Cella Energy Limited
About Cella Energy Limited
Cella Energy Limited has unique patented technology in safe, low-cost hydrogen storage materials. Cella is a spin-out company from the Rutherford Appleton Laboratory RAL at Harwell, Oxford, UK. RAL is a UK Government facility, and if in the US would be equivalent to Argonne National Labs. The lead investor in the Company is Space Florida, Space Florida is an Independent Special District of the State of Florida, created by Chapter 331, Part II, Florida Statutes, for the purposes of fostering the growth and development of a sustainable and world-leading space industry in Florida. Cella has a facility at RAL, and also a facility at the NASA Kennedy Space Centre in Florida.
Cella has connections with the leading oil companies around the world, and its investors also include Thomas Swan & Co. Ltd., a specialist UK chemical company established in 1926. Thomas Swan’s Advanced Materials Division is dedicated to the development of high specification materials for emerging technologies with particular focus on carbon nanomaterials and advanced coatings.
Work began on the technology in 2007 led by Professor Stephen Bennington and Dr Arthur Lovell at the 1,200 person STFC ISIS facility at the Rutherford Appleton Laboratory and at the London Centre for Nanotechnology at University College London (UCL). The work at UCL was led by EPSRC funded EngD student Zeynep Kurban and Professor Neal Skipper. In addition Professor Bill David from STFC and Dr Martin Owen Jones from Oxford University, have provided valuable insights into advanced complex hydride materials.
Cella Energy is a member of the UK Hydrogen and Fuel Cell Association UKHFCA .
Safe, low-pressure and ambient temperaturesCella Energy's technology is a way to nanostructure and encapsulate complex chemical hydride materials to improve their performance, in terms of temperature of operation, adsorption and desorption kinetics, and render them safe to handle in air. The final product is either a fine micro-fibrous polymer mat that resembles white tissue paper, or a fine polymer powder, micro-bead diameter ~ 0.5 - 5 μm, with the hydride material entrained in ~50 - 200nm pores within the polymer.
Although hydrogen is the most abundant element in the universe it does not occur naturally on our planet. Storing hydrogen up to now has required either high pressure storage cylinders at up to 700 times atmospheric pressure (700bar or 10,000psi) or super-cooled liquids at -253°C (-423°F). Neither is practical on a large scale as these hydrogen storage methods both require large amounts of energy to either pressurise or cool the hydrogen, and present significant safety risks.
Packaged in a regular shaped fuel tank or container
The Cella Energy hydrogen storage materials are stored at ambient temperatures and pressures, this means that the Cella Energy hydrogen storage materials can be packaged in a regular shaped fuel tank. They do not require the large heavy cylinders designed to withstand high pressures normally associated with hydrogen storage.
High hydrogen content – exceed DoE targets of 4.5%Cella's materials are already performing at 6wt% weight percentage of hydrogen, but Cella is now working with complex hydrides that store hydrogen at up to 20wt%. These exceed the revised 2009 Department of Energy targets to produce hydrogen storage materials that would compete with gasoline.
Low-costThe Cella Energy hydrogen storage materials can be manufactured in a large scale automated process called electrospinning or electrospraying. This low-cost process is used to produce the composite materials, and a combination of process parameters and the solution chemistry to control the nanostructure. The micro-bead format is particularly interesting as it has properties akin to a liquid fuel that could be used in vehicles just like gasoline, but without any carbon emissions.
Refuelling – safer than gasolineMost drivers are used to refuelling with liquid fuels such as gasoline or diesel. If hydrogen is used in compressed cylinders a new high pressure gas refilling infrastructure is required using high pressure hoses. By contrast Cella Energy's liquid fuels require no additional infrastructure, vehicles can be refilled just like today. In fact the materials are safer to handle than gasoline.
Fuel additivesIn a pure hydrogen vehicle there are zero carbon emissions, but it would also be possible to add Cella Energy's hydrogen storage materials to existing fuels. This would lower the emissions and enable a vehicle manufacturer to meet the new EU Euro 6 standards for emissions with minor vehicle modifications.
AircraftThe Cella Energy hydrogen storage materials could also be added to kerosene, JP-8 or jet-fuel to lower the emissions from aircraft. If used in this way there would be minimal modification of engine design.
More information about Cella Energy can be found in the recent TTP publication below.A new route to portable hydrogen storage
Isn’t hydrogen dangerous ?
When most people think about hydrogen they think of hydrogen as a gas, most notorious for exploding airships in the 1930’s. Hydrogen is the most energy dense material known, it powers our Sun and that is why NASA launches rockets using it. But hydrogen occupies a large volume, so in a vehicle to provide the same range as a typical gasoline tank, you would need a tank the size of a large trailer you would have to tow behind you.
To overcome this problem, hydrogen is pressurised or compressed into smaller tanks. To provide a similar size to a typical car gasoline tank, hydrogen has to pressurised to 700bar (700x atmospheric pressure) or 10,000 psi (pounds per square inch). This pressurisation requires a great deal of energy, and makes the tanks hazardous if ruptured in a collision. The tanks also have to be cylindrical in design, so there are no sharp edges that would not withstand these high pressures. This makes the tanks difficult to package into existing vehicle designs, because most conventional automotive fuel tanks are uniquely shaped to fit any available space in a vehicle.
To overcome the problem of high pressure tanks, automotive engineers have tried using both liquid hydrogen and metal hydrides. Liquid hydrogen is a frozen gas, for example water is a liquid at room temperature but turns into a gas or steam when boiled at 100°C (212°F) - at normal pressures. By contrast, hydrogen is a gas at room temperatures, but does not turn into a liquid until very cold -253°C (-423°F). To make the hydrogen this cold requires a great deal of energy and special insulated storage tanks. The tanks again have to specially designed and shaped, but even then it is impossible to prevent some boil-off. A driver leaving there car parked for any length of time, may find the hydrogen has all gone !
Metal hydrides are solids that absorb hydrogen and typically give out this hydrogen, or desorp it, when heated. The will operate are closer to ambient temperatures and pressures, but there disadvantages can be that they are heavy and air sensitive. Refilling the tanks can also take some time, several hours, because the metal hydrides do not absorb the hydrogen quickly.
In 2002, the DoE first published some targets to make hydrogen competitive to gasoline. One was that a hydrogen storage tank should store hydrogen at least at 6wt% or 6% hydrogen by weight. This target was revised to 4.5wt% in 2009, because this was the most that could be achieved by 700bar compressed hydrogen tanks. Super-cooled liquid hydrogen tanks can achieve about the same 4.5wt%, and metal hydrides are typically between 2wt% and 4wt%.
Why is Cella different ?
Cella uses complex hydrides. Complex hydrides such as Ammonia Borane can store hydrogen at up to 19.6wt%. There is no hydrogen gas involved, instead hydrogen is chemically absorbed into mineral salts. In fact hydrogen is the most abundant element in the universe, for example water that makes up two-thirds of our planet, is hydrogen and oxygen or H2O.
So instead of using oil, to make complex hydrides we use the type of raw materials that are used every day in the chemical processing industry to make materials such as food stuffs, soap powder, cleaning fluids, packaging and many other mass produced consumer goods. These chemicals are low-cost and safe, and are not constrained like rare earth minerals.
Complex hydrides release hydrogen when heated. However many of the complex hydrides are highly air sensitive, release hydrogen only at very high temperatures, can take a long time to release the hydrogen and can contain impurities that would be harmful to a fuel cell or as emissions to the atmosphere.
Cella takes the complex hydrides and encapsulates them using nano-structuring. This first makes the materials handleable in the open air. No vapours are given off, unlike gasoline. This process also dramatically improves the kinetics of the complex hydrides, meaning that the hydrogen is released at lower temperatures and much more rapidly. The nanostructuring also prevents much of the impurities from being released.
About how much does it cost to produce a gallon of gas?
Retail fuel or gasoline (petrol/diesel) prices are determined by the price of oil, the cost of distributing the fuel and by taxation. Prices vary as the price of oil varies on the commodities markets, for example Brent Crude at $100 a barrel, and as Government policies change fuel duty and tax rates. Taxation varies country to country, and often State to State.
In a 100% hydrogen vehicle, we are concerned about the cost of producing hydrogen not the price of a barrel of oil. The DoE long term price target for hydrogen is $1-$2 per Kilogramme kg. In energy terms, a kg of hydrogen is roughly equivalent to a gallon of gasoline. As Cella’s strategy is to fit in with the existing supply chain, we can assume that the distribution costs are the same, but taxation should be lower. In the UK tax & fuel duty represent 63% of the cost of fuel, in North America this is typically 25%. Lower-emission hydrogen fuels should attract lower tax and duty rates.
So if gasoline prices were $4 a gallon, then this could be made up of $2 for the gas, $1 for distribution costs and $1 for tax. Cella prices could be made up of $1 to $2 for the hydrogen, $1 for distribution and $0.50 for tax, meaning $2.50 to $3.50 a gallon equivalent in North America.
In the UK and Europe gasoline (petrol) is sold in litres. A price of £1.50 a litre would be made up of £0.36 for the fuel, £0.19 for the distribution costs, and £0.95 for tax. The equivalent Cella price would be about £1 to £1.20 a litre assuming lower fuel duty and taxation.
Note these prices are estimates for a 100% hydrogen vehicle not for the fuel additives/fuel component. In a hydrogen vehicle the cost of producing the hydride is not significant, because the material is recycled.
Are the nano materials hazardous?
Cella’s materials are not nano size, they are quite big by comparison – actually micron sized. Cella’s micro-beads are small, but in size terms, this is like comparing a grain of sand to a tennis ball. Cella uses nanostructuring techniques during the manufacturing process, but the materials themselves are not nano sized when produced. There are some health concerns about breathing in nano-particles in the air, but this does not apply to larger micro-beads.
In a typical gasoline engine, the gasoline is sprayed as a fine vapour through the injectors for combustion. This spray is made up of micron sized droplets of typically 1-5µm. For the fuel additives, Cella will create similar size micro-beads that will disperse into the gasoline or diesel uniformly as an emulsion.
In the pure hydrogen vehicles where the micro-beads are flowed from one tank to another and heated to release hydrogen, these micro-beads are likely to be larger, maybe a millimetre in size, and there shape will be engineered to maximise the packing density. This size would also prevent any aerosol or explosion risk.
How much would it cost to establish a large-scale production facility?
There are two stages to the proposed roll out of Cella’s hydrogen fuels.
The first stage involves adding the micro-beads to regular gasoline and diesel fuels to lower the emissions and improve the performance of conventional vehicles. The goal is to introduce this without any changes to refuelling infrastructure and without any changes to conventional vehicles. The manufacturing plant to make the micro-beads would be based close to an oil refinery or fuel distribution depot and the hydrogen micro-beads would be added to the fuel prior to delivery to the filling station.
The manufacturing process is similar to any large scale fully automated chemical process and would be orders of magnitude less expensive than a new oil refinery.
The second stage would involve the roll of pure-hydrogen fuels, where the delivery tankers take back-loads back to the refinery of spent micro-beads for recycling. The recycling process would require storage tanks that could make use of the large quantities of hydrogen available at the refineries and the waste heat. The anticipated investment here would be relatively modest in oil industry terms.
Will Cella establish its own brand of gas or filling stations?
Our strategy is work with the existing oil companies, not to establish our own retail outlets.
What would happen if the Cella fuel tank ruptures?
The fuel is much safer to handle than gasoline. If a tank ruptured a solution like milk mixed with water would escape. This would emit no harmful vapour. There is no high pressures or air sensitive material inside.
How is hydrogen produced?‘Green’ hydrogen can be produced using electrolysis or hydrolysis where water is split into hydrogen and oxygen. This process requires electricity. If the electricity is produced using say a wind turbine or a solar farm then zero carbon emissions result. The same could be said if off-peak or wasted base-load electricity is used.
‘Brown’ hydrogen is mostly produced by reforming natural gas or methane CH4. Natural gas reforming is performed on a large scale at most refineries because most of the world’s hydrogen is used during the oil refining process.
If the hydrogen is then pressurised so it can be stored in a high-pressure tanks, this pressurisation makes the energy balance very poor. Cella’s hydrogen storage materials makes this energy balance considerably better by avoiding the pressurisation step.
Cella Energy technology
Complex chemical hydrides now exist that store hydrogen in concentrations that are well above 10 wt%. For example, ammonia-borane is 19.6 wt% hydrogen, 12 wt% of which is released at temperatures below 150°C. However, these materials have slow desorption kinetics and can release other chemicals such as ammonia or borazine which could poison a fuel cell.Many are also difficult to handle in that they degrade rapidly in air. These issues can be solved using our nanotechnology.
Cella Energy has developed a method using a low-cost process called coaxial electrospinning or electrospraying. This traps a complex chemical hydride inside a nano-porous polymer, speeds up the kinetics of hydrogen desorption, reduces the temperature at which the desorption occurs and filters out many if not all of the damaging chemicals. It also protects the hydrides from oxygen and water, making it possible to handle it in air.
The coaxial electrospinning process that Cella uses is simple and industrially scalable, it can be used to create micron scale micro-fibres or micro-beads nano-porous polymers filled with the chemical hydride. Cella believes that this technology can produce an inexpensive, compound material that can be handled safely in air, operates at low pressures and temperatures and has sufficiently high hydrogen concentration and rapid desorption kinetics to be useful for transport applications.
Our current composite material uses ammonia borane NH3BH3 as the hydride and polystyrene as the polymer nano-scaffold. Ammonia borane in its normal state releases 12wt% of hydrogen at temperatures between 110°C and 150°C, but with very slow kinetics. In our materials the accessible hydrogen content is reduced to 6wt% but the temperature of operation is reduced so that it starts releasing hydrogen below 80°C and the kinetics are an order of magnitude faster. Although ideal for our proof-of-concept work and potentially useful for the initial demonstrator projects it is not currently a viable commercial material: it is expensive to make and cannot be easily re-hydrided or chemically recycled.
Cella is now working on other hydride materials, these have slightly lower hydrogen contents but it is possible to cycle them into the hydride phase many hundreds of times and we are encapsulating these in hydrogen permeable high-temperature polymers based on polyimide.
Use of the technologyThere are two ways to use these materials:
Pure hydrogen solution Zero carbon emissionsas a way of storing and delivering hydrogen safely for use in an internal combustion engine or a fuel cell
Fuel additive Lower carbon emissionsFor use as a fuel additive to reduce the carbon emissions from a hydrocarbon fuel such as gasoline, diesel, JP-8, jet-fuel or kerosene
Pure hydrogen solution, how it would work in a vehicleCella can manufacture the materials in the form of micron-sized beads. This makes it possible to move the beads like a fluid. This opens up a number of opportunities:
It is no longer necessary to try and rehydrogenate the material within the vehicle. For most hydrogen storage materials this releases megajoules of energy. If the refuelling is to be done in a few minutes, this requires cooling to remove several hundred kilowatts of power. To facilitate rehydrogenation in the 3-4 minutes that the DOE targets stipulate, the thermodynamics require high temperatures and pressures of around 100bar. This requires substantial engineering and as such we don't believe that on-car rehydrogenation is reasonable. With a fluidized hydride, it is possible to quickly fill or remove the material from the vehicle so that it can be recycled or rehydrided elsewhere.
It is possible to move the material within the vehicle making it possible to separate the storage from thermolysis. A schematic for the kind of idea that we have to achieve this is shown in figure 1. The beads are stored in a fuel tank, which does not need to contain high pressures or be heated and cooled, therefore it can be a simple lightweight plastic tank of complex shape similar to that used in current vehicles. The hydride beads are then pumped to a hot cell where waste heat from the engine exhaust is used to drive the hydrogen into a small buffer volume. The hydrogen buffer is maintained at a pressure suitable for the internal combustion engine ICE or fuel cell and which is sufficient in volume to be able to restart the vehicle. Once the hydride has been heated and the hydrogen driven off, the waste beads are stored in another lightweight plastic tank.
Since the material is removed from the vehicle, large scale chemical recycling routes are available to regenerate the hydride, making a wider range of potential hydrides available.
As the thermolysis, hydride regeneration and storage functions are now separated it is possible to keep the system weight to a minimum.
Cella Energy Markets
Better batteriesWe would all like our laptop batteries to last longer, and the military would like to provide a simpler way of providing soldier power for a 72-hour mission. Small hydrogen PEM fuel cells have progressed significantly in the last decade, and are now small enough to fit inside a typical charger carried with a laptop, mobile phone or camcorder. However the fuel cells need a supply of hydrogen. The chemical energy in the hydrogen is combined with oxygen in the air in the fuel cell membranes, to produce electrical energy, heat and water. As long as the hydrogen is supplied, power is produced, so a laptop could stay charged for a week or a smart-phone for a month.
The Cella Energy hydrogen storage materials resemble white tissue paper or Kleenex. Cella Energy has developed a lightweight, low-pressure hydrogen storage material that can be handled safely in the open air. The Cella hydrogen storage material can be manufactured as low-cost micro-fibres. The foundation IP and patent relates to lightweight, low-cost hydrogen storage that operates at normal temperatures and pressures. The material has a high hydrogen density of 6% by weight and releases the hydrogen quickly and cleanly. 6wt% is the original US Department of Energy DoE target set for 2010.
The way the hydrogen is supplied has held up the adoption of these fuel cells up to now because hydrogen storage has only been possible in hydrogen cylinders. These metal cylinders present safety risks and are not practical for large scale market adoption.
Cella Energy is developing the Hydrogen Bag™ that contains micro-fibres. The fibres resemble white tissue paper and can be packaged in any container or even in clothing. There is no need for a metal canister because the hydrogen is stored at normal temperatures and pressures, and is safe to handle in the open air.
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Hydrogen infrastructure for a billion road vehicles – safer than gasolineIn many ways hydrogen is an ideal clean fuel. But one of the major barriers to its widespread adoption is safe, low-cost storage. Current hydrogen vehicle prototypes use high-pressure cylinders or expensive super-cooled liquids, neither are ideal for mass production. Portable power applications that require longer run times than batteries alone can provide, use low-pressure canisters of metal hydrides, but these are difficult to transport.
Cella Energy uses the benefits of nano-structuring to encase hydrides using coaxial electrospinning. Hydrides are materials that contain hydrogen. Electrospinning is a proven low-cost method of producing micro-fibres by wet-spinning polymers. Once produced the fibres can be 30x smaller than a human hair, and together resemble white tissue paper. The fibres have a core-shell structure, where the core is a hydride and the outer shell a polymer. The outer shell polymer safely encapsulates the hydride: it acts as a filter that only allows hydrogen to pass and stops other molecules like oxygen to traverse, making the materials 100% safe.
Today a billion drivers of internal combustion engine vehicles refuel by pumping liquid gasoline and diesel into fuel tanks. This refuelling takes a few minutes and provides ranges of 300 miles or ~500km. While there are risks associated with handling gasoline, these risks are accepted by most drivers.
Gasoline and diesel vehicles are well established and the internal combustion engine ICE efficiency is increasing year on year. However to meet new emission regulation legislation standards around the world and to off-set the rising cost of fuel, the automotive industry is introducing battery electric vehicles EVs and hybrid vehicles. These vehicles use lithium-ion batteries, the technology is new, and the charging infrastructure is yet to be established universally. EVs typically have ranges of up to 100 miles and can take several hours to recharge. Research shows that vehicles need ranges of 300 miles to overcome the phenomenon known as range anxiety or the fear of being stranded. EVs are expensive to develop because they require new electric drive trains, and so are likely to cost more than conventional ICE vehicles.
By contrast hydrogen vehicles can be refuelled in a few minutes and provide a 300 miles or ~500km range. Most conventional ICE vehicles can be converted to run on hydrogen with minor modifications and are known as H2-ICE, or the electric drive trains developed for EVs can be configured as fuel cell vehicles FCVs. Both H2-ICE and FCVs produce zero carbon emissions at the point of use.
Up to now neither H2-ICE or FCVs have seen widespread adoption because there are few places to refuel the vehicles with hydrogen. The early vehicles have used either liquid hydrogen at -253°C (-423°F) or compressed hydrogen cylinders at up to 10,000psi pressure or 700bar (700x atmospheric pressure). Refuelling requires a new high-cost specialist infrastructure of hydrogen refilling stations.
Cella Energy replaces the high pressure cylinders with a conventional shaped fuel tank that can be more easily packaged within an existing vehicle chassis design. Refuelling takes place from a regular fuel pump and requires no high pressure or very-low temperatures. This fits easily within the existing refuelling infrastructure and means hydrogen could be provided for a billion existing road vehicles immediately.
In the first instance this would be a fuel additive that would lower emissions; later this could be a pure hydrogen solution that would produce zero carbon emissions. In a H2-ICE vehicle additives such as Ad-Blue could be used to lower nitrous oxide emissions.
Cella's hydrogen storage materials are able to store hydrogen at a density that meets automotive industry targets, and operate favourably in terms of release speed and conditions, efficiency and cost of manufacture.
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Reducing emissions from airplanesThe Cella Energy hydrogen storage materials could also be added to kerosene, JP-8 or jet-fuel to lower the emissions from aircraft. If used in this way there would be minimal modification of engine design.
Aircraft emissions are of major concern because jet-engines release a cocktail of emissions in the upper atmosphere. But as air travel increases how can the aircraft industry remain competitive and reduce emissions?
Modern jet-engine fuel is primarily kerosene. Burning kerosene, which is a hydrocarbon fuel, produces a cocktail of greenhouse gas emissions including carbon dioxide CO2, nitrous oxides or NOX, sulfur oxides or SOX and other particulate emissions. These are similar to the emissions produced by gasoline or diesel cars, but appear in different concentrations. Environmental scientists are concerned about the long term impact of these emissions in the upper atmosphere.
Because of the large scale of aircraft jet-engines compared to say a car, the emissions are much greater, and so even a small reduction in emissions of say 1% could have a significant affect on global warming.
Cella can add the hydrogen micro-beads to kerosene. The beads have diameters of ~ 0.5 - 5 μm and will not affect engine design, but could reduce emissions significantly. For more details please contact email@example.com
Space rockets ready to goLiquid hydrogen has a specific energy density of about 143MJ/Kg (mega joules per kilogram) compared to regular jet-fuel or kerosene at about 43MJ/Kg.
Liquid hydrogen is one of the most energy dense fuels known to mankind, and it is why the majority of spacecraft, including the NASA space shuttle, are launched using liquid hydrogen.
However liquid hydrogen is very cold, and has to be stored at -253°C(-423°F). This means that to keep rockets on launch pads on standby is technically difficult and expensive.
Cella's hydrogen micro-beads are also a liquid hydrogen fuel but can be stored at normal temperatures. This means rockets can be kept on permanent standby at significantly reduced cost.
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Bringing power ashore from off-shore wind turbinesBuilding wind farms off-shore has many benefits including stronger and more consistent wind, and less environmental impact. The turbines themselves can be bigger, with turbine blades now significantly larger than the wingspan of a Boeing 747.
However to bring the power ashore is an expensive and difficult business.
Typically undersea collection cables connect multiple turbines, and transport the electricity to a transformer – also out at sea. At the transformer the combined electricity is converted to a high voltage for transmission via undersea cables to shore. These undersea cables have to be buried in the seabed to stop them being snagged by fishing vessels. Once the cables reach land, they are connected to the onshore electricity grid. The connections, transmission equipment and transformers required are also expensive. Multiple cables and equipment is required to provide redundancy. Some cables will have to be hundreds of miles long.
The cables require considerable quantities of copper and their costs are vulnerable to the variable price of copper on the commodities market. There is also concern that the high electromagnetic fields created by these high voltage cables could interfere with navigational ability.
Hydrogen – turning wind from an intermittent power source to a consistent oneAn alternative approach, is to use the electricity to produce hydrogen through the electrolysis of seawater. Water is H20, and is converted into hydrogen and oxygen.
The hydrogen can be stored in vessels that can be brought ashore and used to make electricity in a turbine or fuel cell. This also has the benefit of turning the variable or intermittent nature of wind generation, into a consistent or constant power source.
Cella's low-cost, low-pressure approachPreviously storing hydrogen in vessels of this type would have required high pressure tanks. This pressurization or compression would have taken considerable amounts of energy in itself. By using the Cella Energy low-pressure hydrogen storage materials minimal energy is required for the hydrogen storage process. The shipping vessels themselves would be low-cost to construct because they would not need heavy and robust pressurized tanks.
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