The quest for Energy
Efficiency in Ceiling Fans for
a mass market
September 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
Table 1 A comparison of power consumption of ceiling fans based on different
motor technologies at various speeds [8]
Speed Power consumption (W)
Standard fan based on Fan based on PM BLDC
Single-phase Induction motor
motor
Low 12 4
Medium 39 14
High 75 35
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
Table 2 Power, Power factor and THD values for some electronic loads [10]
Load Active Power Total Current Current THD Amps
power factor demand (A) THD for 500
(W) (VA) % Loads (A)
20W CFL with PFC 21.0 0.96 21.9 0.096 25.0 12.0
35W tube light with PFC 32.5 0.95 34.2 0.15 29.0 21.75
Adapter without PFC 25.0 0.46 60.0 0.25 88.0 110.0
PC SMPS without PFC 48.0 0.61 78.7 0.35 78.0 136.5
Table 3 Power, Power factor and THD values for BLDC fans with power factor
correction [10]
Load Active Power Total Current Current THD Amps
power factor demand (A) THD for 500
(W) (VA) % Loads (A)
Super X1 at 5th speed 34.0 0.96 35.4 0.158 21.7 17.1
Super V1 at 5th speed 36.2 0.96 37.7 0.166 23.4 19.4
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
Table 4 Comparison of the costs of power components of low voltage and high voltage
drives
Low voltage Drive High voltage Drive
Component Unit cost in USD1 Component Unit cost in USD1
SMPS Transformer 0.3 PFC Inductor 0.3
Transition mode PFC 0.3 Transition mode PFC 0.3
Controller Controller
SMPS MOSFET; 0.5 PFC MOSFET; 650V, 0.25
800V, 3A 3A
Output diode; 200V, 0.22 PFC diode; 600V, 2A, 0.12
6A, ultrafast rectifier ultrafast rectifier
Bulk capacitor; 0.36 Bulk capacitor; 47uF, 1.03
2200uF, 35V, 105 ͦ C 450V, 105 ͦ C
Low voltage MOSFET 1.1 High voltage IGBT 2.5
inverter inverter
24V - 5V linear 0.15 AC-DC auxiliary 0.57
regulator SMPS (transformer +
SMPS IC)
Sum 2.93 Sum 5.07
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
Table 5 Comparison of the material inputs of low voltage and high voltage motors
Low voltage High voltage
Description motor motor Units
Total weight of motor excluding
drive 2.105 3.44 kg
Stator details
Number of slots 18 12
Shaft length 120 148 mm
Stator weight 1.03 1.862 kg
Total copper weight 0.2064 0.31 kg
Wire gauge 22 SWG 34 SWG
Rotor details
Number of poles 16 14
Back iron weight 0.152 0.337 kg
Magnet dimensions 25 x 22 x 7 28 x 26.55 x 8 mm
Total magnet weight 0.2879 0.4 kg
Efficiency and Safety
Table 6 Comparison of the power, air delivery, and service value of high voltage and
low voltage fans
Fan type Power Speed PF Air Delivered (CMM) Service
(W) (RPM) Single moving vane Value
anemometer (1300170); 8 (CMM/W)
sample moving average
method
High 24.3 364 0.93 8.1
197
voltage
Low voltage 25.2 344 0.98 198 7.86
Table 7 Leakage currents of high voltage fan and low voltage fan
Leakage current measured as per IS 302-1:2008, clause 13
High voltage fan Low voltage fan
6.8 milliamps 0.96 milliamps
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)
Comparison of the power, air delivery, and service value of various fans
Fan type Power Speed Air Delivery (CMM) Service Value
(W) (RPM) (CMM/W)
Induction motor 75 380 225 3
fan
BLDC fan with 33.5 388 221 6.6
regular blades
BLDC fan with R1 33.5 260 256 7.633
blades
Table 9 Comparison of the power, air delivery, and service value at lower speeds
Fan type Power Speed Air Delivery (CMM) Service Value
(W) (RPM) (CMM/W)
BLDC fan with 25.2 344 198 7.86
regular blades
BLDC fans with 24.0 229 212 8.83
R1 blades
Aluminium blade forming tool images
Fig. 3a Forming tool front view Fig. 3b Blade blank before forming
Fig. 4a Bottom section of forming tool Fig. 4b Bottom section of forming tool
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 Benefits
and Practical Design Considerations. 2010 Texas Instruments Power Supply Design Seminar
SEM1900, 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
