Slides
4- Energy analysis
ENERGY ANALYSIS
4 – Energy analysis
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Structure of a company's energy system
Supply
Conversion
Distribution
Consumption
Heat recovery
Disposal
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4 – Energy analysis
Energy efficiency
Typical areas of improvement
 Cooling/refrigeration
 Heating
 Compressed air
 Insulation
 Heat recovery
 Separation processes
 Lighting
 ...
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4 – Energy analysis
Efficient energy use
Not only a question of best technology!
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4 – Energy analysis
Energy management
Organization
Analysis and
Planning
Set up an organizational unit,
identify responsibilities and determine the
budget
Inventory and description
of the energy situation
search for energy saving options
Control
Control of the energy plants,
work out energy indicators
Consulting
Energy reports,
internal consulting and market analysis
Implementation Implementation of energy saving options
maintenance of energy plants
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4 – Energy analysis
Documentation of load curves
Documentation of
curves for

A year

A week

A day
Analysis of load curves
Winter – summer ratio
Combined use of heat and
power
Switched off or reduced
operation at weekends
Days with high energy demand
Bottlenecks
Energy demand after
production
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4 – Energy analysis
Annual energy consumption
Collection and
documentation
for all energy carriers
Quantity
Cost
Reference quantities
Definition of indicators
Analysis and
interpretation
Distribution of quantities
Distribution of costs
Variation of indicators
Comparison of indicators
with other companies or
publications
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4 – Energy analysis
Analysis of consumers
Heat
Electric power
 Avoid partial load and use
adequate machines
 Separate control of plants
 Adapt power (e. g. fans)
 Adequate temperatures
 Optimize lights (cleaning,
 No internal sources of heat
modern lighting, analyse
and humidity in cooled areas
demand)
 Use shades for heat protection
 Clean and service (air filter,
 Frequency-controlled fans
nozzles, etc.)
 Use heat cascades
 Compressor location and
 ...
pressure
 Peak load management
 Thermostatic valves
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4 – Energy analysis
Heat losses detected
with an infrared camera
4 – Energy analysis
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Specific energy consumption
150
Example:
Energy consumption
of a brewery
125
Indicator:
MJ/hl
100
Measure:
90
91
92
93
94
June 1992
Installation of a vapour
recompression plant
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4 – Energy analysis
Energy, work and power
Work is the transmission of energy.
The unit of work and energy is JOULE.
The speed at which work is performed is power
[J/s = W].
4 – Energy analysis
Slides
Heat capacity
To heat up a body with a mass of m by DT, the following amount of
heat is required:
Q = c m DT
The specific heat capacity c
of the material depends
on the temperature.
Specific heat capacity
The specific heat capacity is the
amount of energy required
to heat up 1 kg of material by 1 °C.
Gold
Unit: [c] = 1 J.kg-1.K-1
Iron
Oxygen Benzene Water
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4 – Energy analysis
The performance of 1 kWh
Lifts 1 ton of steel by 367 m!
Accelerates a car (1 ton) to approx.
60 km/h (without losses 305 km/h)!
Heats up 1 000 l of water by 0.86
°C!
Source: Karl Lummerstorfer, Energie Institut Linz
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4 – Energy analysis
Efficiency in a steam system
Part of the steam system
Steam boiler
Efficiency
(70-) 82 – 90%
Steam transportation
75 – 90%
Heat exchange
85 – 98%
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4 – Energy analysis
Steam system
Reduce leaks.
Improve operation of steam traps.
Increase condensate recovery.
Increase flash steam recovery.
Use lower steam pressure if possible.
Use direct steam for heating if possible.
4 – Energy analysis
Slides
Cooling process
Efficiency = Qcond. / P ~ Tcond. / (Tcond. – Tevap.)
Consequences:
Q: Heat
P: Power
T: Temperature
The lower the temperature difference the better:
Check the necessary cooling temperature
Allow the temperature in the condenser to be as low as
possible (e.g. water cooling)
Maintain the heat exchanger (especially evaporator)
...
The higher the cooling temperature the better
Others:
Remove water from ground
Avoid high temperature of the incoming product
...
4 – Energy analysis
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Cooling process
P
Qu = Qo + P
M
Compressor
Qo
Evaporator
Qu
Condenser
To
Tu
Collector
Low pressure
High pressure
Efficiency = Qo / P = To / (Tu – To)
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4 – Energy analysis
Cooling and freezing
Raising the cooling temperature by 1 °C saves
approx. 4% of electric energy.
Choose the adequate temperature: frozen meat at
-20 °C, cooling at 0 °C to 4 °C.
Clean the condenser regularly and provide
sufficient cool air supply.
Use the capacity of the storage rooms, collect
goods, switch off unused cooling units.
Keep storage rooms closed to avoid entrance of
humidity and warm air.
Defrost cooling rooms.
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4 – Energy analysis
Cooling – 2
 Insulation
Recommendations
for PU-foam insulation:
Insulation thickness
0 to -8 °C 0 to -15 °C below -15 °C
80mm
110mm
150mm
 Evaporator:
Optimize
defrosting
 Compressor
Close
to evaporator
Central location makes servicing and use of heat easier
 Condenser:
Outside
of building, sun-protected
Clean regularly
 Use R134 a, R22 or ammonia
4 – Energy analysis
Slides
Drying process
•Fresh air drying
Q1
•Fresh air drying with heat recovery
8
•Circulating air drying with/without
heat recovery
Q4
Q3
Ti
•Heat recovery with condensation of humidity
(heat pumps, thermo-compression)
Td
Q2
QT
Typical options for improvement:
Q1 = Insulation of drier
Q2 = Pre-drying, pre-concentration of the product
Q3 = Control of temperature and humidity
Q4 = Heat recovery, humidity control of flue gas, good housekeeping
To
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Compressed air
 Shut down compressor, drier
and the network
 Reduce the pressure level
(as far as possible)
 Avoid leakages
 Lower the temperature of incoming air
 Avoid compressed air for cleaning
 Carry out maintenance
 Use electrically-driven equipment
 Foster heat recovery
Source: Karl Lummerstorfer, Energie Institut Linz
4 – Energy analysis
Slides
Lighting
 Turn off when not needed
 Use timer or motion detector
 Use daylight as much as possible
 Service and clean
 Clean windows, ensure efficient
design of rooms
 Use energy saving bulbs
4 – Energy analysis
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4 – Energy analysis
Heat recovery cooling units – 1
Air-cooled
condenser
Water-cooled
condenser
Evaporator
Compressor
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4 – Energy analysis
Heat recovery cooling units – 2
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4 – Energy analysis
ECOPROFIT-company: Brewery
Annual production: > 1 million hl, ISO 14000
 Saving of water, energy and
chemicals due to CP options:
Cold filtering/sterilization
New filling line
Heat/power co-generation
Vapour compression
 ...
4 – Energy analysis
Slides
Specific heat consumption
of a brewery
50.00
in kWh/hl
40.00
30.00
20.00
10.00
0.00
spec. heat
1993
1994
´95
´96
´97
´98
´99
2000
2001
2002
38.60
40.67
47.30
42.62
41.42
37.56
34.19
29.91
27.58
24.47
4 – Energy analysis
Slides
Multistage evaporation
1. evaporator
2. evaporator
1. vapour
3. evaporator
2. vapour
condenser
3. vapour
vacuum
pump
feed
steam
1. concentrate
steam
condensate
Source: Ignatowitz 1994
final
concentrate
2. concentrate
1. vapour
condensate
2. vapour
condensate
3. vapour
condensate
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4 – Energy analysis
Evaporation with vapour compression
evaporator
vapour
preheated
feed
pre-heater
steam
(start-up)
compressor
vapour-
condensate
feed
solution
Source: Ignatowitz 1994
concentrate