Energy loss measurement at smoke vents of elevator shafts
Location: St. Francis Hospital, Münster
Date: 19.03.2024
Elevator shafts have legally required openings to the outside. These openings allow the evacuation of fire gases (smoke) in the event of a fire, but also serve to ventilate the elevator shaft. Legal and normative regulations regarding this can be found in the building code (State Building Code) as well as in the European elevator directive and the harmonized standards of the EN81 series.
Through thermal effects, a significant amount of heat energy (heating energy) escapes through the permanent openings.
Elevator shafts in new buildings must be equipped with systems for controlled smoke extraction and ventilation of elevator shafts (so-called elevator shaft ventilation) since the entry into force of the Building Energy Act (GEG). Things are different in the existing building stock: here, statutory preservation of the existing structure applies in principle; that is, at present, equipping elevator shafts with such systems would be a voluntary matter. However, in individual cases, for energy and cost-balance reasons, retrofitting such technology may be very worthwhile.
The measurements are intended to shed light on whether retrofitting shaft smoke extraction systems is economically feasible and worthwhile.
In the case of the measurements under review, these are two elevator shafts at the St. Francis Hospital, where temporary measuring devices were installed at the smoke extraction openings to determine the magnitude of the annual energy loss. An anemometer (TSI VelociCalc 5725) was installed in the respective smoke extraction opening for this purpose.
The TSI VelociCalc 5725 records the flow velocity and temperature of the outgoing air.
An additionally installed temperature logger (DK320) outside the building recorded the outdoor temperature over the measurement period.
The loss energy is calculated from the temperature difference and the volume flow:
Loss energy per year (kWh) = air loss volume per year (m3) x specific heat capacity of air 0.00033 (kWh/m3 K)
Measurement of firefighter lift (serial no. ??)
Opening size 50 x 36 cm
Ø Air speed 1.54 m/s
Ø Volume flow 998 m3/h
Ø Internal temperature 20.42 °C
Ø Outdoor temperature 10.68 °C
Ø Energy loss 3.21 kWh/h
Annual energy loss 28,500 kWh *
Given that the measurement took place at an average outdoor temperature almost year-round, it can be assumed that the annual heating energy loss is approx. 28,500 kWh .
)* Considering that the cross-section of the smoke extraction opening has been reduced by approximately 50% due to the inserted perforated sheet metal, and that an extremely high flow resistance coefficient is present, it can be assumed that the savings potential after adjusting the smoke extraction opening is about twice as high as the measurement has shown.
The current smoke extraction situation does not meet the requirements of the building regulations of NRW.
Measurement of bed elevators 2+3 (serial no. F101150)
Opening size 1 vertical50 x 50 cm
Opening size 2 on the sides40 x 40 cm
Measurement 2:
Ø Air speed 2.03 m/s
Ø Volume flow 1,823 m3/h
Ø Internal temperature 23.23 °C
Ø Outdoor temperature 13.62 °C
Ø Energy loss 5.79 kWh/h
Measurement 3:
Ø Air speed 0.88 m/s
Ø Volume flow 508.97 m3/h
Ø Internal temperature 23.07 °C
Ø Outdoor temperature 15.93 °C
Ø Energy loss 1.68 kWh/h
Annual energy loss (15.93°C) 65,400 kWh
Annual energy loss (10.5°C) 85,500 kWh
Measurements 2 and 3 must be considered cumulatively, as these are two existing openings in the same elevator shaft. As a result, the average energy loss is 7.5 kW/h at an average outdoor temperature of 14.7°C.
The average temperature during the measurement interval was approximately 4.2 degrees above the annual average temperature of Münster (10.5°C) due to the late time of day and sunshine.
Corrected for this effect, the annual energy loss is about 85,000 kWh.
Conclusion
The measurement was conducted only over a short period, however under representative environmental conditions. The elevators were operating normally during the measurement, which is very important. Furthermore, the outdoor temperature was within a range that allows for a meaningful interpretation of the measurement results.
Of course, the results of this measurement cannot be readily transferred to any other elevator system.
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