1. Energy Saving Options
Electricity

2. Electricity Generation

3. Electricity Generation
During Electricity Generation,
thermal energy is converted to work.
The process is subject to the Carnot
principle

4. Carnot Principle Heat Supplied, Qs at Ts W = Qs -Qr Efficiency = W/ Qs
(Q = m cp T)
So, Efficiency = Ts -Tr Ts
Work, W
Heat Rejected, Qr at Tr
(Temperatures in degrees K)

5. Efficiency: Heat to Work
If Ts = 600oC (steam)
= 873 K
and Tr = 350 oC
= 623 K
Efficiency =
873
= %
Thus, 71.4% of the heat
energy is rejected to the
environment
Heat Supplied, Qs at Ts
Work, W
Heat Rejected, Qr at Tr
(Temperatures in degrees K)

6. Supply Capacity

7. The maximum kVA that can be taken from an electricity mains
Supply Capacity
The maximum kVA that can be
taken from an electricity mains
supply cable is limited by a fuse.
Utilities charge a fixed amount
monthly for each kVA of
available supply capacity

8. Maximum Demand

9. The kVA being taken by the supply cable is measured continuously,
Maximum Demand
The kVA being taken by the supply
cable is measured continuously,
or at given intervals.
The user pays a premium to the
electrical utility according to the
maximum value of kVA
(the maximum demand)
which occurs during the month

10. The Reduction of Maximum Demand
The user should monitor the kVA readings
to ascertain
when the peak occurs
and its magnitude

11. The user will then be in a position to reduce maximum demand charges by
identifying activities that contribute to maximum demand
rescheduling activities that occur at maximum demand time (peak lopping)
staggerong start-up times
using stand-by generators to peak-lop
maximising power factors
switching-off plant when not required

12. The Reduction of Maximum Demand
It should be noted that each kW
saved by electricity conservation,
also saves 1 kVA
of maximum demand charges

13. Electric Motors and Variable Speed Drives

14. Electric Motors ac Both the efficiency and the power factor of
an electric motor vary with the load
The largest potential savings with electric
motors is to match motor to load so that the
motor runs at maximum efficiency ac

15. Electric Motors ac A survey of all motors at a site should
be made and efficiencies estimated.
Those motors which are too large should
be changed.
Many times this involves swapping motors
around the plant and buying only a few
new motors ac

16. Variable Speed Drives ac In situations where the load on the motor
fluctuates, the use of variable speed
drives should be considered to avoid
large heat losses at lower loads ac

17. Fans and Ducts
DUCT
AIR
FAN

18. Fans and Ducts Power = flow rate of fluid x specific volume of fluid
x pressure rise across fan
/fan efficiency ac

19. To Reduce Power Requirements
Fans and Ducts
To Reduce Power Requirements
1. Reduce flow-rate of fluid
2. Decrease pressure drop
in the duct ac

20. Flow Control can be achieved in two ways:
Fans and Ducts
Flow Control can be achieved in two ways:
1. A damper can be
used to restrict the flow
2. The fan speed can be altered ac

21. Reducing Head Losses (Pressure Drops) restrictions, filters, dampers
Fans and Ducts
Reducing Head Losses (Pressure Drops)
Minimise
bends and elbows
restrictions, filters, dampers
and frictional forces

22. Pumps and Pipes
PIPE
LIQUID
PUMP

23. Pumps and Pipes feed water pumps chilled water pumps
condensate return pumps
oil pumps
process fluid pumps
cooling tower water pumps

24. Pumps and Pipes Power = flow rate of fluid x specific volume of fluid
x pressure rise across pump
/ pump efficiency ac

25. To Reduce Power Requirements
Pumps and Pipes
To Reduce Power Requirements
1. Reduce flow-rate of fluid
2. Decrease pressure drop in the
pipe ac

26. and similarly, Flow Control can be achieved in two ways:
Pumps and Pipes
and similarly, Flow Control can be achieved in two ways:
1. A flow control valve can be
used to restrict the flow, just
as a duct damper
2. The pump speed can be altered
just as the fan speed ac

27. Pumps and Pipes
Considerations of selecting optimal pumps and speeds to match pipe flow rates are exactly as for fans and ducts.

28. Reducing Head Losses (Pressure Drops)
Pumps and Pipes
Reducing Head Losses (Pressure Drops)
Minimise
bends and elbows
restrictions, orifices, valves
vertical rises
frictional forces

29. Compressors

30. Compressors Work in = pressure energy + change in internal energy
m cp dT = pV
+ m cv dT
m cp dT = m R dT
cp = R + cv
for air,
1005 =
J/kg K
m = mass of gas
cp,cv = specific heats at
constant pressure
and volume
p = pressure
dT = change in
temperature
R = characteristic gas
constant

31. Compressors Thus 1005 units of work are required to produce
287 units of pressure energy, even at 100%
efficiency of compression.
Furthermore, the work (electricity) has been
produced in the first place in the conversion
of heat to work at 30% efficiency.

32. So it requires at least 3350 units of heat energy to produce 287
Compressors
So it requires at least 3350 units
of heat energy to produce 287
units of pressure energy,
or 11.7 units of heat for 1 unit of
pressure energy.

33. Compressors
Compressed air is the most expensive energy commodity and should only be used as a last resort.
Question every use for compressed air.
It certainly should not be used for swarf
blowing and cleaning purposes.

34. Compressors check conditions of plant check efficiency
check position of inlet duct
check maintenance procedures
check control arrangements
check the amount of compressed gas supplied
check delivery temperature and pressure
check for leaks

35. Compressors check uses for compressed gas
check pressures at points of use
reduce generating pressure to minimum
consider interstage cooling
consider interstage bleed-off at different pressures
consider the use of localised booster compressors
switch off compressors when not in use

36. Compressors
consider the introduction of compressed gas accumulation so that off-peak electricity can be used or to peak lop maximum demand
use outside air/water for cooling/intercooling
recover heat from cooling and intercooling

37. Compressors
avoid condensation and concomitant blockage of pipelines
reheat compressed gas to increase discharge pressure
meter compressed air usage
look for heat recovery opportunities

38. Lighting

39. Lighting check zonal lighting requirements zone lighted areas
check that parts of the building are not being lit unnecessarily
use infra-red detectors/time switches
check the maintenance procedures
replace lamps when their efficiency drops
check lighting controls
use automatic controls

40. Lighting challenge the need for large areas of glazing
eliminate glazing
obtain economic balance of artificial lighting and day-lighting
use separate circuits for day-lighted peripheries
use separate circuits for use outside working hours

41. Lighting check colours of room surfaces
check conditions and cleanliness of luminaires and windows
keep windows and roof-lights clean
avoid dark background colours
never use low-efficiency filament lamps
use low-energy fluorescent or discharge lamps
look for heat recovery opportunities

42. Refrigeration and Air Conditioning

43. Refrigeration and Air Conditioning
check maintenance and operating procedures
evaluate load patterns and operating cycles
check conditions of plant and equipment
check for and seal leaks
check insulation levels and conditions of insulation
consider the use of thermal (cold) storage

44. Refrigeration and Air Conditioning
check operation of condenser fans
check cleanliness of heat transfer surfaces
check water treatment systems
check cooling tower operation
check control arrangements
check operating temperatures and pressures
look for heat recovery opportunities

45. Refrigeration and Air Conditioning
Select proper design points - temperature and humidity - thermal comfort chart
Select minimum airchange rates - vent off pollutants at source
check control arrangements
check that heating and cooling systems cannot conflict
reduce heating and cooling loads
check zonal requirements

46. Refrigeration and Air Conditioning
check for unoccupied areas
consider zoning, partitioning, false ceilings and destratifiers
minimise infiltration
look for opportunities for heat recovery
check insulation levels
isolate system from the surroundings

47. On-site Cogeneration

48. On-site Cogeneration Examine the annual heating and power requirements
for the site and consider whether the on-site
generation of power with use of the heat generated
might be an economic option.
Such a system could also produce refrigeration
via an absorption refrigeration system using the
heat rejected from the power generator