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Doctor of Engineering (EngD) - LED-based gas sensing platform for the detection of leaks of new refrigerants (Edinburgh Instruments and Heriot-Watt University) FILLED

   School of Engineering & Physical Sciences

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  Prof D Reid, Dr J Marques-Hueso  No more applications being accepted  Funded PhD Project (UK Students Only)

About the Project

The UK’s Net Zero targets can only be met by 2050 by drastically reducing carbon emissions and limiting the use of greenhouse gases and F-gases. Meanwhile, climate change will likely result in the increased use of air conditioning and cooling systems, which consequently will derive in increased amounts of refrigerants being leaked in the atmosphere.

There is currently a drive to investigate the use of the so-called 4th generation refrigerants in such appliances, as they are deemed more environmental-friendly due to their low GWP (Global Warming Potential) and having zero ODP (Ozone Depletion Potential). These refrigerants are HFOs, or hydrofluoroolefin, and are unsaturated organic molecules incorporating fluorine. Although there is a risk that in the medium to long term after leakage that some of these refrigerants decompose in tetrafluoroacetic acid and/or HF, they are currently deemed non-toxic but are flammable to mildly flammable and much more expensive than other generation of refrigerants. Therefore, reducing risks of leaks is necessary for energy efficiency, safety and costs reasons.

Leak monitors of HFOs exist on the market and are currently based on two sensing technologies: semiconductor sensors and infrared sensors. While semiconductor sensors are generally used for large leaks detection, infrared sensors are more suitable for small leaks detection and are based on heated diode technology (which suffers from short life-time) or infrared hand held detectors which compare samples to one another, meaning the sampling probe needs to be moving constantly.

The objective of this project is to develop a low-power, cost-effective, HFO-leakage monitoring system, OEM or battery-powered, using LED technology. The emission of commercial LEDs is typically limited to wavelengths under 6 um, which prevents the use of longer wavelength absorption lines of HFOs. The main absorption bands of HFO below 6um overlap with atmospheric gases. The project proposes to develop a dual path system where two LEDs will be pulsed for improved energy efficiency, one LED will be used to determine the baseline atmospheric gas content and the other one will be used to detect the presence of HFO.

The prototype will be designed to be a fixed system deployable across several locations at production sites or at point of use of refrigerated systems. In addition, the system will be IoT-enabled for the remote detection of leaks of refrigerants.

The project fits well with the CDT photonics scope, as light sources (LEDs) and photodetectors will be used for HFOs leak sensing and photonic sensing is one of the priority topical areas.

The novelty of the project is two-fold. First a substantial amount of work is still being done to develop and investigate new refrigerants. This is a developing field and experimental work to understand the spectroscopic signature of these gases will be required. Second, the development of a new sensing platform that outperforms current technology in terms of low maintenance, cost and power consumption. Current HFO leak detectors are either semiconductor-based meant to be in fixed position to detect large leaks of refrigerants or are sensitive hand-held leak detectors based on infrared technology. There will therefore be a real market need for sensitive, fixed and connected HFO leak detectors.

HFOs (and refrigerants in general) can be used in a wide range different applications. For instance, some would be more suited for heat pumps, others for freezers or cooling systems. Therefore this project is the starting point of a large body of work to develop LED-based leak detectors for a variety of markets, at the production site of HFOs or at end use point.

In addition, the successful student will benefit from an existing and successful history of collaboration between Dr J. Marques-Hueso and Edinburgh Instruments Ltd.

The project will provide opportunities for scientific publication: in areas related to the spectroscopy of refrigerants, and in technological advances that can be disclosed. There is scope for presenting the work at scientific conferences.

The student will be based in the facilities of Edinburgh Sensors in Livingston. The project will be mostly lab-based and the student will share an office with other staff members. Remote working will be possible for literature search and writing activities.

Activities will likely overlap with other businesses in the Techcomp Europe group such as Froilabo and Edinburgh Instruments.

We are fully committed to being recognised as an ethical and trustworthy company and try to ensure we embed policies and processes across the group and integrate them into day-to-day business practice.

Wherever possible we work continuously to reduce our carbon footprint and deliver products that are eco-friendly and non-hazardous to the environment.

We also strongly believe in supporting developments in new technology and work closely with universities and companies to bring new ideas to market.

The company operates with flexible working hours, this can be discussed during the interview. The Company is committed to promoting, encouraging, and ensuring equality, diversity, and inclusion in the workplace. 

CDT Essential Criteria

A Masters level degree (MEng, MPhys, MSc) at 2.1 or equivalent

Desire to work collegiately, be involved in outreach, undertake taught and professional skills study

Project Essential Criteria

Enthusiasm and problem-solving skills

Ability and willingness to present technical information to senior management, at international conferences and any other stakeholder such as customers

Commercial mind-set

Experience with experimental optical set up

Thorough understanding of geometrical optics.

Project Desirable Criteria

Any experience with programming languages such as Matlab or optical design software such as Zemax would be beneficial.

Experience using Hitran database

Any experience or knowledge of optical gas analysis

Awareness of safe gas and light source handling

Understanding of electronics


The CDT in Applied Photonics provides a supportive, collaborative environment which values inclusivity and is committed to creating and sustaining a positive and supportive environment for all our applicants, students, and staff. For further information, please see our ED&I statement Forming a supportive cohort is an important part of the programme and our students take part in various professional skills workshops, including Responsible Research and Innovation workshops and attend Outreach Training.

Funding Notes

For International students this project is only partially funded. International students will be provided with a minimum stipend of £15,609 per annum in the first year increasing to £22,907 in years two to four, however are required to fund the difference between the Home Fee which the EPSRC fund and the International Fee charged by the University; the cost of this is in the region of £15,500 per annum for four years, a total cost in the region of £62,000.
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