Nowadays transparent buildings with enormous glazing and extreme high internal loads by electric equipment are spread all over the globe. Even on the northern part these skyscrapers suffer more and more from over heating in summer. The precise cooling load calculation with accurate data is mendetory for modern and confortable buildings.
Constructional requirements for office buildings
Unlike the specification consideration given by individual technical disciplines, with their various procedures and approaches, the integral planning by the architect and the structural and building-services engineers allows to identify the various quantities of influence contributed by the design, the load-bearing (Tragwerksplanung) structure and the building-service systems and to take them into account in one combined concept. By early construction and subdivision of the technical systems can be arranged in a way to achieve a significant reduction in energy demand using optimised system solutions.
It must, therefore, be the aim:
- To design buildings and rooms in a way meeting both current and future requirements,
- To balance structural, technical and energy-management issues and
- To implement building-service concepts that are meeting the occupants’ requirements (comfortable, healthy, convenient).
Site of the building/premises
In selecting the building site and the premises, energy-relevant aspects shall be considered and assessed particularly. Important quantities of influence are:
- Site and topography (climate and radiation data)
- Building-law requirements and restrictions
- Consideration of the typical architecture in a given environment and landscape
- Supply and disposal facilities
- Environmental impacts, e.g. air pollutants (outdoor-air quality), noise, wind etc.
Cooling load simulation is a must for modern buildings
The calculation procedure is applicable to rooms for which temperature requirements must be complied with in the case of thermal loads, and humidity requirements in the case of humidity loads.
An important initial design calculation applies here for the case of constant room air temperature (22°C) and quasi steady state condition under periodic daily load variations. The term used in relation to this is reference cooling load Q (basic cooling load), and it is recommended that this reference cooling load always be calculated as basic data, regardless of the actual required boundary conditions.
Figure 1 Izmir Turkey, skyscraper view from the ferry
For rooms which need to be air-conditioned in zones because of considerable differences in local loads, the calculation should be carried out separately for the individual zones (computer method).
The precise data of local solar radiation is very important for the cooling load. The simulation calculates the temperature for each room considering the wall materials and windows. The materials capacity to store temperatures is taken into account. The orientation and surface of the windows give the total heat load by the sun.
The results give each room a cooling load dependant on the number of persons and there usage of electrical equipment during the day. This leads to air flow rates which are cooled in central ventilation units.
The lower energy consumption of those unit in comparison with split systems makes building owner pay less and the users are satisfied by constant temperatures and good work efficiency for the directors.
Figure graph of the highest cooling load
The calculation data given here are focussed to Central European conditions, i.e. with solar radiation at 50° latitude, true local time (solar time) and the mean atmospheric turbidities occurring here, insofar as they refer to external thermal load, i.e. the cooling load fraction which is due to climatological conditions.
(The potentially considerable temporal deviation in relation to Central European summer time (MESZ – mitteleuripäische Sommerzeit) should be taken in consideration).