Baselining & Data Logging

Establishing a baseline allows you to quantify improvements and detect degradation in the compressed air system.

What is a Baseline

The baseline is a snapshot of current system performance:

                    BASELINE
                        │
    Consumption ────────┼──────────────────────
    (kWh)               │     Improvement implemented
                        │            │
                        │     ┌──────┴──────┐
    ████████████████████│█████│░░░░░░░░░░░░░│
                        │     │  Measurable │
                        │     │   savings   │
    ────────────────────┼─────┴─────────────┴────► Time
                   Before      After

Baseline Parameters

Required Data

Parameter	Unit	Frequency
Electrical consumption	kWh	Daily
Air flow	CFM-h	Continuous
System pressure	psi, bar	Continuous
Operating hours	h	Daily
Production (reference)	units	Daily

Measurement Period

Operation Type	Minimum Period
Continuous production 24/7	1 week
Single shift, 5 days	2 weeks
Variable production	4 weeks
Seasonal	3-6 months

Performance Indicators

Key KPIs

┌─────────────────────────────────────────────────────────┐
│              KEY PERFORMANCE INDICATORS (KPIs)          │
├─────────────────────────────────────────────────────────┤
│                                                          │
│  1. SPECIFIC POWER                                      │
│     kW / 100 CFM (or kW / m³/min)                       │
│     Target: < 20 kW/100 CFM                             │
│                                                          │
│  2. UNIT COST                                           │
│     $/1000 CF produced                                  │
│     Benchmark: $0.20-0.30                               │
│                                                          │
│  3. ENERGY INTENSITY                                    │
│     kWh / unit of production                            │
│     Depends on process                                  │
│                                                          │
│  4. LEAK FACTOR                                         │
│     % of total consumption                              │
│     Target: < 10%                                        │
│                                                          │
└─────────────────────────────────────────────────────────┘

Specific Power Calculation

$$SP = \frac{\sum kW_{\text{compressors}}}{Q_{\text{total}} / 100}$$

Example:

• Compressor 1: 55 kW, 250 CFM
• Compressor 2: 45 kW, 200 CFM
• Compressor 3: 30 kW, 150 CFM (standby, 0 kW, 0 CFM)

$$SP = \frac{55 + 45}{(250 + 200) / 100} = \frac{100}{4.5} = 22.2 \text{ kW/100 CFM}$$

Data Logging

Sampling Frequency

Sampling vs. Averages:

Sample every 1 second:
    │    ●
    │   ● ●
    │  ●   ●    ●
    │ ●     ●  ● ●
    │●       ●●   ●
    └──────────────── t

Average every 1 minute:
    │  ████████
    │  ████████
    └──────────────── t

The average hides peaks and valleys

Parameter	Sampling	Storage
Pressure (control)	1 sec	1 min average
Flow	1 sec	1 min average
Power	1 sec	1 min average
Temperature	10 sec	5 min average
Dew point	1 min	15 min average

Importance of Fast Sampling

Pressure drop event:

1 min sampling:                    1 sec sampling:
    │                                  │
 100├────────────────                100├────────●
    │                                  │        ╲
  90├────────────────                 90├────────╲
    │                                  │          ●
  80├────────────────                 80├──────────╲●
    │ (doesn't detect the spike)       │ Detects the
    └────────────────── t              └──drop────── t

The problem's cause may be invisible with slow sampling.

Data Normalization

By Production

Intensity = Air kWh / Units produced

Month 1: 100,000 kWh / 50,000 units = 2.0 kWh/unit
Month 2: 95,000 kWh / 45,000 units = 2.1 kWh/unit
                                      ↑
                                Got worse (even though kWh dropped)

By Ambient Conditions

Temperature correction:

$$CFM_{\text{corrected}} = CFM_{\text{measured}} \times \sqrt{\frac{T_{\text{standard}}}{T_{\text{actual}}}}$$

Example:

• Measured: 1000 CFM at 95°F (35°C)
• Standard: 68°F (20°C)

$$CFM_{\text{corr}} = 1000 \times \sqrt{\frac{528}{555}} = 976 \text{ CFM}$$

By Discharge Pressure

Higher pressure means higher energy consumption:

$$kW_{\text{normalized}} = kW_{\text{measured}} \times \left(\frac{P_{\text{standard}}}{P_{\text{measured}}}\right)^{0.286}$$

Example:

• Measured: 75 kW at 115 psig
• Normalize to 100 psig:

$$kW_{\text{norm}} = 75 \times \left(\frac{100}{115}\right)^{0.286} = 72.1 \text{ kW}$$

Data Analysis

Load Profile

Typical 24-hour profile:

kW
│
80├                    ████████
│                 █████████████████
70├              ██████████████████████
│          ███████████████████████████
60├      ██████████████████████████████████
│    ████████████████████████████████████████
50├ ████████████████████████████████████████████
│████                                        ████
40├
│
└────┴────┴────┴────┴────┴────┴────┴────┴────┴───► Hour
   0    3    6    9   12   15   18   21   24
        ↑                           ↑
    Night minimum            Production peak
    (leaks + base)

Leak Calculation

$$\% \text{ Leaks} \approx \frac{\text{Minimum night consumption}}{\text{Peak consumption}} \times 100$$

Example:

• Night consumption (0-5 AM): 40 kW
• Peak consumption (9 AM-5 PM): 80 kW

$$\% \text{ Leaks} \approx \frac{40}{80} \times 100 = 50\%$$

This is very high! Target: $< 10\text{-}15\%$

Baseline Report

Minimum Content

Section	Content
Measurement period	Dates, duration
Equipment included	Inventory, capacities
Measured data	Tables, graphs
Calculated KPIs	SP, costs, efficiency
Conditions	Production, weather
Observations	Anomalies, events

Summary Example

════════════════════════════════════════════════════════════
            BASELINE - COMPRESSED AIR SYSTEM
                   Period: March 1-7, 2024
════════════════════════════════════════════════════════════

EQUIPMENT:
  3 rotary screw compressors: 2×100 HP + 1×75 HP
  2 refrigerated dryers
  Total installed capacity: 275 HP

MEASUREMENTS:
  Total period consumption:     25,200 kWh
  Average flow:                 620 CFM
  Average pressure:             105 psig
  Operating hours:              168 h

INDICATORS:
  Specific power:               21.5 kW/100 CFM
  Unit cost:                    $0.28/1000 CF
  Estimated leak factor:        35%

COMPARISON WITH BENCHMARK:
  Current SP:     21.5 kW/100 CFM
  Benchmark:      18.0 kW/100 CFM
  Potential:      16% improvement

════════════════════════════════════════════════════════════

Continuous Monitoring

Energy Management System

┌─────────────────────────────────────────────────────────┐
│              CONTINUOUS MONITORING SYSTEM               │
│                                                          │
│   Meters ─────────┐                                     │
│                   ▼                                     │
│              ┌─────────┐                                │
│              │ Gateway │                                │
│              └────┬────┘                                │
│                   ▼                                     │
│   ┌───────────────┴───────────────┐                    │
│   │          DATABASE             │                    │
│   │   Historical data, trends     │                    │
│   └───────────────┬───────────────┘                    │
│                   │                                     │
│       ┌───────────┼───────────┐                        │
│       ▼           ▼           ▼                        │
│   Dashboard    Reports     Alerts                      │
│                                                          │
└─────────────────────────────────────────────────────────┘

Automatic Alerts

Condition	Threshold	Action
SP greater than benchmark +10%	22 kW/100 CFM	Email to operations
Leaks greater than 20%	Night consumption	Maintenance alert
Low pressure	less than 95 psig	Alarm
Degraded efficiency	5% trend	Weekly report

Continuous Improvement

The baseline is not static. Update after each significant improvement and compare against the previous baseline to quantify the real benefit.