The Physical Properties of Water
3 min read · Energy Atlas Editorial
Water is a chemical compound made from one oxygen and two hydrogen atoms. At normal conditions, it is a colourless, clear, and odourless liquid.
Molecule of water
Water is a chemical compound made of hydrogen and oxygen.
At room temperature and atmospheric pressure, it is a colourless, clear and odourless liquid.
In nature, it is found in three states:
- solid — ice and snow
- liquid — water
- gas — water vapour
Molar mass · 18.01528 g/mol Melting temperature · 0 °C (at atmospheric pressure) Boiling temperature · 100 °C (at atmospheric pressure) Density · 0.99997 g/cm³ (at 3.98 °C) Viscosity · 0.001 Pa·s (at 20 °C) Refraction index · 1.33 Critical temperature · 373.95 °C Critical pressure · 22.064 MPa Surface tension · 0.073 N/m (20 °C) Sound velocity, roughly · 1,460 m/s Specific heat coefficient · 4,184 J/(kg·K) (liquid water at 20 °C)
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Articles
The Origin of Water Energy
The Sun warms surface water and evaporates it. After condensation, the water falls on the land with exploitable potential energy relative to ocean level.
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History of Water Energy Utilization
The energy of water was used since ancient times for grinding grain or irrigation. Later it powered mills or hammers, and finally a turbine was invented.
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Water Energy and Its Uses
The amount of available water energy, kinetic and potential, depends on hydrologic potential, mostly on hydraulic head and flow rate.
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Dams and Reservoirs
The dams create water reservoirs for hydro power plants, to prevent floods or to collect drinking water. Typical dams are gravity or concrete arch dams.
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The Highest Dams and Largest Reservoirs
The highest dam is the 305 m high, concrete arch-shaped Jinping-I dam in China. The largest reservoir is Lake Kariba in Zambezi, with a volume of 180 km3.
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The Segner Wheel
The Segner wheel was an important step on the way to modern turbines. Its principle is today used in rotating irrigation sprinkler systems.
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Francis Turbine
The Francis turbine has a radial-axial design, variable pitch guide vanes, and fixed runner blades. The largest one has a diameter of 10 m.
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Kaplan Turbine
The Kaplan reaction water turbine with adjustable blades, invented in 1918, is used in places with minimal heads and relatively high, variable flow rates.
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Pelton Turbine
The Pelton turbine is an isobaric impulse action turbine. The water jet is directed tangentially at the spoon-shaped buckets on the runner.
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Choosing a turbine (Turbine selection graph)
The turbine selection graph helps to select the best turbine type for the given hydraulic head and rate of flow.
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Hydroelectric Power Plant Operating Principles
In hydroelectric power plants, the water propels the turbine blades, and the generator transforms the energy of a rotating turbine shaft into electricity.
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Types of Hydroelectric Power Plants
The hydroelectric power plants can be divided into accumulation ones with a reservoir, run-of-the river without a dam, derivational, and pumped-storage.
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The Largest Hydroelectric Power Plants in the World
The largest hydroelectric dams in the world are the "Three Gorges Dam" in China, Itaipú Dam and Guri Dam in South America.
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Tidal Energy and Sea Wave Power
Tidal power plants use ebb-tide energy from turbines in the dam enclosing a tidal basin, while tidal stream generators are turbines anchored to the seabed.
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Marine Current Power and Ocean Thermal Energy
Energy contained in ocean currents can be exploited by various underwater turbines or by an OTEC system that uses ocean temperature differences.
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Environmental Impact of Hydropower
The construction of a hydroelectric power plant affects a large area ecosystem and often leads to people's relocation. Then a new balance is established.
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