Hydro-electricity, Waves and Tides


  • Hydro-electric power = requires flooding of a valley by building a big dam. Water is allowed through turbines
  • No pollution
  • immediate Flooding of valley = vegetation immediate rots = releases immediate methane and immediate CO2
  • immediate Loss of habitat
  • Can look unattractive
  • Can provide immediate supply of energy when there is a high demand (except in a drought)
  • High initial costs, but no fuel costs andminimal running costs
  • Wave power = lots of small wave-powered turbines around the coast
  • No pollution
  • Disturb the seabed & habitat of marine animals
  • Spoil the view
  • Hazard to boats
  • Wind drops = waves tend to die out = unreliable
  • High initial costs, but no fuel costs and minimal running costs
  • Tidal Barrages = big dams which are built across river estuaries. They have turbines in them
  • Tide comes in = fills up estuary = water allowed out through turbines
  • Gravitational pull of sun and moon = tides
  • No pollution
  • Prevents free access by boats
  • Spoils the view
  • Changes wildlife habitat
  • Tides happen twice a day = reliable
  • Lower tides = low amounts of energy
  • Do not work when the water level is equal on both sides of barrage
  • Initial costs are quite high, but no fuel costs and minimal running costs

How long have you…? (present perfect 4) Exercises




Use the information given to create questions beginning with ‘How long…?’

• It is snowing.

• The weather is shining.

• John and Kate are married.

• My brother has gone on holiday.

• My aunty and uncle live in Canada.

• My sister is a teacher.

• I work at the chemist.

• I’ve known Susan since I was a baby.

• Jonathan is learning to speak to Mandarin.




Fill in the missing gaps in the sentences using the present perfect (=has/have + past participle)

• I have known Kate a long time.

• My brother has been playing the piano he was 11 years old.

• My mum and dad on holiday to America. They

gone since last Sunday.

• I Ben and Emma since primary school.

We to the same primary and secondary school.

• My sister learning to speak French because she
is going to France next month.



Use the appropriate words in the missing gaps.

have you lived       lives      to

has been       works        have known

I have bought       have worked.

• My sister in Spain. She is studying Spanish

with her friend Rosie. I Rosie since I was 5.

• Spencer like with Jamie. They have worked

together for 2 years.

• How long in Australia?

• a new dress for prom.

• He to Thorpe park.



Challenge: Create 4 of your own questions beginning with ‘How long……?’








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“Every accomplishment starts 
With the decision to try.” Gail Dever

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