Solar Power From Space
The idea of solar panels circling Earth and beaming down power is gaining traction
Susan Hassler: Let’s think about a concept that’s firmly in the “maybe” category: space-based solar power stations.
Phil Ross: This idea has been out there for a while. In fact, the sci-fi author Isaac Asimov wrote about orbital power stations in a short story published way back in 1941.
Susan Hassler: Remind us—what happened in that story?
Phil Ross: Okay. Well, two engineers at an orbiting power station were training a robot to take over operations. It would watch over the solar panels that sucked up energy from the sun, and it would control the beam that transmitted that energy back to Earth. But the robot went a little crazy.
Susan Hassler: Ah, okay. But, crazed robot aside, how likely is it that we’ll see these orbiting power stations in the real world?
Phil Ross: Good question. And that’s what Eliza Strickland is here to tell us about.
Eliza Strickland: All right, I know this idea is a little “out there,” but the researchers involved swear we could have these power stations in orbit by 2030—if they can overcome some technical and economic challenges.
Susan Hassler: Who exactly is working on this?
Eliza Strickland: A couple of different space agencies and private companies are tinkering with experimental systems. But JAXA, the Japan Aerospace Exploration Agency, has pursued it the most aggressively. So I went to Japan, and started my reporting by taking the train to JAXA’s Sagamihara research campus, about 30 miles outside downtown Tokyo.
Eliza Strickland: Sagamihara is a sleepy suburb, and only a few people disembarked at the train station. I took a cab through the quiet streets to the JAXA campus. The lobby of the main building was filled with models of JAXA’s rockets, satellites, and space probes, and videos showcased the space agency’s most successful missions.
Eliza Strickland: JAXA has been researching space-based solar power systems for decades. Japan has compelling reasons to take this sci-fi idea seriously. It has to import all of its fossil fuels. The island nation lacks the land for sprawling solar or wind farms on the ground. So I sought out the researcher who’s been planning Japan’s out-of-this-world solution. I found him in an office decorated with illustrations showing solar panels hovering in space, high above the Earth.
Susumu Sasaki: My name is Susumu Sasaki at JAXA, the Institute of Space and Astronautical Science.
Eliza Strickland: Sasaki, a serious man with shaggy hair and big glasses, explained the major advantage of putting solar panels in orbit, about 22 000 miles above the Earth’s surface: Up there, the sun is always shining.
Susumu Sasaki: On the ground we have day and night, so we cannot get power on ground at night. And also cloudy days, we cannot get power on ground. But in space, there are no such kind of weather problems; we can get the power all the time in space. So we can get power constantly, all day, all the year. It’s very stable.
Eliza Strickland: In his office, Sasaki pulled the plastic wrap off a model of a space power system, which he calls an SPS. The model consisted of a square receiving station about the size of a chessboard, which was decked out with a few circuit boards and a tiny light. There was also a separate solar panel.
Susumu Sasaki: This is a small unit to demonstrate the principle of the SPS, especially in the orbit site, the space site. It’s consisting of the solar cell, here.
Eliza Strickland: He held a solar panel up to the sunlight streaming in through the window. This solar panel converted sunlight to electricity, which then flowed into an attached microwave converter. That’s a standard piece of technology that converts the electricity into microwaves, and it’s the same technology that makes your microwave oven work. Next, a transmitting antenna sent those microwaves wirelessly, through the air, to a receiving antenna on the square receiving board. On the board, a little green light flickered on. Sasaki pointed proudly to the tiny light.
Susumu Sasaki: The microwave comes from this antenna. This is just a demonstration. So this small light illuminates, getting the microwave power like this.
Eliza Strickland: Wireless power transmission is easily done over short distances, but it’s a tricky technical challenge when you scale up. For the space system, researchers will have to aim the microwave beam across thousands of miles so that it precisely hits the receiving antenna, which is called the rectenna. JAXA has plans for a series of demonstration projects, first on the ground and then in space. If all goes well, the agency wants to build a full-scale space-power station by 2030 or 2035. That station would be capable of providing 1 gigawatt of power, about the same amount as a nuclear power reactor. I asked Sasaki if he thinks the bright lights of Tokyo will really be kept on by space-based solar power one day.
Susumu Sasaki: I believe so! I believe so. In Tokyo we cannot have that large rectenna, but in Tokyo Bay area or the seashore, maybe we can have that kind of rectenna site, and we can get the power from that, freely, and with no hazard.
Eliza Strickland: Sasaki invited me to come back for a visit in 2035, when he hopes he’ll be able to give me the grand tour of a real power receiving station.
Eliza Strickland: Sasaki may be Japan’s biggest champion of space-based solar power. But I soon found out that there are true believers in the United States as well.
Gary Spirnak: I’m Gary Spirnak, I’m the president and CEO of Solaren Corporation. We’re based in Manhattan Beach, California.
Eliza Strickland: Inside Solaren’s bright and airy headquarters, designers are laboring over blueprints, and engineers in the electronics lab are tinkering with solar panels and microwave converters.
Gary Spirnak: Basically, we were formed by a team of satellite engineers and space scientists to build a space energy company, and to generate and distribute electricity at competitive prices from the space solar power stations in Earth orbit.
Eliza Strickland: Solaren has a power contract with the California utility company Pacific Gas & Electric and is planning to build its first power-receiving station in central California.
Gary Spirnak: They get electricity, and we get paid.
Eliza Strickland: You may be wondering whether it’s safe to send a beam of microwaves into the middle of California. But Spirnak explains that the only concern is how much the microwaves will heat up whatever they hit. He says the beam is so diffuse that it poses no threat to birds or planes flying through.
Gary Spirnak: The peak part of that beam is less than 20 milliwatts per centimeter squared. So what does that mean? Well, the noontime sun is about 100 milliwatts per centimeter squared. So a plane that’s in clouds, and flying out of clouds and into the sun, will get five or six times the amount of heat on it as flying through the most dense part of our beam.
Eliza Strickland: The company is currently designing the solar panels that would be launched aboard an unmanned rocket and which would unfold in orbit. That orbital system would be pretty big, with the transmitting antenna alone measuring about the length of nine football fields. But building a massive system is the only way to make the economics work out.
Gary Spirnak: All our plants are planned to be profitable. These space solar power plants, they’re large-scale operations. As you might imagine, it takes a lot of money to launch things in space, hundreds of millions of dollars, so you have to be large enough to generate enough revenues to pay for these things.
Eliza Strickland: Spirnak believes that these orbital power stations will be a fact of life pretty soon.
Gary Spirnak: By the end of this decade we’re going to have space solar power plants that are operational. And then as we get into the 2020s, we’ll see those plants put into production.
Eliza Strickland: And what does he think about the skeptics, the people who say this will never happen?
Gary Spirnak: We don’t consider them skeptics; we think of them as future space solar electricity customers.
Eliza Strickland: From the futuristic solar-powered frontier, I’m Eliza Strickland.