Sustainable energy systems - chapter introduction  (Page 13/7)

Learning objectives

After reading this module, students should be able to

• outline the history of human energy use
• understand the challenges to continued reliance on fossil energy
• understand the motivations and time scale for transitions in energy use

Introduction and history

Energy is a pervasive human need, as basic as food or shelter to human existence. World energy use has grown dramatically since the rise of civilization lured humans from their long hunter-gatherer existence to more energy intensive lifestyles in settlements. Energy use has progressed from providing only basic individual needs such as cooking and heating to satisfying our needs for permanent housing, farming and animal husbandry, transportation, and ultimately manufacturing, city-building, entertainment, information processing and communication. Our present lifestyle is enabled by readily available inexpensive fossil energy, concentrated by nature over tens or hundreds of millions of years into convenient, high energy density deposits of fossil fuels    that are easily recovered from mines or wells in the earth's crust.

Sustainability challenges

Eighty five percent of world energy is supplied by combustion of fossil fuels. The use of these fuels (coal since the middle ages for heating; and coal, oil and gas since the Industrial Revolution for mechanical energy) grew naturally from their high energy density, abundance and low cost. For approximately 200 years following the Industrial Revolution, these energy sources fueled enormous advances in quality of life and economic growth. Beginning in the mid-20th Century, however, fundamental challenges began to emerge suggesting that the happy state of fossil energy use could not last forever.

Environmental pollution

The first sustainability challenge to be addressed was environmental pollution, long noticed in industrial regions but often ignored. Developed countries passed legislation limiting the pollutants that could be emitted, and gradually over a period of more than two decades air and water quality improved until many of the most visible and harmful effects were no longer evident.

Limited energy resources

The second sustainability issue to be addressed has been limited energy resources. The earth and its fossil resources are finite, a simple fact with the obvious implication that we cannot continue using fossil fuels indefinitely. The question is not when the resources will run out, rather when they will become too expensive or technically challenging to extract. Resources are distributed throughout the earth's crust – some easily accessible, others buried in remote locations or under impenetrable barriers. There are oil and gas deposits in the Arctic, for example, that have not been explored or documented, because until recently they were buried under heavy covers of ice on land and sea. We recover the easy and inexpensive resources first, leaving the difficult ones for future development. The cost-benefit balance is usually framed in terms of peaking – when will production reach a peak and thereafter decline, failing to satisfy rising demand, and thus create shortages? Peaks in energy production are notoriously hard to predict because rising prices, in response to rising demand and the fear of shortages, provide increasing financial resources to develop more expensive and technically challenging production opportunities.