Alternative energy sources
By TL Martin
In South Africa we have been spoiled with reliable and cheap electricity for many years. Eskom, which supplies 95% of South Africa's electricity,has praised them selves in the past by saying that they supply reliable electricity at some of the lowest rates in the world. At that stage Eskom still had ample reserve capacity.
This has unfortunately changed over the last couple of years due to various reasons, without elaborating too much on the reasons for the power crisis at the beginning of 2008, the bottom line being that the electricity supply from this parastatal could not meet the demand. The consumers were bombarded with unscheduled load shedding and frequent brownouts. Terminology that was unknown to South Africans until very recently.
The demand for electricity has also unexpectedly increased over the last few years due to the strong growth in the economy. Strategic vagueness and planning confusion delayed investment in new power generating capacity.
So what is the solution? A number of solutions were proposed and followed, mainly focusing on the supply- and demand side of electricity.
On the supply side there is Eskom's R300-billion-plus investment and capacity expansion program: developing new peaking and base load capacity as well as refurbishment of existing operating capacity. These programs have long lead times and will only contribute to the supply capacity in the longer term. Eskom also called for expression of interest from the private sector to supply green power, to generate electricity from renewable resources.
In the interim Eskom has invited private sector participants to become involve in the co-generation of electricity. Eskom will allow these independent power producers (IPP's) to generate 30% of the extra power capacity required to sustain the growth in the economy. Eskom has rolled out three IPP programs: the Pilot National Cogeneration Program, the Medium Term Power Purchase Program and the Multi-site Base load Independent Program. In addition the Department of Mineral and Energy is running an IPP project sourcing electricity from IPP's across our borders for example the Mmamabula energy project.
Again, a substantial electricity supply from IPP's will only be available in a few years time. The short-term solution lies in limiting the demand for electricity rather than increasing the supply capacity. For this reason a demand side management (DSM) program was launched to increase energy efficiency. The influence of the DSM program has been fairly restricted.
One of the main reasons for the electricity crisis is the low coal stock reserve. As a temporary solution Eskom is resolving coal supply issues.
For most electricity consumers these programs implemented by Eskom does not improve the current situation. The margin of spare capacity on the national electricity grid will remain small and this means that the Eskom's generation system will remain under pressure. The generating equipment is frequently overloaded, putting unwanted strain on the electrical infrastructure. There is less time for preventative maintenance; all these factors will have an adverse effect on the lifespan of the equipment. For the consumer there are unfortunately no encouraging prospects and from a consumer point the electricity supply remains vulnerable.
The only way for consumers to protect themselves against the vulnerability of the electricity supply is to provide their own backup energy. Various businesses have lost a lot in revenue income due to power outages, for example companies that supplies or stock frozen and perishable goods, bakeries, supermarkets, filling stations, etc
When choosing a backup power system there are several options ranging from power generators (driven by petrol or diesel engines), uninterruptible power supplies (UPS), inverters to renewable power sources: wind and/or solar power. Each of these alternatives has advantages and disadvantages. Ultimately the application will determine the type of system best suited.
Before considering the use of backup power systems it is important to note that backup systems and batteries are expensive and that batteries have a limited lifespan. Every appliance connected to the backup supply that is not absolutely essential will significantly increase the cost of the backup system.
Many businesses rely heavily on electric power to produce products or provide services. These businesses have no options but to install a backup power system. Apart from the fact that the capital cost is high the running costs of backup supply systems are also high. These additional costs have a direct impact on profit margins. It's therefore recommended that you cautiously consider which machines and processes should run on the backup system during a power failure
For example: the refrigerator in the company's kitchen that is without power for a couple of hours and the air-conditioning system in the office that remains off during the power outage will have no negative effect while the temperature for bread ovens could be critical. A water feature not working will have much less impact than a computer server, security fence or alarm system not working.
In most cases a battery bank together with a combination of UPS/charger/inverter is proposed. With the normal mains power available the device charges the batteries. When the supply fails the device acts as an inverter, inverting the stored battery power from DC to normal AC power. These devices are available in three phase or single phase versions. In cases of extended power failures the primary backup system may be further backed up with a secondary system, for example a generator.
Note that your business will not necessary require a primary as well as a secondary backup power system. Again, the decision whether a business should go for a generator or a battery powered inverter/UPS backup system depends on the application. A battery backup system is more appropriate for short duration power failures (typically 2 to 3 hours, load shedding).
The generator backup is more ideal for extended power cuts or where larger loads are concerned. Some of the reasons are: a battery backup (inverter) system does not need any human intervention when the normal supply fails and the device will automatically supply the load as oppose to a generator a human need to start the generator and operate a changeover switch (unless the generator is equipped with an electric starting function and an automatic mains failure panel that will automatically transfer the load from mains supply to generator supply, which is fairly costly). If the generator is not equipped with a sound attenuating canopy the noise from the engine could be disturbing as well as the exhaust fumes.
To accurately size a system the installer would need to know how much backup time is required, and the average and peak power consumption requirements during this time. The installer need to know the type of load, as this will determine what backup system is required
The typical middle-size business could need uninterrupted power for the following:
Lighting: a few lights (preferably low energy compact fluorescents or LED lights) positioned in working areas like offices, board rooms etc. From a safety aspect businesses should provide emergency lighting in potentially dark areas such as staircases or where employees are working at night.
Security: Electric fences, Intercom, gate motors, alarm systems and CCTV cameras.
Communication: Power for PC's, servers and telephones (switchboard and PABX systems).
Uninterrupted power is normally not required for refrigerators and freezers or for cooking devices, kettles and other appliances. These could be done with LP Gas or electrical power from a generator.
In addition to the backup systems discussed above there are alternative energy sources (green power) with the added advantage that you will be using renewable and sustainable energy like electricity generated from the sun, wind or water energy. The use of energy efficient appliances and lighting as well as non-electric alternatives wherever possible can make alternative electricity an environmental friendly alternative to gasoline generators or utility power.
The size and therefore the cost of an alternative electric system depends on the amount of power that is required (watts), the amount of time it is used (hours) and the amount of energy available from the sun (sun hours per day) or wind in a particular area. A system will be designed and priced according to the customers' exact needs. In order to do this, detailed information on the equipment to be used is needed.
Energy efficiency plays an important role in keeping the cost of an alternative electricity system down. Compact fluorescent energy saver lamps use only 20% of the energy a normal incandescent bulb consumes. The latest technology uses LED lights that uses even less electricity than compact fluorescent lamps.