METHODS AND SYSTEMS OF SEA WATER DESALINATION USING
SOLAR AND BIOMASS ENERGY
FIELD OF THE INVENTION
Embodiments of the present invention in general relate to sea water
desalination and in particular relates to methods and systems of the sea
water desalination using the solar and biomass energy.
BACKGROUND OF THE INVENTION
Potable and industrial water supply is an essential parameter for measuring
economic progress and well-being, and is the unique energy form that
enables technical innovation and productivity growth. However, the important
achievements of water supply remain elusive in many parts of the world
because population is growing faster than the current rate of water supply
can accommodate.
Environmental, economic and strategic reasons are behind the rapid impulse
in the deployment of renewable energy sources that is taking place around
the world. In addition to overcoming economic and commercial barriers,
meeting the ambitious objectives set by most countries in this field will require
the development of novel technologies capable of maximising the energy
potential of different renewable sources at an acceptable cost.
The use of renewable sources such as solar radiation and biomass for water
generation is growing rapidly, particularly in areas of the globe where these
resources are plentiful. However, solar energy plants necessarily suffer from
the intermittency of day/night cycles and also from reduced irradiation periods
(winter, cloudy days, short transients). To overcome the intermittency of
day/night cycles and also from reduced irradiation periods problem, research
is being conducted to develop efficient heat storage systems (molten salts,
concrete, latent heat) and other energy storage alternatives (pumped
hydroelectricity, hydrogen, etc). However, these technologies have been
reported to be expensive and/or not sufficiently proven.
In contrast, the biomass power plants have to confront the logistic problems
associated with the continuous supply of very large amounts of a relatively
scarce and seasonal fuel. Although the biomass combustion is a mature
technology with a large number of power plants in operation worldwide,
however, the energy efficiency of this technology is limited and the operating
and investment costs are high, resulting in low financial returns.
Therefore there is a need for a system that may provide the solution to the
above mentioned limitations of the solar and biomass plants and thereby
maximising the energy potential of these resources, increasing process
efficiency, providing greater security of supply and reducing the overall costs.
A shortage of fresh water is another very important problem that is
continuously increasing, due to population growth and changes in weather
conditions, and affects many countries in the world. Many countries usually
have abundant seawater resources and a good level of solar radiation, which
could be used to produce drinking water from seawater. Although everybody
recognizes the strong potential of solar thermal energy to seawater
desalination, the process is not yet developed at commercial level. The main
reason for this is that the existing technology, although already demonstrated
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as technically feasible, cannot presently compete, on produced water cost
basis, with conventional distillation and reverse osmosis technologies.
Nevertheless, it is also recognized that there is still important room to
improve desalination systems based on solar thermal energy.
Since sea water desalination is key to supplying the world's population with
drinking water, but it can only be sustainable and thus socially and
environmentally responsible, if that desalination is based on renewable
energies.
Therefore there is a need to address the above mentioned problems and
provide methods and systems to desalination of water using renewable
energies.
SUMMARY OF THE INVENTION
According to an embodiment of the present invention there is provided a
method and system of the sea water desalination using the solar and
biomass energy. A hybrid system using the solar and biomass energy is used
in order to maximize the energy potential of these resources, increasing
process efficiency, providing greater security of supply and reducing overall
costs.
According to an embodiment of the present invention there, is provided a
method and system of the sea water desalination using the solar and
biomass energy wherein the system is an integrated system wherein power/
renewable energy and potable water/ desalinated water is
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produced/generated using combination of solar and biomass renewable
energy sources.
According to an embodiment of the present invention there is provided a
method and system of the sea water desalination using the solar and
biomass energy where the hybrid system have larger capacities than
standard biomass combustion plants and therefore it implies that higher
energy efficiencies and a reduced risk associated with biomass supply is
achieved.
According to an embodiment of the present invention there is provided a
method and system of the sea water desalination using the solar and
biomass energy wherein the hybrid system using the concentrated solar -
biomass combustion hybrid technology relies on the effective integration of a
solar collector into a biomass boiler. The combination of the solar collector
into the biomass boiler benefits from increased overall energy efficiency of
the hybrid system, reduced investment per unit of power capacity (compared
to CSP with molten salts heat storage), and longer operating hours (24 hours
a day without the need for relevant heat storage).
According to embodiment of the present invention there is provided a method
and system of the sea water desalination using the solar and biomass energy
wherein the hybrid system comprises a solar-biomass power plant which is
intended to operate as a hybrid plant such that on a bright day, 50% of the
plant thermal energy input comes from solar corresponding to an insolation
level of 800 W/m2 and the remaining 50% comes from biomass so as to
generate power and desalinated water as the output.
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According to an embodiment of the present invention there is provided a
method and a system of the sea water desalination using the solar and
biomass energy. The seawater is desalinated using a low pressure saturated
steam which act as thermal source for a multiple effect distillation unit. The
saturated steam required for the desalination of the sea water is supplied by
a solar steam generator supported by a biomass boiler. The solar steam
generator produces high pressure steam which is depressurized and passed
to the thermo vapour compressor as motive steam. The motive steam
compresses the entrained steam from the last effect of the multiple effect
distillation unit. The low pressure saturated steam coming out of thermo
vapour compressor is used to then drive the multiple effect distillation unit to
produce the desalinated water.
According to an embodiment of the present invention there is provided a
method and a system of the sea water desalination using the solar and
biomass energy wherein during the process of the desalination, the sea water
is sprayed over one or more tubes and the steam gets condensed. When the
steam gets condensed the latent heat of the steam is then transferred to the
sea water and the sea water gets evaporated. The evaporated steam will
then enter into a next effect of the multiple effect distillation unit and serves
as a source steam to evaporate the sea water sprayed in the effect of the
multiple effect distillation unit. This process continues in subsequent effects
of the multiple effect distillation unit to get sufficient quantity of distillate. In
the last effect of the multiple effect distillation unit a portion of the evaporated
steam is taken back to the first effect of the multiple effect distillation unit by
compressing it in a thermo vapor compressor using the motive steam
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supplied by the solar steam generator. The intermittency in solar energy is
managed by a biomass boiler generating saturated steam.
According to an embodiment of the present invention there is provided a
method and a system of the sea water desalination using the solar and
biomass energy wherein the hybrid system of desalination can be installed in
arid coastal areas having sufficient solar radiation and biomass resources so
that it can serve both industrial and portable water needs of the region.
According to an embodiment of the present invention there is provided a
method and a system of the sea water desalination using the solar and
biomass energy wherein the hybrid system comprises steam generation unit
and multiple effect distillation-thermo vapour compressor unit. The steam
generation unit comprises of solar field and biomass boiler. The solar field
includes fresnel reflectors made of mirrors with specific curvatures. The
mirrors which are mounted on the trackers will be configured to reflect the
sunlight onto receiver tubes located above these mirrors. These fresnel
reflectors provide direct steam generation which can be input into the
biomass boiler. The integration would be effected through the supply of
saturated steam or saturated steam-water mix from the solar field to the
steam drum of biomass boiler. During night time, and at day times when solar
insolation is not available, the biomass boiler will be operated on biomass
fuel at full load to desalinated water. The biomass boiler will be operated in
the day time depending upon the heat from the solar heat generator, which in
turn depends upon the solar insolation available in the area selected.
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According to an embodiment of the present invention there is provided a
method and a system of the sea water desalination using the solar and
biomass energy wherein the hybrid system comprises steam generation unit
and multiple effect distillation-thermo vapour compressor unit. The steam
generation unit comprises of solar field and biomass boiler. Solar field
includes Linear Fresnel Reflector solar energy collector, steam drum and
steam accumulator. The solar energy is collected using the solar grade
mirrors and concentrated on to a receiver which encompasses absorber
tubes containing water. This water when circulated will absorb the solar
energy and form high pressure saturated steam. This steam is passed to the
steam drum where saturated steam is separated from saturated liquid. The
water in the steam drum is fed back to the LFR field by recirculation pump
and the saturated steam is taken to the steam accumulator. Saturated steam
enters the accumulator at high pressure. Steam is withdrawn from the
accumulator at low pressure. This low pressure steam from the accumulator
act as the motive steam for the TVC which compresses the entrainment
vapour coming from the last effect of multiple effect distillation. Thus the low
pressure saturated steam at thermo vapour compressor outlet is fed to the
multiple effect distillation. The steam entering first effect condenses by giving
up its heat to the sea water sprayed through the nozzles. Partial amount of
sea water is converted into vapour and is passed to the next effect where it
acts as the thermal source for heating the sea water and the process is
continued in all the effects. The steam produced in the last effect is partly
diverted to thermo vapour compressor and the remaining is fed to the final
condenser to preheat the sea water sprayed in each effect. The condensed
distillate water is siphoned to the successive effects and collected in the final
condenser which is pumped to the distillate water tank with the help of
distillate pump. The brine from each effect is also siphoned to the next effect
and finally pumped out by the brine pump. It is evident that solar field can
supply steam only during day time. In order to achieve round the clock
operation the steam generation unit is provided with a biomass boiler which
uses wood as the fuel. The biomass boiler is integrated with the solar field to
supply steam when solar field fails to meet the requirement.
According to an embodiment of the present invention there is provided a
method and a system of the sea water desalination using the solar and
biomass energy wherein the hybrid system using the solar and biomass
energy achieves the efficient utilization of the Balance of Plant (B O P). A
standalone solar power plant will be having lower cycle efficiency than
biomass operated plant due to lower temperature achieved by solar steam
generators. The biomass operated power plant suffers the non-availability of
the biomass and seasonal change in calorific value in the year round
operation. The solar-biomass hybrid system forms a solution of both the
problems associated with each one as separate unit.
According to an embodiment of the present invention there is provided a
method and a system of the sea water desalination using the solar and
biomass energy wherein the optimum method of integration is done by
keeping the outlet dryness of the solar steam generator close to 80 %, as per
two phase flow regime map so as to maintain the stability of the flow. As.the
solar insolation goes up from 300 W/m2 to 800 W/m2 for constant mass flow
rate the dryness also varies.
According to an embodiment of the present invention there is provided a
method and a system of the sea water desalination using the solar and
biomass energy wherein in the hybrid system the solar field is to be
integrated to the down comer of the drum, so that both the steam generating
unit will share a single drum. The inlet to the solar field will be taken from
down comer of the steam drum. From the drum the recirculation pump will
drive the liquid through the solar field. The recirculation pump will try to
overcome the frictional drop across the solar field, which will be varying with
respect to the insolation.
According to an embodiment of the present invention there is provided a
method and a system of the sea water desalination using the solar and
biomass energy wherein in the hybrid system the pressure drop across the
solar field is estimated from various correlations, out of which freidel
correlation found to be close to experimental results. In order to have
sufficient control over the instability, each section of the solar loop is
individually controlled so that sufficient flow rate through each loop is
obtained
According to an embodiment of the present invention there is provided a
method and a system of the sea water desalination using the solar and
biomass energy wherein the MED unit which replaces the condenser takes
the saline water and gives out distillate water at a Gross Output Ratio (GOR)
of 10. The makeup water required for the plant will be taken from the
distillate.
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According to an embodiment of the present invention there is provided a
method and a system of the sea water desalination using the solar and
biomass energy wherein the seawater having a temperature of 30 deg C at
36 000 ppm is mixed with of cooled sea water from the cooling tower. This
seawater is taken to the final condenser of MED.
According to an embodiment of the present invention there is provided a
method and a system of the sea water desalination using the solar and
biomass energy wherein the seawater having a concentration of 36 000 ppm
and a temperature of 37 deg C entering the MED, will be desalinated by
multiple effect distillation to produce nearly pure water with total dissolved
solids as low as only 2 ppm.
According to an embodiment of the present invention there is provided a
method and a system of the sea water desalination using the solar and
biomass energy wherein the brine will be produced at a temperature of 41
deg C and 61 000 ppm total dissolved solids. The brine is diluted and cooled
by fresh seawater at a point close to the ocean. This point is kept close to the
ocean and away from the plant so as to minimize pumping power. The
rejected seawater being returned to the ocean will have a temperature of 34
deg C (or 4 deg C above the seawater) and a salinity 1.25 times that of
seawater.
These and further aspects which will be apparent to the expert of the art are
attained by an adjustable applicator in accordance with the main claim.
BRIEF DESCRIPTION OF THE DRAWINGS
So that the manner in which the above recited features of the present
invention can be understood in detail, a more particular description of the
invention, briefly summarized above, may be had by reference to
embodiments, some of which are illustrated in the appended drawings. It is to
be noted, however, that the appended drawings illustrate only typical
embodiments of this invention and are therefore not to be considered limiting
of its scope, for the invention may admit to other equally effective
embodiments.
Figure 1 illustrates a perspective view of a hybrid system for sea water
desalination using the solar and biomass energy according to an embodiment
of the present invention.
To facilitate understanding, identical reference numerals have been used,
where possible, to designate identical elements that are common to the
figures. It is to be noted, however, that the appended drawings illustrate only
typical embodiments of this invention and are therefore not to be considered
limiting of its scope, for the invention may admit to other equally effective
embodiments.
DETAILED DESCRIPTION OF THE DRAWINGS
Figure 1 illustrates a perspective view of a hybrid system 100 for sea water
desalination using the solar and biomass energy according to an embodiment
of the present invention. In an embodiment, the hybrid system 100 comprises
a steam generation unit 102 and a multiple effect distillation unit 104, and a
thermo vapour compressor unit 104. The steam generation unit 102
comprises a solar field 108 and a biomass boiler 110. The solar field 108
includes a linear fresnel reflector solar energy collector 112, a steam drum
114, and a steam accumulator 116.
A feed water tank 118 is provided for storing the water. A feed pump 120
pumps the water from the feed water tank 118 and then circulates on to a
receiver which encompasses absorber tubes. The solar energy is then
collected using the solar grade mirrors and concentrated on to the receiver
which encompasses the absorber tubes containing water. This water when
circulated will absorb the solar energy and form high pressure saturated
steam. This steam is passed to the steam drum 114 where saturated steam
is separated from saturated liquid.
The water in the steam drum 114 is fed back to the linear fresnel reflector
solar energy collector 112 field by circulation pump 122 and the saturated
steam is taken to the steam accumulator 116. The saturated steam enters
the steam accumulator 116 at high pressure. The steam is then withdrawn
from the steam accumulator 116 at the low pressure.
This low pressure steam from the steam accumulator 116 act as the motive
steam for the thermo vapour compressor unit 106 which compresses the
entrainment vapour coming from the last effect of multiple effect distillation
unit 104. Thus the low pressure saturated steam at thermo vapour
compressor 106 outlet is fed to the multiple effect distillation unit 104.
The steam entering first effect condenses by giving up its heat to the sea
water sprayed through the nozzles. The partial amount of sea water is
converted into vapour and is passed to the next effect where it acts as the
thermal source for heating the sea water and the process is continued in all
the effects. The steam produced in the last effect is partly diverted to thermo
vapour compressor unit 106 and the remaining is fed to a final condenser 124
to preheat the sea water sprayed in each effect. The condensed distillate
water is siphoned to the successive effects and collected in the final
condenser 124 which is pumped to a distillate water tank 126 with the
support of a distillate pump 128. The brine from each effect is also siphoned
to the next effect and finally pumped out by a brine pump 130.
The solar field 108 can supply steam only during day time and in order to
achieve round the clock operation the steam generation unit 102 is provided
with the biomass boiler 110 which uses wood as the fuel. The biomass boiler
110 is integrated with the solar field 108 to supply steam when solar field 108
fails to meet the requirement during the non-day time.
These and further aspects which will be apparent to the expert of the art are
attained by an adjustable applicator in accordance with the main claim. While
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the foregoing is directed to embodiments of the present invention, other and
further embodiments of the invention may be devised without departing from
the basic scope thereof, and the scope thereof is determined by the claims
that follow.

What is claimed is:
1. A system for sea water desalination comprising a steam generating
unit configured to provide a continuous supply of steam to desalinate
the sea water; wherein the steam generating unit comprises a solar
field and a biomass boiler; and wherein the solar field uses solar
energy to convert water into steam; and wherein the biomass boiler is
integrated with the solar field to supply the steam in the absence of the
solar energy such that the steam generating unit provides continuous
supply of steam in the absence or presence of solar energy.
2. The system for sea water desalination of claim 1, wherein the solar
boiler comprises a linear fresnel reflector solar energy collector, a
steam drum and a steam accumulator.
3. The system for sea water desalination of claim 1, wherein the solar
energy is collected using one or more solar grade mirrors and
concentrated on to a receiver which encompasses one or more
absorber tubes containing water to convert the water into steam.
4. The system for sea water desalination of claim 3, wherein the steam is
passed into the steam drum that facilitates the separation of a
saturated steam from a saturated liquid.
5. The system for sea water desalination of claim 4, wherein the
saturated steam enters the steam accumulator at high pressure and is
withdrawn from the steam accumulator at low pressure.
6. The system for sea water desalination of claim 2 wherein the utilization
of medium pressure steam generated of the order of 5 bar is used for
sea water desalination by a multi effect distillation system integrated
with thermo vapour compressor.
7. The system for sea water desalination of claim 6 wherein an increased
solidity factor is achieved by integrating the linear fresnel reflector
based solar technology with the multi effect distillation system.
8. The system for sea water desalination of claim 1 wherein high thermal
performance of 83 kWh/m3 of desalinated water is achieved.
9. The system for sea water desalination of claim 1 wherein the solar
field supply the steam during the day time.
10. The system for sea water desalination of claim 1 wherein the biomass
boiler uses wood as its fuel, and wherein the biomass boiler is
configured to supply the steam during non-day time.