What is renewable energy?
Renewable energy is the term used to describe energy flows that occur naturally and continuously in the environment, such as energy from the wind, waves or tides. The origin of the majority of these sources can be traced back to either the sun (energy from the sun helps to drive the earth’s weather patterns) or the gravitational effects of the sun and the moon. This means that these sources are essentially inexhaustible.
Why use renewable energy?
The key issue is how to extract this energy as effectively as possible and convert it into more useful forms of energy. This can range from directly using the energy from the sun to heat water to using mechanical devices, such as wind turbines, to convert the kinetic energy in the wind into electrical energy.
Energy underpins virtually every aspect of our economy and day-to-day lives. However, the use of fossil fuels, which currently provide the bulk of our energy, releases greenhouse gases (such as carbon dioxide) into the atmosphere. Due to factors such as population growth and changes in lifestyle, the demand for energy has increased to levels where the burning of fossil fuels is releasing enough greenhouse gases into the atmosphere to begin to directly affect our climate system.
There is now a scientific consensus that climate change is real and that it poses an immense threat to the world we live in. Impacts of climate change will make global problems such as drought, famine, flooding, disease, regional insecurity and population displacements worse, and seriously hinder poor countries’ efforts to tackle poverty.
To help lessen the effects of climate change, we must reduce the level of greenhouse gases emitted. This can be achieved by generating our energy from sources that emit low or even zero levels of greenhouse gases, such as renewable energy. We can also make sure that we use energy as efficiently as possible. However, these are not either/or options.
As well as countering the effects of climate change, using renewable energy will also help to reduce other forms of environmental and social damage arising from the use of fossil fuels. For example, it will minimise the impact of acid rain on water and forest ecosystems, or reduce localised air pollution and its subsequent health impacts.
Using indigenous renewable sources of energy will reduce our dependence on imported fossil fuels and will bring diversity and security of supply to the UK’s energy infrastructure, as well as helping to improve the environment and minimise the impact of climate change.
Renewable energy use
Renewable energy flows involve natural phenomena such as sunlight, wind, tides and geothermal heat. Each of these sources has unique characteristics which influence how and where they are used.
The majority of renewable energy technologies are directly or indirectly powered by the Sun. The Earth-Atmosphere system is in equilibrium such that heat radiation into space is equal to incoming solar radiation, the resulting level of energy within the Earth-Atmosphere system can roughly be described as the Earth's 'climate.' The hydrosphere (water) absorbs a major fraction of the incoming radiation. Most radiation is absorbed at low latitudes around the equator, but this energy is dissipated around the globe in the form of winds and ocean currents. Wave motion may play a role in the process of transferring mechanical energy between the atmosphere and the ocean through wind stress. Solar energy is also responsible for the distribution of precipitation which is tapped by hydroelectric projects, and for the growth of plants used to create biofuels.
Environmental and social considerations
While most renewable energy sources do not produce pollution directly, the materials, industrial processes, and construction equipment used to create them may generate waste and pollution. Some renewable energy systems actually create environmental problems. For instance, older wind turbines can be hazardous to flying birds.
Another environmental issue, particularly with biomass and biofuels, is the large amount of land required to harvest energy, which otherwise could be used for other purposes or left as undeveloped land. However, it should be pointed out that these fuels may reduce the need for harvesting non-renewable energy sources, such as vast strip-mined areas and slag mountains for coal, safety zones around nuclear plants, and hundreds of square miles being strip-mined for oil sands.
Though a source of renewable energy may last for billions of years, renewable energy infrastructure, like hydroelectric dams, will not last forever, and must be removed and replaced at some point. Events like the shifting of riverbeds, or changing weather patterns could potentially alter or even halt the function of hydroelectric dams, lowering the amount of time they are available to generate electricity.
Although geothermal sites are capable of providing heat for many decades, eventually specific locations may cool down. It is likely that in these locations, the system was designed too large for the site, since there is only so much energy that can be stored and replenished in a given volume of earth. Some interpret this as meaning a specific geothermal location can undergo depletion, and question whether geothermal energy is truly renewable. The government of Iceland states It should be stressed that the geothermal resource is not strictly renewable in the same sense as the hydro resource. It estimates that Iceland's geothermal energy could provide 1700 MW for over 100 years, compared to the current production of 140 MW.