A battery does not have to hide energy in chemical bonds. One proposed grid-scale design heats carbon until it glows, then uses specialized photovoltaic cells to turn that artificial light back into electricity.
From current to a white-hot store
Electric grids must constantly balance supply and demand. When wind or solar power is abundant, electricity can run resistance heaters—the same basic effect used in a toaster—and raise an insulated storage material to extreme temperatures. Later, that hot material radiates energy as light. Thermophotovoltaic cells, or TPVs, face the emitter and convert part of that light into electric current. The storage medium can be relatively simple carbon, while the precision work happens in the light-harvesting cell. [1][2]
A solar cell for a manufactured sun
A normal solar cell is tuned for sunlight. A TPV cell is tuned for the spectrum emitted by a deliberately heated object. In a 2022 peer-reviewed experiment, researchers from MIT and the US National Renewable Energy Laboratory tested two-junction cells against a tungsten emitter between 1,900 and 2,400 degrees Celsius. The best tandem reached 41.1 percent efficiency, with an uncertainty of one percentage point, at 2,400 degrees. Its average across that temperature range was 36.2 percent. Those figures describe heat reaching the cell and electricity leaving it—not the efficiency of an entire storage plant. [1][2]
The useful photons stay; the others go back
The cell stacks two semiconductor junctions with different bandgaps. Higher-energy photons are absorbed in the first layer; lower-energy photons can reach the second. Light that neither junction can use meets a reflective gold backing. NREL reported that this mirror returned about 93 percent of the unabsorbed light toward the emitter, where the energy could be recycled instead of heating the cell as waste. This optical recycling is the quiet trick: efficiency depends not only on capturing useful light, but also on refusing the wrong light without losing it. [1][2]
Why remove the turbine?
Conventional power stations often use heat to make a fluid expand and spin machinery. The TPV conversion stage has no rotor, blades or bearings, so it can respond electronically and operate beside heat sources hotter than turbine materials normally tolerate. That creates a possible route for storing excess electricity for later release. It may also reduce maintenance at the conversion stage. Yet a complete plant can still need insulation, cooling, electrical equipment and, in some designs, pumps to move heat. The phrase no moving parts applies to the cell, not automatically to every component around it. [1][3]
A powerful cell is not yet a power station
The published demonstration measured cells roughly one square centimetre in area under controlled laboratory conditions. A grid installation would require vast cell areas, durable packaging, repeated thermal cycling and tight control of heat leakage. Researchers have demonstrated the conversion mechanism and its high cell efficiency; manufacturing cost, long-term reliability and whole-system round-trip efficiency remain engineering questions. A thermal battery also loses energy while charging, storing and discharging, so its system efficiency must be lower than the isolated cell result. [1][3]
What to keep in mind
The 41.1 percent result was a peak laboratory cell measurement, not a commercial battery’s round-trip efficiency. It does not establish lifetime, installed cost or performance at grid scale. Different thermal-battery designs also use different storage materials and heat-transfer systems.
Sources & context
Numbered references link the explanation to its sources. Hypothetical examples and visual metaphors are labelled in the text. Checked 26 October 2026.
- LaPotin et al. — Thermophotovoltaic efficiency of 40% (Nature, 13 April 2022)
- NREL — Capturing Light From Heat at 40% Efficiency (18 May 2022)
- MIT News — A new heat engine with no moving parts is as efficient as a steam turbine (13 April 2022)
KEEP EXPLORING
The Energy Problem Nobody SeesExplore · 3 min read
Your Skeleton Repairs Itself by Taking It ApartPeek · 1 min read
Helping Cells Read Past a Premature Stop SignalNewsroom · 1 min readCURIOUS MINDS, SHARED IDEAS
Join the conversation
What surprised you? Share a thought or a question.
Loading reader responses…