H2Go is a domestic hydrogen (H2) sensor designed and developed by DefProc Engineering for the EIC, Northern Gas Networks and Wales & West Utilities. We have taken the device from a proof of concept to a fully functional prototype. As energy companies look for greener, sustainable energy sources, hydrogen is a contender to heat and fuel homes across the UK. Almost 85% of homes in the UK use natural gas for heating and cooking, accounting for 18% of all carbon emissions. In 2021, the UK’s first showcase of hydrogen homes opened at the Northern Gas Networks’ innovation site in Gateshead, allowing the public to see how hydrogen can power a zero-emission gas-fuelled home.
Project background
To increase confidence in hydrogen in domestic properties, the EIC, Northern Gas Networks and Wales and West Utilities wanted a device that looks and works similar to a smoke alarm. Using pure hydrogen as fuel means there is no carbon present. As a result, the domestic hydrogen sensor can replace existing carbon monoxide detectors already in homes.
There was nothing on the market for domestic hydrogen sensors. Industrial hydrogen detectors are unsuitable because they’re too expensive for a home environment. We needed to use our experience to create a device that met all the safety requirements while understanding that affordability and reliability would be essential to our clients and the end consumer.
Building a proof of concept
We began by conducting in-depth research and testing to identify the most suitable sensor. We ran it over several weeks in a typical office setting to evaluate its response in a baseline, low-hydrogen environment. The results demonstrated minimal noise, although environmental factors like air conditioning cycles affected readings slightly. To enhance accuracy, we found it essential to pair the gas sensor with temperature and humidity sensors, as air conditions significantly influence sensor resistance.
To prepare for testing, we built our proof of concept with the sensor board enclosed within gas-tight housing.
Internal vs external testing
Our initial proof-of-concept testing took place in the office, focusing on minimising sensor power draw and isolating hydrogen detection from other gases. Early results highlighted the role of humidity in sensor response, prompting us to adjust the test setup to better reflect typical household conditions. Next, we sent the sensor to the Health and Safety Executive Laboratories (HSL) for further testing. Here, we discovered an issue: a static discharge event had compromised the microcontroller. After receiving the device back from HSL, we revised the design to include a protective enclosure to shield internal components from static. This modification proved successful in follow-up testing.
Prototype development stages
Mechanical and Electrical Design Integration
The development of the domestic hydrogen sensor prototype involved a synchronised approach to mechanical and electrical design, ensuring that all electronic components fit seamlessly within the device’s housing. This dual focus allowed for efficient integration, with the mechanical case design and electrical schematics evolving in parallel. Once the initial designs were complete, test PCBs were manufactured and assembled with all components, followed by rigorous board testing to validate functionality.
Sensor Functionality
The H2Go device is equipped with two key types of sensors:
- Multi-element Hydrogen Sensor: Detects the presence of hydrogen by analysing the sensor elements’ resistance changes.
- Temperature and Humidity Sensor: Measures environmental factors, as temperature and humidity levels can impact sensor accuracy. These elements together ensure the device can detect hydrogen presence accurately, independent of other influencing gases or conditions.
The sensor actively monitors the ambient gas composition. When the hydrogen sensor’s readings cross pre-set thresholds, the device detects a hazardous concentration of hydrogen and activates an alarm. This setup differentiates hydrogen from other common gases, such as alcohol vapours, ammonia from cleaning products, and nitrogen oxides, enhancing its reliability in diverse environments.
Power System Design
Powering the H2Go device is a flexible system that supports both USB and battery inputs:
- Primary USB-C Input: Accepts 5V power for easy recharging, debugging, and device programming.
- Battery Backup: Configured to accept up to three pairs of AA batteries, with the device capable of running on a single pair if needed.
An automatic switchover feature prioritises USB power when available but seamlessly transitions to battery power if USB input is removed, ensuring uninterrupted operation.
User Interface and Alert Systems
The device features high-output red and green LEDs aligned with light pipes in the casing, providing clear visual feedback. A central button mounted on the PCB is accessible through the casing for user input. Additional features include:
- Magnetic Sounder: Positioned for optimal sound output, with sound directed outward through the casing for clear alerts.
- Micro-SD Card: For onboard data logging, accessible only when the case is open.
Iterative Improvements: Refining the Prototype
The prototype revision revealed a few areas for improvement. Key adjustments included:
- Correcting the USB-C footprint and solder paste application to strengthen the socket connection.
- Adjusting the battery measurement circuit to provide accurate voltage readings.
- Adding a capacitor near the sounder to stabilise power output during alarms.
- Adjusting the speaker alignment to maximize sound projection.
- Correcting the micro-SD card pinout to enable reliable data logging.
Following these refinements, the revised boards were manufactured, assembled, and tested successfully.
Finalisation and Design Freeze
With the electrical and mechanical designs completed, a CAD model for the device was created, allowing for a design freeze. This milestone shifted focus towards producing high-quality enclosures and PCBs for final prototype units, setting the stage for deployment and further testing.
What testing is required for a domestic hydrogen sensor?
The H2Go device underwent rigorous testing based on BS EN50194-1 standards for domestic combustible gas detectors, with an alert threshold set to trigger well before hydrogen reaches hazardous levels. Following the British Standard, our tests confirmed the device’s reliability in detecting hydrogen and alarming accurately.
We calibrated the sensors by evaluating stability in open air, responses to temperature and humidity changes, and varying hydrogen concentrations. Anticipating potential issues, we pre-stocked replacement components, allowing for immediate repairs and preventing delays. After successful internal tests, we sent ten devices to HSL for external validation.
At HSL, testing across a broad temperature and humidity range revealed a stronger response to environmental conditions than our in-house tests had shown, with DefProc staff present to observe. With all ten hydrogen detection devices performing effectively, the project achieved Technology Readiness Level (TRL) 7.
Next steps
While shifting government priorities and policies on domestic hydrogen suggests there is no immediate use case for H2Go, the foundational technology has been developed and rigorously tested, ensuring it is ready for scalable manufacturing when the time comes. Further testing will be required once standards for domestic hydrogen use are published, but H2Go stands as a robust blueprint for future devices in this field. As the hydrogen landscape evolves, H2Go is poised to play a key role in shaping the next generation of sustainable energy solutions.
