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Tips for Thermal Energy Conservation


GENERAL
  • Undertake regular energy audits.
  • Plug all oil leakage. Leakage of one drop of oil per second amounts to a loss of over 2000 litres/ years.
  • Filter oil in stages. Impurities in oil affect combustion.
  • Pre-heat oil, for proper combustion, oil should be at right viscosity at the burner tip. Provide adequate Pre-heat capacity.
  • Incomplete combustion leads to wastage of fuel. Observe the colour of smoke emitted from chimney. Black smoke indicates improper combustion and fuel wastage. White smoke indicates excess air & hence loss of heat. Hazy brown smoke indicates proper combustion.
  • Use of Low air pressure "film burners" helps save oil upto 15% in furnaces.
FURNACE
  • Recover & utilize waste heat from furnace flue gases for preheating of combustion air. Every 210C rise in combustion air temperature results in 1% fuel oil savings.
  • Control excess air in furnaces. A 10% drop in excess air amounts to 1% saving of fuel in furnaces. For an annual consumption of 3000 kl of furnace oil, this means a saving of Rs.3 Lakhs.

    (Cost of Furnace oil-Rs.10 per litre).
  • Reduce heat losses through furnace openings. Observations show that a furnace operating at a temperature of 10000C having an open door (1500mm X 750 mm) results in a fuel loss of 10 lit/hr. For a 4000 hrs. furnace operation this translates into a loss of approx. Rs.4 lakhs per year.
  • Improve insulation if the surface temperature exceeds 200C above ambient. Studies reveal that heat loss from a furnace wall 115 mm thick at 6500C amounting to 2650 Kcal/m2/hr can be cut down to 850 kcal/m2/hr by using 65 mm thick insulation on the 115 mm wall.
  • Proper design of lids of melting furnaces and training of operators to close lids reduce losses by 10 – 20% in foundries.
BOILER
  • Remove soot deposits when flue gas temperature rises 400C above the normal. A coating of 3mm thick soot on the heat transfer surface causes an increase in fuel consumption up to 2.5%.
  • Recover heat from steam condentsate. For ever 60C rise in boiler feed water temperature through condendsate return, there is 1% saving in fuel.
  • Improve boiler efficiency. Boilers should be monitored for flue gas losses, radiation losses, incomplete combustion, blow down losses, excess air etc. Proper control can decrease the consumption upto 20%.
  • Use only treated water in boilers. A scale formation of 1mm thickness on the waterside increases fuel consumption by 5-8%.
  • Stop steam leakage. Steam leakage from a 3mm-diameter hole on a pipeline carrying steam at 7kg/cm2 wastes 32 kl of fuel oil per year amounting to a loss of Rs.3 lakhs.
  • Maintain steam pipe insulation. It has been estimated that a bare steam pipe, 150mm in diameter and 100m in length, carrying saturated steam at 8kg/cm2 wastes 25 kl of furnace oil in a year amounting to an annual loss of Rs.2.5 lakhs.
DG SETS
  • Maintain diesel engines regularly.
  • A poorly maintained injection pump increases fuel consumption by 4gm/kWh.
  • A faulty nozzle increases fuel consumption by 2gm/kWh.
  • Blocked filters increase fuel consumption by 2gm/kWh.
  • A continuously running DG set can generate 0.5 Ton/Hr of steam at 10 to 12 bar from the residual heat of the engine exhaust per MW of the generator capacity.
  • Measure fuel consumption per Kwh of electricity generated regularly. Take corrective action in case this shows a rising trend.
TIP FOR ELECTRICAL ENERGY CONSERVATION

GENERAL
  • Improve power factor by installing capacitors to reduce KVA demand charges and also line losses within plant.
  • Improvement of power factor from 0.85 to 0.96 will give 11.5% reduction of peak KVA and 21.6% reduction in peak losses. This corresponds to 14.5% reduction in average losses for a load factor of 0.8.
  • Avoid repeated rewinding of motors. Observations show that rewound motors practically have an efficiency loss of upto 5%. This is mainly due to increase in no load losses. Hence use such rewound motors on low duty cycle applications only.
  • Use of variable frequency drives, slip power recovery systems and fluid couplings for variable speed applications such as fans, pumps etc. helps in minimizing consumption.
ILLUMINATION
  • Use of electronic ballast in place of conventional choke saves energy upto 20%.
  • Use of CFL lamp in place GLS lamps can save energy upto 70%.
  • Clean the lamps & fixtures regularly. Illumination levels fall by 20-30% due to collection of dust.
  • Use of 36W tubelight instead of 40 W saves electricity by 8 to 10%.
  • Use of sodium vapour lamps for area lighting in place of mercury vapour lamps saves electricity upto 40%.
COMPRESSED AIR
  • Compressed air is very energy intensive. Only 5% of electrical energy is converted to useful energy. Use of compressed air for cleaning in rarely justified.
  • Ensure low temperature of inlet air. Increase in inlet air temperature by 30C increases power consumption by 1%.
  • It should be examined whether air at lower pressure can be used in the process. Reduction in discharge pressure by 10% saves energy consumption upto 5%.
  • A leakage from a 1/2" dia hole from a compressed air line working at a pressure of 7kg/ cm2 can drain almost Rs.2500 per day.
  • Air output of compressors per unit of electricity input must be measured at regular intervals. Efficiency of compressors tends to deteriorate with time.
REFRIGERATION & AIR CONDITIONING
  • Use of double doors, automatic door closers, air curtains, double glazed windows, polyester sun films etc. reduces heat ingress and air conditioning load of buildings.
  • Maintain condensers for proper heat exchange. A 50C decrease in evaporator temperature increases the specific power consumption by 15%.
  • Utilisation of air conditioned/refrigerated space should be examined and efforts made to reduce cooling load as far as possible.
  • Utilize waste heat of excess steam or flue gases to change over from gas compression systems to absorption chilling systems and save energy costs in the range of 50-70%.
  • Specific power consumption of compressors should be measured at regular intervals. The most efficient compressors to be used for continuous duty and others on standby.
COOLING TOWERS
  • Replacement of inefficient aluminum or fabricated steel fans by moulded FRP fans with aerofoil designs results in electricity savings in the range of 15-40%.
  • A study on a typical 20 ft. dia fan revealed that replacing wooden blade drift eliminators with newly developed cellular PVC drift eliminators reduces the drift losses from 0.01-0.02% with a fan power energy saving of 10%.
  • Install automatic ON-OFF switching of cooling tower fans and save upto 40% on electricity costs.
  • Use of PVC fills in place of wooden bars results in a saving in pumping power of upto 20%.
PUMPS
  • Improper selection of pumps can lead to large wastage of energy. A pump with 85% efficiency at rated flow may have only 65% efficiency at half the flow.
  • Use of throttling valves instead of variable speed drives to change flow of fluids is a wasteful practice. Throttling can cause wastage of power to the tune of 50 to 60%.
  • It is advisable to use a number of pumps in series and parallel to cope with variations in operating conditions by switching on or off pumps rather than running one large pump with partial load.
  • Drive transmission between pumps & motors is very important. Loose belts can cause energy loss upto 15-20%.
  • Modern synthetic flat belts in place of conventional V-belts can save 5% to 10% of energy.
  • Properly organized maintenance is very important. Efficiency of worn out pumps can drop by 10-15% unless maintained properly.







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