Optimization of industrial fans in Kenya

Kawitrack industrial fans

The expanding middle class in Kenya has put increased pressure on the country’s electricity demand. In response, from 2015, the Kenya Power Company commenced the Last Mile Connectivity project aimed at connecting a whopping 300,000 households to the national grid, in its first phase. Today (2018), Kenya Power is inking deals with local and foreign companies to have an extra 600,000 households in the low-income bracket connected within 18 months.

 

Switch over to the commercial side and the Ministry of Industry, Trade and Cooperatives has reported a 53% spike in the number of registered companies. Such growth in industry will affect the rate of purchasing equipment for those creating businesses to cater for the population. Industrial fans are some of the major equipment in commercial settings, whether for Heating, Ventilation & Air Conditioning (HVAC) systems, exhaust gas/moisture removal etc.

 

Fans can be categorized as either domestic (below 125 Watts) or industrial (above 125 Watts). Industrial fans fall into the following categories:

 

  • Industrial axial fans
  • Centrifugal fans
  • Mixed flow
  • Industrial blower fans

Because they are motor-driven equipment, they will take up a significant share of a plant’s or building’s energy cost. It is therefore important to identify energy management opportunities in order to drive your energy bills down.

 

Regulations

Normally there are local and international regulations that will offer guidelines on the minimum efficiencies of industrial fans. In Kenya, we don’t have local codes on fan efficiency yet, but we can still use the international regulations set up by the EU, the ISO12759:2010 .

 

Optimization opportunities

Optimization of industrial fan systems usually starts with baselining. This is the analysis of each system’s current fan power consumption patterns. The major stages of this process involve:

 

  1. Installing power and energy loggers at different loads served by the fans
  2. Recording the power and energy consumption patterns over a 7-day period to allow trends to be identified
  3. Compare the data with power bills (if available) to see how it contributes to the overall bill from your utility company (Kenya Power in most cases)

 

Baselining will give us a leg up in getting to sample some of the energy efficiency options depending on the type of fan and its functionality.

 

Here are the most common optimization opportunities you could start exploring immediately:

 

  1. Slow down or stop
  2. Proper design and sizing
  3. Install VFD
  4. Upgrade to energy efficient fans

 

Let’s go through each one.

Slow down or stop

Constant load processes like removal of particulate material have a setpoint that if not met will not achieve their purpose therefore potentially making the operating environment hazardous. For variable load processes like cooling or heating however, the fan can be slowed down or stopped if the demand is low.

Assuming there is no change in the ducting system of a HVAC system for example, a 10% decrease in fan speed can result in a reduction of about 25% of the motor power (Figure 1b)

Kawitrack power versus fan speed

Figure 1a. Power and increasing fan speed

Kawitrack power versus fan speed

Figure 1b. Fan and decreasing fan speed                                                      Graphs showing the effect of Fan speed (%) on Motor Power (%)                  Source – DELTA NEU Limited 2014

Example

 

Parameters:

Energy cost = KES 21.03/kWh

Annual operating hours = 2000hrs

Calculations:
A 22kW withering fan stops for 10% of production time as tea is placed on the beds and operates at full capacity at 90% of production time Operating FULL LOAD at 100% of production time:

 

With the STOP for 10% of production time:

 

ANNUAL SAVINGS:

 

Proper fan design and sizing

How did you arrive at the motor and fan design that you’re currently using? Has your industrial fan been properly sized to fit your current needs? It is common practice for many companies to procure extra-large fan units. What is not always apparent is the cost of operating an underloaded fan. Fan motor efficiency and power factor (PF) are directly affected by the load. Fan motors operating at low loading (<50%) will have efficiencies lower than the nameplate information.

Figure 3. Induction motor efficiency
Source. All About Circuits

Whereas data on the full-load power can be found from the nameplate, measured voltage and current values during operation can be found by mounting Power and Energy Loggers (PEL).

 

NOTE

Working on a high voltage supply is highly risky and should only be done by a qualified personnel. Appropriate safety gear must also be used.

 

Under-loading results in poor motor efficiency, low motor power factor and spikes in your demand graph. Eventually, Kenya power will often slap you with Power Factor and Demand Charge penalties for poor utilization.

 

The US Department of Energy’s Motor Challenge Program is a good place to start to learn how to use your induction motors more efficiently. Here, we have prepared an Excel template for you that can be used to calculate fan loading and fan efficiency

Installation of VFD

Motors account for 65% of all the industrial energy use. The need for correct optimization is therefore necessary to realize cost-effectiveness. Installing a Variable Frequency Drive (VFD) helps regulate the motor’s supply current as the load changes. In short, VFDs can:

 

  1. Start and Stop motors
  2. Customize for constant/ variable speed
  3. Have speed limits
  4. Speed ramping
  5. Enable forward/reverse operation
  6. Save energy

Replacing older fans with energy efficient fans

Today motor manufacturers like Siemens have advanced their motor performance classes from the 3 energy levels in 2008, now to 4 levels (from 2014). These include:

 

  • IE1 (Standard Efficiency Motor)
  • IE2 (High Efficiency Motor)
  • IE3 (Premium Efficiency Motor)
  • IE4 (Super Premium Efficiency Motor)

Upgrading your motors might have a substantial set up cost, but the returns outweigh the costs in the long run. Doing a careful financial analysis on your upgrade options is an effective way to analyze prices from manufacturers, annual savings, simple payback (SP) and ensure compliance with the energy regulator.

Conclusion

Ultimately, you will need an energy audit in order to come up with a systematic way of improving the baseline performance of your facility. For better performance, you will also have to come up with a way to continuously track your progress. It therefore goes without saying that hiring energy professionals is in the best interest of your company.

Further reading

AMCA – Realizing Energy Efficiency Opportunities in Industrial Fan and Pump Systems

DELTA NEU LIMITED -How to save energy with industrial fans

Reliable Plant – How to optimize your industrial fan systems

 

 

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