Post on 30-Oct-2014
description
Technical report
product
Solar Desalination Plant
application of
Utilizing Solar Radiation in Water Desalination
by
Desert Fish
Executive Summary
Our product is a power plant that harvests energy from Solar radiation to
utilize it in a much needed application: water desalination. It is a large scaled project
that we designed to provide fresh water for countries that have sea coasts, but lack in
natural fresh water resources.
Unlike most of the current water desalination methods, our method is eco-
friendly and emission free. Except for a slight need of electrical power, the system
fully operates on solar energy.
Our Water desalination process is similar to that of the nature, which happens
in the water cycle; saline water is heated by sun, water evaporates free of salt, clouds
condense, and finally, fresh water fall as rain. To speed up this process, we must
intensify the amount of sun rays affecting the saline water. To achieve that, we spread
a considerable amount of mirrors that focus Solar rays at a set point about 10 meters
high. At that point, a concave mirror is places to reflect and direct all sunrays
downward on a water container. Within the container, a black metal plate with
branches of wire is fixed. The plate's role is to transform most sunlight into heat, and
distribute that heat in the container. The minor need of electricity is operational,
where the mirrors are placed on electronic directors to keep in alignment with the
sun's position in the sky.
After the first phase water goes through, its vapor enter the second phase. That
is when water vapor is naturally directed to a higher chamber. The chamber is
thermally insulated. In addition, tubes of cool water in the walls of the chamber cools
it down. Thus, when the water vapor come into contact with the interior of the
chamber, it condenses to stream down as liquid water. Free of excessive unwanted
minerals, seawater is good for drinking now!
This simple process provides numerous natural and financial advantages.
Since our product doesn't burn fossil fuel, it is totally emission free. Hence, it is
environmentally friendly. Furthermore, present-day water desalination plants use huge
amounts of valuable natural gas, requiring a lot of money. With our product, that
money will no longer be necessary.
Need Statement
People try to prevent a hazardous an expected Mother Nature event that is just
starting, which is known as global warming. Global warming can be prevented in
many ways, and the main key to prevent it is to use clean energy. Nowadays, most
people depend on polluting energy sources (which comes from the burning of fossil
fuels; emitting carbon dioxide) in operating almost everything ranging from cars,
factories, houses, and other buildings. This resulted in the increase of carbon dioxide
emissions by 5.9% in 2010. This increase can be effective in many negative ways, and
people can predict how much will it increase in the coming years. That’s why
planning the future is a vital factor. The world should decrease the use of polluting
energy, and increase the use of clean energy in order to put a stop to global warming.
Water is the most vital element for life. Without water, it is impossible to
survive. Saline oceans make up to 71% of the earth’s surface1. People obtain fresh
water directly from lakes and rivers. Whereas ocean (saline) water must undergo a
process called desalination in order to be good for human consumption or crop
irrigation. Studies show that 14,451 water desalination plants around the world
produce 15.8 billion gallons of water every day. These plants require massive
amounts of energy to function, which can contaminate Earth’s atmosphere. But how
valuable would it be if water desalination plants were to function on clean energy?
What a great advantage to the environment and atmosphere that would be!
Saudi Arabia is the largest producer of desalinated water in the world. The
government pays annual subsidies at a cost of 3.2 million US dollars for water
desalination. There are 30 governmental desalination plants that are spread around the
country. These 30 plants produce over 2.98 million m3 of desalinated water per day.
About three million barrels of oil are used to power these plants every day; it is
expected that this number is going to triple in the next five years.
Another example is the Jebel Ali desalination plant located in the United Arab
Emirates, and it’s the world’s largest desalination plant. Jebel Ali plant is capable of
producing 300 million m3 of water per year. Such enormous amounts of desalinated
water require tremendous amounts of energy. Using pure, clean energy is just what
countries like Saudi Arabia, United Arab Emirates and many others need, looking at
the massive quantities of desalinated water they produce per day using energy that can
cause great harm to the environment.
25,000 people die from starvation every day. Somalia is a suitable example for
that. Due to poverty and land dryness, Somalia loses a large number of people
because of hunger, thirst, and diseases. Although Somalia is bordered with the Indian
Ocean from the east, it doesn’t have the financial abilities nor the facilities to exploit
the ocean in the right way. A large number of countries participated in donating
generous sums of money and provisions to Somalia. But the question is: why can't
Somalia consistently provide its own provisions? Should people keep on donating or
should they put a plan that will satisfy the needs of the people in Somalia? This is one
of the major problems our world faces today, and such misfortunes require immediate
solutions. As you know water is an essential component that can save the lives of
many in Somalia. Water is not only used as a hydrant for the human body but it is also
used to grow crops and create a land full of vegetation for people and animals. In such
problems, easy fresh water sources are the solution.
Looking at these problems happening in our world today, desert fish came up
with an innovative idea that can solve these problems with suitable and appropriate
solutions. We developed a water desalination plant that requires almost nothing but
sunlight to fully function. This plant is capable of supplying fresh water in an
economical and ecological friendly method. Our plan may solve present problems that
are happening in the world today but it can also solve problems in the future. Many
people talk about global warming and how effective and destructive it is, but the only
solution for that is to use clean energy that doesn't have a negative effect on Earth's
atmosphere. Sunlight is a main source of energy that hasn't been utilized completely,
but why do people tend to use other sources of energy that can negatively affect the
atmosphere for many important applications rather than using sunlight, which is
dramatically better source of energy?
Clean energy is the right path to take in order to prevent global warming. Our
innovative product can make the desalination of water a really simple, inexpensive
process, and on top of that, it functions on clean energy. Not only the desalination of
water should undergo a clean energy process but also everything we use in our daily
life.
Background Technology
Our product aims to determine how to harness solar rays as a substitute in
water desalination, and the creation of the quantities involved; such as the amount of
water, the amount of rays necessary to vaporize the water, and the total time for the
process. The Desert Fish team was unique because they gathered different technology
methods, used the methods of other well-known products, and researched in the laws
of physical science, then came up with a new, special, and innovative product that is a
solution for a worldwide problem.
First of all, with the rapid spreading of news channels and forecasts on
weather changes, it is not obscure to the world anymore that the vicinity of the
Middle-East and North of Africa are areas that receive the highest amount of solar
radiation reaching up to 2400 KW/m2(Kilowatts per Meter squared). Having this
amount of solar natural radiation is one advantage that must be exhausted properly. A
method had been functioned by constructing huge water containers in the vast deserts,
which are isolated from their surroundings using glass. This allows the sunrays to
penetrate them to heat the salty water in the containers. The water evaporates; but
over a long period of time, similar to the natural processes that form clouds. We used
the same method, but we adjusted and added enormous things on the original method
in order to intensify the sun radiation and thrive the speed of boiling the water and
evaporating in a much quicker passage of time.
To intensify the solar radiation, we install mirrors in large quantities around
the containers. These mirrors are spread along 50 to 100 meters encircling the glass
tanks, we'd like to name these: primary mirrors. Primary mirrors are set on electronic
directors that detect Sun’s position and focus its rays to another concaved mirror
placed on poles exactly above and facing the container. The Concave mirror is to
intensify the primary mirrors' rays towards the container. Inside the containers, a
black metal plate, which doesn’t reflect light, is placed in order to heat the water to its
boiling point; hence, speeding up its evaporation.
The Primary mirrors are set on electronic directors which helps them to shift
angles in order to absorb the most of the sun’s radiation in all times. We have
researched and came up with results. An example of one of our studies is: Using 150
mirrors with the size of 10m2, and the sun radiation is perpendicular on the mirrors
the estimated time of reaching the boiling point is 14-16 minutes. With our research
we also found a technological mirror that is qualified for our product and it can be
used as the Primary Mirrors, which are called Fresnel Reflectors. Fresnel reflectors
are made of many thin, flat mirror strips to concentrate sunlight onto tubes through
which working fluid is pumped. Flat mirrors allow more reflective surface in the same
amount of space as a parabolic reflector, thus capturing more of the available sunlight,
and they are much cheaper than parabolic reflectors. Fresnel reflectors can be used in
various sizes.
Why a Concave mirror? This question might wander around your mind. The
answer is simple; it is well known that concave mirrors have the shape of an umbrella.
If the sunlight that is reflected from the primary mirrors hits any spot in the mirror it
will be directly reflected to one median point in order to have extensive sun radiation.
Some criticizers may say that our product is too imaginative to be applied in
reality in addition to other alternatives which aim to the exact purpose that could be
more efficient. Well, I clearly stress my words on rejecting the criticizer's thought and
say that "Our product is the best alternative to solve this endemic problem, for many
reasons: First, our product could be applied in reality because of the existence of
products with same core idea of utilizing solar rays naturally which is applied is
Spain. Second, other products may have more efficiency than ours, but I assure you
that our product is part of the high level efficiency while using less amount of energy
and money, and that what makes our product really beneficial to the environment and
also makes it a part of the clean energy field."
Concept Details
The function of our product, Solar Desalination Plant, is to desalinate saline
water in order to produce fresh water. The structure of the plant is simple, flexible,
and expandable. That allows the technology that we innovated, Utilizing Solar
Radiation in Water Desalination, to efficiently work with ease and with clear
mechanics. All these factors benefits the facility by giving it the capability to adjust to
various water supply needs.
The design of the facility is similar to that of an auditorium. A cylinder water
container is located at the center, and arc-shaped rows of mirrors surround it. Above
the water container at the center, a sector of a big concave mirror hangs on a pole,
facing downwards at the container. However, the container and the mirrors around it
are not on the same altitude. The mirrors are raised above the surface of the container
by several meters. That allows some space to be available for building steam
chambers under the mirrors, but still higher than the container's surface. Furthermore,
both the steam chamber and the water container must be under the sea-level.
The technology by which our product operates emphasizes the efficiency of
solar radiation in producing thermal energy. It provides an effective way to harness
solar energy, convert it into thermal energy, and use that heat in an indispensable
application: water desalination.
Solar rays are collected through reflecting mirrors that are widely spread in a
sunny area. These mirrors are known as "heliostats". Heliostats have the ability to
keep reflecting sunlight toward a predetermined target. They are controlled by
computers which calculate Sun's position. Also given the heliostat's position, the
computer operate motors that rotate the heliostat to keep it in correct alignment with
the sun and the target. The target however, is not the final destination of the collected
light. Around 15-30 meters high hangs the target of the heliostats: a concave mirror
whose role is to reflect a concentrated light beam at the water container under it.
Concave mirrors focus defused light at a certain focus point due to the shape of its
curve and the angles of incoming light. Our concave mirror must be designed and
positioned so that its focus point is inside the water container. Its placement at that
height can be achieved by simply attaching it to a pole from its side. Preferably, the
height of the mirror should be adjustable; it should be attached to a slider on the pole
so that it can slide up and down.
At the focus point in the container, a sufficient amount of energy is available,
but it is in the form of light, and we need to convert it into thermal energy. As light
hits any object, part of that light goes through (as in invisible bodies), another part is
reflected back (as in visible bodies), and the remaining light transforms into heat (as
in black bodies). To transform as much heat from the light as possible, a black metal
plate is placed inside the water container. The metal plate serves for another purpose:
the distribution of heat in the container. Therefore, it must be a good heat conductor.
Copper or copper alloys (e.g., bronze, brass) are good materials to build the plate.
They are highly conductive, affordable, and less corrosive than many other metals.
Since our product is a large scaled facility with multiple operations, its
features are better expressed and understood by describing work process phases rather
than describing its physical parts. After the energy is collected, saline water goes
through two main phases in order to desalinate completely: vaporization and
condensation. In chemistry, the process of purifying liquids by vaporization and
condensation is known as distillation.
The water comes directly from the ocean through pipes. Because the container
is under the sea-level, the water naturally flows to it from the ocean without any need
of pumps. 5 tons of water fill the container, and come into contact with the metal plate
inside. The metal plate gets heated up pretty fast by the effect of the concentrated
sunlight beam on its surface. By the laws of thermodynamics, when two bodies come
into physical contact, heat transfers from the hotter (higher temperature) body to the
cooler (lower temperature) body until they reach thermal equilibrium (equal
temperatures). Therefore, heat will transfer from the hot plate to the water until they
reach thermal equilibrium. As the beam keeps on heating the plate, the water's
temperature will keep on rising. When the water reaches its boiling point (i.e. 100°C),
the continuous thermal energy will start to evaporate the saline water. Water
evaporates free of harmful minerals.
For this process to work properly, the container must be thermally insulated.
In addition, the top cover of the container must have special features to perform its job
correctly. It must be transparent (e.g., glass) so that the beam of light coming from
above goes through to reach the metal plate. It also must have a special shape so that
its center is low to be in the water close to the plate, and its edges on the edges of the
container. That prevents water vapor from blocking the light beam as it might get
between the cover of the container and the metal plate.
Note that the waste when evaporating saline water (i.e. salt) remain as residue
in the bottom of the container. Therefore, the container must have a door for daily
cleaning. Cleaning is necessary to keep the plant functioning properly.
After the water becomes mostly vaporized, valves at the top the container
electronically open. The valves lead to the steam chamber placed under the heliostats.
Because it is higher than the container, as soon as the valves open, water vapor
naturally flows into the chamber. The chamber's walls are made of thin sheets of
copper or copper alloys because it's highly conductive and less corrosive than other
metals. When water vapor comes into contact with the cooler walls, it condenses and
transforms back to liquid water. Water leak on the walls to collect at the bottom of the
chamber. The chamber's floor incline downwards to its edge, and that's where a set of
valves takes the fresh water outside. This is the end of the desalination process.
According to the laws of thermodynamics, the steam chamber will eventually
become hot. To keep the desalination process working, we have developed a cooling
system that needs no energy at all. The chamber is in the shade of the heliostats which
helps keep it cooler. To prevent the chamber from absorbing heat from its
surroundings, we must thermally insulated it. In addition, the insulation material
would be white so that it reflects as much sunlight of itself as possible. The insulation
material must also be a couple millimeters apart from the metal sheets. That allows
the most important element of the cooling system to exist. In the apace between, we
engrave and define boundaries for water paths. These paths incline downwards from
one edge to another. Cool water from the ocean go through these paths to cool down
the chamber. Eventually, this water becomes warmer, hence, easier to heat up.
Through a set of valves, this water goes to the water container for its desalination.
This is the water source which fills the container.
All valves streaming in/out water or steam is operated electronically by a main
computer. The computer also calculates temperatures and pressures of different areas
of the facility from feedback signaled from electronic sensors. According to these
information, the computer opens and closes valves to initiate different phases of the
process.
It is obvious that this desalination plant has special location requirements. It
must be close to a sea or any water source. Furthermore, it must be its altitude must be
lower than sea-level. That would probably require excavation works. More important
location relating issue is the project's latitude. Sunny places closer to the equator are
more convenient for our project. Actually, major parts of the design changes its shape
depending on the area of construction, e.g., the width of the heliostat row arc and,
accordingly, that of the concave mirror sector.
Further R&D is necessary for this technology to thrive. Many aspects of the
product need to be developed, especially building materials. Some information and
calculations are hard for high school students to acquire such as optical
measurements.
Sources:
1. http://www.universetoday.com/65588/what-percent-of-earth-is-water/
2. Lisa Henthorne (November 2009). "The Current State of Desalination".
International Desalination Association. Retrieved 2011-09-05.
3. http://sourcing.indiamart.com/engineering/articles/sea-water-desalination-
giving-new-lease-life-middle-east/
4. Applause, At Last, For Desalination Plant, The Tampa Tribune, December 22,
2007.
5. a b International Traffic Network, The world trade in sharks: a compendium of
Traffic's regional studies, (Traffic International: 1996), p.25
6. New York Times: Global Warming & Climate Change (2011 Durban
Conference), updated 21 dec, 2011.