Building Energy Management Systems(BEMS)have been a major success story in UK commercial buildings over the last 20 years.They combine energy saving control techniques,such as optimum start and dead bands,with communication and information systems that allow active management of the building services and the capability to achieve and maintain a high level of energy efficiency.However,in far too many buildings this technology is too complex for users to understand and maintain.As a result,many systems have fallen into disuse.At a time when energy costs for many organisations are spiralling upwards,a situation where the plant is permanently running in hand will have a disastrous effect on the energy efficiency of many buildings today. Many of the issues with programmable BEMS arise first in the control strategy.Energy efficient control strategies,such as,optimum start, close control of temperatures,plant sequencing,etc,are typically available with all BEMS.Yet,rarely is it specified where and when these application techniques should be used.The system’s installer will not spend any more time programming and commissioning a BEMS than is absolutely necessary,with the result that a simpler,less efficient solution is often implemented. This approach also breeds inconsistency,since the same plant will not necessarily be programmed to control in the same way between different installations.In comparison,the standardised modular controls approach offers clear advantages.
These modern types of HVAC control system,such as the SeaChange system from SC Controls,are built up from a number of application specific,demand-driven,self learning and self tuning modules,with preconfigured strategies already embedded,so avoiding the need for programming.As a result,the fixed function modules have the advantage of knowing intrinsically the input/output points,the maximum heating/cooling demand per Zone/Wing,the distribution logic for heating and cooling demands and the control strategy;all are inherent within the particular plant modules e.g.the boiler controller,air handling unit controller,fan coil controller,etc.
These built-in module features eliminate any chance of mis- interpretation,and so the need to prepare such a detailed controls specification for the installer to follow in the first place.As the Energy Management feature is designed into the fixed strategy,it ensures that the demand driven system only operates when required and at a level sufficient to satisfy the energy demand from the zone. Furthermore,the fixed function modules provide a means of standardising the controls where repeat performance and consistency is the key factor.In this scenario,a SeaChange control system is the perfect solution.
As well as reducing the time and cost of control system design and engineering,these distributed modules can be housed in modular-style, smartbox panels.Such panels are more compact and much more cost- effective than the expensive and time consuming-to-build cabinets which are typically home to controllers in a conventional BEMS system.They are also a particularly attractive option on retrofit applications,where allocating sufficient space for the control cabinets where none existed before is frequently a major issue.
At the same time,these plug and play type control modules are incredibly versatile. They can be easily connected together via an Echelon LONWORKS communications network to form a sophisticated building or site wide control system.A networked system can provide the correct level of control for all types and any combination of commercial building HVAC plant,including energy efficient,modulating condensing boilers,natural ventilation systems as well as all types of air handling plant and airconditioning system.They also offer a range of added value energy efficiency benefits.These fixed function modules are the only HVAC controls technology listed by the Carbon Trust under the Government’s Enhanced Capital Allowances scheme. Traditional BEMS systems cannot and do not carry this approval and are therefore excluded from the financial incentives offered by the scheme.Pulse counting and dedicated monitoring modules are also available within the range to assist in the effective implementation of automatic monitoring,targeting and energy management strategies. In fact,in this increasingly important area of energy monitoring and management,modular controls are much more practical,cost effective and easy to use than a traditional BEMS.In theory,the information side of the BEMS can be used to check whether the design criteria are being met or if the system is over capacity and can be better matched to the building by modifying its operating parameters.For example,if boiler plant is oversized,can units be taken off line?Is the max flow temperature too high? Are the flow rates of water and air too high and can the motor speed be adjusted to run slower?Most buildings do not run as designed,so there are often important energy savings which can be made from checking how the system is working.
Understanding the issues involved and making the right decisions in this area requires the expertise of commissioning engineers,the consultant who designed the services in the first place or specialist maintenance.Extra work not only involves extra cost,but also,in a sector where the skill sets,especially in maintenance,are diminishing it is not a desirable position for the building owner or its occupiers to hold.Also,BEMS systems rely for their integrity and maintainability on copious documentation /software disks etc being carefully retained and updated by the client for the lifetime of the building – in practice,this rarely happens.On the other hand,with an auto-configuring controls approach which is self-tuning,self documenting and where no specialist programming is required,the performance and consistency of a modular controls system is guaranteed,irrespective of the engineer’s available skills, documentation integrity or the expensive re-programming that an ordinary BEMS would typically need to accommodate these changes.
21st century modular solutions are also at the forefront of the revolution in control system accessibility,helping to improve the efficiency of the engineering,operating and maintenance teams. Communication with the control system can take place through an Ethernet connection on any valid TCP/IP network e.g.LAN,WAN,radio LAN or internet thanks to devices,such as,the SeaChange smartserver. Unlike traditional BEMS supervisory systems,this technology allows any PC with a standard browser on the network to gain access to an automatically generated,site-specific picture of the control system without the supervisor software or graphics pages having to be installed or copied onto every single machine.Simultaneous access can be achieved from multiple PC’s with different levels of service set up to suit the requirements of high priority and low priority users. Another product from SC Controls is the smartEinterface which is the ideal solution for distributed or ‘campus style’ sites where communication with SeaChange controls in self contained plantrooms are provided via the client’s existing IT network using a supervisory software. This method enables both the client and the maintenance team to access the systems from multiple PCs on site.
Considering how the building user and maintainer interact with the system is indeed critical to the success of the HVAC control system. Before BEMS systems, buildings had stand-alone controls that could be manually set - typified by a thermostat and time clock.
Building users tended to misuse these controls and set them to work longer or hotter once,but forgot to set them back to the energy efficient levels again later.
BEMS systems originally replaced these local controls with units that could only be adjusted through a central system located on site or remotely at some central facility.However,this centralisation of control and authority is not necessarily a good thing as it discourages flexibility and out of hours working.Today’s modular control systems allow users a degree of local interaction with the system via easy to operate wall-mounted zone controllers,located in their workspace.The user can easily extend times for today or change the temperature within limits but the next day these changes are lost and the system automatically reverts to the energy efficient,default settings.The important issue is to ensure that local access is simple and appropriate so people can use the system to make the basic changes to times of use and temperatures that they reasonably require.Intelligent controls are potentially powerful tools to help achieve
high levels of energy efficiency from the available plant and building.In expert hands,the information that BEMS provide can be used to measure energy performance levels and to diagnose plant performance and indicate how to optimise its efficiency.
However,the key here is the expertise of the system user or maintainer. Without the expertise the systems cannot deliver the additional performance benefits.Worse than that,systems that cannot be properly operated or maintained,can fall into total disuse and fail to give even basic performance and energy management benefits. The alternative approach of fixed function control modules brings real flexibility to the market,allowing system installers,endusers and maintainers to benefit.They offer the simplicity of a stand-alone control system but the capability of a complex BMS,with the added advantage that the system can be easily expanded or changed at any time,without huge re-programming or reengineering expense.They can also collect important energy consumption data,monitoring usage and performance to maximise service efficiency.Over a building’s lifetime,installation of this form of controls technology provides undeniably the greatest potential for saving energy and cost.
Navid Mehr is Managing Director at SC Controls-the company behind the SeaChange brand of control systems.
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There is an obvious need for the industry to be more energy efficient and pay more attention to the ways in which energy is both used and wasted. Do you think we have the products on the market to meet our needs?
