Energy Resource Types

What makes an energy resource renewable?

An energy resource is a source we can use to provide energy for activities such as heating, transport and generating electricity. Resources are classified according to whether natural processes replace them quickly enough for continued human use—not according to whether they are cheap or environmentally harmless.

Non-renewable resources have finite stocks and are not replaced on a human timescale. Coal, oil and natural gas are fossil fuels: they formed from ancient organic material over millions of years. Using them consumes a stock that cannot quickly be replaced. Nuclear energy is also non-renewable because its fuel, such as uranium, is finite, although it is not a fossil fuel.

Renewable resources are replenished naturally on a human timescale. They include wind, solar, hydroelectric power, waves, tides, geothermal energy and biomass. Hydroelectric power uses moving water, geothermal energy uses heat from within the Earth, and biomass uses organic material such as plant matter. Biomass must be replaced as it is used if its supply is to remain renewable.

Renewable does not mean available everywhere or at every moment. Wind is replenished naturally, but a wind turbine cannot provide a steady output regardless of weather. Nor does renewable mean impact-free: constructing equipment can cause emissions and developing sites can affect people and habitats.

Coal: developing a finite resource

Coal is a fossil fuel formed from ancient plant remains. It occurs in coal seams, layers within rock, and must be mined before it can be used. Developing coal as an energy resource therefore involves extraction as well as transporting and burning the fuel to produce energy.

Coal has several practical and economic advantages. Large reserves are available around the world, and improvements in machinery and mining technology have made accessible deposits cheaper to extract. Lower extraction costs can make development more profitable and help provide relatively cheap energy.

Coal can also be stored until it is needed. Unlike wind, its availability at a power station does not depend on the weather at that moment. This makes it a reliable resource, provided that supplies of fuel are maintained. However, coal is heavy and bulky, so transporting it adds a cost and requires suitable infrastructure.

Coal's costs to people and the environment

Some disadvantages arise during extraction. Opencast mining removes surface material over large areas, destroying habitats and changing the landscape. Mining also produces waste tips and can pollute water sources. Miners face risks from accidents and mine collapse, while exposure to coal dust can cause lung disease. A cheap energy supply can therefore come with serious costs to workers and nearby environments.

Other disadvantages arise when coal is burned. Burning coal releases carbon dioxide, a greenhouse gas that contributes to climate change. It also releases air pollutants, including sulphur dioxide, which contributes to acid rain. These impacts extend beyond the mine or power station itself.

Coal's reliability and relatively low production costs are important advantages, but they do not remove its environmental damage or its finite nature. A judgement favouring coal for dependable energy in the short term must still account for the longer-term consequences of emissions and continued depletion.

Wind: using a replenished resource

Wind turbines convert energy from moving air into electricity. They can be developed on land or offshore, and projects can range from individual turbines to large wind farms. This flexibility allows development at different scales, while large wind farms can generate significant amounts of electricity.

Wind itself does not need to be mined or purchased as fuel. Although turbines are expensive to build and install, they are relatively cheap to run. Building and maintaining them also creates jobs. Improved turbine designs can generate more electricity, and falling equipment costs can make development more affordable.

During electricity generation, wind turbines do not burn fuel, so they produce no greenhouse gas emissions or combustion-related air pollution. This is a major advantage over coal. Nevertheless, manufacturing, transporting and constructing turbines can generate carbon dioxide: their operation is not the same as their whole-life environmental impact.

Wind's limitations and a balanced judgement

Wind generation is intermittent. Turbines need suitable wind conditions: very weak winds provide insufficient energy, while excessively strong winds can prevent safe operation. Output therefore varies, making wind less dependable on its own than a fuelled power station.

Wind farms can also create local conflicts. Some people consider turbines visually intrusive, and nearby residents may be affected by noise. Turbines can interfere with bird migration and birds may collide with moving blades. These disadvantages show why the location of development matters.

Wind offers a renewable supply with low running costs and no emissions during generation, but these benefits must be weighed against construction costs, variable output and local impacts. Development is more attractive where wind conditions are suitable and harm to residents, landscapes and wildlife can be limited.

Comparing development choices

A useful evaluation connects each advantage or disadvantage to its consequence. Coal's ability to be stored supports dependable generation, but burning it causes emissions. Wind avoids those operating emissions, but changing weather makes its output variable.

Neither classification alone decides whether a project should go ahead. A balanced judgement considers the resource's availability, the costs of development and operation, the reliability of supply, and the effects on people and the environment.