User Manual

6
2 Basics
Ever greater demands placed on room conditions, as well as a growing awareness
of the need to reduce energy consumption, demand new forward-looking building
concepts. Thermally Activated Building Systems (TABS) is an innovative
technology that rises to the challenge.
Thermally activated building systems (i.e. typically the building structure) are
considered a targeted part of energy management to increase energy efficiency.
However, the rapidity of heat and cold transfer is deterred by the considerable
system inertia inherent in the thermal activation of a large mass. This must be
considered for control and when engineering TABS. Matching is dynamic in nature
throughout the entire daytime, nighttime cycle.
Heating and cooling using tube heat exchangers embedded in concrete
elements
The concrete floors are used for most TABS applications as the heat and cold
transfer system within the building. This is referred to as concrete core temperature
control. To this end, coils consisting of plastic or composite tubes are cast directly
in the concrete core of the slabs or floors. As most heat transfer takes place
through the ceiling and not the floor, the tubes are often fixed nearer to the
thermally effective ceiling surfaces (see Figure 2-1). The tubing systems form
closed water circuits used to heat or cool the concrete thermal mass. System
temperature differentials (i.e. the difference between flow and return temperatures)
can be held at minimum, due to the relatively large transfer area. The exposed
concrete surfaces provide a natural temperature adjustment to the adjoining
rooms.
The concrete floor absorbs excess heat and cools the room. The level of self-
regulation is quite high due to the low system temperature differential. This effect
lessens undesired under cooling or overheating of individual rooms within a TABS
zone. The high degree of thermal storage makes it possible to time-shift plant
operation. Auxiliary systems are required to provide individual room temperature
control within a TABS zone. A flow temperature approaching the room temperature
allows operators to efficiently heat, for example, using heat pumps.
Environmentally friendly sources of cooling energy include free cooling, re-cooling,
or ground water cooling..
Buildings featuring TABS have a high level of room comfort. This is achieved by
carefully initiating measures that are matched to one another consisting of the
following basic elements: very good heat and solar protection, sufficient thermal
building storage capacity, sealed exterior shell together with basic ventilation and
air exchange sufficient to ensure proper hygiene as well as heat recovery.
And of course, integrated engineering is extremely important to achieve continuous
levels of energy efficiency for the overall system.
Advantages
– As well heat delivery for heating as heat absorption for cooling takes occur by
the thermally activated building systems with their large transfer surfaces
– Low system temperature differentials (due to the large transfer surfaces).
– Efficient use of natural sources of energy: e.g. heating using heat pumps or
cooling from free cooling, re-cooling or ground water cooling.
– Time-shifted heat delivery and heat absorption by means of large thermal mass.
– Use of cooler outside air at night during the summer or operation of heat pumps
during periods when electrical tariffs are lower.