Solar Desalination

1
Solar Desalination
The University of Dayton MEE 499 Renewable
Energy Systems April 26, 2000 Ben Kelpin
2
Overview

• Why do we need Solar Water Desalination?
• What is Solar Water Desalination?
• Components of Solar Desalination
• The process of converting salt water to fresh
  water
• Specifications of Desalination plants
• Desalination using Membrane Distillation
• Where in the world is this used?
• Conclusions

3
Why Solar Water Desalination?

• Only 2.5 of the water on earth is fresh water
• Also in recent years there has been shortages of
  water in urban areas

4
Desalination Setup
5
Desalination Setup
6
Principles

• A pump pumps raw water into a pre-reservoir. A
  float switch is the controller of the pump.
• The control system leads the raw water to the
  distillation collector 'Flatmodel Rosendahl'
• The glass covering is 2.6 mm thick. Solar energy
  radiation penetrates the glass and is transformed
  into thermal energy on the absorbing soakage
  sheet.

7
Principles

• The raw water supply is distributed through the
  jet tube and the wicks in the soakage shield. In
  the distillation reservoir the raw water is led
  through a soakage filter and is heated up to
  almost 100C. About 50-70 is evaporated and will
  be condensed again. 30-50 remain as sewage
  water.

8
Principles

• The condensation is pure water. All harmful
  agents and minerals stay in the remaining raw
  water and will be flushed out of the collector
  along with the sewage water.
• The condensate runs into the collecting channel.
  It drips from a trickling filter into the lower
  condensate channel.

9
Principles

• The product is pure water and now can be used for
  drinking water and industrial purposes.
• The sewage water can be used for plant irrigation
  with higher tolerance for salt

10
Specifications

• Plants range from 20 112,000 (acre-foot/yr)
• The energy use ranges from 2,500 29,500
  KWh/acre-foot
• Most seawater plants in California produce water
  in the range of 1,000 to 2,000 per acre-foot
• 1 acre-foot 326,000 gallons
• This is equal to the amount of water two or three
  households would consume in one year

11
Desalination using Membrane Distillation

• Membrane distillation uses a special membrane to
  bring out the water vapor generated from
  collected seawater, collecting it as freshwater
• The special membrane is a porous hydrophobic
  membrane which allows water vapor to pass
  through, but not drops of water

12
Membrane Distillation

• Hot seawater passed through one side of membrane
• Water vapor passes through membrane
• Water vapor cooled by cool water
• Results in water drops forming into freshwater

13
Membrane Distillation
14
Features of Membrane Distillation

• System passes cool seawater and seawater heated
  by solar energy through the sides of the membrane
  to obtain freshwater
• Water only needs to be 50 - 60C
• Membrane Distillation has little or no
  maintenance because of simple, replaceable parts

15
Geographical Areas

• Desalinated water is used as a main source of
  supply water in many areas of the Caribbean,
  North Africa, and the Middle East.
• The use of desalination technologies is rapidly
  increasing in the southeastern USA and in
  California.

16
References

• Takenaka Corporation
• www.takenaka.com
• California Costal Commission
• Seawater desalination in California
• Principles of Solar Water Desalination
• www.pege.org (planetary engineering group earth)

17
Questions/Comments