The Dual Work Exchanger Energy Recovery (DWEER) is an energy recovery

Energy recovery

Energy recovery includes any technique or method of minimizing the input of energy to an overall system by the exchange of energy from one sub-system of the overall system with another...

 device. In the 1990s developed by DWEER Bermuda and licensed by Calder AG for use in the Caribbean

Caribbean

The Caribbean is a crescent-shaped group of islands more than 2,000 miles long separating the Gulf of Mexico and the Caribbean Sea, to the west and south, from the Atlantic Ocean, to the east and north...

. Seawater reverse osmosis

Reverse osmosis

Reverse osmosis is a membrane technical filtration method that removes many types of large molecules and ions from solutions by applying pressure to the solution when it is on one side of a selective membrane. The result is that the solute is retained on the pressurized side of the membrane and...

 (SWRO) needs high pressure and some of the reject stream can be reused by using this device. According to Calder AG, 97% of the energy in the reject stream is recovered.

The DWEER system uses a piston

Piston

A piston is a component of reciprocating engines, reciprocating pumps, gas compressors and pneumatic cylinders, among other similar mechanisms. It is the moving component that is contained by a cylinder and is made gas-tight by piston rings. In an engine, its purpose is to transfer force from...

 doublechamber reciprocating hydraulically driven pump, and a patented valve

Valve

A valve is a device that regulates, directs or controls the flow of a fluid by opening, closing, or partially obstructing various passageways. Valves are technically pipe fittings, but are usually discussed as a separate category...

 system in a high pressure batch process with large pressure vessels, similar to a locomotive

Locomotive

A locomotive is a railway vehicle that provides the motive power for a train. The word originates from the Latin loco – "from a place", ablative of locus, "place" + Medieval Latin motivus, "causing motion", and is a shortened form of the term locomotive engine, first used in the early 19th...

, to capture and transfer the energy lost in the membrane reject stream. Its advantage is its high efficiency rate, but it suffers from complex and large mechanical components which are susceptible to corrosion from seawater due to its metal composition.