London-based electrical contractor Thamesgate Group’s team of mechanical and electrical engineers faced a wide variety of problems when it won a contract to replace a 1MW/3MWhr energy storage component within a PureWave Storage Management System for S&C Electric Europe on a remote island location in Scotland. Nick Watkins, Thamesgate’s managing director, explains:
The challenges faced included 90mph winds from all directions and the logistics of shipping and installing over 3000 lead-acid batteries from Japan. Then there was the rain endured during one of the UK’s worst storm periods in the winter of 2013/14. All-in-all a pretty challenging set of circumstances for one of the company’s largest ever projects.
The project involved replacing an existing 1MW/3MWhr energy storage component within a PureWave Storage Management System supplied by the client S&C, in a remote island location in Scotland. A decision was taken for the existing installation based on sodium-sulphur technology to be replaced with an alternative lead-acid battery system supplied by Yuasa Battery Sales (UK). The installation of the new battery system meant that the building used to house the original sodium-sulphur system would need to be redesigned (or demolished) to support a totally different physical footprint, volumetric size and ambient properties. The timescales allowed were three to six months to meet the contractual 'switch-on' date with S&C.
Following an initial visit to S&C’s Swansea office, Thamesgate visited the island location to gather the information and technical data required to complete a project proposal. This was turned round within three weeks and accepted by S&C. Work began on the installation in October 2013 with a three month installation window allowed during one of the UK’s worst storm periods in recent memory.
The building used to house the battery system, PureWave Storage Management System and switchgear is a standard prefabricated sheet metal construction with roller front door and rear opening door access, forced air ventilation and concrete floor with channels for the electrical cables connecting the components to the switchgear. Partitions create separate areas for the switchgear and batteries with the original sodium-sulphur system bolted as a self-contained unit within the main area. The building design is typical of container type structures in the area that have to withstand weather extremes.
One of the first problems encountered was that of space for the mechanical and electrical (M&E) design. The original sodium-sulphur battery was a vertically stacked system whereas the proposed Yuasa installation would comprise 3,188 1,000Ah 2V DC batteries each weighing 64kg that would be configured as modules in 132 open racks across the available floor space. The Yuasa batteries could only be stacked four high up to 1.4m giving an overall footprint that would be five or more times greater than the original system but with a far reduced vertical installation height. As a result, everything had to be precision measured to the mm to fit the Yuasa batteries and stands alongside the control gear and monitoring systems.
The next problem to be solved was that of how to seal the building and maintain it at a constant 20 to 25°C temperature – the optimal range for valve regulated lead acid (VRLA) batteries. The original sodium-sulphur installation featured an internal operating temperature from 300 to 350°C so the building had forced air ventilation. Maintaining the correct temperature for the new battery system required the installation of Mitsubishi/Hitachi fresh air ventilation units to create a controlled environment compartment within the shell of the building. However, the location of the structure means that it is subjected to winds of up to 90mph that can hit from any direction so that any externally mounted heating/cooling apparatus would require protection – and not just from the wind. The potential for horizontal rain ingress that could adversely affect external condenser monitoring leading to possible erratic operation also had to be addressed. In this case, Mitsubishi/Hitachi had to resolve issues they had not encountered previously. The extreme wind and rain could lead to the condenser frosting up and put the units into heating mode resulting in colder air being blown into the building. Ultimately, protective cowlings were installed to resolve this issue.
Further problems related to a variety of health and safety issues. Smoke, fire and hydrogen detection were principal concerns so a VESDA fire and suppression system was installed to continuously sample air within the room and provide superior and more rapid detection compared with traditional smoke detectors. Should the fire suppression be activated, the room is filled with IG55 gas from local canisters following an alarm sequence. A concealed grid metal frame (MF) provides a solid core ceiling to reduce the amount of fire suppression gas required.
The Yuasa VRLA battery system does not discharge gas during normal use. As an added safety measure, hydrogen detection was installed along with a large extractor system to vent to the outside of the building.
With daily cyclic operation and a long design life, the battery installation had to be safely managed and maintained with thought given to future battery testing and maintenance. At installation, each Yuasa battery was impedance tested and thermally checked to ensure reliable operation.
Besides the foregoing, another major issue involved with the project was one of logistics. The remoteness of the location meant that availability of accommodation was limited even in winter so Thamesgate had to rent out homes for its 12-person team who lived on the island for the duration of the project. Local sub-contractors provided additional support and assistance during the project while the 3000+ batteries themselves were delivered on containerised vessels direct from Yuasa’s Japanese manufacturing facility.
The result of the project is one of the world’s largest lead-acid battery installations in one of the remotest parts of the UK. Cross-functional teams and suppliers from around the world combined to solve a number of challenging design and build issues with Thamesgate as the main contractor providing the necessary co-ordination and guidance to complete the energy storage facility.
Thamesgate identified energy storage as a business development area some time ago and this latest project is one of the largest in which the company has ever been involved. Energy storage is a rapidly emerging industry and Thamesgate continues to develop its expertise in DC systems with the aim of becoming a principal supplier to smart-grid companies such as S&C Electric Europe.