A previous article covered the use of nuclear power in the electricity generating industry and the new wave of nuclear plant construction with even Britain now saying that the nuclear route is the road to go to reduce CO2 and other emissions. The feasibility of another nuclear plant in the Cape is also being promulgated as the way to reduce that region's lack of electrical capacity. Besides nuclear, another revolution is the use of a myriad of forms of renewable energy and this article addresses the most common of these with emphasis on where South Africa is in terms of these green energy systems. Most countries have set themselves targets for green energy as a percentage of the total energy requirements and it is interesting to see how they are progressing. A major disadvantage is that most (if not all) of renewable energy schemes produce power at levels well above Eskom's current coal energy costs.
South Africa has no option but to follow the green energy (which includes nuclear) route. The Mail & Guardian (31 July 2006) points out that South Africa accounts for about half of the carbon emissions on this continent. It also indicates that South Africa produced 6,91 tonnes per person of fuel combustion carbon dioxide compared to the world average of 3,89 tonnes. The article lists the three biggest contributors to pollutants as Eskom, Sasol and the crude oil refineries. All nations are trying their best to follow the guidelines of the Kyoto Protocol and reduce carbon emissions and South Africa will have to do the same.
Hydropower
There is nothing new about the use of hydropower and in fact it was used centuries ago by farms in milling and later to produce electricity. Some countries are more amenable in structure to develop hydro projects (such as New Zealand) and there appears to be little more opportunity to use this in South Africa. On the African continent the planned Grand Inga project in the DRC is the single largest hydropower initiative in the world and its target capacity of 39 000 MW could form the base for an African power grid. But do not hold out hope as the project has been talked about for decades, although with Eskom now on board perhaps something might happen. There are also other possibilities for further hydropower projects in Africa, but where funding would come for these is unknown. It is believed that only about 4% of Africa's hydro potential is being exploited.
The country with the most hydroelectric projects on the go is China but remember some are based on the construction of new dams and the Three Gorges project displaced hundreds of thousands of people (so the 'green' aspect must be weighed against the negative effects). The Three Gorges plant has an installed capacity of 18 200 MW making it the largest hydropower station in the world. China is continuing with new hydroelectric projects and the latest to get approval for construction is the Baihetan station (12 000 MW) on the Jinsa River, an upstream branch of the Yangtze River. It will complement three other hydropower stations on the lower reaches of the river and on completion the four stations will have the total capacity to produce twice as much energy as the Three Gorges.
The Chinese government is taking the green route and has indicated that by 2020, 15% of the country's energy needs will come from renewable energy. China also has massive nuclear plans as well. The conclusion is that hydropower is still the largest contributor by far to renewable energy with larger facilities being able to generate as much power as two or three conventional coal fired power stations. Locally within South Africa, there is little potential to follow this route although Eskom may contribute to better utilisation and more power generation from Cahora Bassa and perhaps the Lesotho Highlands scheme which currently provides power to Lesotho.
South Africa only has two hydroelectric power stations at the Gariep (360 MW) and Vanderkloof (240 MW) dams. Protagonists suggest that South Africa could do more to promote small hydro schemes and fund and run them as public-private enterprises. According to one report these small schemes could provide up to 75 MW of power.
Solar power
The power potentially available from the sun is enormous and if harnessed effectively could power all the world's requirements for electricity. (A massive power plant in the Sahara Desert could do that on its own). However, solar power is available only during the hours of daylight and the only way to store that power at the moment is through the use of batteries, which has worked for small installations. (Pumped storage [see below] could also work as a storage mechanism for larger solar power plants).
Solar power has proved very successful in terms of small installations where in remote rural areas photovoltaic cell panels have been used to collect solar energy and convert it into electricity for use by schools and clinics, and even a small number of houses. It has also found wide acceptance in both South Africa and North America for heating water from roof mounted solar panels. An American commercial company has also extended its use into the retail environment with a system that generates 121 kW from solar panels mounted on the roof and car ports of the complex. India has gone the limited solar power route to address the problem of its 100 000 villages that cannot be connected to the grid for either technical or economic reasons.
Its acceptance for grid use has been slower although there is considerable development now. Just a few months ago the first solar power plant opened in the Czech Republic, albeit encouraged by subsidies and rebates which is a common stimulus worldwide. In the middle of the Mojave Desert in Southern California the world's largest commercial solar power plant is located which produces around 350 MW of electricity, claimed to amount to about 90% of the current commercial production of solar energy in the world (2005). This Solar Electric Generating System (SEGS) does not use photovoltaic technology but is rather thermal-based. At the foci of the mirrors is a tube filled with oil which can be heated to 750°F (399°C) which turns water into steam that drives a turbine to produce the electricity. As the last stages are conventional SEGS can be operated using gas when sunlight is not available. (There are nine similar plants operating in the Mojave Desert, two of them being 80 MW in size). The company that built SEGS has plans for a 1000 MW installation to be located in Israel's Negev desert to supply electricity to southern Israel. Another ambitious plan is to develop a 500 MW solar project northeast of Los Angeles with an option to expand to 850 MW. This plant will use Stirling dish technology to create electricity and would be the latter's first major application in commercial power generation. The Mojave Desert plant is being followed by a 64 MW thermal plant in Nevada which will make use of new receiver technology. It is expected to begin production of electricity in March next year. One of the other companies involved intends to increase its global production capability from 90 to some 200 MW per year.
In regard to photovoltaics another commercial company recently announced its intention to build an 11 MW plant in one of the sunniest areas of Portugal. This would become the world's largest solar photovoltaic plant. Australia has used dish concentrators and highly efficient PV detectors to produce 220 kW of power for the remote Anangu Pitjantjatjara aboriginal lands. This station is connected to a mini grid that services a number of communities. The advantage here is that as higher efficiency PV modules are developed they can be replaced in these systems leading to increased power output with the same infrastructure.
In southern Africa Botswana has just decommissioned an experimental PV system that supplied energy to a small village with 11 households, a school, clinic and streetlights for the past six years. But this is typical of the use of such power for small rural communities where there is no grid energy. Eskom is considering the use of solar power in the Northern Cape. It is not PV but thermal energy use and the plant will generate about 100 MW. During the night as in the USA it could be run on gas or oil.
In one recent report the total peak power of installed solar panels was quoted as 5300 MW as of the end of 2005. These figures apply only to PV generated power and including America's solar reflector plants would probably double this total. It serves as a benchmark however as to the minimal use of solar power as the current global consumption of power is considered to be about 13 TW.
Overall it appears that major investments will be made in solar power capacity over the next few years and the general consensus appears to be that the time is now right for the advancement of this technology. Even Germany, with its less than ideal weather has been installing smaller solar power plants and the business in the ideal 'desert' sites appears likely to explode. Increasing capacity will in the longer term lead to lower costs for solar power as the manufacture of components becomes more cost-effective through volume.
Wind power
Wind power is again nothing new and the Netherlands in particular used windmills centuries ago. More recently there has been widespread use of small windmills by farmers to pump water to irrigate crops or for livestock.
South Africa awakened to wind power in 2003 when Eskom's experimental wind farm at Klipheuwel became operational. The plant uses three types of turbines (600 kW, 750 kW and 1,75 MW) so as to look at different types of technology. These wind towers start to generate electricity at wind speeds of about 11 to 15 km/h, run at full power at wind speeds of between 47 and 57 km/h and have automatic shut down mechanisms operating at 90 km/h. Wind is unreliable and Eskom has found that the farm was capable of use for the following:
* 16% during peak times.
* 40% at standard times.
* 44% during off-peak periods.
The site was chosen for its acceptable wind speeds, proximity to Cape Town and an existing electricity distribution infrastructure so that it could be connected to the grid.
The second wind farm is at Darling and is the first independent power producer, Darling Wind Power. Located 70 km north of Cape Town the plan is for 10 1,3 MW wind turbines with the first stage being four, producing 5,2 MW of power. Although highly favoured by green lobbyists, wind power has major problems to overcome. One is that power delivery is erratic, while it would take 1000 of Darlings turbines to replace the output of Koeberg. A major advantage is that wind farms can be built quickly (about a year to produce a plant of 100 MW capacity). Eskom estimates that the practical usable wind resource on South Africa's coasts to be about 1000 MW. This is contested by Darling's owners who believe that the West coast alone could produce 10 000 MW. Darling Wind Power has already secured a 20 year contract to supply the City of Cape Town, and those who wish to use 'green' power will pay a premium on Eskom's rates.
Many countries particularly in Europe have wind farms. Belgium is the world wind power leader as it generates 18% of its energy requirements from the wind. In Japan the largest is Rokkashomura which supplies 30 MW of clean wind energy capacity to the Japanese grid. Another interesting fact is that in 1999 there were more than 11 500 wind turbines in California, which can generate enough power for a city as big as San Francisco.
Dr Maurice McDowell has many years’ experience as a technical journalist, editor, business manager and research scientist. His third party analyses of world-class companies and processes, as well as his insight into industry and technology trends are well respected.
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