Renewable does not mean perfect
Renewable sources will not run out, and most give off little carbon dioxide. But each one still has costs. In the last lesson, Non-Renewable Energy: Pros and Cons, you sorted points into social, economic and environmental. Do the same here.
Key terms:
- Intermittent: not available all the time, because it depends on the weather or the Sun.
- Barrage: a wall built across an estuary with turbines in it, which are turned by the tide flowing in and out.
- Tidal range: the difference in height between high tide and low tide.
- Displacement: people being forced to leave their homes, for example when land is flooded to make a reservoir.
Wind and solar
🌬️ Wind
Advantages: no fuel to buy and almost no carbon dioxide when running (environmental). Land under onshore turbines can still be farmed (economic). Offshore turbines are out at sea, where the wind is stronger and steadier and few people live nearby (social).
Disadvantages: intermittent, because there is no power when the wind drops. Some people dislike the look and noise of onshore turbines (social). Blades can harm birds and bats (environmental). Offshore turbines cost more to build and maintain (economic).
☀️ Solar
Advantages: no fuel and no carbon dioxide when running (environmental). Panels can sit on roofs, so homes and villages far from the grid can make their own electricity (social and economic). Running costs are low.
Disadvantages: intermittent, because there is no power at night and less on cloudy days. Output is lower in places with little sunshine. Large solar farms take up a lot of land (environmental). Making the panels costs money and energy (economic).
Both work best where the resource is strong: windy coasts and hills for wind, and sunny places such as hot deserts for solar. Both have also become much cheaper to build over the past 10 to 15 years. Cheaper wind and solar is a big reason why more countries are using them.
Hydroelectric power (HEP)
HEP uses water flowing from a reservoir behind a dam through turbines. Large dams bring big advantages and big problems.
✅ Advantages
Economic: reliable, because the water can be stored and released when electricity is needed. Cheap to run once built. A large dam can also store water for farming and drinking, and make jobs in building.
Social: a dam can control floods downstream, protecting homes and farmland.
Environmental: almost no carbon dioxide when running.
❌ Disadvantages
Social: displacement. Valleys flooded behind the dam can drown villages and farmland, and people have to move. The Aswan High Dam in Egypt flooded land where many thousands of Nubian people lived.
Environmental: the dam breaks up the river, so fish cannot move along it. Habitats are drowned, and mud and nutrients get trapped behind the dam instead of reaching the floodplain.
Economic: very expensive to build, and it needs a steep valley and plenty of rain.
Tidal and wave
🌊 Tidal
Advantages: predictable, because tides come in and out twice a day and the times are known years ahead. No carbon dioxide when running (environmental). Running costs are low once built, and building and maintaining it gives jobs (economic and social).
Disadvantages: a barrage across an estuary is very expensive and changes the habitat of wading birds and fish (environmental). It stops generating at slack water, so it is predictable but not constant. Only a few places have a big enough tidal range, so it can only be used in a few coastal places.
🏖️ Wave
Advantages: there is a lot of energy in waves, especially on exposed coasts facing open ocean. No fuel needed and little carbon dioxide when running (environmental). It could give power to remote coastal communities (social).
Disadvantages: the technology is still being developed, so it is costly and few wave power stations exist (economic). Output varies with the weather and the season, so it is less steady than tidal power. Machines must survive storms and salt water. They can be a danger to boats and may disturb marine life (environmental).
Geothermal and biomass
🌋 Geothermal
Advantages: reliable, day and night, in all weather. Low carbon dioxide. The hot water can also heat buildings directly, which gives local people cheap heating (social and economic).
Disadvantages: only possible where hot rock is close to the surface, such as volcanic areas. Drilling is expensive (economic). Some gases and minerals can come up with the steam and cause pollution (environmental).
🌾 Biomass
Here this means modern biomass: crop waste, wood pellets and biofuels made from crops.
Advantages: can use waste. When new plants are grown, they take in carbon dioxide as they grow, which can balance the carbon dioxide released when burned. Reliable, and farmers can earn money (economic).
Disadvantages: burning gives off carbon dioxide and smoke. Land used for energy crops is not used to grow food, which can push up food prices (social). Forests may be cleared to grow crops (environmental).
Comparison table
Use this to revise. + is an advantage and - is a disadvantage.
| Source | Reliable? | Main advantages | Main disadvantages | Where it suits |
|---|
| Wind | No, intermittent | + no fuel; low carbon | - noise, look, birds; offshore costly | windy coasts, hills, open sea |
| Solar | No, intermittent | + no fuel; works on roofs | - no power at night; land for farms | sunny places, remote villages |
| HEP | Yes | + stored water; flood control | - displacement; ecosystems; cost | steep valleys with high rainfall |
| Tidal | Predictable, but not constant | + predictable; low carbon | - cost; estuary habitats | estuaries with a large tidal range |
| Wave | Varies with weather | + lots of energy; low carbon | - costly; storm damage; early stage | exposed ocean coasts |
| Geothermal | Yes | + day and night; heating | - limited places; drilling cost | volcanic areas, plate boundaries |
| Biomass | Yes | + uses waste; reliable | - carbon dioxide; land for crops | farming areas with plenty of waste |
Which suits which place?
A good geographer matches the source to the place and gives a reason.
- A remote, sunny village with no grid: solar panels. No power lines are needed, and sunshine is plentiful. Batteries can cover the night.
- A volcanic country such as New Zealand: geothermal. Hot rock is near the surface, and it gives steady power and heat.
- A windy island nation: offshore wind. Strong, steady wind and no space problems on land.
- A country with steep, rainy valleys: HEP. Water can be stored and used when demand is high. The cost to local people must still be weighed.
Because wind and solar are intermittent, many countries combine them with a reliable source. This is why places usually use a mix, not one source alone.
Common mistakes
- Saying renewable energy has no environmental impact. Dams drown habitats and turbines can harm birds.
- Saying wind and solar are reliable. They are intermittent.
- Saying HEP only has advantages. Displacement and damage to ecosystems are the main points to remember.
- Not saying where. Geothermal only works where hot rock is near the surface.
Exam-style question
Fig. 1.1 shows made-up data about a country's renewable electricity.
| Source | Share of renewable electricity (%) |
|---|
| HEP | 60 |
| Wind | 25 |
| Solar | 10 |
| Biomass | 5 |
(a) Calculate the share that comes from wind and solar together. [1 mark]
(b) State two disadvantages of building a large dam for HEP. [2 marks]
(c) Explain why wind and solar power are described as intermittent. [2 marks]
(d) To what extent is HEP the best choice for this country? [6 marks]
Model answer
(a) 25 + 10 = 35% (1).
(b) People are displaced when the valley floods (1). Ecosystems and habitats are drowned or the river is broken up (1). [Very expensive to build also scores.]
(c) There is no wind when the air is still (1), and no sunlight at night or in cloud (1). They cannot make power all the time.
(d) Level 3 (5-6 marks): Balanced answer with developed points for and against and a supported judgement. Level 2 (3-4 marks): Some points on both sides, or developed points on one side. Level 1 (1-2 marks): Simple statements only.
Example full-mark answer: HEP supplies most of the country's renewable electricity (60%) because it is reliable. Water can be stored and released when demand is high, and a dam can reduce floods. Running costs are low and it gives off almost no carbon dioxide. However, a large dam is very expensive and floods valleys, so people lose their homes and habitats are drowned. Wind and solar are cheaper and do not displace people, but they are intermittent. So HEP is the best main source because it is reliable, but it is not perfect, and the country should add wind and solar for the future. Choosing sites with few people would reduce the harm.
Exam tip
In "To what extent" answers, use the word "because" and finish with a judgement that names which source suits the place.