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12 Cards in this Set
- Front
- Back
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What is a TV pick-up? |
A sudden change in demand for electricity caused when popular TV programmes have breaks and great numbers of viewers switch on lights or kettles etc. |
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What is a 'pumped storage' power station? |
At pumped storage hydroelectric stations water is pumped back into the reservoir when there are periods of low power demand. This is often when there is excess energy being produced by other power stations.This stores energy and during higher demand periods the water can be allowed to flow back down to produce electricity just like a normal power station. Such a system saves energy and also can be turned on quickly at times of peak demand. |
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What is an electricity tariff? |
It is the amount that customers pay for electricity. Companies try to reduce the demand for electricity during the day by increasing the price. |
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Look at the Figure. Explain the demand for electricity on a typical winter day. |
The demand rises from 5 or 6 am until about 9 am, as people are getting up, having breakfast and going to work. It is level from about 9 am until 4 pm when most people are at work and using electricity in offices and factories. It rises toa peak at about 6 pm as people get home, switch on the heating and the TV and start cooking dinner. The demand gradually decreases during the evening and becomes low again by about midnight, when most people have gone to bed. |
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(a)Why is there a peak in demand in the early evening in winter but not in summer? (b) Why is there more demand for electricity in winter than in summer? |
(a) Possibly because people turn their heating on when they get home from work in the winter and fewer people cook hot meals in the summer.
(b) More energy is used for space heating and lighting (and possibly more hot meals and hot drinks are made). |
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(a)Why do power engineers need to know what weather is forecast for the next few hours? (b) Why do they sometimes need to know what the TV schedules are? |
(a) So they can try to predict how much electricity will be needed and make sure it will be available.
(b) Advert breaks in popular programmes can cause sudden increases in the demand for electricity. |
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Why can’t power engineers just use hydroelectricity to meet sudden demands? |
There is not enough capacity/there are not enough hydroelectric power stations to generate the extra amount of electricity required. |
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Other than hydroelectricity, which renewable resources are available at predictable times? |
Geothermal energy is available all the time in countries where it is possible; tidal power is available at predictable times. |
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When might wind power be available but not solar power? |
Winds blow during the night as well as in the day time; days without much sunshine are often due to poor weather, which is often accompanied by strong winds. |
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Look at the Figure. Explain when a pumped-storage power station would be: (a) pumping water up to the top reservoir (b) generating electricity. |
(a) During the night (or from 10 pm to 6 am, or similar times) as this is when demand is low and there will be spare capacity from fossil-fuelled and nuclear power stations. (b) Early evening (or between about 4 pm and 8 pm), when the demand is highest. |
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Explain why electricity is often cheaper to use from about 11 pm to 6 am. |
Electricity companies need to match supply with demand; there is normally more demand during the day and evening and less between 11 pm and 6 am; it takes some time to start up fossil-fuelled power stations so they are usually left running; this would waste electricity at night; electricity companies try to persuade people to use more electricity at night and less during the day by making it cheaper. |
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What are the key points to remember? |
The demand for electricity varies during the day and during the year. Demand is highest during the day and in the early evening. Hydroelectric power stations can provide extra electricity within a minute. It takes some time to start up power stations from cold, so they are often left running. Spare electricity is used at night to pump water up to the top reservoirs in pumped storage power stations. Electricity companies try to persuade us to use less electricity during the day and more at night by having different prices for different times of day. |
