A method of operating a dual reverse osmosis/pressure retarded osmosis plant, including when electricity costs less than a first predetermined price, moderate salinity water is pumped into the first portion of a pressure vessel having first and second portions separated by a water permeable/salt impermeable osmotic membrane to yield desalinated permeate in the second portion and brine in the first portion. Further, when electricity costs greater than the first predetermined price, low salinity water is pumped into the second portion and brine is pumped into the first portion to yield pressurized moderate salinity water in the second portion which is run through an energy recovery device to generate electricity. The salinity of the low salinity water is lower than the salinity of the moderate salinity water, and the salinity of the moderate salinity water is lower than the salinity of the brine.

A system includes a pressure exchanger (PX). The PX is coupled to a motor that controls an operating speed of the PX. The system further includes a first pressure gauge configured to generate first pressure data indicative of a pressure of a fluid of a condenser. A first controller is to generate a first control signal based on the first pressure data. The motor of the PX is configured to adjust the operating speed of the PX based on the first control signal. The system further includes a pump. The system further includes a fluid density sensor for generating fluid density data associated with a first output fluid of the PX. A second controller is to generate a second control signal based on at least the fluid density data. The pump is to adjust an operating speed of the pump based on the second control signal.

An electrochemical compressor, including a first end plate, a second end plate, a voltage supply connected to the first end plate and second end plate, a plurality of membranes, where each membrane of the plurality of membranes has a substantially same impedance, and where each membrane of the plurality of membranes has a different thickness in a stacking direction, and a plurality of conductive bipolar plates, where the bipolar plates of the plurality of bipolar plates are arranged in contact with, and alternating in the stacking direction with, the membranes of the plurality of membranes, and where the membranes of the plurality of membranes and the bipolar plates of the plurality of bipolar plates are electrically connected in series between the first end plate and second end plate.

An acoustic wave generation unit oscillates working fluid of 35 atm or less so as to generate acoustic waves with a frequency in a range from 50 Hz or more and 500 Hz or less. A heat/acoustic wave conversion component has a partition wall of 5.0 W/mK or less between two end faces which defines a plurality of cells of 620 cells/cm.sup.2 or more and 3100 cells/cm.sup.2 or less. A heat exchanger disposed close to one end face receives heat from a first external air flowing into the heat exchanger and gives the heat to the one end face so as to flow out a cold air. Another heat exchanger disposed close to the other end face receives heat from the other end face and gives the heat to a second external air flowing into the another heat exchanger so as to flow out a warm air.

An acoustic wave generation unit oscillates working fluid of 35 atm or less so as to generate acoustic waves with a frequency in a range from 50 Hz or more and 500 Hz or less. A heat/acoustic wave conversion component has a partition wall of 5.0 W/mK or less between two end faces which defines a plurality of cells of 620 cells/cm.sup.2 or more and 3100 cells/cm.sup.2 or less. A heat exchanger disposed close to one end face receives heat from a first external air flowing into the heat exchanger and gives the heat to the one end face so as to flow out a cold air. Another heat exchanger disposed close to the other end face receives heat from the other end face and gives the heat to a second external air flowing into the another heat exchanger so as to flow out a warm air.

A fertilizer gradient energy system includes a membrane module. A membrane module may include a first section and a second section. The first and second sections may be separated by a semipermeable membrane. A load may be connected to the membrane module. The first section may be configured to receive a concentrated fertilizer solution. The second section may be configured to receive a freshwater feed solution. In embodiments, a semipermeable membrane may be configured to facilitate pressure retarded osmosis of the freshwater feed solution from the first section to the second section to increase a fluid pressure in the second section. The semipermeable membrane may include an anion exchange membrane. The membrane module may include a third section. A cation exchange membrane may separate the first and third section. Anion and cation exchange membranes may facilitate reverse electrodialysis. Methods of capturing energy via a membrane module are also disclosed.

A tesla-type turbine for converting the enthalpy of a gas volume flow into mechanical energy, a method for operating the Tesla-type turbine, and an apparatus for converting thermal energy into mechanical energy, a method for converting thermal energy into mechanical energy, and a method for converting thermal energy into electrical energy. The Tesla-type turbine has at least one disc which is positioned on an axis of rotation and is set into rotation by a gas volume flow flowing substantially tangentially, so that mechanical energy can be collected at a shaft coupled to the disc. A disc body that forms the disc has at least one cavity in which, for the purpose of cooling the disc body, a cooling medium, in particular a cooling liquid, is received or can be received.

A magnetic fluid drive device for driving a magnetic fluid having temperature sensitivity in accordance with heat reception, the magnetic fluid drive device includes: a heat receiver having a flow channel through which the magnetic fluid flows, to receive heat; a magnet member disposed outside the flow channel to generate a magnetic field; and a drive mechanism that changes a position of the magnet member with respect to the heat receiver from a first position that is adjacent to the heat receiver with the magnet member applying the magnetic field to the magnetic fluid in the flow channel.

Disclosed herein are energy harvesting devices and methods of making and use thereof. The energy harvesting devices can efficiently harvest energy for motions at a frequency of 5 Hz or less.

A fluid system includes a membrane module including a first section and a second section that are separated by a semipermeable membrane, a feed pump connected to the first section, a draw pump connected to the second section, a load connected to the second section, a flush valve, and an electronic control unit (ECU) configured to control one or more of the feed pump, the draw pump, the flush valve, and the load. The ECU may be configured to control the feed pump, the draw pump, the flush valve, and/or the load according based on or according to net power generation.