Micro-Hydro Scroll Turbine Energy Recovery Device

Economic security and human well being are intrinsically linked to the availability of clean water. Sophisticated potable water recovery techniques, specifically saltwater reverse osmosis (SWRO), can mitigate inaccessibility to water resources in island, rural, and disaster-affected communities. Since the 1970s, energy recovery devices (ERDs) have been instrumental in reducing the specific energy consumption of SWRO systems, dropping energy consumption from 8 kWh to 2.5 kWh per cubic meter of potable water produced. While available to large scale (over 500 m3/ day of potable water production) SWRO facilities, such efficiencies have not translated to small scale systems. Therefore, higher energy demands make decentralized access to SWRO prohibitively expensive in areas where clean water is needed most. To support distributed SWRO adoption in remote communities where larger-scale desalination plants are not feasible, this SBIR proposes the development of a micro-hydro scroll turbine (MHST) ERD. Highly reliable and compact, the MHST is unique in that it efficiently recovers the energy from SWRO brine streams at low-flow, high-pressure small scale conditions. The MHST will target the following design points: Variable feed flow at 6.8 - 11 m3/day, operate at 55,000 ppm saltwater, fabricated from corrosion-resistant stainless steel, titanium, or other SW resistant materials, operate at feed pressures from 0 to 1,500 psi, recover at least 70% of the energy from the waste brine stream, the entire system, including reverse osmosis plant, will weight under 80 lbs, recover up to 3 kWh of power given energy metrics of 15-20 watt-hours/gallon during operation. The goal of the proposed Phase I effort is to design, fabricate and test a prototype MHST in both the bellows and high nitrogen stainless steel bearings configuration on high concentrated seawater (up to 55,000 ppm salt). The effort will answer several questions to determine the feasibility of the MHST. A successful development of the MHST will bring the benefits of municipal SWRO to remote and rural communities via affordable and scalable scroll-based ERD. While there are less than 100 small scale SWRO installations in the US, the energy savings made possible by an MHST ERD would lower economic barriers to entry and encourage significant investment in remote and rural desalination in line with DOE Water Security Grand Challenge goals.