Access to cheap energy has become essential to the functioning of modern economies. However, the uneven distribution of fossil fuel supplies among countries, and the critical need to widely access energy resources, has led to significant vulnerabilities. Threats to global energy security include political instability of energy producing countries, manipulation of energy supplies, competition over energy sources, attacks on supply infrastructure, as well as accidents and natural disasters.
The International Energy Agency's World Energy Outlook 2006 concludes that rising oil demand, if left unchecked, would accentuate the consuming countries' vulnerability to a severe supply disruption and resulting price shock. Renewable biofuels for transport represent a key source of diversification from petroleum products. Biofuels from grain and beet in temperate regions have a part to play, but they are relatively expensive and their energy efficiency and CO2 savings benefits, are variable. Biofuels from sugar cane and other highly productive tropical crops are much more competitive and beneficial. But all first generation biofuels ultimately compete with food production for land, water, and other resources. Greater efforts are required to develop and commercialize second generation biofuel technologies, such as biorefineries and ligno-cellulosics, enabling the flexible production of biofuels and other products from non-edible plant materials.
According to the International Energy Agency (IEA), cellulosic ethanol commercialization could allow ethanol fuels to play a much larger role in the future than previously thought. Cellulosic ethanol can be made from plant matter composed primarily of inedible cellulose fibers that form the stems and branches of most plants. Dedicated energy crops, such as switchgrass, are also promising cellulose sources that can be produced in many regions of the United States.
For those countries where growing dependence on imported gas is a significant energy security issue, renewable technologies can provide alternative sources of electric power as well as displacing electricity demand through direct heat production. The IEA suggests that the direct contribution that renewables can make to domestic or commercial space heating and industrial process heat deserves closer attention. Heat from solar, and geothermal sources, as well as heat pumps, is increasingly cost effective but often falls through the gap between government programmes that promote public awareness and provide incentives for renewable electricity and energy efficiency.
Solar heating systems are a well known technology and generally consist of solar thermal collectors, a fluid system to move the heat from the collector to its point of usage, and a reservoir or tank for heat storage. The systems may be used to heat domestic hot water, swimming pools, or homes and businesses. The heat can also be used for industrial process applications or as an energy input for other uses such as cooling equipment. In many warmer climates, a solar heating system can provide a very high percentage (50 to 75%) of domestic hot water energy.
The deployment of renewable technologies usually increases the diversity of electricity sources and, through local generation, contributes to the flexibility of the system and its resistance to central shocks. The IEA suggests that attention in this area has focused disproportionately on the issue of the variability of renewable electricity production. However, this only applies to certain renewable technologies, mainly wind power and solar photovoltaics, and its significance depends on a range of factors which include the penetration of the renewables concerned, the balance of plant on the system, the wider connectivity of the system, and the demand side flexibility. Variability will rarely be a barrier to increased renewable energy deployment. But at high levels of penetration it requires careful analysis and management, and any additional costs that may be required for back-up or system modification must be taken into account.