S. Tafelmeier, G. Pernigotto, G. Pernigotto, A. Gasparella. Free University of Bozen-Bolzano, Faculty of Science and Technology, Italy

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1 ZIMSKI POVRAĆAJ TOPLOTE U VENTILACIONIM SISTEMIMA: POTENCIJALI I OGRANIČENJA OSETNE TOPLOTE I UKUPNI POVRAĆAJ U USLOVIMA EVROPSKIH KLIMA WINTER HEAT RECOVERY IN VENTILATION SYSTEMS: POTENTIAL AND LIMITATIONS OF SENSIBLE AND TOTAL RECOVERY IN THE EUROPEAN CLIMATES S. Tafelmeier, G. Pernigotto, G. Pernigotto, A. Gasparella Free University of Bozen-Bolzano, Faculty of Science and Technology, Italy Beograd, Sava centar, 30. novembar 2. decembar Belgrade, Sava Center, 30 November 2 December 2016

2 Introduction Ventilation load Humidity control Ventilation load: High performance buildings new or renovated have reduced thermal losses through the envelope. Ventilation losses becomes a significant share of the thermal energy needs. Envelope air tightness makes mechanical ventilation often necessary. Heat systems can be deployed. Aim

3 Introduction Ventilation load Humidity control Humidity control: Heat systems in winter mode operation preheat the fresh air by cooling exhausted air. Total heat systems also recover water vapor. Indoor air humidity is relevant for thermal comfort but can impact on occupants performance and satisfaction. If dehumidification is then required because of humidity control, heat can be counter-productive. Aim

4 Introduction Ventilation load Humidity control Aim: Calculate the potential energy and cost from heat in ventilation. Contrast nominal and actual saving when introducing humidity control strategies and limitations to heat. Map the performance in Europe. Aim

5 Ventilation cycle Humidity control Calculation OUTSIDE AIR OA Method Ventilation cycle: heat RECOVERY R EXAUSTED AIR EA air handling MIXED AIR MA RECIRCULATED AIR RA SUPPLY AIR SA RETURN AIR RA

6 Ventilation cycle Humidity control Calculation OUTSIDE AIR OA Method Humidity control: x SA =x RA - m L /m MA x MA x SA =x RA - m L /m MA x R x RA -m L /m OA heat RECOVERY R EXAUSTED AIR EA air handling (steady state moisture balance) (dehumidification not required) (dependence on R humidity) MIXED AIR MA RECIRCULATED AIR RA SUPPLY AIR SA RETURN AIR RA

7 Ventilation cycle Humidity control Calculation Method Humidity control: x R x RA -m L /m OA Specific Latent Load (SLL)=m L /m OA Activity Seated, relaxed Seated, writing Type of Building Theatre, Cinema Offices, Hotel, Apartments Total W Thermal Load per Person Sensib. W Latent W Latent g/h Airchange (2) l/(s person) SLL g v /kg da Eating Restaurants Seated, light activity, typing Slowly walking Offices, Hotel, Apartments Retail store, Bank Moderate dancing Dance Hall Heavy activity Gymnasium

8 Method Ventilation cycle Humidity control Calculation Humidity control: x R x RA -m L /m OA x R 5.7 g/kg (t RA =20 C x RA =7.3 g/kg SLL = 1.6 g/kg) 1. SHR: x OA x RA -m L /m OA 0,0057 Enthalpy kj/kg % 80 % 60 % 50 % 40 % 30 % 20 % 10 % 0,025 0,020 0,015 0,010 0,005 Humidity ratio (kg v /kg da ) 0, Temperature ( C)

9 Method Ventilation cycle Humidity control Calculation Humidity control: x R x RA -m L /m OA x R 5.7 g/kg (t RA =20 C x RA =7.3 g/kg SLL = 1.6 g/kg) 1. SHR: x OA x RA -m L /m OA 2. THR: x OA x RA -m L /m OA x (1-ε) -1 Enthalpy kj/kg % 80 % 60 % 50 % 40 % 30 % 20 % 10 % 0,025 0,020 0,015 0,010 0,005 Humidity ratio (kg v /kg da ) 0, Temperature ( C)

10 Method Ventilation cycle Humidity control Calculation Humidity control: x R x RA -m L /m OA x R 5.7 g/kg (t RA =20 C x RA =7.3 g/kg SLL = 1.6 g/kg) 1. SHR: x OA x RA -m L /m OA 2. THR: x OA x RA -m L /m OA x (1-ε) -1 Enthalpy kj/kg % 80 % 60 % 50 % 40 % 30 % 20 % 10 % 0,025 0,020 0,015 0,010 0,005 Humidity ratio (kg v /kg da ) 0, Temperature ( C)

11 Method Ventilation cycle Humidity control Calculation Humidity control: x R x RA -m L /m OA x R 5.7 g/kg (t RA =20 C x RA =7.3 g/kg SLL = 1.6 g/kg) 1. SHR: x OA x RA -m L /m OA 2. THR: x OA x RA -m L /m OA x (1-ε) -1 or ε 1- x/(x RA -x OA ) Enthalpy kj/kg % 80 % 60 % 50 % 40 % 30 % 20 % 10 % 0,025 0,020 0,015 0,010 0,005 Humidity ratio (kg v /kg da ) 0, Temperature ( C)

12 Ventilation cycle Humidity control Calculation Method Calculation: Energy and cost in ventilation have been determined: Hourly weather data for a whole representative year for 66 climates in Europe Different values of SLL (from 0.8 to 2.4 g/kg) Nominal effectiveness for sensible and total heat : 70 % Seasonal efficiency of 0.8 for the gas water heater Costs charged per kwh for natural gas referred to final domestic users Outcomes represented on Geographic Information System (GIS), averaging the results for all the cities in the same climatic zone according Köppen-Geiger climate classification

13 Sensible heat Results Sensible heat w/o limitation SHR cost Total heat THR cost

14 Sensible heat Results Sensible heat controlled SLL = 0.8 g/kg SHR cost Total heat THR cost

15 Sensible heat Results Sensible heat controlled SLL = 1.2 g/kg SHR cost Total heat THR cost

16 Sensible heat Results Sensible heat controlled SLL = 1.6 g/kg SHR cost Total heat THR cost

17 Sensible heat Results Sensible heat controlled SLL = 2.0 g/kg SHR cost Total heat THR cost

18 Sensible heat Results Sensible heat controlled SLL = 2.4 g/kg SHR cost Total heat THR cost

19 Sensible heat Results SHR cost w/o limitations SHR cost Total heat THR cost 4 >16 color scale from less than 2 EUR (l/s) -1 to more than 16 EUR (l/s) -1 in steps of 2 EUR (l/s) -1

20 Sensible heat Results SHR cost controlled SLL = 1.6 g/kg SHR cost Total heat THR cost 2 16 color scale from less than 2 EUR (l/s) -1 to more than 16 EUR (l/s) -1 in steps of 2 EUR (l/s) -1

21 Sensible heat Results Total heat w/o limitations SLL 1.6 g/kg SHR cost Total heat THR cost

22 Sensible heat Results Total heat controlled SLL 1.6 g/kg SHR cost 24 4 Total heat THR cost

23 Sensible heat Results THR cost w/o limitations SLL 1.6 g/kg SHR cost Total heat THR cost 8 >30 color scale from less than 2 EUR (l/s) -1 to more than 30 EUR (l/s) -1 by 2 EUR (l/s) -1

24 Sensible heat Results THR cost controlled SLL 1.6 g/kg SHR cost Total heat THR cost 2 22 color scale from less than 2 EUR (l/s) -1 to more than 30 EUR (l/s) -1 by 2 EUR (l/s) -1

25 Findings Findings Sensible and total heat increase with duration and severity of the winter climatic conditions, from southern and Mediterranean climates to the northern regions Nominal heat without control strategy is much higher for THR than for SHR - from two to three times - depending on the SLL SHR is reduced by the control strategy from 5 to 65 %, from Nordic to Mediterranean climates and from low to high SLL THR is more affected than SHR, with a reduction from 10 to 93 %, from Nordic to Mediterranean climates and from low to high SLL Costs follow a similar trend, with some variations due to the national energy prices, which may be different in countries with similar climates. Preliminary results: steady state, and winter

26 THANK YOU FOR YOUR ATTENTION! ANY QUESTIONS?