HEATING, VENTILATION AND AIR-CONDITIONING SYSTEMS (HVAC)
The HVAC system is a very important system at home, not only in terms of comfort, but also in terms of the impact in energy consumption.
In this sense, special controlling strategies should be envisaged to be sure that a certain level of comfort will be reached using the less possible energy (or the less expensive amount of energy, if we want to emphasize the economic impact, or the less environmental-aggressive amount of energy, if we want to emphasize environment defense).
In this sense, it is important to consider different aspects for the HVAC system, including the different sources of energy, from solar to eolic, not excluding storage of energy within hot water, for instance.
The HVAC system should support both heating and cooling, which can be accomplished for several technologies using the same equipment in a reverse way.
It has to be noted that the comfort is a psychological concept, commonly associated with temperature. Although, comfort is mostly determined by temperature and relative humidity. This means that we should consider also humidity sensors within the strategy for HVAC control (it has to be noted that most of HVAC equipments fail to do that).
Another feature to be considered by the HVAC systems is related with the renovation of air, to be sure of an adequate composition of air.
Among common features that most users would like to have available in HVAC systems we can mention the following ones:
- Remote activation/deactivation of HVAC systems; this can be accomplished through internet, telephone or through GSM connection;
- Automatic procedures associated with specific scenarios (for example, when the user arrive at home, or when all users left home);
- Possibility of having automatic procedures according with the season year and day of week;
- Possibility of having individual control for different parts of the house.
ELEMENTS OF ACCESS-CONTROL, SECURITY AND SAFETY SYSTEM
The area of access control, security and safety systems can benefit a lot of the current level of technological support, contributing to better levels of security and comfort.
Among common features that most users would like to have available in these types of systems we can mention the following ones:
- Intrusion detection per specific area;
- Image recording supported by digital image processing;
- Access control based on smart cards and complemented by biometric information;
- Remote access to the CCTV (closed-circuit television) surveillance system, based on internet technologies;
- Presence simulation, allowing learning of simulated user behaviour;
- Fire, flow, and gas detections; after reception of alarm adequate procedures can be carried out, for instance closing/switching off water, electric energy or gas supply, accordingly.
The referred desirable features for this group of systems, should be supported by internal communications networks (addressed in a different chapter), which should include wireless connectivity, and connection to the outside world using telephone network, internet, ISDN, ADSL and/or GSM.
In what concerns with the intrusion detection system, it can be supported by:
- Magnetic sensors using Reed contacts, installed in every windows and doors;
- Movement detectors and curtain detectors (based on infrared sensors);
- Water level detectors;
- Fire and smog detectors;
- Gas detectors;
- Self-powered buzzers to be activated in case of alarm situation.
After the acknowledge of an alarm situation, the system should take advantage of the communication infrastructure to issue the alarm via GSM, phone or other media, and to take specific corrective procedures in cooperation with the other installed systems, namely the lighting management system and other automation control systems.
Next system to consider is the closed-circuit television system (CCTV). The name is referred due to historical reasons, when the system was based on the internal wiring using coax cable of a set of cameras to a central location with specific equipments for visualization and storage of images.
Nowadays, the concept of image surveillance is more open, and it is common to look for a camera just like a dedicated computer with specific boards for image and sound acquisition and transmission through the internet.
In this sense, it is possible to build dedicated networks of cameras, with movement capabilities (like in a dome pan & tilt camera), which can still be visualised in dedicated equipments but the evolution is to use an ordinary PC or a television to have access to images of the surveillance system.
Regarding the access control, several flexible and powerful technologies are available and ready to be used. Common user interface include a keypad or a card reader, complemented by a specific sensor for biometric feature grabbing, namely image acquisition. After acknowledge of a presence at the entrance several procedures can be carried out, including:
- Presentation of the acquired image in the internal television circuit or sending it through GPRS or other media;
- Interaction with the other home systems allowing the activation of specific scenarios of lighting, sound, temperature, and so on…
In the following sections, several technologies available for access control support will be presented, namely bar coding, ID cards, and biometric identification.