Charged with the mission of finding more intelligent ways to consume less power, the flagship program’s Intelligent Energy team have pinpointed areas of demand – such as houses, office buildings and industry – in order to develop a group of very clever fridges that will help cut greenhouse gas emissions.

Sharing the load

The smart fridges are fitted with control technology that allows them to communicate with each other via a distributed network so they can share and store energy provided by renewable-powered generators.

As CSIRO engineer Sam West explains, “The fridges are designed to talk to each other, negotiating when it’s a good time to consume electricity and when it’s better not to. These scheduling decisions improve the quality of electricity produced by renewables and can help increase renewable uptake in the energy market.”

Rapid variations in electricity flow can destabilise the electricity grid and result in blackouts and other unwanted side effects. During the day, for example, supplies of electricity generated from photovoltaics can be interrupted by cloud cover resulting in periods of variable power supply.

To combat this, the fridges work together to decide when to cool down, and thus consume power, based on how much surplus power will be available. They are able to anticipate power shortages and change their running schedules accordingly to use as little power as possible during these times. Similarly, by reducing the amount of electricity required during peak demand periods, the need to build more network infrastructure is reduced.

Cool storage

Along with this ability to make intelligent scheduling decisions, the system also enables the fridges to use temperature difference as a form of thermal energy storage.

Essentially, a fridge makes food cold by removing the heat energy from food and the air around it to the outside of the unit. This creates a temperature difference between the inside and outside of the fridge, and explains why the back of a fridge gets hot. Left alone, this temperature difference between the cold inside and the warmer outside of a fridge will eventually equalise, but because this takes a certain amount of time, in the meantime it can be used as a form of thermal energy storage.

“The surplus electricity produced by solar panels can be used to lower the fridge temperature a few degrees more than necessary to create a thermal energy store which will keep the fridge’s contents cold during the night,” says Mr West.

The smart fridge does not consume any less electrical power than traditional units, but by storing energy, cooling down and switching off for a period, the times at which it operates can be synchronised to help level demand for intermittent green power generators like wind and solar farms.

A smarter energy pyramid – managing load, storage and consumption

According to the Intelligent Energy team – which has conducted successful large-scale simulations and laboratory trials of the technology – the smart fridges system is the first energy management model that can provide concrete feedback about how much power will be stored and consumed, as well as being able to match a particular requested load curve.

Other systems use the AC signal frequency on power lines as an indication of whether to turn off – because frequency variation is an indicator of grid load. However, this technology often has response characteristics that are difficult to quantify. The smart fridges, on the other hand, can relay their planned running schedules, and negotiate between themselves to achieve the optimal outcome.

“Using less electricity is always preferable to generating more and is the simplest way to reduce greenhouse gas emissions. Refrigeration can be very energy intensive but by harnessing renewable power this technology offers a low-emission solution to keeping food and other perishables cold,” explains Mr West.

Looking beyond fridges, the team believes that the same algorithms can also be applied to any household energy appliance – such as washing machines, dryers, dishwashers, hot water systems and air conditioners – that stores energy and can be turned on and off without any significant impact.