Plant Energy Balance

Effective Energy Management

• Develop baseline– Utility analysis– Plant energy balance– Lean energy analysis (LEA)

• Take action – Identify and quantify energy saving opportunities– Prioritize energy saving opportunities– Implement energy saving opportunities

• Measure and benchmark to sustain efforts– Develop metrics for system energy efficiency– Measure energy efficiency improvement with sliding NAC– Compare energy efficiency between facilities with NAC

Plant Energy Balance• Energy Balance: Ein – Eout = DEstored

• Plant Energy Balance: Where does Ein go?

• In some cases, detailed sub-metered data may be available.

• However, a useful approximation can be derived from the method that follows.

• This chapter shows how to calibrate approximate the energy use by equipment against total energy input using the energy balance concept.

• This information is helpful in

– focusing efforts on large energy users

– calibrating engineering models of equipment

Ein E,out

Efficiency

• Pinput – Plost – Puseful,output = 0 • Energy efficiency is defined as the

ratio of useful power output to total power input.

• Efficiency = Puseful,output / Pinput

Pin Puseful,out

Plost

• Many pieces of energy using equipment are rated by energy or power output. Thus, energy input is:

• Einput = Euseful,output / Efficiency

Electricity Energy Balance:Data Supplied By Facility

Number Type Rated Fraction OperatingOutput Power Loaded Hours

(hp, kW or tons) (hours/year)10 40-hp stamping machines 40 0.50 4,0004 50-hp chilled water pumps 50 0.75 6,000

200 400-W MH Lights 0.465 1.00 7,0001 100-ton chiller 100 0.50 4,0001 20-hp cooling tower fan 20 0.75 3,5002 100-hp air compressors 100 0.90 6,000

Electricity Energy Balance

Example: E = 10 motors x 40 hp/motor x 50% / 90% x 4,000 hr/yr x 0.746 kW/hp E = 663,111 kWh/yr

Number Type Rated Fraction Operating Effi ciency Conversion Annual FractionOutput Power Loaded Hours Energy Use Total

(hp, kW or tons) (hours/year) (kWh/year) Energy10 40-hp stamping machines 40 0.50 4,000 0.90 0.746 663,111 25.5%4 50-hp chilled water pumps 50 0.75 6,000 0.90 0.746 746,000 28.7%

200 400-W MH Lights 0.465 1.00 7,000 1.00 1.000 651,000 25.0%1 100-ton chiller 100 0.50 4,000 1.00 0.800 160,000 6.2%1 20-hp cooling tower fan 20 0.75 3,500 0.90 0.746 43,517 1.7%2 100-hp air compressors 100 0.90 6,000 0.90 0.746 895,200 34.4%

Total Listed Equipment 2,495,717Other Equipment 104,283 4.0%Measured Total 2,600,000

Electricity Energy Balance:Sorted from Highest to Lowest

Fuel Energy Balance:Data Supplied By Facility

Number Type Rated Fraction OperatingOutput Loaded Hours

(Btu/hour) (hours/year)2 Boilers 3,000,000 0.80 6,000

15 Hanging unit heaters 100,000 1.00 3,0002 Make-up air units 2,000,000 0.70 3,0001 Dry-off ovens 1,600,000 0.60 6,000

Example:E = 2 boilers x 3 mmBtu/hr-boiler x 80% x 6,000 hr/yr / 80% E = 36,000 mmBtu/yr

Fuel Energy Balance

Number Type Rated Fraction Operating Effi ciency Annual FractionOutput Loaded Hours Energy Use Total

(Btu/hour) (hours/year) (mmBtu/year) Energy2 Boilers 3,000,000 0.80 6,000 0.80 36,000 60.0%

15 Hanging unit heaters 100,000 1.00 3,000 0.80 5,625 9.4%2 Make-up air units 2,000,000 0.70 3,000 1.00 8,400 14.0%1 Dry-off ovens 1,600,000 0.60 6,000 0.85 6,776 11.3%

Total Listed Equipment 56,801Other Equipment 3,199 5.3%Measured Total 60,000

Fuel Energy Balance:Sorted from Highest to Lowest