Influence of occupants' behavior on the performance of net-zero emission buildings
Doctoral thesis
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http://hdl.handle.net/11250/279453Utgivelsesdato
2014Metadata
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This thesis investigates how the occupant behavior influences the performance of residential
net zero emission buildings (Net-ZEB) in cold climates such as in Norway, and
proposes guidelines for better design, operation and control strategies. The thesis focuses
on the occupant related variations in the internal gains and the domestic hot water use,
and studies their influence on the building’s heating needs, its heating system performance
and finally, its interaction with the onsite renewable generation and the grid.
The application of the tightly insulated envelope in Net-ZEB significantly reduces the
space heating needs. This increases the share of the occupant-related heat gains in the
total space heating needs, and the related DHW heating in the total heating needs of the
building. These changes can eventually influence the heating system and its interaction
with the grid.
This research analyzes a typical single-family detached house. Such houses are the most
common type of residences in Norway. There is a large variation in the occupancy, household
appliances, and work-schedules in these houses. This research models these occupant
variations, and classifies them using three parameters; the occupancy patterns, the appliance
use behavior and the family size.
This study compares a ‘low-energy house class 2’ building with a moderate insulation, and
a ‘passive house’ with a very tight insulation. The comparison confirms an increase in the
significance of the occupant behavior with increasing insulation. Extensive investigation
of each parameter on the building gives an interesting insight into the relation of these
occupant parameters with the building and the response of its heating system.
The building’s net energy needs and the performance of the heating system are directly
dependent on the internal gains and the domestic hot water use of the households, and
are influenced by the three defined parameters. The study observes that in well-insulated
houses, the utilization of both the internal gains and the system losses is largely limited
due to the extremely reduced heating periods and the significantly reduced space heating
needs. The increasing internal gains often lead to a reduced recovery of the system losses,
and reduce the performance of the heating system. Moreover, the distribution losses due
to the DHW use increases outside the heating period and also negatively influences the
system performance. The research shows that the short-term random temporal variation
in the household’s loads, and in the internal gains and DHW use, have no noticeable impact
on the heating system performance, but does influence the building’s interaction with
the onsite renewable generation, as well as with the grid.
This thesis emphasis that neglecting the occupant-related diversity often leads to an unpredicted
operation of the energy supply system that is not well-understood and undesirable.
A good estimation of the occupants’ diversity is an important factor to correctly design
and size the overall heating system. The thesis further emphasizes that the performance of
a heating system in well-insulated buildings is strongly dependent on the sub-systems’ design
strategies. The study shows the influence of losses from the heat distribution system
on the total system performance. These losses can be reduced through proper planning,
sizing and placement strategy for the heat distribution systems during early design stage.
The research demonstrates that a net zero emission building can offer a large flexibility to the grid, using proper control strategies for the heating system. However, such strategies
often reduce the energy performance of the heating system, and considering their application
in the overall context is important.