What does exhaust humidity control on a stenter save in fuel and power?
About 5% of the stenter's pet coke and power, in BEE's Pali report, which books it as 15.12 t and 15,120 kWh a year. Without the report's rounding, 5% of a 55 kg an hour, 55 kW stenter is 19.8 t and 19,800 kWh, about 76 t CO2. Cost Rs 3.65 lakh, payback about 1.5 years.
Why a dry exhaust wastes coke
Every kilogram of fresh air the exhaust fan pulls in has to be heated to chamber temperature. The report's target is 0.1 to 0.15 kg of water per kg of dry air in the exhaust; stenters left with dampers fully open are often found at 0.05, so they heat two or three times the air they need. Its rule of thumb: halve the fresh air from 10 to 5 kg per kg of fabric and stenter energy falls 57%. A humidity sensor in the duct sets the dampers and fan to keep the exhaust in that band.
What BEE costed
- Stenter: 70 m a minute, 24 hours, 300 days, 100,800 m a day; 55 kW of power and 55 kg an hour of residual pet coke.
- Saving: case studies showed 5 to 30%; the report takes 5%, booked as 5% more cloth for the same coke and power.
- Cost: two sensor and control sets at Rs 1.75 lakh each, Rs 0.15 lakh to fit: Rs 3.65 lakh.
- Report's figures: 15.12 t coke and 15,120 kWh, Rs 1.83 lakh a year at Rs 7,500 a tonne and Rs 4.6 a kWh, payback 2 years.
The rounding that hides a quarter of the saving
The report rounds coke and power per metre to 0.01 before multiplying. The real figure is 0.013: 1,320 kg and 1,320 kWh a day over 100,800 m. Taken straight, 5% of a year's 396 t and 396,000 kWh is 19.8 t and 19,800 kWh, worth Rs 2.40 lakh at the report's prices. Payback falls to about 1.5 years.
Before you order
- Check the exhaust fan actually runs. The audit found it switched off in most Pali units, with air leaving through the fabric exit; with no exhaust stream there is nothing for the sensor to control until the duct works.
- Do not add this to residual moisture control on the same stenter. Both reports count a faster cloth speed for the same heat, so the gains overlap.
- Log coke per shift and metres run for a month before and after. That is the evidence a lender or buyer can check.
One stenter, one year, without the rounding
- Power: 19,800 kWh x 0.675 = 13.4 t CO2
- Pet coke: 19.8 t x 3.17 = 62.8 t CO2
- Total: about 76 t CO2; the report says 54 t
- On the report's own 15.12 t and 15,120 kWh: 47.9 + 10.2 = 58 t
Pet coke at the IPCC 2006 default (97,500 kg CO2 per TJ at 32.5 GJ a tonne) and grid at CEA's FY 2025-26 factor, both estimates.
What Senseible does here
Senseible reads pet coke invoices and electricity bills into monthly records linked to each bill, with CO2 for the power. It has no pet coke factor, so apply the IPCC figure above to the tonnes. The green loan check covers what a lender wants for an efficiency retrofit.
- Green loan readiness check
- Stenter residual moisture control: CO2
- Stenter fuel and CO2 per metre
- Pet coke emission factor in India
Sources: BEE, Detailed project report: exhaust humidity measurement and control in stenter, Pali textile cluster (2010, SAMEEEKSHA), IPCC 2006 Guidelines, Volume 2 Energy, Tables 1.2 and 2.3, CEA CO2 Baseline Database, version 22.0
Last reviewed 2026-11-01. Report figures are from a BEE SME programme project report; costs and paybacks are at 2010 prices. Check today's coke and power prices and a current quote.