1.1Global Energy Production and Resources
The world primary energy demand, estimated at 560·1018 J in 2012, has been projected to increase 50% by 2040 under the International Energy Agency’s (IEA’s) Current Policies Scenario (International Energy Agency 2013), an increase primarily driven by rapid world population growth and the continuous economic development of emerging markets. China is the driving force of energy demand growth, accounting for almost 35% of the projected increase. However, despite the steady upward trajectory of energy demand, a slowdown in demand growth has been observed over the last few years, mainly as a result of energy efficiency gains and structural changes in the global economy that favor less energy-intensive activities. Comprehensive data for 2012 reveal a growth rate of 1.7%, which is slightly lower than the 1.9% growth rate obtained in 2011 (International Energy Agency 2013).
Today, approximately 82% of the rapidly expanding global energy demand is satisfied by fossil fuels. Despite the convenience of their use, fossil fuels represent a major source of anthropogenic CO2 emissions and other types of pollution, all of which cause significant environmental impact and pose serious adverse effects to public health. Despite the CO2-cutting measures announced by many counties after the 2015 United Nations Climate Change Conference, emissions are expected to rise from 31.6 Gt in 2012 to 38 Gt in 2040 according to the IEA’s New Policies Scenario (International Energy Agency 2013). Furthermore, fossil fuel reserves and resources are finite and unevenly distributed across the globe, raising additional concerns about the security of energy supply.
Meeting the rapidly growing energy demand while curbing anthropogenic CO2 emissions to meet currently established targets, avoiding the fast depletion of the fossil fuel reserves, and ensuring the security of energy supply poses a serious challenge to sustainable development and urges the need for the introduction of carbon-neutral fuels and cost-efficient deployment of renewable energy resources. Accounting for 21% of global electricity production, and predicted to further increase to 33% by 2040 according to the IEA’s New Policies Scenario (International Energy Agency 2013), renewables have acquired an increasingly important role in the power generation sector and in the promotion and widespread integration of renewable energy sources across the global energy economy.
Unlike the power generation sector, heat generation for the buildings and industrial sectors is almost totally dependent on fossil fuels. More than 40% of the natural gas primary energy supply and approximately 20% of the coal primary supply and oil primary supply are used for heat production, thereby being responsible for ~39% of global energy-related CO2 emissions. Despite the fact that heat demand accounts for almost 80% of the total energy demand in the buildings sector and that heat production processes remain a major source of anthropogenic CO2 emissions, the share of renewables (including biomass) in global heat production reached only 25% in 2012, thus leaving tremendous potential for improvement. Solid biomass currently accounts for 68.7% of total renewable heat generation and is the most dominant energy source as it is widely used for heating and cooking in developing countries. However, concerns about local pollution from biomass use, low...
