November/December 2019

n TECHNOLOGY November/December 2019 www.drivesncontrols.com 22 POWERFUL MOTORS and regenerative drives are at the heart of a novel gravity-based energy storage technology being developed by a Swiss company called Energy Vault. When there is a surplus of energy, the system will use cranes to lift and stack 35-tonne concrete composite blocks to form towers up to 120m high. When energy is costly or in short supply, the system will lower the blocks to the ground to generate electricity . The technology is intended, in particular, to ensure continuous outputs from intermittent sources of energy such as wind and solar power. It will store energy when these plants are operating at high outputs, and release it when winds or light, or the sun is not shining. For the first time, says Energy Vault, it is offering a system that can deliver power around the clock for less than the price of fossil fuels. Compared to other storage technologies, such as batteries, the Energy Vault system promises: low costs (the electricity will cost around 6 US cents per kWh); long operating lives of more than 30 years with no degradation in performance; roundtrip efficiencies of 80-90%; and the avoidance of potentially polluting materials such as lithium and lead. The technology was inspired by pumped- storage hydroelectric schemes which rely on gravity and the movement of water to store and discharge electricity. But the concrete block system costs less to build, is more efficient, does not need specific topographies to operate, and avoids potential negative impacts on the environment. The technology has already attracted $110m of funding from the massive Japanese investor, SoftBank – its first investment in the energy storage market. A key to the Energy Vault technology is the software that it uses to control the automated lifting and lowering operations of the six-arm crane at the core of each tower. Proprietary algorithms take into account factors such as energy supply and demand levels, grid stability and weather conditions. The system also incorporates machine vision technology. The first large-scale prototype of the Energy Vault technology is due to start operating within months in Northern Italy, and will use six 1.3MW motors and high- efficiency regenerative inverters supplied by Nidec ASI. The Indian utility Tata Power has signed an agreement for a similar 35MWh system with a peak output of 4MW, which will be able to deliver full power within 2.9s of being requested. Energy Vault envisages modular plants with storage capacities up to 80MWh, capable of delivering up to 8MW of continuous power for periods of up to 16 hours. www.energyvault.com Regen drives are key to energy storage system that is ‘cheaper than fossil fuels’ THE ETHERCAT Technology Group (ETG) has accepted Beckhoff Automation’s 1Gb/s and 10Gb/s versions of EtherCat – known as EtherCat G and G10 – as additions to its official EtherCat standard. Beckhoff announced the development of the high-speed variants last year and, following a“thorough review”, ETG’s Technical Committee has now decided to accept them into the standard. “EtherCat is already the fastest industrial Ethernet fieldbus, and will remain so due to its special functional principle,” says Dr Guido Beckmann, chairman of the ETG’s Technical Committee. “With EtherCat G, particularly data-hungry applications – such as machine vision and high-end measurement technology – can now also be integrated. This extends the range of applications for EtherCat technology and makes it even more viable for the future.” For most applications, the standard 100Mb/s EtherCat technology will remain the most suitable version. However, in applications where large amounts of process data must be transported per device, EtherCat G might be more appropriate. As well as machine vision, these could include complex motion controls applications that go beyond the scope of classic drive controls. As an extension of standard EtherCat technology, EtherCat G is compatible with existing devices designed for 100Mb/s operation. These can be can be integrated into an EtherCat G system, or EtherCat G devices integrated into a 100Mb/s EtherCat system, where they will behave like standard EtherCat devices. EtherCat G is compatible with the IEEE 802.3 Ethernet standard and does not need any software adaptions in controllers. The key element of EtherCat G is its use of EtherCat“branch controllers”, which have two main functions: they act as nodes for integrating segments from 100Mb/s devices; and they enable parallel processing of the connected EtherCat segments. This is said to reduce propagation delays in the system “significantly”, increasing system performance many times over previous levels. The ETG is currently working to add EtherCat G (the 1Gb/s version) and G10 (the 10Gb/s version) to its technology specifications. “The advantages of EtherCat are well- known and include processing on-the-fly, comprehensive diagnostics, simple configuration and integrated synchronisation,” says Beckmann. “These attributes are, of course, fully retained when EtherCat G is used.” ETG accepts Beckhoff’s 10Gb/s version of EtherCat into its standard The automated EnergyVault gravity-based storage systemwill be particularly useful for delivering a steady, predictable outputs from intermittent sources such as solar andwind power An example of a network incorporating standard EtherCat, EtherCat G and EtherCat G10 segments for faster communications and greater data throughput. Image: Beckhoff Automation