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Low-Temperature Heating and Ventilation for Sustainability in Energy Efficient Buildings
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.ORCID iD: 0000-0001-8614-5806
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In 2013, the building sector consumed approximately 39 % of the total final energy use in Sweden. Energy used for heating and hot water was responsible for approximately 60 % of the total energy consumption in the building sector. Therefore, energy-efficient and renewable-based heating and ventilation systems have high potential for energy savings. The potentials studied in this thesis include the combination of a low-temperature heat emitter (supply temperature below 45 °C) with heat pump and/or seasonal thermal energy storage, and variable air volume ventilation system. The main aim of this thesis was to evaluate energy savings and indoor air quality when those energy-efficient and sustainable heating and ventilation systems were implemented in buildings. For this purpose, on-site measurements, lab tests, analytical models, and building energy simulation tool IDA Indoor Climate and Energy 4 were used.

Annual on-site measurements for five new two-family houses with low- and very-low-temperature heat emitters connected to an exhaust air heat pump showed  that  between  45–51 kWh∙m-2 energy was used  to  produce  and transport supply water for space heating and domestic hot water. Statistical data showed that these values are 39–46 % lower compared to the energy requirement for the same usage  which is, 84 kWh∙m-2)  in  an  average Swedish new single- and two-family house.

Annual on-site measurements for five new two-family houses with low- and very-low-temperature heat emitters connected to an exhaust air heat pump showed that between 45–51 kWh∙m-2 energy was used to produce and transport supply water for space heating and domestic hot water. Statistical data showed that these values are 39–46 % lower compared to the energy requirement for the same usage (which is, 84 kWh∙m-2) in an average Swedish new single- and two-family house.

In order to compare the energy performance of very-low- and low-temperature heat emitters with medium-temperature heat emitters under the same condition, lab tests were conducted in a climate chamber facility at Technical University of Denmark (DTU). To cover the heat demand of 20 W·m-2 by active heating, measurements showed that the required supply water temperatures were 45 ºC for the conventional radiator, 33 ºC in ventilation radiator and 30 ºC in floor heating. This 12–15 ºC temperature reduction with ventilation radiator and floor heating resulted in 17–22 % savings in energy consumption compared to a reference case with conventional radiator.

Reducing the supply temperature to the building’s heating system allows using more renewable and low-quality heat sources. In this thesis, the application of seasonal thermal energy storage in combination with heat pump in a building with very-low-, low-, and medium-temperature heat emitters was investigated. Analytical model showed that using a 250 m3 hot water seasonal storage tank connected to a 50 m2 solar collector and a heat pump resulted in 85–92 % of the total heat demand being covered by solar energy.

In addition to the heating system, this thesis also looked at ventilation system in terms of implementing variable (low) air volume ventilation instead of a constant (high) flow in new and retrofitted old buildings. The analytical model showed that, for new buildings with high volatile organic compound concentration during initial years of construction, decreasing the ventilation rate to 0.1 L·s-1·m-2 during the entire un-occupancy period (from 8:00–18:00) creates unacceptable indoor air quality when home is occupied at  18:00.  So,  in  order  to  create  acceptable  indoor  air  quality  when  the occupants come home, a return to the normal ventilation requirements was suggested to take place two hours before the home was occupied. This eight- hour ventilation reduction produced savings of 20 % for ventilation heating and 30 % for electricity consumption by ventilation fan.

In addition, the influence of different ventilation levels on indoor air quality and energy savings was studied experimentally and analytically in a single- family house occupied by two adults and one infant. Carbon dioxide (CO2) concentration as an indicator of indoor air quality was considered in order to find  appropriate  ventilation  rates.  Measurements  showed  that,  with  an 0.20 L∙s-1∙m-2  ventilation rate, the CO2   level  was always below 950 ppm, which shows that this level is sufficient for the reference building (CO2 lower than 1000 ppm is acceptable). Calculations showed that low ventilation rates of 0.20 L∙s1∙m-2 caused 43 % savings of the combined energy consumption for  ventilation  fan  and  ventilation  heating  compared  to  the  cases  with 0.35 L∙s-1∙m-2  as a normal ventilation rate recommended by BBR (Swedish Building Regulations).

 

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2015. , x, 40 p.
Keyword [en]
Low-temperature heating system, Energy savings, Seasonal thermal energy storage, Variable air volume ventilation system, Indoor air quality
National Category
Building Technologies
Identifiers
URN: urn:nbn:se:kth:diva-170065ISBN: 978-91-7595-650-3 (print)OAI: oai:DiVA.org:kth-170065DiVA: diva2:827073
Public defence
2015-09-04, M3, Brinellvägen 64, KTH, Stockholm, 13:00 (English)
Opponent
Supervisors
Note

QC 20150626

Available from: 2015-06-26 Created: 2015-06-26 Last updated: 2015-08-11Bibliographically approved
List of papers
1. Energy performance of low temperature heating systems in five new-built swedish dwellings: A case study using simulations and on-site measurements
Open this publication in new window or tab >>Energy performance of low temperature heating systems in five new-built swedish dwellings: A case study using simulations and on-site measurements
2013 (English)In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 64, 85-93 p.Article in journal (Refereed) Published
Abstract [en]

In Europe, high energy consumption in built environments has raised the need for developing low energy heating systems both in new building and in retrofitting of existing buildings. This paper aims to contribute by presenting annual results of calculated and measured energy consumption in five new-built semi-detached dwellings in Stockholm, Sweden. All buildings were equipped with similar low temperature heating systems combining under-floor heating and ventilation radiators. Exhaust ventilation heat pumps supported the low temperature heating system. Buildings were modeled using the energy simulation tool IDA Indoor Climate and Energy (ICE) 4, and energy consumption of the heat pumps was measured. Results showed that calculated and measured results were generally in agreement for all five dwellings, and that the buildings not only met energy requirements of the Swedish building regulations but also provided good thermal comfort.

Keyword
Energy performance, High energy consumption, IDA ICE 4, Low temperature heating, Low temperatures, Measured energy consumption, Site measurements, Ventilation radiators, Building codes, Energy efficiency, Energy utilization, Heat pump systems, Housing, Temperature, Heating equipment, building, energy use, heating, low temperature, ventilation, Stockholm [Sweden], Sweden
National Category
Building Technologies
Identifiers
urn:nbn:se:kth:diva-123567 (URN)10.1016/j.buildenv.2013.02.009 (DOI)000319548100009 ()2-s2.0-84876331057 (Scopus ID)
Funder
Swedish Energy Agency
Note

QC 20160623

Available from: 2013-06-12 Created: 2013-06-12 Last updated: 2017-12-06Bibliographically approved
2. Experimental study of energy performance in low-temperature hydronic heating systems
Open this publication in new window or tab >>Experimental study of energy performance in low-temperature hydronic heating systems
2015 (English)In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 109, 108-114 p.Article in journal (Other academic) Published
Abstract [en]

Energy consumption, thermal environment and environmental impacts were analytically and experimentally studied for different types of heat emitters. The heat emitters studied were conventional radiator, ventilation radiator, and floor heating with medium-, low-, and very-low-temperature supply, respectively. The ventilation system in the lab room was a mechanical exhaust ventilation system that provided one air change per hour of fresh air through the opening in the external wall with a constant temperature of 5 °C, which is the mean winter temperature in Copenhagen. The parameters studied in the climate chamber were supply and return water temperature from the heat emitters, indoor temperature, and heat emitter surface temperature. Experiments showed that the mean supply water temperature for floor heating was the lowest, i.e. 30 °C, but it was close to the ventilation radiator, i.e. 33 °C. The supply water temperature in all measurements for conventional radiator was significantly higher than ventilation radiator and floor heating; namely, 45 °C. Experimental results indicated that the mean indoor temperature was close to the acceptable level of 22 °C in all cases. For energy calculations, it was assumed that all heat emitters were connected to a ground-source heat pump. Analytical calculations showed that using ventilation radiator and floor heating instead of conventional radiator resulted in a saving of 17% and 22% in heat pump's electricity consumption, respectively. This would reduce the CO2 emission from the building's heating system by 21 % for the floor heating and by 18% for the ventilation radiator compared to the conventional radiator.

Place, publisher, year, edition, pages
Elsevier, 2015
Keyword
Low-temperature hydronic heating systems; Energy performance; Thermal environment; Experimental study; Ventilation radiator; Floor heating
National Category
Building Technologies
Identifiers
urn:nbn:se:kth:diva-172002 (URN)10.1016/j.enbuild.2015.09.064 (DOI)000367115300010 ()2-s2.0-84944749414 (Scopus ID)
Funder
Swedish Energy Agency
Note

QC 20160128

Available from: 2015-08-11 Created: 2015-08-11 Last updated: 2017-12-04Bibliographically approved
3. Seasonal thermal energy storage with heat pumps and low temperatures in building projects-A comparative review
Open this publication in new window or tab >>Seasonal thermal energy storage with heat pumps and low temperatures in building projects-A comparative review
2015 (English)In: Renewable & sustainable energy reviews, ISSN 1364-0321, E-ISSN 1879-0690, Vol. 43, 1199-1213 p.Article, review/survey (Refereed) Published
Abstract [en]

Application of seasonal thermal energy storage with heat pumps for heating and cooling buildings has received much consideration in recent decades, as it can help to cover gaps between energy availability and demand, e.g. from summer to winter. This has the potential to reduce the large proportion of energy consumed by buildings, especially in colder climate countries. The problem with seasonal storage, however, is heat loss. This can be reduced by low-temperature storage but a heat pump is then recommended to adjust temperatures as needed by buildings in use. The aim of this paper was to compare different seasonal thermal energy storage methods using a heat pump in terms of coefficient of performance (COP) of heat pump and solar fraction, and further, to investigate the relationship between those factors and the size of the system, i.e. collector area and storage volume based on past building projects including residences, offices and schools.

Keyword
Seasonal thermal energy storage, Heat pump, Solar fraction, Coefficient of performance of heat pump
National Category
Energy Engineering
Identifiers
urn:nbn:se:kth:diva-161099 (URN)10.1016/j.rser.2014.12.002 (DOI)000348880600094 ()2-s2.0-84919820148 (Scopus ID)
Note

QC 20150623

Available from: 2015-03-24 Created: 2015-03-09 Last updated: 2017-12-04Bibliographically approved
4. Low-temperature Heat Emission Combined with Seasonal Thermal Storage and Heat Pump
Open this publication in new window or tab >>Low-temperature Heat Emission Combined with Seasonal Thermal Storage and Heat Pump
2015 (English)In: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, Vol. 119, 122-133 p.Article in journal (Refereed) Published
Abstract [en]

We studied the application of a stratified seasonal hot water storage tank with a heat pump connected to medium-, low- and very-low-temperature space heat emissions for a single-family house in Stockholm, Sweden. Our aim was to investigate the influence of heat emission design temperature on the efficiency and design parameters of seasonal storage in terms of collector area, the ratio of storage volume to collector area (RVA), and the ratio of height to diameter of storage tank. For this purpose, we developed a mathematical model in MATLAB to predict hourly heat demand in the building, heat loss from the storage tank, solar collector heat production, and heat support by heat pump as a backup system when needed. In total, 108 cases were simulated with RVAs that ranged from 2 to 5 (m3 m−2), collector areas of 30, 40, and 50 (m2), height-to-diameter-of-storage-tank ratios of 1.0, 1.5, and 2.0 (m m1), and various heat emissions with design supply/return temperatures of 35/30 as very-low-, 45/35 as low-, and 55/45 (°C) as medium-temperature heat emission. In order to find the best combination based on heat emission, we considered the efficiency of the system in terms of the heat pump work considering coefficient of performance (COP) of the heat pump and solar fraction. Our results showed that, for all types of heat emission a storage-volume-to-collector area ratio of 5 m3 m2, with a collector area of 50 m2, and a height-to-diameter ratio of 1.0 m m1 were needed in order to provide the maximum efficiency. Results indicated that for very-low-temperature heat emission the heat pump work was less than half of that of the medium-temperature heat emission. This was due to 7% higher solar fraction and 14% higher COP of heat pump connected to very-low-temperature heat emission compared to medium-temperature heat emission.

Place, publisher, year, edition, pages
Elsevier, 2015
Keyword
Seasonal thermal energy storage, Stratified storage tank, Heat pump, Low-temperature heat emission
National Category
Building Technologies
Identifiers
urn:nbn:se:kth:diva-170067 (URN)10.1016/j.solener.2015.06.046 (DOI)000361583300010 ()
Funder
Swedish Energy Agency
Note

QC 20150723

Available from: 2015-06-26 Created: 2015-06-26 Last updated: 2017-12-04Bibliographically approved
5. Demand-controlled ventilation in new residential buildings: consequences on indoor air quality and energy savings
Open this publication in new window or tab >>Demand-controlled ventilation in new residential buildings: consequences on indoor air quality and energy savings
2015 (English)In: Indoor + Built Environment, ISSN 1420-326X, E-ISSN 1423-0070, Vol. 24, no 2Article in journal (Refereed) Published
Abstract [en]

The consequences on indoor air quality (IAQ) and potential of energy savings when using a variable airvolume (VAV) ventilation system were studied in a newly built Swedish building. Computer simulationswith IDA Indoor Climate and Energy 4 (ICE) and analytical models were used to study the IAQ andenergy savings when switching the ventilation flow from 0.375 ls1m2 to 0.100 ls1m2 duringunoccupancy. To investigate whether decreasing the ventilation rate to 0.1 ls1m2 during unoccupancy,based on Swedish building regulations, BBR, is acceptable and how long the reduction can lastfor an acceptable IAQ, four strategies with different VAV durations were proposed. This study revealedthat decreasing the flow rate to 0.1 ls1m2 for more than 4 h in an unoccupied newly built buildingcreates unacceptable IAQ in terms of volatile organic compounds concentration. Hence, if the durationof unoccupancy in the building is more than 4 h, it is recommended to increase the ventilation rate from0.100 ls1m2 to 0.375 ls1m2 before the home is occupied. The study showed that when the investigatedbuilding was vacant for 10 h during weekdays, increasing the ventilation rate 2 h before occupantsarrive home (low ventilation rate for 8 h) creates acceptable IAQ conditions. In this system, theheating requirements for ventilation air and electricity consumption for the ventilation fan weredecreased by 20% and 30%, respectively.

Place, publisher, year, edition, pages
Sage Publications, 2015
Keyword
Controlled ventilation system, Energy performance, IDA ICE 4, Indoor air quality, Variable air volume
National Category
Building Technologies
Identifiers
urn:nbn:se:kth:diva-123568 (URN)10.1177/1420326X13508565 (DOI)000351700600003 ()2-s2.0-84925293881 (Scopus ID)
Funder
Swedish Energy Agency
Note

QC 20150429

Available from: 2013-06-12 Created: 2013-06-12 Last updated: 2017-12-06Bibliographically approved
6. Influence of Different Ventilation Levels on Indoor Air Quality and Energy Saving: a Case Study of a Renovated Single-family House
Open this publication in new window or tab >>Influence of Different Ventilation Levels on Indoor Air Quality and Energy Saving: a Case Study of a Renovated Single-family House
(English)Manuscript (preprint) (Other academic)
National Category
Building Technologies
Identifiers
urn:nbn:se:kth:diva-170068 (URN)
Note

QS 2015

Available from: 2015-06-26 Created: 2015-06-26 Last updated: 2015-08-11Bibliographically approved

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