## 2 Concept and Benefits
### The Setpoint Deviation Events  
The event essentially tracks space overheating or overcooling. It is triggered as soon as the space temperature is higher in wintertime or lower in the summertime of the specified setpoint (SP) plus the programmed slack value (e.g., 2 \({}^{\circ}\)C). In its simplest form, the event power will depend on the deviation between the space temperature and the setpoint (\(\rm T_{actual}-T_{setpoint}\)); the waste energy can then be expressed as \"degrees \(\times\) time\". Alternatively, if the HVAC energy power of the space can be metered, the energy power/waste can also be directly expressed in terms of kW/kWh. In principle, the availability of such space energy meters may be rather unlikely. Thus, for reasons of practicality, in the following analysis we preferred to use a simplified indicator of power of this event in terms of the above noted temperature difference and of the waste of it in terms of the same temperature difference integrated over time.  
A more accurate form of the event takes account also of the outdoor temperature. Especially in spring and autumn one cannot be certain about the actual situation unless an outdoor temperature metering is taken into consideration. For example, in June (when a setpoint of 24 \({}^{\circ}\)C and a slack of 2 \({}^{\circ}\)C may apply) an indoor temperature of 20 \({}^{\circ}\)C might erroneously be considered as an over-cooling incident although the outdoor temperature may be only 20 \({}^{\circ}\)C.  
The following Table 2 shows exactly how the event power (temperature deviation) is modelled, taking into account also the outdoor conditions.  
This event can be extended to also include presence considerations. It will again be triggered as soon as the space temperature is higher in the wintertime or lower in the summertime of the specified setpoint (SP) plus slack. The main difference now is that the event takes account of the presence and adjusts dynamically this SP. Multiple SP thermostats are more and more used; should they sense no presence in a space for a given time (short absence) they reduce the SP (winter case). If the no presence situation carries on for a given period they may be further reduced to an even lower value (long absence). As soon as presence is identified, the SP is restored to the higher value and if it persists for a given time it assumes its initial value.  
This event, in fact, simulates the impact of a 3-level thermostat and predicts the economies the installation of such a device would potentially result in. In this case, we would also need real-time presence sensing. In addition, besides the normal SP, one also needs to set the short/long absence SPs.  
Besides the core functionality, there can also be several more benefits resulting from the use of BME. These are all highlighted in Table 3 below.  
\begin{table}
\begin{tabular}{c c} \hline
**Winter** & **Summer** \\ \hline T(out) * \(<\) T(SPw) * : DT = T(in) * - T(SPw) * & T(out) * \(>\) T(SPs) * : DT = T(SPs) * - T(in) * \\ T(SPw) * \(<\) T(out) * \(<\) T(SPs) * : DT = T(in) * - T(out) * & T(SPw) * \(<\) T(out) * \(<\) T(SPs) * : DT = T(out) - T(in)* \\ T(out) * \(>\) T(SPs) * : DT = 0 & T(in) * \(<\) T(SPw) * : DT = 0 \\ \hline \end{tabular}  
* SPw = winter setpoint, SPs = summer setpoints, Tin = indoor temperature, Tout = outdoor temperature.  
\end{table}
Table 2: Deviation Calculation *.