Enhancing Performance Of HVAC Systems
There is a misconception in the commercial controls and HVAC industry today that SCADA (Supervisory Control and Data Acquisition) systems are not applicable, nor are they cost effective in this marketplace...
HVAC (heating, ventilating and air conditioning) systems are used for controlled maintenance of indoor ambient characteristics in optimal manner, with regards to outdoor ambient characteristics. The objective of these systems is to achieve comfortable and pleasant sensation of people staying in the conditioned area. To accomplish the established requests, understanding of intensity and dynamics of thermal effects on objects, physical characteristics of objects and requirements for heating and Cooling energy is needed.
Climate chambers and chillers are the base elements of ventilating and conditioning system – where air is prepared to reach purity, temperature and humidity of air. It is accomplished by filtering, heating, cooling, mixing and wetting/drying of the air. In this article, l’ll discuss the basic elements (industrial climate chambers and chillers), working principles of HVAC systems with control and monitoring configurations based on PLC, and SCADA can perform at optimal efficiency and most effectively.
There is a misconception in the commercial controls and HVAC industry today that SCADA (Supervisory Control and Data Acquisition) systems are not applicable, nor are they cost effective in this marketplace. Typically, these systems come with a high price tag and feature rich technology, which for many of the smaller HVAC market applications, is truly not cost effective. But in the larger markets, such as high-rise office buildings and multiple building systems (including schools, colleges, data centres, and government facilities) they actually make more sense.
One of the most attractive financial features of these products is that they are supported by organisations that are truly ‘Systems Integrators.’ This is defined as an organisation whose sole purpose is their procurement and pursuit of new business and service work; whose success does not rely on a single vendor’s product. Instead, it is dependent on their employee talent pool and their technical ability to provide value-added features and application services to help their customers to be more productive.
How is this different from the typical HVAC system with DDC Controls? Unlike the traditional DDC system from any of the manufacturers, the SCADA systems truly empower the end users (owners). They have a choice on who performs services on those systems, based on quality and price, rather than being held captive to the proprietary systems of the past, where the tools and application databases were held by the manufacturer’s branch office or a single authorised representative.
The technology exists today to allow owners to have a truly open system in the same manner as the PC industry today allows us to purchase a PC from one vendor, an Ethernet card from a second, and printers and peripheral devices from others, and have them seamlessly interoperate using a common platform. SCADA systems provide a better environment to accomplish this than any of the HVAC manufacturers can, using their ‘Front End’ software.
If you take the time to analyse the features and power of these SCADA systems, you will realise that these systems are actually a perfect fit for these types of applications in the HVAC environment. These were never considered in the past since all DDC systems for the HVAC industry were strictly proprietary with custom code and protocols developed by the manufacturers from the controller level to the enterprise level as one system. There weren’t any opportunities for owners, nor integrators for that matter, to even consider looking into any type of driver development since there would certainly be nothing but resistance from the manufacturers, and perhaps ensuing legal action.
The industrial market has had open systems for over 20 years and all of the manufacturers develop products and services to complement these systems.
In many cases, it’s a specialty item that is developed using standard protocols – so that customers will welcome the opportunity to add this to their network. It was a common practice for integration companies to bid on projects for services against each other for the same customer over and over again, unlike the commercial controls industry where the contractor who won the first phase of a project typically ‘locked in’ the customer for a 10-15 year period.
This practice goes against our core values of what we believe in as individuals, owners of businesses. Our nation is one that awards us choices in everything we do, so it is a natural progression to provide for this in our Facility Management Systems. Today, contrary to what some companies would like you to believe, that means open systems utilising protocols such as BACnet, LonTalk, and Modbus on the device level, with SCADA Enterprise level systems at the top of the network architecture.
These systems are made handle a wide array of real-time data throughput while, at the same time, offering common database structures for alarming and historical data archiving. Because of this, it’s a natural progression to have an owner integrate accounting systems, automate work orders, order entry, security, and even point of sale systems into this architecture through the use of open database structures, which are already built-in.
In summary, owners of larger facilities as well as multiple building owners will surely benefit from the SCADA Systems once thought of as only for industrial process control. These systems have the speed and horsepower to accommodate all types of applications. It also allows the owner to take advantage of building an architecture that is ‘truly open’ and will provide the protocols, software, and hardware tools to offer choices on vendors, contractors, and service organisations. This must start at the design level. To guarantee that you will get what you paid for, partner with a Master Integrator before the project begins.
SCADA screen of air conditioning chamber...
Pleasant sensation of people residing in a certain area are provided by constant bringing of fresh air into that space, where at least three air exchanges within one hour are required. Fresh air, which is used for ventilation, is also a carrier of heat for local regulation of ambient temperatures in winter and summer conditions.
Ventilation with 100% fresh air is energy efficient only in case of realisation based on device equipped with feedback sensors of air temperature and humidity, especially at low outdoor air temperature. The air conditioner, in cooling mode, decreases humidity of inflowing air to make better condition in residing area during extreme summer temperatures. Implementation of HVAC system and efficiency evaluation need data about the degree and dynamics of thermal effects on objects, as well as insulation characteristics and needs for heating and cooling. The majority of modern commercial and public buildings are fully or partially air conditioned. Typically, there is central preparing of heating and cooling energy conveyed by water thermal exchangers for a particular area – and air systems for bringing fresh air conditioned in air chambers.
The main objective of an air conditioning system is to fulfill the requirements in terms of air quality (temperature, humidity and air purity degree) to create the comfort and suitable conditions for living and working in an air conditioned environment. This is achieved by a combination of basic air processing, different options for managing air and using the related elements of automation and control laws.
Chiller is a cooling device. It is a complex system of exceptional performance in terms of efficiency, especially the new series, which can be used by low ambient temperature throughout the year. They provide high reliability in housing, technological and industrial applications. Chillers are used in the ceramics industry, food industry, printing industry, machines for plastic injection and extrusion, shopping and business centres, sports facilities and so on.
These systems can operate in free-cooling mode, exploiting the temperature of the outside air for cooling water that is used. A special control valve turns a certain amount of the feedback water from the system. In this way, appropriate conditions of temperature of the outside air cool the water before its return, resulting in delayed activation of the cooling device.
Free–cooling control exploits the temperature of the outside air to assist in the cooling of the utility water. Special valve deviates a certain quantity of return water from the system. The favourable outside air temperature conditions thus cool the water prior to its return, and the activation of the cooling devices is therefore delayed. Free-cooling is envisaged for air/water units in internal free-cooling mode, that is, the free-cooling coil housed inside the unit near the condenser coil/coils, with which it shares the control of the condenser fan/fans.
A very important issue in the design of a system for building management, and therefore the management of HVAC systems, is the choice of communication protocols. The dilemma is whether to choose an open protocol or protocol with limited access. Previous experience shows the advantage of open protocols. Here again the question of what to choose arises: LonWorks (Local Operating Network) or BACnet (A Data Communication Protocol for Building Automation and Control Networks). The leading companies, which among other things, are engaged in the production of building management systems, such as Siemens, Honeywell, Invensys, Johnson and TAC are the main sponsors of LonWorks.
SCADA screen of chiller...
On the other hand, the BACnet is supported by ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers - Association of Engineers in America, dealing with issues related to HVAC systems). BACnet is a generally accepted world standard in building management systems.
Only a SCADA based system can offer a Multi-Sensor Based Occupancy Estimation Model for Supporting Demand Driven HVAC Operation.
A SCADA system performs four functions
1. Data acquisition
2. Networked data communication
3. Data presentation
These functions are performed by four kinds of SCADA components
1. Sensors (either Digital or Analog) and control relays that directly interface with the managed system.
2. Remote Telemetry Units (RTUs).
These are small computerised units deployed in the field at specific sites and locations. RTUs serve as local collection points for gathering reports from sensors and delivering commands to control relays.
3. SCADA master units. These are larger computer consoles that serve as the central processor for the SCADA system. Master units provide a human interface to the system and automatically regulate the managed system in response to sensor inputs.
4. The communications network that connects the SCADA master unit to the RTUs in the field.
SCADA: Widely used in power systems
The applications for SCADA keep increasing day after day.
Some of the applications are:
• Comprehensive operational planning and control
• Fuel resource scheduling
• Optimum power flow
• Network security
• Economic dispatch
• Demand based comfort control
Expected benefits of SCADA for power systems
• Improved quality of service
• Improved reliability
• Reduced operating costs
• Maintenance /expansion of customer base
• Ability to defer capacity addition projects
• High value service providers
• Improved information for engineering decision
• value added services
• Flexible billing option
• Improved customer information access
• Reduced system implementation costs
• Reduced manpower requirements
There are many objectives of SCADA system
• Improved overall System efficiency (capital & energy)
• Increased penetration energy sources including renewable energy sources
• Reduced energy requirements in both the Transmission and Generation
The exploit of modern materials and equipment with the implementation of appropriate algorithms, produce modern HVAC systems that belong to the ENERGY SAVING systems, i.e., systems with maximum performance, which save energy and protect the environment.
A system for monitoring and control provides management and visualisation of the object and display the current value of significant parameters in the form of appropriate tables and graphics, the acquisition of relevant data and archiving, statistical data processing, data transfer to distributed locations in the network, linking with other programs in real time (DDE, ODBC, OLE, etc.) and generating various reports.
AUTHOR CREDIT & PHOTOGRAPH
Dr. Omprakash G. Kulkarni
Scientist, Mentor, Adviser,
Technology Provider and
Renewable Energy and Others...