Active Thermal Mass Solutions
HVAC solutions using thermal mass
Thermal mass is a much more useful concept if the energy storage can be controlled. Thermal mass passively regulates temperatures due to the convective effect of air passively coming into contact with exposed surfaces. But, to be useful in the building environment, thermal mass must also be able to absorb and release heat at a rate roughly in step with a building’s daily heating and cooling cycle. Having lots of mass is not necessarily a good thing if it’s cool when the building requires heat or warm when you are looking to cool.
Active thermal mass therefore describes methods of being able to heat and cool the mass in a controlled manner. The two most common methods used are using air channels (see air based systems) and embedded water pipes (see water based systems) to change the thermal properties of the mass and consequently the building interior.
Active Thermal Mass
Active mass describes methods of heating and cooling the mass from within in a controlled manner
Temperature sensors can be embedded into the concrete or measure the air based temperature and connected to the buildings BMS (Building Management System). Control strategies can be programmed to suit the occupation pattern of the building and passive or powered methods of heating or cooling can actively control the temperature of the thermal mass.
In practice the control strategy for buildings is to keep useful mass, such as a ceiling at a stable temperature. So during the summer the aim may be to keep the ceiling at 20 degree C and in the winter a little warmer at say 23 degree C. It should be kept in mind that concrete with a density of 2,372 KG/M3 has a huge capacity to store energy (796 J/KgK) which is extremely useful when for example it is absorbing unwanted heat gains during a working day. However, it uses energy to actively change the temperature of the mass and so even in active control strategies, the mass should be allowed to passively regulate temperatures where ever possible. This particularly often applies in spring and autumn seasons.
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For further information on thermal mass view concrete centre, termodeck.com, www.termodeck.com, mes, cibse journal, university east anglia website or strangbetong web site. Information on air handling, ventilation, heating, cooling, comfort, design teams, ductwork, sustainable systems, and low energy building design is available from. CIBSE, ASHRAE, Mitsubushi, Daikin, IES, or good architects, building services engineers, quantity surveyors, universities, structural engineersand hvac engineers.