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Overview: The Solar Fuel

We all know that sunlight has multiple functions to almost everything in this world. One of its functions is to serve as one of our energy sources. But the big issue here is how can we store the energy produced by the sun and most importantly how can we provide continuous energy supply from solar energy considering that sunlight is not present all the time? That’s why the solar industry did not stop thinking and doing some solutions to overcome this certain energy problem. They created the Photovoltaic (PV) panels but this is not yet the best solution for this since it’s not capable of storing energy. And that’s how they came up with research about developing technologies that can use sunlight to drive chemical reactions to make fuels and store solar energy in the form of chemical bonds. Thus, converting solar energy into solar fuels.

Fossil fuel is one of the primary energy sources of the world until today. However, it is not a good source of energy for it can cause carbon dioxide (CO2) emissions which is harmful to both human health and the environment. That’s why solar fuels are introduced, through the use of sunlight, water can be easily split to make hydrogen which is a good and clean renewable fuel. Aside from that, sunlight can also turn the carbon dioxide (CO2) turn into useful fuels. 

Innovative technologies and methods are implemented to convert solar energy into solar fuels, efficiently and effectively, so this CO2 emission issue can be resolved. Solar fuels are capable of reducing CO2 emissions by simply replacing fossil fuels that are being used in some industrial processes and other transportation. Additionally, solar fuels particularly hydrogen is considered as one of the alternative sources of energy to replace fossil fuels, aside from that it is also viewed as essential energy storage. 

Moreover, solar fuels can be produced in both direct and indirect processes. Through the direct process, solar energy is being harnessed from the sunlight to make fuel production without the aid of any energy conversion intervenor. On the other hand, in the indirect process, solar energy is first being converted to another form of energy such as electricity or biomass in order to produce fuel. This process is much easier to execute than the direct process but it is less efficient because the energy is wasted during the conversion. 

What is Solar Fuel?

A solar fuel is an artificial chemical fuel, which is produced via direct or indirect solar heat process through the photochemical, thermochemical, and electrochemical reactions. In simple words, solar fuel is the combination of sunlight, carbon dioxide and water which are being used to form a liquid fuel. Sunlight is used to produce chemical reactions to make fuels and to form chemical bonds. Unlike solar cells which only convert sunlight into electricity, solar fuels can also do the conversion and storing energy through its chemical bonds. These chemical bonds have an extremely high density of energy followed by the energy being stored by the atomic nucleus. 

With this given abundant use of solar fuels, extensive research has been implemented into two valuable forms, Hydrogen and carbon-based fuels as well as carbon monoxide and methane.

What is Solar Fuel Technology?

Solar fuel technology is a developmental system that has highly efficient and effective components to make fuel productions. This technology uses sunlight, water, carbon dioxide and nitrogen to produce solar fuels. Moreover, solar technology is similar to natural photosynthesis–where plants make biomass fuels through the sunlight. With this technology, it is possible to make fuel (hydrogen gas) from sunlight by water electrolysis process which is done simply pumping the electricity coming from the solar panels into water. Producing solar fuels through this process will need a solar panel and electrolyzer technology. Although, using these two technologies is quite expensive compared to producing hydrogen using a larger scale from natural gas. 

How is Solar Fuel produced?

Solar fuels are being produced through the use of the different basic natural phenomena of photosynthesis wherein sunlight is used to convert carbon dioxide and water into oxygen and sugars. Over the past half-century, scientists made it possible to produce solar fuels in the laboratory and developed three fundamental approaches to achieve the production of solar fuel. These are the artificial/synthetic photosynthesis natural photosynthesis, and thermochemical approach.

Natural Photosynthesis

Natural photosynthesis is the process wherein the sunlight is being harnessed and converted into energy to make chemical bonds from the organic molecules and building blocks of all living organisms, as well as from coal, oil and gas. Deriving the fuel directly from the photosynthesis done by the living things. 

Artificial Photosynthesis

Whereas, artificial photosynthesis uses a broad range of synthetic system where it ‘s mimicking the natural photosynthesis process. The sunlight is being harvested and the harnessed energy is used to convert water and carbon dioxide into fuels. 

Both natural photosynthesis and artificial photosynthesis process harnessed sunlight by light photons absorption through the antenna which is used to transport the chemical reactions. The energy in these protons is being used to split the charges into positive and negative ions and these charges will act as oxidizing equivalents to split the molecules of water into hydrogen and oxygen constituents, which will store as energy chemical bonds.  

Thermochemical Approach

A thermochemical approach uses light photons to split the molecules of water, directly and uses high energy rays of sunlight to heat substances at very high temperature in a closed environment to make steam or carbon dioxide reaction to produce hydrogen or carbon monoxide.  

Why Support Solar Fuels?

We all know that solar energy is one of the most powerful and abundant sources of energy here on Earth. However, the sun is not that reliable source of energy since it’s not available all the time. Therefore, the solar industry provided several ways to store energy coming from the sun so it can be used at any time of the day.

Solar energy can be harnessed and stored directly through the chemical bonds of a material, or ‘fuel’. These so-called chemical fuels, wherein energy from the sun is being stored are called solar fuels. 

The chemical bonds that can be found in fuels are the most solid way to store energy outside of an atomic nucleus. That’s why solar fuel is essential in our daily energy consumption. 

Aside from that, fuels made from the sunlight can provide a vast grid-scale of energy storage which is a good solution for solar power intermittency. It can also give enough liquid fuels needed to power heavy-duty vehicles, ships and aircraft. 

Types of Fuels

Scientists have made significant progress in generating two vital types of fuels. These are Hydrogen and Carbon-based fuels such as carbon monoxide or methane. 


Hydrogen is commonly used as a transport fuel and considered as an important feedstock for the energy industry. Hydrogen can be produced by electrolysis and water splitting using sunlight. In order to use sunlight in the whole process, a photoelectrochemical cell is needed, this has a photosensitized electrode that converts light into an electric current, which is being used for water splitting. The hydrogen production uses an indirect process since it produces electricity first and then the produced electricity is being used to form hydrogen.

Carbon-based Fuel

Carbon-based fuels such as methane or carbon monoxide can be produced by the used of sunlight, carbon dioxide and water.  These are commonly used for a wide range of industrial products like plastics, pharmaceuticals, fertilizers, and synthetic liquid fuels.

Solar Fuels Applications

One of the main applications of solar fuels is for the transport industry. Most of it uses either pure hydrogen or the combination of carbon monoxide and hydrogen. It is also suitable for the aviation industry as most aircraft used solar fuels. Another potential application is in the industrial feedstock, it is being used as one of the raw materials of machinery or processing plant. Additionally, most of the products that we are using on a daily basis like plastics, pharmaceuticals and fertilizers have this fuel. In fact, Hydrogen is commonly used as a raw material in some product manufacturing.

The Future of Solar Fuels

Among all the renewable resources, the newest one is solar fuel. By the use of solar fuel technology, it is now possible to produce enough eco-friendly fuel to power the larger portions of the world instead of relying on fossil fuels which can cause an imbalance ecosystem and global warming.

Since solar fuel is just a new implemented technology, researchers are still working a lot to develop effective methods and approaches to produce solar fuels. But with this fast-growing system, the production of solar fuel has a huge chance to boom in the solar industry, for the coming years. It can power the electrical grids in a much larger scale of communities in the future. The continuous research and development of its production can lead to major success in leaving fossil fuels for good. 

Reviews on Solar Fuels

Chemistry in a New Light: Solar Fuels

Stefan Bernhard, a Chemistry professor at Carnegie Mellon University, explains why we need solar fuels and how they actually work. 

Solar Fuels

In this YouTube content, the importance of Solar fuels is mentioned including how it works and being produced (process) and how human benefit to it.

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We just had a call with William Sims, CEO of Joule Biotechnologies.  A very personable, charismatic, yet down-to-earth guy.

Yet, the science behind his designer fuel is almost from anotherworld relative to the biofuel approaches in existence today.  In orderto understand what Joule is manifesting, a brief recap of a few otherprocesses is required:

First-generation biofuels transform food crops into either ethanol(fermentation) or biodiesel (transesterification).  Such biofuels nowdisplace more than 2% of global petroleum consumption and production isin the tens of billions of gallons per year range (see Ethanol and Looming Blend Wall). While first-generation biofuels have begun to make a dent in the oilmarkets, their capacity to scale much further beyond current levels isimpacted by the “food vs. fuel” debate, infrastructureincompatibilities, and questions about whether the carbon and energybalance of producing these biofuels is net positive. (See An Inconvenient Truth: Biofuels Have a Carbon Footprint.)

Second-generation cellulosic biofuels by and large do not competewith cropland (ideally) and food sources.  In utilizing the lignin toco-generate electricity, cellulosic biofuels have a better environmentfootprint relative to first generation fuels.  Some companies such asAmyris are also breeding genetically modified organisms to secretehydrocarbons, thereby cutting out some refining processes. There aresignificant questions surrounding the logistics of obtaining millionsof tons of biomass of different shapes and sizes as well as the costsof breaking down the biomass into fermentable sugar (see Denmark Makes A Stab for Biofuels Greatness). Second-generation biofuels are not commercial yet, however, the firstcommercial facility is expected to be running by late 2010. The totalamount delivered, however, will be small.

Third-generation algae is a qualitative leap from first- andsecond-generation processes.  Basically, certain strains of algae cangrow up to 50% of its body weight as a lipid that can be transformedinto a variety of “drop-in” hydrocarbons (jet fuel, diesel, gasoline,etc.).  Algae do not require freshwater or cropland and consume C02 asa feedstock.  The big problem with algae is that the numerous stepsrequired in growing, harvesting, drying, de-watering, extracting theoil, and transforming the oil into fuel costs somewhere between$8-$30/gal.  While costs are expected to come down precipitously incoming years due to the consolidation of these steps (see Biofuels 2010: Spotting the Next Wave), many experts in the field do not believe that we will see commercial-scale algae biofuels for another 8-10 years.

This brings us to Joule Biotechnologies and its competitors, who areattempting to utilize proprietary microorganisms that turn photons,water, and C02 directly into drop-in fuels.  ARPA-E gave $23.7 million to a couple of companies like BioCee in this space last year. ARPA-E calls it “direct solar fuel” because you don’t have to wait millions of years and employ tectonic forces to get fuel. But we prefer Biofuel 3.5.

Although Joule has remained relatively tight-lipped about thespecifics of its technology, its systems have a “solar converter” whichcan be thought of as solar walls (but not cells) that absorb photonswhile managing optical density so their proprietary bugs get all thephotons they need.

The company uses a “helioculture” process that amalgamates thephotons with captured waste C02 and brackish water to optimizephotosynthesis.  Yet, the modification of the organism is such thatrather than using the energy available from photosynthesis to grow, theorganisms direct the energy for production of fuel.

As such, the process generates more energy than it consumes and doesnot have any of the issues of growing, harvesting, and convertingbiomass into energy (because it does not use biomass), therebyradically reducing operational costs.

The company expects to produce diesel at $30/bbl at the nth plant of commercial scale.

Currently, it is building out its first pilot facility, which willcome online in 2010.  Joule will create a demonstration plant in 2011and hopes to break ground on a commercial facility in 2012.

The company is targeting 25,000 gallons of ethanol per acre per year and 15,000 gallons of diesel per acre per year.

Some in the industry are skeptical of Joule’s claims.

For example, renowned NASA scientist Dr. Aaron Baum writes on his blogthat these claims “should be a red flag for investors…  If thecritters can be kept alive indefinitely producing the product, then thelipid fraction is effectively 100%.  This still does not get you closeto their claims for any realistic biological photosynthetic mechanism.”

Not helping Joule’s case is the fact that a number of high-profileadvanced biofuel companies over-promised and under-delivered in recentyears (see 8,751,428 Gallons of Algae Per Acre!), further eradicating credibility within the nascent industry.

Yet, when I asked him about the formidable challenges that hiscompany faces, William Sims was quite humble. He admitted that whileJoule has shown incredible results in the lab, “it is true that we havenot shown that it works at a large scale.”

The company is funded by Flagship Ventures and has enough capital tobuild two pilot facilities this year (one pilot plant will producediesel, the other ethanol) and the demonstration plant in 2011.

It could be a game changer if it works. If it works.

Michael Kanellos contributed to this article.


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