Energy for water and water for energy is a concept called as Water-energy-nexus. It means that we can obtain energy from water and we also need energy to make water usable. In this blog post, we are going to see how energy can be obtained from water.
Energy from water can be obtained by following ways:
- Energy from compounds in seawater
- Osmotic power
- Tidal energy/Wave energy
- Sea water temperature differences
- Water splitting
Let’s see how each one of these works.
When water is in motion, that is if it is either running as in an ocean or falling as in a waterfall, it is full of kinetic energy. This energy can be converted to useful energy i.e. electricity. Electricity generated from hydro-power is known as hydroelectricity. Hydro-power satisfies 20% of the world’s needs, making it the most widely used form of renewable energy so far.
Energy from compounds in seawater:
Seawater covers two-thirds of our planet. US Navy wants to power warships with it. They aren’t making use of the fact that water has salt, but that it can get hydrogen and carbon dioxide from it, turning them into liquid hydrocarbon fuels. What’s even more interesting is that the technology created by the US Navy scientists simultaneously captures hydrogen and carbon dioxide.
Want to do some DIY project that involves seawater to energy? Have a look at the following video of how one can make a salt water battery. The reason we can use the salinity of water is because salt in the water helps it conduct electricity. Distilled water that is free of salts is a poor conductor of electricity. Salt water is thus as an electrolyte solution since it conducts electricity. Common salt is an ionic compound that ionizes into sodium and chloride ions when dissolved in water. A very good explanation of how a salt battery works is given here.
Just as second law of thermodynamics that says heat naturally flows from higher temperatures to lower temperatures, so does the water in saline water. If fresh water and seawater are kept side by side, separated by a membrane that only lets water pass and not salt, we will see that water from the freshwater side will move towards seawater side. Thus the concentration of salt will go on increasing on the fresh water side. This is known as osmosis. The concentration difference or the salinity gradient is what creates electricity. This is because in order to stabilize the concentration on both the sides, pressure is compensated which in turn drives the turbine that generates electricity.
Tidal energy/Wave energy:
Tidal or wave energy is the energy obtained from tides/waves. Various organizations are trying to harness this kind of energy. UC Berkeley is developing a new Wave Energy Converter that is able to efficiently harvest this energy. It is called a ‘Wave Carpet’. It is inspired from mud because mud dampens ocean waves. CETO on the other hand is a first operating wave energy array scheme in the world. It not only converts wave energy to electricity, it also converts saline water to fresh water. The Swansea Bay tidal lagoon project in the UK and the MeyGen tidal array project in Scotland are two of the large-scale tidal power projects currently under development. Another interesting project is the use of dielectric materials to convert the movement of water into electricity, something that can be used on our houses or in our toilets.
In theory, oceans could power the entire globe without adding any pollution to the atmosphere. And they could provide a more dependable source of electricity than the wind or sun. – Nature
Seawater temperature differences:
Research has indicated that electricity can be obtained from temperature gradients in Pacific. This concept is the newest of all.
Water can be split into its basic elements: hydrogen and oxygen. It happens during photosynthesis. Hydrogen is a very efficient and clean fuel. There are various ways to split water. Two of the many ways to split water are electrolysis and photo-catalysis. People who promote hydrogen as a highly potential fuel, promote this technology and call it the hydrogen economy.