The alpha and omega of successful heat networks is having a good demand profile. However many secondary heat networks are not in a fit state to provide this for connecting to the primary main. But they can be fixed.
In many cases heat mapping, master planning studies and even the techno-economic analysis will assume the newly constructed primary network will be tapped into by existing secondary networks in nearby buildings, replacing communal plant rooms with a heat interface unit onto the main network, thereby creating an instant demand.
Ignoring the intricacies of the associated commercial arrangement for the time being, how the secondary network performs in reality is crucial. Often these networks are not in good shape, primarily due to an historic lack of regulation. Heat network developers are starting to wake up to a hidden issue that has been plaguing housing on communal heating systems for decades; these systems need fixing.
In 2016 the Department for Business, Energy and Industrial Strategy (BEIS) issued a ‘Guidance on Economic and Financial Cases for Heat Networks’* report. The risk analysis contained within the document is at Code Red for connecting primary and secondary networks, meaning it’s one of the few areas identified as being ‘High’ in the all three risk categories of impact, severity and probability.
The report outlines some key steps to take in order to anticipate potential connectivity issues between primary (district network) and secondary (existing buildings) circuits and ensure that the building demand and performance are modelled correctly.
- Identify buildings looking to connect to the district network.
- Estimate initial cost of connection based on optimal secondary network performance.
- Review and validate the actual operational performance of the existing system reviewing factors such as age, condition, control methodologies and network losses.
- Account for costs required to improve the building network performance such as improved insulation and recommissioning the system in order for the network to operate at an optimal flow/return ΔT.
Poor compatibility is an issue also experienced on communal heating networks when newly upgraded heating plant is connected to existing distribution systems which can often be 40+ years old.
Where this is the case it is essential that a thorough review of the level of corrosion in the existing distribution pipework is carried out. This will help to determine if it is necessary to separate primary (boiler plant) and secondary (distribution) circuits via a plate heat exchanger to prevent contamination of the newly upgraded plant.
It is also important to understand the impact that scale and corrosion in older distribution pipework can have on overall network performance. Relying solely on theoretical data when calculating heating loads and subsequently sizing replacement systems is risky and where available, operational data should be accounted for in calculations.
The recently introduced Heat Network (Metering and Billing) Regulations stipulate that building level meters are now mandatory on all existing district networks where the building contains more than one final customer, with more granular network metering (down to individual tenant level) required for new buildings connected to district networks. The importance of the operational insight that network metering provides, certainly shouldn’t be underestimated.
At Sustain our engineers have significant experience of reviewing network performance via our Heat Network Health Checks. We make use of the latest portable metering technology to better understand real-time operational performance of heat networks which allows us to provide recommendations to improve network efficiency.
If you are currently operating a communal or district network or considering new connections and are concerned about system performance, we would be more than happy to provide our support and expertise. Please get in touch by calling 0117 403 2700 or emailing firstname.lastname@example.org.
* Heat Network Detailed Project Development Resource: Guide on Economic and Financial Case – Development of the Financial Model, Heat Pricing and Maximising Opportunities DECC, Grant Thornton, AECOM, July 2016.