Case Background
A semiconductor manufacturing company’s cleanroom workshop requires its air handling unit (AHU) to continuously supply 10,000 m³/h of clean air. The system was originally designed to use a set of standard-sized high-efficiency panel filters with an effective filtration area of 2.5 m².
- Design Airflow: 10,000 m³/h
- Original Filtration Area: 2.5 m²
- Calculated Airflow Velocity: Airflow / Area = 10,000 / 3600 / 2.5 ≈ 1.11 m/s (a common design velocity)
Now, considering an energy-saving retrofit, a V-shaped high-efficiency filter is adopted, which can increase the effective filtration area to 5.0 m² within the same installation space.
- New Filtration Area: 5.0 m²
- Calculated Airflow Velocity: Airflow / Area = 10,000 / 3600 / 5.0 ≈ 0.56 m/s
Cost Comparison Analysis
We assume the following:
- Electricity Cost: 1 CNY per kWh
- System Annual Operating Hours: 8,000 hours
- Fan Efficiency: 60%
- Filter Final Resistance: Set to double the initial resistance when replacement is required.
1. Initial Resistance Comparison
- Original Scheme (1.11 m/s): Initial resistance is approximately 225 Pa
- New Scheme (0.56 m/s): Initial resistance is approximately 110 Pa (resistance is roughly proportional to airflow velocity)
2. Operational Energy Consumption Comparison
The fan shaft power formula is: N = (Airflow × Static Pressure) / (3600 × Fan Efficiency)
We mainly focus on the additional energy consumption due to the difference in filter resistance.
- Original Scheme Annual Electricity Consumption:
Average operating resistance: (225 Pa + 450 Pa) / 2 = 337.5 Pa
Annual electricity consumption: (10,000 m³/h × 337.5 Pa) / (3600 × 0.6) × 8000h ≈ 1,250,000 kWh
Electricity cost: 1,250,000 CNY
- New Scheme Annual Electricity Consumption:
Average operating resistance: (110 Pa + 220 Pa) / 2 = 165 Pa
Annual electricity consumption: (10,000 m³/h × 165 Pa) / (3600 × 0.6) × 8000h ≈ 611,111 kWh
Electricity cost: 611,111 CNY
- Annual Electricity Savings: 1,250,000 – 611,111 = 638,889 kWh
Annual electricity cost savings: 638,889 CNY
3. Filter Life and Replacement Cost Comparison
At low airflow velocities, filter life is significantly extended. Assuming a filter life of 12 months at 1.11 m/s.
- Life Estimation: Life is proportional to dust holding capacity, which significantly increases at low airflow velocities. Empirically, halving the airflow velocity can extend life by 2.5 to 3 times. We take the conservative value of 2.5 times.
New Scheme Life: 12 months × 2.5 = 30 months (2.5 years)
- Original Scheme Replacement Cost:
Assuming a set of filters costs 5,000 CNY.
Number of replacements in 5 years: 5 times
Total filter cost over 5 years: 5,000 × 5 = 25,000 CNY
- New Scheme Replacement Cost:
Assuming the V-shaped filter, due to its complex structure, costs 8,000 CNY.
Number of replacements in 5 years: 5 years / 2.5 years = 2 times
Total filter cost over 5 years: 8,000 × 2 = 16,000 CNY
4.Year Filter Procurement Cost Savings: 25,000 – 16,000 = 9,000 CNY
(This does not yet account for the reduced labor and downtime costs due to fewer replacements)
5-Year Total Cost Data Comparison
| Cost Item | High Airflow Scheme | Low Airflow Scheme | 5-Year Savings |
| Energy Cost (Electricity) | Energy Cost (Electricity) | 611,111 CNY/year × 5 years = 3,055,555 CNY | 3,194,445 CNY |
| Filter Procurement Cost | 25,000 CNY | 16,000 CNY | 9,000 CNY |
| 5-Year Total Cost | 6,275,000 CNY | 3,071,555 CNY | 3,203,445 CNY |
1. Significant Energy Savings: In this case, simply by increasing the filtration area to reduce airflow velocity, over 3.19 million CNY in electricity costs can be saved over five years. The energy-saving effect is extremely significant and represents the largest source of cost savings.
2. Material and Labor Savings: The filter replacement frequency drops from 5 times in 5 years to 2 times, not only saving procurement costs but also reducing the workload of maintenance personnel and related operational management costs.
3. Environmental Benefits: Over five years, approximately 3.19 million kWh of electricity is saved, equivalent to reducing several thousand tons of carbon emissions. Additionally, by replacing filters three fewer times, solid waste generation is reduced.
4. Quick Payback on Initial Investment: Although the V-shaped filter is more expensive per set (8,000 CNY vs. 5,000 CNY), the operational cost savings make the payback period very short. The additional 3,000 CNY in procurement costs can be fully recovered in the first month’s electricity savings alone.
Therefore, this is a very real and common scenario in the industrial field: investing more upfront for higher efficiency and larger filtration area filters ultimately brings significant economic returns and environmental benefits.
Post time: Sep-01-2025