This new EMA Energy Managers’ guide has been designed with Ecopilot (UK) Ltd to offer some basic information and guidance on understanding thermal storage, how it works within buildings and what the common misperceptions are when accessing buildings’ thermal inertia.
The vast majority of buildings are thermally inert by nature. This means that a building’s framework has a self-regulating ability to maintain the correct temperature – but is this being utilised by the buildings’ managers?
Most control and regulating systems currently in use are set to instantly compensate for each temperature variation that occurs in a building. As a result, the installed systems are forced to work against the natural self-regulation, which leads to the waste of both cooling and heating capacity.
An example of this would be early in the day, following a night set back or system shutdown when the internal air temperature and external temperature are cooler. With a standard control strategy, the temperature measured by the return or extract air temperature sensor would increase the duty requirement of the supply air, modulating the heating valve to the heating coil open to reach the required space temperature set point.
During the course of the day, the outdoor temperature rises and therefore the external temperature influence on the building increases. The effect of this is that the temperature internally increases therefore the duty requirement of the heating to the supply air is reduced, eventually reaching equilibrium and the heating valve is closed. Should the external and internal temperature influences surpass the equilibrium point, the valve to the cooling coil would be modulated open to reach the set point of the space temperature.
The result of this would be that the building would have been heated and cooled within the space of one day, requiring energy input to both systems. With a more intelligent and long term control strategy taking into account the internal and external influences this could certainly be avoided.
Varieties of systems that optimise buildings with regard to a building’s natural thermal inertia are available on the market today. Measured reductions in energy consumption of 20–40% (from the 500+ installations already carried out) for heating and cooling of buildings are common after installation. Pay-off times for the systems normally appear to be approx. 2–5 years. The interesting thing is that these results are achieved by letting a building’s technical installations work with the laws of nature to store the free heat and cold that would otherwise have been “discarded”. If you manage properties with modern computerized BMS systems (no older than approx. 10 years), a system that works with a building’s inertia could be one of the most viable measures to install in the property that you manage.
Research in the field and barriers for take up in the past
As early as the 1970s, research results from the Royal Institute of Technology (KTH) in Stockholm showed the importance of adopting a holistic view and taking advantage of a building framework’s thermodynamic properties.
The basic idea involves utilising the heat, for example from machines and people, which is stored in the framework of the building. Actually, controls and regulating technology only need to observe the temperature curves and intervene when necessary. The secret was said to be the ability to do this in a controlled manner without negatively affecting the indoor climate.
Way forward – control strategy that takes account of the buildings’ thermal inertia