In recent years renewables have become increasingly central in the debate on the quest for energy sources that are alternative to crude oil and other fossil fuels. Yet, there is still some confusion about what renewables are, what their potential is and in which proportion they are actually being employed globally.
We can make a distinction between the definition of clean energy sources and renewables. In the first group we include energy sources that do not produce polluting emissions that impact climate. Nuclear power and renewables themselves are clean energy sources. In fact, nuclear can be considered clean energy as reactors do not produce carbon emission, nevertheless materials used for the nuclear energy technology are not renewable (i.e. uranium). The definition of renewable focuses on its characteristic to be theoretically inexhaustible, being replenished by nature; biomass, wind power, solar power, hydropower and geothermal are renewable sources. Traditional biomass is the most common and the most used renewable source of energy. It generates power from the combustion of organic material that has not been submitted to any process of fossilization, for example residues from forestry and agriculture, such as wood. From biomass, another category of renewables is derived: biofuels. These include ethanol, obtained from corn and soybeans, biodiesel from oil palms and biogas, derived from organic waste.
Renewables are traditionally opposed to fossil fuels like petroleum, coal and natural gas, as these contain high amount of carbon that they release during combustion under the form of greenhouse gas emissions. The latter have been associated with climate change and global warming.
Renewables can be efficiently employed in three sectors crucial to developed and developing economies worldwide: power generation, heating and cooling, and transport.
In order to promote policies supporting the use of renewable energy across the world, the Renewable Energy Policy Network for the 21st Century (REN21) was established in 2004 as a global network that involves several actors from governments, civil society, private sector and academia. Since 2005, REN21 regularly releases a “Renewables Global Status Report” that analyses and provides updates on the overall situation of renewable energy worldwide, in terms of production, consumption, investment and policy.
The current status of renewable energy worldwide
Except for a short slow down due to the economic crisis that affected most developed countries in 2009, the energy consumption increased by 5.4% in 2010 and the global energy demand continues to increase year by year as an effect of global demographic growth and development needs, which lead to higher consumption.
In this overall energy scenario the use of renewables continued to grow reaching a share of 16% over the global energy consumption in 2009, as highlighted in the “Renewables 2011 Global Status Report”.
According to the latter, some countries’ energy performance reported a rapid increase in the use of renewable sources, particularly China, Germanyand the United States. In Europefor example, wind technology for power generation recorded very encouraging trends in 2010. In Denmark and Portugal more than 20% of the electricity demand was fulfilled using wind power, in Spain more than 15% and in Irelandmore than 10%.
Are we improving?
In two years, from 2008 to 2010, the annual overall investment in renewable energy has increased from US$ 130 billion to US$ 211 billion, according to the “Renewables 2011 Global Status Report”. In all the three sectors we mentioned earlier, the use of renewable energy grew and the costs of such technologies generally reduced allowing a bigger diffusion. More and more countries in recent years are implementing policies aimed at meeting renewable energy targets and are putting in place measures such as subsidies to promote biofuels over fossil fuels.
Why should we care about the use of renewables?
According to the United Nations’ Human Development Report 2011 the global carbon dioxide emissions have grown 112% since 1970. Increasing the share of renewables in the total energy production and consumption will help reduce the high carbon nature of the world economies and so the global greenhouse gas emissions.
Environmental degradation caused by emissions directly affects individuals in their everyday life. Air pollution, water pollution and global warming have important consequences on human health, such as respiratory diseases, immune system damages, heatstroke and cardiovascular disorders. Furthermore, in higher temperatures, vectors of infectious diseases spread faster.
The world population is also experiencing several other environmental concerns related to emissions. These are majorly responsiblefor climate change, which affects temperature, rainfall, sea level and risk of natural disaster. For most developed countries it will take longer to see the effects of climate change, because they often have lower average temperatures. However, in tropical areas the rise in temperatures is already having negative impacts on water availability, also causing decrease of rainfall necessary for agricultural production. Climate change and global warming have also been associated with the rapid rising of the sea level and a higher incidence of natural disasters such as cyclones, floods and tsunamis, that the media report more and more frequently.
New perspectives for our renewable future?
Research on new techniques for reducing the carbon emissions in the atmosphere involves different sectors and applications.
At the National Renewable Energy Laboratory, Colorado (United States), scientists are trying to obtain new biofuels out of liquefied algae. Currently biofuels are produced from land-based sources (soybeans, corn, palm oil…) and the quantity of spare land available for such cultivation can raise issues. Compared with petroleum, biofuels are advantageous as the sources for their production are still broadly available. Nevertheless, sustainability of biofuels production has been questioned with respect to the availability of another indispensable resource: water. Studies on the higher costs of biofuels’ production in terms of fresh water consumption, have pointed out that in some areas crops require abundant irrigation. This can represent an issue, for example in areas where rainfall is scarce. However, some tropical lands where oil palms and sugarcane grow (such as Indonesia and Brazil) receive copious rains, which make irrigation not necessary and reduce the water costs of biofuels’ production. Another significant impact of this energy source is the rising of food prices with negative consequences on poverty reduction, particularly in those countries that heavily rely on imports for food consumption (such as many countries inAfrica).
– Algae grow faster and their cultivation is not bound by seasonal cultivation time requirements;
– Algae contain more oil, so a specific quantity of algae can produce more oil than the correspondent quantity of biofuel’s crop;
– Algae don’t need fertile lands to be cultivated.
Nevertheless, the way algae oil is currently produced is still very expensive, and still some questions on potential disadvantages remain, particularly: what would be the environmental impact of broadening on a larger scale algae production?
Promotion of renewable and environment-friendly lifestyles, has led to an ambitious innovation experiment in Denmarkthat focuses on how to build carbon-neutral houses. The idea is to put together technologies that on the one side reduce the need for electricity and heating and on the other side fulfil the energy requirements of the house using solar power.
These are just some of the examples that can give us an idea of the advancements in renewable energy research and application. Where will we stand in the next years as per the achievement of our global renewable potential?
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 Debates about biomass question its classification among the clean energy sources. On the one hand, biomass can be considered to be CO2 neutral, as the CO2 emissions produced in the combustion process do not increase the CO2 level in the atmosphere, being the same quantity hat the living organism used as biomass has absorbed during its life-cycle. Nevertheless, on the other hand, the use of traditional biomass, broadly diffused in developing countries particularly among rural population for cooking and heating, has high social costs, such as health impacts from indoor air pollution and exacerbation of deforestation.
 Despite biofuels release carbon emissions during their combustion, they are considered as carbon neutral as the carbon dioxide they release is the same that has been absorbed during the lifecycle of the biomass from which they are originated.
 REN21, Renewables 2011 Global Status Report.
 United Nations Development Programme (UNDP), Human Development Report 2011.
 King and Webber, 2011. Quoted by David Schneider, “Biofuel’s Water Problem”, IEEE spectrum, volume 47, number 6, June 2010.
 D. Schneider, “Biofuel’s Water Problem”, IEEE spectrum, volume 47, number 6, June 2010.
 E.K. Hansen, “Home, Smart Home”, IEEE spectrum, volume 47, number 8, August 2010.