HVAC Efficiency and Baseline Nonresidential HVAC Stakeholder Meeting #2

Transcription

1 1 HVAC Efficiency and Baseline Nonresidential HVAC Stakeholder Meeting #2 California Statewide Utility Codes and Standards Program Abhijeet Pande Heschong Mahone Group, Inc. December 9, /09/2010

2 2 Evaporative Cooling Summary of current code requirements Typical practice Summary of code change proposals Data/findings Specifics of code change proposals Remaining data collection and analysis Specific stakeholder requests

3 Current Code Requirements Evaporative Cooling The ACM provides path for modeling evaporative cooling through optional System 9 ( 3.3.5) Stand-alone evaporative cooling systems, and Evaporative cooling as pre-cooling for other systems Inputs needed for modeling Evaporative cooler fan capacity and brake horsepower (bhp) Water pump capacity and brake horsepower (bhp) Whether evap cooling is stand-alone or as pre-cooling Default inputs provided Direct cooling efficiency Indirect cooling efficiency Can be changed by user 3

4 Typical Practice 4 New construction: Packaged rooftop units dominant type of air conditioners for commercial buildings Single Package Rooftop AC 65% Single Package Rooftop Heat Pump 15% Split System AC 9% Evaporative System 3% Water Loop Heat Pump 6% Split System Heat Pump 2% Data Source: California Nonresidential New Construction Baseline Report RLW Analytics Inc., 1999

5 Typical Practice 5 Retrofits: Typically done with like systems Often at minimal efficiency gains or At prescribed minimum federal efficiency levels New Construction: Higher efficiency projects (e.g. LEED) use Higher efficiency Dx systems Higher efficiency alternate systems such as advanced evaporative cooling, radiant cooling

6 Summary of Code Change Proposals 6 Base Code: Performance credits for high-efficiency evaporative cooling systems Stand-alone indirect systems Packaged/built-up hybrid systems with evap and Dx Reach Code: Best practices: Systems using high-efficiency evaporative cooling systems Stand-alone systems Packaged/built-up hybrid systems with evap and Dx

7 Data / Findings 7 Interviews with manufacturers/designers Western Cooling Challenge Simulation Software Review DOE-2.1E EnergyPlus Engineering Practice Association of Water Technologies Water Management Guidelines

8 Interview Summary 8 Detailed interviews with manufacturers, designers, distributors System types: Direct, Indirect, Indirect/Direct, Hybrid evap + Dx Few packaged products Many built-up products designed to spec System Efficiency: 65-75% efficiency for direct systems Can go as high as 120% of wet-bulb depression with newer indirect systems Building Types: Warehouses, big-box retail, industrial, data centers System costs: Varies depending on system type and usually reported in $/cfm Designers have provided cost quotes of $3/cfm for direct units and $6-$9/cfm or higher for indirect and hybrid units Water management Timed sump flush Conductivity sensors

9 Western Cooling Challenge 9 Established by the Western Cooling Efficiency Center Goals: 40% reduction in energy use and peak demand of roof-top units (RTUs) through Development of new products and improvements to existing products Target RTUs between 3-20 tons, manufacturing capacity >500-units/yr Extensive laboratory testing of equipment at several design conditions

10 Western Cooling Challenge 10 Test Conditions Test Conditions/ Criteria Outside Air Condition (TdbºF/TwbºF) Return Air Condition (TdbºF/TwbºF) Min. Outdoor Ventilation (cfm/nominal-ton) ARI 340/360 WCC Peak WCC Annual 95/75 105/73 90/64 78/67 78/64 78/ External Static (in WC) Min Filtration NA MERV 7 MERV 7 Operating Mode Full Capacity Full Capacity Full or Part Capacity Source: Western Cooling Efficiency Center

11 Western Cooling Challenge 11 Performance Thresholds WCC Peak Conditions Testing done at independent labs WCC Annual Conditions Min Sensible Credited Capacity NA 80% (% sensible credited cooling at peak conditions) Min Sensible Credited EER (kbtu/kwh) Max Supply Air Humidity Max Water Use (gal/ton-h) NA 4 Results include variables above plus Total System EER Source: Western Cooling Efficiency Center

12 Western Cooling Challenge 12 First system to exceed the goals announced in Jan 2010 Small commercial applications 5-ton RTU Energy savings up to 60-80% compared to baseline system Source: Technical Report NREL/TP , September 2009

13 Simulation Software Review 13 DOE 2.1E Pros: Can model both direct and indirect saturation effectiveness Can model both stand-alone and DX integrated systems Cons: M-cycle indirect units with effectiveness greater than 1.0 limited to 1.0 effectiveness Hybrid modeling assumes indirect and DX to be in the same airstream Some newer hybrid evap+dx units have more options of mixing primary and secondary air streams as well as outdoor and return air No account of water usage of the systems

14 Simulation Software Review 14 EnergyPlus Pros: Modules to deal with direct, indirect and hybrid systems Models evaporative pad characteristics (area, depth) that combined with mass flow rate of air calculates saturation effectiveness Can input saturation effectiveness directly as well Models both dry-coil and wet-coil evaporative coolers Models water usage based on evaporative media characteristics Cons: Limited in modeling of some of the newer hybrid evap+dx units that have more options of mixing primary and secondary air streams as well as outdoor and return air Run-time Need for validation

15 Simulation Software Review 15 Engineering Tools Manufacturers have custom software used internally Based on finite element or other first-principles modeling Not available to designers/buyers Engineering firms develop sizing guidelines based on manufacturer published data to meet loads

16 Limitations and Challenges 16 Lack of field-verified performance Even for units tested under laboratory conditions, not enough information available publicly about field performance of the same units Please share if you have such data Lack of unified standards for evaluating evaporative system efficiency California Evaporative Cooler Efficiency Ratio (ECER) uses slightly different criteria than ASHRAE/ARI standards ECER used for listing of equipment, but not for modeling performance WCC has established criteria more suitable for western climates Not the same as the ASHRAE/ARI or ECER metrics

17 17 HVAC Efficiency and Baseline Equivalency with DX systems Courtesy: Jonathan Woolley Western Cooling Efficiency Center

18 Water Usage of Evaporative Systems 18 WCC criteria for max water consumption 4 gal/ton-h at annual test conditions Association of Water Technologies (AWT) Green Task Force Best Practices Guidelines Minimizing water usage, including using non-potable makeup water where available Maximizing energy efficiency through maintaining clean heattransfer surfaces Extending the life cycle of equipment by controlling corrosion and mechanical deterioration of materials Reducing carbon footprint of facilities personnel by integrating cooling water data mining into building management systems Favoring materials and processes friendly to the environment and operator safety Source:

19 Water Usage of Evaporative Systems 19 Association of Water Technologies (AWT) Green Task Force Best Practices Guidelines Option 1 Water System Management Program Water treatment, conductivity controllers, automatic controls to adjust bleed-off Option 2 Use of non-potable water Harvested rainwater, storm water, pass-through cooling water etc. Pre-treatment needed for water to be suitable for use with systems Option 3 achieve both options Source:

20 Specifics of Code Change Proposals 20 Base Code Compliance credit in the performance approach Qualifying criteria Meet the qualifying criteria for the Western Cooling Challenge EER at three test conditions, water usage, cooling capacity Method for Modeling Credit Model Measured Total System EER of the unit at WCC annual conditions Using the DX model in DOE 2.1E

21 Summary of Initial Simulation Runs 21 Energypro simulation of hybrid evap + Dx unit

22 Specifics of Code Change Proposals Credit in the form of modeling EER of the unit at WCC annual conditions using the Dx model embedded in DOE 2.1E Pros: Works with existing simulation tools Conservative savings estimates Performance degradation of the unit at peak conditions similar to Dx units Cons: Conservative savings estimates Dx coil model may not be appropriate for those evaporative systems that work better at peak conditions 22

23 Specifics of Code Change Proposals 23 Base Code Compliance Credit Solution Allow a custom curve for EER of unit at different outdoor and indoor conditions DOE2.1E has built-in capability for custom performance curves Currently used to model higher EER credit for DX units using several outdoor conditions while maintaining 67º F wet-bulb of return air Would need to define custom curve using several outdoor conditions while maintaining 64º F return wet-bulb for this credit

24 Specifics of Code Change Proposals 24 Base Code Compliance Credit Custom Curve Issue Would need to define custom curve using several outdoor conditions while maintaining 64º F return wet-bulb for this credit Need at least four data points of outdoor conditions to generate a bi-quadratic equation Currently only two data points available through WCC testing (WCC peak and WCC annual) Could develop a simple linear equation based on WCC criteria OR request additional data points for testing of units

25 Specifics of Code Change Proposals 25 Reach Code: Develop best practices guidelines for meeting reach code thresholds using evaporative cooling technologies Simulation-based package of measures to meet reach code thresholds Evaluate cost-effectiveness

26 Remaining Data Collection and Analysis 26 Complete interviews with manufacturers/designers Energy Savings Water Consumption Product Availability Analysis Procedures System Costs Evaluate water consumption guidelines Develop controls requirements as basis for compliance credit Complete simulations using proposed EER approach Develop custom curve for high efficient evaporative coolers

27 Specific Stakeholder Requests 27 Field performance data for advanced evaporative cooling systems Delivered cooling capacity as fraction of max at various outdoor temperature conditions Saturation effectiveness Overall system efficiency Water consumption and controls Respond to interview requests to gather data on evaporative systems Additional stakeholders that should be added to the process

28 28 HVAC Baseline and Efficiency QUESTIONS & COMMENTS