Hydro

Question 1

Derive the equation for power

Answer 1

Power=energy/time=m.g.h/t
m=density*volume

Power= density.volume.g.h/t

Volumetric flow rate (r)=V/t

so: Power= density.g.h.r

Applying an efficiency:

Power= density.g.h.r.efficiency

Question 2

What is the water cycle?

Answer 2

Water in the oceans evaporate and rise to form clouds in the sky

Evapotranspiration from plants release more water vapour which is stored in the atmosphere as clouds

Eventually the clouds precipitates and causes ice and snow to form in mountainous regions and water in other areas.

Snow and ice eventually melt and run off to nearby water storages like rivers and the sea.

Infiltration leads to ground water to be discharged and run to a water storage in oceans

Question 3

Are you aware of the different types of hydroelectric plant as categorised both by head height and by power capacity? And the different types of turbine used?

Answer 3

Low head hydroelectric power plants- Less than 30 m
Medium head - 30 to 300m head
High head- more than 300m head

Question 4

What are the types of turbines? And what are its features?

Answer 4

Francis turbine: Medium head and reaction turbine
Kaplan Turbine: Small head and reaction turbine
Pelton turbine: High head and impulse turbine
Turgo turbine: High head and impulse turbine
Crossflow: Medium head and impulse turbine

Question 5

What are the advantages of hydroelectric power?

Answer 5

Low cost source of low carbon electricity
Renewable resource with high conversion to electricity efficiency 80% +
Low greenhouse gas emission
Scalable technology from micro to large scale production
Can be used for base load, peaking and pumped storage applications
Inexpensive to run due to low maintenance costs once installed
New opportunities such as irrigation, aquaculture, flood prevention and water sports
Long lifetimes relative to other power sources

Question 6

What are the disadvantages of hydroelectric power?

Answer 6

High initial installation costs
Requires flooding of large areas upstream and the altered water flow impacts upon the river flow and aquatic life downstream.
Anaerobic decay of un-cleared vegetation can produce CH4
Long lead time in construction of large projects
Variable output dependent upon weather
Possible dam or supply failure
Flooding of large areas of land with associated loss of agriculture and relocation of communities
Silting restricts the lifetime of the system