By Alex Leonov

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Figure 1 – Wireless ZigBee/802.15.4
ZigBit RF Module with chip antenna

As energy costs continue to skyrocket and environmental concerns move to the forefront, running an energy efficient business becomes a mission critical practice that not only saves significant money, but also helps create a positive identity that attracts publicity and ongoing business.

Industrial facility CEO ’s dilemma
Sweden’s largest supplier of sports equipment, Rantzows Sport, AB, recognising the need for a streamlined solution to reducing energy consumption, decided to outsource its energy management to a specialist firm. Stefan Andersson, Rantzows’ CEO, set the straightforward goals: “Room temperature should be adjusted to a suitable and verified living climate, and what is not needed should be shut off.” For a sprawling industrial facility, however, this direct path to energy efficiency took on daunting new complexity. Implementing a building automation system was the clear solution, but achieving that end goal meant overcoming numerous challenges.

Going wireless
After being selected to manage this project, BFM – a Swedish-based innovative energy management company – immediately recognised obstacles to be overcome. Retrofitting the existing buildings with wires would be extremely expensive with the combined costs of running cables far exceeding $100 per metre. BFM’s expert assessment of the industrial facility revealed the need for a solution based on modules interconnected in a wireless network. Such a solution would allow all the benefits of local control functions and remote operation without the associated infrastructure costs.

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Figure 2 – Link2Web energy management
system’s components

In order to circumvent complications with the facility’s concrete walls, BFM envisioned a self-healing multihop mesh network, capable of rerouting a signal if line-ofsight was blocked. A 1-Wire interface was proposed to enable connection of different control signals at a low cost. Finally, to optimise network performance and stay consistent with the project’s energy efficient goals, BFM proposed battery operated wireless end-node devices, which would minimise the network’s power consumption. ZigBee, a global standard for the wireless sensor networking, based on IEEE 802.15.4, was the only one to meet the above requirements.

Selecting a ZigBee platform
The next step was to find a ZigBee platform that would enable the proposed design to be implemented cost efficiently and in a short time frame. ZigBee modules that simply need to be mounted on a PCB offered greater flexibility, time and cost savings during the design and prototyping phases than chipsets. Additionally, no RF expertise is required for ZigBee module implementation. The key selection criteria for the ZigBee modules were RF performance, power consumption and a form factor.

Having done extensive online research, BFM narrowed their search to a handful of ZigBee module vendors. MeshNetics’ ZigBit modules for 2.4 GHz and 868/915 MHz frequency bands topped the list. The sub-1 GHz module, the ZigBit 900, with its superior line of sight range of 6,000 m and excellent wall penetration capability, was a strong contender. However, for the project at hand, the 2.4 GHz ZigBit A2 proved to be the best choice. Its line-of-sight range of 300 m sufficed, while its integrated chip antenna allowed rapid design-in. ZigBit’s low power consumption and only 3 cm2 footprint helped fully meeting all BFM’s technology requirements. The fact that ZigBit modules come bundled with MeshNetics’ ZigBee PRO networking software, along with professional support for both hardware and software, further boosted BFM’s confidence in this choice.

Implementation
In order to create a complete building automation system using the internet as an operators’ platform, BFM used the following basic components, as shown in Figure 2:

  • NetControl – web server
  • XNet-Coordinator – ZigBit-based wireless sensor network (WSN) coordinator unit that uses RS-232 interface for communication and a 24 V AC power supply
  • XNet-Local Controller – ZigBitbased WSN controller unit that uses 1-Wire analogue interface and 24 V AC power supply
  • XNet-Endnode – ZigBit-based WSN end device that has 1-wire analogue interface and is 3 V battery powered.
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Table 1 - Annual energy savings

With these components, a complete over-the-internet energy management system for a district heating installation or an air handling unit can be implemented for US$ 3,000. The system was named “Link2Web”.

Next, BFM implemented ZigBit module-based control and sensor devices based on ZigBee ultra low power wireless networking technology with an embedded mesh networking stack software – forming a self-organising, self-healing sensor and control network. This embedded wireless communications approach achieves a high quality, cost effective system that is applicable to virtually any commercial building or industrial facility, while reducing startup and commissioning costs to nearly nothing.

Resulting savings
The entire Link2Web system was installed in an industrial building with a total heated area of 3,600 m2 holding one oil-fired boiler and nine air handling units (AHUs) with air heaters and recycling air control.

With the wireless sensor network in place, a webserver called TINI was employed to oversee the facility’s energy usage. Every ten minutes, all values collected by the ZigBit modules are sent to the TINI web server, which in turn channels the values over the internet to an SQL database. Operators connect to the database to read and change values. Each time the TINI webserver connects to the database, changed values are read and sent back to the local ZigBit-based controllers. In the industrial energy management facility, ZigBit uses this information – including data referencing both outside temperature and inside temperature – to precisely control the radiator temperature in a way that effectively realises the CEO’s initial vision: “Room temperature should be adjusted to a suitable and verified living climate, and what is not needed should be shut off.”

Leveraging in-depth, real time temperature and energy usage data, the BFM-designed ZigBee wireless sensor network optimised energy management – achieving a dramatic improvement in efficiency that translated to significant bottomline gains. For a total installation cost of $45,000, the Link2Web energy management system returned annual energy savings in the amount of $34,974 – nearly paying off itself over the course of a single year (Table 1).

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Figure 3 - Industrial facility with MeshNetics’
ZigBee module-based wireless
sensing solution

Now BFM offers an even easier alternative. An industrial facility or a commercial building can start using the Link2Web energy management system with no down payment. They can simply rent it for a fixed monthly fee and BFM will install and maintain the system for an agreed period of time.

The rental costs are as follows:Initial payment: $0
Monthly maintenance fee by L2W: $1,650
Total (per year): $19,800

In the case above, the value of the reduced energy consumption was $34,974. With the annual rental cost of $19,800 it would produce the immediate annual saving of $15,174.

It can be seen that ZigBee technology offers tremendous value in terms of energy conservation and bottom line benefits for building owners across any and all industries. Wasteful energy consumption is not what it used to be. Once merely an act of inattentiveness that held little consequence, gluttonous energy consumption practices now significantly impact the bottom line of both individuals and businesses. ZigBee-enabled smart energy products and solutions address these critical needs in an affordable and easy to implement way, and the ZigBee modules enable the development of such products and solutions on time and on budget.