Posted on November 5th, 2016 in solar by Spencer R.
Think about what you know about clean sources of energy. What’s the greenest?
Hydroelectric, geothermal, wind and solar all probably spring to mind. Environmentally friendly though they may be, they all have significant limits on how much energy they can produce and where they can be used. To wit, despite some really cool advances in solar, solar panels still can only generate energy while the sun shines.
The solution, then, is obvious. Go where the sun never sets: in space.
That’s the vision of scientists, researchers and entrepreneurs both here in the United States as well as in Japan, China and Europe. Though the concept has been batted around at least since the 1970s, it’s been repeatedly revisited and abandoned because getting all the parts up there, and the people to put it all together, was impossibly expensive. Only with the advent of super small, mass-produced satellites and reusable booster rockets are some beginning to take a much harder look at making space solar a reality.
There are dozens upon dozens of ideas for how to build a space-based solar collection system, but the basic gist goes something like this: launch and robotically assemble several hundred or thousand identically sized modules in geosynchronous orbit. One part comprises mirrors to reflect and concentrate sunlight onto solar panels that convert the energy into electricity. Converters turn that electricity into low-intensity microwaves that are beamed to large, circular receivers on the ground. Those antennae re-convert the microwaves back into electricity, which can be fed into the existing grid.
John Mankins, who spent 25 years at NASA and Caltech’s Jet Propulsion Laboratory, received funding from NASA’s Institute of Advanced Concepts in 2011 to refine his space solar power plant concept in greater detail. The technology and engineering required to make space solar a reality already exists, he insists, but as with any expensive new idea, it comes down to greenbacks and gumption.
“It’s not like fusion—there’s no new physics involved,” Mankins says, referencing ITER, the 35-nation collaboration to build a fusion reactor in France. “There’s no secret sauce. It’s a financial hurdle to get funding to develop the elements and demonstrate the new architecture required to do this.”
Mankins and others estimate the total cost for developing, building, launching and assembling all the components of a space-based solar power plant is on the order of $4 to $5 billion—a fraction of the $28 billion price tag on China’s Three Gorges Dam. Mankins estimates a working scale model with full-sized components could be had for $100 million. By comparison, the Tennessee Valley Authority’s recently completed Watts Bar nuclear plant took 43 years to build, from start to stuttering finish, and cost $4.7 billion all told.
Critically, what consumers would pay—the price per kilowatt-hour—needs to be in the same ballpark as conventional sources of energy produced with coal, natural gas and nuclear, which range in price from 3 to 12 cents per kilowatt-hour. Hydroelectric can be staggeringly cheap, at less than one cent per kilowatt-hour—but only if you’re lucky enough to live in a region with abundant high-flow rivers, like in parts of Canada and Wisconsin. Geothermal is very economical too, checking in at 3 cents per kilowatt-hour, but you’ll need to ask the Icelanders how they like their power bills. And wind advocates trumpeted the news last year that costs for that renewable resource had plummeted to 2.5 cents per kilowatt-hour.
Getting the cost into the low double digits or even single digits of cents per kilowatt-hour is absolutely essential to make space solar a competitive utility, says Gary Spirnak, CEO of the California-based energy company Solaren.
Spirnak’s company is approved as a solar energy provider in California, and has had past supply arrangements with Pacific Gas and Electric, but its business model is completely based on generating their power from space-harvested solar. Solaren is in the process of negotiating new agreements with one or more utilities. The company has patents here in the U.S. for its design as well as in Europe, Russia, China, Japan and Canada, and has secured a first round of financing for a lab-based demonstration of its component technologies sometime in the next year. Spirnak hopes to convince investors to support a 250-megawatt pilot plant by the end of the development and testing phase, perhaps within five years.
Two keystone structures are required for space solar to work. First, solid-state power amplifiers that efficiently convert electricity from collected sunlight into radio-frequency waves, and receivers on the ground that re-convert the RF waves back into electricity.
Paul Jaffe, an engineer at the Naval Research Laboratory in Washington, D.C., worked on two prototypes of the collection module, which he refers to as a “sandwich” since the solar collector, power converter and RF emitter are all smashed together into a foot-square tile two inches thick. The weight of each individual module ultimately determines the pricing of the distributed electricity on the ground; in terms of watts per launched kilogram, Jaffe says the basic tile design came in at around 6 watts per kilogram.
Taking into account that power output, a 20-year solar power plant lifetime, a launch cost of $2,500 per kilo, and different cost levels of the components themselves, Jaffe calculates that if the mass decreased and wattage increased to 500 watts per kilo, that equates to a cost of 3 cents per kilowatt-hour.
“Doing even really simple things to reduce the mass gets us into the 100 watts per kilogram range, and 1,000 watts per kilogram isn’t crazy,” he says. “You get very good efficiencies with current solar technology that’s already commercially available, and we carry around these very efficient, lightweight RF converters in our pockets every day.”
RF converters are the very reason cell phones work—phones are basically glorified walkie-talkies whose signals are helped along by a network of signal relay stations. The converters in the phone translate radio waves into data that we understand—audio—and vice versa. This technology is central to research into space solar at Caltech, in a collaboration between scientists and engineers there and Northrop Grumman.
Spirnak says the main thrust of Solaren’s work in recent months has been just that—reducing the weight of their modules. Though reusable rockets would knock the overall production cost down even further, Spirnak isn’t holding his breath in the near term; he’s figuring on using conventional heavy lift vehicles to get Solaren’s components into space.
“We spent a lot of time ruthlessly taking weight out of the system,” Spirnak says. “We can package individual large elements into single launchers, with some interesting feats of origami," though delivering the entire system into space will still require multiple super-heavy launchers.
Jaffe says the single most common question he gets when talking about space solar isn’t whether it can or should be done, but how dangerous that energy beam from space is. Won’t it flash-fry birds and planes in the sky when they pass through the beam?
“If you sit outside on a sunny afternoon for 15 minutes, you don’t get burned,” he explains. “Our radios, TVs and cell phones aren’t cooking us, and those are all at the same frequencies as what’s being proposed. There are already safety limits [on microwave transmissions] set by IEEE [Institute of Electrical and Electronics Engineers], so you design a system to make sure the power is spread over a large area. It won’t accidentally turn into a death ray.”
To get the best cost-to-weight ratios, efficiencies of scale, and have comparable electrical generation capacity of an average nuclear power plant (1 to 2 gigawatts), any solar collection array in space would need to be roughly a kilometer in diameter.
Collection receivers on the ground would need to be accordingly large—for a space-based solar plant to generate around one gigawatt of energy, a one-kilometer (.62 mile) solar collector would beam energy to a 3.5-wide kilometer (2 mile) receiver on the ground. That would require an area of around 900 acres. Compare that with the Solar Star solar panel plant in California, currently the United States’ largest solar utility, which occupies 3,200 acres.
Radio-frequency power transmission does have one significant drawback: the “safe” wavelengths that also won’t get refracted by something as simple as rain are already overcrowded, clogged up through regular radio transmissions, as well as military, industrial and satellite use.
Critics of space solar, prominent among them Tesla’s Elon Musk, say economy-scale efficiencies just can’t be achieved because of all the converting and reconverting of the power that is required.
But Jaffe is hopeful that the old crack on fusion won’t also become true of space solar: “It’s been 10 years away for the last 60 years,” he laughs.
Mankins stresses that with the global population forecast to explode to 11.3 billion by the end of the century, with almost all of that represented in the developing world, space solar deserves serious investment by public entities as well as private partners. He says abundant clean energy is necessary to fulfill basic human needs, as well as address the assured environmental destruction if all of that energy comes from conventional sources.
“If the mix of energy sources does not change radically, there is no way we’ll get to carbon neutral,” Mankins says. “You also can’t tell 800 million people in China that they must stay in abject poverty. There’s a need not just to offset today’s carbon use, but to look forward 70 years and to how we’ll offset three times today’s use. We really need big solutions.”
Posted on October 11th, 2016 in solar by Spencer R.
Researchers continue to make progress in large-scale storage of solar energy for use when the sun’s not shining. The latest comes out of the Universidad Politecnica de Madrid (UPM), where scientists have developed a thermal-based system that uses an abundant natural material, molten silicon, to store energy generated by the sun.
The system developed by researchers from the university’s Solar Energy Institute can store up to 10 times more than existing similar solutions, according to researchers, and it could one day be coming to a city near you. That’s because the team aims to develop a series of next-generation, low-cost solar thermal stations based on the system—which currently has patent-pending status in the United States—to store electricity in urban areas.
Solar thermal energy storage solutions store sunlight as heat molten salt, then convert the energy into electricity on demand using a thermal generator. The key difference in the solution developed by the UPM team from others is its use of molten silicon, the most abundant element in the Earth’s crust, researchers said. This makes it a plentiful, natural, low-cost, and safe resource for use in storing solar energy, they said.
The solution developed by the team takes solar energy and stores it in the form of heat in molten silicon at a very high temperature, around 1400°C (2552°F), said Alejandro Datas, the research promoter of the project.
“At such high temperatures, silicon intensely shines in the same way that the sun does, thus photovoltaic cells—thermophotovoltaic cells in this case—can be used to convert this incandescent radiation into electricity,” he explained. “The use of thermophotovoltaic cells is key in this system, since any other type of generator would hardly work at extreme temperatures.”
Indeed, silicon has properties that allow for storage of more than 1 mW per hour of energy in a cubic meter—10 times more than storage systems that uses salt, Datas said. The UPM system thermally isolates molten silicon from its environment until the energy is demanded and, when this occurs, the stored heat is converted into electricity.
The UPM team is manufacturing the first lab-scale prototype of the system and expect that the first application will be in the solar thermal energy sector. For future applications the system also is well suited to storing electricity in the housing sector and to provide and manage electricity and heating in urban areas.
Posted on October 8th, 2016 in solar by Spencer R.
The potential of solar power is significant, with the International Energy Agency previously stating that the sun could be the planet’s biggest source of electricity by 2050.
In the U.K., the appetite for solar among some is becoming increasingly stronger. “We’re in the middle of what you can only describe as an energy revolution in the U.K.,” Alan Whitehead, member of parliament for the opposition Labour Party, told CNBC.
“Solar power is now becoming increasingly central to U.K. power production,” Whitehead added. “The deployment of solar is racing way ahead of what was thought was going to be the curve, and it’s now making a real impact on energy systems.”
The U.K. is home to what is claimed to be the largest floating solar panel array in Europe. The array, based in the south of England, was installed by Lightsource Renewable Energy. The array is set to generate 5.8 million kilowatt hours in its first year of operation.
Commenting on the benefits of solar in general Nick Boyle, founder and CEO of Lightsource Renewable Energy, said the business was, “now in a position for the first time – and it’s a really interesting inflection point – where I can go to large electricity users and offer to undercut what they’re paying today.”
Boyle went on to explain that the predictable nature of solar meant that it also generated a predictable revenue stream, making it an attractive investment product.
For Lightsource, there are several plus points to floating solar arrays. “One of the major benefits to floating solar is that there is all this space in areas of London or other cities, where you have a large area on top of the reservoir that’s not being used,” Liv Harder, senior development manager at the company, said.
“It has definitely become more affordable to do projects like these over the last few years,” Harder added. “The cost of panels has gone down nine times in the last five (years) alone, and the floats themselves also continue to go down in price as more and more installations go up.”
In the U.S., the solar industry seems to be in good health. At the beginning of this year it was revealed that the U.S. solar industry installed 7,286 megawatts of solar power in 2015, according to data from GTM Research and the Solar Energy Industries Association.
The figures represent an increase of over 1,000 megawatts of solar photovoltaic installations compared to 2014. Photovoltaic technology is able to directly convert sunlight into electrical energy.
According to the data, solar beat natural gas capacity additions for the first time ever, with 29.5 percent of all new electric generating capacity met by solar power in 2015.
Back in the U.K., Alan Whitehead was also confident about solar’s prospects. “The future of solar power is incredibly bright,” he said. “Solar has a wonderful future I think, it’s one of those technologies that is absolutely game changing.”