Energy Agreements Programme. HVAC Special Working Group. Report The Use of Energy Performance Indicators (EPIs) in HVAC Systems

Transcription

1 Energy Agreements Prgramme HVAC Special Wrking Grup Reprt The Use f Energy Perfrmance Indicatrs (EPIs) in HVAC Systems Prepared by - Dnall O Brien Industrial Utilities Ltd. Date: March

2 EXECUTIVE SUMMARY The varius spins f the HVAC SWG has highlighted the significance f the impact f HVAC systems t the verall energy intensity f the site. The HVAC SWG Spin II Reprt fr 2009 has shwn that HVAC can be respnsible fr up t 80% f sme facilities energy bill. The imprtance f having metrics t cmpare and challenge energy cnsumptin in HVAC systems is therefre f immense imprtance. The HVAC SWG Spin I reprt states that It was fund during the site audits that nly 35% f the participating cmpanies had verall EPIs t mnitr the energy perfrmance f their HVAC systems. It is therefre f imense imprtance t assist cmpanies in the develpment f EPI s t effectively manage the energy cnsumptin f this energy intensive service. Varius suggested energy perfrmance indicatrs were explred in the reprt. There is a lt f ptential infrmatin available n site t mnitr perfrmance but very rarely will ne system f indicatrs prvide the full picture f the energy efficiency f the HVAC system. Measurement f fan cnsumptin n a HVAC system whether its specific fan cnsumptin r a ttalised figure will nt give an indicatin f anything ther than the efficiency f distributing air thrugh the system. Likewise degree day analysis will nly address thermal heating r cling lads n a building/system. Unfrtunately there is n silver bullet slutin fr EPI s that will allw HVAC systems t be cmpared n a single indicatr due t the huge variatin in size and cmplexity f HVAC systems. Fr mst HVAC energy end-users, it will be a case f selecting EPI s that give as much infrmatin as pssible n the efficiency f their HVAC system with the minimum effrt in terms f the engineering/facilities team resurce input. Fr mst facilities this will undubtedly mean the selectin f a few key EPI s which will address the majr energy streams and back-up the EPI s with an peratinal cntrl check f the systems and equipment. The peratinal cntrl check will nt give a number which can be graphed peridically like a numerical EPI but will allw an peratr t make an assessment f the energy perfrmance f the system based n his/her knwledge f the systems and knwledge f where their ptimum perfrmance shuld be. 3

3 CONTENTS EXECUTIVE SUMMARY... 3! 1.0! INTRODUCTION... 3! 1.1! BACKGROUND... 3! 1.2! OBJECTIVE OF REPORT... 3! 1.3! METHODOLOGY... 3! 2.0! ENERGY PERFORMANCE INDICATORS (EPIS)... 4! 2.1! EPI DEFINITION... 4! 2.2! PROS AND CONS OF EPIS FOR HVAC... 4! 3.0! HVAC SYSTEMS ENERGY SERVICE REQUIREMENT & ENERGY FLOWS... 5! 3.1! HVAC ENERGY SERVICE REQUIREMENT... 5! 3.2! ENERGY FLOWS IN HVAC SYSTEMS... 6! 4.0! ENERGY PERFORMANCE INDICATORS SUGGESTED... 8! 4.1! SPECIFIC FAN CONSUMPTION... 8! 4.2! TOTALISED FAN CONSUMPTION... 8! 4.3! DEGREE DAY ANALYSIS... 8! 4.4! INDEPENDENT ASSESSMENT OF UTILITIES FEEDING A HVAC SYSTEM... 9! 4.4.1! Cnsumptin f Utilities by System... 9! 4.4.2! Efficiency r COP f Utility System... 9! 4.5! SUMMARY OF COMPLEXITIES ASSOCIATED WITH HVAC EPI S... 11! 5.0! SELECTION OF A SUITE OF OPTIMUM EPIS... 11! 5.1! STRATEGY FOR SELECTING APPROPRIATE EPI S FOR HVAC SYSTEMS... 11! 5.2! REASONS FOR NON-COMPLIANCES... 15! 5.3! CONTINUOUS IMPROVEMENT... 15! 6.0! CONCLUSIONS... 16! 2

4 1.0 INTRODUCTION Energy Agreements Prgramme (HVAC WG) The Energy Agreements Prgramme, launched in May 2006, is aimed at the largest energy users interested in taking a strng, strategic and systematic apprach t energy management. Firms agree t implement the new Irish Energy Management Standard, IS 393, and t pursue an aggressive prgramme f energy efficiency actin and investment. In return, SEAI ffers relatinship supprt, advice, netwrking and sme financial supprts. As an initiative within the Energy Agreements Prgramme, SEAI have launched Special Wrking Grups which are frmed by grups f member cmpanies in cnjunctin with SEAI. A prgramme f wrk is determined by the Grup which may cnsists f shared studies, self-assessments, identificatin f energy saving prjects, gruped special investigatins, published guidelines and recmmendatins t the wider grup f Energy Agreements participants. The Special Wrking Grups fcus n a particular area f technlgy r a special interest f energy management system implementatin. The HVAC Wrking Grup Spin III was launched in August This reprt is ne specific utput frm the HVAC SWG Spin III scpe f wrk. 1.1 Backgrund The use f Energy Perfrmance Indicatrs (EPI s) t evaluate energy efficiency is a key requirement f EN and EPI s are widely used t evaluate energy cnsumptin at Macr levels in almst all industrial facilities. EPIs have prven quite easy t implement at macr level where fr example units prduced versus verall energy cnsumptin may be trended ver a specific time. EPI s are als very successfully used fr utility system perfrmance but haven t been used successfully fr HVAC systems. The HVAC SWG Spin II Reprt fr 2009 has shwn that HVAC can be respnsible fr up t 80% f sme facilities energy bill when HVAC utilities are taken int cnsideratin. The imprtance f having metrics t cmpare and challenge energy cnsumptin in HVAC systems is therefre f immense imprtance. The HVAC SWG Spin I reprt states that It was fund during the site audits that nly 35% f the participating cmpanies had verall EPIs t mnitr the energy perfrmance f their HVAC systems. It is therefre f imense imprtance t assist cmpanies in the develpment f EPI s t effectively manage the energy cnsumptin f this energy intensive service. 1.2 Objective f Reprt The bjective f this reprt is t dcument the varius appraches that culd be emplyed t aid in the develpment f EPI s t mnitr the efficiency f HVAC systems. The reprt als aims t suggest a prcedure whereby energy managers can cnclude which EPIs are the best fit fr their applicatin. 1.3 Methdlgy The methdlgy fr generating this reprt was t brainstrm pssibilities with members f the Special Wrking Grup panel f cnsultants and review the existing infrmatin available n EPI s befre cmpiling a reprt n the findings. 3

5 2.0 ENERGY PERFORMANCE INDICATORS (EPIS) 2.1 EPI Definitin An Energy Perfrmance Indicatr (EPI) is a standard r pint f reference against which cmparisns can be made. It is a valuable tl, thrugh the prcess f benchmarking, fr assessing energy perfrmance, allwing the cmparisn f the perfrmance f similar facilities, systems r equipment t be carried ut. 2.2 Prs and Cns f EPIs fr HVAC An EPI fr a HVAC system will facilitate the cmparisn f the perfrmance f the HVAC system against histrical perfrmance f that system r may even allw the benchmarking f the system against similar HVAC systems. The mst significant challenge assciated with develping EPI s fr HVAC systems is the fact that HVAC systems vary cnsiderably in design intent and in the delivery f the energy service requirements frm system t system. Sme HVAC systems may be as simple as unit heaters required t heat a large space r may be as cmplex as a system which cntrls air changes, fresh air, temperature, humidity and rm pressure. In additin, the EPI may vary greatly within a single AHU system depending n ambient r space cnditins. As a result it is rare that AHU systems can be cmpared glbally in a similar fashin t fr example Chilled water system COP. 4

6 3.0 HVAC SYSTEMS ENERGY SERVICE REQUIREMENT & ENERGY FLOWS 3.1 HVAC Energy Service Requirement The energy service requirement is the term given t the cre requirement fr a HVAC system. This can vary depending n the nature f the space being cnditined r the requirements f the prduct being manufactured in the space. Different energy service requirements may include sme r all f the fllwing: Ventilatin The prvisin f fresh air t a space in rder t satisfy a legislative, cmfrt, prcess r building fabric prtectin requirement. Ventilatin & Filtratin The prvisin f partial fresh air in a recirculated system which allws the supply air t be subjected t filtratin. Heating Heat can be added t a space in many ways, radiatrs, direct gas fired unit heaters r mre cmmnly fr industrial applicatins duct/ahu munted heating cils using steam r lw pressure ht water as a heating medium. Cling- Space cling is predminantly achieved with a duct/ahu munted cling cil using chilled water as the cling medium hwever direct Expansin (DX) units are als used. Dehumidificatin- Dehumidificatin is ften a prcessing requirement f sme rms where excessive misture can affect quality. Dehumidificatin can be achieved by cling air t belw its dew-pint in cnventinal cling cils r by passing the air thrugh a desiccant dehumidificatin wheel. Dehumidificatin is an energy intensive step in a HVAC system as the air ften has t be pre-cnditined and pst cnditined after the dehumidificatin step t bring the supply air back t the required temperature cnditins. Humidificatin Humidificatin may be required in rms where a tlerance exists n the humidity in a space. Humidificatin is required in such spaces when cl ambient utdr air is heated thereby reducing the RH f that air. Misture is added in typically by injecting steam r a mist at the utlet f the supply AHU. Humidifiers can be direct steam injectin, indirect steam, gas-fired r electrical. Pressure Prfile The setup f a Pressure prfile is a methd f safeguarding against the infiltratin f unwanted particulate r vapurs int a space which may have a specific cleanliness requirement r a hazardus area classificatin. The safeguarding is accmplished by maintaining the critical space at a higher air pressure t the surrunding spaces thereby guaranteeing the flw f air frm the critical space utwards and reducing the risk f infiltratin. A reverse prfile culd als be setup t ensure prduct cntainment in the cnditined space. 5

7 3.2 Energy Flws in HVAC Systems The flws f energy in a HVAC system vary with the cmplexity f the HVAC energy service. The energy flws int HVAC systems can vary frm electricity int a ventilatin fan t a series f electrical, thermal heating and thermal cling energy flws. The energy flws assciated with the cnditin f the ambient air intrduced int a system and the energy cntent f exhausted air must be cnsidered. Example 1 Simple HVAC system with supply fan, heating and exhaust Fan Supply fan Electricity Exhaust fan Electricity Space Maintained >18 O C Heat Exhausted Heating cil energy Cling Cil Energy HEAT LOSS Fig. 3.1 Energy Flws in a simple Heated and ventilated space Example 1 abve shws the energy inputs int a very simple heating and ventilatin nly HVAC system similar t what may be seen in any typical prductin space which has an air-change and fresh air requirement, a minimum temperature requirement but des nt have an upper limit n temperature. The energy inputs are therefre electricity in t the fans and the heat input fr space heating. There is als an energy surce frm the fresh air which may have a heating r cling effect n the space depending n the ambient cnditins. 6

8 Example 2 Energy Agreements Prgramme (HVAC WG) Humidity Cntrlled, temperature cntrlled, Air Pressure Cntrlled Cleanrm HVAC System. Heat in Frst Cil Elec in Supply Fan Cling in Pre-cler Heat in Regen Heater Elec in Regen Fan Cnditined Space 30% RH +/- 5% 20 C +/- 1 C Pressure ++ Heat Dumped t Atmsphere Cling in Pst-cler Heat in Make-up Air Heat in Pst Humidificatin Heat in re-heat Elec in Exhaust fan HEAT LOSS Fig. 3.2 Cmplex Energy Inputs t Cleanrm HVAC System 7

9 4.0 ENERGY PERFORMANCE INDICATORS SUGGESTED The diagrams shwn in Fig 3.2 and 3.3 abve shw hw the level f cmplexity can differ with HVAC systems which makes it difficult t have EPI s which suit all HVAC applicatins. A sensible set f EPI s fr Example 1 may be t recrd kwh electrical energy per week and kwh heat input per week. Systems like that shwn in Example 2 are hwever much mre cmplex and wuld require multiple energy streams t be evaluated. There are hwever a number f indicatrs which can be applied t specific elements f HVAC systems which can help put mre visibility n verall system perfrmance. 4.1 Specific Fan Cnsumptin Specific Fan Cnsumptin (SFC) is a measure f fan electrical input versus vlume f air delivered t the HVAC space. Specific Fan Cnsumptin fr a fan n a HVAC system can be calculated frm the measured pwer input ver the measured air flw prduced. This can be dne n a cntinuus basis r n a ttalized basis fr daily r weekly intervals. A spt check f Specific fan cnsumptin can be carried ut if fixed instrumentatin des nt exist fr example n annual revalidatin. Tracking Specific Fan Cnsumptin can shw hw filters getting blcked ver time affects pwer cnsumptin and can be used as a tl t decide n the ptimum time t replace filters.sfc can als shw up anmalies fr example if a filter became damaged r detached. 4.2 Ttalised Fan Cnsumptin Ttalised fan cnsumptin is a simple indicatr f the kwh cnsumptin by fans in a HVAC system ver a time perid (generally weekly r mnthly). The additinal benefit f the ttalised figure is f particular imprtance in systems that are nt running 24/7. If HVAC systems are being shut dwn during nnprductin times (r in the case f administratin buildings at nights and weekends), then the specific fan cnsumptin will nt highlight inefficiencies assciated with pr timekeeping f the HVAC systems. This EPI is als useful in systems that may nt have an air-flw meter but has electrical meters n the fans (pssibly in the frm f kwh ttaliser n the supply fan). 4.3 Degree Day Analysis Degree day analysis is a methd f assessing the perfrmance f a building r HVAC system in terms f the heat cnsumptin relative t the ambient temperature. Heating degree days are a measure f the severity and duratin f cld weather. The heating degree day analysis hinges n selecting the base external temperature abve which the building r HVAC system des nt require heating typically 15 C t 18 C depending n insulatin and the rate f internal heat generatin. Degree day data can be btained frm Met Eireann. The sum f the degree days ver perids such as a mnth r an entire heating seasn is used in calculating the amunt f heating required fr a building r HVAC 8

10 system. Degree Days are als used t estimate air cnditining usage during the warm seasn. 4.4 Independent Assessment f Utilities feeding a HVAC System After fan energy cnsumptin, the next energy users which are required t be tracked are the utilities that feed a HVAC system t prvide cnditining f the air which is circulated by the fans. When lking at utilities, evaluatin must take place frm tw appraches. Firstly the cnsumptin f utilities gives the amunt f that utility which was used by the HVAC system (kwh), and secndly the efficiency f the generatin f that utility (COP Biler efficiency etc) will give the relative cst in terms f electricity r thermal fuel surce input Cnsumptin f Utilities by System The ability f a site t track the cnsumptin f utilities will be determined by the level f metering installed n the applicable systems. In many cases thermal utility metering can be mre expensive t install than electrical meters due t the fact that many parameters have t be measured t capture energy r heat flw. Fr example, metering heat input t a HVAC system may require the metering f ht water flw, the temperature f that ht water at supply and the temperature that the ht water returned frm that HVAC system. Ht water may be used in that HVAC system at multiple different pints which may nt be rientated in a manner that wuld allw all pints t be captured with ne metering device. Users may decide t take a mre macr apprach if metering is nt sufficient t allw individual utility metering f a HVAC system - fr example, if there is a dedicated ht water system feeding HVAC systems in general the energy int that Ht water system may be metered. The ttal thermal energy cnsumptin fr the HVAC systems can then be sub-divided acrss the individual systems empirically if required. Examples f utility cnsumptin EPIs that may be used fr HVAC systems are as fllws: Gas/Steam/Ht Water per week/mnth r heating degree day analysis Chilled Fluid Cnsumptin per week/mnth Chiller Energy v Cling Degree Days Biler Cnsumptin versus Heating Degree Days Dehumidifier Electricity/Gas cnsumptin per Week/Mnth Humidifier Electricity/Steam/Gas cnsumptin per Week/Mnth Efficiency r COP f Utility System Tracking energy efficiency f utility systems using EPIs is extremely imprtant whether the utilities are fr HVAC cnsumptin r therwise. In HVAC systems the majrity f energy cnsumptin assciated with utilities is fr heating and cling. Steam, Ht Water and Chilled water systems are generally the utilities which require analysis. Steam System Efficiency 9

11 If steam is the primary heating medium fr a HVAC system, then the efficiency f generatin f steam can be an imprtant EPI. There are varius lsses r inefficiencies assciated with Steam systems including: Cmbustin inefficiencies Standing lsses Blwdwn lsses Steam distributin lss Cndensate lsses Flash steam lsses Very ften the simplest way f getting an verall efficiency reading fr steam is t meter the fuel input t the biler and meter the steam usage (preferably by summing all end users). HVAC heating may be ne r mre f the majr users. A weekly r mnthly reading fr ttalised fuel cnsumptin and ttalised steam cnsumptin can be used t calculate system efficiency. This EPI may highlight in particular lsses during perids f lw steam prductin when bilers may be cycling n and ff. Other items that can shw up wuld be steam traps passing r issues with cndensate return. Fig 4.1 Weekly lgging f Steam System Efficiency as an EPI Ht Water System Efficiency In a similar fashin t steam system efficiency, verall ht water system efficiency can be mnitred by metering fuel input and heat delivered t the users. The heat delivery will need t be calculated frm flw, supply temperature and return temperature, either n the BMS r frm a prprietary heat metering device. Chilled Fluid System Efficiency (COSP) The system cefficient f perfrmance (COSP) fr a chilled water lp gives a figure fr the thermal energy usage ver the energy input int generatin and distributin f the chilled water. It is imprtant t have the pwer cnsumptin f the distributin pumps included if pssible as recent SEI findings frm the 2008 Refrigeratin SWG reprt has shwn that mismatches between cling lads and distributin energy input was ne f the biggest cntributrs t pr COSP s 10

12 in industrial applicatins. In rder t mnitr COSP therefre the fllwing energy readings will be required: Chiller/Refrigeratin system electrical input Chilled Water distributin pumps electrical input Ancillary pwer users electrical input (Cling twer water pumps dedicated t chillers, Cling Twer Fans) Chilled water thermal usage again this can be ne heat metering pint acrss the main supply & return headers r ttalised heat meters acrss users. Chilled water COSP s have been shwn t vary cnsiderably acrss different systems fr similar temperature fluids frm values as lw as 1.5 and up t 8. If COSP cannt be mnitred due t a requirement fr multiple metering pints fr electrical cnsumptin in chilled water pumps then the base COP fr the system shuld be mnitred. COP can be calculated frm thermal usage divided by electrical input t the chiller/refrigeratin system. 4.5 Summary f Cmplexities assciated with HVAC EPI s As can be seen frm the varius suggested indicatrs abve there is a lt f ptential infrmatin but very rarely will ne system f indicatrs prvide the full picture f the energy efficiency f the HVAC system. Measurement f fan cnsumptin n a HVAC system whether its specific fan cnsumptin r a ttalised figure will nt give an indicatin f anything ther than the efficiency f distributing air thrugh the system. Likewise degree day analysis will nly address thermal heating r cling lads n a building/system. Unfrtunately there is n silver bullet slutin fr EPI s that will allw HVAC systems t be cmpared n a single indicatr due t the huge variatin in size and cmplexity f HVAC systems. Fr mst HVAC energy end-users, it will be a case f selecting EPI s that give as much infrmatin as pssible n the efficiency f their HVAC system with the minimum effrt in terms f the engineering/facilities team resurce input. Fr mst facilities this will undubtedly mean the selectin f a few key EPI s which will address the majr energy streams and back-up the EPI s with an peratinal cntrl check f the systems and equipment. The peratinal cntrl check will nt give a number which can be graphed peridically like a numerical EPI but will allw an peratr t make an assessment f the energy perfrmance f the system based n his/her knwledge f the systems and knwledge f where their ptimum perfrmance shuld be. 5.0 SELECTION OF A SUITE OF OPTIMUM EPIS 5.1 Strategy fr Selecting Apprpriate EPI s fr HVAC Systems A practical apprach t selecting EPIs wuld be t firstly evaluate the existing meters and the infrmatin that they prduce. The level f existing infrmatin in many cases is f a sufficient standard t allw meaningful EPI s t be generated. The additin f strategic meters can increase the level f infrmatin available substantially fr a relatively small investment. Fr example, the additin f a heat 11

13 meters n the heating and cling systems feeding the HVAC can be invaluable in determining the perfrmance f HVAC systems. Once the level f existing metering available (r metering available fllwing investment) the EPI s pssible can be selected. Cnsideratin shuld be given at this pint t the time and effrt required t extract the EPI data. Only significant energy users shuld be pursued if the system is t be rbust and user friendly. The last step in achieving a set f meaningful EPI s is t set upper and lwer limits t the EPI. Fr example fr a simple EPI fr kwh fan pwer cnsumptin in a week the fllwing may apply: Fig. 5.1 Trending an EPI n a weekly basis with actin limits. The same wuld apply fr any f the EPI s set whether it is Chilled Water COSP, Ht Water System Efficiency, Specific Fan Cnsumptin etc. When actin limits are in place they can be altered as the systems change. Higher efficiencies can be strived fr fr example t meet best practice fr certain EPI s. 12

14 Fig. 5.2 The flwchart abve shws the prcess fr generating sensible EPI s fr a HVAC system which starts with the review f existing metering. 13

15 Fig. 5.2 Examples f EPI s fr sme cmmn types f HVAC Systems (Ptential EPI s per example shwn shaded) 14

16 5.2 Reasns fr nn-cmpliances There are many reasns fr nn-cmpliances which wuld manifest themselves in the frm f a breach f the upper r lwer limit f the EPI which is nt attributable t an explainable event. The mst cmmn reasns fr nn-cmpliances wuld be Incrrect peratin Equipment Failures Pr Cntrl 5.3 Cntinuus Imprvement Cntinuus imprvement shuld be strived fr with any system and therefre the system must be cntinuusly challenged t ensure it is fit fr purpse. As systems evlve with imprvements the EPI limits can be changed t reflect the imprvements made t the system e.g. if air change reductins are made t a HVAC system, fan kwh cnsumptin will reduce significantly and the limits will need t be changed. Likewise heating, and cling cnsumptin will drp. It is imprtant that EPIs are flexible and that the cntrl limits can be altered withut t much sign ff r apprval. Changing the reprting system shuld be easy enugh t encurage change and t allw peratrs f the HVAC systems t challenge the status qu, increasing perfrmance even if a change t limits is required. 15

17 6.0 CONCLUSIONS It has been shwn that industrial HVAC systems are a very varied and are a cmplex system t mnitr frm an energy usage r energy perfrmance pint f view. This is due t the many different energy cnsumptin steps which can exist and the different factrs which affect energy cnsumptin in a HVAC system. Having a single parameter which indicates energy perfrmance is extremely difficult r impssible fr mst situatins. In rder t get an appreciatin fr the relative efficiency f different HVAC systems in a facility therefre requires multiple EPIs t be used in mst cases. This shuld be backed up with an peratinal cntrl check f the system. The EPIs mst applicable t the specific HVAC system shuld be selected based n the energy cnsumptin infrmatin that can be easily btained frm the system and which gives a gd picture f the system perfrmance fr minimal peratr/engineer time input. 15