Tag Archives: Solar

Solar Aviation: Around the World in 80 Days by 2015

A recent article from Forbes introduced me to a new technology I honestly would not have expected to exist: manned airplanes powered by solar energy. [1] Solar Impulse – the name of the Swiss company and the actual plane– offers an addition to a field that has been steadily developing since the 1970s. [2] The plane contains approximately 12,000 solar cells and four lithium-polymer batteries. These solar cells cover the 208 foot wingspan and give the craft an feather-like appearance. [1] After reading the headline and looking at the photo below, I found myself thinking of Icarus, the overconfident boy in Greek mythos who flew too close the sun. (A nerdy confession I know, but hopefully my ninth grade English teacher would be proud.) The story is one of hubris and failed ambition, and I could not help but think it applicable here. Interesting and innovative though they may be, are such advances in solar aviation really helping us combat the energy crisis?

The first solar-powered flight took place in California on November 4, 1974. “Sunrise I” was a tiny unmanned craft that weighed practically nothing and flew for approximately 20 minutes. A few years later, the first piloted solar aircraft (“Solar One”) used nickel-cadmium batteries with some success. [2] Progress in the field developed through the decades, with crafts such as the “Gossamer Penguin”—first to fly purely on solar energy, the “Sunseeker”—now the only solar aircraft in continuous operation, “Helios”—which reached nearly 30,000 feet in 2001, and Alan Cocconi’s craft—first to fly through an entire night, all contributing their fair share in honing solar aviation technology. [2] [3] But the Solar Impulse project is seeking to make the achievements in solar aviation less of a novelty and more of a practical solution to energy concerns. The company has aspirations to be the first to circumnavigate the globe with a larger aircraft in 2015. [4] The current “Solar Impulse” uses electricity produced from solar cells that can generate up to 45 kW of power. There are four, 10-horsepower electric engines on board that allow the plane to average about 40 miles per hour. [1]

That’s not very fast. In fact, numerous precautions are taken into account in order to avoid inflight complications, such as limiting weight (“Solar Impulse” is 3,500 pounds) and taking off early in the morning then landing at night. [1] An engineer and pilot associated with the project stated that the commercial applicability of solar aircrafts was still four decades away. And yet, the Solar Impulse project has demonstrated that solar energy can be a “stand-alone fuel”. [4] These early stages in developing a technology are admittedly slow. At this moment, solar aviation may not be immediately applicable to our energy problems. But commercial airlines are burning through fossil fuels and the innovation spurred by companies like Solar Impulse may someday be a saving grace for transportation. This is a long-term investment that may prove to be more of a gamble, but I’d rather take that risk now even if at the end of the day we get a little too close to the sun, our wax melts, and the whole project crashes and burns…metaphorically, of course.


[1] http://www.forbes.com/sites/uciliawang/2013/03/28/get-ready-for-a-solar-power-planes-maiden-flight-across-the-u-s/?ss=business%3Aenergy

[2] http://ecoble.com/2009/02/16/sun-power-jet-fuel-for-the-21st-century/

[3] http://www.solarimpulse.com/en/airplane/solar-aviation/

[4] http://gigaom.com/2013/01/30/coming-to-america-a-swiss-solar-powered-plane/


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Elon Musk’s Guide to the Galaxy

Over the past month, I’ve had the distinct privilege and opportunity to attend two of Elon Musk’s keynote presentations where he discussed his vision for a sustainable energy future, electric vehicle technology, and humanity’s multi-planetary quest.  As a way of background, Elon Musk is considered to be a modern day visionary, inventor, and innovator, and he is often compared to legendary inventors such as Nikola Tesla, Thomas Edison, Richard Branson, and Steve Jobs.  Elon Musk founded and runs companies such as PayPal, Tesla Motors, SpaceX, and SolarCity [1].


Elon Musk and DOE Secretary Steven Chu speaking at 2013 ARPA-E Energy Innovation Summit, Washington, D.C. – 2.26.13

Photo: Michael Belfiore

The first keynote speech I attended was on February 26, 2013 in Washington, D.C. while attending the 2013 ARPA-E Energy Innovation Summit.  This particular conference brings together some of the brightest energy minds in the world to discuss energy policy, energy technology innovation, energy security, and funding opportunities and successes through the ARPA-E program [2].

Mr. Musk’s presentation focused primarily on the process he went through to secure a low-interest $465 million loan through the Department of Energy’s Advanced Technology Vehicle Manufacturing (ATVM) Program [3].  The ATVM program was authorized by President Bush in 2007 under the Energy Independence and Security Act and later appropriated in the Fall of 2008.  The ATVM was already authorized and funded before President Obama’s American Recovery and Reinvestment Act (ARRA) stimulus program was enacted in 2009.  The ATVM program was geared towards helping the private sector accelerate the advancement and production of alternative fuel technology vehicles such as hybrid electric vehicles (HEVs), plug-in hybrids electric vehicles (PHEVs), and full electric vehicles (EVs) in order to reduce America’s dependence on foreign oil.

Mr. Musk was joined by Secretary of Energy Steven Chu on stage for the keynote session.  It was interesting to learn that both General Motors and Chrysler were both ineligible to apply for the ATVM program since both companies were going through bankruptcy proceedings at that time.  The two largest loans that were approved under the ATVM program went to Ford ($5.9 billion) and Nissan ($1.6 billion) to accelerate the development of their advanced vehicle technology platforms.  As Secretary Chu pointed out during the session, the most attractive piece of Tesla Motors’ application for an ATVM loan was that the company is vertically integrated and all of Tesla’s vehicle components and systems are designed and built here in America.  According to Secretary Chu, Tesla designs and builds everything from their battery systems, electric drive trains, suspension systems, chassis, and even the test and evaluation equipment to ensure that the vehicle is performing optimally.

The major announcement that Mr. Musk revealed during the session is that the production and sales of Tesla’s new Model S electric sedan was going so well that Tesla will be repaying their ATVM loan within 5 years instead of 10 years, which is in half the time than what was stipulated under the ATVM program terms.  Mr. Musk ended the session by reminding the audience that the DOE’s efforts to fund and support advanced energy technology research and development have produced many major successes similar to Tesla.  He pointed out that these successes all too often go overlooked due to the failure and over politicization of Solyndra.


Tesla and SpaceX founder and CEO Elon Musk, speaking at SXSW 2013 – 3.9.13

(Credit: Daniel Terdiman/CNET)

The second and most recent keynote address I attended was during SXSW Interactive in Austin on March 9, 2013.  Mr. Musk touched on the challenges of running multiple companies at the same time and cautioned entrepreneurs to not make the same mistakes that he has made.  When Musk was asked what was the biggest mistake and lesson he’s learned so far about being an entrepreneur and innovator, he explained to the audience that he has learned the hard way that you can’t hire someone simply because they are the smartest person available to do the job.  Musk said that you have to hire someone who is capable of doing the job and who also has their heart in the right place and a personality that you can easily get along with.

Musk also discussed his SolarCity venture and how the company is providing cheap solar power to customers who previously could not afford it through a full service community solar-based business model.  He also went into detail on SpaceX’s recent successful test launch of their new vertical take-off and landing vehicle (VTVL) called the Grasshopper.  SpaceX is taking a private sector approach to space flight by focusing on fully recoverable rockets in an effort to minimize the cost of each launch and mission.  SpaceX recently completed a successful text launch and docking mission to the International Space Station (ISS).  NASA subsequently awarded SpaceX a 10-mission contract to deliver supplies to (ISS).  Musk believes that humanity will be a multi-planetary species in the very near future due to private sector innovation and efforts like SpaceX.  Musk concluded the keynote session by saying, “I’d like to die on Mars, just not on impact.” [4]


[1] http://elonmusk.com/

[2] http://www.arpae-summit.com/

[3] http://www.teslamotors.com/blog/clearing-air-our-doe-loan

[4] http://news.cnet.com/8301-14013_3-57573439/elon-musk-at-sxsw-id-like-to-die-on-mars-just-not-on-impact/

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Is the Future of CSP Dim?

Concentrated solar power (CSP) is an often overlooked method to generate electricity from the sun. As the name implies, CSP systems concentrate the sun’s energy, and do so with the use of reflective mirror surfaces. In commercial CSP plants, the concentrated sunlight is typically used to heat a working fluid which in turn generates steam to produce electricity via a steam turbine. Although commercial CSP plants have existed since the 1980s, a number of factors have hindered the technology’s penetration into the energy market. What are the factors holding this technology back? And (perhaps more importantly) is there any hope for the technology to grow in to a competitive source of electricity?

In recent times, photovoltaic (PV) prices have dropped dramatically, leading to a strong interest in installing utility-scale PV. This has also had the secondary effect of reducing the investment in CSP, since it is currently a more expensive method to generate electricity from the sun. Because of cost, investors have opted for PV over CSP – so much so that many planned CSP plants are instead being converted to utility-scale PV plants. Environmental factors have also had an effect. Last year, BrightSource Energy’s planned 500-megawatt CSP plant encountered an obstacle after surveyors discovered fossil deposits on the planned building site. Further concerns on the site’s impact on wildlife, as well as the cost of the plant forced BrightSource to put the project on hold.

However, CSP does have marked advantages over other forms of renewable energy. Of particular interest are the methods with which CSP can overcome intermittency problems. Power plants which combine CSP and traditional primary sources of energy can provide electricity day and night. Integrated thermal storage seeks to overcome this problem as well – the working fluid which drives the CSP plants can be stored in tanks and then utilized at a later time to generate electricity at night or during periods of low sunlight. This provides a greater flexibility to the grid than PV and wind typically provide. Recent studies back up this claim, showing that thermal storage adds a market value of up to $14/MWh, and a capacity value of up to $30.50/MWh.

Domestically, companies such as SolarReserve has taken advantage of thermal storage, and have projects underway which will prove the technology’s viability. Furthermore, the largest solar thermal energy generating facility in the world operates on both solar and natural gas and powers over 200,000 homes according to NextEra Energy Resources, the company that owns the facility. 

In total, over 1.4 GW of CSP plants were under construction in the US last year. Once operational, these projects will help to demonstrate the feasibility of CSP in the US. This information, coupled with the success of overseas companies (see Abengoa) and projects (such as in Abu Dhabi, Spain, etc.) will ultimately show the viability of CSP in the coming years. Therefore, although there is definitely hope for the technology to grow, its success will ultimately rely on the ability to drive prices down through methods such as thermal storage. Only then, it seems, will investors be more willing to add a greater share of CSP into the renewable energy sector.

(additional references linked in article)


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Solar Plane Soars Above Expectations

In early April, a Swiss research team finally test flew their solar plane prototype. The light craft has a wingspan of a Boeing 747 (approximately 65 meters[2]) and over 12000 solar cells. Its average flight speed is only 45 miles an hour, but that is not stopping the inventors from dreaming big. Their plan for 2010 is to circumnavigate the globe. And all without using a drop of fuel to power the plane [3].

Here, the plane begins to rise with the Alps looking on [3].

This little story shows that, perhaps, solar power has a future in aerospace applications. While current solar panels are not powerful or efficient enough to be a main method of propulsion, perhaps they could be used in hybrid applications. This would be similar to the first generation of hybrid vehicles, where the internal combustion engine was the primary energy source and the electric motor was secondary energy source.

Taking off is the most fuel intensive portion of flight. In fact, if the plane reaches a high enough speed, jet engines can shut off their compressors in their engines, allowing only the combustion reaction to propel them and maintain speed.  A lot of this is due to the lower drag at high altitudes due to lower air density. Is this a niche in which a solar powered plane could significantly lower fuel costs?

Unfortunately, the prognosis is not overly optimistic. The current Toyota Prius Permanent magnet AC synchronous motor is only 80hp[4], while each Boeing-747 jet engine is approximately 116000hp[2]. The weight and passenger size of these vehicles are absolutely massive, but scaling the Boeing engine power down to a 2-4 seat plane’s power doesn’t help much: 976hp to 80hp. A lot of this power isn’t necessary for steady flight, but the difference in magnitude is remarkable. It would be interesting to see if there are smaller, 2-4 seat planes for which the motor power is more comparable.

The other reason hybrid planes currently aren’t on the horizon is the two main restrictions of flight: weight and cross sectional area. Solar panels, electric motors, and large batteries would have to be added to make the hybrid plane function. For the scale of a plane, it’s hard to estimate what weight these would add, but it would not be insignificant. This, however, would be at least partially offset by requiring less fuel in the tanks. Finally, though, you get into area concerns. The solar panel arrays would require large areas to function. While it wouldn’t directly increase drag much (since solar panels are installed on a plane perpendicular to the velocity of the aircraft), I doubt manufacturers are about to make their planes’ bodies increase in size greatly so they can install more solar panels. Thanks to drag and weight concerns, there’s only so much room on a plane.

There are many technical and practical difficulties with making a hybrid plane (such as inclement weather suddenly becoming much more of a problem).  On the bright side, though, there have always been technical and practical difficulties associated with aerospace vehicles. It comes with the territory. Hopefully, this is one area they can get hammered out.


2. http://www.boeing.com/commercial/747family/747-8_fact_sheet.html

3. http://intransit.blogs.nytimes.com/2010/04/07/solar-plane-takes-maiden-flight-slowly/

4. http://www.toyota.com/prius-hybrid/specs.html


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Concentrated Solar

The sun is the most abundant form of energy. It is ubiquitous, inexhaustible, and emits no greenhouse gases. Within five minutes, the sun provides enough energy to the United States in order to meet the nation’s demand for an entire year.

There are two main ways to harvest energy from the sun: concentrated solar and photovoltaic panels. Although photovoltaic panels are desirable for their ability to be placed on rooftops where the power is needed, concentrated solar has many advantages. The technology is more efficient and cost effective than photovoltaic panels. Concentrated solar plants can operate with little water because they can be air-cooled. It uses mostly commodity materials: steel, concrete, and glass. This technology could be used to desalinate brackish groundwater or seawater. [1]

One obvious restriction of concentrated solar is the large amount of land required and electric transmission lines, however, there are many locations suitable for this technology and the transmission lines could be shared with wind farms. Nevada Solar One is an example of a concentrated solar power technology that is currently being implemented.

Nevada Solar One is one of the largest concentrated solar power plant in the world that came on line in 2007, costing close to $250 million. It encompasses 250 square acres and contains more than 180,000 parabolically shaped mirrors that follow the sun. These mirrors concentrate the sunlight on long steel pipes filled with oil. The oil is heated up to 750 degrees Fahrenheit and is then poured into giant radiators that use the heat to boil water into steam. Turbines are driven by the steam and push as much as 64 megawatts onto the grid. That is enough electricity for 14,000 households. At Nevada Solar One, twenty-one percent of the sun’s rays can be converted to electricity on a clear summer day. [2]

[1] Romm, Joseph. “The Technology that will Save Humanity.” Salon April 2008. http://www.salon.com/news/feature/2008/04/14/solar_electric_thermal

[2] Johnson, George. ” Plugging Into the Sun.” National Geographic September 2009. http://ngm.nationalgeographic.com/2009/09/solar/johnson-text/1


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