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motor

  1. Motor supervision and control
  2. Power factor correction
  3. Compressors
  4. Boiler plant operation
  5. Lighting
  6. HVAC - Fans and Pumps
  7. Variable speed drives

 

Motor supervision and control


Old electric motors waste energy. Examining all motors and replacing old units with energy efficient motors makes sense- especially when there is a money-saving subsidy scheme available from Eskom for the purpose. Combining the capital expenditure savings with operational savings makes long-term sense. The savings to the economy are also significant as the estimated100 000 industrial motors presently consume up to 10.0 GW of electricity in South Africa and account for 60% of the total industrial energy usage and about 57% of peak demand generation.

By making use of the Eskom subsidy scheme, purchasers of motors ranging from 1.1kW through to 90 kW qualify for subsidies. The 1.1kW units qualify for a subsidy of R400, while the discount on a 90kW unit subsidy is R 3 500.

Savings are significant. A 22kW energy efficient motor includes a R 1 400 once-off subsidy on the catalogue price and produces energy savings of 9,056kWh/ a year, or R 5 071 a year. Additional benefits include compatibility with variable speed drives, presenting operators with an opportunity to improve drive systems and optimise processes.

Backing a move to energy efficient motors with increased supervision and control of motors will maximise benefits. Switching off drives that are running, but are not being used, helps reduce energy and running costs.


Power factor correction

Improving the overall power factor of plant can hold several benefits. These include increased plant capacity and the reduction of electrical maximum demand charge. In addition, power losses can be reduced in feeders, transformers and distribution equipment.

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Compressors

Compressed air leakages can be problem areas. An audit of equipment and development of a comprehensive maintenance and leakage prevention plan can significantly reduce leakages and lead to significant energy and cost savings.

Training and education can reduce the use of compressed air for function such as regulating ambient temperatures and general cleaning.

 

Boiler plant operation

Regular examination and maintenance of boiler systems are essential to effective energy savings. Consideration should be given to:

  • Checking the gas and air tightness of boilers regularly
  • Exercising care when operating above maximum continuous rating (MCR) as this could reduce the life span of the boiler
  • Calibrating feed water and steam flow meters to determine boiler leaks.

Lighting

  • Install efficient lighting systems.
  • The use of electronic ballasts is not common in commercial and industrial lighting systems, yet they can save up to 60% of the electricity required.
  • Many lights are generally left on unnecessarily in buildings during the day and night. Lighting controls in buildings can ensure that energy is conserved during periods of low occupancy.
  • When buildings with centralised air conditioning plants are fitted with energy efficient lighting, these systems generate less building heat load, so energy is saved on cooling equipment.
  • Optimising the design and location of light fittings can also save energy. It is wise to make use of the services of lighting specialists when making choices on lighting system design.

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HVAC - Fans and Pumps

  • Pumping is the biggest single application of motive power. Fans also use significant amounts of electrical energy. Systems with fans and pumps offer many opportunities to save energy on pump and fan drives. Basically the fluid or gas has to be delivered at the end of a system of pipes or ducts. If the pipes or ducts are poorly placed or designed, then the pump or fan motors use more energy than would be the case to deliver the same volumes with more correctly designed fluid and gas flow systems.
  • Leaky pipes, valves or ducts also require more motive power to deliver the same useful volume where and when it is needed. Prevention of leaks is important. Filters and fan belts that are not replaced at the appropriate times or maintained properly could also cause inefficient energy consumption.
  • Pumps or fans may not be running as efficiently as they could because the pump or fan curve has not been properly matched to the load curve. In this case it would possibly help to trim impellers.
  • In some cases where valves and damping vanes are used to regulate fluid or gas flow, there may be too much energy dissipated by the valves or dampers, simply because the fan or pump is oversized. Right-sizing of pumps and fans to match the load is important in implementing energy efficiency.
  • Technical knowledge, operations and maintenance skills on fans and pumps in industry is essential. Avoid fan belt slippage - replace if worn

 

Variable speed drives

  • Install variable speed drives on cubed law loads(?) and save up to 60(?)% on energy
  • Replace efficient motors rather than rewinding them
  • Upgrade to higher efficiency motors

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