The satellite operating in a test orbit for the feasibility of solar energy collection and transmission technology to Earth has successfully completed its year-long mission.
According to a mission summary released by the California Institute of Technology (Caltech) on January 16, engineers behind the Solar Space Power Demonstrator (SSPD-1) project reported that all three devices on the 50 kg satellite prototype functioned successfully. They are confident that the project “will pave the way for solar energy in space,” according to Popular Science.
Simulation of the Solar Space Power Demonstrator in low Earth orbit. (Image: Caltech).
Launched on a SpaceX Falcon 9 rocket in early January 2023, SSPD-1 conducted a trio of experiments. First, the Deployable on-Orbit ultraLight Composite (DOLCE) experiment assessed the durability and efficiency of ultra-lightweight solar panel structures inspired by origami. Meanwhile, the ALBA experiment tested 32 solar panel designs to determine which was most suitable for space. Concurrently, the Microwave Array for Power-transfer Low-orbit (MAPLE) tested microwave transmission equipment to send solar energy collected in orbit back to Earth.
Most importantly, MAPLE demonstrated for the first time that solar energy could be collected using solar panels and transmitted back to Earth via a microwave beam. Over more than eight months, the SSPD-1 team intentionally increased pressure testing on MAPLE, which led to a decrease in energy transmission capability. The research team then simulated the issue in the laboratory, identifying the cause in complex electro-thermal interactions and the degraded performance of each component in the assembly.
Ali Hajimiri, co-director of the Space Solar Power Project (SSPP) at Caltech and professor of electrical engineering and medical engineering, stated that the results will help refine the design of many MAPLE components to maximize long-term performance.
Today, solar panels used on satellites and many other space technologies are over ten times more expensive to produce than those used on the ground. Caltech explains this is primarily due to the additional cost of a protective crystalline film layer known as the external layer growth. Through ALBA, researchers found that even promising designs on Earth, such as perovskite solar panels, exhibit significant performance discrepancies in space. In contrast, gallium arsenide panels operate stably over long periods without the need for an additional film layer.
For DOLCE, the research team acknowledged that not everything went according to plan. While the initial intention was to deploy in 3-4 days, DOLCE encountered numerous technical issues such as wiring faults and mechanical component failures. However, researchers found ways to troubleshoot problems using cameras on the satellite to simulate malfunctions in the laboratory.
Even with the successful conclusion of SSPD-1, it will be many years before solar energy can be efficiently harvested at an affordable cost via satellites. Previous estimates suggested that space solar energy could cost between $1 and $2 per kWh, while current prices in the United States are below $0.17 per kWh. Material costs need to be significantly reduced while still being durable enough to withstand solar radiation and geomagnetic activity in space.
There are many other issues that need to be addressed before solar energy in space can contribute to humanity’s sustainable energy infrastructure. The amount of electricity transmitted by SSPD-1 via a microwave beam is minuscule compared to daily consumption, and solar panels in space must span thousands of meters. Safety concerns regarding the transmission of microwaves and powerful lasers to Earth are also noteworthy. The research team at SSPP is working hard to find solutions to all these challenges before an orbital solar farm becomes a reality.
