The quest for Energy Efficiency in Ceiling Fans for a mass marketSeptember 14, EEDAL2017, Irvine

Durgasharan Krishnamurthy

Versa Drives Private Limited

Outline of the presentation Background and motivation Key results First technology transformation: Using a more

efficient motor and the issues faced therein. Second technology transformation: Using more

efficient better blades while remaining cost-effective Conclusions and Looking ahead

Background and Motivation Study led by Daljit Singh of Prayas in 2010 revealed some

interesting stats [1] Estimated 350 million fans were in use in India Almost all these use inefficient induction motors They consume 75W – 80W at top speed and 39W at medium speed

2013 Lawrence Berkeley National Laboratory Study Doubling the efficiency in all fans in the world will save 70 terra-

watt hours per year; Energy enough for 70 cities of 200,000 for a year [2]

High efficiency BLDC fans already available in developed countries are not suitable for mass markets

Key results Using Brushless DC motor (BLDC motor) saves more

than 50% energy but Harmonics is a problem; Power factor correction circuit is a must

LV BLDC motor is at least 50% less expensive than HV BLDC motor and is safer

Experimentally arrived at aluminium blades of uniform thickness are 12-16% more efficient compared to conventional blades while costing the same

Put together, the BLDC motor with better blades give an efficiency improvement of 150% while costing 60-70% more

Using Brushless DC motor to double the efficiency

Speed Power consumption (W)

Standard fan based on Single-phase Induction motor

Fan based on PM BLDC motor

Low 12 4Medium 39 14High 75 35

Table 1 A comparison of power consumption of ceiling fans based on different motor technologies at various speeds [8]

Brushless DC motor is a synchronous motor with permanent magnets and is very efficient as compared to a single-phase induction motor.

Harmonics problem and Power factor Correction as a solution

Load Active power (W)

Power factor

Total demand (VA)

Current(A)

CurrentTHD%

THD Amps for 500 Loads (A)

20W CFL with PFC 21.0 0.96 21.9 0.096 25.0 12.035W tube light with PFC 32.5 0.95 34.2 0.15 29.0 21.75Adapter without PFC 25.0 0.46 60.0 0.25 88.0 110.0PC SMPS without PFC 48.0 0.61 78.7 0.35 78.0 136.5

Table 2 Power, Power factor and THD values for some electronic loads [10]

Load Active power (W)

Power factor

Total demand (VA)

Current(A)

CurrentTHD%

THD Amps for 500 Loads (A)

Super X1 at 5th speed 34.0 0.96 35.4 0.158 21.7 17.1Super V1 at 5th speed 36.2 0.96 37.7 0.166 23.4 19.4

Table 3 Power, Power factor and THD values for BLDC fans with power factor correction [10]

Block Diagram of High Voltage BLDC motor with PFC

Fig 1 High voltage BLDC motor drive with power factor correction

Block Diagram of Low Voltage BLDC motor with PFC

Fig 2 Low voltage BLDC motor drive with power factor correction

Cost Analysis – Electronic Drive

Low voltage Drive High voltage DriveComponent Unit cost in USD1 Component Unit cost in USD1

SMPS Transformer 0.3 PFC Inductor 0.3Transition mode PFC Controller

0.3 Transition mode PFC Controller

0.3

SMPS MOSFET; 800V, 3A

0.5 PFC MOSFET; 650V, 3A

0.25

Output diode; 200V, 6A, ultrafast rectifier

0.22 PFC diode; 600V, 2A, ultrafast rectifier

0.12

Bulk capacitor; 2200uF, 35V, 105 ͦ C

0.36 Bulk capacitor; 47uF, 450V, 105 ͦ C

1.03

Low voltage MOSFET inverter

1.1 High voltage IGBT inverter

2.5

24V - 5V linear regulator

0.15 AC-DC auxiliary SMPS (transformer + SMPS IC)

0.57

Sum 2.93 Sum 5.07

Table 4 Comparison of the costs of power components of low voltage and high voltage drives

All costs are unit costs taken www.mouser.com or www.digikey.com and for at least 1000 numbers order quantity

Material Inputs Analysis – Motor

DescriptionLow voltage

motorHigh voltage

motor UnitsTotal weight of motor excluding drive 2.105 3.44 kgStator detailsNumber of slots 18 12Shaft length 120 148 mmStator weight 1.03 1.862 kgTotal copper weight 0.2064 0.31 kgWire gauge 22 SWG 34 SWGRotor detailsNumber of poles 16 14Back iron weight 0.152 0.337 kgMagnet dimensions 25 x 22 x 7 28 x 26.55 x 8 mmTotal magnet weight 0.2879 0.4 kg

Table 5 Comparison of the material inputs of low voltage and high voltage motors

Efficiency and Safety

Fan type Power (W)

Speed (RPM)

PF Air Delivered (CMM)

Single moving vane anemometer (1300170); 8 sample moving average

method

Service Value

(CMM/W)

High voltage

24.3 364 0.93 197 8.1

Low voltage 25.2 344 0.98 198 7.86

Leakage current measured as per IS 302-1:2008, clause 13High voltage fan Low voltage fan6.8 milliamps 0.96 milliamps

Table 6 Comparison of the power, air delivery, and service value of high voltage and low voltage fans

Table 7 Leakage currents of high voltage fan and low voltage fan

Brushless DC motor based fan - Takeaways Low voltage BLDC motor with built in power factor

correction is the first and most impactful step in increasing the efficiency of the fan

Power consumption comes down by more than half as compared to an induction motor fan

Electronics and magnets increase the cost by 60%-70%

Increasing efficiency further using better blades Danny Parker and associates invented blades of high

efficiency in 2000 using aerodynamics’ principles [16] and these have been commercialized as Gossamer wind fans [7]

The blade cross-section varies in thickness along the length of the blade [16]

The above characteristic of the blades require use of industrial plastics and expensive tooling

Increasing efficiency further using better blades in a cost-effective way We used an aluminium sheet of uniform thickness (1

mm) allowing the use of a simple forming tool Flat trapezoidal blank which is 140mm wide at the

hub and 90mm wide at the tip was formed into a blade of continuously twisting angular shape

Experimental result: Tip twist angle of 9 -12 degrees and hub twist angle of 18-22 degrees

Blades formed to twist angles according to Betz condition ([12]) did not yield the desired results

Efficiency results with new blades (R1)

Fan type Power (W)

Speed

(RPM)

Air Delivery (CMM) Service Value (CMM/W)

Induction motor fan

75 380 225 3

BLDC fan with regular blades

33.5 388 221 6.6

BLDC fan with R1 blades

33.5 260 256 7.633

Comparison of the power, air delivery, and service value of various fans

Fan type Power (W)

Speed (RPM)

Air Delivery (CMM) Service Value (CMM/W)

BLDC fan with regular blades

25.2 344 198 7.86

BLDC fans with R1 blades

24.0 229 212 8.83

Table 9 Comparison of the power, air delivery, and service value at lower speeds

Aluminium blade forming tool images

Fig. 3a Forming tool front view

Fig. 4a Bottom section of forming tool Fig. 4b Bottom section of forming tool

Fig. 3b Blade blank before forming

Fan (with new blades) image and new blade (R1) cross sections’ image

Some observations about R1 blades 12% - 16% increase in efficiency with R1 blades R1 blade fan top speed is >100 rpm less => Lesser

acoustic noise (preliminary test: 7-9 dBA less) Tool cost of about 300,000 INR (4285 USD) which

is similar to that for regular aluminium blades; In contrast plastic blade tooling can cost 2,500,000 INR (38,500 USD)

Blade cost of 85 INR each (1.29 USD) which is the same as that of regular aluminium blades

Improved efficiency at the same cost

Conclusions and Looking ahead There is enormous scope for energy saving in ceiling fans BLDC motor ceiling fans with aero-dynamically better blades

are 150% more efficient than induction motor fans, while costing 60% - 70% more

Newer MOSFETs with half the on-resistance can further improve the efficiency by about 2%, while costing the same

AC-DC SMPS efficiency can be improved to 90% as compared to 87% now using different topology [19]

Need for a) blades of optimal aerofoil made of cost-effective materials, b) more cost-effective manufacturing of the same. These blades can increase efficiency by > 40%

WIFI connectivity can give better energy management

References[1] Daljit Singh, Avinash Barve, Girish Sant. Ceiling fan: The Overlooked Appliance. Prayas Energy Group, Pune, March 2010. www.prayaspune.org

[2] Nakul Sathaye, Amol Phadke, Nihar Shah, Virginie Letschert, Lawrence Berkeley National Laboratory. Potential Global benefits of Improved Ceiling fan energy efficiency, SEAD, April, 2013. www.superefficient.org

[3] Midway Eco fans. Emerson Electric Company, ceilingfans.emerson.com/shop/en/fan/midway-eco-fan-p-cf955

[4] Haiku fans. Big Ass solutions, www.bigassfans.com

[5] www.khaitan.com , www.crompton.co.in/economy/, www.havells.com/en/consumer/fans/ceiling-fans/regular.html, www.usha.com/fans/ceiling-fans/decorative/striker-platinum-lavender-chrome, https://shop.bajajelectricals.com/Bajaj-Bahar-Ceiling-Fan-pc-403-47.aspx

[6] www.khaitan.com/inner_pro.php?id=65, www.havells.com/en/consumer/fans/ceiling-fans/energy-saving/es-50-sweep-white.html

[7] Gossamer Industrial fans. www.gossamerwind.com

[8] Superfan brochure. www.superfan.in/downloads.html

References (contd.)[9] N. Mohan, T. M. Undeland, W. P. Robbins. Power electronics, converters, applications, and design, John Wiley & Sons, 3rd edition.

[10] K. Durgasharan, Total Harmonic Distortion in demand current, 2014, Internal report, Versa Drives Private Limited.

[11] Bureau of Indian Standards. IS 302-1:2008, Safety of household and similar electrical appliances, part 1, General requirements (sixth revision). August 2008.

[12] Charles N. Adkins, Robert H. Liebeck. Design of Optimum Propellers. JOURNAL OF PROPULSION AND POWER, Vol. 10, No. 5, Sept.-Oct. 1994.

[13] Larrabee, E. Practical Design of Minimum Induced Loss Propellers.Society of Automotive Engineers, Business Aircraft Meeting and Exposition, Wichita, KS, April 1979.

[14] Søren Gundtoft. Wind turbines. University College of Aarhus, June 2009

[15] From Helios to Our house. http://www.memagazine.org/contents/current/features/helios/helios.html

[16] Parker, D., Hua, G., and Hibbs, B. (2000). High efficiency ceiling fan. United States Patent Number 6039541.

References (contd.)[17] Peter J. Schubel and Richard J. Crossley. Wind Turbine Blade Design, Section 5.5. Energies 2012

[18] N. R. Mirudhula, R1 blade design, 2016, Internal report, Versa Drives Private Limited.

[19] Bernard Keogh. Power Factor Correction Using the Buck Topology—Efficiency Benefitsand Practical Design Considerations. 2010 Texas Instruments Power Supply Design SeminarSEM1900, Topic 4, TI Literature Number: SLUP264.

[20] https://en.wikipedia.org/wiki/Turbomachinery

[21] George Wilkenfeld and Lloyd Harrington. Too smart for our own good: Why intelligent appliances seem as far away as ever. Proceedings of the 8th International Conference on Energy Efficiency in Domestic Appliances and Lighting, 2015.

[22] Durgasharan Krishnamurthy. The quest for Energy Efficiency in Ceiling Fabs for a mass market. Proceedings of the 9th International Conference on Energy Efficiency in Domestic Appliances and Lighting, 2017.

Thank you