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ELR Electrical Engineering Support Services cc.
Leslie Martin (Technical and operations manager)
mobile: 082 922 2443
fax: 086 536 7417
web site: www.elr-
1. Increasing electricity prices.
For decades South Africans received subsidised, cheap electricity. There was a time that we paid some of the lowest electricity rates in the world, but things are changing and we have started paying a lot more for electricity in recent years. Indications are that this trend is going to continue and we’ll probably have to dish our more to contribute to Eskom’s Capital Expenditure Fund so that they could repay the loans for the new power stations and power lines that they are currently building.
1. Reduce environmental impact
Currently, Eskom and South Africa for that matter still relies heavily on fossil fuel (coal to be more specific) to generate our electrical power. About 77% of South Africa’s energy needs are directly converted from coal. At the moment Eskom is building two new coal fired power stations (with a total combined output capacity of about 9600MW). Although using fossil fuel, as a means of generating electrical power, has certain benefits the disadvantageous outweighs these benefits especially when considered from an environmental perspective.
Coal gives off Carbon Dioxide (CO2) when burned and subsequently contributes to the green house effect, which is believed to be the main contributing factor of the global warming phenomena. In addition the burning coal also produces Sulphur Dioxide that forms acid rain. It is given that a 1000MW coal fired power station releases 7.1 million tonnes of CO2 annually. Currently Eskom has an installed coal fired power generation capacity of 37.7 GW (Giga Watts) which translates to 267.5 million tonnes of CO2 per year (based on the assumption that all coal fired power plants operated continuously for one year).
2. From an engineering perspective
Complex processes are involved in the energy conversion process where chemical energy (stored in the coal) is converted to electrical energy. Coal fired power stations are thermal plants that generates electricity by heating water and steam to more than 500⁰C at pressures of up to 20 MPa. Switching these power plants on and off and cyclic load requirements places large stresses on the boiler and steam parts. In addition corrosion is another life shortening factor in the combustion areas of the boilers. The maximum life expectancy of thermal plants is therefore about thirty to fourty years (assuming that regular and efficient maintenance activities are conducted). Eskom’s existing coal fired power stations were build between the 1960’s and 1990’s, which means that they are between 20 and 50 years old. Eskom has managed to extend the life of most of its old coal fired power stations by introducing costly refurbishment projects. As these plants grow older they have to be taken out of service as progressively more maintenance has to be carried out. The running costs increases while the reliability of the boilers and turbines reduces.
3. Water consumption
Thermal plants use a lot of water. On average a 1000MW coal fired power station uses about 8.9 Gl (Giga litre) per annum. Although Eskom’s modern, coal fired, dry cooled power stations uses less water than the old conventional thermal power stations it still means that in a water scarce country, like South Africa, there is less water for other critical users like households and farm irrigation schemes.
4. Reduce CO2 emissions and water consumption
Let’s take an example in which each house hold and small industrial business replaces 1kW of conventional energy with some form of renewable energy. A thousand consumers translates to 1MW, ten thousand consumers will then convert 1GW of conventional electrical power to renewable power. This means that we could reduce the annual CO2 emissions by 7.1 million tonnes and save 8.9Gl of water, which is enough water to supply more than half a million households per year. Wind and solar energy produces no CO2 and uses no water.
5. Reduced availability and reliability of conventional electrical power
As we have already mentioned the age of Eskom’s coal fired power plants makes them more expensive to run and they do become less reliable. The South African economy grows constantly, which increases the demand for electricity. The global recession placed a damper on the economic growth in South Africa, which is a blessing in disguise for Eskom. We all remember the period of enforced load shedding (in early 2008) as the demand for electricity constantly exceeded the supply.
All power producers maintain a reserve generating capacity to cater for unexpected
surges in demand. An internationally accepted value for reserve capacity is 15% of
demand. Eskom’s reserved capacity has been reduced to 8% which is not sufficient
to maintain a reliable supply. During winter months the demand is high as many households
uses electricity for heating purposes while the available supply margin is low during
the summer months as Eskom performs the required maintenance on power plants. In
addition to this the efficiency of the thermal power plants are often lower due to
wet coal conditions and high ambient temperatures that adversely affects the cooling
of the steam in the condensers (especially on the dry cooled type power stations).
The refurbishment of old and mothballed power plants to increase the capacity is a small contribution compared to new powers stations.
Building large power plants takes years.
Eskom’s Demand Side Management programme (the aim of this programme is to change the mindset of the people so that they could stop wasting electrical energy and adopt ways to improve efficiently) also only has a limited affect on the power crisis.
Another aspect that needs to be considered is that many electricity users do not get their electricity directly from Eskom but through networks and equipment that belongs to municipalities. Due to mismanagement of funds, ineffective or incorrect maintenance activities the existing electrical infrastructures of many municipalities are ticking time bombs. The electrical equipment (cables, transformers and switchgear) in most municipalities is reaching the end of their useful life. Little or no money is budgeted for capital expenditure products to replace or refurbish this aging electrical equipment. This means that the reliability of electricity supplies (from municipalities) is dropping at alarming rates.
With the ever increasing demand for electricity and Eskom’s inability to increase the reserve capacity (at least over the short to medium term) and the increasing inability of utilities to supply reliable electricity to its users, requires that electricity users become less dependent on conventional energy supplied by the utilities.
Renewable energy in the form of solar and wind power provides an alternative so that electrical users can become less dependent on utility power. It is even possible that users can become completely independent by providing for their own needs as far as electrical energy is concerned and at the same time they do their bit to preserve the environment for future generations.
6. Improved technology and reduction in initial cost
Modern solar panels are more efficient, lighter and easier to install. One hour of full sun is estimated to produce 1kW of electrical energy per square meter of surface area.
Small scale, vertical axis, magnetically levitated wind turbines operate almost frictionless which ensures that they could start producing power at wind speeds as little as 2.7m/s (just under 10km/h). These turbines are readily available in sizes from 1 – 10kW.
Renewable energy, in the form of wind and solar power, often relies on batteries as a means to store the energy. The modern lithium iron phosphate batteries are powerful and safe and have a life expectancy of nearly 50 years. It is possible to replace lead acid batteries (with equivalent capacities) with batteries that weight seven times less, using only half the space). As an example: 20Ah cells weigh only half a kilogram with a peak output of 300A (for limited time duration). Sophisticated battery management systems monitor the performance and condition of each cell in a battery bank. As the demand for renewable energy products (wind turbines, solar panels, batteries and inverters increase the prices are reduced and at the same time more money becomes available to spend on R&D, which ensures a constant improvement in technology.
High efficient and cost effective PV solar panels
Vertical and horizontal mounted wind turbines
Super Lithium Iron batteries
Smart grid controllers, chargers and inverters
Why should South African households and small
industrial businesses consider alternative energy