INDUSTRY COMMENT
The stability of heat networks
Pete Mills, commercial technical operations manager at Bosch Commercial & Industrial, discussed what the future looks like
for heat networks and the options businesses have available to them to ensure energy security
Ask the Expert
The integration of lighting and HVAC control systems can help significantly reduce both installation and
commissioning costs. Will Darby, managing director of Carlo Gavazzi UK, outlines a simple way that this can be achieved
Currently, most heating, ventilation and air conditioning (HVAC) systems have their own dedicated controls network, as do most lighting systems. This is usually because HVAC is installed as part of the mechanical installation, while the lighting system is usually part of the electrical installation and so is often installed by a separate contractor. As a consequence, both HVAC systems and lighting systems often incorporate field control devices, such as presence detectors, potentially doubling up on those used in the HVAC system.
Is it possible to combine the two sets of controls? E
nergy security continues to be a major concern across Europe and is likely to be the case for some time to come. We are all facing a very uncertain and unsettling winter to come with many not having a precedent for such a situation in their lifetime. For the UK, energy security will need to draw on the natural assets of our islands, such as our dwindling natural gas and oil production, as well as our abundant wind
and tidal resources. Together with international energy supply agreements, this will start to shape the direction to travel. But energy security is also about reduction in demand and improving efficiency in the use of energy. There is great potential for the use of waste heat to give a boost to the efficient use of
energy. Energy from Waste (EfW) also has potential where it has a market to sell the heat into. This is where district heating and heat networks offer potential if they can be realised at scale.
What to expect from heat networks
Now, it must be said that the heat network industry in the UK is still at an adolescent age but is now on a clear path to maturity that will bring with it stability. Regulation of the industry is well underway within the Energy Bill that will usher in minimum technical standards. A regulator (OFGEM) provides consumer protection that will build on the success of the voluntary Heat Trust scheme.
Key to the adoption of heat networks at wider scale is how we can transition from individual communal or block schemes to wider district energy schemes that then provide a market to sell heat into. This is where heat network zones fit in, which are very much part of Government strategy for heat network development. Following on from the consultation round in Autumn 2021 looking at heat network zoning, the department for Business, Energy, and Industrial Strategy (BEIS) have moved on to pilot schemes across England. The pilot schemes involve 28 local authorities as partners in finding out how zoning could work within dense urban areas. The goal of heat network zones is to identify areas where they can provide the lowest cost low carbon heat to consumers compared with other decarbonisation routes. Ultimately for individual homes, there would be no immediate obligation to connect to a heat network if you happen to be within a zone, but for new developments and commercial buildings this is likely to be mandatory. Commercial buildings will act as important anchor loads to help the viability of heat network zones, particularly those that have significant heat demands. But of course, commercial buildings come in all shapes and sizes from a hairdresser needing hot water to a hospital with 24/7 heat demands. The applications may be quite different but the concept of getting your heat from a utility rather than producing it on site from a boiler is one that many owners of commercial buildings may be considering in the not-too-distant future. Dedicated heat network zones will not be the only places where commercial buildings will have the opportunity to buy heat. Examples such as Bristol and Glasgow where city wide district heating schemes are starting to develop, will want to pick up useful heat loads from commercial buildings that help spread the time-of-day usage patterns to even out demand profiles.
Switching things up
Transitioning from boiler-based systems to heat provided from a district energy scheme is not too difficult, although the general trend to lower temperature heating systems is still useful to keep in mind. In most cases a substation will take the place of a boiler, acting as a transition with hydraulic break from the main network to the building. For smaller commercial units, particularly those within a mixed development, this interface could be as simple as a heat interface unit (HIU) that might be found within a domestic apartment. Typically, the existing space provided for a boiler will be appropriate for a substation or HIU with necessary adaptations for the pipework. The Bristol guidance documents for their district heating schemes provide a useful resource to see how this is done. Heating our commercial buildings in the future through heat network zones of course will not be available to all, but where they become an option, they will provide a useful alternative that will be cost effective and help the overall efficiency of our energy system.
If a scheme’s HVAC and lighting engineers talked to each other, it would become apparent that there are opportunities to share sensors and to reduce the amount of control wiring using a field bus system. Carlo Gavazzi’s Dupline field and installation bus, for example, can provide a simple solution to integrating both lighting and HVAC control systems in a simple cost-effective solution.
What are the benefits to be had from combining the two sets of controls?
Dupline allows the sharing of hardware and control wiring, reducing capital and installation costs with the added benefit of enabling both control systems to work as one. A major advantage of Dupline technology is that it offers completely free topology allowing the two-wire cable to be routed in any configuration: line, ring or star or as a combination of these.
In addition, many Dupline sensors and I/O-modules are bus-powered without the need for local power. Cabling is simply a matter of dropping the same two-wire bus from module to module regardless of whether that module is serving the HVAC or lighting system (or both), eliminating the need for two separate networks. To help speed up the commissioning process, all Dupline devices are discoverable over the Dupline network, so there is no need to manually assign individual IDs. In the same way the entire Dupline network is discoverable via BACnet over IP by the BMS controller or supervisor.
How is the system linked to the BMS?
At the heart of the Dupline system is the UWP 3.0 controller. This provides a gateway function between the Dupline network and the building automation network. A Carlo Gavazzi DALI master provides the link from Dupline to the lighting DALI drivers, while other lighting loads can be controlled directly by means of Dupline relays or power dimmers. The programming of the entire system is simple, with addressing, grouping and functions setup carried out in a single PC-based configuration tool with seamless integration of data points from Dupline, DALI and BACnet/IP. Furthermore, it is easy to interface with Carlo Gavazzi’s broad range of energy meters
thereby allowing energy usage data to be included alongside the HVAC and lighting control systems for a complete solution. To find out more about Carlo Gavazzi’s Dupline go to
www.carlogavazzi.co.uk.
Read the latest at:
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BUILDING SERVICES & ENVIRONMENTAL ENGINEER NOVEMBER 2022 9
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