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Concrete Core Cooling

All structures are subject to heat gains and losses due to a number of factors.

Internal gains:

  • Lights
  • People
  • Machines
  • Solar radiation entering the space through glazing

External gains appear from solar radiation on the building fabric and transmission gains and losses due to the temperature difference between inside and outside.

To a certain extent, the walls and ceilings of a building act as natural storage vehicle to moderate the effect of the loads. This phenomenon can be seen for example in older buildings such as churches where due to the thickness of the walls, even on a warm summer’s day a feeling of coolness can be experienced, in part due to the effect of night cooling stored within the structure.

Modern buildings, however, are so well insulated and sealed from the outdoor environment that little overnight cooling takes place unless this is achieved by a night time ventilation cycle. Such cycles are dependent on many factors and as such are extremely unpredictable.

Therefore, the traditional method for dealing with these gains and losses in modern structures is to size the heating/cooling plant according to the peak design load.

The reality is that sizing for these peak loads leads to over-sized equipment, often operating inefficiently at part load.

Concrete Core Tempering Systems utilise the storage capability of the buildings concrete mass to absorb energy and hence “soften” these peak loads thereby enabling smaller more efficient equipment to be utilised. As a consequence, the overall system capital costs and subsequently the operating costs are substantially reduced. The key added benefit being that since the system operates overnight using the most efficient generating plant, building CO² Emissions can be reduced in excess of 10%.

Concrete has a volumetric thermal capacity comparable to that of water. For example, if the temperature of a 140 mm thick layer of concrete is varied by 2K, this is equivalent to a heat or cold storage capacity of around 190 Wh/m2 or alternatively expressed as an output of 23.5 W/m2 for 8 hours.

Today, concrete core cooling systems are taking on a new relevance in the market place as they are well placed to compliment the use of low CO2 alternative electricty generators such a s wind and wave power.

Control

Typically design requirements have been rigidly specified to have specific room temperature that will be different for both cooling and heating and a tolerance in the order of ±1 or 2°C. Apart from the fact that determining when the system should be changed over to be controlled for either a heating or cooling is totally impractical, research work shows clearly that not only should internal conditions be variable related to outdoor temperature, but that there is a range of temperatures that will provide the highest level of acceptability.

The comfort chart according to DIN1946 Part 2, for example, shows that there is a range of temperature combinations that will provide an acceptable percentage of occupants in a “comfortable” environment.

DIN1946 comfort graph

Clearly, rigid levels of control should be relative only to production processes and not spaces occupied only by human beings.

LTi have considerable experience in the application of thermal storage and are able to offer two alternative solutions to take advantage of the thermal storage capacity of the buildings concrete ceilings:

  • BATISO – Water Based Concrete Core Cooling
  • CONCRETCOOL – Air Based Concrete Core Cooling

The choice of which system to choose will depend upon the constraints of the building and the site location. LTi are able to advise on all aspects of applying the system.

In the event that the building is either existing or of unsuitable construction for an integrated system, similar benefits can be achieved by the addition of an Ice Thermal Storage Solution.