Energy Efficiency Made Simple Vol IV 2015

A need for energy, both real and perceived, has been the driver of electrical innovation for well over a century. Whereas much can be done to optimise what we already have, the opportunities (especially in Africa) are driving a new wave of innovation. To appreciate this, it is important to review our past.

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Power electrical systems – progress over time H du Preez, Consultant

Power savings in transformers and motors is an area where there have been a number of improvements in the past few decades – with room for more. Various figures are quotedwhen the equipment that uses the most electricity is considered. It is said that between 60 and 70% of the total electricity generated is used by electric motors in some form or other. A s most of the power used in the country is generated in par- ticular areas, a distribution system is required – which means transformers and transmission lines. South Africa’s power is predominantly generated by coal – causing CO 2 emissions that pollute the atmosphere. Saving electricity actually reduces pollution. Alternative environmentally-friendly generation systems such as solar, wind, wave and hydro also come with their particular problems and limitations. At the turn of the 20 th century, 1903 and onwards, electricity was in its infancy with direct current (dc) systems and research into alter- nating current (ac) just beginning. Dc motors and dc generators were

Figure 2: Early dc machine.

the norm. Convenience rather than efficiency was the consideration – light at the turning on of a switch and power away from the water wheel or steam engine. The incandescent lamp comes from this era. When ac power started to make its mark, it was realised that pow- er could be saved; for example, an ac arc lamp requiring 8 Amps (A), 30 Volts (V) and 240Watts (W) but with a 110 V supply, a resistor would be connected in series; the power in the resistor would be 640 W wasted power until a choke coil was developed using a coil wound over an iron core, dropping the voltage with a much smaller power loss. This system obviously only works when an ac system is employed. As we progressed through the 20 th century, technology and ma- terials advanced to improve efficiency and reduce wasteful systems. Materials: Materials have been improved and with better use and design, savings are realised. Electrical steels: The attraction of flux magnification and its dividend of force control was central to early machine design, but as the electrical industry grew, the spotlight turned to energy efficiency.

Figure 1: Ring Dynamo.

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ENERGY EFFICIENCY MADE SIMPLE 2015