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Berkeley COMPSCI 294 - A Computer Science View of THE LOAD

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9/2/09 1 A Computer Science View of THE LOAD David E. Culler CS294-F09 Feb 2, 2009Where does the energy go? 9/2/09 210-8-2008 3 … Buildings Electricity Water Supply Air People Waste Water Return Air Heat9/2/09 4 Supply Demand Figure'Courtesy'Professor'Arun'Majumdar,'UCB,'LBNL'9/2/09 5 BUILDINGS CONSUME SIGNIFICANT ENERGY Source:(U.S.(Department(of(Energy(2007(Building(Energy(Data(Book.((Sept(2007(The Numbers Tell the Story $370 Billion Total U.S. Annual Energy Costs 200% Increase in U.S. Electricity Consumption Since 1990 40% Total U.S. Energy Consumption for Buildings 72% Total U.S. Electricity Consumption for Buildings 55% Total U.S. Natural Gas Consumption for Buildings9/2/09 6 Buildings Matter! Buildings construction/renovation contributed 9.5% to US GDP and employs approximately 8 million people. Buildings’ utility bills totaled $370 Billion in 2005. Buildings use 72 % of the electricity and 55 % of the nation’s natural gas. Source: Buildings Energy Data Book 20079/2/09 7 EPA Nat Action Plan for Energy Efficiency • 30% of energy consumed in buildings is wasted • 66% electrical, 34% gas and other • 15.5 kWh per square foot * 2003 EIA Commercial Building Consumption SurveyWhere does the energy go in buildings? • HVAC – Heating, Ventilation, Air Conditioning • Lighting • Major Equipment • Plug Loads 9/2/09 89/2/09 9HVAC • Heating – maintain indoor temperature within comfort threshold – ASHRAE 55-1992: 68-75° winter, 73-79° summer (why?) • Ventilation – replacing air in a space to control temperature or remove CO2, contaminants, moisture, odors, smoke, heat, dust and airborne bacteria – ASHRAE 62-1999: 20 CFM per person in work environment • Air Conditioning – provides cooling, ventilation, and humidity control • Provides comfort to people – Humidity, Pressure, Acoustics, Visually pleasing, … – Productivity, durability, health, ... 9/2/09 10Thermodynamics … • 0th Law: If two thermodynamic systems are each in thermal equilibrium with a third, then they are in thermal equilibrium with each other. • 1st Law: Energy can neither be created nor destroyed. It can only change forms. – In any process in an isolated system, the total energy remains the same. • 2nd Law: The total entropy of any isolated thermodynamic system always increases over time, approaching a maximum value. • 3rd Law: the entropy of all systems and of all states of a system is zero at absolute zero" 9/2/09 11Heat Transfer • Conduction – Energy transferred when free atoms collide – 2nd law: from higher to lower – Via a medium (solids, liquids, gas) • Convection – Displacement of molecule groups at a different temperature – Transfer of enthalpy • Radiation – Heat transfer caused by emission and absorption of electromagnetic waves • Latent heat • Thermal Resistance (R-Value) • U = 1/R • Heat Flux: Q = U x A x ΔT 9/2/09 12Heat Gains • Solar Heat Gain • Occupants • Equipment • … 9/2/09 13Psychrometrics • psychrometric ratio – ratio of the heat transfer coefficient to the product of mass transfer coefficient and humid heat at a wetted surface • Specific enthalpy – symbolized by h, also called heat content per unit mass, is the sum of the internal (heat) energy of the moist air in question, including the heat of the air and water vapor within 9/2/09 14HVAC Equipment • Fans / Blowers • Furnace / Heating Unit • Filters • Compressor • Condensing Units • Evaporator (cooling coil) • Control System • Air Distribution System – Ducts, dampers, … 9/2/09 15Building HVAC: Ventilation 9/2/09 16 Supply Air Fan Exhaust Air Fan Return Air Vent Air Vent ZoneBuilding HVAC: AHU 9/2/09 17 Supply Air Fan Exhaust Air Fan Air Handling Unit Return Air Vent Air Vent ZoneAir Handling Unit (AHU) 9/2/09 18Building HVAC: Chilled Water 9/2/09 19 Supply Air Fan Exhaust Air Fan Air Handling Unit Chilled Water Pump Return Air Vent Air Vent ZoneBuilding HVAC: Chiller 9/2/09 20 Supply Air Fan Exhaust Air Fan Air Handling Unit Chilled Water Pump Refrigerant Chiller Compressor Expansion Valve Condenser Evaporator Return Air Vent Air Vent ZoneBuilding HVAC: Cooling 9/2/09 21 Supply Air Fan Exhaust Air Fan Air Handling Unit Chilled Water Pump Refrigerant Chiller Water Condenser Pump Compressor Expansion Valve Condenser Evaporator Cooling Tower Return Air Vent Air Vent Zone AirMajor Equipment 9/2/09 22Building HVAC: Zone Control 9/2/09 23 Supply Air Fan Exhaust Air Fan Air Handling Unit Chilled Water Pump Refrigerant Chiller Water Condenser Pump Compressor Expansion Valve Condenser Evaporator Cooling Tower Return Air Vent Air Vent Damper Zone Reheater AirHeating • AHU Cool + Zone Reheating • AHU + Boiler • Distribute Hot and Cool H2O and mix at zone • Circulate hot H20 + Radiator separate from VAC 9/2/09 24Building HVAC: Major Equipment 9/2/09 25 Supply Air Fan Exhaust Air Fan Air Handling Unit Chilled Water Pump Refrigerant Chiller Water Condenser Pump Compressor Expansion Valve Condenser Evaporator Cooling Tower Return Air Vent Air Vent Damper Zone Reheater Air Conditioner Major Eqmt AirSystem Types and Terms • Packaged Rooftop Unit • Split System • Heat Pump • Geothermal • Air to Air • Hydronic (water) • (Packaged Thermal) PTAC / PTHP • Constant Volume • Variable Volume • Indoor Air Quality • Direct Expansion 9/2/09 26Heat Pump 9/2/09 2710-8-2008 28 Soda HVAC components • Chillers 2 x 130 kw • Colling Towers: 2 x 33.2 kw • Computer Room units: 12 x 45 kVA • AHU SF: 3.2 kw • AHU RF: 2.3 kw • Economizers: 4 x 2.6 kw + 2.1 + 1.4 • Supply fans: 4 x 2.3 kw + 1.4 • Pumps: 2 x 9.3 kw + 2 x 14 kw • Compressors: 2 x 5 kw - It’s all duty cycle10-8-2008 29 Soda Chilled Water • Blow cold air throughout building • Maintain circulation • Adjust cooling with vents and VFDs • Heat it where needed • AC determined by needs of the worst heat load – Comm closet 2x chillers Cooling Towers 287 288 290 340 420 530 Pumps Fans Machine Room ACCs10-8-2008 30 Soda Electrical 12 KV dist. 2x Substation 1200 A 277/480 3 phase 2500 A 120/208 3 phase 2x Chiller MCM1 HP1A 400 HP1A 400 HP2A 600 HP3A 400 HP4A 400


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Berkeley COMPSCI 294 - A Computer Science View of THE LOAD

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