" Determined to address the nation's power challenge, the federal government of Nigeria, through the Nigerian Electricity Regulatory Commission (NERC), has signed into effect regulations for two critical licence types that would allow independent interests to generate and distribute power."
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Wednesday, March 14, 2012
New SA wind atlas
Thompson said that the atlas, which is part of the Wind Atlas for South Africa (Wasa) project, would be a useful tool for comparison and identification of potential sites for future wind turbine projects.
The first atlas covered the areas seen as the most promising for harnessing wind energy, but in future it was hoped to extend this to the rest of South Africa and possibly neighbouring countries.
“Some of you may wonder as to what a wind atlas has to offer South Africans when the country is faced with the triple challenges of unemployment, inequality and poverty. Let me respond by stating upfront that we cannot achieve success in responding to this triple challenge unless we diversify our energy sources and incorporate environmentally benign energy resources such as wind,” said Thompson.
The project was a collaboration between the South African National Energy Research Institute, the University of Cape Town Climate System Analysis Group, the Council for Scientific and Industrial Research (CSIR), the South African Weather Service and the Technical University of Denmark’s (DTU’s) department of wind energy.
Funding for the project, which had to date cost R22-million, was provided by the Department of Energy, the United Nations Development Programme – Global Environment Facility and the Danish Embassy in South Africa.
Using 30 years of meteorological global reanalysis data, a mesoscale climate model with a 5 km x 5 km resolution had been created in order to generate the wind atlas, explained the DTU’s Jens Hansen.
The model had been verified against the ten actual wind measurement stations, which had been in operation since August 2010, with the stations measuring the wind speeds at a height of 80 m above ground level.
Hansen said the correlation between the atlas and real measurements was pleasing. “This is world class, there is nowhere in the world that has a better wind atlas than this one,” he said.
Hansen said that the data from the Wasa project was freely available on a website, which the CSIR hosts, and interest in the project was high from both local and international users. The website already had 444 registered users from 37 different countries with over 16 000 downloads having taken place.
The atlas should enable prospective wind farm developers of all sizes to obtain free modelled wind measurement data that could be used together with commercial wind resource software. This would allow initial assessment of the viability of developing a wind farm in a chosen area, after which developers could carry out more detailed studies.
Hansen, however, noted that this was not the first wind atlas created for South Africa, with a previous atlas having being created by Dr Kilian Hagemann, who also attended the launch. However, Hansen said the new atlas was the first produced by a verified method created during the 1980s at the DTU.
Source....
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Monocrystalline vs Polycrystalline Photovoltaic Cells
Basic Anatomy of a PV cell
A lump of pure silicon
The main ingredient in most photovoltaic cells is silicon – the same element that makes computer chips possible. Silicon is the second most abundant element in the Earth’s crust, but unfortunately it is normally found in the form of silica (the chemical symbol for silica is SiO2) – you might know it as sand.
Various methods exist to extract the pure silicon, but the most common is carbothermic reduction, where the silica is heated to 1700°C in the presence of carbon. As the silicon cools it forms crystals.
The speed at which the silicon cools is one of the critical factors that determine the crystal size: the slower the silicon cools, the larger the crystals. With care the silicon can be extracted as one large crystal. As you might imagine, that’s more difficult, which means it’s more expensive.
The difference between monocrystalline vs polycrystalline solar cells is simply that one is produced from a single crystal of silicon and the other is produced from a piece of silicon consisting of many crystals.
Practical Differences
So what is the impact on cell performance?
Since polycrystalline cells contain many crystals, they have a less perfect surface than monocrystalline cells. This means that they absorb slightly less solar energy and produce slightly less electricity per square metre. On the plus side, the process of creating the silicon for a polycrystalline cell is much simpler, so these cells are generally cheaper per square metre.
On balance, the cost of monocrystalline vs polycrystalline based panels per Watt of power output works out about the same, but the polycrystalline panels will be slightly larger than equivalent monocrystalline panels. This is generally not a problem unless you have a very limited area available for the installation, in which case you will want to maximise the power output per square metre.
Monocrystalline and polycrystalline can also look different. Monocrystalline cells will usually have a perfectly uniform appearance, but polycrystalline cells will appear “grainy” – think of how a granite worktop looks and you’ll get the idea. From a distance this will not be noticeable, so if they are going on your roof this is unlikely to worry you.
So which should I choose?
At the end of the day, unless you are very space constrained, your choice of panel will probably be dictated by factors other than whether they are made up of mono or polycrystalline cells.
The price per Watt is an important factor, and that is largely unaffected by the choice of monocrystalline versus polycrystalline cells. In some circumstances, the area available for the installation may be a factor that pushes you to go for monocrystalline cells.
But the most important thing is to make sure that you choose a reputable installer and manufacturer. Your panels will most likely give you many years of trouble free operation, but for your own peace of mind you will probably want to choose a manufacturer that is likely to be around for long enough to honour the terms of the guarantee – which may be up to 25 years!
Source...
A lump of pure silicon
The main ingredient in most photovoltaic cells is silicon – the same element that makes computer chips possible. Silicon is the second most abundant element in the Earth’s crust, but unfortunately it is normally found in the form of silica (the chemical symbol for silica is SiO2) – you might know it as sand.
Various methods exist to extract the pure silicon, but the most common is carbothermic reduction, where the silica is heated to 1700°C in the presence of carbon. As the silicon cools it forms crystals.
The speed at which the silicon cools is one of the critical factors that determine the crystal size: the slower the silicon cools, the larger the crystals. With care the silicon can be extracted as one large crystal. As you might imagine, that’s more difficult, which means it’s more expensive.
The difference between monocrystalline vs polycrystalline solar cells is simply that one is produced from a single crystal of silicon and the other is produced from a piece of silicon consisting of many crystals.
Practical Differences
So what is the impact on cell performance?
Since polycrystalline cells contain many crystals, they have a less perfect surface than monocrystalline cells. This means that they absorb slightly less solar energy and produce slightly less electricity per square metre. On the plus side, the process of creating the silicon for a polycrystalline cell is much simpler, so these cells are generally cheaper per square metre.
On balance, the cost of monocrystalline vs polycrystalline based panels per Watt of power output works out about the same, but the polycrystalline panels will be slightly larger than equivalent monocrystalline panels. This is generally not a problem unless you have a very limited area available for the installation, in which case you will want to maximise the power output per square metre.
Monocrystalline and polycrystalline can also look different. Monocrystalline cells will usually have a perfectly uniform appearance, but polycrystalline cells will appear “grainy” – think of how a granite worktop looks and you’ll get the idea. From a distance this will not be noticeable, so if they are going on your roof this is unlikely to worry you.
So which should I choose?
At the end of the day, unless you are very space constrained, your choice of panel will probably be dictated by factors other than whether they are made up of mono or polycrystalline cells.
The price per Watt is an important factor, and that is largely unaffected by the choice of monocrystalline versus polycrystalline cells. In some circumstances, the area available for the installation may be a factor that pushes you to go for monocrystalline cells.
But the most important thing is to make sure that you choose a reputable installer and manufacturer. Your panels will most likely give you many years of trouble free operation, but for your own peace of mind you will probably want to choose a manufacturer that is likely to be around for long enough to honour the terms of the guarantee – which may be up to 25 years!
Source...
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