By Eamonn Ryan from a SAIRAC Cape Town presentation
At the SAIRAC Cape Town Tech Talk, Marthinus Greeff from WEG South Africa discusses the vital topic of motor efficiency, emphasising its growing importance globally and its impact on South Africa’s energy landscape. The session highlights the need for more energy-efficient motors, especially with the upcoming regulatory changes in South Africa. This is Part 2 of a seven-part series.
The SAIRAC Cape Town Centre January TechTalk. SAIRAC Cape Town Centre.
South Africa is leading the charge in Africa by adopting IE3 motors as the minimum efficiency standard, starting in May 2024. This regulatory shift positions South Africa as a key player in Africa’s push for energy efficiency, with government support guiding industries through the transition.
Understanding motor efficiency classes
Greeff explains motor efficiency classes, which are standardised globally:
- IE1: Standard efficiency
- IE2: High efficiency
- IE3: Premium efficiency
- IE4: Super-premium efficiency
- IE5: Ultra-premium efficiency (for motors with Variable Speed Drives)
These classifications help companies choose the right motor for their needs, with IE3 being the minimum for most applications. Larger motors, often over 1 000 kW, typically require medium voltage for efficiency and safety.
Calculating costs and savings of efficient motors
Greeff discusses the financial implications of selecting more efficient motors, emphasising the importance of understanding energy consumption. For example, a motor with 91.4% efficiency loses 0.86 kW to heat and inefficiency, impacting its electrical input. By factoring in load, efficiency, and operating hours, businesses can calculate long-term savings when switching to high-efficiency motors.
The real-world cost comparison
Greeff compares the running costs of two motors: one with 91.4% efficiency and another with IE3 (premium efficiency). Using Eskom’s tariff rate of 232 cents per kW/h, running the less efficient motor for a year costs approximately R60 000. In contrast, the IE3 motor’s operating cost drops to around R14 500—highlighting the economic benefits of investing in higher-efficiency motors.
Upfront investment vs long-term savings
Although high-efficiency motors have a higher initial cost, their lower running costs over time make them a better investment. Greeff points out that the savings on electricity can quickly offset the higher upfront costs. For example, the running cost of a low-efficiency motor could exceed the motor’s purchase price within just a month, making the case for prioritizing efficiency clear.
The impact of rising electricity costs
Greeff assumes a 10% annual increase in electricity prices over the next decade. This highlights how energy-efficient motors will become even more cost-effective as electricity rates rise. To help attendees assess potential savings, WEG offers an energy efficiency tool on the website, allowing users to calculate savings based on their motor specifications.
Comparing IE1 and IE3 motors
The difference in efficiency between an IE1 motor and an IE3 motor might be only 3%, but the cost savings are substantial. Greeff demonstrates that the additional cost of an IE3 motor can be recouped within seven months if running 24 hours a day, or 14 months with 12-hour daily operation. This underscores the importance of investing in high-efficiency motors for long-term financial and environmental benefits.
Longevity and maintenance considerations
Motor longevity is another factor to consider. Greeff explains that a well-maintained motor can last up to 30 years, but improper maintenance can shorten its lifespan to around 10 years. He also discusses the efficiency losses from motor rewinds, which can result in a 2-3% reduction in performance each time. Repeated rewinds can compound these losses, leading to higher energy consumption.
Holistic system efficiency
Greeff advocates for looking beyond just motor replacement when assessing energy efficiency. Often, the overall system—including components like pumps and fans—may need optimisation to achieve the best energy savings. Replacing an entire system, rather than just the motor, could be more cost-effective and energy-efficient in the long run.
Local regulations and compliance
Greeff highlights the new South African regulation mandating that all low-voltage motors meet IE3 efficiency standards starting May 31, 2024. This law will affect approximately 99% of low-voltage motors in South Africa, requiring businesses to transition to higher-efficiency motors to comply. Companies should begin planning for this change now to avoid penalties and capitalise on energy savings.
Key takeaways
- Economically viable IE3 motors: The additional cost of an IE3 motor is quickly recouped through energy savings.
- Maintenance extends motor life: Proper maintenance and limited rewinding can significantly extend a motor’s lifespan.
- Consider the whole system: Evaluating the entire system—including pumps and fans—can provide better energy efficiency than just replacing the motor.
- Regulation compliance: South Africa’s new efficiency regulations, effective May 31, 2024, require all low-voltage motors to meet IE3 standards. Preparing now ensures compliance and allows companies to take full advantage of energy savings.
Marthinus concludes by stressing the importance of transitioning to energy-efficient motors, both for financial benefits and to comply with upcoming regulations in South Africa.
