Variable Frequency Drives: An Important Energy Saver

By IBT Inc

February 04, 2010

Electrical

Is the energy bill at your facility too high?

Are you actively searching for cost savings?

Image courtesy of SiemensDo you have applications were the motor runs at full speed and the volume/flow is controlled by a valve or damper?

If you answered yes to any of the questions above, there is a solution. Electric driven loads represent almost two thirds of the industrial electric power demand.

The bad news: As energy costs continue to increase, this cost factor always has a negative impact on production costs.

Image courtesy of YaskawaThe good news: For almost every company, this represents enormous cost-saving potential that is presently not being tapped into. Especially in energy-intensive sectors, up to 70% of the energy used can be saved.

Flow machines such as pumps, fans, and compressors typically run at 100% of rated speed, delivering a maximum rate, which is rarely required. The application of a Variable Frequency Drive (VFD) can save a considerable amount of energy, often paying for the investment in a matter of months.

Today, most facility managers and owners are looking for answers to the question: Where is the highest cost-saving potential? And for most companies the single biggest (non-payroll) expense is electricity.

Changing over to energy-efficient drive technology gives you an immediate payback, especially:

  • in industry sectors that use a lot of energy
  • for mechanically controlled machines such as pumps, fans or compressors
  • for drives that operate for long periods of time
  • drives that frequently run in partial load operation
  • applications where the drive must be repeatedly braked

It is especially important to consider lifecycle costs in selecting the optimum drive technology. Operating costs are especially high when compared to the original purchase price. For example, 97% of the lifecycle costs of a motor occur in operation. And of this 97%, energy costs are frequently by far the highest cost factor. Here an enormous cost-saving potential is waiting to be tapped into.

VFD Cost Savings Example

The cost to run a pump at 100% (full speed) all day costs $3879.20. Assuming a pump does not need to run at full speed the entire day, we will use an example of:100% Speed for 25% of the day
80% Speed for 50% of the day
60% Speed for the remaining 25% of the day
Cost of running with an AC drive controlling the motor:20 hp x (1) 3 x 0.746 kW/hp x 650 hours x $0.10/kWhr = $969.80 per year20 hp x (0.8) 3 x 0.746 kW/hp x 1300 hours x $0.10/kWhr = $993.08 per year

20 hp x (0.6) 3 x 0.746 kW/hp x 650 hours x $0.10/kWhr = $209.48 per year

Total = $2172.36 per yearAnnual savings: $3879.20 – $2172.36 = $1706.84 per year

IBT represents two premier manufactures of Variable Frequency Drives: Siemens and Yaskawa. Call your local sales representative for additional information or to schedule an Energy Savings Audit at your facility.

American Recovery and Reinvestment Act of 2009

The American Recovery and Reinvestment Act of 2009 (ARRA) provides funding opportunities for states and industry to improve efficiency and reduce emissions.