Winning at DHN Thermal Inspections

Nov 8, 2019 | DHN, Thermography

The Problem

Leaks in District Heating Networks (DHNs) can be very hard to locate. By comparing the hot water flow out into the network with the return flow, Enviroenergy can estimate the cost of the heat losses from Nottingham City’s DHN, at around £150,000 per year.

Pinpointing the precise location of faults is complicated, especially for chronic small leaks. Network pipe routes often run beneath inaccessible or private land where a car-mounted or handheld thermal camera 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 1 cubic meter of water every day. Larger leaks have also proven hard to locate using traditional methods and can lose up to 12 cubic meters per day, running undetected for years.

Water loss from the network leads to heat loss, wasted energy and hence inefficiencies in the system.

If the government’s vision of a larger heat network sector is to be realised, we need initiatives like this to drive costs down and improve the competitiveness of these networks.” – Stephen Hayes, Nottingham City Council

Objective and Proposal

Drones can 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 direct fact-based repair and maintenance operations. Therefore processing, interpreting and presenting this data in a digestible format was crucial to the project delivery.

Project Team

HexCam was invited by Innovation Gateway to submit a proposal detailing how aerial thermography could help to improve the performance of District Heat Networks (DHNs).

After pitching to representatives from large organisations, we were selected for a follow up meeting by Nottingham City Council with the Energy Services Team. We were introduced to Drone Systems ApS, a Danish company specialising in mapping and categorising defects in DHNs.

HexCam’s knowledge and experience of flying drones in complex environments, coupled with Drone Systems’ expertise of high resolution thermal mapping and data analysis, allowed us to join forces offering a full inspection and reporting service to Nottingham City Council and Enviroenergy.

Choosing the right combination of drone and sensor for the local environment, topography, ground conditions and weather conditions is key to successful data capture.

Nottingham’s DHN supplies heat to densely populated urban and city center commercial areas, so safety of the flights was critical. Reliability of the drone and sensor is absolutely essential as optimal weather conditions may not last for long and the complex logistics involved may only allow access to Take-Off and Landing Sites (TOLS) for a short time.

Finding suitable ground station sites that could be used safely within our CAA permissions allowing us to adequately cover the mapping area from the right height above ground whilst keeping the drone within Visual Line of Sight (VLOS) at all times.

The Solution

Mission planning was critical to things going smoothly when a suitable weather window opened up as Drone Systems’ weather condition requirements for capture were very specific.

HexCam completed extensive desktop and on-site planning, engaging with local police, property owners and local authority departments, ensuring all permissions were in place to safely access and use a series of 10 TOLS around the city. Sites ranged from parks to shopping center rooftops and even the pig enclosure of a city farm.

Steven Hayes, Nottingham City Council said: “In my view what makes these organisations great is the competency of the individuals working within them, without which, this project wouldn’t have been as successful.”

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

We worked through 2 full nights to capture 290ha of thermal data to create a thermal map and provide reporting and interpretation. The processed thermal orthomap together with all interpretation and reporting is accessed by Enviroenergy using Drone Systems’ ‘Teraplan’ portal. Using this system, Enviroenergy have been able to view categorised leaks and other hot spots pinpointed to a precision of 20cm to 30cm.

The Rewards

A high resolution thermal map of the entire network up to the outer walls of buildings overlaid onto pipe layout drawings and visual imagery makes locating problems more straightforward. Accurately locating anomalies means that Enviroenergy’s maintenance teams can now dig directly to faults rather than digging long ‘exploratory’ trenches in the street. More focused excavations means less time on site and reduced disturbance for local residents.

Enviroenergy now have visibility of smaller leaks that might otherwise have gone undetected for years. Reducing leaks and carrying out more focused maintenance should lead to cost savings for Enviroenergy and more reliable heating provision to customers.

As well as providing information about heat loss from the network, the thermal maps have provided Nottingham’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 with useful data on building envelope insulation standards.

Without drones it would not have been possible to capture data covering the entire network in such a short timescale 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 energy efficiency of the network.

Award Winning

At The Association for Decentralised Energy awards 2019 the Innovation Award, sponsored by Switch2, was presented to Nottingham City Council and Enviroenergy for their pioneering use of drones to carry out rapid inspections of heat networks.