Case study //

Nottingham District Heating Network (DHN) Citywide Thermographic Survey, Mapping & Reporting

Category: Thermography

Client: Nottingham City Council / Enviroenergy (via Drone Systems ApS, Denmark)

Date: January 2019

Summary: Two night citywide aerial thermal survey, mapping and anomaly reporting for Nottingham’s District Heating Network (DHN) comprising 60km of buried insulated pipeworks and covering an area of 290 hectares.

The problem

Leaks in District Heating Networks (DHNs) can be hard to locate. By comparing network supply and return flows at thermal substations on the network, Enviroenergy estimated the cost of 2018 heat losses from the DHN to be around £150,000.

Pinpointing the precise location of network faults can be complicated, especially for small chronic leaks that are not obvious on the surface. Network pipes often run beneath inaccessible or private land where car-mounted or handheld thermal cameras would not be able to reach. Enviroenergy needed a quick and reliable solution to locate faults across the whole network as even the smallest leaks can each result in the loss of 1m³ of water every day running undetected for months or even years. Some larger leaks have also proved hard to locate using traditional methods and can lose up to 12 m³ per day. Water loss from the network equates to heat loss, wasted energy and hence inefficiency in the system.


Drones are able to capture high resolution thermal data over large areas without the challenges of physical access on the ground. The primary objective was to provide meaningful results that would enable Enviroenergy to focus its reactive repair and proactive maintenance operations in the right locations. Processing, interpreting and presenting the thermal data in an intuitive and easily digestible format was crucial to the project delivery.

Project Team

HexCam was originally invited by Innovation Gateway to submit a proposal detailing how drone-based aerial thermography could help to improve the performance of District Heat Networks (DHNs). After pitching our ideas, we were selected for a follow up meeting with Nottingham City Council’s Energy Services Team and were introduced to ‘Drone Systems ApS’, a Danish company specialising in thermal mapping and defects analysis for DHNs.

HexCam’s UK knowledge and experience of flying drones in complex city environments, coupled with Drone Systems’ DHN expertise and high resolution thermal mapping and data analysis, allowed us to join forces to provide a full inspection and reporting service to Nottingham City Council and Enviroenergy. We’ve been working together on a number of UK DHN projects ever since.

The Solution

Good mission planning was critical to ensuring a smooth and safe operation when a suitable weather window opened up.  HexCam completed extensive desktop and on-site planning, engaging with local police, property owners, local authority departments and other stakeholders, ensuring that all permissions were in place to safely access and use a series of 10 Take-Off and Landing Sites (TOLS) around the city. Sites ranged from parks and burial grounds to shopping centre rooftops and even the pig enclosure of Stonebridge City Farm.

Flight routes over the city were planned using UgCS flight automation software, allowing us to combine linear and grid mapping patterns within a single flight and making the most efficient use of our batteries.

We worked through 2 full nights to capture 290ha of thermal data for the creation of a thermal orthomap for subsequent reporting and interpretation. The carefully tuned thermal map, together with geo-located anomaly reporting and interpretation is accessed by Enviroenergy using Drone Systems’ ‘Teraplan’ portal which allows them to view categorised leaks and other thermal points of interest geolocated and pinpointed to a precision of 20 to 30cm.

The Rewards

A high resolution thermal map of the entire city network up to the outer walls of buildings, overlaid onto pipe layout drawings and Google mapping (including Streetview), makes locating and labelling potential thermal issues more straightforward for network managers and maintenance engineers.

Accurately locating thermal anomalies means that Enviroenergy’s maintenance teams can now dig directly to faults rather than digging ‘exploratory’ trenches in the street. More focussed excavations means less time on site, reduced maintenance costs and reduced disturbance for local residents.

Enviroenergy were able to see developing problems as well as smaller leaks that might otherwise have gone undetected for years. Reducing leaks and carrying out more focussed maintenance should lead to cost savings for Enviroenergy and more reliable heating provision to customers. By carrying out annual or even bi-annual surveys, changes in heat loss can be detected allowing developing issues to be spotted and resolved before they become full-blown leaks.

As well as providing information about heat loss from the network, the thermal maps have provided Nottingham City Council’s Energy Services Team with multi-use data including the identification and location of roofs with significant heat signatures. As some parts of the network run through roof voids, a warm roof could indicate a pipe insulation problem. Wide area information about heat loss from roofs could also provide Nottingham City Council with useful data on building envelope insulation standards.

Without drones it would not have been possible to capture data covering the entire city network in such a short timescale and with the precision needed to detect even the smallest of leaks. Previously, leaks from the DHN could have gone undetected, making this project exceptional as a solution for increasing the efficiency of the network.

The innovation of this DHN thermal mapping and reporting project was recognised by the Association for Decentralised Energy (ADE) winning its 2019 innovation award.