DefProc’s latest collaboration with Northern Gas Networks (NGN) has led to the creation of a Smart Gas Pressure Sensor. Designed to detect low-pressure in consumer homes, the device works with natural gas, 100% hydrogen and a blended supply. If the pressure goes below the low threshold point (17 mbar), the device activates a shut-off valve to close the customer’s gas supply and assist in protecting the wider network.

Project background

As part of its Hydrogen Strategy, the UK Government is supporting research, development and testing projects to determine the feasibility of using hydrogen as an alternative to natural gas for heating. Hydrogen has a lower density and energy content than natural gas, so it needs a higher flow rate. As the UK gas networks run at low pressure, maintaining supply pressure is crucial for both consumers and equipment. 

In the event of an incident on the network, a reduction in gas supply pressure could affect the security of supply and delivery of gas at a satisfactory pressure. In extreme conditions, the gas supply is isolated to allow the network to recover. Reestablishing supply is costly and time-consuming as it relies on gaining access to each property multiple times. To solve this problem, NGN wanted a device that could detect low pressure at the point of supply in consumer properties and activate a shut-off valve to isolate the gas supply.

The Smart Gas Pressure Sensor device

The first technical breakthrough was verifying the most appropriate system design to meet the monitoring and reporting of pressure and under-pressure shut-off (UPSO) conditions. The initial focus was selecting and testing potential device components to build a proof of concept. We conducted pressure testing to ensure the device was gas-tight, before sending it to DNV in Groningen for external testing with hydrogen and methane. They also monitor pressure drop to determine the device’s reaction time and responsiveness to different humidity and temperature levels.

Following the testing at DNV, we began the development of the prototypes. We had confirmation that the proof of concept device worked as intended, and now the focus was on its physical design.

The key design decisions during the prototyping stage were:

• Pressure sensor: We explored several different pressure sensors. Our chosen sensor is compatible with hydrogen and natural gas, allows pressure sensing up to 2 bar and is suitable for low-power applications.
• Valve: Decisions for the valve included selecting the type of ball valve, how to power the valve motor drive and its positioning within the size-restricted device. 
• Materials: Any material used had to be compatible with hydrogen and natural gas.
• Power input: Input from an external power source (mains) was preferred over an internal battery. However, the voltage input needed to be close to the operating voltage to minimise losses. With this in mind, the hardware includes a USB port to power the device alongside a silicone insert plug to prevent dust ingress when not in use.
• Battery: The initial choice was either primary (non-rechargeable) or secondary (rechargeable) battery type. Due to the self-discharge present in secondary batteries, and the design requirement for multi-year use, primary batteries offered the most suitable energy storage. The battery will offer power backup in the event of a power loss. The device will also send an alert to notify the gas network about the mains power outage.
• Microcontroller: All the onboard functions of the device are controlled by the microcontroller. We chose an Arm Cortex M0+ due to its compatibility with Arduino and long-life, battery-powered applications. 
• Connectivity: LoRaWAN was chosen for the device’s connectivity. It offers low power, security and good signal penetration through walls and enclosed spaces. This is important if the device is to run for a long time without human intervention. 
• State indicator: It was necessary to indicate the valve’s status (open/closed) to local users. However, the requirement for the device to be low-power and long-life meant minimising energy consumption. As a result, the LED emits periodic short flashes to indicate the operating state.
• Volume and shape: The device had to fit within the limited volume between the property’s emergency control valve (ECV) and the gas meter. We used the layout of the meter boxes at NGN’s Futures Close homes as a reference.
• Data display (UI): The data from the LoRaWAN application is forwarded securely to a server. A database specifically designed for storing sensor readings against a timestamp collects the information. The dashboard displays current and historical data and includes an alert system if a device drops below the 17 mbar threshold.
• Tamper indicator: As the device will be fitted in consumer meter boxes, the gas network must know if it is tampered with. The device features a switch which, when triggered, will send an immediate alert via LoRaWAN. 

The development phase concluded with five fully functional prototypes that will be sent for external testing and deployment.

The benefits

The Smart Gas Pressure Sensor will fill the expected market need for monitoring supply pressure. Where this measurement is necessary as part of the network’s hydrogen roll-out, the device ensures that the deployment will not face delays. The monitoring capabilities and automatic shut-off valve will also maximise the stability of hydrogen on the gas network. It can provide near-real-time data retrieval at the point of supply so operators can view what’s happening anytime, anywhere.

Network operators can verify which end-user supplies are disconnected before restoring pressure, saving time and operational costs compared to manual reset procedures. Pressure monitoring will highlight if there’s a problem with the supply and shut-off valve monitoring will show the supply status. Multiple engineer visits are no longer essential to disconnect and reconnect the supply following an incident.

From a customer perspective, reducing engineer visits will limit the disruption they face. Operators can leverage the device’s smart element to notify customers if their supply has stopped and why. Offering timely messaging about the supply status may increase consumer confidence and acceptance of a new fuel type. There is also potential to utilise data from the sensors to monitor the network. This will highlight pressure issues and allow the network to resolve them proactively, allowing fewer and shorter interruptions for consumers.

What’s next?

After testing is complete at DNV, the five prototype devices will go to NGN’s Futures Close at Low Thornley. This will allow for extended testing on supply and future testing in a representative environment. Currently, the Smart Gas Pressure Sensor is at Technology Readiness Level (TRL) 6. Extended testing will provide feedback on the longevity of the devices and allow direct observation and feedback on the functions. It will provide information from the live gas supply to ensure reliable operation going into hydrogen trials. Successful completion of testing and trials will bring Smart Gas to TRL 7. 

The Smart Gas Pressure Sensor project is on the shortlist for the Engineering and Manufacturing Awards R&D Project of the Year. The award celebrates product research and development projects that showcase measurable design successes. We value the recognition and hope to continue the device’s development after the trials at Low Thornley. 

If you require technical expertise for your next project, we’d love to hear from you! You can get in touch via email (contact@defproc.co.uk) or head to our new contact page to kickstart the process.