Drying is one of the most important post harvest steps. It enhances the storage life of the crop products, minimizes losses during storage, and saves shipping costs. The drying process is the removal of water from the wet surface of the food. In this process, heat is transferred by convection and radiation to the surface of the produce. This heat raises the temperatures heat and evaporates the moisture from the exterior of the agricultural products, diffusing the interior moisture to the surface and replenishing the evaporated surface moisture. (more…)

Although technology change (usually involving an improvement in energy efficiency) is not inherently a geographic process, it does not occur uniformly over geographic space. Consequently, mathematical modeling and behavioral and innovation diffusion studies by geographers have improved our understanding of the pervasive phenomenon of technology energy efficiency change in energy markets. Similarly, creative government policies in Germany since 1990 have led to a faster rate of adoption of renewable energy sources, compared to the United States. (more…)

A combination of legislation and technology has helped clean up many of the world’s coal-burning plants. Both developed and developing countries have adopted increasingly stringent environmental regulations to govern emissions from coal-fired power plants. In the United States, all coal-fired power plants built after 1978 must be equipped with postcombustion cleanup devices to capture pollutants before they escape into the atmosphere. Cyclones, baghouses, and electrostatic precipitators filter out nearly 99% of the particulates. Flue gas scrubbers use a slurry of crushed limestone and water to absorb sulfur oxides from flue gas. The limestone reacts with the sulfur dioxide to form calcium sulfate, which may be used to produce wallboard. Staged combustion and low-NOx burners are used to burn coal to minimize NOx formation. Another strategy, selective catalytic reduction, reacts ammonia with NOx over a catalyst to produce nonpolluting nitrogen and water vapor.

Conventional coal-fired power plants capture pollutants from the flue gas after it leaves the boiler. Circulating fluidized bed (CFB) combustors capture most of the pollutants before they leave the furnace. Crushed coal particles and limestone circulate inside the CFB combustor, suspended by an upward flow of hot air. Sulfur oxides released during combustion are absorbed by the limestone, forming calcium sulfate, which drops to the bottom of the boiler. The CFB combustor operates at a lower temperature (14001F) compared to pulverized coal (PC) boilers (27001F), which also helps reduce the formation of NO x .

Precombustion coal cleaning is another strategy to reduce sulfur emissions by cleaning the coal before it arrives at the power plant. Sulfur in coal is present as pyrite (FeS2 ), which is physically bound to the coal as tiny mineral inclusions, and as ‘‘organic sulfur,’’ which is chemically bound to the carbon and other atoms in coal. Pyrite is removed in a coal preparation plant, where coal is crushed into particles less than 2 inches in size and is washed in a variety of devices that perform gravity-based separations. Clean coal floats to the surface, whereas pyrite and other mineral impurities sink. Additional cleaning may be performed with flotation cells, which separate coal dust from its impurities based on differences in surface properties. Precombustion removal of organic sulfur can be accomplished only by chemical cleaning. So far, coal combustion emissions and chemical cleaning has proved to be too costly, thus flue gas scrubbers are often required to achieve near-complete removal of sulfur pollutants.

The tightening of environmental regulations is likely to continue throughout the world. In the United States, for example, by December 2008, it is anticipated that coal-fired power plants will have to comply with maximum emission levels for mercury. Emissions of mercury and other trace metals, such as selenium, are under increasing scrutiny of coal combustion emissions because of suspected adverse effects on public health.

Coal is sometimes combusted with waste material as a combined waste reduction/electricity production strategy. The disposal of waste from agriculture and forestry (biomass), municipalities, and hospitals becomes costly when landfill space is limited. Some wastes, particularly biomass feedstock, are combustible, but their low energy density (compared with coal) limits their use as an electricity production fuel. Blending coal with these fuels provides an economical method to produce electric power, reduce waste, and decrease coal plant emissions. Most wood wastes, compared to coal, contain less fuel nitrogen and burn at lower temperatures. These characteristics lead to lower NO x formation. In addition, wood contains minimal sulfur ( o 0.1% by weight) and thus reduces the load on scrubbers and decreases scrubber waste biomass.

Numerous electric utilities have demonstrated that 1–8% of woody drying biomass can be blended with coal with no operational problems. Higher blends may also be used, but require burner and feed intake modifications as well as a separate feed system for the waste fuel. Cofiring in fluidized bed boilers may avoid some of these drawbacks, but the economics of co-firing are not yet sufficiently attractive to make it a widespread practice.

Gasification is a thermo chemical process that has been exploited for more than a century for converting solid feedstocks to gaseous energy carriers. The first gasifier patent was issued in England at the end of the 18th century and producer gas from coal gasification was mainly used as lighting fuel throughout the 19th century. At the turn of the 20th century, the main use of producer gas, obtained essentially from coal, switched to electricity generation and automotive applications via internal combustion engines. The use of producer gas was gradually supplanted by the use of higher energy density liquid fuels and as a result confined to areas with expensive or unreliable supplies of petroleum fuels. (more…)

Currently, site reclamation is planned for during the permitting process and is incorporated into the mining operation. However, this was not always the case. Many mine sites were legally abandoned in an un-reclaimed or poorly reclaimed condition because mining was completed before environmental regulations went into effect. These abandoned mines are scars on the landscape and cause most of the water pollution attributed to mining. These old mines are considered abandoned because, in most countries, no one is legally required to reclaim the land or to treat the water. A similar problem occurs at mine sites that are or were operated by companies that have gone bankrupt. (more…)

At present, in the United States and worldwide, motor vehicles are fueled almost exclusively by petroleum based gasoline (or reformulated gasoline) and diesel fuels. Since the first oil price shock in 1973, efforts have been made to seek alternative fuels to displace gasoline and diesel fuels and achieve energy and environmental benefits. Some of the alternative fuels that have been researched and used are liquefied petroleum gas (LPG), compressed natural gas (CNG), liquefied natural gas (LNG), methanol (MeOH), dimethyl ether (DME), Fischer– Tropsch diesel (FTD), hydrogen (H 2 ), ethanol (EtOH), biodiesel, and electricity. Production processes associated with gasoline, diesel, and each of these alternative fuels differ. (more…)

The development of the ‘‘new’’ wind and solar technologies is of great importance for the future contribution of RESs to energy supply. Although the present wind and solar technology contribution of 0.4% to total primary energy consumption per capita is still very small, the growth of these industries has been considerable in the past 6 to 8 years. Today they provide 10 times the energy of 10 years ago. Wind energy shows the most remarkable growth dynamics; its contribution is now reaching energetically relevant dimensions. (more…)

Energy exists in many forms. Some of energy forms are simple to use and identify as energy. But other forms of energy can not be seen until the energy released. Some forms of energy like light and sound, they carry energy from one place to another. There are also vibrating objects that carry the kinetic energy that makes the sound. The energy passes through the wave where the wave was originated. The higher the wave, it gives more energy. Light is also one form of energy. A light beam or light ray brings out energy from where there was light. This energy is often referred to as radiation energy. (more…)

The outlook for reductions in future energy use is necessarily based on the potential for increased technological and operational efficiencies. In this section, the outlook for such improvements in large commercial aircraft over the next quarter century is examined.

Engine efficiencies may be improved by between 10 and 30% with further emphasis on moving more mass through engines that operate at higher temperatures and higher pressures. A continuation of the historical trend would lead to a 10% increase in L/D by 2025, and further improvements in the reduction of parasitic drag may extend these savings to perhaps 25%. However, the technologies associated with these improvements have weight and noise constraints that may make their use difficult. (more…)

“Spain has great potential but lack geothermal legislation and investment.” Besides being clean, renewable and friendly, easily manageable, which contributes to security of energy supply.

However, like other renewable energy sources, requires the development of sustainable energy technology push policies and efficient and environment economic support. (more…)