CSI Thermal Multifamily/Commercial OG 100 Incentive Calculator User Guide

Transcription

1 CSI Thermal Multifamily/Cmmercial OG 100 Incentive Calculatr User Guide Versin 3.0 Last updated n 06/15/11

2 Table f Cntents 1. Guide Overview TRNSYS Engine Required Calculatr Inputs Getting Started Assumptins Summary f Outputs

3 1. Guide Overview CSI Thermal Multifamily/Cmmercial SRCC OG 100 Incentive Calculatr Guide The Multifamily/Cmmercial OG 100 Incentive Calculatr Guide prvides a detailed explanatin f hw the CSI Thermal incentive is determined. Prgram Administratrs develped the n line calculatr tl, which blends a set f fundamental design assumptins with the belw mentined list f inputs. The calculatr can be accessed at Users may access the public versin which is separate frm the applicatin prcess, r the applicatin versin which is embedded int the applicatin prcess. The sle purpse f the calculatr is t determine a CSI Thermal incentive amunt based n a number f key inputs fr a given prpsed system. Results may nt match thse yu assume r have estimated using different mdels. The calculatr shuld nt be used as a perfrmance guarantee. Actual perfrmance f a slar thermal system may differ frm the results f the CSI Thermal calculatr. If yu have a perfrmance estimating tl that yu like, cntinue t use it. Hwever, the, the CSI Thermal Incentive Calculatr must be used t determine the incentive amunt. The calculatr uses Transient Energy System Simulatin (TRNSYS) sftware t mdel each system and prduce an incentive, based n cnventinal energy displaced by slar energy TRNSYS Engine The TRNSYS Tl is a flexible tl designed t simulate the transient perfrmance f thermal energy systems. The develpment f TRNSYS began in 1975 as a jint prject between the University f Wiscnsin Madisn Slar Energy Lab and the University f Clrad Slar Energy Applicatins Lab. Mre than 35 years later, TRNSYS is a well respected energy simulatin tl under cntinual develpment by a jint team made up f the Slar Energy Labratry (SEL) at the University f Wiscnsin Madisn, The Centre Scientifique et Technique du Batiment (CSTB) in Sphia Antiplis, France, Transslar Energietechnik GmBH in Stuttgart, Germany and Thermal Energy Systems Specialists (TESS) in Madisn, Wiscnsin. The CSI Thermal Prgram Administratrs have cntracted with TESS t develp the CSI Thermal Multifamily/Cmmercial OG 100 Incentive Calculatr, which uses the TRNSYS engine t estimate the 1 Please nte that the final incentive amunts are subject t change based upn the cnfiguratin f the as built system and ther prgram requirements detailed in the CSI Thermal Handbk. 2

4 annual displaced cnventinal gas r electric energy in rder t calculate the incentive amunt fr each prject. 3. Required Calculatr Inputs The cmbined inputs f the calculatr are simulated by TRNSYS t estimate the annual displaced cnventinal gas r electric energy t heat the stated Gallns per Day (GPD). Cnfiguratin Optin : Click n the arrw t access a drp dwn list f pssible cnfiguratins based n the type f heat exchanger, freeze prtectin type, and number f tanks. 1 tank= the slar system and a cnventinal backup heater r biler are heating the same tank 1 tank with a tankless backup= 1 slar strage tank, with a backup tankless r ndemand water heater 2 tanks=slar strage and backup water heater strage are separate tanks. Fr systems with mre than 2 tanks, select a cnfiguratin with 2 tanks (yu will have the pprtunity t further define the number f tanks in a different input field belw) Cllectr : Click n the arrw t access an alphabetical drp dwn list f Slar Rating and Certificatin (SRCC) OG 100 certified cllectrs. Select the manufacturer and mdel. This calculatr btains data frm the SRCC nline directry f OG 100 certified cllectrs n a regular basis. This calculatr is unable t mdel ICS and Thermsiphn systems, since they are nly prvided an OG 300 certificatin and nt an individual OG 100 cllectr certificatin. ICS and Thermsiphn systems fr multifamily and cmmercial prjects are eligible fr a 3

5 CSI Thermal incentive; hwever, a custm simulatin must be run t mdel these prjects. Please cntact the apprpriate Prgram Administratr, based n the utility service territry where the prject site is lcated. Fr newly certified cllectrs that are nt yet n this list, please cntact SRCC t determine when their nline directry will be updated t include the newly certified equipment. Unfrtunately, the applicatin may nt be submitted until the equipment is listed in the SRCC nline directry. Number f Cllectrs : Enter the ttal number f cllectrs, nt the square ftage. Average Cllectr Mdule Area : Enter the average square ftage f individual cllectrs. This field is NOT asking fr grss cllectr area. Number f Cllectrs in Series per Flw Path : Enter the number f cllectrs in series per flw path. In ther wrds, hw many cllectrs r banks f cllectrs are heating the same mlecule f water? Every time a mlecule f water is heated by ne cllectr and then by a secnd cllectr, sme cllectin efficiency is lst because f the warmer temperature fluid entering the secnd cllectr. This input field is NOT asking fr the number f cllectrs in each bank. See belw fr a visual representatin f flw path. Nte belw hw cllectrs cnnected in parallel have tw cnnectins between each cllectr, while thse cnnected in series have nly ne. 4

6 Parallel Reverse Return. Number f cllectrs in flw path is ne. Series. Number f cllectrs in Flw Path is three. 5

7 Parallel Reverse Return Series Cnnectin Parallel Reverse Return The number f cllectrs in the flw path is tw. Parallel Reverse Return Parallel Reverse Return The number f cllectrs in the flw path is ne. 6

8 Series Series Cnnectr Series The number f cllectrs in the flw path is six. B A These cllectrs may have internal parallel piping r internal serpentine piping. Either way, the parallel external maniflds cause each mlecule f water passing frm A t B t flw thrugh nly ne cllectr. The number f cllectrs in the flw path is ne. Ttal Slar Strage Capacity : Enter the ttal gallns f slar strage. Fr 1 tank systems, where bth the slar system and a cnventinal heater r biler are heating the same tank, enter the tank vlume. (E.g. If the ttal capacity f a ne tank system is 300 gallns, enter 300 gallns fr the ttal slar strage capacity). 7

9 Fr 1 tank drain back systems this is the vlume f the drain back reservir plus the strage tank. Fr a 2 tank system, this is the vlume f the slar strage tank nly (d nt include the vlume f the auxiliary strage). Fr a 2 tank drain back system, this is the vlume f the drain back reservir plus slar strage tank. Nte. On large drain back systems, the drain back tank is ften large and serves as the ttal slar strage. Ttal Number f Slar Tanks : Enter the number f slar strage tanks. D nt include the small drain back reservirs in this number. Ttal Backup Heater Capacity : Enter the galln capacity f the backup heater. Fr a tankless heater enter zer. Fr a heater that heats nly the upper part f the tank, enter the capacity f that prtin. Ttal Number f Backup Tanks : Enter the number f backup strage tanks (this is typically 1). Backup Fuel Surce : Click n the arrw t access a drp dwn list f backup water heater ptins. Maximum Auxiliary Heat Capacity : Auxiliary refers t the backup water heater. Lk at the nameplate n the backup water heater fr the gas capacity in BTUH r the electric element capacity in kw, and enter this value. CEC Climate Zne : Click n the arrw t access a drp dwn list f the 16 Califrnia Energy Cmmissin (CEC) Climate Znes. 8

10 T determine the CEC Climate Zne f the prject site, refer t the CEC Climate Zne Manual psted n Enter the zip cde f the prject site in the Find bx at the tp f the PDF, and hit enter. Sme zip cdes are in multiple climate znes. Hit Enter multiple times t find all climate znes fr that zip cde. Applicant may select the apprpriate climate zne in these cases. Ht Water Demand : Ht water demand refers t the gallns per day (GPD) f ht water used. Sectin f the CSI Thermal Handbk prvides sizing guidelines fr multifamily and cmmercial prjects. Since the results are highly sensitive t GPD, the pssibility f verheating 9

11 r ptential gaming t get higher incentives is high. T mitigate these cncerns, a set f input GPD values have been adpted and are defendable based n ASHRAE data. Refer t Appendix D (Maximum GPD Guideline Table) f the CSI Thermal Handbk t determine the apprpriate GPD based n type and size f building. These values are based n 2007 Editin f the ASHRAE Handbk HVAC Applicatins, Sectin 49.14, Table 7. The GPD values in the table are maximum values, and systems may be sized using a lesser GPD assumptin. Building types nt listed in the Maximum GPD Guideline Table must d ne f the fllwing t determine GPD value: Meter Actual Cnsumptin: Meter actual ht water cnsumptin using an inline water flw meter with accumulatr fr a minimum f 60 calendar days and adjust fr seasnal variability. Ht water cnsumptin calculatin must be stamped by a P.E. Meter natural gas r electric cnsumptin at the water heater fr a minimum f 60 days and adjust fr seasnal variability. Water heater gas r electric meter cnsumptin calculatin must be stamped by a P.E. Lad Prfile : Click n the arrw t access a drp dwn list f lad prfile ptins. Select the type f business r institutin that mst clsely matches the ht water lad f the building. Refer t Attachment A: Multifamily/Cmmercial OG 100 Incentive Calculatr Lad Prfiles, fr the cmplete lad prfiles fr each building type. If the building type is nt listed n the drpdwn list, please select Other and fllw directins under Lad Prfile Data File belw. 10

12 Number f Units : Required when the fllwing lad prfiles are selected: Multifamily, Men s Drmitries, Wmen s Drmitries, Htels/Mtels Number f Rms : Required when the fllwing lad prfile is selected: Nursing Hmes Number f Peple : Required when the fllwing lad prfile is selected: Office Building Number f Full meals served : Required when the fllwing lad prfiles are selected: Fd Service (full meals), Fd Service (fast fd) Number f Students : Required when the fllwing lad prfiles are selected: Elementary Schls (Year rund peratin), Elementary Schls (10 mnth peratin), Junir High Schls (Year rund peratin), Junir High Schls (10 mnth peratin), Senir High Schls (Year rund peratin), Senir High Schls (10 mnth peratin) Number f 10 lbs per washing machine : Required when the fllwing lad prfile is selected: Laundrmats. The 10 lbs refers t the capacity f the cmmercial washing machine. Fr a washing machine with a 20 lbs capacity, duble the value in Appendix D f the handbk when entering the ht water demand GPD (previus input). Other Lad Prfile : When a building type is nt listed in the Maximum GDP Guideline Table in Appendix D, Applicants must meter actual ht water cnsumptin, natural gas r electric cnsumptin used fr water heating as described in Sectin f the CSI Thermal Handbk. A Prfessinal Engineer (P.E.) must use the metered data alng with additinal analysis and calculatins t cme up with a custm lad prfile t gather hurly ht water draw fr ne year. The lad prfile must shw hurly ht water galln demand fr a typical year (8760 hurs) and the status f the recirculatin lp fr each hur as utlined in the fllwing example: Table H1 Lad Prfile Data Example Hur Elementary Schls (10 mnth) Ht Water Draw Gallns/Hur 11 Recirculatin Lp Pump Status 1=On: 0=Off

13 The lad prfile data must be upladed t the calculatr in a tab delimited frmat dcument using the template prvided in Table H1. A GDP value must als be entered fr system sizing verificatin. T uplad a lad prfile, g t Lad Prfile Descriptin field and click n the Brwse buttn, select the file and click Open. A custm lad prfile will be calculated using the upladed data. Recirculatin Lp. If the building has an peratinal recirculatin lp, check the bx: If a recirculatin lp is nt present, leave the bx unchecked: Set Pint Temperature f Backup Heater : Enter the set pint value in F (usually arund 140 F). Set Pint Temperature fr Delivered Water : This is the mixing valve set pint temperature. Enter this value in F. Array Tilt : Enter the degree tilt frm hrizntal f the cllectr array. Array Azimuth : Enter the True Azimuth. True Suth is 180 degrees. T find True Azimuth in Califrnia add the magnetic variatin t the magnetic cmpass reading f the cllectr array (13 degrees in Suthern Califrnia, 15 degrees in Nrthern Califrnia). 12

14 Average Annual Access : Enter the integer percent fr the average annual slar access t the cllectr array between the hurs f 10am and 3pm. Use a shade analysis device t determine this value. The minimum allwable average annual availability f the slar cllectr(s) between the hurs f 10:00 am and 3:00 pm is 85 percent (15 percent average annual shade between 10:00 am and 3:00 pm). Prject Name : Enter the prject name and reservatin ID (if available). This is used fr yur reference and will be included n the results . This input field nly applies t the public versin f the calculatr. Address : Enter yur address. The calculatr will yu results. This prcess typically takes abut 15 minutes t cmplete, but may take lnger if the system is prcessing many requests. Yu will receive an when yur results are ready. This input field nly applies t the public versin f the calculatr. 4. Getting Started As yu start using the calculatr, there are a few things t keep in mind: Please allw at least 20 minutes fr yur results t be returned; results may take lnger, even up t a few hurs. Input fields are nt negtiable. This is a final versin f the calculatr. Please cntact yur lcal Prgram Administratr fr prgram questins. Cntact infrmatin is listed at If yu experience technical difficulties please cntact supprt at supprt@csithermal.cm r Assumptins Cllectr Fluid: 40% prpylene glycl fr all systems requiring an anti freeze slutin water fr drainback systems water fr direct frced circulatin systems Fluid prperties are cnstant during the simulatin and were based n a 40 C (104 F) average fluid temperature. 13

15 Weather: Califrnia climate zne data in Energy+ frmat will be used t drive the annual simulatins. The wind speed required by the TRNSYS external pipe mdels and un glazed slar cllectr mdels will be reduced t 30% f the value frm the data file t accunt fr lcal bstructins and near surface effects. Slar shading f the cllectr surface is nt accunted fr in the TRNSYS simulatins (but it easily culd be) but rather used t prvide a linear multiplier n the calculated rebate (calculated in the web tl). The weather data is prvided n an hurly basis and the TRNSYS prgram interplates the data fr us in its sub hurly calculatins (currently set t 1 minute timesteps). Envirnment Temperature: The envirnment temperature fr heat lss calculatins fr the strage tanks and tank/hx piping is assumed be that f semi cnditined space. The temperature f semi cnditined space is defined t be 1/3 f the temperature difference frm the ambient temperature t 72 F: T envirnment = T ambient + (72 F T ambient )/3 Flat Plate and Evacuated Tube Slar Cllectrs: Parameters prvided by the user selectin f an OG100 slar thermal cllectr frm the web site: Grss cllectr area cllectr intercept efficiency, cllectr 1st rder lss cefficient and 2nd rder lss cefficients as tested flw rate as tested fluid descriptin (water etc.) 1st rder and 2nd rder incidence angle mdifiers cefficients fr flat plate cllectrs 1st rder and 2nd rder transverse incidence angle mdifiers cefficients and 1st rder and 2nd rder lngitudinal incidence angle mdifiers cefficients fr evacuated tube slar cllectrs. Parameters prvided by the user frm the web site: # f cllectr mdules Slpe f cllectr surface (0=hrizntal, 90=vertical) Azimuth f cllectr surface (180=suth,270=west, 0=nrth, 90=east) # f panels in series per parallel flw path Thermal capacitance f the slar cllectrs is set t 10 kj/m2.k 14

16 50 thermal ndes (isthermal temperature sectin) per mdule alng the flw path Cllectr Piping: All pipes in the mdel are assumed t be standard size Type L cpper pipes sized t maintain 4 /secnd r less fluid velcity at peak flw cnditins; up t a 2 nminal size. The inner and uter diameters fr these cmmnly used cpper pipes are listed belw. Nminal Size Outer diameter Inner diameter 3/ / / / ¼ ½ Beynd 2 inches, the inner diameter f the pipes are ideally sized t maintain the 4 /secnd criteria and the uter diameter is calculated based upn the rati f the uter diameter t the inner diameter fr the nminal 2 Type L cpper pipe. The ttal length f the cllectr lp piping (frm the cllectr t the heat exchanger and back fr indirect systems and frm the cllectr t the tank and back fr direct systems) is calculated as: Ttal Length = * Number f Cllectr Mdules This length is divided equally amngst the cllectr supply and return lines. All cllectr lp pipes are assumed t be insulated with ¾ pipe insulatin with a thermal cnductivity f 0.04 W/m.K (similar prperties t an Aergel like material). Internal and external fluid cnvectin resistances are accunted fr in the mdel. Pipes have a temperature distributin alng the flw directin (10 ndes per pipe) with the amunt f stratificatin set frm an earlier analysis that lked at simulatin speed versus accuracy. Cllectr pipes are assumed t be lcated utdrs and are expsed t the ambient temperature and reduced ambient wind speed fr cnvective lsses with lng wave radiatin lsses (emissivity=0.9) calculated based upn the sky temperature. 15

17 Cllectr Pump: Cllectr side flw rate is set at 1 galln per minute thrugh each cllectr. The ttal cllectr lp flw rate is then: Gallns per Minute = # Cllectr Mdules / # Cllectrs in Series per Parallel Lp Pump pwer assumed t be a linear functin f flw rate and set at 15 Watts/gpm. The pump is assumed t have a mtr efficiency f 90% and an verall efficiency f 60%. External Heat Exchanger (External HX Systems Only): The external heat exchanger will be mdeled as a cnstant effectiveness heat exchanger with an effectiveness f 0.4 fr all duble wall cases (separatin f glycl and water). The external heat exchanger will be mdeled as a cnstant effectiveness heat exchanger with an effectiveness f 0.5 fr all single wall cases (separatin f water and water). The heat exchanger has n thermal lsses. The effectiveness f the heat exchanger des nt change with time (n fuling). Tank/HX Pump (External HX Systems Only): Tank side vlumetric flw rate is set equal t the cllectr side vlumetric flw rate. Pump pwer assumed t be a linear functin f flw rate and set at 15 Watts/gpm. The pump is assumed t have a mtr efficiency f 90% and an verall efficiency f 60%. Tank/HX Piping (External HX Systems Only): All pipes in the mdel are assumed t be standard size Type L cpper pipes sized t maintain 4 /secnd r less fluid velcity at peak flw cnditins; up t a 2 nminal size. The inner and uter diameters fr these cmmnly used cpper pipes are listed belw. 16

18 Nminal Size Outer diameter Inner diameter 3/ / / / ¼ ½ Beynd 2 inches, the inner diameter f the pipes are ideally sized t maintain the 4 /secnd criteria and the uter diameter is calculated based upn the rati f the uter diameter t the inner diameter fr the nminal 2 Type L cpper pipe. The ttal length f the tank lp piping (frm the tank t the heat exchanger and back) is set t 40 with the length divided equally amngst the supply and return lines. All tank lp pipes are assumed t be insulated with ¾ pipe insulatin with a thermal cnductivity f 0.04 W/m.K (similar prperties t an Aergel like material). Internal and external fluid cnvectin resistances are accunted fr in the mdel. Pipes have a temperature distributin alng the flw directin (10 ndes per pipe) with the amunt f stratificatin set frm an earlier analysis that lked at simulatin speed versus accuracy. Tank lp pipes are assumed t be lcated within semi cnditined space and are expsed t a prescribed envirnment temperature fr calculatin f bth the cnvective and lng wave radiatin lsses (emissivity=0.9). The pipes are assumed t be in stagnant air (n air velcity) with a hrizntal rientatin fr natural cnvectin heat transfer calculatins. Slar Cntrller: The cntrller used t turn n and ff the cllectr side pumps is assumed t be a differential cntrller with a 20 F turn n deadband and a 5 F turn ff deadband. The cntrller is sensing the cllectr fluid utlet temperature and a strage tank fluid temperature lcated near the bttm 1/3 f the strage tank (nde 8 f 10 in the slar tank). The cntrller des nt allw shrt cycling f the pumps, enfrcing a 5 minute minimum run time and 5 minute minimum ff time cnditin. The cntrller will als check the temperature f the strage tank; ceasing pump peratin if the strage tank reaches 170 F. The pump will nly then be enabled when the strage tank temperature falls belw 160 F. 17

19 The cntrller als watches the cllectr fluid temperature and will turn n the pumps if the cllectr temperature reaches 300 F; prvided the tp f the slar strage tank has nt reached the 175 safety limit. The pumps will shut ff when the cllectr temperature falls belw 280 F r if the tp f the strage tank reaches 170 F. Fr direct frced circulatin systems, the cntrller will initiate pump peratin when the temperature f the fluid in the cllectr falls t 35 F and will cntinue t run the pumps until the temperature at the cllectr utlet reaches 45 F. Drainback Tank (If Present): The vlume f the drainback tank is set frm a linear functin f the number f cllectr mdules and is set by: Gallns = *Mdules The heat lss cefficient fr the drainback tank is set t 3 kj/h.m2.k The drainback tank is assumed t be rectangular in shape with the height being 2/3 the length f the sides. The drainback tank is assumed t be fully mixed at all times. The drainback tank is assumed t be lcated within semi cnditined space. Slar Strage Tank: Parameters prvided by the user frm the web site fr the strage tank: Ttal nminal vlume f primary strage (gallns) Number f identical primary slar strage tanks Type f auxiliary heat input (electric, gas, r gas tankless) Nameplate auxiliary heating input rate fr 1 tank systems The primary (slar) strage tank fr this prject, fr systems with immersed heat exchangers, is based lsely n the ppular 120 galln versin f the Bradfrd White PwerStr strage tank (immersed heat exchanger). Detailed mdel calibratins have been dne in TRNSYS in rder t set the immersed heat exchanger free cnvectin parameters fr this strage tank such that the results frm the mdel clsely match the published I=B=R ratings fr the tank. The fluid vlume is 90% f the user prvided nminal strage vlume The slar strage tank will be mdeled as a single strage tank with parameters chsen t mimic a user specified number f strage tanks cnnected in parallel. The tanks are assumed t be lcated within semi cnditined space. 18

20 Stratificatin is mdeled in the strage tank thrugh the use f 10 unifrm temperature layers (ndes) in the strage tank. The verall heat lss cefficient f each slar strage tank is calculated using an algrithm prvided by ASHRAE Standard , Addendum k, Table 7.8. Fr slar strage tanks with electric backup and having less than r equal t 12 kw f rated heating capacity, the energy factr fr the tank is calculated as *Gallns. Frm the calculated energy factr, the heat lss cefficient f the strage tank can be derived. Fr slar strage tanks with electric backup and having greater than 12 kw f rated heating capacity, the heat lss in BTU/h frm the strage tank at a watert air temperature difference f 70 F is calculated as 20+35* Gallns. Frm the calculated heat lss, the heat lss cefficient f the strage tank can be determined. Fr slar strage tanks with gas back up, the assumptin is made that the heating system is external t the strage tank (gas biler with an immersed heat exchanger etc.). The strage tank can then be described as an un fired strage tank with a crrespnding level f insulatin f R12.5. The lsses fr the mdeled tank are dubled frm the theretical R12.5 insulatin t accunt fr thermal shrts and ther tank heat lss as dne in the SRCC OG300 standard. Fr slar strage tanks in preheat systems (n auxiliary heat input), the assumptin is made that the tank is an un fired strage tank with a crrespnding level f insulatin f R12.5. The lsses fr the mdeled tank are dubled frm the theretical R12.5 insulatin t accunt fr thermal shrts and ther tank heat lss as dne in the SRCC OG300 standard. The ttal heat lss cefficient fr all f the slar strage tanks is then calculated and a single strage tank, with the same height t diameter rati, a vlume equal t the vlume f all the individual strage tanks, and an effective heat lss cefficient that prvided the same ttal heat lss cefficient as the sum f the individual tanks, is then mdeled. The rati f the height f the slar strage tank t the diameter f the slar strage tank is assumed t be that f the 120 galln strage tank; 2.608:1 In all systems where water is heated by the cllectr lp and returned t the strage tank, the heated water is assumed t enter at the very tp f the strage tank (nde 1) unless the primary strage tank cntains an auxiliary heating system (electric r gas but nt gas tankless). In the case where the slar strage cntains an auxiliary heating system, the heated water enters the tank just belw the heated sectin f the strage tank (nde 4). The return water t the cllectr lp is assumed t ccur frm the bttm f the slar strage tank (nde 10). 19

21 The mains water enters at the very bttm f the strage tank (nde 10) and exits at the very tp f the strage tank (nde 1). Cld water inlets thrugh a diptube are nt cnsidered in this analysis. If the system cnfiguratin in questin has an immersed heat exchanger then the fllwing assumptins apply: Immersed heat exchangers separating glycl frm ptable water are assumed t be duble wall heat exchangers while immersed heat exchangers separating water frm ptable water are assumed t be single wall heat exchangers. The inner diameter f the ciled tube heat exchanger piping is set t meters and the utside diameter f the ciled tube heat exchanger is set t meters. These values are based n published data fr the Pwerstr series strage tanks. The length f each heat exchanger ciled tube is meters (this value is based n published data fr the Pwerstr series strage tanks) The thermal cnductivity f the heat exchanger material is assumed t be 50 kj/h.m.k fr duble wall immersed heat exchangers and 150 kj/h.m.k fr single wall immersed heat exchangers. These values were used in the calibratin f the tank mdel t published data fr the Pwerstr series tanks which allwed us t set the natural cnvectin cefficients t best match the published perfrmance data (different fr single and duble wall cases). The diameter f the ciled tube heat exchanger was set t meters with a tubet tube spacing f meters. The number f identical ciled tube heat exchangers in the strage tank is calculated based n the rati f the ttal user specified slar strage tank vlume t the vlume f the 120 galln base tank (with a nn integer number f heat exchangers pssible). The ciled tube heat exchanger is lcated near the bttm f the strage tank with the uppermst sectins in nde 6 (heated fluid entrance) and the lwermst sectins in nde 9 (heated fluid exit). When the heat exchanger is charging the slar strage tank, a cnvective mixing lp is assumed t ccur with heated fluid rising frm the heat exchanger t the tp f the strage tank (r just belw the auxiliary heated sectin f the tank), turning, and returning t the bttm f the strage tank. The mass flw rate f this cnvective lp is strictly a functin f the vlume f the fluid that is unheated by the auxiliary heater; 150 kg/h fr tanks withut auxiliary heat and 100 kg/h fr tanks with the upper sectin heated by auxiliary. These values were btained by matching TRNSYS simulatin mdels t measured SDHW perfrmance fr tanks similar in cnstructin t the Pwerstr series f tanks. These cnvective mixing flw rates are then multiplied by the rati f the ttal slar strage vlume t 120 gallns. If the system cnfiguratin in questin has an auxiliary heating system in the primary strage tank then the fllwing assumptins apply: 20

22 The upper 30% f the primary strage tank is assumed t be heated by auxiliary. The efficiency f the heating device is set by the type f device; 0.98 fr electric systems and 0.82 fr gas systems. The capacity f the auxiliary heating device is prvided by the user in the web tl. The capacity f the auxiliary heating device fr the base system (cmparisn system) is calculated by dubling the rate f energy required t raise the maximum hurly ht water draw frm the mains water temperature t the user specified ht water auxiliary setpint temperature. The setpint f the auxiliary heated sectin f the tank is prvided by the user with an assumed 5 degree Fahrenheit deadband temperature difference fr the cntrller. The thermal lsses frm the auxiliary heater t the envirnment, and frm any expsed pipes in the auxiliary heating system, are ignred. The small parasitic pump pwer (if any) assciated with the auxiliary heating system is ignred. Auxiliary Strage Tank (If Present): Parameters prvided by the user frm the web site fr the auxiliary strage tank: Nminal vlume f auxiliary strage tank (gallns) Number f identical auxiliary strage tanks Type f auxiliary heat input (electric, gas, r gas tankless) Nameplate auxiliary heating input rate fr back up system The auxiliary strage tank fr this prject is als based lsely n the 120 galln versin f the Bradfrd White PwerStr strage tank. The fluid vlume is 90% f the user prvided nminal strage vlume The auxiliary strage tank will be mdeled as a single strage tank with parameters chsen t mimic a user specified number f auxiliary strage tanks cnnected in parallel. The tank is assumed t be lcated within semi cnditined space. Stratificatin is mdeled in the strage tank thrugh the use f 10 unifrm temperature layers (ndes) in the strage tank. The verall heat lss cefficient f each strage tank is calculated using an algrithm prvided by ASHRAE Standard , Addendum k, Table 7.8. Fr strage tanks with electric backup and having less than r equal t 12 kw f rated heating capacity, the energy factr fr the tank is calculated as *Gallns. Frm the calculated energy factr, the heat lss cefficient f the strage tank can be derived. 21

23 Fr strage tanks with electric backup and having greater than 12 kw f rated heating capacity, the heat lss in BTU/h frm the strage tank at a water t air temperature difference f 70 F is calculated as 20+35* Gallns Fr strage tanks with gas back up, the assumptin is made that the heating system is external t the strage tank (gas biler with an immersed heat exchanger etc.). The strage tank can then be described as an un fired strage tank with a crrespnding level f insulatin f R12.5. The lsses fr the mdeled tank are dubled frm the theretical R12.5 insulatin t accunt fr thermal shrts and ther tank heat lss as dne in the SRCC OG300 standard. The ttal heat lss cefficient fr all f the auxiliary strage tanks is then calculated and a single strage tank, with the same height t diameter rati, a vlume equal t the vlume f all the individual strage tanks, and an effective heat lss cefficient that prvided the same ttal heat lss cefficient as the sum f the individual tanks, is then mdeled. The rati f the height f the auxiliary strage tank t the diameter f the auxiliary strage tank is assumed t be that f the 120 galln strage tank; 2.608:1 The heated water frm the strage tank enters at the very bttm f the strage tank (nde 10) and exits at the very tp f the strage tank (nde 1). A diptube is nt cnsidered in this analysis. The return water frm the recirculatin lp (if enabled) enters at the very bttm f the strage tank (nde 10) and exits at the very tp f the strage tank (nde 1). If the auxiliary strage tank has an electric heating system then the tank is heated by tw immersed electrical heating elements. The uppermst heating element, and its assciated thermstat, is situated such that the upper 30% f the auxiliary strage tank is heated (nde 3). The lwer heating element, and its assciated thermstat, is situated such that the upper 70% f the auxiliary strage tank can be heated by this heating element (nde 7). The upper heating element is cntrlled t maintain the temperature at the user specified set pint temperature with a temperature deadband f 15 F. The lwer heating element is cntrlled t maintain the temperature at the user specified set pint temperature with a temperature deadband f 5 F. The heating elements are cntrlled in a master/slave arrangement where the lwer heating element is nly enabled if the upper heating thermstat is satisfied. The efficiency f the electric heating devices is The capacity f each auxiliary heating device is calculated by halving the user specified auxiliary heating rate. The capacity f each auxiliary heating device in the base system is calculated by dubling the rate f energy required t raise the maximum hurly ht water draw frm the mains water temperature t the userspecified ht water auxiliary setpint temperature. If the auxiliary strage tank has a gas heating system then the entire tank is heated frm the bttm (nde 10) by a gas heat surce with an efficiency f The thermstat fr the heating system is lcated near the bttm f the tank (nde 9) and is cntrlled 22

24 t maintain the user specified temperature setpint with a temperature deadband f 5 F. The capacity f the auxiliary heating device is then simply the user specified auxiliary heating rate. The capacity f the auxiliary heating device in the base system is calculated by dubling the rate f energy required t raise the maximum hurly ht water draw frm the mains water temperature t the user specified ht water auxiliary setpint temperature. Tankless Gas Water Heater (If Present): The tankless water heater in the slar system has a user defined capacity and the tankless water heater in the base system has an unlimited capacity t meet the ht water demand. The capacity is perfectly adjustable such that device exactly meets the temperature demand. The efficiency f the tankless water heater is 0.82 fr gas tankless systems and 0.98 fr electric tankless systems. N thermal lsses r parasitic energy cnsumptin is mdeled. The setpint temperature fr the tankless system is set t the desired water delivery temperature (a user specified value). Tempering Cntrl: The system is assumed t have tw separate tempering valves which restrict the delivery temperature f the heated water by bypassing part f the mains water stream arund the strage tank and mixing it back in with the heated water cming frm the tank. The first tempering valve (nly fr a tw tank system) limits the temperature f the water leaving the slar strage tank n the lad side t 160 F (limit n temperature entering the auxiliary strage tank). The secnd tempering valve limits the temperature f the water being delivered t the lad t the userspecified ht water delivery temperature. DHW Lads: Parameters prvided by the user frm the web site: Daily ht water cnsumptin (gallns) DHW Prfile The table at the end f this dcument lists the hurly fractin f daily ht water cnsumptin fr each f the draw prfiles available t the user. 23

25 The minimum flw rate at any time is assumed t be at 0.5 gallns per minute. Fr example if at 2 am the draw schedule and draw vlume dictate that the ttal amunt f ht water drawn ver the hur is 2 gallns, then the system will deliver 0.5 gpm f heated water fr 4 minutes at the beginning f the hur and sit idle fr the remainder f the hur (as ppsed t drawing 2 gallns per hur fr the entire hur). This is dne t avid the unrealistic cntinuus trickle f ht water ver an hur which can ccur during lw draw perids. The main water temperature is based upn an algrithm develped by NREL based n measured data and is a functin f the time f year and the mnthly average ambient air temperatures fr the lcatin. This mains water temperature prfile is n average abut 6 degrees Fahrenheit warmer than the algrithm used in the OG 300 rating prgram (F Chart methd). This will significantly alter the results when cmpared with standard OG 300 systems. Ht Water Delivery Pipes: All ht water pipes in the mdel are assumed t be standard size Type L cpper pipes sized t maintain 4 /secnd r less fluid velcity at peak flw cnditins; up t a 2 nminal size. The inner and uter diameters fr these cmmnly used cpper pipes are listed belw. Nminal Size Outer diameter Inner diameter 3/ / / / ¼ ½ Beynd 2 inches, the inner diameter f the pipes are ideally sized t maintain the 4 /secnd criteria and the uter diameter is calculated based upn the rati f the uter diameter t the inner diameter fr the nminal 2 Type L cpper pipe. The DHW lad is assumed t be remved at tw pints in the system; ne half f the lad is remved at the half way pint dwn the pipe run and the remaining lad is remved at the end f the pipe run. 24

26 The length f the ht water pipe frm the strage/heating system t the first lad pint is calculated as: Pipe Length = * Gallns f Ht Water Usage per Day The length f the ht water pipe frm the first lad pint t the secnd lad pint is calculated as: Pipe Length = * Gallns f Ht Water Usage per Day All DHW pipes are assumed t be insulated with ¾ pipe insulatin with a thermal cnductivity f 0.04 W/m.K (similar prperties t an Aergel like material). Internal and external fluid cnvectin resistances are accunted fr in the mdel. Pipes have a temperature distributin alng the flw directin (10 ndes per pipe) with the amunt f stratificatin set frm an earlier analysis that lked at simulatin speed versus accuracy. All DHW pipes are assumed t be lcated within semi cnditined space and are expsed t a prescribed envirnment temperature fr calculatin f bth the cnvective and lng wave radiatin lsses (emissivity=0.9). The pipes are assumed t be in stagnant air (n air velcity) with a hrizntal rientatin fr natural cnvectin heat transfer calculatins. Recirculatin Pump (If Present): The cnstant speed recirculatin pump pwer will perate 24 hurs a day, 7 days a week with a mtr efficiency f 90% and an verall pump efficiency f 60%. The flw rate fr the circulatin lp pump was set frm a linear relatinship assumed between a typical value fr a small system and a typical value fr a large system. The flw rate is calculated as: Pump Flw (gpm) = Gallns f Ht Water Usage per Day / 1000 The pwer fr the circulatin lp pump was set frm a linear relatinship assumed between a typical value fr a small system and a typical value fr a large system. The pump pwer draw is calculated as: Pump Pwer (hp) = 1/25 + Gallns f Ht Water Usage per Day / 50,000 Recirculatin Lp (If Present): The length f the recirculatin lp pipe frm the end f the supply line back t the heating device is equal t the length f the pipe run frm the heating device t the secnd (and final) lad draw pint: Pipe Length = * Gallns f Ht Water Usage per Day The diameter f the recirculatin lp piping is assumed t be the same as the ht water supply pipes. All recirculatin lp pipes are assumed t be insulated with ¾ pipe insulatin with a thermal cnductivity f 0.04 W/m.K (similar prperties t an Aergel like material). 25

27 Internal and external fluid cnvectin resistances are accunted fr in the mdel. Pipes have a temperature distributin alng the flw directin (10 ndes per pipe) with the amunt f stratificatin set frm an earlier analysis that lked at simulatin speed versus accuracy. All recirculatin lp pipes are assumed t be lcated within semi cnditined space and are expsed t a prescribed envirnment temperature fr calculatin f bth the cnvective and lng wave radiatin lsses (emissivity=0.9). The pipes are assumed t be in stagnant air (n air velcity) with a hrizntal rientatin fr natural cnvectin heat transfer calculatins. Fr single tank systems, the recirculatin fluid enters the primary strage tank at the height f the auxiliary heat inlet t the tank (nde 3) and exits at the tp f the strage tank such that the remainder f the tank is nt heated by the auxiliary energy surce and this energy is nt sent ut int the cllectr lp. Fr tw tank systems, the recirculated fluid enters the bttm f the auxiliary strage tank (nde 10) and exits at the tp f the strage tank. Fr gas tankless water heater systems, the recirculated fluid is returned t the inlet f the tankless water heater and mixed with heated water frm the primary strage tank. Base DHW System: The base water heating system is driven by the same water draw prfile and mains water temperature as the SDHW system. When cmpared against single tank SDHW systems with integral auxiliary heat, the base DHW strage tank will have the same vlume, height, and heat lss cefficients as the primary slar strage tank. When cmpared against tw tank SDHW systems, the base DHW strage tank will have the same vlume, height, and heat lss cefficients as the auxiliary slar strage tank. When cmpared against tankless SDHW systems, there will be NO base DHW strage tank. The base DHW tank, r tankless water heater, is assumed t be lcated within semicnditined space. Stratificatin is mdeled in the base DHW strage tank thrugh the use f 10 unifrmtemperature layers (ndes) in the strage tank. The mains water enters at the very bttm f the strage tank (nde 10) and exits at the very tp f the strage tank (nde 1). A diptube is nt cnsidered in this analysis. Fr tankless systems, the mains water mixes with any recirculated water befre entering the tankless water heater. Fr DHW systems with a strage tank, the return water frm the recirculatin lp (if enabled) enters at the very bttm f the strage tank and exits at the very tp f the strage tank. 26

28 In electric systems, the base electric tank is heated by tw immersed electrical heating elements. The uppermst heating element, and its assciated thermstat, is situated such that the upper 30% f the auxiliary strage tank is heated (nde 3). The lwer heating element, and its assciated thermstat, is situated such that the upper 70% f the auxiliary strage tank can be heated by this heating element (nde 7). The upper heating element is cntrlled t maintain the temperature at the user specified auxiliary set pint temperature with a temperature deadband f 15 F. The lwer heating element is cntrlled t maintain the temperature at the user specified auxiliary set pint temperature with a temperature deadband f 5 F. The heating elements are cntrlled in a master/slave arrangement where the lwer heating element is nly enabled if the upper heating thermstat is satisfied. The efficiency f the electric heating devices is The capacity f each auxiliary heating device is calculated by dubling the rate f energy required t raise the maximum hurly ht water draw frm the mains water temperature t the user specified ht water auxiliary setpint temperature. In gas systems, the entire DHW tank is heated frm the bttm (nde 10) by a gas heat surce with an efficiency f The thermstat fr the heating system is lcated near the bttm f the tank (nde 9) and is cntrlled t maintain the user specified auxiliary temperature setpint with a temperature deadband f 5 F. The capacity f the auxiliary heating device is calculated by dubling the rate f energy required t raise the maximum hurly ht water draw frm the mains water temperature t the userspecified ht water auxiliary setpint temperature. All assumptins surrunding the tankless water heater fr the SDHW system will apply here as well (thermal lsses, efficiency, capacity, heat lss etc.) The base DHW system utilizes a tempering valve t limit the temperature f the water delivered t the lad (user specified delivery temperature). The base DHW system utilizes exactly the same DHW pipes and recirculatin system as the SDHW system. Calculatin f Savings: The TRNSYS mdel calculates the energy savings f the SDHW system as cmpared t the DHW system in the fllwing manner: Auxiliary Energy Savings = Annual Auxiliary Energy Used by the Base DHW System Annual Auxiliary Energy Used by the SDHW System Parasitic Energy Savings = Annual Parasitic Energy Used by the Base DHW System Annual Parasitic Energy Used by the SDHW System Delivered Energy Savings = (Annual Energy Delivered t the Lad by the SDHW System Annual Energy Delivered t the Lad by the DHW System) / Efficiency f Auxiliary Heater Ttal Annual SDHW Savings = Auxiliary Energy Savings + Parasitic Energy Savings + Delivered Energy Savings 27

29 Lad Prfiles: All usage prfiles except Laundry cme frm ASHRAE HVAC Applicatins 2007 sectin 49.18, figure 24. The Laundry usage prfile cmes frm a Federal Technlgy Alert n Cmmercial Heat Pump Water Heaters fund at: Refer t Attachment A: Multifamily/Cmmercial OG 100 Incentive Calculatr Lad Prfiles fr the lad prfiles fr each building type. 6. Summary f Outputs Once the OG 100 incentive calculatin is cmplete, the fllwing utputs will be prvided t the requestr: Estimated annual displaced energy: therms fr systems with natural gas backup water heaters; kwh fr systems with electric backup water heaters. Estimated incentive amunt: based n the estimated annual displaced energy, using the current incentive step level rate. 28