Masters Thesis: Wind Driven Reverse Osmosis Desalination for Small Scale Stand-Alone ...

181 Pages·2011·7.63 MB·English

Master of Science Thesis
Wind Driven Reverse
Osmosis Desalination for
Small Scale Stand-Alone
Applications
Evaluation of system configurations and selection of an
optimal configuration for Somaliland by means of a
SIMULINK model
C. Generaal B.Sc.
February 25, 2011

Wind Driven Reverse Osmosis
Desalination for Small Scale Stand-Alone
Applications
Evaluation of system configurations and selection of an optimal
configuration for Somaliland by means of a SIMULINK model
M.Sc. Thesis
For obtaining the degree of Master of Science in Aerospace
Engineering at Delft University of Technology
C. Generaal B.Sc.
February 25, 2011
Faculty of Aerospace Engineering (cid:1) Delft University of Technology
Delft University of Technology
Copyright ⃝c C. Generaal B.Sc.
All rights reserved.
Delft University Of Technology
Department Of
Wind Energy
The undersigned hereby certify that they have read and recommend to the Faculty of Aerospace
Engineering for acceptance a thesis entitled “Wind Driven Reverse Osmosis Desalination
for Small Scale Stand-Alone Applications” by C. Generaal B.Sc. in partial fulfillment of
the requirements for the degree of Master of Science.
Dated: February 25, 2011
Professor:
prof.dr. G.J.W. van Bussel
Supervisors:
ir. H.F. Veldkamp
dr. ir. S.G.J. Heijman

"If we could ever competitively, at a cheap rate, get fresh water
from seawater, that would be in the long term interests of
humanity and would dwarf any other scientific accomplishment."
John F. Kennedy, April, 1961
vi
Abstract
The need for a sustainable water supply is high in many regions worldwide. The coastal city
Berbera in Somaliland is one of those places where clean drinking water is not part of everyday
life. With wind and saline water being freely available, wind driven reverse osmosis desalination
cansolvetheproblem. Existingsolutionsonwinddrivenreverseosmosisdesalinationarehowever
limited. It is difficult to select the best configuration for a specific site. To deal with this issue
the Wind2Water model is developed.
The Wind2Water SIMULINK model is a tool to select an optimal wind driven reverse osmosis
system for a specific site. The model consists of four main blocks; the windturbine block, the
transmission or coupling block, the pump block and the reverse osmosis array block. Two main
configurations exist in the model; the mechanical coupling with gearbox and different gearbox
ratios and the electrical coupling with battery. The Wind2Water model is organized in such a
way that it is easy to implement additional components (such as a new wind turbine or pump).
The assumptions that were made for the creation of the mechanical Wind2Water model were
validatedbymeansoftheexperimentaldatafromtheprototypeofDelftUniversityofTechnology
built on Curaçao. The validation focussed on the permeate outflow around mean wind speed.
With this focus the model matched the experimental results, proving that the assumptions were
valid. The electrical Wind2Water model was validated by means of the prototype of Hatenboer
Water. The efficiencies of the components in the electrical configuration were varied to find an
electrical coupling that best matched the experimental results. This configuration was found
and the characteristics of this configuration were used for the evaluation of other electrical
configurations.
With the Wind2Water model brackish water configurations and sea water configurations were
analyzed for regions with a mean wind speed of 5.9 m/s and 7 m/s. The evaluated configuration
types were multi-bladed and three-bladed wind turbines with a mechanical coupling, and three
bladed wind turbines with an electrical coupling. The effect of different pump sizes and, for the
mechanical systems, transmission ratios were also taken into account. The water output for each
configuration was estimated and from that the water cost could be defined. The total score of
each configuration was based on the weighted score of the most important design criteria, being
cost, maintenance, life and reliability.
viii Abstract
For brackish water desalination the optimal configuration type (based on the four design criteria)
is the mechanically coupled multi-bladed windmill. By looking only at the water cost the
multi-bladed mechanical configuration is the best option as well. At higher mean wind speed
three bladed mechanical configurations and the electrical configurations can however become cost
competitive. The best configuration from a water output point of view depends on the mean
wind speed. At high mean wind speeds the three bladed wind turbines, either mechanically or
electrically coupled, are favorable. At low mean wind speeds a well chosen mechanical coupling
with a multi-bladed wind turbine is preferable.
Also for sea water desalination the mechanical configuration with a multi-bladed windmill is the
solution with the highest weighted score. In terms of water output the configurations with the
mechanically coupled three bladed wind turbines are outperforming the others. Because of the
higher system cost the water cost of these configurations is however similar to the water cost of
the multi-bladed configurations. The three bladed mechanical configurations have a customized
mechanical coupling. This results in lower scores on maintenance, life and reliability compared to
the three bladed mechanical configurations with an off-the-shelf coupling.
For brackish water and for sea water desalination, the five configurations with the highest
weighted score were selected. These configurations were analyzed with the monthly wind
conditions of Berbera, Somaliland. For both brackish water and for sea water desalination the
mechanically coupled multi-bladed configuration was found to be the optimal solution. The
electrical configurations showed a higher average water output and a water cost score similar to
the multi-bladed configuration for brackish water desalination and for sea water desalination this
score was even higher than for the multi-bladed configuration. For application in a developing
country the score on the ease of maintenance for the electrical system was however assumed to
be lower than for the multi-bladed mechanical configuration, resulting in a slightly lower overall
score for the electrical configuration.
The mean wind speed in Somaliland varies highly per month and even per day. Introducing
a multi-bladed mechanical system that is able to switch between different transmission ratios
during the year promises to be the best solution for both brackish water desalination as well as
for sea water desalination in Somaliland. The variable transmission will allow for more water
production in the low wind speed months, resulting in a higher average daily water output. With
this higher water output the water cost will decrease and the weighted score of the multi-bladed
mechanical configuration will increase.