Thermal Desalination
Water is one of our most important natural resources. Whether it is from reservoirs, rivers or underground aquifers, we rely on water for our survival. We need water for drinking, growing food, and sanitation.
Water security is “The capacity of a population to safeguard sustainable access to adequate quantities of acceptable quality water for sustaining livelihoods, human well-being, and socio-economic development, for ensuring protection against water-borne pollution and water-related disasters, and for preserving ecosystems in a climate of peace and political stability.” Working definition, UN-Water, 2013 |
Our planet contains a lot of water, but only 3% is fresh water, and only 1% is available to humans, the rest is locked up in glaciers, icecaps etc and therefore is a reasonably scarce resource. We currently have technologies such as reverse osmosis and thermal desalination to make fresh water from salt water, however they are expensive to run due to the energy required to make the process work, hence are not used in many applications.
Key to making this process more cost effective is reducing the cost of the energy required. This can be achieved by using free energy sources such as the sun that provide a plentiful source of energy and a plentiful source of heat.
Key to making this process more cost effective is reducing the cost of the energy required. This can be achieved by using free energy sources such as the sun that provide a plentiful source of energy and a plentiful source of heat.
In this task you are going to design, build and test a solar thermal desalinator. This will use heat energy from the sun to evaporate the salty water so that the fresh water can be collected. You will test the water both before and after the desalination process to see if it has reduce the salt level enough to make it safe to irrigate crops. This task will involve the following steps
Define
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Deconstruct the problem to specify the requirements of the task. Some of the questions that may help you with this are as follows
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Ideate
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In this stage you will come up with at least three different ideas for the design of your desalinator. Each of these designs must include the following
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Prototype
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In this section you will need to turn your idea into a reality by using he tools and materials in the STEM Centre to build your design. You will need to document your build process as part of this task. This involves making notes about what you did, successes, challenges etc as well as annotated photos.
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Test and Evaluate
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When the prototype is created you will test the design to determine how effectively it works. If there is time you can go back and make changes to your design.
You will then undergo a process of self and peer evaluation in which you will look critically at your design to look at the postives of the design as well as factors that could have been improved with more time |
To measure the extent to which you have desalinated the water you will test it using a refractometer. It measures salinity by determining how far the light bends as it passes through your saline sample. It allows you to accurately determine the salinity of your water.
You should test the water before and after moving through your desalinator to see to what extent the salt has been removed. The video opposite will show you how to use this apparatus properly. |
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