This New Solar Panel Tech Works Even at Night

No Sun? No Problem: How Nighttime Solar Panels Harvest Energy from the Cold Night Sky

Thermoradiative energy generation – often dubbed “nighttime solar” or “anti-solar” power – is a new way to generate electricity after the sun goes down. It exploits a simple scientific principle: heat flows from warmer objects to cooler surroundings, and that flow can be converted into electricity. During the day, the Sun (a very hot body) warms the Earth; at night, the Earth’s surface cools by radiating heat as infrared light into the cold darkness of space. Thermoradiative devices aim to tap into this outgoing heat radiation and turn it into usable power nature.com abc.net.au. In essence, they act like solar cells in reverse: instead of absorbing sunlight from a hotter source, they emit infrared light to a colder sink (the night sky) to drive an electric current nature.com unsw.edu.au. As long as the device is warmer than its environment (e.g. a warm surface facing the cool night sky), it will radiate heat and can produce electricity from that energy flow nature.com abc.net.au.

This concept may sound counterintuitive – how can emitting light produce power? – but it obeys the same thermodynamic fundamentals as ordinary solar photovoltaics. “It’s counterintuitive that a material that emits radiation can generate electricity at the same time, but that’s what we’ve demonstrated,” explained UNSW Professor Nicholas Ekins-Daukes, who leads a night-solar research team nature.com. Dr. Phoebe Pearce, a researcher on the team, put it simply: “In the same way that a solar cell generates electricity by absorbing sunlight from a very hot sun, the thermoradiative diode generates electricity by emitting infrared light into a colder environment. In both cases the temperature difference is what lets us generate electricity.” unsw.edu.au In other words, thermoradiative generators still ultimately harvest solar energy – just at a later stage. The Earth absorbs sunshine by day and re-radiates that energy as heat by night; thermoradiative devices capture a small portion of this departing heat flow as electric power abc.net.au abc.net.au.

How Nighttime Generators Differ from Traditional Solar Panels

Conventional solar panels (photovoltaics) generate current by absorbing incoming photons from a hotter source (the Sun). In contrast, thermoradiative devices generate current by emitting photons (in the infrared range) to a colder sink nature.com. This means the current and voltage run in the opposite direction compared to a normal solar cell ucdavis.edu. A standard solar cell is cooler than the Sun, so it gains energy from sunlight; a thermoradiative cell is warmer than deep space, so it loses energy via infrared radiation – and in doing so, it can drive electrons and produce power ucdavis.edu nature.com. Effectively, daytime solar cells use the Sun-Earth temperature difference, while nighttime cells use the Earth-space temperature difference.

Because of this flipped operating mode, thermoradiative panels can work when regular solar panels cannot, such as during nighttime, or even on cloudy days if there’s a warm surface and a cold sky. However, the physics also implies that the power levels are lower. The Sun is extremely hot (~5,500 °C), providing intense light, whereas the radiative cooling to space relies on Earth’s warmth (~15–20 °C) against the frigid 3 K background of space. That yields much smaller energy flux. In fact, today’s prototype “night solar” devices only generate milliwatts of power per square meter, a tiny trickle compared to the hundreds of watts per square meter from midday sun spectrum.ieee.org. One Stanford experiment produced about 50 milliwatts per square meter (0.05 W/m^2) at night – “a trickle… but already financially interesting for low-power applications like LED lighting or phone charging,” said Prof. Shanhui Fan, who led the Stanford study spectrum.ieee.org. By comparison, a standard solar panel might output 100–200 W/m^2 under bright sun spectrum.ieee.org. In short, thermoradiative tech won’t replace high-power solar farms, but it could complement them by providing continuous 24-hour generation, albeit at lower wattage ucdavis.edu spectrum.ieee.org.

Another key difference is in device structure. Traditional solar panels use semiconductor p–n junctions optimized for visible light. Thermoradiative generators require materials that can efficiently emit and absorb mid-infrared light (wavelengths ~8–13 μm) spectrum.ieee.org. Early prototypes borrow materials from infrared imaging and night-vision technology (for example, mercury cadmium telluride, a sensor material used in thermal cameras) unsw.edu.au. These are quite different from the silicon used in most solar PV panels. Also, some approaches use thermoelectric generators rather than photovoltaic diodes: for instance, the Stanford team attached a thermoelectric module to a cooled solar panel, converting a temperature difference directly into voltage spectrum.ieee.org. In that setup, the solar panel itself acted as the radiator to sky, cooling below ambient air temperature at night, and the thermoelectric device harvested the heat flowing from the warmer air to the cooler panel spectrum.ieee.org spectrum.ieee.org. Conventional solar cells don’t do anything with radiative cooling; in fact, they usually lose efficiency if they get cold at night, whereas the new tech actively exploits it. These distinctions underscore that “nighttime solar” devices are a new class of energy technology, operating on heat emission and radiative cooling principles rather than direct sunlight.

From Theory to Reality: Recent Breakthroughs (2010s–2025)

The idea of nighttime power generation from radiative cooling has been explored theoretically for years, but only recently have experiments caught up. Here are some key milestones and breakthroughs in the last decade, especially after 2020:

• 2014–2019: Physicists began formulating the thermodynamics and detailed balance theory for thermoradiative diodes (the “solar cell in reverse” concept). The notion of using Earth as a heat source and the night sky as a heat sink was discussed in academic circles, but remained speculative nature.com. This fourth “missing quadrant” of optoelectronics (where a device at negative voltage and positive current emits light and generates power) was largely a theoretical curiosity nature.com.
• 2020 – Concept Paper and Prediction: Jeremy Munday (then at University of California Davis) and colleagues published a landmark paper proposing an “anti-solar” photovoltaic cell that could work at night ucdavis.edu. They calculated that, under ideal conditions, such a thermoradiative cell could generate up to ~50 W/m² at night – about one-quarter of a daytime solar panel’s output ucdavis.edu. This got wide media attention as the “anti-solar cell” idea. Munday’s team also started building small prototypes and noted that the physics is essentially the photovoltaic process run in reverse ucdavis.edu ucdavis.edu.
• 2022 – First Experimental Power Generation: In 2022, a team at the University of New South Wales (UNSW Sydney) achieved the first unambiguous lab demonstration of thermoradiative power. They used a tiny thermoradiative diode made of mercury cadmium telluride (a material from IR night-vision sensors) to generate electricity from the infrared heat radiating off a warm surface toward a cold sky nature.com unsw.edu.au. The output was extremely small – about 100,000 times weaker than a solar panel in sunlight unsw.edu.au abc.net.au – roughly on the order of nanowatts, enough to power only a wristwatch from body heat differences nature.com. “We’ve just demonstrated that this is possible… the device we’ve made is relatively low power, as expected at these early stages,” said Prof. Ekins-Daukes of UNSW abc.net.au abc.net.au. Importantly, this was proof of concept that the long-theorized effect actually works outside of textbooks abc.net.au abc.net.au. The results were published in ACS Photonics in 2022 unsw.edu.au, sparking a wave of excitement and global press coverage. Scientists likened it to the first silicon solar cell in 1954 – only ~2% efficient, but a starting point for decades of progress unsw.edu.au.
• 2022 – Radiative Cooling Panel Prototype (Stanford): Around the same time, researchers at Stanford University took a different approach to “nighttime solar.” Instead of a specialized diode, they retrofitted a conventional silicon solar panel with a thermoelectric generator (TEG) to capture radiative cooling energy spectrum.ieee.org. At night, a solar panel exposed to clear sky loses heat and actually drops a few degrees below the ambient air temperature euronews.com. The Stanford team, led by Prof. Shanhui Fan, exploited this by sandwiching a TEG between the cooling solar panel and the warmer air. Heat flowed from the air through the TEG into the colder panel, generating a small current spectrum.ieee.org spectrum.ieee.org. Testing on Stanford’s rooftop over multiple nights in late 2021 showed a steady 50 mW per m² of electric power under a clear night sky spectrum.ieee.org. “Compared to 100–200 W/m² under sunlight, 50 mW is a trickle,” Prof. Fan said, “but it’s already enough for low-power devices like an LED or phone charger” spectrum.ieee.org. In drier, hotter climates (where radiative cooling at night is stronger), they estimated it could reach ~100 mW/m² with the same setup spectrum.ieee.org. This work, published in Applied Physics Letters in 2022, demonstrated a practical “night solar panel” prototype using off-the-shelf components.
• 2022–2023 – Validation and Interest: The UNSW and Stanford demonstrations validated that nighttime power harvesting is feasible. Media outlets dubbed the technology “night solar panels” that work “with the stars” instead of the sun renewableaffairs.com renewableaffairs.com. The public was intrigued by solar panels that generate energy at night, and the news went viral on tech sites and social media. The concept even earned nicknames like “anti-solar cells” or “moonlight panels,” although moonlight itself isn’t the source (it’s really Earth’s heat) euronews.com. The initial power levels were very low, but researchers emphasized that this was just the beginning. “The proof of concept is big,” Ekins-Daukes told the ABC, “we’ve only been using half the opportunity [sunlight in daytime]. Now we’re tapping into the thermal emission that leaves Earth at night.” abc.net.au abc.net.au Interest from funding agencies picked up, seeing the potential to fill the solar energy gap at night.
• 2024 – Efficiency Improvements and New Materials: By 2024, the UNSW team reported progress on improving thermoradiative diodes. They experimented with new semiconductor materials that are easier to manufacture than mercury cadmium telluride unsw.edu.au unsw.edu.au. They also optimized device designs to reduce internal losses. A paper in Nature Photonics (late 2024) detailed enhanced performance, still small in absolute terms but moving closer to theoretical limits nature.com nature.com. There’s room to improve output by about 1000-fold before hitting fundamental thermodynamic limits, the researchers noted nature.com. Achieving that would make nighttime diodes approach ~10% of a solar panel’s output – tens of watts per square meter instead of milliwatts unsw.edu.au nature.com. While that level is not realized yet, it’s a target that guides ongoing research. Another 2024 study in iScience modeled how much power thermoradiative panels could realistically get in different climates aos-nielsen-group.com aos-nielsen-group.com. It found that clear, dry desert nights offer the best conditions – potentially dozens of mW per m² – whereas humid or cloudy nights dramatically reduce the harvest (since clouds and atmospheric water vapor send heat back down) nature.com aos-nielsen-group.com. This helps identify where “night solar” might be most practical on Earth (think cloudless regions or seasons).
• 2024 – Moving Toward Space Applications: A particularly exciting development in 2023–2024 is the interest in using thermoradiative generators in spacecraft. Satellites in low-Earth orbit experience 45 minutes of daylight followed by 45 minutes of darkness each orbit nature.com. They normally rely on battery storage when in Earth’s shadow. A thermoradiative layer on a spacecraft could instead keep trickling out power during those eclipses nature.com. In 2024, Prof. Ekins-Daukes’ UNSW group announced a project (funded by the U.S. Air Force) to test a night-solar diode in space nature.com. “One objective is to optimize our thermoradiative diode as much as possible and then do a space flight,” he said nature.com. They aim to launch an experimental device by 2025–26 to see how it performs in orbit’s extreme cold and darkness unsw.edu.au. This fast-tracks the technology – much like the first silicon solar cells went from lab demo in 1953 to powering Vanguard satellites by 1958 nature.com. If successful, it could prove valuable for satellites, space stations, or even deep-space missions where sunshine is intermittent or absent.
• 2025 – Ongoing Research: As of 2025, research teams around the world are pushing the frontiers of thermoradiative tech. The UNSW “Night Time Solar” group has published results on temperature-dependent performance of various diode materials (including III–V semiconductors that could be more scalable) aos-nielsen-group.com. Jeremy Munday’s team in the U.S. is developing prototype anti-solar cells in the lab and exploring integrating them with conventional solar panels ucdavis.edu ucdavis.edu. New academic collaborations and funding grants have popped up, recognizing that solving night generation could significantly boost renewable energy reliability. While still mostly in laboratories, nighttime solar is transitioning from a fascinating idea toward a practical technology.

Real-World Experiments and Prototypes

Lab demonstrations so far have been small-scale – often single diodes or mini-panels powering tiny devices under controlled conditions. For example, the UNSW team’s thermoradiative diode was tested using the heat difference between a warm plate and a cooled environment, generating mere nanowatts (detected only with sensitive instruments) unsw.edu.au nature.com. They humorously noted it can power a wristwatch – if that watch were running on the wearer’s body heat nature.com. The device essentially showed that any warm surface (even the Sydney Opera House’s roof at night, as the researchers quipped) could, in theory, produce solar-like power after dark qpvgroup.org.

The Stanford prototype was more tangible: it used a standard silicon solar cell panel with an added thermoelectric generator. This was a proof-of-concept that night power can be harvested with existing solar technology plus some modifications spectrum.ieee.org. Over a few nights of outdoor testing, it lit up a small LED and could slowly charge a phone (given enough hours), illustrating potential off-grid uses spectrum.ieee.org. Notably, it required clear skies and a decent temperature drop; the device produced much less or zero power on cloudy or warm nights. Still, it demonstrated that retrofit solutions are possible – you could imagine a future kit to upgrade normal solar panels so they eke out a bit of energy overnight spectrum.ieee.org spectrum.ieee.org.

No full-scale commercial pilot plant exists yet for nighttime solar. However, researchers are scaling up their tests. Outdoor field trials have begun: teams are placing experimental panels on rooftops or in deserts to measure real-world night generation over seasons aos-nielsen-group.com. These trials help determine how factors like humidity, weather, and angle to the sky affect output in practice. For instance, a study measured that a clear desert sky might allow ~0.04–0.1 W/m², while a cloudy sky yields nearly zero net power aos-nielsen-group.com. Such data will guide where early deployments make sense (e.g. arid climates).

On the space front, the upcoming satellite test (expected by 2026) will be the first off-world prototype. If a thermoradiative diode can survive launch and function in orbit, it could pave the way for integrating these devices on satellites or planetary rovers. Even a few watts of continuous trickle charge in space can be extremely valuable, potentially allowing smaller batteries or keeping instruments alive during long nights.

It’s worth noting that any warm object radiating to a cooler environment can be exploited. This means beyond night sky, one could attach thermoradiative generators to industrial waste-heat sources or even to human bodies. In fact, researchers speculated about body-heat-powered electronics: for example, a thermoradiative cell could scavenge energy from a person’s warmth radiating into a cool room, perhaps to run a medical wearable or slowly recharge a pacemaker battery unsw.edu.au unsw.edu.au. Such ideas are still conceptual, but a tiny “night PV” cell could one day extend or replace batteries for certain implants or wearables by using the human body (warm) vs. surroundings (cooler) as the heat differential.

Quotes and Insights from the Pioneers

Scientists and engineers in this nascent field have shared a mix of excitement and realism about its promise:

• “We have made an unambiguous demonstration of electrical power from a thermoradiative diode,” said A/Prof. Ned Ekins-Daukes after the first 2022 lab success, emphasizing that even though it’s 100,000× less power than a solar panel, it proves the physics works unsw.edu.au abc.net.au. “Whenever there is a flow of energy, we can convert it… We’re diverting energy flowing in the infrared from a warm Earth into the cold universe,” added Dr. Phoebe Pearce, highlighting the elegance of harvesting Earth’s nightly heat loss unsw.edu.au.
• “It allows us to generate electricity at night, just from the cold night sky. That’s really exciting,” Ekins-Daukes told ABC News, underscoring how half of Earth’s daily heat budget had been untapped until now abc.net.au. He noted that “in a sense, we’ve only been dealing with half of the opportunity when we use photovoltaic cells in the day” – the other half being the infrared energy flowing out at night abc.net.au abc.net.au.
• Stanford’s Prof. Shanhui Fan pointed out that while the nighttime power is small, it might be practically useful: “The nighttime production is a trickle at 50 mW/m². But it is already financially interesting for low-power applications like LED lights, charging a cellphone, or powering small sensors.” spectrum.ieee.org He also described the mechanism: “At night, the solar panel can reach a temperature below ambient air – that’s a rather unusual opportunity for power harvesting.” euronews.com In other words, radiative cooling gives a free temperature gradient that we can exploit.
• On the future potential, Dr. Michael Nielsen of UNSW (lead author on several thermoradiative studies) said being at the very start of this field is thrilling: “Even if commercialization… is still a way down the road, being at the very beginning of an evolving idea is such an exciting place to be as a researcher… We hope for rapid progress towards delivering the dream of solar power at night.” unsw.edu.au The dream of “solar power at night” is ambitious, but each improvement brings it closer.
• Researchers also frankly acknowledge the challenges. “Right now, [our] demonstration is very low power… One of the challenges was actually detecting it,” Ekins-Daukes said, stressing that big advances will require better materials and industry investment unsw.edu.au. “I have to be honest, we need to find some new materials to achieve [widespread use],” he told ABC, and “how engaged industry can be” will determine how quickly costs come down abc.net.au abc.net.au.
• There’s optimism tempered with pragmatism. “I think for this to be breakthrough technology, we shouldn’t underestimate the need for industries to step in and really drive it. I’d say there’s still about a decade of university research to be done… And then it needs industry to pick it up,” Ekins-Daukes said in a UNSW briefing unsw.edu.au unsw.edu.au. He compared it to the solar PV revolution: academic pioneers like Martin Green made key discoveries, but it was industrial scale-up (backed by large investments) that made solar panels cheap and ubiquitous unsw.edu.au. The same will likely hold for thermoradiative tech.

Potential Applications and Benefits

What could we use nighttime solar technology for, if it matures? Here are some of the most promising applications and their benefits:

• 24/7 Solar Power Systems: Perhaps the biggest vision is integrating day and night generators for round-the-clock renewable energy. You could have hybrid panels that produce electricity during the day via normal PV, and continue to generate a smaller amount at night via thermoradiative cells abc.net.au. This could reduce reliance on batteries to cover nighttime gaps, improving the consistency of solar power on the grid. Even a night output that’s 5–10% of the daytime output could run critical devices or trickle-charge storage, flattening the solar supply curve spectrum.ieee.org.
• Satellite and Spacecraft Power: Thermoradiative diodes are well-suited for space, where the “sky” is extremely cold and every 90 minutes a satellite goes into darkness nature.com nature.com. A layer of these diodes on a satellite could generate power during the orbital night, supplementing or partly replacing heavy batteries. This can extend mission life and reduce weight. The U.S. Air Force and academic groups are actively pursuing this use-case, aiming to test night-solar cells on satellites within the next two years nature.com unsw.edu.au. If successful, future spacecraft might routinely coat their surfaces with thermoradiative generators to harvest power whenever they face deep space.
• Remote Sensors and IoT Devices: Many sensors (for agriculture, environmental monitoring, security, etc.) need to run all night in locations where grid power isn’t available. Nighttime solar trickle chargers could keep them powered through the night using the heat of the Earth. For example, a sensor network in a desert could use day solar and night thermoradiative panels together, so the sensors never fully power down. This could be more reliable and lower-maintenance than using only solar + battery, especially if replacing batteries is difficult or costly in the field spectrum.ieee.org.
• Off-Grid Lighting and Small Electronics: In rural or off-grid communities, low-power lighting or phone charging at night could be supplied by “night” panels. As Prof. Fan noted, 50 mW/m² can drive LED lights or charge phones (albeit slowly) spectrum.ieee.org. In principle, a few square meters of night-panel could power an LED lamp for safe lighting after dark without any battery – a boon for areas lacking electricity. This tech could complement regular solar lanterns by providing a bit of direct night generation.
• Wearables and Medical Devices: The human body is a constant heat source (~37 °C) in a cooler environment, especially in an air-conditioned room or a cold climate. A miniature thermoradiative cell could harvest body heat radiating into the surroundings unsw.edu.au. This might power electronic wearables like smart watches or fitness trackers, or even critical devices like pacemakers and artificial hearts unsw.edu.au. Today these run on batteries that eventually need recharging or replacement – but a body-heat “trickle charger” could extend their life. Ekins-Daukes suggested that in principle a person’s own heat could power a wristwatch continuously unsw.edu.au unsw.edu.au. It’s a futuristic idea, but not out of the question if thermoradiative devices become efficient at small scales.
• Industrial Waste Heat Recovery: Thermoradiative diodes can be thought of as a type of heat engine, but one that converts heat to electricity by radiating light. They could potentially be attached near hot machinery or furnaces that operate in cooler ambient environments. Instead of the heat just dissipating, a TR device could radiate some of it to a cooler reservoir (like the sky or a cooling chamber) and produce power in the process aos-nielsen-group.com. This is analogous to thermoelectric generators currently used on engines, but using radiative physics could work in scenarios where thermoelectrics are less efficient. It’s an area of research – using TR cells for reclaiming energy from industrial processes or even from car exhaust heat.

Limitations and Challenges

Despite the excitement, thermoradiative “nighttime solar” technology faces significant challenges before it can become mainstream:

• Low Power Density (Efficiency): The current efficiency is extremely low – on the order of 0.001% or less of incoming solar PV. The UNSW diode produced 1/100,000th the power of an equivalent solar cell area abc.net.au abc.net.au. Even optimistic projections suggest the absolute upper limit is around 50 W/m² at night ucdavis.edu aos-nielsen-group.com, and a more realistic goal might be 10–20 W/m² (about 1/10 of conventional solar) unsw.edu.au nature.com. That means you’d need a very large area of night-panels to generate significant power. Such low intensity is only suitable for small loads unless efficiency improves dramatically. Researchers are trying to boost it by 100× or more, but that will require years of innovation nature.com.
• Material Challenges: The materials that work best for thermoradiative diodes (so far) are not cheap or mass-produced. HgCdTe (mercury cadmium telluride) was used in the first demo because it’s very sensitive in mid-infrared unsw.edu.au, but it’s a toxic and costly semiconductor used mostly in military IR detectors. Effort is shifting to more common materials (like certain III–V semiconductors, e.g. InAs or InSb alloys) that might be easier to manufacture aos-nielsen-group.com. Still, making a semiconductor device that emits IR efficiently and has low electrical losses is hard. Non-radiative recombination (where electron-hole pairs waste energy as heat instead of light) plagues these devices at present aos-nielsen-group.com aos-nielsen-group.com. New designs, possibly using quantum wells or “intermediate band” structures, are being explored to improve radiative efficiency pubs.aip.org. Until a breakthrough in materials happens, the performance will remain far below theoretical limits.
• Thermal Management and Environment: To get useful power, the thermoradiative device must stay warmer than the sky (or whatever cold sink it’s radiating to). That often means the device needs a good thermal connection to a heat source (like the ground or ambient air) while having a clear view of cold space. The Stanford prototype, for example, needed a large aluminum thermal link between the solar cell and TEG, and a heat sink to ambient air spectrum.ieee.org. Any inefficiency in heat conduction can kill the power output. Moreover, if the ambient air temperature drops close to the panel’s temperature, the power goes toward zero. Weather dependence is a major factor: cloud cover or humidity at night acts like a blanket, warming the sky and thus reducing the temperature difference available. Deserts and clear winter nights are ideal, but tropical, cloudy, or hazy conditions greatly diminish performance nature.com aos-nielsen-group.com. This means nighttime solar might be seasonally or geographically limited, or require locations with optimal sky conditions (high altitude, arid climate, etc.). Mitigating this could involve pairing the device with active cooling or deploying in regions known for clear skies.
• Scalability and Cost: As with any new energy tech, scaling from a lab device to a commercial panel involves huge cost and engineering challenges. Manufacturing techniques need to be developed to produce large-area thermoradiative cells or integrate them into existing solar panels. Currently, exotic semiconductor fabrication (like that for infrared detectors) would be prohibitively expensive per square meter. The devices may also need encapsulation and protection from the environment (like traditional solar panels have glass covers, which incidentally must be IR-transparent in this case). Additionally, the Stanford-style approach that uses thermoelectrics faces cost issues: TEG modules often use rare materials (bismuth telluride, etc.) and aren’t cheap. “We haven’t done a detailed cost analysis, but… you’d have to compare a 24-hour solar panel with our system vs. a normal panel plus a battery,” Prof. Fan noted spectrum.ieee.org. If thermoradiative or TEG components are too pricey, plain batteries might win out for energy storage in many cases. The hope is that for certain applications (like long-lived sensors or satellites where battery replacement is tough), the higher upfront cost could be justified by maintenance-free night power spectrum.ieee.org.
• Competition with Other Solutions: Nighttime solar is not the only way to tackle the intermittency of renewable energy. Batteries, thermal storage, and other energy storage technologies are rapidly advancing and dropping in cost. By the time nighttime solar panels are efficient and mass-produced, batteries might be so ubiquitous that a niche “night panel” isn’t worth it except in special cases. There are also other approaches like thermal diurnal engines (e.g. running a Stirling engine at night from stored heat) or simply building oversized PV plus storage. Nighttime solar will need to find where it has a clear advantage – likely in low-power, long-duration applications where maintenance-free operation is crucial (again, space, remote sensors, etc., rather than grid-scale power in cities). Its success may hinge on hitting performance levels where it can meaningfully reduce battery cycling or provide power where others can’t.

Market and Commercialization Outlook

Thermoradiative technology is still in the R&D phase, but its future market potential is generating buzz. In the near term (next 5–10 years), we can expect limited, specialized commercialization rather than widespread consumer products. For instance, a likely first market is space and defense: if the Air Force-backed tests succeed, manufacturers of satellites or high-altitude drones could adopt thermoradiative auxiliary power to extend mission durations nature.com. This would be a low-volume, high-value market to kickstart production. Governments might fund early units for spacecraft or remote scientific stations (e.g. Antarctic research bases that endure polar night could benefit from night generators to supplement wind or diesel generators).

Another possible early adopter is the Internet of Things (IoT) and sensor industry. Companies deploying remote sensors (wildlife monitors, seismic sensors, etc.) could integrate night-harvesting cells to keep their devices running continuously. We might see startup companies forming partnerships with research labs to develop “battery-free” sensor solutions that use day/night thermal power. Indeed, the concept of perpetual environmental sensors that don’t need battery swaps is attractive – a niche that thermoradiative tech could fill if it matures spectrum.ieee.org.

Integration with solar panel manufacturing is a longer-term prospect. One could imagine major solar panel manufacturers like First Solar or SunPower, down the road, offering hybrid panels with a thermoradiative layer on the underside. During the day, the top side does normal PV; at night, the underside diode (or the PV cell in reverse bias) generates a trickle of power. Such dual-function panels might appeal for off-grid installations or critical infrastructure that values even small nighttime power. However, significant R&D is needed to make this seamless and cost-effective. As Ekins-Daukes noted, industry engagement will be crucial: “If industry can see this is valuable, progress can be extremely fast”, but until then, it’s mostly in university labs unsw.edu.au.

Right now, government and academic funding is driving the progress. Aside from the U.S. Air Force project, agencies like the U.S. Department of Energy (DOE) or Australia’s ARENA may start investing in “night solar” research as part of broader renewable energy programs. The technology intersects with areas like advanced photovoltaics, thermal energy, and materials science – all of which have funding streams. At UNSW, the research has been highlighted as a major innovation, helping the university secure grants and industry interest qpvgroup.org qpvgroup.org. It’s likely that in the next few years, we’ll see university-industry partnerships or startups forming to explore commercial prototypes. The timeline for any mass-market product is uncertain – researchers themselves say it could be a decade or more for significant commercial rollout unsw.edu.au – but smaller-scale uses could emerge sooner.

In terms of market size, if thermoradiative panels achieved even a fraction of their theoretical performance, they could complement the multi-billion-dollar solar industry. They won’t replace conventional solar (which will always deliver more power in daytime), but they could carve out a supportive niche. For example, the value proposition might be: install X square meters of night-panels alongside your solar array to get Y extra watt-hours each night, reducing battery needs by Z%. If that math is favorable in certain scenarios (and the cost per m² of night-panels drops with scale), there will be customers. Additionally, unique markets like wearable electronics or medical implants could be significant if the technology can be miniaturized and made biocompatible. Imagine a pacemaker that recharges itself from body infrared emission – that would be a highly valuable device in healthcare, albeit requiring rigorous testing and approvals.

The Road Ahead: Future Outlook

Technically, the future outlook for nighttime thermoradiative power is one of steady, incremental improvement – much like early solar cells in the 20th century. Researchers are optimistic but realistic. In the next few years (by the late 2020s), we will likely see efficiencies creep upward from the current proof-of-concept level. Each factor of ten increase in power output will open new application possibilities. Achieving, say, 1 W/m² at night (which some theoretical calculations suggest might be possible with improved radiative cooling and materials spectrum.ieee.org) would make a big difference in practicality. Shanhui Fan’s calculations indicate that with optimized thermal emission properties, a few hundred milliwatts to 1 W per square meter could be attainable spectrum.ieee.org. That’s still small, but at that point a modest array could power more meaningful devices continuously.

On a roughly 10-year horizon, if research hits its goals, we might see small-scale commercial adoption. Perhaps by the mid-2030s, remote sensors or specialty solar panels with built-in night generation could be on the market. The efficiency could potentially reach a few percent (versus effectively ~0% now) if a breakthrough material is found. A lot will depend on whether a killer application emerges that absolutely needs this technology and is willing to pay for it even when it’s expensive. Space applications might be that driver, since they have urgent need and high willingness-to-pay for even slight performance gains. If a satellite mission in 2026 demonstrates that a thermoradiative diode can run, say, a small heater or instrument during orbital night, it will attract more aerospace investment.

Commercially, widespread use will depend on cost reductions. That hinges on materials and manufacturing scaling up. It’s worth remembering that traditional solar panels took decades to drop in price by orders of magnitude; now they’re one of the cheapest power sources on Earth, but only thanks to massive investment and scale. Nighttime solar might follow a similar learning curve if given the chance. The involvement of industry players – perhaps companies in the infrared sensor field or solar firms diversifying – will accelerate the transition from lab to fab.

We may also see hybrid systems in the future. For example, a clever design could combine a thermoradiative diode with a thermal storage system: store heat in a material during the day and then use that heat at night to keep the diode generating power even if the air is cold. This would be like a continuous thermal engine but using radiative output. Concepts like pointing a thermoradiative panel at a terrestrial heat reservoir (e.g. warm ground or water that retained heat from daytime) could boost output at night beyond what the atmosphere alone allows ucdavis.edu. Such innovations might improve the capacity factor of the system.

In summary, thermoradiative “night solar” technology is at a stage comparable to where conventional photovoltaics were many decades ago: scientifically proven, with obvious limitations, but a clear roadmap for improvement. It targets a fascinating goal – solar power when there is no sun. As one science writer quipped, it’s like “harvesting starlight (or rather Earth-light) to keep our devices running after dark.” Each year from 2023 onward has brought new progress: from the first watts in the lab to plans for space trials. If that pace continues, who knows? In a decade or two, your rooftop solar array might also sport an after-hours thermoradiative layer, quietly converting the chill of the cosmos into a few extra watts to light your home at night. As Prof. Ekins-Daukes remarked, “when I talk to people about it, they often respond: ‘Wow, you mean this is possible?’” nature.com. Yes – it is possible. It will take ingenuity and investment to make it practical, but nighttime solar is no longer science fiction; it’s a steadily emerging reality, turning the darkness into an opportunity for power. abc.net.au nature.com

Sources: University press releases and news (UNSW Sydney unsw.edu.au unsw.edu.au; UC Davis ucdavis.edu), Nature Photonics and ACS Photonics research papers via Nature and UNSW reports nature.com nature.com, IEEE Spectrum and ABC News interviews with researchers spectrum.ieee.org abc.net.au, and other scientific journalism and publications as cited above.