Renewable energy has transformed how we think about power generation—but when it comes to replacing fossil fuels across every corner of the economy, the picture gets more complicated. The electricity grid is getting cleaner, solar and wind capacity is growing fast, and public momentum behind the energy transition has never been stronger. Yet for large parts of industry, the shift to clean energy remains frustratingly slow, and the reasons why are worth understanding clearly.
This article tackles the most common questions people ask about renewable energy’s limitations—from storage challenges and industrial heat to how emerging technologies like iron fuel are changing the equation. Whether you are a sustainability professional navigating decarbonization targets or simply curious about where the energy transition is heading, these answers cut through the noise.
What is the biggest problem with renewable energy today?
The biggest problem with renewable energy today is intermittency—the fact that solar and wind only generate power when the sun shines and the wind blows. This mismatch between supply and demand creates a fundamental challenge: energy systems need to be reliable around the clock, but the most abundant renewable sources are inherently variable.
This intermittency problem has knock-on effects across the entire energy system. Grid operators must balance supply and demand in real time, which becomes increasingly difficult as more variable generation is added. When renewable output is high, prices can drop to near zero or even go negative. When output is low, backup capacity—often still fossil-fuelled—has to fill the gap.
Beyond intermittency, renewable energy faces several other significant challenges:
- Storage at scale: Current battery technology can store electricity for hours, but seasonal or long-duration storage remains expensive and limited.
- Infrastructure gaps: Many industrial sites and regions lack the grid connections needed to access or absorb large volumes of renewable electricity.
- High-temperature heat: Electricity and most renewable technologies struggle to deliver the extreme temperatures many industries need cost-effectively.
- Upfront capital costs: Transitioning industrial processes to clean energy often requires significant investment, creating financial barriers for many companies.
Together, these challenges mean that while renewable energy has made remarkable progress in the power sector, replacing fossil fuels entirely—especially in heat-intensive industries—requires solutions that go beyond solar panels and wind turbines.
Why is industrial heat so hard to decarbonize with renewables?
Industrial heat is hard to decarbonize because most industrial processes require very high temperatures that conventional renewable electricity sources cannot easily or cost-effectively deliver. Roughly two-thirds of industrial energy consumption goes to heat generation, and approximately 80% of that heat is still produced by burning fossil fuels—a figure that reflects just how stubborn this challenge is.
The core issue is temperature. Many industrial processes in sectors like specialty chemicals, pulp and paper, and food and beverage require sustained heat above 500°C, and some processes need temperatures well above 1,000°C. Electric heating can technically reach these temperatures, but the energy costs and infrastructure requirements are often prohibitive at an industrial scale.
Why electrification alone is not enough
Electrifying industrial heat sounds straightforward in theory, but in practice it runs into real obstacles. Many industrial facilities are located in areas where grid capacity is insufficient to handle the additional electrical load. Upgrading grid connections takes years and costs millions. For a factory that needs heat continuously and at scale, waiting for grid infrastructure is simply not a viable strategy when emissions targets are pressing.
Why hydrogen faces its own barriers
Green hydrogen is often proposed as an alternative for high-temperature industrial heat, and it does have genuine potential. However, transporting and storing hydrogen safely requires specialised infrastructure that most industrial sites do not currently have. The cost of green hydrogen also remains high, and supply chains are still developing. For many companies, hydrogen is a long-term option rather than a near-term solution.
This combination of factors—high temperature requirements, infrastructure constraints, and cost pressures—is precisely why industrial heat remains one of the most challenging parts of the energy transition. It is also why new approaches to industrial heat decarbonization are attracting serious attention from both industry and investors.
If you are working through these challenges in your own organisation, the form below can help connect you with the right expertise.
What are the main types of renewable energy storage solutions?
The main types of renewable energy storage solutions are lithium-ion batteries, pumped hydro storage, green hydrogen, thermal storage, and solid-state energy carriers like iron fuel. Each technology serves different purposes, operates at different timescales, and suits different applications—there is no single solution that works for everything.
Understanding the landscape of storage options helps explain both the progress being made and the gaps that remain:
- Lithium-ion batteries: Currently the dominant short-duration storage technology. Excellent for balancing grid fluctuations over minutes to hours, but expensive for multi-day or seasonal storage.
- Pumped hydro storage: The most mature large-scale storage technology, using surplus electricity to pump water uphill and releasing it through turbines when needed. Geographically limited but highly reliable.
- Green hydrogen: Produced by using renewable electricity to split water, hydrogen can store large amounts of energy and be used in fuel cells or combustion. Infrastructure and cost remain significant hurdles.
- Thermal energy storage: Stores heat directly using materials like molten salt or water. Useful for industrial processes but limited in terms of energy density and transport flexibility.
- Solid-state energy carriers: Materials like iron powder can store energy in a stable, transportable form and release it as heat through combustion. This category is emerging as particularly promising for industrial applications.
The diversity of storage technologies reflects the diversity of energy needs. No single solution will solve the storage challenge across all sectors. The most effective path forward involves matching the right storage technology to the right application—and for industrial heat, solid-state carriers are increasingly relevant.
How does iron fuel technology solve renewable energy’s biggest problems?
Iron fuel technology addresses renewable energy’s biggest problems by providing a high-density, transportable, carbon-free energy carrier that can deliver high-temperature industrial heat on demand. Unlike solar or wind, iron fuel is not dependent on weather conditions. Unlike batteries, it can store energy for extended periods without degradation. And unlike hydrogen, it can be transported safely in standard containers without specialist infrastructure.
The technology works on a circular principle that functions much like a rechargeable battery. Fine iron powder burns with ambient air inside a boiler, producing a flame of up to 2,000°C and generating steam, hot water, or hot air with zero direct CO₂ emissions. The only by-product of combustion is iron oxide—essentially rust—which is then collected, transported to a production facility, and converted back into iron fuel using low-carbon hydrogen. The cycle then begins again.
What makes iron fuel practical for industry
Iron fuel’s practical advantages are significant. The boiler system achieves an energy efficiency of up to 95%, which compares favourably with many fossil-fuel systems. The total CO₂ output from the boiler is just 10 kg per megawatt-hour of thermal energy, and that figure comes entirely from a small pilot safety flame—the iron combustion itself is completely carbon-free. NOₓ emissions are among the lowest of any fuel.
Crucially, the Iron Fuel Boiler is designed to integrate with existing industrial setups rather than replace them entirely. This plug-and-play approach means companies can begin decarbonizing their heat generation without dismantling their current infrastructure. You can learn more about how the technology works in detail on our Iron Fuel Technology page.
The technology has been demonstrated at the megawatt scale at Technology Readiness Level 7 (TRL 7) in Helmond, the Netherlands, where an Iron Fuel Boiler successfully powered a district heating network under real-world conditions. This is not a concept on paper—it is a working system with a proven track record, and the first commercial contract has already been signed.
What’s the difference between iron fuel and green hydrogen for industry?
The key difference between iron fuel and green hydrogen for industry is how each stores and delivers energy. Green hydrogen is a gas that requires pressurised or cryogenic storage and specialised pipelines or transport equipment. Iron fuel is a solid powder that can be stored and transported in standard containers—no special infrastructure needed. For most industrial sites, this distinction is highly consequential.
Both technologies share an important characteristic: when produced using renewable energy, neither releases CO₂ during use. Green hydrogen combusts cleanly, and iron fuel combustion is carbon-free. Both can deliver high-temperature heat. But their practical profiles for industrial deployment differ considerably.
Safety and logistics
Hydrogen is a highly flammable gas with a wide flammability range, which creates real safety and regulatory challenges for storage and transport at industrial sites. Iron powder, by contrast, is a stable solid. While it requires appropriate handling procedures, it does not carry the same explosion risk as pressurised hydrogen. For industrial operators managing complex, busy sites, this difference in risk profile matters.
Infrastructure requirements
Deploying green hydrogen at scale requires investment in new pipelines, compression equipment, and storage facilities. Most industrial sites do not have this infrastructure today, and building it takes time and capital. Iron fuel, on the other hand, can be delivered by truck and stored on-site in conventional containers. This makes it far more accessible for companies that need to act on their decarbonization commitments now rather than waiting for hydrogen infrastructure to develop.
This is not to say hydrogen has no role to play—it is a key input in the iron fuel cycle, used to regenerate iron oxide back into iron fuel. The two technologies are complementary rather than purely competitive. But for near-term industrial heat decarbonization, iron fuel offers a more immediately deployable pathway for many companies.
When will renewable energy fully replace fossil fuels in industry?
Renewable energy is unlikely to fully replace fossil fuels in industry before 2050, and even that timeline requires significant acceleration in technology deployment, policy support, and investment. The industrial sector is one of the hardest parts of the economy to decarbonize, and progress has been slower than in electricity generation. However, the pace is picking up, and the tools to make it happen are increasingly available.
Several factors will determine how quickly the transition unfolds. Regulatory pressure from frameworks like the EU Emissions Trading System is making carbon-intensive production progressively more expensive, creating a financial incentive to switch. Meanwhile, clean-heat technologies are reaching commercial maturity, with early adopters already deploying solutions that would have been unavailable just a few years ago.
The 2030s are likely to be a pivotal decade. Companies that begin deploying clean-heat solutions now will have a significant advantage—both in terms of regulatory compliance and in building the operational experience that comes with early adoption. Those that wait may face higher costs, tighter timelines, and fewer technology options as demand for clean energy solutions intensifies.
The honest answer is that there is no single date when fossil fuels disappear from industry. The transition will happen sector by sector, site by site, as commercially viable alternatives become available and the economics shift. What is clear is that the technologies needed to make it happen—including iron fuel—are already moving from demonstration to deployment.
How RIFT helps solve renewable energy’s industrial challenge
We develop and deliver industrial Iron Fuel Boilers—clean energy systems that replace fossil fuel-fired heat generation with a fully circular, carbon-free alternative. For sustainability managers facing the challenge of decarbonizing industrial heat, our technology offers a practical path forward that works within existing infrastructure and operational realities.
Here is what makes our approach different:
- Zero direct CO₂ emissions from iron fuel combustion, with total system output of just 10 kgCO₂ per MWhth
- Up to 95% energy efficiency, outperforming many traditional fossil-fuel boilers
- Plug-and-play integration with existing boiler infrastructure—no major disruption to operations
- Cost-competitive pricing aligned with fossil fuels, protecting your bottom line
- Long-term fuel supply agreements for reliable, dependable access to iron fuel
- Ultra-low NOₓ emissions—among the lowest of any combustion fuel
We are backed by €113.8 million in funding and have already signed the world’s first commercial contract for industrial iron fuel deployment. If you are ready to explore what iron fuel technology could mean for your operations, get in touch with our team to start the conversation.