Sustainability covers such a large remit that it is often difficult to define exactly what it means – it’s something the rail industry is still grappling with. It can mean recycling waste goods and investing in renewable energy sources, but for businesses it is also about efficiency and safety.
In the Netherlands, the railway is a leading example of a sustainable business. As of the start of this year, wind turbines supply 100 per cent of the power for its electrified network.
At Rail Media’s Sustainability Summit in 2015, ADComms’ head of next generation networks, Mike Hewitt, explained plans for a hybrid power solution the company was preparing to deliver for a GSM-R repeater at Worlaby in Lincolnshire.
Network Rail was seeking a way of powering the repeater without connecting it to a trackside electricity supply which is a more cost-effective and practical way of powering the repeater. The scheme is something of a pilot project for exploring the use of renewable energy sources to power Britain’s railway.
Drawing electricity from a trackside power cabinet presented issues with access, high installation costs and a high risk of vandalism. The solution had been to use a large diesel generator; besides the cost of hiring, refuelling and maintaining the generator, this wasn’t a particularly environmentally friendly option.
Primary and secondary sources
ADComms, which has since been acquired by Panasonic, proposed a hybrid solution using solar power as the primary energy source. The challenge with off-grid solutions is the basis to understand in depth the load requirements and the solar energy and surface meteorology data for any given location. The key components are the solar harvesting, the energy storage and appropriate sizing of the generator solution for the site. The aim was to store sufficient energy to reduce the need for refuelling to a single site visit each year.
Instead of connecting it to the grid, the repeater would draw the majority of its energy from a set of lithium-ion batteries. Li-ion was chosen over VRLA (valve-regulated lead-acid) due to its higher- density storage capacity, increased operating temperature and longer life cycle. These would harvest and store the energy supplied by solar panels, with a diesel generator acting as a backup.
The system design was based on the following base data:
“The high-level objectives were to provide a reliable, cost-effective, off-grid power solution with modern, innovative and best-of-breed components,” explained Andrea Johnston, project manager for ADComms at Worlaby. “Maintenance should be kept to a minimum with the aim of a single yearly visit to service the site and refuel the diesel generator. Site monitoring is key to ensure the site is functioning within design parameters – the solution is powering a safety critical device, the GSM-R repeater.”
Andrea added: “The primary power source is a solar array of 12 Panasonic panels, charging the lithium batteries which provide the power to the repeater. The secondary power is provided by a generator which is primed to start and charge the batteries when the solar power is not sufficient.”
The system design was based on twelve 250W Panasonic Solar Panels, connected to a 235Ah Li-ion battery solution. This is supplemented with a 6kW diesel generator set.
The target was to achieve, each year, 2,631kWh of energy production from solar, or 48.5 per cent of the energy production from solar harvesting with an excess of 1,632kWh available for storage. The intention for the generator was for less than 48 starts per year and fuel consumption of under 500 litres over the annual cycle.
Key to the system is an innovative cloud-based remote monitoring and management system which provides full site visibility, monitoring and performance measuring. Cyber security is also a key consideration and the remote connectivity included a combination of encrypted radio interface and relies on FIPS140-2 cryptography standard compliance.
Live site
Planning for the trial at Worlaby began in 2015. The site had been prone to fly tipping and so had to be cleared, and the project involved a sizeable amount of civils works. This all had to be achieved on a site with restricted access. Andrea, who has been with ADComms since 2004, typically oversees the installation of repeaters and commented that this project presented a variety of new challenges.
The installation went live in June 2016 and, although the dark winter months will provide the sternest test, it performed well throughout the summer.
Low maintenance
The use of solar power technology by this pilot Worlaby project will no doubt inform future projects. Not only was solar power an environmentally friendly solution, it was also the most practical and financially beneficial option. Running a diesel generator throughout the year costs somewhere in the region of £30,000 and requires more than 16 site visits for maintenance and refuelling.
Although the cost of installing this kind of hybrid system is higher than a traditional grid supply or generator, AD Comms believes the long-term maintenance costs will be much lower as it removes the need for so many site visits and allows for a predictive approach to maintenance.
The trial will continue until towards the end of this year.
