What Cold Fusion is *Not* - Solid State Fusion Discovery

August 28, 2025

What Cold Fusion is Not

Author: Solid State Fusion Team

Originally, "cold fusion" referred to muon-catalyzed fusion, a nuclear fusion process involving a muon, which is a heavy electron. In 1989, the term was applied to benchtop electrolytic experiments that utilized deuterium and metal to generate anomalous heat. Current research suggests that cold fusion represents merely one potential nuclear reaction that can occur in low-temperature environments. Low-energy nuclear reactions (LENR) have demonstrated the production of fusion, fission, and transmutations through mechanisms fundamentally distinct from those posited by conventional 100-year-old nuclear theory. Cold fusion is not hot fusion.

Cold fusion fundamentally differs from traditional hot fusion, which replicates stellar plasma conditions by requiring extreme temperatures, pressures, and densities to overcome the Coulomb barrier. This electrostatic force repels positively charged nuclei, thereby precluding their sufficient proximity for fusion. Hot fusion employs high-speed collisions to fuse hydrogen isotope nuclei into helium, releasing immense energy. In contrast, cold fusion transpires at considerably lower temperatures, potentially facilitated by quantum effects within materials such as metal lattices. For instance, numerous experiments involve the loading of hydrogen or deuterium into palladium. Cold fusion reactions are fundamentally dissimilar from the plasma reactions in hot fusion and depend upon unique mechanisms.

For a comprehensive understanding of these unique mechanisms, we invite you to review our analysis of the recent Metzler et al. article published in the Journal of New Physics. The authors argue that a multidisciplinary understanding of atomic, nuclear, and quantum effects is necessary.

Differences Between Cold Fusion & Hot Fusion

Table 1 highlights key distinctions between hot and cold fusion, thereby clarifying what cold fusion is not: It does not operate at millions of degrees Celsius, does not require high-energy particle collisions in plasma reactors, and does not need extremely high energy inputs.

Attributes

Cold Fusion

Hot Fusion

Temperature Range

Occurs at lower temperatures, leveraging chemical and quantum properties of material structures and effects like electron screening

Cold Fusion

Requires extremely high temperatures–millions of degrees Celsius–to achieve the conditions that meet the Lawson criterion for fusion

Hot Fusion

Reaction Medium

Utilizes solid-state materials, such as metal lattices (e.g., palladium).

Cold Fusion

Operates exclusively with plasmas and often at high temperatures, generally modeled as randomly oriented for mathematical simplicity

Hot Fusion

Reaction Mechanism

Requires further research, but potentially involves quantum effects, electron screening, nuclear resonance, and material-dependent properties.

Cold Fusion

Relies on high-energy particle collisions and thermonuclear reactions with observable byproducts like neutrons.

Hot Fusion

Energy Output (Scientific)

Produces heat energy significantly higher than chemical reactions, suggesting potential nuclear processes; can also emit radiation or particles.

Cold Fusion

Generates high-energy particles as predicted by classical nuclear fusion, with measurable and repeatable energy yields

Hot Fusion

Energy Output (Engineering)

Some claims suggest energy returns exceeding input energy; investigation of these claims is ongoing.

Cold Fusion

Most current experiments do not produce net positive energy; the energy output remains far below the input required to sustain reactions with the exception of one experiment.

Hot Fusion

Scientific Approach

Empirically driven, focusing on surprising observations and iterative improvements to reproducibility.

Cold Fusion

Theoretically guided, using mathematical models to predict outcomes, with experiments serving as confirmation.

Hot Fusion

Experimental Setup

Conducted via techniques like electrolysis, gas loading, and glow discharge using accessible materials.

Cold Fusion

Mimics stellar conditions using large-scale setups, such as tokamaks and inertial confinement devices.

Hot Fusion

Experimental Cost

Experiments can range from a few thousand dollars (e.g., small-scale laboratory setups) to potentially millions for commercialization efforts.

Cold Fusion

Requires hundreds of millions to billions of dollars for credible research, largely funded by governments or major private investors.

Hot Fusion

Historical Context

Often dismissed due to historical skepticism despite some repeatable but poorly understood anomalies in lab setting.

Cold Fusion

Enjoys broad credibility and funding, driven by its demonstrated success in military and energy applications but has yet to demonstrate economic viability.

Hot Fusion

Expected Market

Offers potential for distributed, small-scale, safe energy production with minimal regulatory constraints.

Cold Fusion

Aims to provide large-scale energy solutions through centralized grid-based power plants, dependent on substantial infrastructure.

Hot Fusion

Comparison to Fission

Promises atomic energy solutions for applications unsuitable for fission, such as residential or vehicular energy needs.

Cold Fusion

Unlikely to outperform advanced modern fission reactors for large-scale power generation.

Hot Fusion

Reproducibility

Demonstrates mixed reproducibility, with ongoing research aimed at achieving consistent results.

Cold Fusion

Energy generation has yet to achieve reproducibility at economically viable levels; reliability remains a secondary concern.

Hot Fusion

Understanding hot fusion mathematically is straightforward, as it involves modeling a few high-energy particles in a random environment. In contrast, LENR takes place within materials that possess molecular structures, introducing complex interactions across various scales that fundamentally alter the process.

As researchers continue to investigate and better understand the phenomenon, the terminology has evolved. The name "cold fusion" has changed along with the field due to this complexity:

Cold Fusion: A term that gained prominence in 1989 following the contentious assertions by Fleischmann and Pons.
Low-Energy Nuclear Reactions (LENR): A broader term that acknowledges various nuclear processes such as fusion, fission, and transmutation.
Solid-State Fusion (SSF): This term encompasses LENR in condensed matter systems

While referred to by various names, the underlying objective of this research remains consistent: to develop clean, practical, and abundant energy sources. The potential of cold fusion lies in its promise of future small-scale, distributed energy devices, such as power generators or water heaters. Despite ongoing challenges with reproducibility, research into Low-Energy Nuclear Reactions (LENR) continues to demonstrate incremental progress.

DIG DEEPER

Fusion is easy. Making Money with Fusion is Hard.

Since the 1960s, anyone could make a fusor in their garage that would demonstrate the fusion reaction and make some neutrons. But that sort of device always consumes more useful energy than it produces.

The main goal of fusion energy researchers is to find ways to make a system that produces industrially useful amounts of energy.

Many important milestones on that journey are worthy of great effort.

Theoretical advances.

Engineering advances.

Experimental technique advances.

And contributing to the bread of science, the literature of experimental experiences, successful and less-so.

DIG DEEPER

Who works on Solid State Fusion, and what do they find interesting about it?

Theoretical physicists, searching for ways to explain observations and extend our theory into new realms. There is an enormous gap of knowledge between the atomic scale and the laboratory scale. And between simple hot plasmas and complex cold molecules, crystals, or materials.

Theoretical chemists EE's finding new ways to stimulate and measure and record nuclear reactions.

Laboratory Scientists and Mechanical Engineers seeking better ways to characterize what happens in the lab and notice the unexpected, and improve the process repeatability.

Earth geo-scientists seeking explanations for our planets heat production and flux of nuclear ash such as helium, or hydrogen. What could happen in Earth's core, which is as hot as the sun's surface, seems to produce excess heat, but we can't see it with any telescope access it by drilling.

Astrophysicists seeking better understanding of ways planets can change isotope ratios.