What is renewable energy?
Renewable energy sources are derived principally from the power of the sun’s
radiation. There are also non-solar renewables, namely tidal energy and geothermal energy. Solar power, both in the form of direct solar radiation and indirect forms such as wind, water and bioenergy, was the energy source which early human societies were based on. Prior to the industrial revolution, these sources were virtually the only forms of energy used by man. During the past 150 years, modern civilisation has become increasingly dependent on fossil fuels such as coal, oil and natural gas. These are finite resources which by their nature are limited in their availability into the longer term. Their combustion releases carbon dioxide into the atmosphere which is a key contributor to global warming. The various forms of renewable energy generally have lower environmental impacts than fossil fuel and they are naturally renewed providing the opportunity to provide energy indefinitely. They contribute to global primary energy demand in three main sectors; electricity production, heat and cooling, and transport.
The term alternative energy refers to energy sources, which create less
environmental damage and pollution than fossil fuels, and offer an alternative
to non renewable resources.
Sustainable energy is a term that is used to cover both renewable energy and
the rationale use of energy (RUE). The rational use of energy is the efficient
and effective use of energy independent of where the energy comes from.
Sustainable energy in its broader context can be defined as energy providing
affordable, accessible and reliable energy services that meet economic, social
and environmental needs within the overall developmental context of the
society for which the services are intended, while recognising equitable
distribution in meeting those needs.
Energy Supply and Use
Energy supply and consumption has increased steadily across the globe in
recent years and is set to continue with the continued growth of the world’s
population and the increased energy needs of existing and developing
economies such as China and India. In the period between 1973 and 2003,
Total Primary Energy Supply (TPES) rose from 6,034 million tonnes of oil
equivalent (Mtoe) to 10,579 Mtoe, an increase of almost 70% (McQuade,
2005). Table 3.1 details this growth by individual energy source. It shows a fall
in the use of oil over that time, while there has been a significant rise in the
use of natural gas and nuclear power. Overall, the percentage share of
renewables and waste has declined slightly.
It is clear from the figures above that the world is heavily dependant on fossil
fuels for its energy requirements. The question of when these finite resources
are likely to run out is an important issue when studying renewable energy. At
current rates of use, it has been estimated (BP, 2003) that proven coal
reserves should last for about 200 years, oil for approximately 40 years and
natural gas for 60 years. The availability of liquid fuels, however, is set to peak
between 2005 and 2015.
This peak in liquid fuels has been referred to by many commentators as “peak oil”. In a recent publication commissioned by the Irish Semi State body
“Forfás”, the issue of peak oil and its potential impacts on Ireland were
analysed. The study explained that “peak oil” is not so much a potential future
energy crisis so much as a “liquid fuels” crisis. It is expected that as global oil
supply declines and demand increases, there will be significant impacts on the
world’s economies, especially for global and national transportation networks