Green IoT design is an IoT design paradigm based on a holistic IoT design framework that focuses on maintaining a balanced trade-off between the functional requirements, Quality of Service (QoS), interoperability, Cost, security, and sustainability within the IoT ecosystem. It emphasises the need to prioritise energy efficiency and the reduction of waste in the IoT ecosystem from manufacturing IoT devices, deployment of IoT systems and operation of IoT systems.

The emergence of modern technologies such as Fifth Generation (5G) mobile networks, blockchain, Artificial Intelligence (AI), and fog/cloud computing are unlocking new IoT use cases in various industries and sectors of the modern technology-driven economy or society. As a result, the number of IoT devices connected to the Internet and the volume of traffic generated from IoT infrastructures will increase significantly, increasing the energy demand in the IoT ecosystem. The result is an increase in the carbon footprint and e-waste (especially from battery-powered IoT devices) from IoT-related services or the IoT ecosystem.

An effective green IoT strategy should span the entire IoT product lifecycle from the design to production (manufacturing) to the deployment, operations and maintenance, and recycling. The primary goal in each stage is to reduce energy consumption, adopt sustainable resources (e.g., harvesting energy from sustainable energy sources, using sustainable materials) usage, minimise e-waste and other pollutants, and adopt recycling of resource or waste. Therefore, a shift toward Green IoT (GIoT) emphasises the need to adopt energy-efficient practices and processes prioritising resource conservation, waste reduction, and environmental sustainability^[1].

Green IoT design is a design framework consisting of design, production, implementation, deployment, and operation choices to reduce energy consumption and waste from the IoT ecosystem. They are energy-efficient strategies devised to reduce the carbon footprint from manufacturing, deploying, and operating IoT systems (IoT sensor devices, networking nodes, data centres or computing devices). They are also strategies devised to reduce the waste from IoT infrastructures. They may involve hardware, software, management or policy decisions. The green IoT design framework should consist of the following design considerations: developing and deploying energy-efficient mechanisms, choosing energy sources, and mechanisms to ensure environmental and resource sustainability.

Energy-efficient design: It involves that design and deployment of energy-saving mechanisms to reduce the energy consumption of IoT devices. These mechanisms include the following:

1. Green computing: Energy-efficient strategies designed to minimise energy consumption or to maximise energy efficiency, decrease the carbon footprint from computing devices and processes in the IoT infrastructures (from the devices at the IoT layer to the computing servers at the fog computing servers).
2. Green communication and networking: Selecting energy-efficient technologies, products, practices designed to minimise energy consumption or to maximise energy efficiency, decrease the carbon footprint from networking and communication nodes in nodes and processes in IoT infrastructures (from the IoT access nodes, through the Internet core network to the cloud data centres).
3. Green security: Design and implementation of energy-efficient security algorithms to minimise energy consumption or to maximise energy efficiency in IoT infrastructures.
4. Green architectures: Designing and organising IoT and other ICT architures within the IoT infrastructure in such a way as to minimise energy consumption or to maximise energy efficiency.
5. Green hardware design: Design of energy-efficient hardware chips and devices (computing and networking nodes) to minimise energy consumption or to maximise energy efficiency and decrease the carbon footprint from computing and networking hardware nodes in IoT infrastructures. A significant amount of energy can be saved by designing energy-efficient chips and hardware devices. With the increased use of AI and blockchain in IoT applications, energy-efficiency at the hardware level becomes very essential.
6. Green software design: Optimimising software algorithms and programs to minimise energy consumption or to maximise energy efficiency and decrease the carbon footprint from software programs running of IoT infrastructure.

The above energy-efficient or sustainable computing, security, networking, hardware, and software design strategies can significantly reduce the energy demand from large scale IoT infrastructures deployed through out the world. Although, significant amounts of energy can be saved by applying these strategies, the rapid growth in the size IoT industry may offset these gains, but they offer a significant gain for the environment.

Design choices for energy sources The type of energy sources required to power IoT infrastructures varies from the IoT cyber-physical infrastructure to the core infrastructures. Electrical and electronics devices in the IoT infrastructure can be powered with energy from:

-main: Powering electrical and electronic systems within the IoT infrastructure using electricity from main power supply. It is suitable for power energy hungry devices like networking nodes and servers but not suitable for massive number of IoT devices, especially when the devices are suppose to be mobile. -energy harvesting: To reduce dependence on fossil fuel and other environmental unsustainable energy sources, renewable energy sources are used to power electrical and electronic systems within the IoT infrastructure. The kind of renewable energy source depend on the energy demand of the networking and computing nodes. For IoT devices, energy harvesters that can be scaled down to produce small amount of energy to power small IoT devices while larger energy harvesters that can produce larger amounts of energy are used to supply power-hungry computing and networking nodes. -energy storage: The energy storage systems that are used to stored energy in IoT infrastructure are battery energy storage system (BESS) and super-capacitors. Most IoT devices are often powered by small-sized batteries with limited amount of energy.

Environmental and resource sustainability mechanisms