This paper presents a comprehensive comparison of the photovoltaic power generation systems aboard the International Space Station (ISS) and the Chinese Space Station (CSS). Key parameters including photovoltaic array specifications, power system output, structural configurations, cell technologies, energy storage, and power supply capabilities are analyzed to highlight the technological characteristics and operational differences between the two space stations.

1.Photovoltaic Array Power, Voltage, and Current

1.1International Space Station (ISS)

The ISS features four large solar array wings, with each wing originally capable of generating over 30 kW, resulting in a total nominal power output of 124 kW (typically operating at around 80 kW under standard conditions)¹. These arrays operate at a DC voltage of approximately 160 V, which is stepped down to 124 V via DC-DC Converter Units (DDCU) for station-wide distribution¹. Current levels vary with power demand, but peak current per array can exceed 187 A (calculated from 30 kW / 160 V).

Image source: Sohu News. "Does the International Space Station have power stations or other power-generating equipment?"

https://m.sohu.com/a/374148541_120085179/

In 2021, NASA initiated an upgrade with new Roll-Out Solar Arrays (ROSA), increasing the total power capacity to 215 kW². These upgraded arrays maintain compatibility with the existing 124 V distribution system while improving efficiency during low sun angles².

Image source: China Manned Space Engineering Office. "NASA to upgrade International Space Station solar arrays."

https://www.cmse.gov.cn/hqsy/lydt/gjkjz/202101/t20210128_47565.html

The original solar panels of the ISS were likely sourced from multiple manufacturers. TecStar, for example, provided solar panels for the ISS's Interim Control Module (ICM) program in the past³. The components of the upgraded ROSA array are sourced from Spectrolab⁴.

1.2Chinese Space Station (CSS)

The CSS incorporates six groups of solar wings with a combined design power exceeding 100 kW⁵. Each solar wing operates at a DC voltage optimized for the station's power management system (specific values not publicly disclosed). With a total deployed area of 138 m² across its largest four wings (27m × 4m each), the CSS achieves high power density through advanced cell technology⁵. Current ratings are proportional to power output, with estimates exceeding 800 A at the main bus voltage (derived from 100 kW / 125 V assumption).

Image source: NetEase News. "Outdated design? China's space station 'lightweight' with 300-ton gap?" https://www.163.com/dy/article/K00LLU9705538JEM.html

Regarding the manufacturers of the CSS's photovoltaic components, while specific details are not extensively publicized, China has several leading domestic solar panel manufacturers. For instance, companies like SolarSpace, a Chinese tier-1 solar panel manufacturer founded in 2011, could potentially be involved. By the end of 2023, it had manufacturing capacities reaching 60 gigawatts of cells and 7.2 gigawatts of modules, with bases in Cambodia, Laos, and China⁶. Another possible candidate is XPower Solar Energy Co., Ltd, a clean energy provider specializing in high-performance PV modules with a global production capacity of 1 GW modules and two manufacturing plants in China⁷.

2.Structural Configurations: Stowed and Deployed States​

2.1ISS

Stowed Configuration: Original solar arrays were folded into compact sections for launch, while newer ROSA arrays are stored in cylindrical canisters (≈1m diameter × 6m length)².

Deployed Configuration: Each array wing spans 73 meters (240 feet) with a total area of 2,500 m² (27,000 sq ft)⁸. The eight arrays are distributed across the US Orbital Segment, mounted on rotating gimbals to track the sun¹.
 

Distribution: Four pairs of arrays extend from the station's truss structure, with Russian modules (Zvezda, Zarya) featuring smaller auxiliary arrays (Zarya's arrays are currently retracted)¹.

Image source: NASA. "Solar Arrays on the International Space Station."

https://www.nasa.gov/image-article/solar-arrays-international-space-station-2/

2.2CSS

Stowed Configuration: Solar wings are folded in a multi-stage, accordion-like structure to fit within launch fairings, utilizing lightweight composite materials for compact storage.

Deployed Configuration: Each wing deploys to 27m × 4m, with a multi-dimensional articulation system allowing ±180° rotation for optimal sun tracking⁵. The six wings are distributed: Tianhe, Mengtian and Wentian each have a pair⁵.

Distribution: Symmetric placement minimizes shading between modules, with wings extending perpendicular to the station's longitudinal axis.

3.Photovoltaic Cell Technologies

3.1ISS

Original arrays (1998) use silicon-based solar cells with ≈14% conversion efficiency⁵.

Upgraded ROSA arrays incorporate advanced triple-junction cells (likely GaAs-based) to improve efficiency, though specific materials remain undisclosed².

3.2CSS

Employs triple-junction gallium arsenide (GaAs) cells with >30% conversion efficiency^5,9.

These cells utilize indium gallium phosphide (InGaP), gallium arsenide (GaAs), and germanium (Ge) layers to capture multiple light spectra, critical for low-Earth orbit conditions.

Image source: NetEase News. "Outdated design? China's space station 'lightweight' with 300-ton gap?" https://www.163.com/dy/article/K00LLU9705538JEM.html

4.Battery Storage Systems

4.1ISS

The original battery was a nickel-metal hydride battery (Ni-H₂), consisting of 48 independent battery modules (ORU), with a total available energy of 96KWh for the entire energy storage system. In 2017, it was upgraded to a lithium-ion battery, with each nickel-metal hydride battery ORU replaced by a lithium-ion battery ORU, doubling the capacity and energy. The total available energy of the entire ISS energy storage system has been increased to approximately 192 kWh¹⁰.

These batteries store ≈60% of generated power during daylight periods to support operations during Earth shadow (≈35 minutes per orbit)⁸.

The nickel-hydrogen batteries on the ISS were sourced from multiple suppliers. As the ISS moves towards more advanced lithium-ion batteries, GS Yuasa Corporation's group company, GS Yuasa Technology Ltd. (GYT), has been manufacturing lithium-ion cells for the ISS since 2012¹¹.

4.2CSS

Each module of China's space station (the Tianhe module, the Wentian module, and the Mengtian module) has its own photovoltaic wings and independent energy storage systems. The systems use lithium-ion batteries. The Tianhe core module is equipped with six sets of lithium-ion batteries, the Wentian laboratory module with four sets, and the Mengtian laboratory module with four sets. The official has not disclosed the specific battery capacity. However, according to public reports and expert speculations, the capacity of each battery group is expected to be at the 100-200 Ah level, and the total available energy of the entire space station system is estimated to be over 100 kWh¹².

For the CSS, possible manufacturers of the lithium-ion batteries include CATL (Contemporary Amperex Technology Co., Limited), a global leader in lithium-ion battery production, and Spaceflight Power, which has experience in manufacturing various types of batteries^5,13.

5.Power Supply Capabilities

5.1ISS

Supports a maximum load of 124 kW (upgradable to 215 kW), powering life support, communication systems, and over 50 scientific experiments².

5.2CSS

Generates ≈1,000 kWh daily, sufficient for dozens of experiment cabinets and crew needs⁵.

The 100+ kW capacity allows for future expansion, including additional modules and high-power scientific instruments.

The ISS and CSS photovoltaic systems reflect their respective design eras and operational requirements. The ISS, with its larger array area and incremental upgrades, prioritizes legacy compatibility, while the CSS leverages advanced GaAs cells and modular design for higher efficiency. Both systems demonstrate robust solutions for sustaining human presence in low-Earth orbit.

Sources:

1.Sohu News. "Does the International Space Station have power stations or other power-generating equipment?" https://m.sohu.com/a/374148541_120085179/

2.China Manned Space Engineering Office. "NASA to upgrade International Space Station solar arrays." https://www.cmse.gov.cn/hqsy/lydt/gjkjz/202101/t20210128_47565.html

3.SpaceDaily. "TecStar Ships ISS Solar Panels." https://www.spacedaily.com/reports/TecStar_Ships_ISS_Solar_Panels.html

4."Boeing to Provide Six More Solar Arrays for International Space Station." https://boeing.mediaroom.com/news-releases-statements?item=130801

5.Wang Yanan (Aerospace Knowledge). "China Space Station 'power bank': 1 million yuan per square meter, generating 1000 kWh daily." http://m.toutiao.com/group/7161312038013190656/?upstream_biz=doubao

6.A1SolarStore. "SolarSpace solar panels review 2025: In-depth look." https://a1solarstore.com/blog/solarspace-solar-panels-review-in-depth-look-a1-solarstore.html

7.XPower Solar. "Leading Solar PV Modules Manufacturer | About XPower." https://www.xpowersolar.com/about/

8.NASA. "Solar Arrays on the International Space Station." https://www.nasa.gov/image-article/solar-arrays-international-space-station-2/

9.NetEase News. "Outdated design? China's space station 'lightweight' with 300-ton gap?" https://www.163.com/dy/article/K00LLU9705538JEM.html

10.Eugene Schwanbeck; Penni Dalton. "International Space Station Lithium-ion Batteries for Primary Electric Power System."

11.GS Yuasa. "GS Yuasa's Lithium-ion Cells to Be Delivered to the International Space Station for Fourth Time." https://www.gs-yuasa.com/en/newsrelease/article.php?ucode=gs200509534828_785

12.China's Manned Space Program. "Energy system of China's space station."

13.SolarFeeds. "Spaceflight Power 65 Ah, 100 Ah, 150 Ah, 250 Ah Lead Acid (AGM) Battery Capacity, Prices, Reviews." https://www.solarfeeds.com/battery/long-life-battery-series/