June 2019

47 www.drivesncontrols.com June 2019 GAMBICA SUPPLEMENT n HYBRIDISATION: A PROFITABLE DISRUPTIVE STRATEGY FOR ENERGY B usinesses are constantly looking for ways to reduce energy expenditure. One approach is to improve process efficiency, but a point is reached where further efficiency increases are no longer realistically possible. What then? Finding cheaper energy is one option, but the energy utilities are unlikely to oblige – at least not directly – so a more creative solution is needed. That solution is hybridisation. Hybridisation is characterised by a power system that has access to two or more independent sources of energy. The word “independent” is important – a power system that can be fed from either of two utility substations wouldn’t qualify, because it has two connections to the same energy source – the national grid. However, a power system that can source power from the grid and from, say, a solar panel installation, is definitely a hybrid system. Adding a renewable energy source to a power system will probably deliver savings but, if energy storage is also added, it’s possible to save even more money and to improve versatility. Typically, hybrid power solutions are used in “behind the meter” applications, such as peak shaving. Power systems must be designed to supply the maximum load safely, but this maximum demand will invariably be intermittent. This means the system’s power transformers are working below full capacity most of the time. Now consider a factory with a hybrid power system incorporating energy storage. The power transformers can be rated for the average load, with the battery making up the difference during periods of maximum load. This is peak shaving. In addition, many commercial supplies are priced on “maximum demand”, i.e. the utility charges for energy consumed and also for the maximum load the user puts on the supply system. Peak shaving enables energy users to reduce their maximum demand and the associated charge by supplying some of their peak energy needs from their batteries. Another option is storing energy when prices are low and releasing it when they are high, which reduces energy bills significantly. Some hybrid systems can also generate reactive power on demand, which improves power factor, saving both energy and money. In addition, the batteries can power the plant if the grid supply fails, potentially eliminating the need for a separate UPS installation. Hybrid power systems can even feed energy from the batteries back into the grid. The utility pays for this, offsetting energy bills. The technology for hybrid power systems is readily available. There have been big developments in batteries, with lithium-ion technology being a popular choice, although users with longer time period requirements may benefit from alternatives such as flow batteries. Batteries produce DC power, whereas commercial power systems usually need AC. The solution is to use standard inverters. These are more familiar as variable-speed drives that take AC power at supply frequency, convert it to DC (the DC link) and then convert it back to AC. The DC link can alternatively be fed from a battery and the inverter will convert the DC to AC at a frequency accurately matched to the grid. Inverters in hybrid power systems can also take power from the grid to top up the batteries. Danfoss inverters for hybrid systems use the same hardware as variable- speed drives, and this commonality means hybrid applications benefit from products proven in thousands of VSD applications. Considerable expertise is necessary to implement efficient hybrid power systems, so it’s advisable to choose a supplier with proven expertise. Danfoss is such a supplier and provides solutions complying with international grid codes. These are already delivering big savings in hundreds of applications. Disruptive technologies receive much attention, but many applications to which this epithet is applied are unworthy of the title. An exception is hybridisation. Hybrid power systems are a radical development: they deliver large cost savings while reducing environmental impact. So great are their benefits that it’s likely hybrid power systems will soon predominate. But there’s no need to wait! You can benefit from hybridisation right now – start today by contacting a leading inverter expert with proven hybrid expertise! n A disruptive new technology – hybridisation – is bringing big changes and impressive benefits to electrical power systems, argues Alan Baird of Danfoss Drives. Alan Baird

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