What is the energy source of the future?
- Wolfgang A. Haggenmüller
- Oct 1
- 23 min read
The global demand for energy is rising continuously. Increasing electrification, especially through electromobility, heat pumps, digitalization and industrial processes, requires a fundamental change in energy supply. The goal is a climate-neutral, sustainable and reliable energy future.

Introduction
The question of the future energy source is central to the 21st century. The energy industry is facing enormous upheavals: global energy demand is growing, while at the same time decarbonization, i.e. the drastic reduction of CO₂ emissions, must be promoted. According to the International Energy Agency (IEA), electricity demand will almost triple by 2050, not least due to the electrification of mobility, heating and industry. The Intergovernmental Panel on Climate Change (IPCC) and numerous climate researchers such as Prof. Hans Joachim Schellnhuber emphasize that a complete move away from fossil fuels is necessary by the middle of the century at the latest in order to limit global warming to below 1.5 °C. But where should the clean energy come from? Not only from the 'socket', but from technologies and resources that are efficient, sustainable, economically and socially accepted. In this study, we comprehensively analyze all relevant energy sources: fossil, nuclear, renewable, and synthetic. In doing so, we look at them in terms of their environmental impacts, CO₂ balance, sustainability, costs, storability, acceptance, future viability and political framework conditions.
The increasing demand for energy in the 21st century
Global energy demand is growing steadily – driven by industrialization, population growth, digitalization and increasing electrification. According to the International Energy Agency (IEA), global electricity consumption will almost double by 2050. This poses enormous challenges for energy infrastructure and generation and requires a profound transformation of energy systems.
Energy hunger of a growing world population
In 2023, over 8 billion people lived on earth. By 2050, the UN expects this to rise to around 9.7 billion. In Africa and Southeast Asia in particular, not only the population is growing, but also the demands on prosperity, mobility and infrastructure. This leads to a rapid increase in per capita energy consumption in these regions.
According to the World Energy Outlook 2023, fossil fuels accounted for about 80% of global primary energy consumption in 2022 – especially oil (29%), coal (27%) and natural gas (24%). This dependence is associated with massive CO₂ emissions: the energy sector was responsible for around 73% of global greenhouse gas emissions in 2022 (UNEP, 2023).
Electrification of industry, mobility and heat
Electrification is a major driver of future energy demand. Electricity demand is rising rapidly, especially in mobility (electric cars, rail transport), industry (electrical process heat, electrolysis) and in the building sector (heat pumps).
Electromobility: The number of e-vehicles registered worldwide more than tripled between 2018 and 2023. According to BloombergNEF, over 50% of new registrations are expected to be electric by 2030.
Building heat: The use of heat pumps, especially in Europe and China, is increasing sharply. They are increasingly replacing oil and gas heating systems.
Industry: Electricity-based technologies (e.g. electric arc furnaces, electrolysers) are being developed to decarbonise energy-intensive sectors such as steel, chemicals or cement.
Digitalization and Data Centers
Advancing digitization also contributes to the hunger for electricity. Cloud services, artificial intelligence, cryptocurrencies, and the Internet of Things (IoT) are driving the need for data centers. According to a study by the IEA (2024), data centers, data transmission networks and AI models could account for up to 8% of global electricity consumption by 2030 – more than all of Germany's demand today.
The energy demand of the future: forecasts
Scenarios from the International Renewable Energy Agency (IRENA) assume that global primary energy demand will increase by 25–30% by 2050 – even under ambitious climate targets. Not only the quantity, but also the structure of demand changes:
More electricity: The share of electrical energy in final energy consumption will increase from currently around 20% to over 50%.
More flexibility: Demand-oriented load management is becoming more important in order to compensate for fluctuating feed-in from the sun and wind.
More storage: The demand for energy storage (batteries, hydrogen, thermal storage) is growing exponentially.
According to the IEA, global primary energy demand was around 620 EJ in 2023 (~598 EJ 2018; ~505 EJ 2010) According to BP Outlook, installed energy capacity (wind, solar, hydro, nuclear) will grow 8 to 14 times from now until 2050. In its baseline scenario ("Current Trajectory"), the BP Energy Outlook 2024 assumes an increase in primary energy from ~627 EJ today to approx. 692 EJ 2050
Global energy demand is rising continuously from about 520 EJ (2000) to an estimated 780 EJ (2050). Installed capacity is growing disproportionately and theoretically significantly overtakes demand – through efficiency, renewable energies, growth in power plant capacity. This leads to a surplus of generable power, which BP cites as the reason for rising emissions despite expansion.

The apparent exceeding of the installed capacity compared to the primary energy demand in the BP Net Zero scenario is due to a fundamental change in the energy system – in particular due to the following three factors
🔌 Electrification & Energy Losses in Conversion
In a fossil system, a lot of primary energy is "burned" to generate electricity or heat (with typical efficiency ~35–40%).
In the case of direct electricity use (e.g. through heat pumps, e-mobility), the efficiency is much higher (e.g. 90% for e-cars vs. 20-25% for combustion engines).
This means that you need much less primary energy if you provide the same service electrically – but more installed power generation capacity.
🌞 2. Renewables have low capacity factor
Solar and wind plants have low full load hours:
PV: approx. 10–25 % capacitance factor
Wind: approx. 25–45 %
This means that in order to provide a certain amount of energy, you need many times more installed capacity compared to base-load power plants such as gas or nuclear.
As a result, the installed capacity is increasing dramatically – without the same increase in final energy consumption.
🔋 3. Integration: Storage, Power-to-X, Grid Losses
Renewable energies need more grid capacity, storage and backup power.
Power-to-X solutions (e.g. hydrogen from electrolysis) also increase electricity demand beyond conventional demand – even if the end use is more efficient.
These additional requirements are included in the installed capacity, but not in the primary energy consumption.
📊 Result
The discrepancy is therefore not a contradiction, but the consequence of structural change:
From a loss-making fossil system (a lot of primary energy, little usable energy)
Towards an efficient but capacity-intensive renewable system
Overview of energy sources
Energy sources can be divided into four main groups. These differ in efficiency, emissions, availability and acceptance.
· Fossil fuels: coal, oil, natural gas
· Nuclear energy sources: classic nuclear energy, new types of reactors
· Renewable energies: solar energy, wind power, hydropower, geothermal energy, biomass, ocean energy
· Synthetic energy carriers and storage: hydrogen, batteries, power-to-X, CCS
3. Fossil fuels: coal, oil, natural gas
Fossil fuels are carbon-intensive, finite, and cause environmental problems such as air pollution and climate change. International energy agencies see their share falling to below 20% by 2050.
Fossil fuels – coal, oil and natural gas – formed the backbone of the world's energy supply for over a century. As recently as 2023, around 80% of the world's primary energy came from fossil sources (IEA, World Energy Outlook 2023). They are stored in geological deposits and were formed by millions of years of conversion processes of organic substances. The use of fossil fuels is associated with considerable CO₂ emissions: When burned, greenhouse gases are released, which contribute significantly to global warming.
Significance and historical role
Fossil fuels – coal, oil and natural gas – shaped the global energy supply for over 150 years. The beginning of the industrial age in the 19th century was based on coal, later crude oil became the central fuel for mobility and industry, while natural gas was increasingly added as a source of heating and electricity in the 20th century.
As recently as 2023, the global share of fossil energy sources in primary energy supply was around 79% according to the International Energy Agency (IEA) (World Energy Outlook 2023). They continue to dominate, especially in countries such as China, India, Russia and the USA – for reasons of availability, infrastructure and low costs in the short term.
"Without a complete phase-out of fossil fuels by 2040, the global climate goals will not be achievable." — Dr. Fatih Birol, Executive Director of the IEA (2023)
Technological characteristics and use
Coal: Available in different qualities (lignite and hard coal), mainly used in power generation. Extremely CO₂-intensive, with emissions between 820–1,050 g CO₂/kWh (IPCC, 2023).
Petroleum: Mainly used in transportation, petrochemical and industrial. Flexible in use, but not directly suitable for power generation.
Natural gas: Discussed as a "bridging technology", good controllability, relatively low CO₂ emissions (approx. 410–650 g CO₂/kWh), but problematic methane losses.
Environmental impacts and climate balance
The use of fossil fuels is the main cause of anthropogenic climate change. According to the IPCC Synthesis Report (2023), about 73% of all global greenhouse gas emissions come from the burning of fossil fuels. In addition, there are:
Air pollution (particulate matter, NOx, SO₂)
Water pollution (e.g. during fracking)
Landscape destruction (e.g. open-cast mining)
Methane leaks (especially during natural gas production)
"A large part of the health burden of air pollutants in urban areas can be traced back to fossil fuel combustion." — The Lancet Countdown Report on Health and Climate Change (2022)
Economy
In the short term, fossil fuels often appear cheap – especially in countries with existing infrastructure. However, external costs such as environmental and health damage are often not priced in:
UBA (2020): External costs of coal-fired power generation in Germany: up to 18 ct/kWh
CO₂ price EU ETS (2024): over 80 €/t CO₂, and rising
A switch to low-carbon technologies is becoming increasingly economically attractive due to government pricing of fossil emissions (e.g. ETS, CO₂ tax).
Storability and system flexibility
Fossil fuels are inherently storable, storable and transportable. This makes them particularly suitable for:
Grid stabilization
Base load and peak load coverage
Buffering seasonal fluctuations
In a system with many renewable sources, their flexibility is still considered necessary to some extent today – a role that is to be replaced by hydrogen and storage solutions in the future.
Political and social acceptance
Social acceptance is declining rapidly in many OECD countries, especially for coal (e.g. Germany, France, Sweden).
Politically , fossil fuel projects are increasingly being stopped or definanced:
G7 resolution 2021: No more money for fossil foreign investments
EU taxonomy: Only sustainable investments eligible for funding
UN Climate Change Summit COP28: Global phase-out path for coal announced
Nevertheless, there are counter-movements by interest groups, producing countries and state-subsidised energy markets.
Future viability and global scenarios
In the ambitious climate scenarios (e.g. IEA Net Zero by 2050, Agora Energiewende, Shell Sky 2050), the fossil fuel share of the energy mix in 2050 will be less than 10%, in particular limited to "residual applications" (steel, aviation, petrochemicals).
Nevertheless, many analysts see transitional phases in which natural gas with CCS (Carbon Capture and Storage) or H₂ blending temporarily remains.
"The fossil era is coming to an end – not because of a shortage of resources, but because of climate limits." — Prof. Volker Quaschning, HTW Berlin

Nuclear Energy and Small Modular Reactors (SMR)
Nuclear energy offers low-carbon power generation, but is controversial because of risks, high costs and unresolved final storage. Countries such as France and China continue to rely on them, while Germany is exiting.
Nuclear energy is one of the most controversial energy sources. It uses the splitting of uranium or plutonium nuclei to generate large amounts of thermal energy, which is used to generate electricity. There are no CO₂ emissions during operation – which makes them attractive as a temporary solution for some experts from a climate policy perspective.In 2023, according to the International Atomic Energy Agency (IAEA), around 10% of the world's electricity came from nuclear energy. France covers more than 70% of its electricity needs with nuclear power. In countries such as Germany, Austria or Italy, on the other hand, a complete phase-out has taken place or is planned. Social acceptance varies greatly.
Small Modular Reactors (SMR) are new, more compact reactor types with a capacity of less than 300 MW. They promise lower construction costs, higher safety through passive cooling systems and better integration into decentralized grids. Canada, the United States and Finland are actively investing in their development. Critics, however, warn of unresolved questions about nuclear waste, the search for a repository and proliferation risks.
The carbon footprint of nuclear energy is very low at around 12–30 g CO₂/kWh (IPCC, 2022). However, there are long-term environmental risks from the radioactive waste, which must be stored safely for hundreds of thousands of years. Safety risks in the event of serious accidents such as those in Chernobyl (1986) and Fukushima (2011) also have a negative impact on political acceptance.
Nuclear energy is controversial economically: construction times of 10–15 years, high investment costs (over €10 billion per reactor) and high insurance costs make new projects in Western countries hardly feasible without massive government funding (Agora Energiewende, 2023).Conclusion: Nuclear energy offers climate-friendly power generation, but high risks and social rejection limit its future viability. SMRs could play a niche role, but they will not play a major role in the global energy transition.
Renewable energies – sun, wind, water, biomass, geothermal energy
Photovoltaics, wind energy, hydropower, bioenergy and geothermal energy are inexhaustible, climate-neutral and increasingly economical. According to IRENA, they could account for over 80% of the global electricity mix by 2050.
Renewable energies are considered the backbone of the future energy supply. They are based on natural, virtually inexhaustible sources such as sunlight, wind, water, plant biomass and geothermal energy. Unlike fossil or nuclear energy sources, they emit no or only small amounts of CO₂ during operation and are therefore essential for a climate-neutral future.
According to the Global Energy Monitor (2024), over 450 GW of renewable energy capacity was newly installed globally in 2023. In particular, the expansion of photovoltaics (PV) and wind power is experiencing exponential growth. In countries such as Denmark, Norway and Costa Rica, more than 90% of electricity already comes from renewable sources.
Solar energyPhotovoltaic modules convert sunlight directly into electricity. The efficiency of modern modules is 20–23%. In sunny regions, electricity generation costs (LCOE) of less than 2 ct/kWh are achievable (IEA 2023). The environmental balance is very good – CO₂ emissions are 20–70 g CO₂/kWh, depending on the origin. Recycling and the use of resources (e.g. silicon, silver) remain challenges, but the circular economy is constantly improving.
Wind EnergyOnshore and offshore wind turbines are the second largest source of renewable electricity. They have a carbon footprint of only about 10–20 g CO₂/kWh (UBA, 2022). Offshore wind farms offer great potential, but are associated with higher construction and maintenance costs. Land acceptance is a challenge in densely populated regions, although modern plants become more efficient and quieter through repowering.
HydropowerThis established technology supplies around 16% of the world's electricity. However, large reservoirs cause significant interventions in ecosystems and social structures. Small hydropower plants are more ecologically compatible, but less efficient. The CO₂ balance is around 24 g CO₂/kWh. In emerging countries, hydropower is often also used to control the water supply.
BiomassBioenergy can be produced by combustion, gasification or fermentation of plant raw materials. Their CO₂ balance is only neutral if replanting is ensured. It is particularly suitable for process heat and biofuels, but is controversial due to competition for land with food production. Emissions of particulate matter or nitrogen oxides are also an issue.
Geothermal energyDeep geothermal energy can supply heat and electricity via geothermal power plants – especially in geologically active regions such as Iceland or Indonesia. Near-surface geothermal energy is suitable for heat pumps. The technology is base-load capable, but expensive and locally limited. In Germany, the BMWK specifically supports geothermal projects with regional heat supply.
Conclusion: Renewable energies perform best in almost all sustainability criteria. Their biggest challenge lies in weather-dependent availability (volatility), which makes modern storage technologies, grid integration and sector coupling necessary. In addition, high investments are required in the initial phase, but these are offset by falling operating costs.
Storage technologies and synthetic energy carriers
The volatile feed-in of renewable energies makes storage technologies such as batteries, pumped storage and hydrogen systems essential. Grid expansion and intelligent control systems are also necessary.
With the steadily increasing demand for climate-neutral energy, innovative technologies and synthetic energy sources are gaining in importance. The aim is to make energy usable where sun and wind are not continuously available, and to be able to use energy sources across sectors – for example in transport, industry and the heating sector. Such solutions extend the range of renewable energies and enable so-called sector coupling.
Power-to-X (PtX)
The term "Power-to-X" describes technological concepts in which electricity – ideally from renewable sources – is converted into other chemical or thermal energy sources. These include:
Power-to-gas: Electricity is converted into hydrogen by electrolysis. This can be stored, used directly or synthesized with CO₂ to methane.
Power-to-liquid: Production of synthetic liquid fuels (e-fuels), especially for aviation and maritime transport.
Power-to-Chemicals: Use of electricity to produce raw materials for the chemical industry.
These technologies enable the seasonal storage of energy and its use in areas that are difficult to electrify.
Green hydrogen
Green hydrogen is considered a key technology for the decarbonization of hard-to-electrify sectors such as industry, aviation and shipping. However, it requires a lot of renewable energy to produce.
Green hydrogen is produced by electrolysis of water with renewable electricity and is therefore CO₂-free. It is considered a central component of the energy transition, especially for applications such as:
Steel production (e.g. direct reduction of iron ore)
Fuel cells in trucks, trains and ships
High-temperature processes in the chemical industry
The biggest challenge lies in efficiency: electrolysis requires about 50–60 kWh of electricity per kilogram of hydrogen. However, scaling is underway – according to the EU's hydrogen strategy, 10 million tonnes of green hydrogen are to be produced annually by 2030.
Synthetic fuels (e-fuels)
E-fuels can be used in existing combustion engines and thus offer a bridging technology, especially for aircraft, ships and existing fleets. They consist of green hydrogen and CO₂ from the air or industrial processes. However, their production is expensive and energy-intensive. The overall efficiency is often less than 20%. Therefore, e-fuels are primarily needed for applications with high energy density.
Thermochemical storage
In addition to battery electricity, thermochemical storage systems (e.g. with salt solutions or reactions such as Ca(OH)₂ ↔ CaO + H₂O) offer a possibility for seasonal energy storage. Such systems are under development for district solutions and industrial clusters, for example as part of research projects at Fraunhofer ISE and DLR.
Space Solar Power Plants
One visionary approach is to install solar panels in space, where the sun shines continuously. The energy generated is to be transmitted to Earth by microwave or laser. The first pilot concepts are being developed in China and Japan, among other places. Cost-effectiveness, technical risks and social acceptance are currently still high hurdles.
Quotes and voices from research:
Dr. Fatih Birol (IEA): "Green hydrogen will become the backbone of climate-neutral industry in Europe."
Agora Energiewende (2023): "Power-to-X is not an end in itself – it is the bridge between electricity surplus and sector coupling."
Fraunhofer UMSICHT: "Synthetic fuels offer a high degree of flexibility, but are energy-intensive."
Global developments and geopolitical aspects
The global energy transition is not only a technical challenge, but also a major geopolitical and economic project with far-reaching consequences for international power relations, trade relations and security structures. The transition from fossil fuels to renewable and synthetic energy sources is changing existing dependencies and creating new dynamics.
Geopolitical power shifts
In the 20th century, oil- and gas-rich countries such as Saudi Arabia, Russia and the USA dominated geopolitical energy events. With the decline of fossil fuels, these countries are gradually losing influence, while countries with great potential for renewable energies or critical raw materials are increasingly moving to the center of the geopolitical stage.
China has become the leading producer of photovoltaic modules, wind turbines, batteries and electrolyzers. Around 80% of global PV value added is in Chinese hands (IEA, 2023).
Chile is positioning itself as an export nation for green hydrogen and ammonia, supported by excellent conditions for wind and solar power.
Morocco is investing in large-scale solar power plants and pipelines to export hydrogen to Europe.
These shifts open up opportunities, but also create new dependencies – especially in the area of technology and raw material supply.
Critical raw materials and new dependencies
The energy transition is exponentially increasing the demand for certain raw materials: lithium, cobalt, nickel, graphite and rare earths are essential for batteries, wind power generators and PV systems. Many of these substances are extracted in geopolitically unstable regions.
According to the International Energy Agency (IEA, 2022), the demand for lithium could increase eightfold by 2040 and quadruple for cobalt. A large part of these raw materials comes from a few countries: about 70% of the cobalt comes from the Democratic Republic of the Congo, over 60% of the lithium from Australia, over 90% of the rare earths are processed in China.
This creates new dependencies and strategic challenges:
Diversification of supply chains: Development of alternative producing countries (e.g. Canada, Brazil, Portugal).
Recycling and Circular Economy: Developing efficient recovery processes for batteries and components.
Technological substitution: Research on substitute materials or reduction strategies for critical elements.
International Cooperation and Energy Justice
While industrialised countries are investing massively in green infrastructure, many countries in the Global South lack the financial and technological means for a sustainable transformation. This threatens to create a global energy gap.
To counteract this trend, initiatives such as the Just Energy Transition Partnerships (JETPs) have been launched. Wealthy countries (G7, EU) are providing capital to support emerging economies such as South Africa, Indonesia and Vietnam in a socially just coal phase-out.
Example: South Africa will receive around 8.5 billion US dollars by 2027 for the restructuring of its coal industry – financed by Germany, France, Great Britain, the USA and the EU.
Energy and safety
Decentralization and electrification increase the resilience of energy systems, but bring with them new security issues:
Cybersecurity: Smart grids and digital networks are vulnerable to attacks.
Security of supply: Local production of green hydrogen or electricity reduces import dependencies, but requires storage solutions.
War and energy prices: The war in Ukraine has had a massive impact on energy prices and highlighted the vulnerability of fossil imports – an additional driver for renewable energies in Europe.
Quotes and analyses:
Fatih Birol (IEA, 2022): "The geopolitical maps of energy are being redrawn – with critical raw materials as new pawns."
Federal Academy for Security Policy (2023): "Energy is not only a question of sustainability, but also of geopolitical stability."
IRENA Global Landscape of Renewable Energy Finance (2023): "The energy transition can only succeed globally with international cooperation."
Social acceptance and political framework conditions
Renewables are increasingly accepted if participation and regional value creation are given. Policy instruments such as carbon pricing, subsidies and international agreements are crucial.
The implementation of the energy transition depends crucially on social acceptance and stable political framework conditions. Technological progress alone is not enough – without the support of the population and clear regulatory guidelines, expansion, investment and transformation will come to a standstill.
Social acceptance
The willingness of the population to support renewable energies depends heavily on the perceived benefits, the fairness of implementation and participation in decision-making processes. Especially when it comes to the expansion of wind turbines and grid expansion, there is always local resistance – a phenomenon that is often discussed under the slogan "Not In My Backyard" (NIMBY).
A study by the Fraunhofer Institute for Systems and Innovation Research (ISI) from 2022 shows that early information, transparent decision-making processes and economic participation significantly increase acceptance. Citizen energy projects, in which residents participate directly in the proceeds, promote identification and trust in the energy transition.
Social justice also plays a central role: Who bears the costs of the transformation – for example through rising electricity prices? Who benefits from subsidies such as the Building Energy Act or the e-car premium? A fair distribution of burdens and opportunities is essential to secure social support in the long term.
"The energy transition needs not only engineers, but also social scientists – because acceptance is a key success factor." — Prof. Ortwin Renn, Director of the IASS Potsdam
Political framework
Reliable, transparent and long-term political guardrails are essential for investments in renewable energies, storage technologies and climate-friendly infrastructure. A central example of this is the German Renewable Energy Sources Act (EEG), which has made a significant contribution to the global spread of photovoltaics since 2000.
Currently, politicians around the world are setting different priorities:
EU – Green Deal & Fit for 55:
With the Green Deal, the European Union is pursuing the goal of being climate-neutral by 2050. Core instruments are the EU Emissions Trading Scheme (ETS), binding sector targets and the expansion of renewable energies to over 42% by 2030.
USA – Inflation Reduction Act (IRA):
The IRA provides over $360 billion for clean technologies. This will massively promote the development of green industries such as battery production, solar module production and hydrogen production.
China – Central expansion targets:
China is pursuing state-controlled expansion with targets and long-term industrial plans. By 2030, the share of non-fossil energies in the primary energy supply is to increase to at least 25%.
International cooperation
Global challenges such as climate change require multilateral solutions. The energy transition can only succeed if countries work together – whether in the expansion of transnational power grids, in the establishment of an international hydrogen market or in the standardisation of sustainability standards.
Examples of international energy cooperation:
Just Energy Transition Partnerships (JETPs): Support emerging economies in the socially acceptable coal phase-out, e.g. South Africa, Indonesia, Vietnam.
EU-MENA Hydrogen Corridor: Cooperation between Europe and North African countries to build a green hydrogen economy.
IRENA & IPHE: International organizations that promote knowledge sharing, data standards, and policy coordination.
Result
The transformation of energy systems is not only a technical, but also a social and political task. Without the trust and active participation of the population as well as without consistent and ambitious political frameworks, the success of the energy transition is in danger of failing. What is needed is a broad-based vision that combines social justice, economic participation and ecological responsibility.
Sources and further reading:
Fraunhofer ISI (2022): Acceptance and Participation in the Energy Transition
IASS Potsdam (2021): Societal Dimensions of the Energy Transition
European Commission (2023): Fit for 55 and Green Deal Policy Briefs
U.S. Department of Energy (2023): Inflation Reduction Act Implementation Plan
IRENA (2023): World Energy Transitions Outlook
Agora Energiewende (2023): Global Energy Transition Policy in Comparison
Evaluation of energy sources according to future criteria
In view of the large number of available energy sources, the central question arises: Which energy sources are sustainable – ecologically, economically, socially and technologically? To answer this question, a structured assessment based on central criteria is necessary.
Evaluation standards
The following categories form the basis for the systematic comparison:
CO₂ emissions (direct/indirect)
Sustainability and resource conservation
Kosten (Levelized Cost of Energy – LCOE)
Storage and transport capability
Technological maturity
Social acceptance
Scalability & Global Potentials
Political and geopolitical risks
Overview of the most important energy sources

Quelle: IEA World Energy Outlook 2023, Fraunhofer ISE, IPCC AR6 Report, Agora Energiewende
Interpretation and discussion
Photovoltaics and onshore wind power perform excellently in almost all criteria. They are cost-effective, climate-friendly and technically sophisticated – but weather-dependent and can only be controlled to a limited extent without storage.
Offshore wind power offers higher yields and greater land potential, but at higher costs and with technical challenges in infrastructure (e.g. grid connection, maintenance at sea).
Hydropower is very efficient, but geographically very limited and ecologically controversial (river straightening, interventions in ecosystems).
Green hydrogen is being treated as a key technology for sector coupling and storage. However, high costs and inefficient conversion losses (approx. 30-40% from electricity to hydrogen) are still major challenges at present.
Nuclear energy offers base-load-capable low-carbon energy, but remains controversial due to costs, long-term risks and social rejection (especially in Germany, Austria, Switzerland).
Fossil fuels such as coal and natural gas are increasingly losing relevance because of their climate balance and political risks. Even transitional technologies (e.g. gas-fired power plants) must be critically assessed if there are no CCS (carbon capture and storage) technologies or green gas admixtures.
Synthetic fuels offer a promising option for aviation and shipping, but are inefficient to produce and can currently only be produced at very high cost.
Conclusion of the review
Renewable energies combined with storage technologies, green hydrogen and efficiency measures represent the most sensible future strategy in terms of energy policy and ecology. Fossil sources and conventional nuclear energy no longer have a sustainable perspective in the long term – neither for environmental, nor for cost and safety reasons.
Scenarios up to 2050 – What will the energy supply of the future look like?
Various energy scenarios (IEA, IPCC, DENA) predict a dominant role for renewables. The world's energy supply is becoming more decentralised, digital, electric and climate-oriented – provided there is investment, technology transfer and political will.
The global energy supply is facing a profound change. The coming decades up to 2050 are crucial to limit global warming to below 2°C, as required by the Paris Climate Agreement. But how will the energy supply develop in concrete terms? Numerous research institutions and energy agencies are drafting scenarios that show possible future paths.
Methodology and assumptions
Scenarios are not predictions, but consistent futures based on certain framework conditions. A distinction is usually made between:
Reference scenarios (business as usual) – without stronger climate policy
Decarbonisation scenarios – with politically set climate targets (e.g. net zero)
Technology-open scenarios – with different combinations of measures
The basis of the following evaluation are, among other things:
IEA Net Zero 2050 Roadmap (2023)
IRENA World Energy Transitions Outlook (2023)
Fraunhofer ISE Scenarios for Germany (2022)
Agora Energiewende Climate-neutral energy system 2045
Development of installed capacity by energy source (worldwide, in GW)
Here is an overview of the expected development of installed capacities (in gigawatts):

Sources: IEA NZE 2023, IRENA 2023, Fraunhofer ISE, Agora Energiewende
🟢 The explosive increase in wind, solar and storage technologies is clearly visible. Fossil fuel capacities are declining drastically, nuclear energy is growing slightly, but remains marginal globally.

Energy Systems of the Future: Features
The energy systems in 2050 will be fundamentally different from today's:
Decentralization: Energy is increasingly generated locally (e.g. through rooftop solar panels), with digital controls.
Sector coupling: Electricity, heat, mobility and industrial processes are linked (Power-to-X, heat pumps, e-mobility).
Flexibility and storage: Battery storage, hydrogen, load management and smart grids compensate for fluctuating generation.
Digitalization: AI and IoT dynamically control demand and generation. Virtual power plants are replacing large-scale fossil fuel power plants.
Future Scenarios in Comparison

BP Energy and IEA scenarios at a glance
The BP Energy Outlook scenarios model different developments in the global energy system up to 2050. Here are the two main scenarios, which were also shown in the graphic:
🔵 Current Trajectory (Status quo)
Description: Refers to current developments in politics, technology and consumption without additional climate policy.
Primary energy demand: Increases moderately from ~627 EJ (2022) to approx. 780–800 EJ by 2050.
Installed capacity: Increasing significantly, especially from solar and wind power. Increase by 8 to 10 times for renewables.
CO₂ emissions: Remain at a high level, no climate targets are achieved.
🟢 Net Zero (climate neutrality by 2050)
Description: Global action to achieve the 1.5°C target under the Paris Agreement.
Primary energy demand: Decreases slightly from around 2040 – through efficiency, electrification and behavioural changes – to ~670 EJ by 2050.
Installed capacity: Growing massively – solar + wind + storage dominate. Electricity share of total demand: >50%.
CO₂ emissions: Approaching net zero; fossil fuels account for <10% of primary energy consumption.
⚖️ The most important parameters in comparison

And here is a comparison of the IEA scenarios from the World Energy Outlook (WEO 2024 & 2023):
🟠 IEA STEPS (Stated Policies Scenario)
Adopted framework: Based on currently implemented policies, no additional measures
Primary energy demand: Will increase by about +25% by 2035 compared to 2022.
Fossil fuels: Benefits of coal, oil and gas reach global peak ≤ 2030, then plateau or slight decline
Renewable Energy & Nuclear: Capacities are growing strongly – electricity generation is becoming increasingly cleaner, especially through PV, wind and nuclear, with ~10,000 GW of generation capacity in 2030
Electrification trend: Global electricity demand is growing rapidly (e.g. two new "Japan" by 2035).
🟢 IEA NZE (Net Zero Emissions by 2050)
Assumptions: Highly ambitious climate targets implemented in accordance with the 1.5 °CPariser target.
Primary energy demand: Decreases by ~15% by 2045 compared to 2022 and remains at lower levels until 2050
Clean energies: share of renewables + nuclear energy to rise to 32-78% by 2045
Electrification & electricity mix:
Electricity demand in NZE grows strongly beyond STEPSNiveau
"Electric age": Electricity, PV, wind dominate expansion trends.
Fossil tank: Decline in coal, oil and gas, but still used – but greatly reduced by 2050 (e.g. coal by ~46%).
📊 Overview in comparison


Challenges and Uncertainties
Despite ambitious goals, major challenges remain:
Grid expansion: New power lines and distribution grids are a bottleneck factor in many countries.
Raw material supply: Expansion of PV, wind and batteries requires enormous amounts of copper, lithium and rare earths.
Global inequality: Many developing countries and emerging economies need financial support for energy transformation.
Political stability: Energy policy depends on international relations, trade flows and the security situation.
Result
The future of energy supply is renewable, networked, decentralised and flexible. By 2050, the global energy system will change fundamentally. It is crucial that the course is set now – technologically, politically and socially. The next 10–15 years are the critical window of opportunity.
"The energy transition is not a sure-fire success. But it is feasible – technologically, economically and socially. The decision is up to us." — Fatih Birol, Director of the International Energy Agency (IEA)
Summary and Conclusion
The question of the energy source of the future is one of the central challenges of the 21st century. Global energy demand continues to grow – not only due to increasing electrification in the transport sector (electromobility), but also due to the restructuring of industrial processes, the decarbonisation of the heat supply and population growth in many regions of the world.
The energy source of the future is not a single concept, but an interplay: renewable energies as the backbone, supplemented by storage, digitalization and green molecules. This is the only way to ensure that the energy transition succeeds economically, ecologically and socially.
Key Findings
As part of this study, all relevant energy sources were systematically examined – from fossil and nuclear to renewable and synthetic options. The evaluation according to ecological, economic, technological and social criteria gives a clear picture:
Fossil fuels (coal, natural gas, oil) no longer have a long-term perspective in a climate-friendly world. Their CO₂ emissions are too high, the geopolitical risks too great and their sustainability too low.
Nuclear energy remains a component of the energy supply in some countries. However, their role is limited by high costs, unresolved repository issues and low social acceptance.
Renewable energies (solar, wind, hydropower, geothermal energy, bioenergy) are already cost-efficient and technically mature. Their expansion is indispensable and must be massively accelerated worldwide.
Green hydrogen and synthetic fuels are urgently needed for the decarbonization of industry, aviation, shipping and as a storage solution. However, they require additional investment in infrastructure, generation capacities and political frameworks.
"The future belongs to renewables – supplemented by storage, digitization and intelligent system coupling."– Agora Energiewende, 2022
Recommendations for action
Based on the current state of scientific and technical knowledge, the following recommendations are made:
Priority on the expansion of renewables: PV and wind are the main pillars. Investments in grids, storage and intelligent control systems must accompany this.
Maintaining openness to technology, but selectively promoting it: hydrogen, geothermal energy and thermal storage offer great potential – especially for industrial applications.
Decarbonization in all sectors: Not only electricity, but also mobility, heat and industrial processes must be consistently converted.
Global equity and partnerships: Building a climate-neutral energy future must be fair globally – through technology transfer, financial aid and new trade relations (e.g. for hydrogen imports).
Promoting social participation and acceptance: Community energy, local value creation and transparent communication strengthen trust and social support.

Conclusion
The energy source of the future is not a single technology, but an intelligent interplay of renewables, storage technologies, efficiency measures and social change. The technologies required for this are already available – the decisive factor now is their consistent implementation.
"There is no one solution – but there is one direction: away from fossil fuels and towards renewables. The greatest danger lies in inaction."– Prof. Claudia Kemfert, DIW Berlin
The transformation of the energy system is not only a technical necessity, but also an opportunity: for innovation, for global partnerships – and for a sustainable future.
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