Osmotic Heat Engine for Energy Production from Low Temperature Geothermal Resources Geothermal Project

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Last modified on July 22, 2011.

Project Title Osmotic Heat Engine for Energy Production from Low Temperature Geothermal Resources
Project Type / Topic 1 Recovery Act: Geothermal Technologies Program
Project Type / Topic 2 Geothermal Energy Production from Low Temperature Resources, Coproduced Fluids from Oil and Gas Wells, and Geopressured Resources
Project Type / Topic 3 Low Temperature Resources
Project Description Oasys (Osmotic Application Systems) is developing a transformative Engineered Osmosis (EO) technology that employs osmotic potential energy as a mechanism for electricity production through low temperature geothermal resource capture. The osmotic heat engine (OHE) is a closed cycle pressure retarded osmosis (PRO) system capitalizing on low temperature heat to recycle an engineered osmotic draw solute. The sole input to this closed loop system is waste heat (40C-150C); the only output is electricity from hydropower turbine. Low temperature geothermal resources are abundant, and capturing this heat as osmotic potential energy will support cost-effective, efficient, and environmentally benign power generation. The OHE is also useful for capturing the waste heat from high temperature geothermal recovery processes (e.g. flash processes), thereby improving the energy recovery and reducing the cooling costs of existing high-grade geothermal plants.

The OHE captures energy by separating a dilute solution of salts into concentrated brine and deionized freshwater components using low temperature (40-150C) geothermal heat, or the rejected heat from high temperature geothermal recovery systems. These saline and freshwater solutions store energy as the difference in their chemical energy potentials, or salinities. This captured osmotic potential is converted into electrical power using the pressure retarded osmosis (PRO) process. In PRO, freshwater flows across a semi-permeable membrane into a pressurized saline draw solution. The increased volume produces excess pressure that is dissipated though a hydropower turbine to produce electricity. In this way, PRO converts osmotic potential to hydraulic potential and finally to electricity. The depressurized and diluted draw solution is regenerated using low temperature (40-150C) geothermal heat, enabling continuous operation of the OHE.

State California
Objectives Design, construct, and test the performance of an osmotic heat engine (OHE) for low temperature heat recovery.
Awardees (Company / Institution) Oasys Water
Awardee Website http://www.oasyswater.com/
Partner 1 AltaRock

Funding Opportunity Announcement DE-FOA-0000109
DOE Funding Level (total award amount) $910,997.00
Awardee Cost Share $911,000.00
Total Project Cost $1,821,997.00

Principal Investigator(s) Robert McGinnis

Targets / Milestones Oasys presently holds patents on the NH3-CO2 draw solute, application of the draw solute in forward osmosis desalination and water treatment systems, and the OHE system. Oasys is successfully operating a lab scale forward osmosis pilot plant utilizing the engineered osmosis platform and is preparing for the construction of an industrial scale water treatment pilot plant in January 2010. Much of the initial work on forward osmosis design, including draw solute optimization, membrane research, and pilot plant construction are directly transferable to the OHE system.

Location of Project Geysers, CA, Cobb, CA

Impacts Technology based upon existing water desalinization efforts. Innovative, early stage technology could be high impact-If successful, there could be widespread application.
Funding Source American Recovery and Reinvestment Act of 2009
References EERE Geothermal Technologies Programs[1]


  1. EERE Geothermal Technologies Programs