2.3 - Energy Resources Introduction

Non-renewable resources will run out one day

• A non-renewable energy resource is one that's used up faster than nature can replace it, so it will one day run out.
• The non-renewables are the fossil fuels and nuclear fuel.
• The three main fossil fuels are coal, oil, and (natural) gas. These formed underground over millions of years and are burnt to release their energy.
• The nuclear fuels are uranium and plutonium.

What they have in common

• Reliable - Power stations keep fuel in stock, so they can generate electricity whenever it's needed. Gas power stations can also respond quickly when demand increases, but nuclear power stations are slow to start up.
• Will run out - They're being used far faster than they form.
• Damage the environment - All non-renewables harm the environment.

Renewable resources will never run out

• A renewable energy resource is one that's replenished as fast as (or faster than) it's used, so it will never run out.
• The renewable energy resources are:
  • The Sun (solar)
  • Wind
  • Water waves
  • Hydroelectricity
  • Tides
  • Biofuels

How they compare with non-renewables

• They do less harm to the environment than fossil fuels, though most still cause some damage.
• Several are less reliable, because they depend on the weather and can't always produce energy on demand.
• Many produce less energy than a fossil-fuel or nuclear power station, but they have low running costs once built.

Uses - Electricity, transport and heating

• Both renewable and non-renewable resources are mostly used to generate electricity, which can then be sent wherever it's needed.
• The two other major uses are transport and heating.

Transport

• Petrol and diesel vehicles (including most cars) use fuel made from oil.
• Many vehicles run on a mix of biofuel and petrol or diesel, or on pure biofuel.
• Electricity can power vehicles such as trains and cars, generated from either renewable or non-renewable resources.

Heating

• Natural gas is the most widely used fuel for heating UK homes - the gas heats water, which is pumped to radiators.
• Coal can be burnt in a fireplace, and burning biofuel can also heat homes.
• A geothermal heat pump uses geothermal energy to heat buildings.
• Solar water heaters use the Sun to heat water that's pumped to radiators.
• Electricity from any resource can be used for heating (e.g. in electric heaters).

In terms of energy stores

1. A fuel holds energy in its chemical energy store.
2. Burning it transfers that energy to the internal (thermal) energy store of its surroundings.
3. From there it can transfer to other useful stores, such as the kinetic energy store of a moving vehicle.

We still depend on fossil fuels but want more renewables

A country's mix of energy resources changes over time, driven by new technology, better understanding of environmental effects, and changes in cost.

How UK electricity use has changed

• Over the 20th century, UK electricity use rose sharply as the population grew and people used electricity for more things.
• Since the start of the 21st century, electricity use has been slowly falling, as appliances became more efficient and people used energy more carefully at home.
• Some electricity is still produced from fossil fuels and nuclear power; the rest comes from renewables such as wind.

Why people want more renewables

• Burning fossil fuels is damaging to the environment, so people want resources that do less harm.
• Because non-renewables will run out, countries need alternatives before fossil fuels are exhausted.
• Public and international pressure leads governments to set renewable targets, pushing energy providers to build renewable power plants.
• Electric cars and hybrids (powered by two fuels, such as petrol and electricity) are becoming more popular.

Weighing up which resource to use

• Factors when choosing a resource include: availability, cost, reliability, environmental impact, and opportunities such as jobs.
• For a power station, useful comparisons include:
  • Start-up time - How long before it begins producing energy.
  • Generating capacity - The maximum power it can produce in normal conditions.

Evaluating data on wind turbine energy output

• When choosing a renewable resource, you often have to analyse data on its energy output and judge how valid that data is.
• Wind turbines are a good example, because their output depends strongly on how they're built and where they're placed.

Reading the data

• Longer blades give more power - For both locations, a 50 m blade produces more power than a 35 m blade. Longer blades sweep a larger area, capturing energy from more moving air.
• Off-shore turbines produce more power - For a given blade length, the off-shore turbine has the higher output, because sea winds are stronger and steadier than on land.
• More power costs more - Large off-shore turbines have a far higher start-up cost, mainly because building and connecting turbines at sea is difficult and expensive.

Judging whether the data is valid

Before trusting figures like these, ask how they were obtained: were the turbines tested under the same wind conditions, over how long a period were readings taken, and who collected the data (a manufacturer may quote a best-case output). Output also varies with the weather, so a single power figure is really an average or maximum, not a constant output.

Comparing costs for heating and transport

Data from secondary sources can be used to compare the cost of using different energy sources for heating and transport.

Heating a home

• Most homes use central heating, where water is heated in a boiler and pumped to radiators.
• Gas central heating is usually more cost-effective than electric heating.
• A biomass boiler is typically less cost-effective than either gas or electric heating.
• Solar thermal panels are expensive to buy and install, but sunlight is free, so they have no fuel costs. However, they depend on sunny weather.

Transport

• Electric vehicles usually cost more to buy, but are cheaper to run because electricity costs less per mile than petrol or diesel.
• Biodiesel can be expensive to buy, though some people produce it cheaply themselves.
• Range is the maximum distance a vehicle can travel on a full tank or charge:
  • Petrol, diesel and biodiesel cars typically manage 300-400 miles.
  • Electric cars typically manage less, around 200-300 miles.
• Efficiency - Electric vehicles are the most efficient, meaning more input energy is transferred to the kinetic store of the vehicle. Diesel and biodiesel have similar efficiencies, both higher than petrol.