Industrial Energy Efficiency - Two main goals
Political and social target —> GHG emissions reduction
Industrial target: Savings of energy costs
Holistic approach of energy efficiency
—> Optimization of the inputs (Natural Gas and Electricity)
—> Optimization on industrial plant level
Energy Conversion - Industrial utilities and applications
Energy Conversion - Approaches to alternatives
Green field
Rare in practice
Fundamental new ideas with high energy savings
Solutions often not feasible for integration as retrofits
Brown field
Usually in practice
Solutions often not technical feasible (e. g. lack of installation space)
Solutions often not economic feasible (e. g. high costs, high production loss)
—> In practice most plants are already build —> Realization: Retro fits and brown field approaches
Cross Cutting Technologies
—> Can be found in every industrial plant
—> Therefore energy efficiency concepts have a high impact
Drives, pumps and ventilators
Lighting
Mechanical motion
HVAC
Supplying thermal energy (process heating and cooling)
Drives
70 % of industrial electricity demand
> 90 % of life cycle costs due to elecricity
Classifications by International Electrotechnical Commission (IEC) —> new
and Committee of Manufacturers of Electrical Machines (CEMEP) —> old
Efficiencies: Super premium, premimium,…. worse than state of the art
Energy Conversion
Pump - life cycle costs
Higher complexity —> higher investment and maintenance costs
Main influence on efficiency and energy costs —> system design and control strategy
Runtime: 3000 h/a over 7 years
Pump and Drive vs. Plant
Drives and Pumps
Throttle valve control
—> Full load: Efficiency 67 %
—> Part load: Efficiency 13 %
Variable speed drive
—> Full load: Efficiency 63 %
—> Part load: Efficiency 45 %
Types (after efficacy)
LED (200 lm/W)
Metal halide (150 lm/W)
Fluorescent
CFL
Mercury
Halogen (25 lm/W)
Incadescent
Saving potentials fluorescent lamps
Increasing potential of various measures
Fluorescent lamp with…
conventional ballast (initial state)
low-loss ballast (initial state)
electronic ballast
dimmable electronic ballast + day light control system
dimmable electronic ballast + day light control system + motion detector to verify presence
—> Also saving potentials from T8 (26 mm) to T5 HE (16 mm)
Mechanical Power - Types
Compressed air
Electromechanical linear motors
Mechanical Power - Compressed air
Definitions of pressure
Composition of costs
7 % of the industrial electricity demand
—> Absolute pressure: measured from absolute zero and relevant for all theorectical considerations
—> For industrial praxis: Measure gage pressure to atmospheric pressure is relevant
Tools
Usable energy
System Design
Progress automation based: Pneumatic tools —> Linear or rotatory cylinders
Very low investment costs
Applied in explosion safe zones
Very low efficiency in relation to the applied final energy
13 % of the input energy is usable mechanical energy
Losses: Motor, compression, cooling,…
Rules of thumb
Temperature change of + 10 K —> 2 - 4 % more energy input
Target pressure drop
Treatment: < 0,6 bar
Pipe system: < 0,1 bar
Connection accessories: < 0,3 bar
Pressure change of + 1 bar —> 6 - 10 % more energy input
Audible leakages from 1 mm2 (annual costs of 500 €)
Acceptable leakage losses
Max. 5 % for small networks
Max. 7 % for medium networks
Max. 10 % for large networks
Max. 15 % for very large networks
Increasing the efficiency of a compressed air system
—> Potential for efficiency measurements: 33 %
—> Target should be optimization and substitution
Optimization of compressor
Usage of compressor’s waste heat
Minimization of leakages
Substitution of applications (electronic devices like linear motor)
Mechanical Power - Electromechanical linear motors
Pro and Cons
+ Lower operating costs
+ Simple installation only electricity needed
+ Compact
- Less robust
- Higher investment costs
- Not explosion proof
Mechanical Power
Comparison compressed air vs. electro mechanics
Thermal Power - The Onion Layer Model
Layers
Heat recovery
Energy storage
Industrial Utilities
Thermal Power - Process Integration
Thermal Energy = Heat and cold
Pinch Analysis —> Tools for analyzing and optimizing thermal systems
Thermal Power - Pinch Basics
Pinch analysis
—> Provides theoretically possible potential for heat integration —> Often technical limitations
Stream
Flow requires heat or cold —> don’t change composition
Cold stream
Flow starts cold, needs heat
Hot stream
Flow starts hot, needs cold
Reaction
No stream
Changes temperature and composition
Example
Thermal Power - Energy Target
Composite Curve
Thermal Power - Rules of pinch analysis
External heat input above the pinch —> Because subsystem above the pinch has a heat deficit
External heat removal below pinch —> Because subsystem below the pinch has a heat surplus
No heat transfer across the pinch —> Or the heat is missing above the pinch and increases the heat deficit
Thermal Power - Types
Furnace
CHP
Electrical heating
Heat pump
Compressed cooling machine
Ab/Adsorption cooling machine
Thermal Power - Furnace
High exergetic fuels for low exergetic heat production
Fuel is burned —> Heat from flame and exhaust gas —> Water
High temperature steam can be extracted —> Depends on the pressure
Definition Exergy
Exergy or Availability
= Amount of useful work you can get out of the system at a specified state by placing a reversible heat engine between it and the dead state
Thermal Power - CHP Types
CHP —> 66 % better fuel usage
Types
Motor - Generator
Gas turbine - Generator
ORC turbine - Generator
Steam turbine - Generator
Fuel cell
Thermal Power - CHP
Exergetic benefits
Electricity as the main driver for economic values
Heat is important for efficiency
Emissions depends on the fuel
Thermal Power - Electrical heating
Immersion heating
Resistor used
Large scale water boiler
Up to 200 °C
Difficult control system, minimum power required
Electrode Type
Electric current directly through water
Up to 350 °C
Easy to control through full bandwith of power
Thermal Power - Heat pump
—> Heat and Cold
Waste heat from the process —> transfered to a refrigerant
Electric energy —> gaseous refrigerant gets compressed —> Increase of pressure and temperature
Heat from refrigerant at high temperature —> Feed back into the process
Thermodynamic integration is significant for efficiency
Process
Thermal Power - Compression cooling machine
Ability to supply all year cooling with low flow temeratures
Refrigerant gets evaporated at low pressure and low temperature
Condensed above ambient temperature after compressing
Types: Reciprocating, scroll, screw, turbo compressors —> increasing power range
Thermal Power - Ab/Adsorption cooling machine
Dissolves vapour in a liquid (the absorbent)
Pumps the solution to a higher pressure in the regenerator
Uses heat to evaporate the refrigerant vapour out of the solution
Most common absorption cycle: Water as refrigerant and lithium bromide as the absorber
Most common adsorption cycle: Silicia gel, zerolites, slat
Mechanical compression —> Exergy 100 %
Thermal compression —> Exergy << 100 %
Share of exergy of heat changes with temperature (higher temperature, higher exergy —> logarithm)
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