Energy Efficient Elevators: A Study of Regenerative Drive Group Members Shaheen Mistry Htet Eint Phoo Shruti Srinivas Vaishali Parmar
Introduction Context • BCA has targeted 80% of all buildings in SG to be GM certified by 2030. installation of regenerative lifts is a prerequisite for Green Mark Certification. •
Regen is a green technology. It produces clean & safe energy that does not damage the network
Significance Buildings account for 38% of total electricity consumption in SG and out of this 3% to 10% is consumed by elevators. • Taking into account demographic trends as well as a growing need for convenience, it is expected that the number of lifts and escalators will be rising worldwide. • Further urbanisation in developing countries and a growing awareness of accessibility issues due to an aging population s will foster the need for more of this equipment. • Understanding energy usage and costs is becoming increasingly important to clients of the elevator industry. Thus it is necessary to be able to predict, with reasonable accuracy, the energy usage of a new elevator installation and of an existing installation post modernization.
The Principle of Regenerated Energy in a Lift system • Potential energy is constantly being transferred while the car is moving. • If, a lift is travelling down full and the load weight (people inside) is larger than the counterweight, then the motor torque is opposite direction to the speed i.e., the motor is braking • In the same way, when the lift is going up with light load, the motor is braking to prevent the car from coming up very fast due to heavy counterweight. • This braking energy is the regenerated energy which is typically dissipated in a resistance and it can be saved if the motor is controlled with a regenerative drive. • It is possible if the motor acts as a generator and is directly connected to the grid or depending on the typology allows the braking energy to be injected back to the power network
Lift motor operating modes (fM ‐ Motor force ; v ‐ Speed ) (source: ISR‐UC
The Principle of Regenerated Energy in a Lift system
Regenerative operation of a lift equipped with a regenerative inverter (source: Mitsubishi) Theoretically, if there were no losses, the regenerated energy would be equal to the motoring energy.
Total Energy= Mechanical Energy+ Auxiliary Energy- Regenerative energy However, there are still losses due to the existence of • friction losses (e.g. friction in the guide rails, air resistance), motor losses (e.g. the copper • losses, the iron losses) • and, in geared systems, losses in the gearbox (this is especially significant in systems equipped with worm gears where the efficiency in the reverse direction is considerably • lower than in the forward direction). • Illumination circuit, car illumination, socket on car roof, car fan, emergency call and telephone monitoring, backup power supply. Hence we can represent the energy regenerated as
Total Energy= Mechanical Energy+ Auxiliary Energy+Losses -Regenerative energy
Manufacturer’s Claims For • lifts capacity ranging from 650-2500 kg • lift speeds 1.5m/s to 2.5 m/s • Number of starts 1000-1500 / day • Condition: fully loaded
S. No.
Manufacturer
Low rise (below 30 stories)
Mid rise (30-80stories)
High rise (80 and above)
1.
OTIS
60%
50%
75%
2.
Mitsubishi
60%
50%
70%
3.
Kone
60%
65%
75%
Hypothesis
1.
Lifts having high capacity will have more energy consumption. These will also produce more regenerative energy.
2.
Regenerative drive will be more efficient in high rise buildings compared with low-rise buildings.
Methodology
Literature Review and comparative study based on OTIS data
Live case study 1: NHC towers by Kone- understanding the regenerated energy- new construction
Live case study 2: Fuji Xerox towers by Mitsubishi – retrofit construction
Comparative analysis
Conclusion and hypothesis validation
History of Elevators
Type of Elevator
Year
Speed
Load
Steam-powered-1st 1857 Passenger elevator
0.2 m/s
450 kg
Hydraulic Power
1867
2.5 m/s
Direct connected Geared Elevator
1889
Traction
1903
2.5 m/s
Gearless
1922
7 m/s
675 kgPassengers 1125 kg-Freight
Calculation of energy consumption using Doorlard and Schroeder’s Method Doolard’s method • •
Energy consumed by each elevator when it makes a round trip is considered. Comparison between the different elevator drive technologies.
Schroeder’s method •
An estimate for the daily energy consumption of the elevator can be made. The daily energy consumed (Ed) is: Ed = R x ST x TP /3600 where: R is motor rating ST is daily number of starts TP is trip time factor
Drawbacks of Doolard and Schroedar methods • • •
Proven to be inconsistent by almost a factor of two. These methods are only suitable for rule of thumb calculations, and for making comparative assessments between different configurations. They cannot assess the benefits of regenerative drives, different roping arrangements, different efficiency motors or gearboxes, and so on.
Calculation of energy consumption using ISO formula ISO FORMULA E(total) = Z x k1 x k2 x hmax x Pm / v x 3600 + Standby Energy E = Annual Energy Consumption Z = Number of starts k1 = Average Load factor K2 =Height factor Pm=Motor Power v= Speed of lift
SCOPE OF ISO METHOD OF CALCULATION a) a method to estimate energy consumption based on measured values, calculation, simulation on an annual basis for traction, hydraulic and positive drive lifts . b) energy classification system for new, existing, and modernized traction, hydraulic .
DRAWBACKS OF THE ISO METHOD ISO doesn’t take the following into consideration : a) hoistway lighting; b) heating and cooling equipment in the lift car; c) machine room lighting; d) machine room heating, ventilation, and air conditioning; e) non-lift display systems, CCTV security cameras, etc.; f) non-lift monitoring systems (e.g. building management systems, etc.); g) effect of lift group dispatching on energy consumption; h) environmental conditions; i) consumption through the power sockets; j) lifts whose travel includes an express zone.
Hypothetical Cases Considered to arrive at the energy consumption of lifts and the possible regenerated energy Assumptions Standby power considered = 0.6 Kw Speed of Hydraulic lift = 1m/s Speed of Gear lift =1.3m/s Speed of Gearless lift =2m/s Percentage of Regenerated Energy considered = 20% to 40%(Source: OTIS)
CASE 1 Height of building :60m
OFFICE Hydraulic = 147600 x 0.3 x 0.5 x 60 x 16.7 / 1 x 3600 = 2,21,84,280/ 3600 = 6162.3+ 5256 = 11418.3 kWh Energy Regenerated =2283.33 kWh
Gear
= 147600 x 0.3 x 0.5 x 60 x 12.7 / 1.3 x 3600 = 17265960 / 4680= 3689.3 + 5256 = 8860.84 kWh Energy Regenerated =3544.33 kWh
Gearless = 147600 x 0.35 x 0.5 x 60 x 11.7 / 2 x 3600 = 1,81,32,660 / 7200= 2518.42 + 5256 = 7774.42 kWh Energy Regenerated = 3109.76 kWh
OFFICE
Type of elevator
Annual energy consumption (in kWh)
Energy Regenerated(in Kwh)
Hydraulic
11418.3
2283.33
Gear
8860.84
3544.33
Gearless
7774.42
3109.76
Type of elevator
Annual energy consumption (in kWh)
Energy Regenerated(in Kwh)
Hydraulic
11774.9
2354.98
Gear
10072.59
4029.03
Gearless
8233.10
3293.24
RESIDENTIAL
Constants: Standby power considered = 0.6 kW
CASE 2 : HEIGHT OF BUILDING : 90M OFFICE Type of elevator
Annual energy consumption (in kWh)
Energy Regenerated(in Kwh)
Hydraulic
14,499.45
2899.89
Gear
10,663.26
4265.30
Gearless
9033.63
3613.45
Type of elevator
Annual energy consumption (in kWh)
Energy Regenerated(in Kwh)
Hydraulic
15,034.35
3006.87
Gear
12,480.89
4992.35
Gearless
9,721.66
3888.66
RESIDENTIAL
ELECTRICITY COST Type : Residential Height of building : 60 m Type of elevator
Energy Consumption by 1 lift (in kWh)
Energy Regenerated ( in kWh)
Cost Before Regeneration (SGD)
Cost After Regeneration (SGD)
Savings per lift (SGD)
Hydraulic
11,774.9
2354.98
2000
1665.45
334.55
Gear
10072.59
4029.03
1780.80
1068.5
712.30
Gearless
8233.10
3293.24
1455.61
873.36
582.25
Height of building : 90 m Type of elevator
Energy Consumption by 1 lift (in kWh)
Energy Regenerated ( in kWh)
Cost Before Regeneration (SGD)
Cost After Regeneration (SGD)
Savings per lift (SGD)
Hydraulic
15,034.35
3006.87
2658.07
2126.45
531.62
Gear
12,480.89
4992.35
2206.62
1323.97
882.65
Gearless
9,721.66
3888.66
1718.78
1031.27
687.50
Live Case Study 1 National Heart Centre, Singapore
Project Detail GFA No. of storey Year of Completion Building use Total no. of Lifts
– 48,000 sq. m – 12 storey – 2014 – Hospital – 12 no. (10 are regenerative lifts, served from Basement 3 to Level 12)
Live Case Study 1, NHC Six months data from NHC Type of Lift
Passenger Lifts
Service lifts
Capacity
Speed (m/s)
Sep-2015 (kWh)
Oct-2015 (kWh)
Nov-2015 (kWh)
Dec-2015 (kWh)
Jan-2016 (kWh)
Feb-2016 (kWh)
PL1
24 Persons (1630 kg)
2.5
270.309
297.666
274.013
280.448
234.088
215.557
PL2
24 Persons (1630 kg)
2.5
314.498
352.751
303.433
297.985
278.837
244.236
PL3
24 Persons (1630 kg)
2.5
226.034
248.874
219.127
218.302
194.862
156.439
PL4
18 Persons (1225 Kg)
2.5
175.689
199.471
178.624
189.916
176.986
161.681
SL1
35 Perons (2400 kg)
2.5
818.056
879.04
796.705
792.208
789.682
689.432
SL2
35 Perons (2400 kg)
2.5
804.366
881.428
783.608
832.012
762.033
743.654
SL3
24 Persons (1630 kg)
2.5
482.108
536.809
512.931
500.654
527.484
441.987
SL4
24 Persons (1630 kg)
2.5
591.638
624.33
582.021
599.463
656.018
610.763
Comparing energy consumption on six months
900
Energy Consumption (kWh)
800 700
When the capacity is bigger (the speed = constant), the energy consumption of lifts become larger.
600 500 400 300 200 100 Sep-15 PL1
Oct-15 PL2
PL3
Nov-15 PL4
Dec-15
Month SL1
SL2
Jan-16 SL3
Feb-16 SL4
Live Case Study 1, NHC Manual calculation to determine the energy regenerated
Type of Lift
Capacity
Speed (m/s)
Energy Consumed
Total Energy Consumption = Mechanical Energy + Auxiliary Energy –Regenerative Energy
PL1
24 Persons (1630 kg)
2.5
For Passenger Lifts (PL 1) calculation
PL2
24 Persons (1630 kg)
2.5
PL3
24 Persons (1630 kg)
2.5
PL4
18 Persons (1225 Kg)
2.5
SL1
35 Persons (2400 kg)
2.5
SL2
35 Persons (2400 kg)
2.5
SL3
24 Persons (1630 kg)
2.5
SL4
24 Persons (1630 kg)
2.5
For peak hours NHC Operation Hours (8am – 5pm) (Assuming for the people who wants to consult with doctors, 9:00am to 9:30am // 3:00pm to 3:30pm) Visiting hours – (12:00pm to 2:00pm // 5:00 pm to 8:30 pm) (Assuming for the people who visit their patient in NHC, 12:00pm to 12:30pm // 7:00pm to 7:30pm)
Service and Staff lifts
Jan-2016 (kWh) 234.088
278.837 %
Energy Regenerated Energy Consumed
194.862 %
Energy Regenerated Energy Consumed
176.986 %
Energy Regenerated Energy Consumed
789.682 %
Energy Regenerated Energy Consumed
762.033 %
Energy Regenerated Energy Consumed
527.484 %
Energy Regenerated Energy Consumed Energy Regenerated
% of saving %
Energy Regenerated Energy Consumed
Passenger Lifts
Traffic Patterns (considering diversity factor)
Item
656.018 %
For low traffic (at night) (8:30pm to 8:00am) (50% of the full load ) For normal hours – 70% of the full load
ME = KE + PE = ½ mv2 + mgh
• 100% full load capacity (peak 2 hours) Mechanical Energy = ½ x 1630 x 2.52 + 1630 x 9.81 x 60 = 964511.75 Nm = 0.27 kWh (1kWh = 3600,000 Nm) = 0.54 kWh/day (x2) = 14.04 kWh/ month (x26)
• 70% of the full load capacity (normal 10:30 hrs) Mechanical Energy = ½ x 1141 x 2.52 + 1141 x 9.81 x 60 = 4108855.1 Nm = 0.18kWh = 1.89 kWh/day (x10.5) = 49.14 kWh/ month (x26)
• 50% of the full load capacity (11:30 hrs at night) Mechanical Energy = ½ x 815 x 2.52 + 815 x 9.81 x 60 = 482255.875 Nm = 0.13 kWh = 1.495 kWh/day (x11.5) = 38.87 kWh/ month (x26)
Live Case Study 1, NHC Auxiliary Energy = =
Energy consumed by lighting + circuit (data from the supplier) 1 kWh + 3kWh = 4kWh/ month
Total Energy Consumption = Mechanical Energy + Auxiliary Energy – Regenerative Energy 234.088 = 102.05 + 4 – RE RE = -128.038 kWh % of saving
= 35%
For Staff and Service Lifts (PL 1) calculation For peak hours NHC Operation Hours (8am – 5pm) Morning (8:00am to 8:30am), before lunch (12:00pm to 12:30pm), after lunch (1:00pm, 1:30pm), Evening (5:306:00pm) For low traffic (at night) (9:00pm to 6:00am) (50% of the full load ) For normal hours – 70% of the full load • 100% full load (peak 2 hours) Mechanical Energy = 20.28 kWh/month
Regenerative Energy
=
% of saving
=
-626.302 kWh
44%
• 70% of full load capacity (normal 13 hrs) Mechanical Energy = 94.64 kWh/ month (x26)
• 50% of full load capacity (9 hrs at night) Mechanical Energy = 44.46 kWh/month
Live Case Study 1, NHC Capacity
Speed (m/s)
PL1
24 Persons (1630 kg)
2.5
PL2
24 Persons (1630 kg)
2.5
PL3
24 Persons (1630 kg)
2.5
PL4
18 Persons (1225 Kg)
2.5
SL1
35 Persons (2400 kg)
2.5
SL2
35 Persons (2400 kg)
2.5
SL3
24 Persons (1630 kg)
2.5
SL4
24 Persons (1630 kg)
2.5
Type of Lift
Passenger Lifts
Service and Staff lifts
Item Energy Consumed Energy Regenerated Energy Consumed Energy Regenerated Energy Consumed Energy Regenerated Energy Consumed Energy Regenerated Energy Consumed Energy Regenerated Energy Consumed Energy Regenerated Energy Consumed Energy Regenerated Energy Consumed Energy Regenerated
Jan-2016 (kWh) 234.088 128.038 278.837 172.787 194.862 88.812 176.986 94.466 789.682 626.302 762.033 602.653 527.484 418.184 656.018 546.718
% of saving 35%
Percentage of Saving
38%
31%
SL
35%
4
44%
3 2
44%
1
PL
44% 46%
0%
10%
20%
30%
40%
50%
Energy saving of eight lifts on Jan-2016 900
Energy (kWh)
800
•
Compared with passenger lifts, the service and staff lifts have high capacity and seems to have heavy traffic. More savings are found in service lifts.
•
Energy consumption and energy regenerated is most influenced by the traffic flows.
700 600 500
400 300
The savings of eight regenerative lifts are within 31% - 46% (Kone claim that energy consumption of lifts with regenerative drive can be reduced to 60%) •
200 100 0 PL 1
PL 2
PL 3
PL 4
SL 1
SL 2
Type of lifts Energy Consumed Energy Regenerated
SL 3
SL 4
Live Case Study 2 – Fuji Xerox Tower
Car Park Lift 1 (B3-2flr)
Car Park Lift 2 (B3-2 flr)
Low Rise Zone (3-15 flrs)
High Rise Zone (15, 29-38 flrs)
Service Lifts (B3-15 flr)
Mid Rise Zone (15, 24-28 flrs)
Note: 15-24 flrs - void
Floor Plan Retrofitting – Lift Modernization with Regen Drives GFA – 47,000 sqm Height – 38 storeys Commissioned – 1987 No. of Lifts - 16 (12 with Regen) Original & Retrofit – Mitsubishi Elevators Retrofitting Period - Jun 2012 – Oct 2014 Developer – CDL Major Tenants – Fuji Xerox / Prudential / Watsons
Lift Zoning: Low Rise Zone – 3rd to 15th floor Mid Rise Zone – 3rd, 15th, 24th to 28th floor High Rise Zone - 3rd, 15th, 29th to 38th floor Car park Lifts – B3 to 3rd flr (no regen) Service Lifts - B3 to 15th flr (no regen)
Live Case Study 2 – Fuji Xerox Tower Zone
No. of Lifts No. of Stops
Motor
Capacity
Speed (m/s)
Before
After
Regen Drive
Low Rise (Upto 15 flrs)
4
14
1155 kg (17 persons)
3
Thyristor
VVVF
Yes
Mid Rise (Upto 28 flrs)
4
6
1155 kg (17 persons)
5
Thyristor
VVVF
Yes
High Rise (Upto 38 flrs)
4
12
1155kg (17 persons)
7
Thyristor
VVVF
Yes
Car Park Lifts (Upto 2 flrs)
2
6
815 kg (11 persons)
1
AC-Geared
VVVF
No
Service Lifts (Upto 15 flrs)
2
17
1600 kg (20 persons)
1.5
AC-Geared
VVVF
No
18,000.00
Jul 2012 to Oct 2014 – Lift Modernization
•
Observed that the energy consumption is reduced after introduction of modern technology in lifts.
Lift Modernization Period
16,000.00
12,000.00 10,000.00 8,000.00
6,000.00 4,000.00 2,000.00
Car Park (kWh)
Car Park (kWh)
Service Lift (kWh)
Low Rise Zone (kWh)
High Rise Zone (kWh)
Mid Rise Zone (kWh)
Feb '16
Jan '16
Dec '15
Nov '15
Oct '15
Sep '15
Jul '15
Aug '15
Jun '15
May '15
Apr '15
Mar '15
Feb '15
Jan '15
Dec '14
Nov '14
Oct '14
Sep '14
Aug '14
Jul '14
Jun '14
May '14
Apr '14
Mar '14
Feb '14
Jan '14
Dec '13
Nov '13
Oct '13
Sep '13
Aug '13
Jul '13
Jun '13
May '13
Apr '13
Mar '13
Feb '13
Jan '13
Dec '12
Nov '12
Oct '12
Sep '12
Aug '12
0.00 Jul '12
Energy Consumption (kWh)
14,000.00
Live Case Study 2 – Fuji Xerox Tower • Jul 2012 to Oct 2014 – Lift Modernization • Oct 2013 to Oct 2014 – Regen Drive Activation
18,000.00 16,000.00 14,000.00
10,000.00 8,000.00 6,000.00 4,000.00 2,000.00
Lift Modernization Period
Low Rise Zone (kWh)
Phase-wise Activation of Regen Drive
Jan '16
Nov '15
Sep '15
Jul '15
May '15
Mar '15
Jan '15
Nov '14
Sep '14
Jul '14
May '14
Mar '14
Jan '14
Nov '13
Sep '13
Jul '13
May '13
Mar '13
Jan '13
Nov '12
Sep '12
0.00
Jul '12
Energy Consumption (kWh)
12,000.00
High Rise Zone (kWh) Mid Rise Zone (kWh)
Live Case Study 2 – Fuji Xerox Tower Comparing Annual Energy Consumption from 2013 to 2015
Reduction in Energy Consumption for three zones 16000
35000
14000
30000
12000
25000
10000
20000
2013
max kWh
8000
min kWh
2014
15000
2015
6000
10000 4000 5000
2000
0
0 High Rise
Mid Rise
Jan Feb Mar Apr May Jun
Low Rise
Maximum Energy Consumption (kWh)
Minimum Energy Consumption (kWh)
% of reduction
High rise
15236.47
5564.60
63%
Mid rise
9570.87
3956.56
59%
Low rise
5649
3617.94
36%
Obviously, Regenerative drive is more efficient in high-rise buildings compared to low rise as expected.
Jul
Aug Sep Oct Nov Dec
From 2013 to 2015, there is a 57 % decrease in energy consumption. As 3-10% is the lift energy consumption in a building, assuming 8% is this energy, with the application of regen drive, total lift energy consumption in a building shall reduce by 4.56%
Case Study Results 1. Literature Review. Different heights (60m and 90m) %Regenerated energy specified by Otis for various heights 2. NHC. different load conditions. Speed and height constant (60 m) Capacity
1630 kg
2400 kg
Energy saving 30%-38%
45%
3. Fuji Tower. different height and speed conditions. Load is constant (1155kg) Height Energy saving
Zone1 (42m) Zone 2 (84m)
Zone 3 (114m)
36%
63%
59%
Result Interpretation 1. 2. 3.
78-86 % more energy regenerated when number of floors increased from 20 stories to 30 stories There is 10%-15 %increase in energy saving as the capacity increases by 700-800 kg There is 20% increase in energy saving as the height goes up from low rise to mid rise and further increase in 5% as the height goes up from mid to high rise
Conclusion • Regenerative drives are considerable more efficient in high to super high structures with high capacity and high traffic.