Testing Energy Efficiency

ENERGY AUDIT

               Energy Audit is the key to a systematic approach for decision-making in the area of energy management. It attempts to balance the total energy inputs with its use, and serves to identify all the energy streams in a facility. It quantifies energy usage according to its discrete functions. Industrial energy audit is an effective tool in defining and pursuing comprehensive energy management programme.

As per the Energy Conservation Act, 2001, Energy Audit is defined as "the verification, monitoring and analysis of use of energy including submission of technical report containing recommendations for improving energy efficiency with cost benefit analysis and an action plan to reduce energy consumption".

NEED FOR ENERGY AUDIT

            In any industry, the three top operating expenses are often found to be energy (both electrical and thermal), labour and materials. If one were to relate to the manageability of the cost or potential cost savings in each of the above components, energy would invariably emerge as a top ranker, and thus energy management function constitutes a strategic area for cost reduction. Energy Audit will help to understand more about the ways energy and fuel are used in any industry, and help in identifying the areas where waste can occur and where scope for improvement exists.

           

            The Energy Audit would give a positive orientation to the energy cost reduction, preventive maintenance and quality control programmes which are vital for production and utility activities. Such an audit programme will help to keep focus on variations which occur in the energy costs, availability and reliability of supply of energy, decide on appropriate energy mix, identify energy conservation technologies, retrofit for energy conservation equipment etc. In general, Energy Audit is the translation of conservation ideas into realities, by lending technically feasible solutions with economic and other organizational considerations within a specified time frame.

ENERGY EFFICIENCY

            Energy efficiency is a way of managing and restraining the growth in energy consumption. Something is more energy efficient if it delivers more services for the same energy input, or the same services for less energy input.

TESTING ENERGY EFFICIENCY

            A fully equipped lab is the pre-requisite to test the energy efficiency and assess the performance of thermal and electrical energy systems. Thermal energy systems which play a key role in energy guzzling are boilers, furnaces and heat exchangers while the energy guzzlers in case of electricity consumption are motors, fans, blowers, pumps, compressors and HVAC systems. The parameters to be considered and the testing methodologies are detailed below.

1.      THERMAL ENERGY SYSTEMS

1.1  BOILERS

            Performance of the boiler, like efficiency and evaporation ratio reduces with time, due to poor combustion, heat transfer fouling and poor operation and maintenance. Deterioration of fuel quality and water quality also leads to poor performance of boiler. Efficiency testing helps us to find out how far the boiler efficiency drifts away from the best efficiency.

Objective

·         To find out the efficiency of the boiler

·         To find out the Evaporation ratio

Calculation of boiler efficiency

            Boiler efficiency can be calculated by directed and indirect methods whereas the indirect method is highly efficient. The indirect method calculates the efficiency of a boiler by estimating the losses. The following losses are applicable to liquid, gas and solid fired boiler

L1– Loss due to dry flue gas (sensible heat)

L2– Loss due to hydrogen in fuel (H2)

L3– Loss due to moisture in fuel (H2O)

L4– Loss due to moisture in air (H2O)

L5– Loss due to carbon monoxide (CO)

L6– Loss due to surface radiation, convection and other unaccounted*.

*Losses which are insignificant and are difficult to measure.

The following losses are applicable to solid fuel fired boiler in addition to above

L7– Unburnt losses in fly ash (Carbon)

L8– Unburnt losses in bottom ash (Carbon)

Boiler Efficiency by indirect method = 100 – (L1 + L2 + L3 + L4 + L5 + L6 + L7 + L8)

 

Energy losses in a boiler

Table1.1. Typical instruments used for performance assessment of boiler

S.No.	Instrument	Type	Purpose
1.	Flue gas analyzer	Portable or fixed	% CO2 , O2 and CO
2.	Temperature indicator	Thermocouple, liquid in glass	Fuel temperature, flue gas temperature, combustion air temperature, boiler surface temperature, steam temperature
3.	Draft gauge	Manometer, differential pressure	Amount of draft used or available
4.	TDS meter	Conductivity	Boiler water TDS, feed water TDS, make-up water TDS.
5.	Flow meter	As applicable	Steam flow, water flow, fuel flow, air flow

1.2  FURNACES

            Furnace is by definition a device for heating materials and therefore a user of energy. The primary energy required for reheating / heat treatment (say annealing) furnaces are in the form of Furnace oil, LSHS, LDO or electricity.

Objective

·         To find out the efficiency of the furnace

·         To find out the Specific energy consumption

Measurement Parameters

The following measurements are to be made for doing the energy balance in oil fired reheating furnaces (e.g. Heating Furnace)

i) Weight of stock / Number of billets heated

ii) Temperature of furnace walls, roof etc

iii) Flue gas temperature

iv) Flue gas analysis

v) Fuel Oil consumption

Instruments like infrared thermometer, fuel consumption monitor, surface thermocouple and other measuring devices are required to measure the above parameters. Reference manual should be referred for data like specific heat, humidity etc.

Table1.2. Typical instruments used for performance assessment of furnaces

S.No.	Instrument	Type	Purpose
1.	Flue gas analyzer	Portable or fixed	% CO2 , O2 and CO
2.	Temperature indicator	Infrared thermometer, surface thermocouple	Fuel temperature, flue gas temperature, combustion air temperature, surface temperature

1.3  HEAT EXCHANGERS

            Heat exchangers are equipment that transfer heat from one medium to another. The proper design, operation and maintenance of heat exchangers will make the process energy efficient and minimize energy losses. Heat exchanger performance can deteriorate with time, off design operations and other interferences such as fouling, scaling etc. It is necessary to assess periodically the heat exchanger performance in order to maintain them at a high efficiency level.

Objective

·         To determine the overall heat transfer coefficient

Measurement of parameters

            The test and evaluation of the performance of the heat exchanger equipment is carried out by measurement of operating parameters upstream and downstream of the exchanger. Due care needs to be taken to ensure the accuracy and correctness of the measured parameter. The instruments used for measurements require calibration and verification prior to measurement.

Table1.3. Typical instruments used for performance assessment of heat exchangers

S.No.	Instrument	Type	Purpose
1.	Orifice flow meter, Vortex flow meter, Venturi meters, Coriollis flow meters, Magnetic flow meter	As applicable	Fluid flow measurement
2.	Thermo gauge, RTD	Thermo gauge for low ranges	Temperature measurement
3.	Liquid  manometers, raft gauge,  Pressure gauges, , Absolute Pressure transmitters,	Bourdon and diaphragm type	Pressure measurement
4.	Hydrometer	As applicable	Density measurement
5.	Viscometer	As applicable	Viscosity measurement
6.	Measured in the Laboratory as per ASTM standards	As applicable	Specific heat capacity measurement
7.	Measured in the Laboratory as per ASTM standards	As applicable	Thermal conductivity measurement
8.	Chemical analysis, HPLC, GC, Spectrophotometer	As applicable	Composition+

2.      ELECTRICL ENERGY SYSTEMS

2.1  MOTORS

            The two parameters of importance in a motor are efficiency and power factor. The efficiencies of induction motors remain almost constant between 50% and 100% loading.

Objective

·         To determine motor efficiency

·         To determine power factor

Table2.1. Typical instruments used for performance assessment of motors

S.No.	Instrument	Type	Purpose
1.	Eddy current dynamometer	As applicable
2.	Energy meter	As applicable	Energy consumption measurement
3.	Tachometer	As applicable	Speed measurement
4.	Ammeter	As applicable	Current measurement
5.	Voltmeter	As applicable	Voltage measurement

2.2  PUMPS

            Pumping is the process of addition of kinetic and potential energy to a liquid for the purpose of moving it from one point to another. This energy will cause the liquid to do work such as flow through a pipe or rise to a higher level. A centrifugal pump transforms mechanical energy from a rotating impeller into a kinetic and potential energy required by the system.

            The most critical aspect of energy efficiency in a pumping system is matching of pumps to loads. Hence even if an efficient pump is selected, but if it is a mismatch to the system then the pump will operate at very poor efficiencies. In addition efficiency drop can also be expected over time due to deposits in the impellers. Performance assessment of pumps would reveal the existing operating efficiencies in order to take corrective action.

Objective

•          Determination of the pump efficiency during the operating condition

•          Determination of system resistance and the operating duty point of the pump and compare the same with design.

Table2.2. Typical instruments used for performance assessment of pumps

S.No.	Instrument	Type	Purpose
1.	Flow meter	Ultrasonic, on-line, electromagnetic	Flow measurement
2.	Energy meter	As applicable	Energy consumption measurement
3.	Ammeter	As applicable	Current measurement
4.	Voltmeter	As applicable	Voltage measurement

2.3  COMPRESSORS

            The compressed air system is not only an energy intensive utility but also one of the least energy efficient. Over a period of time, both performance of compressors and compressed air system reduces drastically. The causes are many such as poor maintenance, wear and tear etc. All these lead to additional compressors installations leading to more inefficiency. Periodic performance assessment is essential to minimize the cost of compressed air.

Objective

• To determine Actual Free Air Delivery (FAD) of the compressor

• To determine isothermal power required

• To determine volumetric efficiency

• To determine Specific power requirement

            The actual performance of the plant is to be compared with design / standard values for assessing the plant energy efficiency.

Test arrangement for measurement of compressed air flow

Table2.3. Typical instruments used for performance assessment of compressors

S.No.	Instrument	Type	Purpose
1.	Thermometers or Thermocouple	As applicable	Temperature measurement
2.	Pressure gauges or Manometers	As applicable	Pressure measurement
3.	Differential pressure gauges or Manometers	As applicable	Differential pressure measurement
4.	Standard Nozzle	As applicable	Hydraulic purpose
5.	Psychrometer	As applicable	Humidity measurement
6.	Tachometer/stroboscope	As applicable	Speed measurement
7.	Electrical demand analyser	As applicable	Power requirement

2.4  HVAC

            Air conditioning and refrigeration consume significant amount of energy in buildings and in process industries. The energy consumed in air conditioning and refrigeration systems is sensitive to load changes, seasonal variations, operation and maintenance, ambient conditions etc. Hence the performance evaluation will have to take into account to the extent possible all these factors.

Objective

·         To estimate the energy consumption at actual load vis-à-vis design conditions

Measurements to be Recorded During the Test

            All instruments, including gauges and thermometers shall be calibrated over the range of test readings for the measurement of following parameters.

Evaporator

a. Temperature of water entering evaporator

b. Temperature of water leaving evaporator

c. Chilled water flow rates

d. Evaporator water pressure drop (inlet to outlet)

Compressor

e. Power input to compressor electrical power, kW

Table2.4. Typical instruments used for performance assessment of HVAC

S.No.	Instrument	Type	Purpose
1.	Thermometers or Thermocouple	As applicable	Temperature of water in evaporator and chilled water temperature measurement
2.	Pressure gauges or Manometers	As applicable	Pressure of water of air
3.	Energy meter	As applicable	Power input to compressor

2.5  LIGHTING SYSTEMS

            Lighting is provided in industries, commercial buildings, indoor and outdoor for providing comfortable working environment. The primary objective is to provide the required lighting effect for the lowest installed load i.e. highest lighting at lowest power consumption.

Objective

·         To calculate the installed efficacy in terms of lux/watt/m² (existing or design) for general lighting installation.

The calculated value can be compared with the norms for specific types of interior installations for assessing improvement options.

Table2.5. Typical instruments used for performance assessment of lighting systems

S.No.	Instrument	Type	Purpose
1.	Lux meter	As applicable	Illumination
2.	Energy meter	As applicable	Energy consumption measurement
3.	Ammeter	As applicable	Current measurement
4.	Voltmeter	As applicable	Voltage measurement