# The State-of-the-Art of Sensors and Environmental Monitoring Technologies in Buildings
## 5 Discussion: Application, Challenges and Future Perspectives  
### Selection Parameters for Sensors and Communication Technologies in Buildings  
It is evident from our detailed review in Sections 2 and 3 that there is a plethora of sensing and communication technologies currently available on the market to cater for various requirements, and each one of them has its own respective sets of operating principles, characteristic features, and pros and cons. Whilst the arrangement, deployment costs, and other associated implementation challenges of sensor networks for different building applications may vary significantly based on variable factors such as location, size of building, number of devices and preferred technologies, they share an extensive set of common issues. As a result, their selection forms a design space which can consist of at least 13 different critical parameters which must be taken into account. The following key parameters can act as a checklist for building stakeholders, such as designers, managers, owners and occupants, considering the acquisition of various sensing and communication technologies for their respective applications.  
1. Heterogeneity--a single device/technology or a heterogeneous group with varying properties and hierarchies.
2. Cost--purchasing, installation and maintenance.
3. Availability--readily available for installation and replacement when required.
4. Deployment--once, incremental or random.
5. Maintenance--monthly, quarterly, annually or maintenance-free.
6. Connectivity--continuous, occasional or sporadic.
7. Accuracy/Range--adequate accuracy and measurement/coverage range for desired application.
8. Security--vulnerability to any potential hacking/viruses/noise/interference.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Product ID** & **Harvesting Technology** & **Product Type** & **Manufacturer** & **Cost** \\ \hline ‘Aerial Switch’ & Photovoltaic & Turnkey product—HMI switch & NISSHA & POA \\ \hline S3001-D330 & Photovoltaic & \begin{tabular}{c} Turnkey product— \\ Temperature sensor \\ \end{tabular} & EnOcean & \$27 \\ \hline S3001-D320 & Photovoltaic & \begin{tabular}{c} Turnkey product— \\ contact sensor \\ \end{tabular} & EnOcean & \$30 \\ \hline EPACA & Photovoltaic & Turnkey product & EnOcean & n/a \\ \hline AEM40940 & RF & Power Management IC & E.PEAS & \$4 \\ \hline STM300 & n/a & Low-power transmitter module & EnOcean & \$26 \\ \hline PCT100 & RF via RFID (less than 10 m) & \begin{tabular}{c} Light and temperature \\ transmitter module \\ \end{tabular} & Powercast & \$83 \\ \hline PMG17-100 & Vibration-EM coil & Energy source & Perpetuum & POA \\ \hline APA 400M & Vibration-Piezo & Energy source & \begin{tabular}{c} Cedrat \\ Technologies \\ \end{tabular} & POA \\ \hline S233-H5 FR & Vibration-Piezo & Energy source & Made & \$140 \\ \hline HZ-14 & Thermoelectric (Seebeck) & Energy source & Hi-\(Z\) & \$11 \\ \hline CZ1 & Thermoelectric (Seebeck) & Energy source & Tellurex & \$12 \\ \hline PL-ENO-SET1 & Mechanical & Turnkey product—HMI switch & EnOcean & \$100 \\ \hline EH300 & \
\begin{tabular}{c} Any intermittent electric \\ source (0–500V AC/DC) \\ \end{tabular} & Energy source &
\begin{tabular}{c} Advanced \\ Linear \\ Devices \\ \end{tabular} & \$80 \\ \hline \hline \end{tabular}
\end{table}
Table 6: Comparison of various commercial energy harvesting solutions available for potential use in buildings.  
* Lifetime--a few hours, many months or several years.
* Power Consumption--low consumption to ensure long battery lifetimes, low energy bills etc.
* Reliability--susceptibility to any potential disconnections/loss of power during data acquisition/ storage/transmission.
* Ruggedness--suitability for indoor/outdoor environments.
* Portability--flexibility to adjust/move network if and when required.