuit for wave-powered reverse osmosis desalination plants that independently controls the load on the wave energy converter and the pressure at the reverse osmosis membrane through a switching valve
Technology No. 2019-321
IP Status: US Patent Pending


  • Wave-powered reverse osmosis (RO) desalination plants
  • Optimization of RO systems in water and wastewater treatment plants
  • Remote actuation in general fluid power applications

Key Benefits & Differentiators

  • Eliminates major design constraints: Using a switch-mode power transformer decouples the operating pressures of the power source and RO process
  • Higher uptime and process control: The electric generator can potentially operate as an electric motor to augment the performance of the transformer
  • Lower equipment costs: New configuration reduces component size requirements related to the power source and uses fewer high cost components than other power transformers,which can result in significant cost savings

Technology Overview

Currently, 1% of the world’s population consumes water from desalination, but the United Nations (UN) estimates that by 2025 this number will reach 14%. Desalination is mainly performed through reverse osmosis (RO) or distillation, which are both energy-intensive processes. Unfortunately, this high energy consumption makes desalination expensive and might result in high carbon emissions depending on the energy source. Wave-driven desalination plants, which use energy harvested from ocean waves to power RO systems, are a potential solution to this problem. However, significant design constraints and energy losses arising from coupling wave energy harvesting and RO processes need to be addressed, namely 1) that pressure pulsations generated by the wave energy harvesting process must not exceed levels appropriate for the RO system components and 2) that the operating pressure of the wave energy harvesting process is constrained to the limits of the RO process.

To overcome these challenges researchers at the University of Minnesota have developed a new fluid power circuit configuration that uses a hydraulic switch-mode power transformer (SMPT) with an electrical generator. In this new configuration, the SMPT uses the inertia of a hydraulic motor driven electric generator and switching of the hydraulic motor inlet between high and low-pressure sources to decrease the pressure at which power is transmitted to the RO process from the levels used in the wave energy harvesting process. This novel technology decouples the operating pressures of the wave energy harvesting and RO processes, allowing the wave energy harvesting process to operate at higher pressures, improving the power density and enabling a significant reduction in component sizes (e.g. a 77% reduction in displacement of the wave energy converter-driven pump). This technology can potentially lead to more sustainable and cost efficient desalination plants. This novel technology is particularly relevant for establishing desalination plants in vulnerable coastal communities, which have experienced persistent water shortages and have limited power supply. Besides wave-driven desalination plants this technology can be used to improve power density, decrease power consumption, and improve controllability of RO systems in water and wastewater treatment plants, and general fluid power circuit applications such as off highway equipment.

Phase of Development

TRL: 2-3
Proof of concept using mathematical models has been performed

Desired Partnerships

This technology is now available for:
  • License
  • Sponsored research
  • Co-development

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Licensing Terms

MN-IP Try and Buy
Center for Compact and Efficient Fluid Power (CCEFP) Try and Buy – Available to CCEFP member companies
  • Trial period is up to 12 months
  • Trial fee is $0; In place of Try fee, a business plan for the Try period is required
  • No US patent fees during Try period1
  • In place of a conversion fee, a post-Try period business plan is required2
  • First $1M cumulative sales are royalty-free
  • Sublicense freely
  • Royalty rate: 2% of Net Sales
  • Patent(s) expenses paid by licensee
  • Qualified startups: 5% of equity of startup is allocated to University at formation3
  • Transfer fee for transferring license to a third party - $25,000
Please contact us for detailed term sheet for a Try & Buy agreement as well as guidelines for Try1 and post-Try period2 business plans as well as qualified startups3

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