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NETWORK / 29 / DECEMBER 2017 / JANUARY 2018 two elements, storing charged vanadium electrolyte (which is 70 per cent water) in tanks, which is then pumped through "stacks" that provide the power element. The set up is similar to an engine and fuel tanks, except the fuel never runs out, because vanadium electrolyte does not degrade, no matter how much you use it (unlike lead and lithium solutions). Flow machines are ideal for high-energy applications, requiring dis - charging or charging duration of three hours or more on a daily basis, which is what's required for time shi ing multiple hours of solar power or for providing all types of grid support services. Highlighting costs Another stumbling block in the energy stor- age industry is cost. The standard industry metric, using price per kilowatt hour, does not take into account all of the costs in- volved. To get a comprehensive understand- ing of the cost of storage, we need to look at levelised cost of storage – which takes into account how you will use the system and the resulting effect on elements such as maintenance, depreciation and replacement costs. Energy storage, especially at grid level, needs to be thought of as infrastruc - ture, in just the same way as pylons, cabling and substation equipment – it needs to last for 25 years or more in order to provide all grid services - and it needs to create an investable, attractive return. This is what's termed a "flexible platform asset" and that's what a flow machine provides, as opposed to being a consumable like a conventional battery. However, there is no one panacea tech - nology when it comes to energy storage. We recently announced a hybrid energy storage project, which combines flow machines with lithium technology. Because flow machines address the weaknesses of conventional, power-centric batteries, this solution can ac - commodate short term power spikes as well as longer duration, energy-focused needs. By using a flow machine as a workhorse, cover- ing 60-80 per cent of the work on a daily basis, with lithium batteries being employed to cover occasional peaks, the lithium usage can be carefully managed to prolong its life, whilst providing the short sharp bursts of power that the site requires. Energy storage is the key to solving the energy trilemma of access, affordability and de-carbonisation. Renewable energy can be deployed centrally as baseload generation or on a decentralised basis, behind the meter as part of a smarter, more flexible energy system. The future is energy and storage is at its heart, so make sure you select the right technology for your needs. CASE STUDY UK'S LARGEST FLOW BATTERY SYSTEM CONNECTED TO GRID The Hawkey family runs a 600-acre farm and 28-cottage holiday retreat called The Olde House in Wadebridge, North Cornwall. Their agri-business is grid-connected and has a peak demand of over 100kW. The site has traditionally been an early adopter of new renewable energy generating technol- ogy and to help offset costs, generates its own electricity from an on-site 350kWp solar array. Much of the site's energy use occurs during the evening and at night (when guests return to their cottages and start cooking dinner, etc.) Therefore, in order to make the most of their solar generation and to avoid peak electricity costs, the site needs to store excess solar generation produced during the day for use at night. We call this "firming" solar. redT's Vanadium Redox Flow Machines are ideally suited to this situation. As excess solar needs to be stored over a long period during the day and discharged over a long period during the night, liquid energy storage machines, such as redT's, don't degrade and are therefore ideal. In addition to making savings by utilising their own generation instead of importing from the grid, The Olde House will also be able to generate useful revenue by provid- ing grid services to the local network and trading energy as part of Centrica's Local Energy Market project. redT are the first storage technology to be signed up to this scheme, which will allow asset owners to take control of their energy use and trade excess generation with both the grid and each other. redT's machines are flexible platform assets, which means they can be used to perform different services at different times, depending on what provides the greatest net benefit to the asset owner. In this context, The Olde House can use the machines to engage in frequency response services, bid into the capacity market and engage in merchant energy trading and arbitrage activity. Importantly, because these machines don't degrade, layering on new services or changing what activities the machine performs, does not have an associated cost in terms of degradation. Holiday cottages at The Olde House site. redT energy storage machines at The Olde House.