Clean energy: advantages and types

The transition towards a more sustainable energy system is one of the most pressing challenges of our time. At the heart of this transformation lies the concept of clean energy: a category encompassing all those sources capable of producing energy while minimising pollutant emissions and climate impact, in stark contrast to fossil fuels that have powered industrial development over the past two centuries.

Understanding what clean energy is, what its main clean energy sources are, and how technologies are evolving to make it increasingly accessible and efficient is essential for anyone wishing to navigate the contemporary energy debate – whether as a citizen, a business, or an investor.

What is clean energy?

Clean energy encompasses all forms of energy produced from renewable sources – sun, wind, water, geothermal heat – that emit negligible or zero greenhouse gases throughout their production cycle. It differs from fossil fuels in that its sources regenerate naturally and do not disturb the planet’s climate balance.

The concept of clean and sustainable energy goes beyond the mere absence of emissions at the point of production. An energy source is truly sustainable when it accounts for the entire life cycle – from the manufacturing of plants to their final disposal – and when it is compatible with the long-term availability of natural resources. In this sense, clean and affordable energy is also energy that can be distributed equitably, at progressively declining costs, reaching communities and populations still dependent on polluting sources or lacking stable access to electricity.

Globally, the sector is growing at a sustained pace. According to data from the International Renewable Energy Agency (IRENA), in 2023 installed capacity from renewable sources exceeded 3,000 GW worldwide for the first time, with solar photovoltaic and wind as the leading technologies. In Europe, the REPowerEU plan has further accelerated renewable energy penetration targets, with a goal of at least 42.5% of energy from clean sources by 2030.

Clean energy sources

The clean energy sources available today are numerous and continuously evolving. Each has specific characteristics in terms of potential, geographical distribution, costs, and technological maturity.

The main ones are:

Solar energy

Harnesses solar radiation through photovoltaic panels (converting it into electricity) or concentrated solar power plants (producing heat to generate steam). It is the renewable source with the fastest declining installation costs: the cost of photovoltaics has fallen by more than 90% over the last decade, according to IRENA.

Wind energy

Converts the force of wind into electricity via turbines installed both on-shore (on land) and off-shore (at sea). Offshore installations are recording strong growth thanks to more consistent winds and lower territorial opposition: the Hornsea Two wind farm in the North Sea, with a capacity of 1,320 MW, is among the largest in the world.

Hydroelectric energy

The historically most widespread renewable source, it harnesses the flow of water to drive turbines. It still accounts for approximately 15% of global electricity production, with plants ranging from large dams such as the Three Gorges Dam in China (22,500 MW) to small installations on local waterways.

Geothermal energy

Draws on natural heat from the Earth’s interior. Particularly effective in volcanic and tectonically active areas, such as Iceland – which meets almost 100% of its electricity needs from geothermal and hydroelectric power – or Tuscany, home to the world’s oldest geothermal plant, Larderello, in operation since 1904.

Biomass energy

Derived from the combustion or chemical transformation of organic materials – agricultural waste, forest residues, municipal solid waste. It can produce electricity, heat, or biofuels, and is particularly relevant for the production of biomethane, a renewable gas that can be fed directly into existing distribution networks.

Green hydrogen

Produced through the electrolysis of water powered by renewable energy, green hydrogen is considered one of the energy carriers of the future, capable of decarbonising sectors that are difficult to electrify, such as heavy industry, long-distance transport, and heating.

Marine energy

Harnesses tides, currents, and wave motion. Still in the large-scale development phase, it holds enormous potential in coastal areas, with pilot projects already underway in Scotland, France, and South Korea.

Environmental impact of renewable energy

One of the strongest arguments in favour of clean and sustainable energy is the direct comparison with fossil fuels in terms of CO₂ emissions per unit of energy produced. Data from the IPCC (Intergovernmental Panel on Climate Change) illustrates the difference clearly:

Beyond climate-altering emissions, clean energy sources offer broader environmental benefits. The absence of fossil fuel extraction and combustion dramatically reduces local air pollution – with direct positive effects on the health of populations, especially in urban areas. The World Health Organisation estimates that air pollution caused primarily by fossil fuel combustion results in approximately 7 million premature deaths per year worldwide.

It should be noted that renewables also have an environmental impact, albeit far smaller: the production of solar panels requires rare raw materials and energy-intensive industrial processes, wind turbines can interfere with local wildlife, and large hydroelectric dams alter river ecosystems. The challenge is to manage this transition responsibly, minimising negative externalities and ensuring that the development of renewables respects biodiversity and local communities.

Technologies for clean energy production

The growth of clean and renewable energy is closely linked to the evolution of the technologies that make it possible, efficient, and competitive with fossil fuels. Over the past twenty years, technological progress has transformed sectors that once seemed niche into pillars of the global energy system.

In solar energy, first-generation photovoltaic technology based on crystalline silicon has reached efficiency levels unthinkable just a few years ago, exceeding 23% in commercial modules and approaching 30% in research cells. In parallel, thin-film panels and perovskite cells are gaining ground, promising further reductions in production costs and applications on flexible or transparent surfaces – such as building facades and windows.

In the wind sector, innovation focuses on increasing turbine size – blades up to 120 metres long are now being manufactured – and on the development of floating offshore wind, which enables installations in deep waters where winds are stronger and more consistent. The Hywind Tampen project in Norway is the world’s first floating wind farm designed to power offshore oil platforms, reducing their emissions by 35%.

Energy storage systems are playing an increasingly central role, essential for overcoming the intermittency typical of solar and wind. Lithium battery costs collapsed by 97% between 1991 and 2021, making large-scale energy storage competitive. Alongside batteries, alternative technologies are being developed, including pumped-storage hydropower, fuel cells, and thermal storage systems, each with different characteristics in terms of capacity, response speed, and lifespan.

For the distribution of clean energy, intelligent grids – the so-called smart grids – represent the enabling infrastructure of the energy transition. Through sensors, artificial intelligence algorithms, and advanced control systems, smart grids optimise energy flow in real time, integrate distributed production from renewable sources, and enable the active participation of consumers – who become “prosumers”, capable of producing and supplying energy back to the grid.

Innovations in the sustainable energy sector

The sustainable energy landscape is evolving rapidly, with innovations redefining not only production technologies but the entire way the energy system is conceived. Some of these trends are already operational realities; others are still in an experimental phase but set to mature rapidly in the coming years.

Green hydrogen is perhaps the most discussed frontier. Produced by water electrolysis powered by renewable energy, it can be transported through existing gas networks – with appropriate adaptations – and used as fuel in sectors difficult to electrify. The European Union has set a target of 10 million tonnes of domestically produced renewable hydrogen by 2030, and several countries – including Germany, Spain, and Italy – are investing in production hubs and transport corridors.

Nuclear fusion represents another frontier: unlike fission, it produces energy without long-lived radioactive waste and with virtually unlimited resources (deuterium and tritium, extractable from water). In December 2022, the American National Ignition Facility achieved for the first time in history a net energy gain from fusion – producing more energy than was used to trigger the reaction – opening a concrete prospect, even if still far from commercialisation.

On the distributed generation front, renewable energy communities (RECs) are changing the paradigm of electricity generation: groups of citizens, businesses, and local authorities come together to produce, share, and sell energy from renewable sources at a local scale. In Italy, the transposition of the European RED II directive has paved the way for the expansion of RECs, with both economic benefits – reduced energy bills – and social benefits, fostering the active participation of communities in the energy transition.

Finally, the digitalisation of the energy system – through artificial intelligence, digital twins, and blockchain – is enabling increasingly granular and optimised management of energy flows. Digital twins of distribution networks, for example, allow real-time simulation of supply and demand scenarios, anticipation of faults, and more precise investment planning, reducing waste and operating costs.

The main innovative trends that will characterise the energy sector in the coming years can be summarised as follows:

• Scaling and integration of green hydrogen into existing transport and distribution networks, as a carrier to decarbonise heavy industry and heating.
• Next-generation storage systems: solid-state batteries, thermal storage, and iron-air systems, to overcome the intermittency limitations of renewables.
• Floating offshore wind and space-based solar: technologies to harness energy resources currently out of reach, with enormous potential in areas with high solar irradiance or high wind speeds at sea.
• Energy communities and prosumers: distributed generation models that bring production closer to consumption points, increasing system resilience and reducing network losses.
• Artificial intelligence for grid management: predictive algorithms that optimise energy distribution in real time, reduce faults, and intelligently integrate the variable output of renewables.

The transition towards clean and affordable energy is neither a linear path nor one free of challenges: it requires substantial investment, continuous technological innovation, infrastructure adaptation, and governance capable of accompanying change without leaving territories or social groups behind. But the direction is clear, and the technologies needed to pursue it are largely already available. For companies managing energy networks and infrastructure, actively contributing to this transition – modernising plants, enabling the transport of new carriers such as biomethane and hydrogen, investing in digitalisation – is not merely a strategic choice: it is a responsibility towards future generations.