Tidal Power Flashcards
How are tides produced?
The gravitational attraction between the Earth and the moon creates tidal flow of water that produces 2 periods of high water and 2 periods of low water in each 25 hour cycle
Where can tidal power be harnessed?
The speed of water flow in most areas of sea are too slow to harness but the flow may be focused, and velocity increased by coastal features and seabed topography
What 3 methods are there for harnessing tidal power?
Tidal barrages
Tidal lagoons
In-stream turbines
How do tidal barrages allow tidal power to be harnessed?
It is a dam across an estuary or bay in which turbines are located
This means all water flowing in or out of a lake created behind the barrage flows over the turbines
Name an advantage of tidal barrages
It makes maximum use of the tidal flow of water in and out of an estuary or bay
Name a disadvantage of tidal barrages
Financial and environmental costs are high
How are tidal lagoons different to tidal barrages?
They only surround a selected part of an estuary or bay, dont stretch all across it
This earns only part of the area is effected unlike barrages, and ecologically sensitive areas can be avoided
What do some tidal lagoon schemes propose?
Multiple lagoons next to each other e.g. Bristol Channel
What can happen if the demand for energy is too low when it is being generated?
Water can be pumped into a lagoon using the surplus energy, producing a higher water level than the sea
Electricity can be generated later when demand is high without the need for tidal water flow
How do in-stream turbines work?
They are fixed to the seabed and absorb the kinetic energy of natural tidal flow
Compare in-stream turbines to tidal lagoons and tidal barrages
They harness much less energy than a barrage or lagoon
The environmental impacts are very low because they dont have any significant impact on tidal flow
What are the advantages of tidal power?
They are predictable: the position of the sun and moon can be predicted meaning the times and ranges of tides can be
A tidal barrage on a large estuary would have a large electricity output compared to most other renewable energy schemes
What are the disadvantages of tidal power?
They are intermittent so it makes it difficult to meet continual demand
There are few sites where it would be economically viable
The environmental impacts of barrages are larger than that of other renewable schemes
Why is it rare to find locations where tidal power is economically viable to exploit?
Seawater usually moves quite slowly
What locational features make tidal power viable?
Coastal feature like estuaries and headlands may concentrate the flow and increase water velocity
If tidal range is large and the mass of moving water is, it might be viable to harness
What are 4 named environmental impacts of tidal barrages?
Materials
Tidal range change
Sedimentation
Pollutant concentration
What are the environmental impacts of tidal lagoons because of the materials?
- the size of of a large barrage requires large quantities of material for construction, these have environmental impacts during extraction,processing,transport and installation
E.g. rock,cement
Explain tidal range change as an environmental impact of tidal power
The barrage reduces the ease of water flow in and out a lagoon, high tide not as high and low not as low
Explain why sedimentation is an environmental impact of tidal power schemes
Because of barrages, there are some areas of fast water flow where sediments can be eroded and carried away, but there is also areas of very slow water, meaning sediments can be deposited and may build up.
Sediments settling will mean the turbidity is lower.
Why is pollutant concentration an environmental impact of tidal power schemes?
Pollutants from human activities around lagoons or in catchment areas may build up in lagoons
How do the environmental impacts in tidal lagoons compare to those in tidal barrages?
They are similar but on a smaller scale- because they don’t involve a whole estuary
There are more chances to avoid sensitive areas e.g. avoid migratory species paths
How do the environmental impacts of in stream turbines compare to lagoons and barrages?
They dont block the natural tidal flow so dont have the same impacts
What environmental impacts do in-stream turbines have?
They can produce noise that affects marine animals like whales and dolphins
The effect is localised unless a large amount were installed over a large area
Why have new proposed tidal technologies not been tested?
Because tidal power isn’t widely used
Explain how one new proposed tidal power technology works
Tidal reefs
Similar to a barrage in that it crosses an estuary but it is not as tall so water can flow over and marine organisms can still move
