Green software: less energy = less CO2 emission

This is blog 10 in a series about Green IT.

​​ Imagine you download a new app, and suddenly your battery runs out much more quickly than previously. The cause: poorly programmed software. This is, in miniature, what also happens on a grand scale: in data centres and on the internet. Poorly programmed or incorrectly used software contributes to the ICT sector’s carbon footprint. How? We will explore this in the coming blogs about green software. This blog is the first on this new theme.

Green software engineers

Green software is a growing field uniting climate science, software design, energy issues, hardware and data centre design. (1) A growing number of software engineers is focused on encoding or modifying existing software to reduce both energy consumption and the corresponding CO2 emission. We deliberately use the term ‘software engineers’ here instead of ‘software developers’, because software can be greened permanently, and not just at the stage of new development. (2)

Green software engineers not only concentrate on programming software, but also examine the impact of software on the entire chain, including the used hardware and users’ experiences.

Learning and developing together

This is the mission of the Green Software Foundation (GSF), established in 2019, with which some 58 organizations and almost 1100 software engineers are currently affiliated. Together they research the development and sharing of best practices, including the use of relevant tools. They also offer cost-free training courses (in English) to help others understand green software development. (3,4)

Using green software can lead to reducing the total energy consumption by up to 60%. So it pays to invest in this. The efforts are based on six principles that form the foundation of GSF’s mission. The coming series of blog posts about green software will further explore these six principles.

Principle 1 – Carbon efficiency: ‘Emit the least amount of carbon possible.’

The first principle of green software is a simple one: to prevent is better than to cure. The goal is to create software with the least possible CO2 emission and with a special focus on carbon efficiency, so that users get the same value with less emission.

People often don’t realise that an entire chain lies concealed behind the use of electricity. Electricity is something taken for granted: you insert your plug in a socket and ‘it’ is simply there. Until recently, many people did not realise that generating electricity using fossil fuels is one of the most polluting processes with a vast amount of CO2 emission. Fortunately, societal awareness is growing on this point, driven by the energy and climate crisis.

Although 40% of the energy used in the Netherlands is now green (and that percentage is continuing to grow), 60% continues to be generated using fossil fuels such as coal and gas. (5) This forms the main source of CO2 emissions and contributes significantly to climate change. Combating climate change therefore demands concerted efforts to reduce the emissions. As we saw in the first blog about Green IT, there is a direct relationship between CO2 emission and energy consumption. So if we want less CO2 emission, we need to find ways to actively reduce our energy use.

Principle 2 – Energy efficiency: ‘Use the least amount of energy possible.’

Energy use and CO2 emission are directly correlated: if you use less energy, you also emit less CO2. That is why the principles of carbon efficiency and energy efficiency are closely connected and in fact are aimed at the same goal.

When seeking software that uses the least possible energy, you can look at two aspects:

(1) energy proportionality: how can I use my computer’s capacity as efficiently as possible;

(2) static power use: how can I make sure my computer uses the least amount of power at times when it is not being used.

Energy proportionality: ‘Use your equipment in the most optimal way possible’

Energy proportionality, introduced by Google engineers in 2007, measures the relationship between a computer’s power consumption and the speed at which the work is performed. The consumption shows how much of the computer’s computing power and memory capacity is actually used. An active computer that fully uses its capacity will show a high percentage, while an inactive computer with minimum use of computing and memory capacity will show a low percentage.

The relationship between capacity and use is not linear. For instance, an inactive computer can use 100 Watt, at 50% activity it uses 180 Watt, and when fully used it may use 200 Watt. It means that, the more a computer is used, the more efficiently it converts electricity into actual computer operations. This fundamental principle also lies at the basis of the energy economy of large data centres. Energy efficiency is optimised when the servers operate at maximum capacity.

Static power use: ‘A computer also uses power in standby mode.’

The second aspect concerns the power use of an inactive computer. For example: if you’re working on a Word document and then pop off to get some coffee, the programme continues to use power in the background.

That’s precisely why computers have an energy-saving mode. When the device is inactive, it switches to sleep mode. The screen goes dark and the computer use less energy. But even in stand-by mode the computer still uses one third of its normal use. Since this mode equals some 260 kWh on a yearly basis, it is advisable to completely power down a computer after use. (6)

Servers also have an energy-saving mode, known as the ‘savings mode’. The Netherlands Enterprise Agency promotes the use of this mode on its website, as it can achieve direct energy savings of 10%. (7) Still, the energy saving mode is often not used in practice. An often-cited reason is that servers need to be able to respond rapidly to changing commands. Using the savings mode can adversely impact user’s ease, as users need to wait longer for the system to start up again.

Conclusion

In this blog we introduced you to green software. The Green Software Foundation plays an important role in sharing and promoting research in this field. It works on the basis of six principles to develop new software and to modify existing software.

In this blog we took a closer look at the first two principles, concerning carbon and energy efficiency. Both have the same goal: a lower energy use to reduce CO2 emission. Software engineers have two ways of doing so: to reduce static energy use at times of inactivity (using the energy-saving mode), and optimising the use of computing and memory capacity during active use.

In the next blog we turn our attention to the principles of CO2 awareness and the corresponding options.

Sources

(1) Taken from the Green Software Foundation website: https://greensoftware.foundation/articles/what-is-green-software

(2) In his podcast series, ‘World Wide Waste’, Gerry McGovern (also author of the same-titled book) interviews Hannah Smith about ‘The Hidden Weight of Code’. Among other things, they address the confusion that would arise if we were only to refer to software developers.

(3) Green Software Foundation, 'Free learning course: Green Software Practitioner', available at https://learn.greensoftware.foundation

(4) These principles are shared by Microsoft, which has also developed a cost-free course that covers these principles. This course can be followed at https://learn.microsoft.com/en-us/training/modules/sustainable-software-engineering-overview/. Particularly the course’s brief explanatory videos are of great value.

(5) Statistics Netherlands (CBS), ‘Aandeel hernieuwbare elektriciteit met 20% gestegen in 2022’, published on the CBS website on 6 March 2023.

(6) United Consumers, 'Stroomverbruik computer: Dit is wat uw computer jaarlijks verbruikt'. Last consulted on 23 November 2023.

(7) RVO, 'Energie besparen datacenters', published on 17 May 2021.