Zeroth Energy System: connecting ambient loops and higher temperature district heat networks

Why more developments are connecting the Zeroth Energy System to a district heating network

The tightening timescales for reaching the 2050 net-zero carbon target require us to accelerate our efforts towards the decarbonisation of heat. Ambient network systems, such as the Zeroth Energy System by Glen Dimplex Heating and Ventilation (GDHV), are being increasingly specified for multi-occupancy developments because of their high efficiency and capability to reduce a building’s CO2 emissions. This raises the questions: can the Zeroth Energy System be specified in a district heating priority area, and can it connect to the district heating network?

The Zeroth Energy System has been successfully installed in developments across the UK, both within and outside Greater London. One of the first installations under the Greater London Authority (GLA) was the Church Road development by Galliard Homes. Along with projects such as Harbour Lofts in Poole developed by Acorn Properties and The Factory by Dundonald Church in London, it has been shown that ambient networks can help achieve compliance for complex projects and deliver high energy efficiency for a variety of building types.

The Zeroth Energy System has now been specified for a large number of diverse projects across the UK that are either completed or currently under construction.

It follows that combining the benefits of ambient networks and those of district heating could offer efficiency improvements to many residential developments. To answer the questions of connecting the Zeroth Energy System into district heating networks and the benefits of such a connection, we should have a look at the methodology behind both technologies first.

The rising popularity of district heating networks
Heat networks are not a new concept. Modern third-generation district heating networks have been deployed in Scandinavia for more than half a century, and their benefits for occupiers, developers and the environment have been well documented.

In response to climate change, the UK government and many local authorities have shown support for increasing the use of heat networks, especially in high-density areas. For example, London has been very vocal with plans to deliver 25% of its energy through large-scale heat transmission networks as a way to reduce carbon emissions and support a low carbon economy.

Behind this support of large-scale networks is the wide range of benefits they can offer – the use of diverse fuel sources, utilisation of energy from waste heat, help with balancing energy distribution and delivery of cost-effective low carbon heat can lead to reduced energy bills, local economy growth and a flexible and stable energy system.

The UK government and many local authorities have shown support for increasing the use of heat networks, especially in high-density areas

There is however a common misconception that a high-temperature heat network must (at building level) be paired with a high-temperature communal heating system. This is simply not the case, as the system operating temperature can be adjusted, as we will discuss later.

Importantly, the major drawback of adopting traditional high-temperature communal heating technologies in modern buildings with increasingly thermally efficient building envelopes is the heat loss, which results in reduced efficiency.

Heat-loss factors are not only indicators of system efficiency, they also directly impact the comfort levels of the occupants. In a modern, thermally-efficient building, heat loss from the distribution pipework can cause overheating of service risers, corridors and apartments.

The Zeroth Energy System and the efficiency of the ambient loop
The Zeroth Energy System is a low carbon solution designed with cooperation and feedback from construction industry experts and BRE to address the challenges of distribution heat loss by using heat pump technology while aligning with compliance.

The network of in-apartment water-to-water heat pumps is connected to an ambient loop operating at 25°C, and can provide heating and hot water, or heating, cooling and hot water using the same infrastructure without the need for a refrigerant.

The thermal energy can come from a renewable central plant – for example, air-source heat pumps – including those from a district heat network. The unvented 172L cylinder within each unit can provide hot water up to 60°C and, if comfort cooling is required, the system can transfer the waste energy from the heating process.

Conversely, the waste energy from the cooling process can be transferred to the water cylinder to provide the thermal energy for hot water delivery.

Modelling in SAP 2012 shows that the efficiency of the system, when used with an air-source heat pump, reaches 300%, with a heat loss reduction of 90% compared with traditional high-temperature systems.

Connecting to a district heating network
If you would like to benefit from a communal ambient loop but are wondering if this could connect to a higher temperature district heat network, then the answer is simple: yes.

Hydronic design connection to a district heating network can be achieved without major alteration to the system infrastructure. A spur would be required from the network into the building plantroom. This would be connected to a plate heat exchanger to blend the temperature down to circa 25-40°C where it would be stored in a buffer.

This would be blended again into the building’s ambient loop at 25°C to feed each apartment. In principle, the air-source heat pump we so often see specified with Zeroth Energy Systems would be replaced with a spur to the district heat network.

Although the Zeroth Energy System is a relatively new solution, the technology is already up and running. Currently, more than 120 projects in various stages of construction are considering the Zeroth Energy System – albeit, a large percentage do not require a connection to a district heating network, although they do utilise an air-source heat pump as a central plant.

Replacing traditional high-temperature systems that can suffer drops of efficiency to as low as 33% though distribution heat loss with an ambient loop communal system can result in a reduction of heat loss by 90% in a building. This leads to healthier buildings and increased energy efficiency.

Connecting an ambient network such as the Zeroth Energy System into a district heating network also unlocks all the additional benefits such networks have to offer. This provides the freedom to build well-designed, comfortable and healthy buildings for the future.

To find out more information on the Zeroth Energy System, or to discuss how your project could benefit from an ambient loop system, please contact our team of specialists.