Coal sector of South Africa

Coal is the primary fuel produced and consumed in South Africa and is one of the country's largest sources of foreign exchange. Coal reserves constitute 5.4% of the world’s reserves, all hard coal, with no lignite.

The coal mining sector has become the second largest component of the South African mining sector with annual coal sales higher than gold.

The country's coal reserves are mainly bituminous, with a relatively high ash content of about 45%, and low sulphur content of about 1%. South Africa's recoverable coal reserves, estimated at 54.6 billion short tons (Bst), are the world's seventh largest, representing approximately 5% of the world reserves.

South Africa’s hard coal is classified as so-called ‘Gondwana’ coal, comparatively rich in ash and must be prepared, at least for exporting. This coal has limited, if any, coking properties and to that extent, is low to medium volatile at 16–29%. It is relatively (<>

Africa has been organised by landowner mining, that is, mining rights have remained with the owner of the land. State control merely took the form of a statutory approval procedure and mining supervision, so that no royalty had to be paid to the state. Wide areas of land are owned by big mining companies, and this is also true of the country’s coal deposits. In the meantime, the government is aiming at profound change in this sector. The government and mining companies recently agreed a new draft on mining laws under which, all of the country’s natural resources are transferred to state ownership. Present and future mining companies must re-apply for their mining rights, the issue of which is to be associated with statutory stipulations; deposits which are not exploited at present or whose short-term exploitation has not been applied for by the landowner can now be granted to other interested parties.

The idea is to remove the frequently occurring decade-old blockage of unused natural resources on the part of landowners, and to provide fresh mining and employment.

There are 11 coalfields in all, extending across 19 regions from the border with Botswana in the Northern Province, via the provinces Gauteng, Mpumalanga, and Freestate, to KwaZulu-Natal in the Southeast, with 83% of the reserves concentrated in the mining areas of Witbank, Highveld, Vereeniging/Sasolburg, Ermelo and Waterberg. While the first four mining areas are relatively close to the coast of the Indian Ocean, namely, just under 600 km by rail; the distance from the Waterberg area, located at the Botswana border, doubles to 1,120 km.

Among the chief mining regions are Witbank, Highveld, Vereeniging/Sasolburg, Ermelo and Waterberg, areas with a current 98% share in total output. In 2001, the total 77 collieries operated 66 underground mines and 37 opencast pits. They mined 54% or 124 Mt of total underground output and 46% or 104 Mt in surface operations. The opencast pits reach depths down to 60 m, with maximum of five seams, though only two–three are usually suitable for dragline operations, which account for two-thirds of opencast pit output. Truck and shovel mining, by contrast, is mainly used in the multi-seam mining area of Waterberg. Deposit sections whose mining in opencast pits is uneconomical are often exploited in underground mines. The flat seams lend themselves to extraction at depths of hardly more than 200 m.

The mining technique deployed here is board and pillar, which accounts for over 90% of underground mine production, while long walling is only used in exceptional cases. In board and pillar operations, coal extraction is dominated by the continuous miner, but mechanised drilling and blasting, too, are still used occasionally.

Introduction to Solar Photovoltaics

Solar energy is usually divided into two categories, although they can be employed together in solar installations.

Solar thermal energy is generated from heat and employs heat directly to heat water, the ambient temperature in buildings, or steam to power electricity generators.

Solar photovoltaic electricity is generated from light, employing photovoltaic modules or cells, which convert sunlight into electricity using cells with semi conductors.

Solar thermal technologies use the sun’s heat. They include non-grid solar thermal technologies; water heating systems, solar cookers, solar drying applications and solar thermal building designs. These technologies help to conserve energy in heating and cooling applications. Solar thermal devices use direct heat from the sun, concentrating it to produce heat at useful temperatures. As with many other advances in the energy sector, modern solar thermal industry began with the oil embargo of 1973-1974 and was strengthened with the second embargo in 1979. In the early 1980’s, a 354 MW solar power plant was built in the Mojave Desert, in California. The heat contained in solar rays, concentrated by reflecting troughs and raised to 400^oC, produces steam that runs a conventional power generator. When the sun is not shining, the plant switches to natural gas. The latest generation of this type of plant incorporates new engineering solutions and new scientific principles such as non-imaging optics, which makes it possible to build much more efficient concentrators at lower costs. Solar thermal technology has many applications both for grid-connected power generation, in isolated locations where grid connected electricity is not viable, and in domestic and commercial situations.

Solar photovoltaics or solar PV are solid-state semiconductor devices that convert light directly into electricity. Solar PV’s are mostly made of silicon with traces of other elements and are closely related to transistors, LEDs and other electronic devices. The electricity is direct current but can be converted to alternating current or stored for later use.

Bell Telephone researchers discovered the PV cell in 1954 when examining the sensitivity of a properly prepared silicon wafer to sunlight. From the late 1950s, PVs were used to power US space satellites, which generated commercial applications for PV technology. The simplest PV systems power many of the small calculators and watches in everyday use. More complex systems provide electricity in off-grid applications and generate electricity for the grids.

Advanced technology is required to manufacture PV cells and modules, but the cells themselves are simple to use. PV modules are usually low-voltage DC devices with no moving or wearing parts, although arrays of PV modules can be wired for higher voltages. Once installed, a PV array does not require much maintenance except for an occasional cleaning, and even that is not imperative. Most PV systems contain storage batteries, which require some water and maintenance similar to that required by the battery in a car.

A solar cell consists of layers of semiconductor materials with different electronic properties. In a typical solar crystalline silicon cell, most of the material is silicon. The silicon is doped with a small quantity of boron to give it a positive or p-type character. A thin layer on the front of the cell is doped with phosphorous to give it a negative or n-type character. The interface between these two layers contains an electric field and is called a junction. Light consists of particles called photons and when the light hits the solar cell, some of the photons are absorbed in the region of the junction, freeing electrons in the silicon crystal. If the photons have enough energy, the electrons are able to overcome the electric field at the junction and are free to move through the silicon and into an external circuit. As they flow through the external circuit they give up their energy as useful work (turning motors, lighting lamps, etc.) and return to the solar cell. The photovoltaic process is entirely solid-state and self-contained; there are no moving parts and no materials are consumed or emitted.