Low-orbit constellation expansion, crystalline silicon cells return to the competition

A set of P-type heterojunction modules has entered the predetermined orbit. Whether the cost advantage of terrestrial photovoltaic can be converted into savings on satellite power supply bills depends on how much power remains several years later.

Recently, a set of P-type heterojunction (P-HJT) modules independently developed and packaged by JA Solar was launched from Jiuquan aboard the Kuaizhou-11 carrier rocket and entered the predetermined orbit.

This marks JA Solar's first in-orbit test of P-HJT modules. According to the plan, the company will compare the in-orbit data with the results of ground simulation tests to evaluate the reliability and power attenuation of this crystalline silicon technology route in the low-orbit environment.

The reason why terrestrial photovoltaic enterprises begin to send products into space points to a direct commercial question: how much money can the crystalline silicon cell's existing cost advantage on the ground save for satellite power supplies?

The mass deployment of low-orbit constellations provides application space for low-cost cells. However, the low cost of cell slices is only the starting point of calculation. To improve efficiency and radiation resistance, solar wings may require a larger area and more protective materials, which will correspondingly increase structural weight and launch costs.

This test by JA Solar will provide the first batch of in-orbit data for this accounting.

First, Check the Power Generation Capacity at the End of Life

Terrestrial photovoltaic modules are exposed to rain, snow, sand and dust, and long-term sunlight. After entering orbit, the materials face another set of working conditions.

Satellites travel between the sunlit zone and the Earth's shadow zone, and the modules repeatedly undergo thermal cycling. Space radiation will damage cell materials and cause output power attenuation. The vacuum environment, atomic oxygen in specific orbits, and the difference in thermal expansion of different materials will affect the encapsulation layer and electrical connections.

Terrestrial power stations can overhaul and replace modules, but satellites usually do not have such conditions after launch. The power supply design must leave a margin in advance to ensure that when the mission is nearing its end, the remaining power can still support the operation of the payload and platform.

Therefore, space solar cells have a key indicator — end-of-life power. The efficiency before launch must be considered together with how much power can be retained after several years.

Through this test, JA Solar aims to confirm whether the attenuation rate of P-HJT modules in real orbit is consistent with the results predicted by ground irradiation, temperature cycling and other tests. The deviation between the two will affect the subsequent product protection design, power margin and applicable service life.

According to JA Solar's disclosure, space photovoltaic is still in the stage of exploration and verification, there are no relevant orders at present, which has no substantial impact on the operating performance at this stage, and there is great uncertainty in large-scale commercialization.

The value of the in-orbit test lies in allowing the R&D team to obtain operation data that is difficult to be fully replaced by ground simulation. To what extent the data is accumulated and how long the design life can be supported still needs to be judged in combination with the specific orbit and test results.

Recalculate the Power Supply Cost for Low-Orbit Constellations

It is not the first time that crystalline silicon cells have been sent into space.

Early spacecraft widely used silicon cells. Later, multi-junction III-V cells with better efficiency and radiation resistance gradually became the mainstream, including the technical routes generally collectively referred to as "gallium arsenide cells". The European Space Agency recorded this replacement process when introducing the evolution of space solar cells.

Multi-junction cells use different materials to absorb light of different bands to improve the utilization rate of solar energy. NASA's small satellite power supply materials list 3- to 5-junction III-V cells as the mainstream technology for space applications, with a typical conversion efficiency of about 30%, and some products have higher efficiency.

The difference in efficiency will be directly reflected in the solar wings. For the same power supply demand, the higher the cell efficiency, the smaller the required area, and the more margin there is for the stowage, deployment and structural design of the solar wings. Better radiation resistance helps reduce power loss during long-term operation.

For spacecraft with high cost and long service life, spending more money during procurement in exchange for a smaller array area and more sufficient reliability basis has its engineering rationality. The accumulated flight records of mature space cells can also reduce the risk of adopting new products for specific models.

The procurement conditions for low-orbit constellations are different.

Hundreds or even more satellites are continuously produced, launched and supplemented to the network, and the cell cost will accumulate with the procurement scale. Whether suppliers can deliver on schedule and whether the performance of different batches is consistent will also affect the production of the entire satellite. Some missions have a relatively short designed service life, and their demand for long-life performance is different from that of traditional large communication satellites.

Therefore, crystalline silicon cells have gained a new opportunity to participate in competition. The terrestrial photovoltaic industry has established a large-scale manufacturing, automated production and material supply system. If space products can reuse part of the processes and supply capacity, it is possible to reduce manufacturing costs.

However, thinning, radiation-resistant design, dedicated encapsulation, screening and quality traceability may all add new processes and costs. How much of the terrestrial manufacturing advantage can be retained in the end depends on the production scheme after the product is finalized.

The greater variable lies outside the cell.

If the efficiency of crystalline silicon cells is low, a larger solar wing may be required to meet the same power supply requirement; if the in-orbit attenuation is fast, the initial power needs to be increased during design. After the array area is expanded, the structure, deployment mechanism, attitude control and launch mass all need to be recalculated.

The money saved in cell procurement may be offset by these additional costs, or there may still be a balance. The result depends on the satellite's orbit, service life, power demand and structural design, and cannot be summarized by a general cost reduction ratio.

Whether P-HJT can be applied depends on the extent to which it can reduce the cost of the entire satellite.

JA Solar still needs to use in-orbit data to prove that P-HJT modules can retain cost advantages after meeting the power supply and service life requirements of satellites. It may be first applied to low-orbit satellites with short service life and high cost pressure, but from test to batch supply, it still needs to be verified by satellite customers.

This article is from the WeChat official account "Xingdong Wuji", author: UniLym, authorized for release by 36Kr.