Drives & Controls July / August 2022

44 n CLEAN ENERGY July/August 2022 www.drivesncontrols.com than half as much as a sodium-sulphur ($532/MWh) or lithium-ion battery store ($367/MWh). The feasibility study for the Gravitricity scheme is due to be completed in late 2022. It will provide the information needed to build a full-scale commercial multi-weight gravity energy store at a grid-connected site in the north of England. This could involve sinking a purpose-built 10m-diameter and 250m-deep shaft. The company says that much of the mechanical design, control systems and the optimisation of the hoisting equipment, will be transferable to future applications. As production ramps up, Gravitricity and its partners intend to produce modular systems which will cut fabrication costs considerably. In the longer term, the consortium hopes to buy and operate its own shaft-sinking equipment, offering further cost improvements. This will also allow storage schemes to be located in areas where abandoned mineshafts are not available. Gravitricity envisages future schemes raising and lowering multiple weights totalling up to 12,000 tonnes in shafts up to 750m deep, providing almost 25MWh of flexible storage. But Gavitricity does not have the gravity storage market to itself. A Swiss company, Energy Vault, has built a system based on a 20- storey high crane which raises and lowers 35- tonne composite blocks. The company, which has attracted more than $400m in funding, is ready to go commercial by building 100m-tall “warehouses”containing dozens of energy elevators that each raise and lower 35-tonne blocks made from recycled materials such as fly ash or old wind turbine blades. One of Energy Vault’s first orders is for a 100MWh scheme to be built next to a wind farm in China. It has also signed an agreement with India’s largest power generating utility for a joint feasibility study that could lead to gravity storage systems being deployed in the sub-continent. According to a US Department of Energy report, the cumulative investment in grid- connected energy storage could amount to around $270bn over the coming ten years. If significant proportion of that storage is in the form of gravity-based systems, it could create substantial business opportunities not only for the designers of the storage systems, but also for suppliers of the necessary motor- generators, converter systems and controls. n Energy Vault envisages“warehouses”containing many energy elevators, which together could provide energy storage capacities measured in GWh Siemens’ Congleton VSD plant will hit carbon-neutrality eight years early Siemens’variable-speed drives factory in Congleton, Cheshire, is on track to achieve carbon neutrality later this year – eight years ahead of its original target. The site, which produces more than 1.2m controls and drives every year, has achieved this goal by deploying a range of sustainable technologies for energy generation and demand, including generating 75kW of renewable energy from a hydro-electric plant on the nearby River Dane, and using carbon-neutral biogas to power an on-site gas engine. These measures alone are saving the company £250,000 a year and have taken the 80% power-independent factory off the grid for much of the time. A building management system adjusts itself automatically to improve the site’s energy efficiency, while modern windows and LED lighting have cut energy bills by 13% and 30% respectively. The 50-year-old plant, which sends no waste to landfill, is eight years ahead of Siemens’original 2015 commitment to ensure its operations are carbon-neutral by 2030. In 2018, the Congleton factory became fully digital by embracing lean manufacturing methods to achieve continuous improvement and by adopting Industry 4.0 processes. It now uses advanced manufacturing methods including virtual reality, digital twins, the IIoT, robots, cloud storage and additive manufacturing to produce up to 50,000 variants to meet the changing demands of its customers and markets. In 1990, the site employed 400 people, making 50,000 VSDs and controls a year. Today, a similar number of workers produce 1.2 million devices, including 600,000 VSDs. This has been achieved within the same physical footprint. Because the factory is surrounded by industrial and housing estates, there is no room to expand, resulting in Congleton having one of the highest productivity rates per square metre of any Siemens site. The company has committed to ensuring that all of its global operations are carbon-neutral by 2030 and for all of its production facilities and buildings to achieve net zero-carbon footprints by 2030. “Siemens believes that sustainability is a force for good and can deliver value for all its stakeholders,”explains Andrew Peters, managing director of Siemens Digital Industries Congleton.“We want to help customers achieve sustainable growth and to transform their industries through decarbonisation.The first step of that is for us to achieve these ambitions in our own operations. “Our Congleton factory is paving the way for sustainability, whilst setting a great example on how manufacturers can join this amazing journey to net- zero,”adds Olivia Whitlam, Siemens’head of sustainability for the UK and Ireland.“We have 8,600 people spread across offices and 11 manufacturing sites across the UK and we are creating innovation up and down the country with sustainability at the core of our operations and services.” Siemens’Congleton site has no room to expand, resulting on one of the company’s highest productivity rates per square metre