A partnership with Finning has allowed Southern Water to maximise its return from investing in CHP technology. This has led to some of its sites becoming self-sufficient in terms of energy generation, as well as benefiting from a comprehensive support package that has meant some biogas generators have clocked up over 100,000 run hours and are still operating efficiently.
Self-sufficient energy
Recognising they had a readily available renewable fuel source, Southern Water tasked Finning with exploring how energy generation from biogas could be used alongside existing CHP equipment.
Matt Bryan, Gas Engines Product Support Account Manager for Finning explains:
“Southern Water wanted to use the wastewater treated at their sites to both help power their sites and sell any surplus energy back to the National Grid. To do this effectively they needed a solution that could perform reliably in quite challenging conditions. The biogas their sites produce can vary in quality so lacked the same consistency as natural gas, which would have been a problem for some generator models.”
Biogas was already being used to power a sludge dryer, but Finning identified that installing a Cat® G3520C gas generator to run off biogas would deliver an additional 1.95MWe – enough to meet all of the site’s energy needs. This allowed Southern Water to substantially reduce energy costs and its use of fossil fuels.
Caterpillar G-Series generators were selected for their ability to maintain a consistent output from varying gas quality, making them a resilient choice given that biogas composition can differ quite widely. Furthermore, the system installed by Finning included both a gas collection and compression station to filter the biogas and remove some of the solids, as well as a gas clean up skid that removes other contaminants. This uses new technology to remove siloxanes, which if left would coat the engine cylinder head with a glass hard surface that would damage the cylinder heads and valves.
Modular installation reduces disruption
The success of this first project led to Finning installing seven more generators at other Southern Water sites. Because installation of CHP equipment can mean significant disruption and downtime for plants, a modular approach was taken for all of these.
This means that most of the necessary design and engineering work is completed at Finning’s own facilities, with the system then delivered in a series of self-contained modules in order to minimise disruption and cut time needed on site by as much as 50%.
For example, the modular packages at Southern Water’s Budd’s Farm facility included the generator set and associated synchronisation, G59 and LIMA remote control and monitoring equipment, a heat recovery system, as well as the gas collection and compression station, and gas clean up skid. For the Peacehaven site, the package was adapted to include a dual gas train allowing it to run on either biogas or natural gas. This was an important consideration as without power vital processes in the plant cannot operate. The package is therefore configured to run in island mode should the site suffer a mains power failure, enabling processes such as the supply of heat to the digesters, to remain at full capacity.
Long-term reliability
Alongside specifying the right equipment and ensuring it was installed with minimum disruption, Southern Water recognised that they would only receive the maximum benefits from the systems if they were kept running efficiently and reliably.
Matt Bryan continues:
“Crucially, as an investment for their business, Southern Water needed generators to perform consistently across a sustained period of time. Every time an engine was offline would not only cost them money in having to buy in replacement energy but also negatively impact their carbon footprint. So, they needed specialist support in ensuring their generators were maintained to perform as reliably as possible.”
“This meant that specifying the right generators for their needs was only part of our challenge. In order for the project to be a sustained success we have devised and delivered a program of maintenance and repair over the course of fifteen years. This has meant Southern Water benefit from high availability levels and minimal downtime.”
Key to maintaining this remarkable record has been the dedicated team of Gas Safe registered engineers that Finning has based in the South of England. These specialists are on hand to conduct routine and emergency work on all the generators, with parts available quickly through its network of branches.
This expertise is complemented by 24/7 remote monitoring of the generators and associated plant such as dry air coolers, heat exchangers and heat recovery systems. Bryan continues:
“If the sites face a problem such as power outage, then the generators can trip and not restart automatically. Historically this would mean a call-out and a wait for an engineer to arrive, whereas our remote monitoring system will automatically detect unexpected shutdowns and allow us to restart to engine without needing to visit site. This helps to keep unplanned downtime to an absolute minimum.”
Longevity and value
Thanks to the expert ongoing maintenance of the generators, some units have now exceeded 100,000 run hours – a significant milestone in the value Southern Water have gained from working with Finning.
Furthermore, the success of the project has meant that a rebuild project is being planned for some of the older machines, which will offer a sustainable way to prolong their life and avoid the need to buy new equipment.
