Experts: Ana Bendiek Laranjo (Empa), Hanmin Cai (Empa)
Building maintenance consumes vast amounts of energy – not just for heating and hot water, but increasingly for smart control systems too. However, old smartphones could be an innovative solution and, thanks to their computing power and communication capabilities, could soon help reduce grey emissions in the building sector. What started out as an experiment has the potential to revolutionise the future of building automation.
Picture: Anton Maksimov (Unsplash)
Maintenance and operation of Switzerland’s private, commercial and industrial building stock consumes around 90 terawatt hours of energy each year. This corresponds to approximately 40 percent of the country’s total energy demand. While the energy consumption for maintenance is decreasing with the increasing popularity of Minergie and passive houses, the share of grey energy in buildings is rising. Highly effective insulating materials and heat generation from renewable sources are inadequate if the net-zero target is to be achieved by 2050.
Smart building control is an essential part of the overall package. Self-learning algorithms operate buildings, taking their structural characteristics into account. External factors such as the weather and seasons are also incorporated into heating performance calculations. However, such control systems require hardware components with computing power and communication capabilities.
In 2022, 11 billion devices for smart building technology were in use worldwide. Manufacturing and transporting this hardware is both resource- and energy-intensive and simply shifts emissions from construction to other sectors. Hanmin Cai, Group Leader at Empa’s Urban Energy Systems Laboratory in Dübendorf, faces this problem every day in his work. At the same time, around 5 billion smartphones are thrown away worldwide each year – usually due to insufficient battery performance, a defective screen or upgrading to a newer model.
The story of Mr Cai’s idea begins during the COVID-19 lockdowns. He saw how global supply chains were disrupted and chips for smart building control systems were becoming difficult to obtain. At the same time, he had adequate time and inclination to throw himself into his collection of old smartphones. Each individual device represented a stage in the mobile researcher’s life, which is why he initially saw it as a fun pastime to connect the old smartphones using algorithms he developed all by himself and combine the individual stages of his life into a single whole. And then the experimentation led to a pioneering project aimed at answering one key question: Can old smartphones be used as control units for smart building automation? Mr Cai describes his accidental discovery as follows: “I was fascinated by the computing power and communication capabilities of outdated smartphones and began integrating them into my daily work, focusing on energy management in the experimental NEST building at Empa.” He soon discovered that devices manufactured in 2018 or later had sufficient computing power and communication capabilities to serve as such control units.
He loaded algorithms he had co-developed onto one of his old smartphones using open-source software to control the temperature in a room of the NEST building. The phone collected and analysed incoming data from the building and its surroundings. The device then forwarded corresponding instructions to the building, the heating system, the boiler, the building battery, the lights and the blinds. And it actually worked. Mr Cai demonstrated that the smartphone’s performance in terms of accuracy and communication speed was sufficient for building control purposes. This discovery was a highlight of the pioneering project.
The beauty of this approach is that smartphones do not have to be dismantled for use in building control. To perform their task, they are simply connected to the power supply and communication networks. A broken screen or a low battery does not interfere with this, which keeps costs low and has the added benefit that the product warranty remains valid. Experience has shown that a single smartphone is enough to control a single-family home, so most households would have the resources to control their buildings.
Despite the successes and resources that are abundantly available, the idea is still in its infancy. For scaling and use by end users, a kit that serves as an interface between the smartphone and its environment and packs away all the loose cables must be developed. Although they may well serve their purpose in a laboratory, they are not good enough for commercial use.
There are also some important questions that still need answering – such as software security and the lifespan of such a smartphone installation. Last but not least, a comprehensive lifecycle analysis is absolutely essential. Do reused smartphones actually perform better than newly manufactured control units in terms of the emissions generated? Initial results are promising, even when emissions from the smartphone’s manufacture for its primary purpose are taken into account.
The team is not short on inspiration, either. And for Mr Cai, who leads the project, one thing is clear: “The greatest benefit lies in a change of mentality and in the fact that the issue of rising grey emissions in increasingly energy-efficient buildings is becoming more visible.” He believes that stationary applications requiring little effort outside of building automation are also conceivable, including the likes of robot vacuum cleaners, self-service checkouts in supermarkets, ticket systems in car parks or charging stations for electric cars. In other words, applications where data is processed in the background and appearance is secondary. So, to sum the situation up, it looks as though smartphones are on the verge of getting a second lease of life.
