MECHANICAL SYSTEM DESIGN

Transcription

1 Julia Thrpe Landscape Building at Janelia Farm Mechanical Optin Final Reprt MECHANICAL SYSTEM DESIGN PROPOSED GOALS, SCOPE & JUSTIFICATION The Landscape Building will have an estimated yearly utility bill f $3,530,000 nce it is cmpleted. This is a direct result f the size f the building as well as the building type. Labratry spaces have requirements that will directly increase the cst f peratin. Prviding 100 percent utdr air t all labratry spaces will increase fan energy and equipment energy because such a large amunt f air must be cnditined and mved thrughut the building. Air cannt be recirculated and therefre all f the air in the labs must be exhausted ut f the building. Exhaust air cntains a large amunt f energy that escapes unused int the atmsphere. As stated in a case study f R.W. Jhnsn Pharmaceutical Research Institute, Fume hds are directly respnsible fr a large amunt f fan energy, and they are indirectly respnsible fr vast amunts f heating and cling energy because f the vlume f cnditined air they cntinually exhaust frm the labs. The primary gal is t mdify the existing HVAC system t reduce energy cnsumptin and yearly utility csts. As energy cnsumptin is reduced, lcal and utility emissins will decrease as well. Secndary gals include ptimizing the artificial lighting in the labratry spaces lcated n the secnd and third flrs as well as resizing affected cmpnents f the electrical system. The system mdificatins must be dne withut unfavrably changing the current system. As fund with Technical Assignments One and Tw, the Landscape Building meets ventilatin requirements utlined in ASHRAE Standard 62 and lighting pwer allwance and building envelpe cmpliance as utlined in ASHRAE Standard All changes shall maintain the highest standards f the riginal design. The scpe f the design prcess includes the fllwing: Mdeling the existing labratry and supprt spaces. Mdeling the labratry and supprt spaces based n deign requirements. Mdeling the labratry and supprt spaces based n required air changes per hur. Determine smallest pssible system that meets lad and indr air quality requirements. Designing and incrprating a grund-cupled water system. The labratry spaces are the prime fcus f this design. They make up apprximately ne third f the building area with mechanical rms at apprximately 50%, and vivarium, ffices, and public spaces making up the remainder. It can be said that the labratry spaces are the dminant lad and energy cnsumer in the Landscape Building due t its 100 percent utdr air requirement. All cmparisns in the design prcess are in reference t the existing labratry design nly. All ther areas and spaces have been excluded. The results f this thesis prvide suggestins fr alternative slutins t the design f the Landscape Building at Janelia Farm. All mdificatins are fr academic purpses and d nt imply flaws in the riginal design (ld e-studi disclaimer). All mdificatins are simply alternative slutins which will include ne extensive mdificatin t the mechanical system and resulting changes t the ther building systems. 17

2 Julia Thrpe Landscape Building at Janelia Farm Mechanical Optin Final Reprt CONSIDERED ALTERNATIVES COGENERATION Cgeneratin systems capture thermal energy that wuld therwise be lst t the envirnment. These systems becme increasingly ecnmically feasible as utility rates increase and as energy cnsumptin increases. Such systems are applicable t large facilities with large thermal lads such as the fllwing: Assisted Living Facilities Nursing Hmes Senir Husing Apartments and Cndminiums Clleges and Institutins Hspitals Htels Athletic Clubs Industrial and Waste Treatment Facilities Laundries Accrding t the HVAC Systems and Equipment Handbk published by ASHRAE, the basic cmpnents f the cgeneratin plant are Prime mver and its fuel system. Generatr. Waste heat recvery system. Cntrl system. Electrical and thermal transmissin and distributin system. Cnnectins t building mechanical and electrical services. The design team at Burt Hill cnsidered the feasibility f a cgeneratin system t prvide pwer and steam fr the Janelia Farm Research Campus. The fllwing three buildings n the campus were incrprated in this study: Landscape Building: 546,436 square ft research facility. Cnference Husing: 42,000 square ft htel facility with 107 guest rms. Transient Husing: 48-tw bedrm apartments fr lng term visitrs. The cnceptual design included a turbine generatr with adequate capacity t satisfy the minimum cntinuus electrical pwer demand fr the campus. The cntinuus demand ranged frm 2.5 t 3.0 mega-watts. The design featured 500kW gas micr-turbines that culd be staged n/ff t meet 18

3 Julia Thrpe Landscape Building at Janelia Farm Mechanical Optin Final Reprt demand. The system was mre efficient when all the turbines perated cntinuusly. Enugh heat culd be recvered t perate tn absrptin chiller which is equivalent t ne f the seven current chillers. The waste heat culd have met the majrity f the winter heating requirements. This study cncluded an annual savings f $195,640 fr the 2.5 mega-watt cgeneratin system. The estimated first cst was $4,720,000. Based n this, the simple payback perid wuld be 24 years. This was deemed beynd the limits f a reasnable payback perid n such an investment. A secnd study utilizing the 3.0 mega-watt system resulted with an annual cst savings f $214,400, system first cst f $7,080,000, and a 33-year pay back perid. Again, this is beynd reasnable fr a payback perid. Based n these results n further analysis was dne. In rder fr cgeneratin t be feasible fr the Janelia Farm research campus, equipment and installatin csts will have t be greatly reduced. Nte: All dllar values are frm

4 Julia Thrpe Landscape Building at Janelia Farm Mechanical Optin Final Reprt ENERGY RECOVERY WHEELS Anther energy saving ptin that the design team cnsidered was the use f enthalpy wheels r desiccant wheels. During cling mde when utside air is ht and humid, the wheel transfers bth heat and humidity frm the utdr air t the exhaust air. This decreases the cling lad n the ther mechanical equipment. During the cling seasn when utside air is frigid and dry, the wheel transfers heat and humidity t the incming air frm the exhaust air. This decreases the heating lad required f the biler and air handling equipment. There are tw drawbacks t including a wheel in the mechanical system in the Landscape Building. The primary reasn is the risk f crss cntaminatin. As the building is a medical research labratry, there is a always a chance f chemicals, gases, r infectius material becming air-brne in a space and cnsequently the mechanical system. One way the system manages this issue is t prvide 100 percent utdr air t all critical spaces and exhausting 100 percent f that air directly ut f the building. Energy recvery wheels are able t recver energy and misture because they are able t effectively mix the exhaust and supply air streams. Given this, cntaminants will als transfer between air streams. As a result, the cncept f using an enthalpy wheel was nt pursed. Desiccant wheels n the ther hand d nt transfer air-brne cntaminants. The wheel is flushed with supply air that is deflected by a damper in the purging sectin f the rtr. This further helps reduce the risk f cntaminatin. While this may wrk well in thery, the chance that the equipment may nt wrk prperly was a risk the wner was nt willing t take. Using a desiccant wheel was nt pursued. The secnd mre minr drawback is Hward Hughes Medical Institute did nt want t pay fr the equipment and additinal space it wuld take up in the mechanical rms. Figure 3 : Desiccant Wheel Schematic 20

5 Julia Thrpe Landscape Building at Janelia Farm Mechanical Optin Final Reprt HEAT EXCHANGERS Tw types f heat exchangers will be lked int; air-t-air and a plate-type heat exchanger made by CnsERV. Typical air-t-air heat exchangers nly let sensible energy pass thrugh a medium frm ut air stream t the ther. As a result, the air streams never directly interact and cntaminatin f the supply air cannt ccur. N crss cntaminatin is ne f the primary design gals f the riginal design as well as this redesign. The draw back is the lack f latent energy transfer with an airt-air heat exchanger. Humidifiers and dehumidifiers (cling cils) will need t be intrduced and sized int the system t ensure adequate humidity levels. This will add t the first cst f the system as well as energy csts. The integratin f a plate-type heat exchanger made by CnsERV will be analyzed fr effectiveness and amunt f energy saved. As stated in the prduct descriptin, the exchanger is a plate-type heat exchanger wherein the plates are cnstructed f inmer membranes, such as sulfnated r carbxylated plymer membranes, which are capable f transferring a significant amunt f mister frm ne side f the membrane t the ther side. In ther wrds, it is effectively a plate-frame heat exchanger, but instead f using metal r paper, a plymer membrane separates the tw air streams. These membranes are able t transfer bth sensible and latent energy, but the air streams remain cmpletely islated frm each ther. This is the critical feature which makes this a feasible additin t the mechanical system in the Landscape Building. The square bx in the left side f Figure 5 belw is the actual exchanger in ne f the many pssible cnfiguratins. It is pssible t mdel bth types f heat exchangers in HAP 4.20a with prduct infrmatin fund nline. Figure 4 : Membrane Heat Exchanger Schematic 21

6 Julia Thrpe Landscape Building at Janelia Farm Mechanical Optin Final Reprt RUN-AROUND COILS A run-arund cil is a system designed t recver heat frm the exhaust air stream t the utdr air plenum and vice versa t pre-heat and pre-cl the incming air. This is dne by a fin tube cil lcated in the tw air streams. Accrding t the Applicatin Team at the Lawrence Berkley Labratry A high-perfrmance, run-arund energy exchanger can prvide a large increase in verall HVAC system effectiveness frm 50 percent t nearly 70 percent, large returns n investment, typically 33 percent, and shrt payback perids f three years. In new building designs and retrfits, a run-arund system can reduce peak heating and cling lads as well as ttal heating and cling lads. The run-arund system can have a significant impact upn the biler and chiller capacity in new HVAC designs. The A-Team als states that flw rates greater than 10,000 cfm are gd fr using this system. The Landscape Building has utdr air and exhaust air flw rates in excess f 100,000 cfm and the tw plenums are lcated parallel t each ther. Installing a run-arund cil may be an effective way f reducing the amunt f energy needed t cnditin the air. It is pssible t cmbine the run-arund cil lp with the preheat cil t reduce the amunt f pressure drp created by the run-arund cil (labdesignnews.cm). The additin f a run-arund heat recvery system can be mdeled in HAP 4.20a. 22

7 Julia Thrpe Landscape Building at Janelia Farm Mechanical Optin Final Reprt CASE 1 : EXISTING LOAD CALCULATIONS The first step in the mechanical design is t mdel the existing labratry spaces in Carrier s Hurly Analysis Prgram 4.20 as accurately as pssible. The results serve as a benchmark against which all new designs are cmpared and analyzed. The data that was needed included the fllwing: Rm dimensins and rientatin. Wall, ceiling, and flr assemblies. Windw and rf characteristics. Required supply air flw rate fr each rm. Lighting and equipment lads. Air system type and equipment specificatins. System set pints and cntrls. Plant characteristics and cnfiguratins. Infrmatin was btained frm the master drawing set, specificatins, design calculatins, and cnsultants in the field. All dcuments were prvided by the prject manager frm Jacbs Facilities, Inc. and a design engineer at Burt Hill. Results frm this mdel prvided helpful infrmatin abut the current design. Rms were fund t be receiving anywhere frm ne air change per hur t 47, indicating a great deal f ver design. All spaces met ventilatin requirements as utlined in ASHRAE Standard Please see Table 3 belw fr basic system infrmatin. Ttal Cil Lad [tn] Cling Sensible Cil Lad [MBH] Table 3 Case 1 Mechanical System Heating Ttal Cil Lad [MBH] Peak Lad [cfm] 684 4,635 2, ,933 23

8 Julia Thrpe Landscape Building at Janelia Farm Mechanical Optin Final Reprt CASE 2 : EXISTING SPACE WITH MODIFIED EQUIPMENT LOADS AND AIR CHANGES Befre making alteratins t the mechanical system, accurately mdeling the existing building was imprtant. It was als imprtant t determine if the assumptins made during the design prcess were reasnable. Accrding t a research grup f scientists and engineers, Measurements frm varius labratries indicate that peak equipment lad tends t be verestimated greatly (Mathew, 8). If the air system was versized, it wuld be pssible t reduce it t the minimum size and therefre decrease equipment size and energy usage. Existing design dcuments state 20 W/SF equipment lads fr all labratry and labratry supprt spaces. Typically labratries have an equipment lad f 4 W/SF fr lab spaces and a range f 6 t 8 W/SF fr supprt spaces depending n the amunt f equipment (Mathew, 2). The design equipment lads and reduced lads were simulated t cmpare the impact n the mechanical system and energy usage. As a result f the equipment lads fr the Landscape Building being unknwn, a mre cnservative 10 W/SF fr equipment lads was used. This mst likely will result in a larger cling lad and cnsume mre energy than will the actual building. Typically labratry equipment lad schedules were taken frm ASHRAE Standard because the actual schedules are nt knwn. The ccupancy schedules have been taken frm the riginal design calculatins as seen belw in Table 4. Table 4 Occupancy Schedule Space 8:00 am t 4:00 pm 4:00 pm t 12:00 am 12:00 am t 8:00 am Open Labs 80% 55% 45% Lab Supprt 80% 70% 70% The results f the reduced lad mdel did nt have an effect n the required air flw rate as this is a functin f air changes and nt the lad. One result f this adjustment is less energy is used by equipment than expected. Anther gd utcme is the rm air ΔT can decrease t meet the lads with the same amunt f supply air. The rm temperature is set at 70 F/50%RH. q = 1.08cfm ΔT Where q = ttal cling lad ΔT = return air temperature supply air temperature The required supply air temperature required fr the actual design is fund t be 34.1 F frm the fllwing calculatin. 8,028,000 = 1.08(181,933)(75 T supply ) T supply = 34.1 F With the reduced equipment lads, the supply air temperature becmes 6,276,000 = 1.08(181,933)(75- T supply ) T supply = 43.1 F 24

9 Julia Thrpe Landscape Building at Janelia Farm Mechanical Optin Final Reprt As it can be seen in the shrt calculatin abve, reducing the lad has a majr impact n the rm air ΔT. A 21.8% reductin in the lad raises the required supply air temperature by nine degrees. Typically, the lwer practical limit t supply air temperatures is 40 F. Therefre, it can be argued that having T supply = 34.1 F is nt reasnable. The hand calculated supply air quantities were cmbined with the reduced equipment lads t prduce the fllwing results. There was a 23.7% reductin in the ttal cil lad and a 21.7% reductin in the annual energy cst. A mre cmprehensive simulatin result can be fund in Appendix B. Table 5 Ttal Cil Lad [tn] Case 2 Mechanical System Cling Sensible Cil Lad [MBH] Heating Ttal Cil Lad [MBH] Peak Lad [cfm] 522 3,534 1, ,726 As stated abve, after mdeling the existing labratry space it was fund that air chances per hur ranged frm 1 t almst 48. Having 48 air changes per hur is excessive and a large amunt f energy culd be saved by dwnsizing the system. Using the design standards prvided by the engineer, required supply air flw rates were determined by hand calculatins. Care was taken t ensure the spaces were still sized t create negative pressure using the exhaust hds. The wner Hward Hughes Medical Institute typically bases design requirements n The Natinal Institute f Health s (NIH) design standards fr their labratry buildings. In this case, the labratry spaces called fr a minimum f 8 air changes per hur which is greater than the minimum requirement based n NIH design standards. Supprt spaces have a higher lad density and therefre a minimum f 12 air changes per hur shuld be used. There are spaces adjacent t the labratries that were included in this mdel due t their lcatin. They are nt cnsidered lab r supprt spaces and therefre d nt need t be evaluated based n air changes. Instead, ASHRAE Standard 62.1 is applicable. Occupancy classificatin and internal lads were used t determine the minimum amunt f utdr air needed. In the riginal design f the building, these spaces were cnsidered labratry supprt spaces and therefre were greatly ver designed. 25

10 Julia Thrpe Landscape Building at Janelia Farm Mechanical Optin Final Reprt CASE 3 : EXISTING SPACE WITH REDUCED LIGHTING LOADS Fr the lighting system breath wrk f this reprt, the lighting layut and lamp selectin was analyzed t determine if the lad n the spaces culd be reduced. It was cncluded that the layut culd be imprved t prvide a mre unifrm distributin as well as selecting lamps with a better lumen per watt rati. There was a small decrease in the ttal cil lad. It drpped frm 684 tns t 677 tns. The biggest savings can frm reducing the electricity use f the lights by 19.4%.Fr a mre detailed explanatin, please see Appendix C. Table 6 Ttal Cil Lad [tn] Case 3 Mechanical System Cling Sensible Cil Lad [MBH] Heating Ttal Cil Lad [MBH] Peak Lad [cfm] 677 3,222 2,

11 Julia Thrpe Landscape Building at Janelia Farm Mechanical Optin Final Reprt CASE 4 : OVERALL IMPACT OF REDUCED LOADS Case 4 represents cmbining Case 3 with Case 4. The verall impact f simply designing the system t design standards and nt ver sizing is fairly significant. It is significant in the fact that resizing the lighting and reducing the equipment lads prduced an annual savings f $241,077 which is apprximately 25 percent with very little upfrnt cst t the wner. Cmparing the riginal design in Case 1 t the verall results, the ttal cil lad decreased by 28 percent. This case study clearly demnstrates the imprtance f knwing the use and lads f each space as much as pssible during the design prcess. The Landscape Building was put ut t bid very early in the design prcess with nly apprximately 75% f the design cmpleted. The remainder f the design was cmpleted by the cntractrs n site with the aid f shp and fabricatin drawings. Simulatin results can be fund in detail in Appendix D. Table 7 Ttal Cil Lad [tn] Case 4 Mechanical System Cling Sensible Cil Lad [MBH] Heating Ttal Cil Lad [MBH] Peak Lad [cfm] 492 3,337 1, ,726 27

12 Julia Thrpe Landscape Building at Janelia Farm Mechanical Optin Final Reprt GROUD-COUPLED DESIGN GROUND-COUPLED SYSTEMS Grund-Cupled Heat Pumps (GCHPs) are a subset f grund-surce heat pumps (GSHPs). GCHPs use a series f plastic piping buried either hrizntally r vertically in the grund t discharge r gain energy. The grund may be used as a heat sink due t the relatively cnstant temperature by either warming the water during the summer r cling the water in the winter. The benefit f using a GCHP system is the use f free energy which wuld therwise have t be prduced by mechanicals means. The dwnside is the large upfrnt cst f installing the system and the pump energy cnsumed during peratin. One significant design requirement is an adequate amunt f land t install the system. Bres can either be hrizntal r vertical. The benefit f vertical bres include a smaller plt f land is required; the sil temperature varies less at larger depths, and require the smallest amunt f pipe and pumping energy (Kavanaugh 1). In additin, vertical lps are able t transfer mre heat than hrizntal lps. The main drawback t vertical fields is the much higher cst as cmpared t a cmparable hrizntal field. Hward Hughes Medical Institute wns 669 acres n the Janelia Farm Campus. It is prbable that hrizntal piping culd be used if vertical bres are nt necessary. This wuld result in a lwer first cst as vertical drilling can be mre expensive. There are tw ptins fr the type f pipe lp designed; clsed and pen. In a clsed lp, water r a refrigerant slutin are circulated in a piping lp and then heat is exchanged t r frm anther piping lp. This prevents any pssible cntaminatin frm the grund lp t cause prblems in the interir piping and equipment. An pen lp either uses an pen well, stream, r lake as a water surce and then can discharge water back. In the case f a well, at least tw separate wells are required. Open lps tend t be less expensive n a per-tn basis fr large systems and can require n mre maintenance than a typical HVAC system is well deigned (Kavanaugh 5). With pen systems there is the drawback f envirnmental issues that stem frm dumping pssibly cntaminated int a nature water surce. Pssible cnfiguratins include the fllwing: Using the water fr pre-heating cils in the air handlers. Using the water t directly serve the VAV bxes already in the riginal mechanical system design. This cnfiguratin culd use the existing piping that serves the VAV bxes. In this system, the branches f the VAV piping will need t be determined as well as lcatin and sizes f heat exchangers. A typical heat pump system with a central lp and pump. This applicatin is better suited fr smaller buildings. The Landscape Building is t large in size t cnsider using ne pump t serve a system. One lcal lp, multiple heat pumps with pump and check valves n each unit. Multiple individual lps, heat pumps, and circulatr pumps. Multiple units with ne lcal pump that perates when ne r mre unit is n. 28

13 Julia Thrpe Landscape Building at Janelia Farm Mechanical Optin Final Reprt Multiple units with tw-way valves, ne lcal lp, and variable speed pump. Heat pumps and water heater n the same lp t balance lcal lad (Kavanaugh 4). This thesis reprt will determine the best way t use GCHPs in the Landscape Building t bth reduce the amunt f energy required t heat and cl the labratry spaces and reduce the perating csts. SYSTEM DESIGN The grund lp is replacing the cling twers as the means fr releasing and absrbing energy t and frm the atmsphere, instead f designing a typical grund-cupled heat pump system. The fllwing briefly describes the reasns fr this apprach: 1) After cmpleting a rugh estimate calculatin n the size and number f heat pumps that wuld be required t serve the labratry spaces, it was determined that t many heat pumps are required. Apprximately 300 fairly large heat pumps wuld need t be lcated thrughut the labratry spaces. There actually is enugh space in the building t d this. The service crridr lcated behind the ccupied areas has 10 feet dedicated t husing MEP system equipment. While being feasibly, it did nt seem reasnable t install such a large amunt f equipment. The first cst n tp f the cst t install the grund lps wuld have made the system t expensive. 2) The bilers and chiller are used fr ther applicatins besides heating and cling the spaces. The bilers are used t generate steam and ht water that is used by anther building n the site as well as supplying a means f sterilizing labratry equipment in the wash rms. The chiller is used t meet the lads f the cld rms and als the data and cmmunicatin rms which perate n independent systems frm the rest f the building. Therefre, replacing the current system with a heat pump system wuld eliminate the means t meet the lads f these specialized areas. 3) Using a heat pump system t heat and cl the building requires the heat pumps t be lcated near the spaces. This in turn means that the piping will travel frm the space thrugh the building, t a heat exchanger, and then int the lp in the grund. As the Landscape building is fairly lng, this wuld require lps t be cnsiderably large. This wuld increase the pressure drp in the pipes thereby requiring larger pumps that cnsume mre energy. In additin, mre energy wuld be lst ut f the pipe. Therefre, it was determined that cnnecting the grund lp water indirectly int the cndenser side f the chiller will be system f chice fr this reprt. The schematic fr the system if fund belw in Figure 5. 29

14 Julia Thrpe Landscape Building at Janelia Farm Mechanical Optin Final Reprt CHWS CHILLED WATER SUPPLY TO LANDSCAPE BUILDING Tut = 99.5F TYP CH - 1 (VSD) CH - 2 CH - 3 CH - 4 CH - 5 BACK-UP CH - 6 FUTURE CH - 7 FUTURE BYPASS Tin = 85F TYP P-1 (VSD) TYP GLR BACK-UP P-3 (VSD) FUTURE P-4 (VSD) GROUND LOOP RETURN TO BORES Tut = 85F TYP CHILLED WATER RETURN FROM LANDSCAPE BUILDING HTX 1139 GPM TYP HTX 587 GPM TYP Tin = 57F TYP CHWR HTX 587 GPM BACK-UP GLS GROUND LOOP SUPPLY FROM PUMPS P-1 (VSD) TYP P-1 (VSD) TYP P-1 (VSD) TYP P-1 (VSD) BACK-UP GROUND LOOP WATER RETURN FROM LANDSCAPE BUILDING GLR Figure 5 : Cndenser Water Schematic VERTICAL FIELD CONFIGURATIONS Based n the size f the cling lad, vertical lps will better serve the Landscape Building. Typically, vertical bres need t be lcated with a minimum f 15 t 20 feet between bres t ensure heat transfer frm ne bre t anther des nt ccur. It is pssible t use tw U-tubes per bre. While there is less heat transfer per tube, it may be ecnmically viable due smaller first csts in drilling. An ther ptin is whether t use parallel lps r series lps. A parallel-piped vertical heat exchanger can utilize U-tubes with smaller diameters than a series-piped vertical heat exchanger, resulting in lwer piping csts, lwer antifreeze csts, and prbably lwer labr csts because the smaller pipe is easer t wrk with. Parallel lps all have the same amunt f heat transfer where as the series lps have varying heat transfer depending n the lcatin in the series. The bre field will be lcated in the field behind the Landscape Building and then extend east and west f the building. In this lcatin, the piping can extend apprximately 60 feet frm mechanical rm up t the grund surface, drp 120 feet, and then rise 60 feet back t the mechanical rms. The bres will nt extend up as high as the frst line t ensure that freezing is nt an issue. Als, the field in which the bres are lcated is prjected by histric preservatin acts and therefre nthing substantial will ever be installed there. This ensures that the structural integrity f the sil will als nt becme an issue. CHILLER BUILDING LOADS HTX 30 GROUND LOOPS Figure 6 : Grund Lp Diagran

15 Julia Thrpe Landscape Building at Janelia Farm Mechanical Optin Final Reprt Figure 7 : Grund Lp Prpsed Site Figure 7 abve is a rendering f Landscape Building and the surrunding Campus. The building is the series f squares cnnected by a thin white line. These squares are the ffice pds lcated n the secnd and third flrs and are the nly part f the building that is expsed. The building and cluster f trees t the left is an existing ffice building that is currently being used as the trailer fr the prject manager, architect staff, MEP engineers, and the wner s representative. It is still unknwn what plans Hward Hughes Medical Institute has fr these buildings. There is a gd pssibility that they will be demlished after cnstructin is cmpleted. The grup f buildings at the bttm center is the Janelia Farm Mansin and ut buildings. This building is a histric landmark. The view f Sugarlaf Muntain is prtected, meaning nthing can be built that wuld impair this view. The gray lp seen in the field abve is a sidewalk between the tw buildings fr recreatinal use. The area that is prtected is the wedge that begins at the Mansin and extends upward ver the Landscape Building. The bundaries f it are symblically incrprated int the building as the feature stair cases represented by the tw lng rectangular shapes which divide the building int thirds. It is in this area between the Mansin and the Landscape Building that the vertical bre field will be lcated. As calculated abve, the bres will reach a depth f apprximately 120 feet belw grund. With 61,000 feet f piping t handle the design lads f the building, 510 bres are required. There will be 20 feet between bres in all directins t ensure that heat transfer between bres des nt becme a prblem. A 15 x 34 bre r 300 x 680 ft array will accmmdate the number f bres required. The bre array will easily fit within the limits f the field which is well ver 210,000 square feet. After sizing three heat exchangers t serve the lad f the building, the pipe diameter was fund t be 1-1/4 using Table 5.4 fund in Grund Surce Heat Pumps published by ASHRAE. All calculatins can be fund in Appendix E. 31

16 Julia Thrpe Landscape Building at Janelia Farm Mechanical Optin Final Reprt Figure 8 : Bre Diagram Due t the new system cnfiguratin, nly pumps n the grund lp side and heat exchangers needed t be sized. There are thee pumps in parallel serving the grund lps and ne back-up pump. They are 4030 series variable frequency drive pumps frm Armstrng, perating at 3600 rpm. The peak lad efficiency is 78%. The heat exchangers were selected using cmputer sftware prvided by SWEP. There are three heat exchangers in parallel with each ther and in series with the pumps. They each have a flw rate f abut 570 gpm. Cut sheets and pricing infrmatin can be fund in Appendix I. The system cmpnents have been designed in parallel t cntinue the practice f allwing fr easy maintenance r as a safety in case f failure. This design als cnnects in well with the current chiller and pump cnfiguratin. 32

17 Julia Thrpe Landscape Building at Janelia Farm Mechanical Optin Final Reprt POND LOOP CONFIGURATIONS An alternative cnfiguratin is t use the tw existing man-made pnds as heat sinks in an pen lp system. These pnds are lcated just nrth f the Landscape Building and currently serve aesthetic purpses nly. Figure 9 belw in a rending f the Landscape Building and the tw adjacent pnds. Figure 9 : Existing Pnds The lng arched building is the Cnference Husing Building. This building is prvides shrt term husing fr visiting scientists and engineers. The Upper Pnd is 18 feet deep with the bttm elevatin f 240. The pnd is 1.1 millin square feet in area. The Lwer Pnd has a bttm elevatin at 226 and is 12 feet deep. The pnd is slightly smaller than the Upper Pnd with an apprximate area f 590,000 square feet. The prpsed system will draw water frm the Upper Pnd, pump in thrugh the heat exchangers in the mechanical rm in Zne F, and then be pumped thrugh the service crridr that runs between the tw buildings and empty int the Lwer Pnd. Water will als be pumped at the same rate frm the Lwer Pnd t the Upper Pnd t cmplete the full circle. The pumps that mve the water between pnds will be lcated in existing space in the Cnference Husing Building mechanical rm. As the pnds are man-made and a great deal f earth wrk needs t be dne fr their cnstructin, incrprating a series f pipes int that design is relatively simple and shuld nt incur extra majr expenses. BUILDING LOADS CHILLER UPPER POND HTX LOWER POND Figure 10 : Pnd Lp Diagram 33

18 Julia Thrpe Landscape Building at Janelia Farm Mechanical Optin Final Reprt There are series pumps and ne back-up pump frm Bell & Gssett. They run at 1750 rpm and have a peak lad efficiency f abut 79%. The pumps are equipped with a VFD bypass t ensure that the heat exchangers will still receive peak lad flw when the VFD is nt functining. End suctin pumps were selected even thugh they d nt have the best efficiency pssible, they d prevent cavitatin frm ccurring. The pssibility f having t replace a pump early is mre f an ecnmic burden than having t accunt fr a slightly lwer efficiency. The pumps that are lcated between the tw pnds have the same features as the pumps in the mechanical rm. The nly difference is that they are smaller due t small head requirements. Cut sheets can be fund in Appendix I. The pnds have been previusly designed t maintain the same water level thrughut the year thrugh the use f a make-up water system. In the event that this system is nt peratinal there is a small creek that flws int the Upper Pnd. The water discharge and intakes will be lcated as far apart in each pnd t allw the maximum amunt f mixing t ccur s that cnstant temperature water is supplied t the building. All pipe inlets and utlets will be lcated at the bttm f the pnds s as nt t diminish their intended aesthetic quality and t prvide water that has a mre cnstant temperature. There is n data n the thermal prperties f these water surces as they are small manmade pnds and therefre it is assumed that the temperature at the bttm is apprximately the same as the grund temperature fr calculatin purpses. Pipe is sized t 6 using System Syzer Calculatr. 34

19 Julia Thrpe Landscape Building at Janelia Farm Mechanical Optin Final Reprt EMISSIONS & FUEL SAVINGS Emissins and fuel savings is a direct result f smaller lads and mre efficient systems. By designing a lighting system with lamps that prvide mre lumens per watt and mre accurately mdeling the equipment lads, the building is cnsuming less energy. Therefre, the perating csts are dwn as well as emissins rates. Appendix H has cmplete infrmatin n emissins and fuel cnsumptin fr each case. Case 7 uses 28.5% less electricity than the actual system. In additin, emissins decreased by apprximately 30% as well. 35