Tools for Energy Efficiency in Industrial Processes

1
Tools for Energy Efficiency in Industrial
Processes

• Richard Love and Don Cleland
• Centre for Postharvest and Refrigeration Research
• MASSEY UNIVERSITY

2
Overview

• What tools are needed for industrial energy
  efficiency?
• Case studies audits of chilled water plants.
• Case study monitoring report of chilled water
  plant.

3
Industry Contributes to National Energy
Consumption

• Hang (2006).

4
33
41
10
13
4
4
Energy Efficiency

• Important for sustainable use of renewable
  resources.
• Savings may be economically important.
• Efficiency gains decrease total energy use even
  if demand increases (due to other factors) energy
  efficiency decreases total impact.

5
Functional Vs Critical Measures

• Functional measures (e.g. /kg, kWh/km)
• useful for aggregates,
• generic,
• meaning ambiguous,
• retrospective,
• does not help improve performance.
• Critical measures (e.g. energy audit)
• why energy was used,
• how can energy be used better,
• large data-processing problem,
• technically complicated,
• site specific.

6
Benchmarks

• Energy efficiency is a comparison
• thermodynamic limits (eg. Carnot cycle)
• ? best for design
• historical performance (regresssion model)
• sector best practice
• mechanistic performance model
• ? best for operation

7
Industrial Chilled Water

• Used for process cooling air conditioning.

8
Chilled Water System
Condensers
Compressors
Chillers
Tanks
To site demand
From site demand
9
Industrial Chilled Water

• Performance model generated for 16 chilled water
  plants, and validated against plant data.
• Model used to evaluate savings opportunities.

Energy savings opportunities at sixteen chilled
water plants (not cumulative).
Opportunity Energy Saving
Discharge pressure set-point too high 6-15
Water chiller heat exchanger performing below specification 3-11
Convert chilled water storage tank to a stratified tank 16-30
Improved control strategies 15-22
10
Lower Discharge Pressure

• A simple set point change.
• Main problem equipment is operated at design
  (hottest day), rather than best configuration for
  actual conditions.
• Secondary problem condenser fouling and
  short-circuiting.

energy use
product
suction low temperature
11
Size of Chiller Heat Exchangers
low operating cost
low capital cost
12
Other Opportunities
Part loading of compressors is inefficient. ?
too many compressors active control
strategies ? mixing of supply and return water
stratified tanks
Condensers Compressors Chillers Tanks
From site demand
To site demand
13
Common Problems

• Poorly documented plant modifications.
• Meters missing.
• Unclear what some meters measured.
• Meters not calibrated.
• Data incorrectly archived.
• Problems due to low priority and lack of analysis.

14
Implementation

• Audits are half the battle. Recommendations need
  to be implemented.
• Education overcomes staff reluctance.
• Capital projects wont be implemented on a
  sustainability criteria, alone.

15
Monitoring Reports

• Weekly reports.
• Purpose
• remind
• educate
• identify
• evaluate
• Both functional and critical measures reported.

16
Problems

• Data.
• Meaning of targets.
• Disagreement about how to fix plant.

17
Conclusions

• Critical measures of energy use are preferred for
  energy saving.
• Data integrity is important.
• Analyst needs to be technically informed.
• On-going monitoring needed to realize savings.
• Site education and clearly explained targets
  critical.

18
Acknowledgements

• Federica Vaino