So you’re telling me that my electric car’s battery is in the paint?

What comes to mind when you picture a battery? The familiar Duracell Coppertop AA battery? A clunky  automotive battery? The small rectangular battery in your cell phone? Researchers at Rice University are reinventing the concept of batteries and battery packaging by creating a lithium-ion battery with spray paint. That’s right, your local neighborhood hoodlum taggers can now be more energy forward than you sitting at home watching Cops.

A team of researchers from Rice University have demonstrated in a paper in Nature Scientific Reports that special “spray paints” can be used sequentially to build up the layers needed to form a lithium-ion battery. A spray-on battery could be used on a variety of materials, both rigid and flexible. They point out that the technology could be coupled to energy conversion devices such as solar cells.

Simply put, a lithium-ion battery is created by tightly layering cathodes and anodes like in the image shown below. The researchers at Rice University replicate this cylindrical design in a customizable form using the spray coatings that they developed. They applied the battery painting process to a variety of materials including stainless steel, glass, ceramic tile, and flexible polymer sheets. An SEM image of a cross section of the battery is shown below. Each of the spray painted batteries performed as a typical battery. They even applied the spray paint to a coffee mug to spell out the name of their Alma mater while also storing energy. They added that more complicated surface geometries could be possible using different spray nozzle designs that are tailored to the different viscous properties of the paints.

The are a few drawbacks to a spray painted lithium-ion battery. For one, the materials are highly toxic, corrosive, and flammable, hence why they are always tightly packaged and hidden away in their conventional form. Secondly, the batteries are highly sensitive to oxygen and moisture. This sensitivity currently restricts their widespread use because they still have to be packaged like their conventional brethren, reducing their novel promise. A spray painted battery is shown below on a glazed ceramic tile alongside its final packaged form. One of the researchers’ next steps is to develop a sealing layer to protect the batteries from these elements. Because who wants to paint their electric vehicle with a new battery but then have the painter tell them that they always have to keep the car cover on.

Typical lithium-ion battery construction.

Conventional and spray painted lithium-ion batteries.

SEM image of spray painted lithium-ion battery cross section.

Glazed ceramic tile with spray painted battery prior to packaging (left) and post-packaging (right)

 

Solar Power in UAE

In one of the most energy rich regions of the world, Abu Dhabi, new energy is being built out for domestic use. However, this oil rich country has been focusing on developing renewable sources of energy. Their new 100MW solar plant will come online this month and electrify up to 20,000 homes in the region. Called Shams 1 after the Arabic word for sun, the project will be the largest solar plant of its type in the world.¹

Built using a technology called Concentrated Solar Power; this plant uses the sun to super heat liquid to turn steam turbines. Parabolic mirrors focus the sun’s light on an oil filled pipe. This super-heated liquid is then passed through water in order to heat and turn into steam. The steam is then passed through a standard turbine with the heated steam being condensed and returned to cycle again. The benefit of this process is the heated oil can be stored in tanks and used when sunlight is not available. This allows for electrical production to be spread out as needed.²

The solar plant has its own unique complications. Being built in a desert environment, the mirrors accumulate sand and dirt, reducing the ability to produce energy. In order to prevent this from becoming a major issue, automated trucks were developed that cleaned the mirrors and only need one worker walking in front. The truck detects the worker and follows behind cleaning the mirrors. Also taken into consideration is the conservation of water in the dry desert environment. Shams 1 was developed with this in mind with a dry cooling system to prevent water loss. In addition, a good amount of the water used to clean the mirrors is capture and recycled for later use. ³

Shams 1 is a joint venture between Total, Abengoa Solar, and Masdar. Developed at a cost of approximately $600M, the plant contains 258,000 mirrors on 768 tracking parabolic troughs. The plant sits on a 2.5 square kilometer field. At full capacity it is expected to power approximately 20,000 homes. The oil rich nation says the cost of the plant will be comparable to electricity generation produced from diesel. The advantage is now that United Arab Emirates is now freed up to sell their natural resources on the international market. This development is part of a larger goal of having 7% of energy production from renewable sources by 2020. The 100 megawatt facility will be approximately 0.5% of the estimated 20 gigawatts of domestic demand in 2020. ¹

Resources:

¹ http://www.gizmag.com/shams-1-worlds-largest-concentrated-solar-power-plant/26707/

² http://www.eere.energy.gov/basics/renewable_energy/csp.html

³ http://social.csptoday.com/emerging-markets/masdar-will-not-stop-shams-1

The Rise of Cheap Solar?

A recent report by McKinsey & Company, Solar power: Darkest before dawn, is forecasting an annualized drop in the underlying cost of solar PV cells by 10% per year from now through 2020.  This continued drop in the cost of solar manufacturing, when combined with a doubling of manufacturing capacity over the next 3 to 5 years, will result in an unprecedented expansion of solar power installation.  This mirrors the cost reductions seen over the previous 5 years, where panel prices have declined by approximately 75%, and growth in installed capacity from 4.5 GW in 2005 to 65 GW in 2012.

This dramatic drop in price has been the result of multiple, incremental improvements in each component of the installed cost of a system [1]:

This is in striking contrast to the co-incidental drop in the cost of natural gas over the previous decade, where a massive influx of supply due to the breakthrough technologies of horizontal drilling and hydraulic fracturing have produced a glut of supply, applying downward pressure on wholesale prices.  This precipitous drop in the price of natural gas in North America has led to lower market prices, and lower demand curves for all sources of electricity, including solar.

As solar continues it’s march to grid parity, McKinsey forecasts a price per watt (peak) installed of $1 by 2020.  This echos what US Secretary of Energy Stephen Chu has previously predicted:

“Before maybe the end of this decade, I see wind and solar being cost-competitive without subsidy with new fossil fuel.”

Additionally, using a conservative estimate of $2 per watt (peak) installed, McKinsey predicts 400 to 600 GW of capacity installation between 2012 and 2020.

Regardless of the pace of cost reduction, certain applications have reached parity with alternative generation technologies already.  For remote installations and isolated grids, solar is already the low-cost option.  As prices continue their decline, more and more applications will become attractive, with or without subsidy.

[1]  http://www.mckinsey.com/client_service/sustainability/latest_thinking/~/media/5E847C563A734F148B5F3A6EFBD46E39.ashx

What’s going on with First Solar (and cadmium telluride solar cells)?

Above: Year-to-date price history of several large solar cell manufacturers.
FSLR = First Solar (American)
SPWR = SunPower (American)
STP = Suntech Power (Chinese)
YGE = Yingli Green Energy Holdings (Chinese)

Followers and investors in one of the world’s largest solar panel producers have experienced a continuous stream of bad news since February. First Solar, a global leading producer of thin-film solar cells, has lost nearly half of its market capitalization since the beginning of 2012 and seems to be plumbing new all-time lows every few days [1]. First Solar is not without company in its suffering: its biggest American rival, SunPower Corp, has performed under the S&P 500 for the year as well (though not nearly as badly), and the established solar sector as a whole took a particularly bad tumble in mid-2011 and hasn’t yet recovered [1].

Much of this is likely due to changing market conditions and foreign competition. Over the past few months, much discussion has taken place regarding the Chinese government’s role in the selling of solar cells to Western markets, providing subsidies to Chinese manufacturers selling their products abroad in an attempt to undercut Western manufacturers and force them out of business. In late March, the US Commerce Department announced that they had found evidence that the Chinese government had indeed provided impermissible export subsidies to its local manufacturers, and placed small tariffs on solar panels from several Chinese manufacturers in response [2]. There is the possibility for even more punitive tariffs should the Commerce Department decide that Beijing is engaged in dumping practices, which would involve the government heavily subsidizing producers to the degree that they would be able to sell their panels abroad below cost [2].

But First Solar seems to have special problems, beyond the market conditions that would be affecting its competitors as well. Unfortunately, most of the company’s unique problems likely stem from its technology. First Solar is the leading producer of thin-film solar panels using cadmium telluride (CdTe) as its semiconductor material, and  produces the most efficient CdTe panels available [3]. CdTe panels, while having less sunlight-to-electricity conversion efficiency than some other materials like crystalline silicon, are particularly cheap to manufacture, with First Solar’s solar panels being the first to fall below a dollar per watt [4]. This cost advantge has been a boon to First Solar during its life, but some troubling news arose out of its 2011 10-K filing and annual earnings report. In the company’s earnings conference call, its then-CEO noted that it had used more money than originally predicted in fulfilling product warranties in 2011 and had alloted additional money to its warranty reserve [5].

The 10-K filing also noted that the company believed its higher rates of product are failure can be traced to a potentially increased failure rate of its cells in hot climates. It reached this conclusion “based on technical literature, data that we have developed internally including through accelerated-life testing, our analysis of modules returned under warranty, and our analysis of performance data from systems that we monitor under O&M agreements” [6]. It should be noted that, given the short short life span of thin-film technology and First Solar’s dominance of the market, this is really the first evidence or investigation towards the potential problems of cadmium telluride solar cells in hot climates. If First Solar’s suspicions are correct, we may be finding out for the first time that CdTe has a shorter lifespan in hot, sunny weather (where solar would be most appealing anyway).

This could be some pretty terrible news for First Solar, since its business strategy now focuses entirely on building utility-scale solar installations. During First Solar’s rapid growth in the second half of the 2000s, much of its sales and revenue came from its operations in Germany, where the national government heavily incentivized solar power development through the use of a generous feed-in tariff (a type of production subsidy). In 2010, amid many other austerity measures, the German government slashed this subsidy over the protest of domestic and foreign solar cell producers [7]. First Solar took this as cause to focus on building utility-scale projects in hot climates like the American southwest [8], and recently ceased all German manufacturing operations [9]. It was only after expanding out of temperate climates that First Solar found out about their potential problems in hot climates. This potential shortfall in meeting the company’s best market opportunity has gotten many investors spooked and concern about its viability [10].

Will this spell the end for the company? At this point, it doesn’t look like it. True to its goals in orienting towards utility-scale solar, First Solar has been able to sell projects in Arizona and California to plant operators like NRG Energy and Berkshire Hathaway’s MidAmerican Energy [11,12]. It would seem that these investors, at least, are not as concerned about the technology as the stock market seems to be.

References:
[1]: http://www.google.com/finance?q=fslr
[2]: http://www.nytimes.com/2012/03/21/business/energy-environment/us-to-place-tariffs-on-chinese-solar-panels.html
[3]: http://www.businesswire.com/news/home/20110726005689/en/Solar-Sets-World-Record-CdTe-Solar-PV
[4]: http://www.popularmechanics.com/science/energy/solar-wind/4306443
[5]: http://seekingalpha.com/article/399251-first-solar-s-ceo-discusses-q4-2011-results-earnings-call-transcript
[6]: http://www.sec.gov/Archives/edgar/data/1274494/000127449412000015/fslrdec1110k.htm
[7]: http://www.nytimes.com/gwire/2010/03/31/31greenwire-slashed-subsidies-send-shivers-through-europea-32255.html
[8]: http://online.wsj.com/article/SB10001424052970203518404577097540383138700.html
[9]: http://www.nytimes.com/2012/04/18/business/energy-environment/first-solar-to-cut-2000-jobs-and-close-a-german-factory.html
[10]: http://blogs.marketwatch.com/thetell/2012/03/12/first-solar-slides-again-on-price-target-cut-warranty-woes/
[11]: http://finance.yahoo.com/news/nrg-energy-midamerican-solar-first-201300851.html
[12]: http://www.bizjournals.com/phoenix/news/2012/05/04/midamerican-first-solar-start-work-on.html

Solar Panels: A True Carbon-Free Source of Energy?

“Today I challenge our nation to commit to producing 100 percent of our electricity from renewable energy and truly clean carbon-free sources within 10 years.”

-Al Gore, 2008

Our political leaders have a huge influence in how our population views technologies.  The former statement, while laudable, is distilled to the point of necessitating further analysis.  While the goal of ubiquitous carbon-free energy sources is certainly worth pursuing, it is vital that we do not discount the carbon footprint entailed in the adoption of those sources.

Let’s just take a look at solar photovoltaic (PV) systems. According to [1] and [2], the energy required to make a solar panel (by Siemens-like processes in 2007) was 4354 MJ/m2, which equates to 1210 kWh/m2 of panel produced. If this panel produces about 168 kWh/m2 in a year, then the estimated energy payback time (EPBT*) is about 2.2 years. This is great news.  However, if you then consider the carbon footprint of creating this solar panel and divide it over the panel’s lifetime (~30 years), the aggregate carbon emissions amount to 32 g/kWh produced. Fortunately, given improvements in technology, this value was expected to drop to 24 g/kWh by the end of 2011. So even though solar panels do not release CO2 during their normal operation (because they don’t need fuel to operate), the manufacture of solar panels does have a nontrivial carbon footprint. The upside of the story is that this footprint is still dwarfed by those of coal, oil, and natural gas (see table III below).

Source: [2]

So far, I’ve spoken only of the carbon emissions from the manufacture of PV arrays.  This is only one side of the CO2 payback time equation.  Another vital consideration is the carbon that is displaced by using solar energy in lieu of dirtier energy sources from the existing energy infrastructure — namely, coal and natural gas.  To quantify this carbon offset, one must consider both the energy source that would have been used were it not for the solar panel, as well as the amount of power being displaced by the solar panel.  Furthermore, the amount of power provided by a panel is a function of both its efficiency (largely driven by technology) as well as the solar panel’s environment. For example, according to [3], it would take twice as much time for a panel in the UK than in California to offset the energy used for its production. This is due to California’s favorable sunshine conditions of about 1,700kWh/m² per year, compared to the UK’s less favorable 700-900 KWh/m2 of solar energy per year.

So, in the end, solar power is a lot cheaper in terms of CO2 emissions and this is why I support their adoption. But it is at times appropriate to recall the famous quip from science fiction author Robert Heinlein: “there ain’t no such thing as a free lunch.”

*“EPBT is defined as the number of years a PV system must operate before it generates sufficient energy to equal the amount it consumed in manufacturing” [1]

References:

[1] P. Zhai and E.D. Williams, “Dynamic Hybrid Life Cycle Assessment of Energy and Carbon of Multicrystalline Silicon Photovoltaic Systems,” accepted for publication by Environmental Science & Technology (Sept.3, 2010).
[2] Y. Jiao, A. Salce, W. Ben, F. Jiang, X. Ji, E. Morey, and D. Lynch, “Siemens and Siemens-like Processes for Producing Photovoltaics: Energy Payback Time and Lifetime Carbon Emissions” JOM, 63 (1) (2011), pp. 28–31. Can be accessed here: http://www.springerlink.com/content/93h4wh6718251270/fulltext.pdf
[3] http://info.cat.org.uk/questions/pv/what-energy-and-carbon-payback-time-pv-panels-uk

Will PV cells take over the world?

Solar power is the poster child of the green energy movement. And why wouldn’t it be? Fuel that is entirely free, will be around for billions of years no matter what we as humans do, and doesn’t pump out nasty pollutants when used. Also, as a bonus, there is more solar power available than the world could conceivably use, roughly 89 petawatts of power [1], that’s 89,000,000,000 megawatts.

However, harnessing that power proves to be much more difficult than burning wood for a fire. The most common method used to convert solar radiation to useful energy is the photovoltaic effect, which converts photons from the sun directly to electricity and is utilized by photovoltaic, PV, cells. These cells in general do a fairly poor job of collecting the sun’s energy. Typically efficiencies are of the order 20%. In the laboratory, ie highly controlled conditions, PV cells have reached efficiencies of over 40% [2]. While the public may see these efficiencies in the future, they are not currently realistic.

What is realistic however, is a drop in price of PV cell technology. Last year, Ramaz Naam blogged for Scientific American about a possible Moore’s Law effect for solar PV cells [1]. Moore’s law originally applies to the doubling of computing power every 18 months, a trend followed by the computer industry for decades. It appears that solar power follows a similar curve, with dropping prices following a logarithmic curve from the 1980’s through 2010. Via Naam’s prediction, PV cells would reach $1/W in 2023, and could become cost effective, including installation costs, in 2020 [1].

http://blogs.scientificamerican.com/guest-blog/2011/03/16/smaller-cheaper-faster-does-moores-law-apply-to-solar-cells/

It seems though that solar power will beat Moore’s Law. Today, 2012, PV cell production costs are already approximately $1/W [3]. That’s 11 years sooner than Naam’s prediction, made only 1 year ago. In addition to dropping to $1/W, improvements in technology and production methods could lead to costs dropping to 50¢/W in the next 10 years. This would put solar power much ahead of the curve, and into the cost effective region for power generation, poised for rapid entry into the energy market.

It is very difficult to predict when a technology is on the edge of explosion due to innovation, and so a year ago it would have been exceedingly difficult to guess that solar power would go through a revolutionary shift in production techniques, enabling PV cells to be produced at greatly reduced prices. However, it seems as if PV technologies have experienced a massive innovation spike with such ideas as new ways to manufacture silicon with less waste, improved stability in silicon wafers that allow for less of the material to be used, and new designs for solar cells themselves [3]. These technologies are emergent, and will be improved upon as kinks are worked out. However, these advances represent a boom for solar power, and it will continue to ride that wave for many years to come as technologies are perfected and production grows.

Will solar power be part of the future? Most definitely. The amount of grid-connected PV installations grew 39% in just the 3rd quarter of 2011 with over 1 GW installed in the first 3 quarters of 2011 [4]. This growth will continue, especially with recent price drops for PV cells. Will solar power take over the energy sector, and the world? Maybe. There are still many hurdles for solar power to face, an intermittent source being the most serious. But the hurdle keeping away the most investors and customers has been lowered, reducing one of the barriers to clean, cheap, accessible energy for all.

Here’s to world domination solar power.

References:
[1] http://blogs.scientificamerican.com/guest-blog/2011/03/16/smaller-cheaper-faster-does-moores-law-apply-to-solar-cells/
[2] http://www.nrel.gov/ncpv/images/efficiency_chart.jpg
[3] http://www.technologyreview.com/energy/39771/page1/
[4] http://www.seia.org/cs/news_detail?pressrelease.id=1793

What is Masdar City?

I was able to volunteer at the Cleantech Forum 2010 in late February. There I became familiar with Masdar, the lead sponsor. Masdar is located in the heart of the global oil and gas industry, Abu Dhabi, but it’s all about renewable energy and sustainable technology. In short, their mission is to turn Abu Dhabi in to an international hub for renewable energy and support the development, commercialization and adoption of sustainable technologies. Their four integrated business units (Masdar Institute, Masdar Carbon, Masdar Power and Masdar City) are all cutting edge, but I’d like to focus on what they call the “physical embodiment of Masdar,” Masdar City.

The thought is to create a place for innovators and entrepreneurs to test energy science, city design, sustainable development and environmental architecture. The focus is not only on test and design, but also on making an alluring place to live and work. If your creating the city of the future and money is not an object(budgeted at $22 billion), why not reach for the sky? They have!

Masdar City will be powered by 100% renewables, it will be zero waste, zero carbon and it will have a sustainable water system. Transportation, materials, foods…all sustainable. They are going all out and the level of detail is amazing. From the orientation and width of the streets to the wind cones (shown in the Masdar Headquarters photo above) that naturally ventilate interior spaces to the retractable shades (shown below) covering City Plaza, nothing was overlooked.

Transportation is beneath the city, leaving the ground level open for pedestrians. The transportation system includes a light rail and a Personal Rapid Transport (PRT) system that a transports up to 4 adults to any PRT station at the touch of a button.

The Masdar Institute of Science and Technology(MIST), developed in cooperation with MIT will be at the heart of the R&D in Masdar City. It will eventually be home to 600 master’s and PhD students, with over 100 faculty members. MasDar City with also be the home of the International Renewable Energy Agency (IRENA) headquarters and host operations for companies like GE and BASF.

They are currently in Phase One of seven, which focuses on MIST. This means that first residents will be students testing new technologies, while being test subjects themselves. I would encourage you to learn more about Masdar City.

Source: http://www.masdarcity.ae/en/index.aspx

Solar must abide to TNSTAAFL

Using solar radiation for energy / electricity generation is certainly a great idea.  In terms of solving current CO2 production (if current concerns prove true), eliminating environmentally devastating coal mining operations and a dependence upon a depleting supply of raw crude oil,  it’s almost one of those stupid simple solutions that somehow we’ve neglected for hundreds of years, even though it was there, shining on us each day.   A strong case to support using direct solar energy (versus, say, fossil fuels) can be made quickly and easily, and might go something like this:

Efficiency of solar panels or solar trough / Rankin cycle technology for electrical generation (electrical generation): ~15%

Efficiency of fossil fuel electrical generation: (E = E_ecosys * E_organic matter to fossil fuel * E_mining and processing * E_burning and electrical generation)

Since this number is hard to calculate, lets simplify it to the favor of fossil fuel: E = E_ecosys * E_burning and electrical generation, taking E_ecosys as 2% and E_burn and electrical generation = 60% we find:

E_fossil fuel electrical generation : <<1.2%

So, use the sun’s energy with 15% eff, or 1.2% eff?  The choice seems obvious.  Best of all, using the direct method is FREE!  You don’t have to pay to mine, process, transport and burn the fossil fuel, you just have to collect solar radiation!  But wait, everyone knows you are not supposed to used the “F” word, because the “F” word violates one of the few time tested truths of humanity “there is no such thing as a free lunch”.  But what does using the sun cost, and why do some (Ken Zweibel, James Mason and Vasilis Fthenakis) suppose that the US could solely rely on solar electrical generation by as early (or late) as year 2100?

The cost of solar is land, because the issue at hand is energy density.   Though expectantly much less environmentally damaging than say, coal mining, solar harvesting requires an unheard of amount of land for el. gen.  Coal and oil mining undoubtedly occupy many thousands of square miles in the U.S. and the world over, but likely less than an equivalent area capable of producing the same energy content via direct solar el. gen.  This is a bold statement, solar would use more land than coal and oil mining?  But there is so MUCH solar energy, how could this be?!  4500 quadrillion BTU’s (4500,000,000,000,000,000) of solar radiation is dumped down on just the southwestern United States every year (Zweibel et. al.)!  Or almost 45x MORE energy than the U.S. uses each year!  So the answer is simple, just cover 1/45th of the southwest United States with solar technology like PV cells and trough / Rankin systems! And voilà, the world’s (or at least the U.S.’s) problems are solved- besides constructing a nation wide grid and the pesky and relentless enormous necessity of land!  Complaints aside, how much land will be required for the U.S. to be direct solar dependent?  Using a current U.S. energy consumption of 100 quads per year, and a 15% solar to electricity conversion efficiency, and a 6.5 kWh/m^2 / day solar intensity in the southwest we need:

Energy use: 100E15 BTU / yr           =       2.93E13 kWh / yr         =        8.027E10 kWh / day

and

Southwestern solar energy available: 6.5 kWh/m^2 / day

then

Land required is:

Energy Use / Energy Available per m^2          =        1.23E10 m^2                =               ~5000 sq. miles.

However, this number assumes 100% efficiency, so accounting for eff.:  5000sq. mi. / .15 eff      =  33,300 sq. mi.

Therefore, at a minimum, we would need something on the order of 33,000 square miles, which is on the order of magnitude of the size of a large state, every square inch of an entire state!  Surprisingly, the proponents of the “Solar Grand Plan”, by Zweibel et. al., determine through presumably more realistic calculations that an overwhelming 165,000 square miles is actually required to support the U.S.’s energy needs.  Now like I said at the beginning, solar is very attractive for many reasons, but can we expect it to be feasible to cover 165,000 square miles? That is this big, by the way (orange):

and would be even larger if you wanted the ground to receive sunlight so that plants could grow, or you wanted a city every so often within this massive area for civilization (which the power is for, remember), or you wanted any open space (like a park or forest) to get away from the dense arrays of solar collectors or panels.  At any rate, it just intuitively feels infeasible to cover such a vast expanse of land with equipment for solar power electricity generation. Don’t get my wrong, I support the use of solar, but I am unsure if it is feasible for the United States to rely 100% on solar energy power production due to the shear square miles required.

Lastly, the cost of building something of this magnitude is said to be in the $400B range, and would require national policy, not unlike the American Recovery and Reinvestment Act, but maybe more direct in assisting construction.  Alternatively,  a $.05/kWh  tax could pay for the construction says Zweibel et. al., which seems reasonable- and also leading to my conclusion that it’s not the cost of building solar facilities, but the cost of land usage that will prevent the “free” fuel from succeeding at supplying 100% of the U.S.’s energy needs.

Extra-Planetary Solar Arrays

“The dots to which our energy beams are directed…are cold and hard and human beings like myself live upon their surfaces — many billions of them. Our beams feed these worlds energy drawn from one of those huge incandescent globes that happens to be near us. We call that globe the Sun and it is on the other side of the station where you can’t see it.”

Speaking to his incredulous robot, the protagonist in the Isaac Asimov story “Reason” explains the basic functioning of Solar Station #5, a space-based solar power station in geosynchronous orbit with the Earth. First described by Asimov in 1941, space-based solar power (SBSP) may have moved from the realm of science fiction to reality, receiving interest from government and industry as an emissions-free, renewable energy source with no issues of intermittency or battery storage.

SBSP relies on solar power collection by panels attached to satellites in orbit, from which the energy is wirelessly beamed to the Earth’s surface. Since these satellites are stationed outside the atmosphere, virtually uninterrupted collection is possible of a light much more intense than that absorbed on Earth. In the most likely configuration, the host satellite would convert photons into electricity, powering a microwave emitter focused on a collector on the Earth’s surface.

Source: NASA

While extra-planetary solar arrays and wireless energy transmission have been investigated on an experimental scale, several recent high-profile commitments to SBSP may signal its growing feasibility. In April of 2009, the utility Pacific Gas & Electric contracted with an SBSP provider to buy 200 MW of solar power by 2016. If completed, this project would be the first application of the technology. Last year Japan announced a plan to launch a solar power satellite by 2030, which would transmit power via laser beam. Additionally, in 2007 the US National Security Space Office released a report proclaiming their intention to implement SBSP, referring to it “as a potential grand opportunity to address not only energy security, but environmental, economic, intellectual, and space security as well.”

Yet since wireless energy transmission from space has never actually been implemented, its viability by 2016 is questionable, hinging on technology constraints and the high cost of rocket launch. High-intensity transmission and terrestrial collection would have to be perfected, and concerns remain about environmental disturbance and safety issues created during transmission, as well as the effects of excessive heat on the solar cells.

In the prevailing theory, large disassembled solar panel arrays would be launched by heavy-lift rocket to low earth orbit, where they would then be assembled and brought to geostationary orbit by smaller rockets. Even assuming a solar panel mass of 1kg/kW, the minimum cost for a heavy-lift rocket is $11,538/kg, bring the total cost for a 2GW power station upwards of $11.5 billion. Another unlikely option suggested by NASA is to establish a construction site on the moon, where less gravity means cheaper rocket launches (yet initial investment in lunar infrastructure would reached untold billions).

Although the near constant stream of high-energy photons available outside the atmosphere is a tantalizing source of energy, the technological impediments and astronomical costs make implementation unlikely, considering the massive risk taken on by any investor. While government and private sector research and funding continues for the technology, SBSP may remain a well-intentioned fantasy.