Generating electricity: thermal, hydel, nuclear and renewable

Last time

Before we start: last time, in Water, forests and fishing, you learned these points. Here they are again on one card. Keep them in mind, because today builds on them.

Keeping the lights on

Pakistan has long suffered power shortages and load-shedding. Electricity comes from thermal, hydel, nuclear and renewable sources, each with its own costs and problems. This lesson covers them all.

Thermal power

Thermal power stations burn oil, gas or coal to boil water, and the steam turns turbines. They can be built near cities and produce power all year. But imported fuel is expensive, and they pollute the air and add to climate change.

Hydel power

Hydel, or hydro-electric, power uses water falling from a dam to turn turbines. Tarbela and Mangla dams generate large amounts. It is cheap once built, clean and renewable, and the dam also stores water for irrigation. But dams cost a lot to build, displace people, silt up, and produce less when river levels are low in winter.

Nuclear power

Nuclear power stations use the heat from splitting uranium. Pakistan has plants near Karachi and at Chashma. They produce large amounts of power with little air pollution. But they are very costly, produce dangerous waste, and carry a risk of accidents.

Why some costs rise

Thermal power depends on imported oil and gas, priced in dollars. A falling rupee or rising world prices raise the cost. Local gas reserves are running down, so more fuel must be imported. Old, inefficient power stations and losses in transmission add to costs.

Solar power

Pakistan gets strong sunshine most of the year, ideal for solar power. The Quaid-e-Azam Solar Park near Bahawalpur is a large solar plant, and many homes and farms now use solar panels. Solar is clean and free once installed, but produces nothing at night and needs batteries or other power.

Wind power

Strong, steady winds blow along the coast of Sindh, at places such as Jhimpir and Gharo. Wind farms there feed electricity into the national grid. Wind is clean, but varies with the weather, and turbines are costly to build.

Tidal and other renewables

Tidal power uses the rise and fall of the tides: water flows through turbines in a barrage as the tide comes in and goes out. The creeks of the Indus delta have potential for tidal power, though little has been built. Biogas from animal dung is used in some villages for cooking and lighting.

Power sources compared

The main sources side by side.

Why expand renewables?

They cut the cost of imported fuel and save foreign exchange. They are clean, helping Pakistan fight climate change, which threatens it with floods and heat. And they can bring power to remote villages not linked to the grid.

Mistakes that lose marks

Mistake one: calling hydel power non-renewable. Mistake two: describing tidal power as wind power at sea. Mistake three: listing advantages without explaining them. The fix: the right process, and explained advantages and drawbacks.

The full-marks tip

The full-marks tip: describe each process in steps: what turns the turbine, and how. For each source, give an advantage and a drawback for Pakistan.

On one card

So, on one card: electricity. Keep it for revision.