Feasibility of Energy Recovery in Conjunction With The Application of A Redesigned Central Cooling And Heating Plant

Outline Introduction/Background Existing Conditions Problem Statement Energy Recovery System (ERS) Design Central Plant Redesign Electrical Analysis Structural Analysis Life-Cycle Cost Analysis Conclusions and Recommendations

Project Team Owner: QIAGEN Sciences, Inc. Architect: Capital Design Assocs., Inc. CM: Whiting-Turner GC: CDI Engineering Group Mech. Contractor: Pierce Associates MEP Engineer: Herzog-Hart Corp. Structural: Cagley and Associates

Outline Introduction/Background Existing Conditions Problem Statement Energy Recovery System (ERS) Design Central Plant Redesign Electrical Analysis Structural Analysis Life-Cycle Cost Analysis Conclusions and Recommendations

Existing Overall Conditions Location: 118 Germantown Road, Germantown, Maryland Size: 213,000 Ft2 Cost: $52.5 Million Use : Research and production of biotechnological products such as RNA and DNA, state of the art research facilities and laboratory spaces, chemical and biotech storage, and administrative offices

Building 1 Building 2

Existing Mechanical Conditions 16 Air-handling units; 4,770 to 46,105 CFM 5 – 100% Outdoor air units; 4,770 to 18,105 CFM 2 – 900 ton electric driven centrifugal chillers Constant speed primary, variable speed secondary chilled water distribution system 2 – 2,700 GPM induced draft cooling towers 2 – 400 boiler horsepower fire-tube steam boilers 2 – 400 GPM shell and tube steam-to-water heat exchangers Variable speed primary hot water distribution system

Outline Introduction/Background Existing Conditions Problem Statement Energy Recovery System (ERS) Design Central Plant Redesign Electrical Analysis Structural Analysis Life-Cycle Cost Analysis Conclusions and Recommendations

Problem Statement Large energy consumption from the 100% outdoor air air-handling units Energy recovery measures are currently not in place to take advantage of the conditioned air being removed from the spaces Existing 100% Outdoor Air Air-Handling Unit

Existing Chiller Plant Problem Statement Peak summer energy costs coincide with peak central cooling plant loads Currently no approach to reducing peak demand and energy costs Existing Chiller Plant

Outline Introduction/Background Existing Conditions Problem Statement Energy Recovery System (ERS) Design Central Plant Redesign Electrical Analysis Structural Analysis Life-Cycle Cost Analysis Conclusions and Recommendations

Energy Recovery System (ERS) 4 existing 100% outdoor air air-handling units modified with total energy recovery wheels Preheat coil located before enthalpy wheel for fail safe frost protection of the wheel substrate SEMCO TE3 EXCLU-SIEVE® Total Energy Wheels selected to recover both sensible and latent energy

ERS Wheel Selection SEMCO provided performance charts used to select proper wheel size Selection based on supply and return air quantities Return air from general room exhaust, not fume hoods Optimum face velocity of 800 FPM across wheel

Microscopic view of 3Å molecular sieve ERS Performance Controlling cross-contamination is critical for laboratory spaces Adjustable Purge Air Section 3Å Molecular Sieve Desiccant Independent Testing Results Microscopic view of 3Å molecular sieve Purge Air Schematic Testing Results

ERS Energy Analysis Energy analysis for the mechanical system utilizing the ERS is done in conjunction with the central plant redesign The peak preheating load is reduced from 7,015 MBH to 4,650 MBH, a 2,365 MBH reduction The peak cooling load is reduced from 1,045 tons of cooling to 885 tons, a reduction of 160 tons Carrier’s Hourly Analysis Program (HAP) V4.10 used to model base building and ERS design loads

ERS First Cost First cost information is used in the life-cycle cost analysis later on in the presentation Cost information was obtained from Spencer Goland at Rotor Source, Inc.

Outline Introduction/Background Existing Conditions Problem Statement Energy Recovery System (ERS) Design Central Plant Redesign Electrical Analysis Structural Analysis Life-Cycle Cost Analysis Conclusions and Recommendations

Central Plant Redesign The central plant redesigns take into account the load reductions from the ERS design 3 alternatives are analyzed, along with the existing plant Case B Case C Case A 2 – 700 nominal ton electric driven centrifugal chillers Associated primary and secondary chilled water pumps 2 – 2100 GPM cooling towers Associated condenser water pumps 1 – 400 and 1 – 300 boiler horsepower fire-tube steam boilers Associated hot water pumps 1 – 675 nominal ton gas-fired double-effect absorption chiller-heater 1 – 700 nominal ton electric driven centrifugal chiller Associated primary and secondary chilled water pumps 1 – 2700 GPM cooling towers 1 – 2100 GPM cooling tower Associated condenser water pumps 1 – 400 boiler horsepower fire-tube steam boiler Associated hot water pumps 2 – 675 nominal ton gas-fired double-effect absorption chiller-heaters 1 – 200 nominal ton electric driven centrifugal chiller Associated primary and secondary chilled water pumps 2 – 2700 GPM cooling towers 1 – 600 GPM cooling tower Associated condenser water pumps 1 – 100 boiler horsepower fire-tube steam boiler Associated hot water pumps

Central Plant Redesign Modeling The Engineering Equation Solver (EES) is used to model the equipment for each plant case Electric driven chiller modeling DOE2 model for evaluating chiller performance Cooling tower modeling Curve fitting of manufacturer performance curves Pump modeling Curve fitting of manufacturer curves as well as application of pump affinity laws for variable speed application Fire-tube steam boiler modeling Constant efficiency model

Central Plant Redesign Modeling Gas-fired absorption chiller-heater modeling Unique aspect of central plant modeling Chiller-heaters can provide simultaneous heating and cooling York YPC double-effect absorption chiller-heater model Curve fit part load performance charts provided by York for individual and simultaneous operation Individual Performance (York) Individual Performance (EES) Simultaneous Performance (York) Simultaneous Performance (EES)

Central Plant Redesign Modeling Procedures written in EES for base building and 3 redesign case operating sequences Base building and Case A use conventional system Electric driven centrifugal chillers Gas-fired fire-tube steam boilers Case B uses chiller-heaters as main plant Case C utilizes gas-electric hybrid plant Absorption chiller-heater used as primary chiller

Central Plant Redesign Energy Analysis Utility rates are taken from service providers EES produces hourly energy consumption for central plant components Microsoft Excel is used to calculate energy costs

Central Plant Redesign Energy Analysis Total Annual Energy Costs kW Demand charge reductions Central plant gas usage Peak demand kW reductions

Central Plant Redesign First Cost Analysis First cost information for chillers from Jim Thompson at York International R.S. Means First cost for central plant redesign cases Includes main plant equipment Chillers Boilers Heat Exchangers Cooling Towers Pumps Chilled Water Condenser Water Hot Water Plant first cost used in life-cycle cost analysis

Outline Introduction/Background Existing Conditions Problem Statement Energy Recovery System (ERS) Design Central Plant Redesign Electrical Analysis Structural Analysis Life-Cycle Cost Analysis Conclusions and Recommendations

Electrical Analysis The effect of the central plant redesigns on the existing electrical system is analyzed 2 direct points of connection on main switchgear #2 for existing electric driven chillers Existing electrical loads on switchgear #2 Power Panel PP4 Chillers #1 and #2 Emergency Distribution Panel EDP #3 Serves 4 Emergency Motor Control Centers (EMCC) Spare connection

Electrical Analysis Air-conditioning and refrigeration equipment analyzed per NEC 440 Grounding sized according to NEC Table 250-94 Conduit sized according to NEC Chapter 9 kVA demand is calculated for load on switchgear NEC Table 430-150 used to determine the full load current for the motors connected to EMCC’s Feeder sizing done for each case NEC Table 310-16 used for wire ampacity Branch Conductor NEC 430-22 D at 125% of the full load current Overload Protection NEC 430-31 and NEC Table 430-152 ; time delay fuses @ 175% FLC Disconnect NEC 430-110 at 115% of full load current

Electrical Analysis Case A shows no reduction in electrical service Case C reduces load by 558 kVA 2500 kVA transformer downsized to 2000 kVA $6,015 savings Wire size reduced $8,960 savings

Outline Introduction/Background Existing Conditions Problem Statement Energy Recovery System (ERS) Design Central Plant Redesign Electrical Analysis Structural Analysis Life-Cycle Cost Analysis Conclusions and Recommendations

Structural Analysis Analyze the impact of the central plant redesigns on structural system Equipment foundations for centrifugal chillers and gas-fired absorption chiller-heaters Centrifugal chiller foundation design 4 times the equipment weight in concrete for vibration Reinforcing for temperature and shrinkage Absorption chiller-heater foundation design Few moving parts, vibration not critical Foundation needs to support equipment operating weight

Structural Analysis Chiller-heater foundation depth reduced 24” from centrifugal chiller foundation despite weight increase of over 42,000 lbs Reduced depth saves $1,840 compared to base building and Case A foundations Concrete costs Reinforcing steel costs Case C absorption chiller-heater foundation Use 12” depth 1 chiller-heater weighing 65,500 lbs Existing centrifugal chiller foundation 36” depth 2 chillers weighing 27,000 lbs each Design Parameters ACI 318-02 Shrinkage and Temperature Reinforcing Wide Beam Shear Flexure Punching Shear Case A centrifugal chiller foundation Use 36” depth as in existing building 2 chillers weighing 23,400 lbs each

Outline Introduction/Background Existing Conditions Problem Statement Energy Recovery System (ERS) Design Central Plant Redesign Electrical Analysis Structural Analysis Life-Cycle Cost Analysis Conclusions and Recommendations

Life-Cycle Cost Analysis Used to determine most attractive redesign option First cost information combined with annual energy costs calculated in central plant redesigns First costs for ERS design, central plant equipment, structural and electrical redesigns Analysis Method 20 year life cycle ERS replacement at 10 years NIST Energy Price Indices 3.9% discount rate

Life-Cycle Cost Analysis Case A redesign has instant payback Case C payback; 9 months Case C net savings over Case A; $133,132 Difference in LCC savings and first cost savings of 2 cases Case C hybrid plant has lowest LCC Result of reduced annual energy costs $864,475 savings over base building $230,756 savings over Case A redesign

Outline Introduction/Background Existing Conditions Problem Statement Energy Recovery System (ERS) Design Central Plant Redesign Electrical Analysis Structural Analysis Life-Cycle Cost Analysis Conclusions and Recommendations

Conclusions and Recommendations Energy Recovery System Design Effective response to high energy consumption of 100% outdoor air units Decreases size of central cooling and heating plant Central Plant Redesign Case B central plant first cost and required area too high; not a feasible option Cases A and C both provide significant life-cycle cost savings Case C hybrid plant shows best annual energy costs

Conclusions and Recommendations Final Recommendation Implement Case C gas-electric hybrid central plant redesign Short payback period attractive to owner Highest net savings of all options evaluated Flexibility of using either gas-fired chiller-heater or electric driven centrifugal as primary chiller Future electric utility rates may be more or less favorable

Acknowledgements AE Faculty Industry Professionals William P. Bahnfleth, Ph.D., P.E. Stanley A. Mumma, Ph.D., P.E. James D. Freihaut, Ph.D., P.E. Walt Schneider, P.E. Industry Professionals Dave Johnson, P.E. – QIAGEN Sciences, Inc. John Saber, P.E, – Encon Group, Inc. Jim Thompson – York International Corporation Spencer Goland – Rotor Source, Inc. 5th Year AE Students Andy Tech – Mechanical Jim Meacham – Mechanical/CM 242 South Atherton St. – Multi-disciplinary Family, Friends, and People I Forgot

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Energy Recovery System

Central Plant Redesign DOE 2 electric chiller modeling Correction factors based on chilled water and condenser water temperatures Regression coefficients Capacity correction Efficiency correction

Central Plant Redesign Marley Cooling Tower Curves Cooling Tower Modeling Curve fitting using manufacturer plots Linear regressions for each constant range on plot Condenser water temperature is a function of range and wet bulb temperature Curves for full and half speed

Central Plant Redesign Bell & Gossett Pump Curve Pump Modeling Curve fit existing plot Head and efficiency as a function of flow Affinity laws for variable speed pumping Head is function of flow rate and motor speed

Electrical Analysis kVA demand calculations Incorporate demand factor and voltage

Structural Analysis Reinforcing design Chapter 7 specifies minimum area of steel for shrinkage and temperature

Structural Analysis Wide beam shear check Chapter 11.3 – Shear strength for non-prestressed members Chapter 11.12 – Special provisions for slabs and footings Chapter 15.4 – Shear in footings

Structural Analysis Flexure check Chapter 15.4 – Moments in footings Chapter 12 – Development and splices of reinforcement

Structural Analysis Punching shear check Assumes 8”x8” vibration isolation pads at 4 corners Chapter 15.5 – Shear in footings Chapter 11.12 – Special provisions for slabs and footings

Life-Cycle Cost Analysis First cost information Manufacturer cost data R.S. Means cost data Base building first cost Case C first cost Case A first cost