planning:building_services:ventilation:comparison_of_energy_performance_of_ventilation_systems_using_passive_vs_active_heat_recovery
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planning:building_services:ventilation:comparison_of_energy_performance_of_ventilation_systems_using_passive_vs_active_heat_recovery [2020/08/10 07:56] – created alang | planning:building_services:ventilation:comparison_of_energy_performance_of_ventilation_systems_using_passive_vs_active_heat_recovery [2023/04/28 17:22] (current) – jgrovesmith | ||
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- | ======Comparison of energy performance of ventilation systems using passive vs. active heat recovery====== | + | ====== Comparison of energy performance of ventilation systems using passive vs. active heat recovery ====== |
Author: Dr Tomas Mikeska, Passive House Institute | Author: Dr Tomas Mikeska, Passive House Institute | ||
- | =====Introduction===== | + | ===== Introduction ===== |
The standard solution for the ventilation of residential as well as non-residential Passive Houses is a ventilation unit equipped with a passive heat recovery or energy recovery core (in the following: “passive system”). The minimum requirement for certification of such systems is a heat recovery efficiency of 75% at a maximum electricity demand of 0.45 Wh/m³. At 15 K temperature difference, the COP of such a system, i.e. the heat recovered divided by the electricity consumption, | The standard solution for the ventilation of residential as well as non-residential Passive Houses is a ventilation unit equipped with a passive heat recovery or energy recovery core (in the following: “passive system”). The minimum requirement for certification of such systems is a heat recovery efficiency of 75% at a maximum electricity demand of 0.45 Wh/m³. At 15 K temperature difference, the COP of such a system, i.e. the heat recovered divided by the electricity consumption, | ||
- | Some manufacturers suggest to replace these passive heat recovery systems by heat pumps which use the extract air as a heat source to heat the supply air (in the following: “active system”). The goal of this article is to compare the energy consumption of passive and active systems for different climates. | + | Some manufacturers suggest to replace these passive heat recovery systems by heat pumps which use the extract air as a heat source to heat the supply air (in the following: “active system”). The goal of this article is to compare the energy consumption of passive and active systems for different climates. |
+ | |||
+ | ===== Methodology ===== | ||
- | =====Methodology===== | ||
The comparison is carried out for nine different climates across North America. By means of an hourly simulation we compare different passive systems and an active system, installed in a building according to the International Passive House standard ([[https:// | The comparison is carried out for nine different climates across North America. By means of an hourly simulation we compare different passive systems and an active system, installed in a building according to the International Passive House standard ([[https:// | ||
- | As a reference, the buildings are equipped with a passive HRV system with an efficiency that is appropriate for the respective location (Table 1). Frost protection is achieved by direct electric preheating of the outdoor air. This reference system provides a certain supply air temperature and requires a certain energy demand for fans and frost protection. | + | As a reference, the buildings are equipped with a passive HRV system with an efficiency that is appropriate for the respective location (Table 1). Frost protection is achieved by direct electric preheating of the outdoor air. This reference system provides a certain supply air temperature and requires a certain energy demand for fans and frost protection. |
- | ^ City ^ Design Temp (< | + | ^ City ^ Design Temp (< |
| Winnipeg | | Winnipeg | ||
| Livingstone | | Livingstone | ||
Line 22: | Line 25: | ||
| Atlanta | | Atlanta | ||
| Seattle | | Seattle | ||
+ | |||
**Table 1: Investigated cities, their design temperatures and the efficiency of the passive systems** | **Table 1: Investigated cities, their design temperatures and the efficiency of the passive systems** | ||
All other systems are assumed to provide the same heating contribution, | All other systems are assumed to provide the same heating contribution, | ||
- | =====Investigated systems===== | + | ===== Investigated systems ===== |
Three passive systems and one active system are investigated: | Three passive systems and one active system are investigated: | ||
- | | + | |
+ | | ||
- Passive energy recovery. Frost protection below -10 °C. | - Passive energy recovery. Frost protection below -10 °C. | ||
- | - Passive heat recovery core using dampers that regularly switch the direction of the airflow in the heat exchanger so that condensation and frost reevaporate. Frost protection is needed only below 19 °C. | + | - Passive heat recovery core using dampers that regularly switch the direction of the airflow in the heat exchanger so that condensation and frost reevaporate. Frost protection is needed only below -19 °C. |
- Active system with COP values according to Table 2. It is assumed that the heat pump will go regularly to defrost mode when the temperature of the air leaving the evaporator drops below 3 °C. In that case the COP is reduced by 20%. | - Active system with COP values according to Table 2. It is assumed that the heat pump will go regularly to defrost mode when the temperature of the air leaving the evaporator drops below 3 °C. In that case the COP is reduced by 20%. | ||
- | + | ^ T< | |
- | ^ T< | + | |
| -3 | 21 | 3.5 | | | -3 | 21 | 3.5 | | ||
| 4 | 21 | 3.3 | | | 4 | 21 | 3.3 | | ||
| 10 | 21 | 3 | | | 10 | 21 | 3 | | ||
+ | |||
**Table 2: COP of active system taken from standard DIN 18599-6: | **Table 2: COP of active system taken from standard DIN 18599-6: | ||
+ | ===== Results ===== | ||
- | =====Results===== | + | As can be seen from Figure 1 and Figure 2, a heat pump used for heat recovery purposes will consume up to **4 times** |
- | As can be seen from Figure 1 and Figure 2, a heat pump used for heat recovery purposes will consume up to **4 times** as much energy as a passive heat recovery ventilator. There is only one case where active and passive heat recovery have approximately the same energy demand: the heat pump compared to a simple heat recovery with direct electric pre-heating for frost protection in the climate of Winnipeg (825 hours with outside temperatures below -20 °C, 2949 hours with outside temperatures below -3 °C). Note that it is generally not recommended to use simple heat recovery ventilators with direct electric pre-heating for frost protection in such cold climates. Even in Livingstone, | + | |
Figure 1 also shows that the additional electricity demand of a heat pump solution for heat recovery is typically on the order of 10 kWh/(m² yr), a value that is much higher than the total electricity consumption for heating in a Passive House with a heat pump system. | Figure 1 also shows that the additional electricity demand of a heat pump solution for heat recovery is typically on the order of 10 kWh/(m² yr), a value that is much higher than the total electricity consumption for heating in a Passive House with a heat pump system. | ||
- | [{{ : | + | [{{ : |
+ | ===== Representation of active heat recovery systems in the PHPP ===== | ||
- | [{{ : | + | Calculating active heat recovery systems in the PHPP requires that the ventilation heat recovery rate is set to zero. This will result in the correct annual heating demand and peak heating load that need to be covered by the heating system. The properties |
- | =====Representation of active heat recovery systems in the PHPP===== | + | [[.: |
- | Calculating active heat recovery systems in the PHPP requires that the ventilation heat recovery rate is set to zero. This will result in the correct annual heating demand and peak heating load that need to be covered by the heating system. The properties of the heat pump in the active heat recovery system, as a function of the ambient temperature, | + | |
- | + | ||
- | {{:picopen:how_to_insert_active_system_in_phpp.pdf|How to insert an active system in PHPP version 9}} | + | |
If space heating is provided by the active heat recovery plus an additional heat pump, or if the active heat recovery system is operating in different modes (outdoor air / recirculation air), the average COP of the total system needs to be entered into the performance map in the Compact worksheet. This will require that the fraction provided by each system is estimated in an auxiliary calculation. | If space heating is provided by the active heat recovery plus an additional heat pump, or if the active heat recovery system is operating in different modes (outdoor air / recirculation air), the average COP of the total system needs to be entered into the performance map in the Compact worksheet. This will require that the fraction provided by each system is estimated in an auxiliary calculation. | ||
- | =====Conclusion===== | + | ===== Conclusion ===== |
- | This article compares a passive heat recovery ventilation core with an ' | + | |
- | It is also important to mention that products | + | This article compares a passive heat recovery ventilation core with an 'active |
- | It should go without saying | + | It is also important to mention |
+ | It should go without saying that the most appropriate mechanical system must always be identified for a specific building. There are cases (e.g. very mild climates) where direct-passive-heat recovery is not absolutely necessary and there are also cases in which extract air heat pumps can be integrated efficiently into the overall mechanical system. Energy modelling provides guidance on the impact on the heating/ | ||
+ | ===== References ===== | ||
- | =====References===== | ||
|Peper 2002|Peper, Søren, Wolfgang Feist: Klimaneutrale Passivhaussiedlung Hannover-Kronsberg. Analyse im dritten Betriebsjahr. Endbericht Mai 2001 bis April 2002. [[https:// | |Peper 2002|Peper, Søren, Wolfgang Feist: Klimaneutrale Passivhaussiedlung Hannover-Kronsberg. Analyse im dritten Betriebsjahr. Endbericht Mai 2001 bis April 2002. [[https:// | ||
- | |Peper 2007|Peper, Søren, Oliver Kah, Rainer Pfluger, Jürgen Schnieders: Passivhausschule | + | |Peper 2007|Peper, Søren, Oliver Kah, Rainer Pfluger, Jürgen Schnieders: Passivhausschule Frankfurt Riedberg. Messtechnische Untersuchung und Analyse. [[https:// |
planning/building_services/ventilation/comparison_of_energy_performance_of_ventilation_systems_using_passive_vs_active_heat_recovery.1597038980.txt.gz · Last modified: 2020/08/10 07:56 by alang