Selected Passive Cooling Techniques Potentials and Constraints Pierre Hollmuller Energy Efficient Building Design: Experiences and Way Forward Indo-Swiss Building Energy Efficiency Project (BEEP) New Delhi, 30 November 2016 Institut Forel / Institut des Sciences de l’Environnement
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Selected Passive Cooling Techniques Potentials and Constraints
Pierre Hollmuller
Energy Efficient Building Design: Experiences and Way Forward
Indo-Swiss Building Energy Efficiency Project (BEEP) New Delhi, 30 November 2016
Institut Forel / Institut des Sciences de l’Environnement
Energy Efficiency and Passive Cooling
Efficient building design / Prevention of heat loads • Microclimate and site design • Building form and layout • Solar control • Thermal insulation • Internal gain control • … Passive cooling / Heat dissipation with natural sinks • Night ventilation • Radiative cooling • Evaporative cooling • Earth coupling • Water source cooling (sea, lake, river) • … Efficient air-conditioning • Water cooling instead of air cooling • VAV air systems • Enthalpy recovery
• Reduction of temperature peaks carried by ventilation
EAT Case Studies
Single family house (Morocco)
• Airflow: 750 – 930 m3/h • 3 pipes (length: 72 m, diameter: 15 cm, depth: 2.2 – 3.5 m) • Design factor: 1 m2 per 9 m3/h
EAT Case Studies
University building (India)
• Airflow: 30’000 m3/h (daytime) • 1 pipe (length: 100 m, diameter: 120 cm, depth: 4 m) • Design factor: 1 m2 per 80 m3/h • EAT + direct evaporative cooling (air washer within AHU)
EAT inlet
EAT outlet
Evaporative cooling
EAT Case Studies
Administrative building (Switzerland)
• Airflow: 12’000 - 18’000 m3/h (daytime) • 43 pipes (length: 23 m, diameter: 250 cm, depth: 0.75 cm
below basement) • Design factor: 1 m2 per 23 m3/h
• Pipe array below insulated basement (no interference with
solar radiation, nor with building)
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Design Guidelines
Reduction of daily oscillation • Soil : 20 - 30 cm around each pipe • Length: 10 - 20 m per 100 m3/h
Reduction of annual oscillation • Soil: 200 - 300 cm around each pipe • Length: 20 - 40 m per 100 m3/h
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°Cair : 200 kg/h
soil : 0.4 m
tube : 50 m
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°Cair : 200 kg/h
soil : 2 m
tube : 50 m
daily storage: ~ 20 cm
yearly storage: ~ 3 m
yearly storage: ~3m
daily storage: ~ 20 cm
Design Guidelines
Reduction of daily oscillation (15% amplitude) Soil around pipe: 20 - 30 cm
Nomographs for daily and annual amplitude reduction
Annual oscillation reduction (15% amplitude) Soil around pipe: 200 - 300 cm
Valid for dry soil (conductivity: 1.1 W/K.m, specific heat: 1.6 MJ/K.m3)
Design Tools
Two complementary tools for the design of EAT:
• EasyPipes Basic: pre-design
• EasyPipes Plus: detailed design
Easypipes Basic: Pre-design
hs
ha
d
• Analytical solution of heat charge and discharge around a pipe
• Excel integrated • Analysis in terms of annual and daily
frequencies
Easypipes Plus: Detailed Design
• Numerical simulation algorithm • Excel interface to Trnsys simulation environment • Transient aiflow • Interference with upper surface and between the pipes • Water condensation/evaporation
EAT + Evaporative Cooling : Potential in New Delhi
Distribution (°C) Return (°C) Return – Distribution (K)
Puissance (kW) Puissance (kW) Puissance (kW)
Distribution temperatures (building)
GLN District Cooling Network (Geneva)
Conclusions
Passive cooling techniques: • diverse techniques / interesting potentials • low energy and maintenance cost • complementary with energy efficiency measures (building and AC system) Constraints: • temperature/enthalpy level of heat sink • investment cost Earth-air tunnels: • existing and validated design guidelines and tools • complement / competition with evaporative cooling (depending on location and period of the