Energy Efficient Heating Ventilating and Air Conditioning

Facility Energy Balance

Fundamental Equation Qf = [(A/R + V pcp) (Tia – Toa) – Qint] / Eff A = area of envelope R = thermal resistance of envelope V = air flow rate pcp = product of air density and specific heat Tia = inside air temperature Toa = outside air temperature Qint = internal heat gain Eff = efficiency of heating equipment

Energy Saving Opportunities Increase insulation: R Decrease outdoor air flow rate: V Decrease inside air temperature: Tia Maximize utilization of internal heat: Qint Increase efficiency: Eff

Increase Insulation

Insulate Un-insulated Walls/Ceilings Diminishing return of increasing insulation Adding R=10 hr-ft 2 -F/Btu and (Tia – Toa) = 35 F

Insulate Metal Walls Insulate walls with spray-on cellulose or closed-cell foam

Cover Single-pane Glass with Double-Wall Polycarbonate Sheets

Replace Single Pane Skylights with Double-Wall Polycarbonate R = 1 to R = 4 Heating Cost Saving = $0.90 / ft 2 - yr Cost = $2 / ft 2

Insulate Dock Doors

Reduce Air Flow

Air Flow Fundamentals Air flow in = Air flow out Most plants exhaust more air than MAUs supply Causes negative pressure and infiltration Infiltration air reduces comfort, and heating energy

Close Doors and Openings Install garage-door openers on lift-trucks to close shipping doors!

Close Doors and Openings Install garage-door openers on lift-trucks Observation: Heating energy varies by 3X at same temp! Discovery: Didnt close shipping doors!

Seal Unused Exhaust Fans

Reduce Stack-Driven Infiltration

Turn Off Excess Exhaust/Ventilation

Turn Off Dust Collectors When Not In Use

Shut Blast Gates to Dust Collectors When Not In Use

Filter and Return Clean Air to Plant

Scrap Paper Collector

Install VFDs on Vent Hoods

Supply Outside Air to Exhaust Air Locations

Scrap Transport System

Reverse Exhaust Fan Direction to Utilize Heat from Equipment

Balance Plant Air Pressure with Differential Pressure Controlled MAUs Manometer measures pressure difference and adjusts MAU air flow Good choice if ventilation requirements change frequently (paint booths, etc.) Minimizes infiltration and facilitates lower inside air temperature

Use Indoor Heaters For Envelope Loss and Make-up Air Units to Heat Outside Air Unit/IR/air rotation heaters –Reheat indoor air/space –80% efficient since exhaust combustion gasses Direct-fire make-up air units –Bring in and heat outside air –100% efficient since combustion gasses added to outside air Selection: –Heating outside air, even at 100% efficiency, requires more energy than re-heating inside air at 80% efficiency. –Use unit/IR heaters to make up envelope losses –Use make-up air units to heat outside air

Reduce Indoor Air Temperature

Move Thermostat Off Exterior Walls

Use Programmable Thermostats Lower/increase interior set-point temp during unoccupied periods Important because heating/cooling load proportional to (Tia – Toa) Example: If Toa = 50 F, then reducing Tia from 70 F to 60 F decreases heating load by 50% However, thermal mass limits temperature drop and reduces savings

Reduce Temperature Stratification With High-Volume Low-Velocity Fans Problem –Excess temperature stratification Solution –Install destratification fans

Reduce Temperature Stratification With Gas-Fired Infrared Heaters Problem –Warm air removed by exhaust fans or openings –Excess temperature stratification (warm air near ceiling) Solution –Install radiant heaters

Decrease Space Cooling Energy

Replace Dark Roof with White Roof White roofs reflect sunlight and reduce roof cooling load by over 50%

Use Economizer For Year-round Cooling Economizers vary positions of dampers to use outdoor air when Toa < Treturn

Identify Economizer Failure with LEA Cooling slope should flatten at low temps Broken and missing damper gears

Verify Economizer Savings In year-round cooling, can reduce cooling electricity use by ~40%

Increase Cooling Air Set-point Temperature During Cool Weather Higher cooling air set-point temperature: Increases cooling load offset by economizer Decreases re-heat (if any) Decreases compressor load.

Purchase High-Efficiency Roof-top Units

Case Study 1 Reduce winter ventilation & balance air pressure Weather-adjusted gas use reduced by 51%.

Case Study: Reduce Winter Ventilation & Balance Air Pressure

Reduce Winter Ventilation & Balance Air Pressure Weather-adjusted baseline gas use reduced by 51%.