• • • ENERGY EFFICIENCY • • •


power in a turbine while simultaneously recovering the heat from the thermal storage. (Source: https://ease-storage.eu/wp-content/uploads/2016/03 /EASE_TD_ACAES.pdf)


4. PUMPED HYDRO


Pumped-storage hydropower (PSH) is classified as a hydroelectric energy storage that is configured with two water reservoirs at different elevations which generates power as water passes through a turbine and draws power from the water pumps recharge to the upper reservoir. PHS are characterised by two different capabilities, the first is an open loop connected to ongoing hydrologic connection to a lake and the second is where two reservoirs are separated from an outside water body. According to the US Government Office of Energy Efficiency and Renewable Energy “Pumped- storage currently accounts for 95 per cent of all utility-scale energy storage in the United States.”


5. TIDAL CURRENT


This renewable energy source is powered by the natural tidal activity of the ocean tides and currents. The movement is a type of kinetic energy, and the tidal power surrounds gravitational hydropower that uses water movement to push a turbine and generate electricity. The submerged turbines are similar design to miniature wind turbines. Vortices, whirlpools and eddies are common occurrences on almost every global coastline and are predictable and powerful


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movements. Tidal data centre projects under development include SIMEC Atlantis Energy ambition for a facility in Caithness, Scotland, powered by 80MW of tidal power. Other projects are proposed for construction near the shoreline in locations such as Atlantis Singapore, Hammerfest Strom Norway, MCT Northern Ireland, and Open Hydro Orkney Islands.


6. GRAVITY STORAGE


A gravity storage scheme involves a piston with millions of metric tons raised by water pressure to store energy. As the piston descends this pushes water through a generator to deliver electricity. Prototype gravity storage projects are being developed by firms such as Scotland based, Gravitricity. It is building a prototype 250kW gravity power unit using towers. It says its units could deliver peak power outputs of between 1 and 20 MW, function for up to 50 years with no loss of performance and deliver full power in under one second.


At the other end of the scale Gravity Storage concepts are based on the hydraulic lifting of a large rock mass using water pumps. The rock mass acquires potential energy and can release this energy when the water that is under pressure is discharged back through a turbine. According to Heindl Energy Gravity Storage a rock mass with a diameter of 250m would result in a storage capacity of 8 GWh, which is comparable to the largest pumped storage power station in Goldisthal, Germany (8.4 GWh). It says gravity


  


storage of this type is a concept with which unprecedentedly large quantities of power can be stored over long periods. The capacity of energy storage can be between 1 and 10 GWh, comparable to large Pumped Hydro Storage. (Source: https://heindl-energy.com/)


NEW POWER STORAGE, NEW POWER CHAIN


In the drive for Green House Gas abatement and net zero operation, every energy storage option at source, grid, switch, battery, UPS and generator back up in data centres is changing. The i3 Solutions Group and EYP Mission Critical Facilities Inc., (EYP MCF) collaboration on greenhouse gas abatement has issued the first in a series of white papers providing detailed technical analysis for data centre operators as they move to carbon net- zero operations. The new series of white papers aims to provide vendor-neutral decision-making support together with insights into the factors associated with the many technology options currently available to the sector for lowering the carbon footprint of data centre operations. Titled: “Infrastructure Sustainability Options and


Revenue Opportunities for Data Centres,” the first paper is available for download now, and covers how targets for reducing greenhouse gas emissions and increasing revenue-generating opportunities are not mutually exclusive objectives.


I3 SOLUTIONS GROUP i3.solutions


electricalengineeringmagazine.co.uk


ELECTRICAL ENGINEERING • JULY/AUGUST 2021 33


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