A building controls strategy based on fundamental engineering principles

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1 How is a healthcare facility like a chemical plant? Lessons from chemical engineering for HVAC optimization Edward George & Associates Leslie R. Schulte, PhD Valerie Coulter Eddie McLaughlin A better way to control HVAC systems Engineering fundamentals Mass and energy balances Development of HVAC controls Case studies Economizer decisions Supply temperature resets Central chiller plant flow control Customer summary Questions MWHCEC Engineering fundamentals: Mass and energy are conserved A building controls strategy based on fundamental engineering principles Mass can be moved around and you can change its form, but you can t create or destroy mass Melting Boiling Energy can be moved around and you can change its form, but you can t create or destroy energy Heat Kinetic energy Freezing Condensing Chemical energy Friction 3 4 Moving and altering mass as little as possible minimizes the required energy in chemical plants and buildings Raw materials Electricity and steam Finished product Waste (heat) Unconditioned Electricity, gas, steam, chilled water Relief and exhaust Waste (heat) Modern controls allow for feedback and real-time calculations that enable more sophisticated strategies 5 6 1

2 Today s HVAC systems have a lot of computing power, but are often underutilized Honeywell s Series 16 Direct Digital Control for Process Control Standard protocols (or rules) for communication between devices allows for expanded integration The newer the controls, the more of our process can be implemented with no capital improvements Significant investment capital required 50% 80-90% % s 1990s 2000s Expanded capability to Reduction in size and cost of microprocessors leads to digital combine multiple manufacturers products Pre-1990s 1990s 2000s 2010s controls widely accepted in on the same supervisory new buildings controller 7 8 uses existing equipment to develop short and long-term strategies for reducing energy use Perform building assessment Implement semi-standard chemical engineering strategy Identify buildingspecific optimization opportunities Identify operational and capital improvements for longer term costsavings Case studies: Specific optimization strategies for improving occupant comfort and minimizing energy use 9 10 Typical economizer decision is based on drybulb temperature Temp: 78 F Humidity: 55%RH Return from Economizer decisions Typical dry bulb cutoff Aggressive: 65 F Conservative: 55 F Temp: 70 F Outside Humidity: 70%RH Temp: 55 F Humidity: 85%RH Supply to

3 Change in supply temperature ( F) Supply temperature ( F) 11/2/2017 An energy-based comparison is best because even the most aggressive temperature decision leaves money on the table Enthalpy is the sum of internal energy plus the product of pressure and volume Enthalpy: 31 Btu/lb Temp: 78 F Humidity: 55%RH Return from In Indianapolis, replacing a dry-bulb decision with an enthalpy-based decision results in 5% more free-cooling 180,000 ft $105,000 Temp: 70 F Outside Humidity: 70%RH Enthalpy: 28 Btu/lb Temp: 55 F Humidity: 85%RH Supply to Enthalpy: 21 Btu/lb The change in enthalpy (at constant pressure) is the total heat removed from the 13 District steam & chilled water Johnson Controls 82% 1.3 million kwh saved over 1 year 14 Canned supply temperature resets might save money, but can cause occupant comfort issues 70 Return from 65 Supply temperature resets Outside Supply to Outside temperature ( F) A supply reset based on a building s current needs saves money and keeps occupants happy Mississippi medical office building with supply reset saved $12 per $1 spent on services 1 Return from ,000 ft $317,000 Outside Supply to Average VAV temperature offset ( F) 17 Electric Trane 60% 3.8 million kwh saved over 3 years 18 3

4 Variable volume chiller plant control applied to medical office building Central chiller plant flow control 285,000 ft 2 Central chilled water plant and electric heat 1980 Niagara January 2015 CLIENT SINCE Indianapolis LOCATION flow saves energy on pumping Constant Volume Chiller 3-Way Valve flow saves energy on pumping Chiller 2-Way Valve AHU Coil Bypass Valve AHU Coil Goals: Maintain chilled water flow through chiller Minimize pumping required to satisfy system load with the current chilled water supply temperature 21 Goals: Maintain chilled water flow through chiller Minimize pumping required to satisfy system load with the current chilled water supply temperature 22 flow provides energy savings on pumping Indianapolis medical office building with chiller plant optimization saved $5 per $1 spent with Constant Volume Daily Energy Usage Daily Energy Cost 600 kwh $ kwh $ ,000 ft $370,000 Yearly Energy Cost $17,500 $8,200 Represents 3.5% Yearly Savings $9,300 of the primary service electrical costs Energy consumption is proportional to the cube of the pump speed. Rated energy consumption of each chilled water pump is 25 kw. Typical daily usage is approximately 8 hrs at 100%, 8 hrs at 70% and 8 hrs at 40%. Due to limitations on economizer, chilled water system runs year round. Electrical rate is approximately $0.08/kWh. 23 Central chilled water plant and electric heat Niagara 72% 4.5 million kwh saved over 2 years 24 4

5 has lowered utility costs for building owners across the country Washington, D.C. Total energy saved 120,000 MMBtu $1.5 million $7 saved/$1 spent 9 years Evansville, IN 24,800 MMBtu $370,000 $6 saved/$1 spent 1 year Total avoided costs $ saved/$ spent Years as client Indianapolis, IN 42,500 MMBtu $1.1 million $5 saved/$1 spent 6 years Jackson, MS 12,900 MMBtu $320,000 $12 saved/$1 spent 4 years Questions Edward George & Associates works on behalf of building owners and operators to better utilize existing control systems and mechanical equipment to reduce utility costs and improve operations. Indianapolis, IN 46,300 MMBtu $105,000 $16 saved/$1 spent 1 year