Energy ConservationEnergy Management

Role of an energy managerAssessCurrent energy demandEnergy auditAnalyseEnergy requirementsAdviseOn technical improvementsAdvertiseWays to save energyAccountFor energy consumption

Assess energy demandKeep recordsConsumptionTime of readingsTemperatureOther factors affecting demandWeekday/weekendSpecial eventsFrequency of readingsWeeklyDaily

Energy AuditFeasibility studyEstablish and quantify energy flows into and within a building or organisationAimIdentify viable and cost effective energy saving measuresEnhance operating efficiency and reduce maintenance costsEstablish a baseline energy consumptionProcessCollect data from energy invoices and metersSurveys of plant, equipment and buildingsCollect information from managers and other staff

Auditing processIdentify energy management opportunities

Can be no cost or low cost measuresChange an energy tariffChange an energy supplierReschedule production activities Preferential tariffsAdjust existing controls to match requirementsImplement good housekeeping policiesInvest in small capital itemsThermostats & time switches

Who does energy audits?Can be undertaken internally energy managerSpecialist energy consultantsEnergy service companiesPerformance contractsGuarantee organisations energy cost savings in return for a feeMain interest is in installing and managing their recommended plantMay arrange finance of projectsVested interest

Why is energy wasted?Poorly designed buildings and installationsInsufficient insulationUndersized ventilation ductsInadequate control systemsPoor control settingsInefficient plant operationOut of date technologyPoor maintenancePoor operating and working practices

Different types of energy auditAccording to level of detail and depth of analysis

Preliminary TargetedComprehensive

Preliminary auditHow much energy is being consumedWhat type of energyPerformance of facility compared with similar facilitiesCharacteristic performance of building

Preliminary energy auditIdentification of potential areas of energy savingFinancial energy audits

Collect data Establish quantity and cost of each form of energyData from energy invoices and meters for previous yearAnalyse dataPresent dataEstablish priorities Make recommendations

Targeted energy auditProvide data and analysis on specific targeted projectse.g. heating of one building or lightingDetailed survey of target areaAnalysis of energy flows and costsRecommendations for action

Comprehensive energy auditsSimilar to preliminary audits but in far more detailDetailed data on energy flows into and within organisation or facilityOften requires use of sub-metering to accurately determine component energy flowsOr estimate energy use(Plant power output (kWh)/efficiency of plant) *operating hours per yearUse of thermal imaging May use complex energy simulation softwareDetailed energy survey Energy project implementation plans

Collect dataBuild up picture of pattern of energy consumption and cost from energy invoicesAll invoices for relevant time periodDelivery notes for oil, solid fuel, LPGIdentify estimated meter readings check with previous yearsInadequate/unavailable invoices contact utility company/fuel supplierCollect geographic data Location, altitude, orientationWeather data, degree day dataManufacturing data (if appropriate)Production output Check data for anomaliesSmall building using more energy than larger oneHigh energy use at night when unoccupied

Understanding invoices: electricityDate of meter readingMonthly standing chargePresent and previous meter readingDaytime peak rateNight time off-peak rateCharges for each rateSome tariffs have a higher unit charge for first 1000 kWhMonthly maximum demand charge For every kW of the peak power demand during the monthPenalise users make heavy demands during peak periodsSupply capacity annual maximum demandMonthly chargeTotal cost + VAT

Gas invoicesMuch less complicated than electricityDate of meter reading or estimateCalorific value of gasPresent and previous meter readingsAmount of gas used ft3, kWh or thermsUnit price per kWhStanding chargeMonthly or quarterlyTotal cost + VAT

Other fuelsFuel oilMeasured by volumeVaries with temperature corrected to standard condition of 15.50CDate of deliveryUnit cost per standard litreCalorific value (?)Total cost + VAT

Solid fuelWeight deliveredDate of deliveryTotal cost + VATNo calorific value

Analysing energy recordsKey variablesHeatingExternal temperature - dominantWind speed )Humidity )

Data analysisMany different ways of analysing dataAnnual energy consumption Analysis of heating requirementsDegree day method Mean temperature methodCumulative deviation method(Details in Keiths lecture notes)Normalised performance indicators (NPI) (Beggs, 2002)Time dependent energy analysisLinear regression analysisCUSUM cumulative sum deviation method

Annual energy consumptionSimplest analysisAssess overall energy performance of building

Produces a percentage breakdown of annual energy consumption and cost dataConvert all energy consumption data into standard units (kWh) Standard conversion factors & gross calorific valuesPercentage breakdowns of total consumption and cost of each energy typePresent dataTotal annual energy consumptionCostPercentage breakdown of each fuel typeHistorical trends

Analysis of heating requirementsDegree day methodQuickerOil & coal heating difficult general estimates of consumption Mean temperature methodMore accuratePlot mean consumption against mean external temperature

Degree day methodTwo component partsTemperature relatedIndependent of temperatureHot water & cooking if by gasE = W + H*degree days*86400Where E is total energy consumedW energy for hot water + cooking (gas)W approx constant for given house 7-10 GJ/quarterH is heat loss rate for the homeTwo unknowns W & H, Know degree days & energy consumptionEstimate heat loss & steady energy requirement

Degree day method - exampleEnergy consumption 2 successive quarters31.76 & 18.80 GJCorresponding degree days1100 and 500

E = W + H * degree days*86400 1100 * H * 86400 + W = 31.76 (1) 500 * H * 86400 + W = 18.80 (2)Simultaneous equations (subtract 2 from 1)

H = (31.76 18.80) * 109 = 250 Watts (1100-500)*86400Substitute for H in either equation to get W

W = 31.76 * 109 - 1100 * 250 * 86400 = 8 * 109 = 8GJH - heat lossW - hot water

Degree day method Once H & W have been calculatedPerformance for subsequent quarters can be estimatedIf degree days for 3rd quarter = 400Consumption predicted to be 400 * 250 * 86400 + 8 * 109 = 16.64 GJIf actual consumption is 17.5 GJ then energy has been wasted

Mean temperature method (non electrical heating)Plot the mean consumption over a specific period against mean external temperatureFor 1 week or 1 day - less time than previous method

Analysis of lighting (non-electrically heated house)Lighting varies throughout the year with hours of darknessNeed to assess a realistic time for lightingThere is constant load (A) from appliances and refrigeration use and an increasing amount from lighting.Increase in lighting hours is used to obtain L & A in same way for H & W in heating example

Analysis of heating & lighting in an electrically heated houseMore complex as both H & L are unknownCombine A & W to give overall appliance + hot water load (A)E = (degree days * H + lighting hours * L) * 86400 + AWhere E = energy consumptionH = heat loss rateL = lighting (units of L are Watts per hour)A = appliance + hot water3 unknowns H, L & AIf we have data for 3 quarters Estimate values for H, L & A by solving 3 simultaneous equationsIf appliance load is known calculation is easier

Cumulative deviation methodNo energy conservation horizontal lineWinter following improved insulationSummer no savings heat conservation onlyWinter parallel to 2Summer - improved management of hot waterShould be (4) + (5) but less - energy conservation performance is reduced

Normalised Performance Indicators (NPIs)Provides an indication of the energy performance of a buildingCompares actual annual energy consumption and costs with those achieved by buildings of a similar type and functionProblemsBuildings may be different sizesLocations may have different climatesLocations may have different levels of exposureMaybe different operating hoursCorrect the building energy consumption data allow for variables such as occupancy and weather.NPIs developed to address these problems. Used tocompare with other buildings of a similar type and functioncompare with standard energy benchmark for different building typesBenchmarksMany countries have national energy benchmarks for different types of buildingsUsually kWh/m2 of floor area (volume)Provide guidance, not absolute values to achieve

How to calculate NPIsEstablish total building energy use in standard unitsCalculate the annual energy use for space heatingSub-metering, or analytical techniquesCorrect space heating energy data for climate & exposureWeather coefficient = std annual heating degree days/ annual heating degree days experienced by buildingExposure coefficientsSheltered (city centre) = 1.1Normal (urban/rural) = 1.0Exposed (coastal/hilly site) = 0.9Non-heating energy consumption + corrected space heating = non-time corrected energy consumptionTo calculate normalised annual energy consumption need to correct for hours of use non-time corrected energy consumption * coefficient Hours of use coefficient = std annual hours of use/actual annual hours of useNPI = normalised annual energy consumption/building floor area

Energy SurveysIntegral part of energy auditHelps to understand energy flows within a facility/buildingHelps to identify energy wastageCan be comprehensive or targetedObjectivesDetermine energy performance of facility/building or specific plant/equipmentIdentify and quantify the principal energy flows & energy cost savingsProduce costed recommendations to achieve energy cost savingsMake recommendations on future energy management of facility

What to include in an energy surveyManagement and operation characteristics of a facility or organisationEnergy supply to an organisations various facilities Energy use within an organisations facilitiesThe plant and equipment within a facilityThe fabric of the organisations buildings

Management and operating characteristicsManagement cultureCan have considerable influence on energy consumptionDetermine management structure and practices relating to energy procurement and consumptionIdentify cost centresAre the managers accountable for operating costs also responsible for energy consumption?Maintenance proceduresFrequency and qualityIdentify new maintenance measures to improve energy efficiency

Operating practices: data collectionUse of particular space or buildingMechanical/electrical services in buildingNumber & type of occupants e.g. stationary or activeOccupancy patternsEnvironmental conditionsAir temp, humidity, lightingOperating practices of plant/equipmentIdentify where actual practices deviate from that stated by managementOverheated rooms, open windows, computers left on

Energy SupplyIdentify tariffs and supply contracts of organisationEnsure organisation is using correct electricity tariff to suite its load profileCalculate load profileRegular meter readings include daytime, night time & weekendsFor large electrical loadsNeed to be more accurateMeasure every 30 mins, use portable meters if necessaryInvestigate large peaks in load

Plant and equipmentSurvey major items of plant and equipment to determine their operating efficiencyInclude pipe distribution networksBoilerstune to minimise flue gas heat lossIdentify if flue gas heat recovery is feasibleRefrigerationCheck efficiencyOpening practicesIs heat recovery feasiblePipeworkInsulation & leaksPlanned replacement of old plant

Building fabricIdentify using U values areas of greatest heat lossThermal imagingExcess ventilation open doors

Energy management: recommendationsRecommendations will relate to cost of fuel more interested in saving money than energy/carbonTechnicalInsulation, draft exclusion, thermostatic radiator valves, heating controlLow energy lighting, efficient refrigerationPower factor correctionsRelocation of switches, movement sensorsEnergy managementChecking performanceRecord keepingFinancialMake sub-sections responsible for their own energy budgetCarrots for those who save energyOther factorsChange patterns of workingWorking practicesUse of space