Power Choices

Power Choices

Keeping the lights on is a balancing act. Every energy resource costs something: money, reliability, or damage to the planet. There is no perfect option, which is why this is a topic about judgement rather than facts. The first division is simple, and it rests on one test: is the resource replenished as fast as we use it? • If yes, it is renewable. Wind is the obvious case: using it today takes nothing away from tomorrow. • If no, it is non-renewable, meaning finite. Coal is the obvious case: every tonne burned is a tonne that will not be there again. Apply that test rather than memorising a list, and the awkward cases become answerable.

Which are renewable?

Apply the test to these six. Select ALL THREE that are RENEWABLE.

• Tidal
• Geothermal
• Bio-fuel
• Nuclear
• Oil
• Natural gas

The truth about nuclear

Nuclear power is often described as "clean energy". Which statement is accurate?

• It is non-renewable and produces long-lived radioactive waste, but it is reliable and releases very little carbon dioxide
• It is renewable, because the fuel releases so much energy that it effectively never runs out
• It is a fossil fuel, so it releases a great deal of carbon dioxide
• It produces no waste or hazards of any kind

Weighing it up

Choosing a resource means weighing several things that pull against each other. These are the words the marks are written in:

Match each resource to its trade-off

Always two-sided

Here is the rule that decides the band on every comparison question in this topic. Each resource gets a specific benefit AND a specific cost. Never a one-sided list. The reason is that a one-sided answer cannot be weighed. "Renewables are good for the environment" is not a comparison, because there is nothing on the other side of it, and the question asked you to choose. Two words matter. Specific: "damages the environment" is worth less than "flooding a valley destroys habitats". And each: if you criticise gas for its emissions, you also have to say what gas is good at, or you have written an opinion rather than an evaluation.

One resource, both sides

Take gas, which is the resource most often written about badly because it sits in the middle. What it is good at: it is reliable, so it can be turned up within minutes when demand spikes on a cold evening, and a gas station is comparatively cheap and quick to build. That flexibility is exactly what an intermittent supply needs sitting behind it. What it costs: it is a finite fossil fuel, and it releases carbon dioxide when burned. Less than coal for the same electricity, which is a real difference and not an excuse, but far from none. Now read that back. Neither half is an opinion, both halves are specific, and an examiner can see a judgement being made rather than a preference being announced.

Build the comparison

Wind produces no carbon dioxide while it is running and the fuel is free, _____ it is _____, so it delivers nothing on a calm day. Gas releases carbon dioxide and is _____, but it is reliable and can be turned up within minutes. A sentence built like that can be _____; a one-sided list cannot.

A still day

A country generates much of its electricity from wind. On a still, windless evening in winter, what is the main problem?

• Wind is intermittent, so very little is generated exactly when demand for heat and light is highest
• The turbines begin releasing carbon dioxide when they are not turning
• The wind resource has run out, in the way coal eventually will
• The turbines start producing waste that has to be stored

Electricity is not the whole of it

A country uses energy for three things: generating electricity, transport and heating. People discussing "switching to renewables" usually mean the first, and the other two are the larger problem:

The harder half

A country switches all of its electricity generation to renewables and nuclear. Its total greenhouse gas emissions fall, but by much less than people expected. Why?

• Electricity is only one of the things energy is used for: transport and heating still run largely on fossil fuels
• Building the new stations released so much carbon dioxide that it cancelled the saving out
• Nuclear releases as much carbon dioxide as the coal it replaced
• People used more electricity once they knew it was clean

How a country decides

Put the stages of choosing an energy mix into a sensible order.

• Work out how much power is needed, and when the peaks fall
• Rule out what the geography does not allow: no tidal without a coast, no hydro without valleys and rainfall
• Weigh the remaining options on reliability, cost and environmental impact
• Choose a mix, so that a reliable resource covers the gaps left by the intermittent ones
• Review the decision as build costs and fuel prices change over time

The town's decision

A town is deciding how to generate its electricity. Weigh the factors one at a time.

• The town needs power available on demand, including on calm, cloudy nights. Which choice guarantees that best?
• They are told the site is windy and coastal. Does that settle it in favour of wind alone?
• Nuclear is low-carbon and reliable, but expensive to build and leaves long-lived waste. What is the sensible plan?
• A councillor writes: "Renewables are better for the environment, so we should use them." What is wrong with that as an argument?

Write the evaluation

Exam practice. In about 60 words, evaluate whether a country should build a new nuclear power station rather than more wind farms. Include:

• a specific benefit AND a specific cost for nuclear
• a specific benefit AND a specific cost for wind
• a judgement that weighs them, rather than a preference stated at the end