solar utlization lec 15 cooling loads

solar utlization lec 15 cooling loads - Solar Utilization...

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1 Solar Utilization Solar Cooling A tough project to address from a solar point of view: hot and humid climates require low temperature cooling coils for humidity control (45 deg F or less) thermal refrigeration cycles are not very efficient, old Carnot is working against us, COP in the range of 0.4 to 1.0 (1.2 for double effect units) the good news: as solar availability increases, solar cooling load increases not a well developed industry from a solar point of view
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2 Solar Utilization Solar Cooling Solar Thermal Refrigeration cycles we’ll review: solar assisted heat pumps (not really helpful on the cooling side, but we can use night sky radiation to help cooling) absorption refrigeration cycles (ammonia/water, LiBr/water, organic cycles) combined cycles using absorption refrigeration/Rankine combinations Sterling engines, etc. to power conventional vapor compression cycles desiccant dehumidification and cooling jet refrigeration
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3 Solar Utilization Solar Cooling Capacity is an issue and generally will dictate type of refrigeration system to use. For conventional air conditioning 1 to 5 tons DX split and packaged systems, gas fired absorption is available
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4 Solar Utilization Solar Cooling 5 to 100 tons, DX split and package systems, gas fired absorption, steam and HHW
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5 Solar Utilization Solar Cooling 100 tons and up, electric chillers (air cooled up to 150 tons and water cooled above that), gas fired and steam fired absorption chillers
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6 Solar Utilization Solar Cooling 100 tons and up, electric chillers (air cooled up to 150 tons and water cooled above that), gas fired and steam fired absorption chillers Water cooled centrifugal chillers and cooling tower
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7 Solar Utilization Cooling Loads In order to determine the cooling generation system to use, we need to determine the cooling load for the building. There are computerized methods (e.g. Carrier HAP, Trane Trace) and there are manual methods (Air Conditioning Contractors of America (ACCA) manual J method, CLTD method). Let’s look at some of the basics of cooling load calculations:
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8 Solar Utilization Cooling Loads Instantaneous heat gains: rate at which energy is transferred to or generated within a space Heat extraction rate: the rate at which energy is removed from the space by the equipment. .equal to cooling load when equipment is operating and conditions in space are constant. Rare. Temperature varies due to the controls. Cooling load: rate at which energy must be removed from a space to maintain temperature and humidity at the design values
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9 Solar Utilization Cooling Loads Sensible Heat Gains Latent Heat Gains Internal Ventilation Internal Ventilation Lights Outside air People Outside air People Equipment Equipment Infiltration Walls Roof Floor Windows: cond/conv Windows: Solar Infiltration
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10 Solar Utilization Cooling Loads Qsi = internal sensible heat gains Qli = internal latent heat gains Qti = total internal heat gains = Qsi + Qli
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solar utlization lec 15 cooling loads - Solar Utilization...

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