Salinity differential energy

The salinity differential energy can be utilized to generate the electricity. Its main method is to converse the chemical potential differential energy between seawater with different salinity degree into the potential energy of water, and then to utilize the turbine to generate the electricity. The main method can be expressed as infiltration pressure type, steam pressure type and mechanic-chemistry type, among which the infiltration pressure type has been taken as priority.

One layer of semi-infiltrated membrane will be placed between seawater with different salinity degree. One pressure grads will be produced through the membrane, forcing that water will infiltrate from one side with lower salinity degree to another side with higher salinity degree. Seawater with higher salinity degree will be diluted until the balance of the salinity degree in the membrane. Such pressure is called the infiltration pressure, which has related to the salinity content degree in seawater and temperature. Two kind of infiltration pressure energy conversion method will be introduced as the followings:

a)        Water Pressure Tower Infiltration Pressure System

The water pressure tower infiltration pressure system mainly comprises of water pressure tower, semi-infiltrated membrane, seawater pump, and turbine-generator sets. The water pressure tower is separated to fresh water by the semi-infiltrated membrane, while the tower is connected to seawater by the pump. The system working process is as follows: seawater pump discharges seawater to the water pressure tower. At the same time, functioned by the infiltration pressure, fresh water will infiltrate to the water pressure tower by the semi infiltration membrane, resulting in the rising of water level in the water pressure tower. When the water level in the tower increasing to a certain height, water will be overflow from the water channel in the top of the tower to propel the rotating of turbine and drive to generate the electricity.

In order to keep seawater in the water pressure tower with a certain salinity content degree, seawater is continuously pumped to the tower by seawater pump in order to realize the smooth operation. Deducting the power loss of seawater pump, the total efficiency of the system is about 20%.

b)        Mighty Infiltration Pressure System

The energy conversion method for mighty system is to built up two dam between the river and sea which are called front dam and back dam respectively, and to dig a reservoir between the two dam and in 200m below the sea level.

Turbine generator sets will be installed in the front dam to connect the river and the reservoir, while semi-infiltrated membrane equipment will be installed in the bottom of the back dam to connect the reservoir and seawater.

The system working process is as follows: when the river water is flowing to the reservoir through the turbine, it will push forward the rotating of turbine and drive the generator for electricity. At the same time, the water in the reservoir flows to the sea through semi-infiltrated membrane to keep the water head between the reservoir and the river. The water head theoretically can reach 240m. But it will be smaller in reality so as to keep the fresh water directly discharge into the sea through the semi-infiltrated membrane which only infiltrates water instead of salinity.

Furthermore, only the membrane is flushed uninterruptedly by large amount of seawater, can the fresh water infiltrated through the membrane be taken away to keep the salinity content degree of the water in the seawater side of membrane and make the generation continuously.

The key technology of salinity differential energy power generation system for infiltration pressure type is the technology of membrane, and the fluid exchange technology between the membrane and interface of seawater.