26 Oct Independent report to the Dutch Government
Global sustainability objectives require a technological breakthrough
Climate and sustainability objectives for, among other things, the transport sector and the sustainabilization of energy generation are necessary to combat climate change. They are laid down in national and international agreements such as the Energy Agreement and the Paris Agreement.
The manner in which these objectives can be achieved is not yet clear. At present many sustainable solutions are still relatively expensive when compared with fossil alternatives and the generation of electricity or hydrogen for use in zero-emission vehicles is not yet sustainable. This is not yet possible because completely sustainably generated solar and wind electricity cannot yet provide a continuous and stable energy and power supply without large-scale storage.
In addition, many applications, such as existing sustainable vehicles, still have drawbacks. Batteries that are used in electric cars have a limited operating range, use scarce metals, and when they are dismantled, if they are recycled and reused, care must be taken to prevent these substances from ending up in the environment. The capacity is still insufficient for heavy applications. Hydrogen is still expensive to use for transportation and as a storage medium. For vehicles to achieve a high operating range, high pressure and thus a heavy and large pressure tank are necessary.
Due to the lack of efficient storage technologies the complete sustainabilization of electricity generation is not yet possible.
A breakthrough seems possible in the area of hydrogen.
Hydrogen has potential as a storage medium for energy and as a fuel.
Although the energy density of a kilogram of hydrogen is high, hydrogen is difficult to store because the substance has a low density. In order to move around with a practical amount of hydrogen, it has to be stored under high pressure. This means that the tank has to be heavier and has to be equipped with additional systems to regulate the pressure.
Storing hydrogen by binding it in another substance could be a solution to this problem. Hydrogen could then be stored and transported under atmospheric conditions. This provides several benefits:
- Lower storage and transportation costs;
- Elimination of the cost of compressing the gas;
- Reduction of a possible security risk caused by high pressure, making filling stations in urban areas possible;
- Utilization of the existing distribution network for fossil fuels;
- Depending on the substance used to bind the hydrogen, a lower claim on space;
- Possibilities for application in all modes of transportation: not just road transportation but also aviation and shipping.
- Many possibilities of application for the generation of heat and electricity, both static and mobile.
Several of these types of solutions are being researched.
The TU/e is researching the possibilities of formic acid. Hydrogen binds itself to carbon dioxide to form liquid formic acid (CH2O2). At room temperature, the substance is liquid and not flammable. Inside the vehicle a catalyst converts the formic acid into hydrogen gas. The reaction is therefore reversible, but the storage density still needs to be increased to be practically applicable. Furthermore, the lifetime of the catalyst is still insufficient.
The TUD and Nuon are researching the possibilities of binding hydrogen in ammonia (NH3) for the Magnum power station in Eemshaven. Under the influence of supplied surplus wind energy, hydrogen binds itself to nitrogen to form ammonia. The energy is released again when it is combusted into water and nitrogen. The energy per unit of volume is equal to ethanol. Nuon and TUD expect that large-scale application will require ten years.
H2-fuel systems BV has found a solution in which hydrogen is bound in sodium borohydride, a solid substance, and in the process is diluted with water to become a liquid: H2-fuel. At the same fuel tank capacity, this bonding yields a greater operating range than other alternatives for fossil fuels. With formic acid, ammonia, and hydrogen gas at 700 bar, cars can cover approximately 300 to 350 kilometers on a 60 liter tank. With H2-fuel, more than twice as much at a lower cost. In addition, because of the relatively low cost, H2-fuel seems to offer potential for the storage of energy.
H2-fuel is a sustainable and cost-effective solution with several other benefits
H2-fuel is an energy carrier in which hydrogen is stored under atmospheric conditions. This energy carrier can be transported in solid form, as slurry, or dissolved in a liquid. By adding a liquid activator the stored hydrogen can be released on call and used in a fuel cell to generate electricity (for reaction see Box 1). Highly diluted hydrochloric acid is currently used as an activator for mobile applications, while a catalyst or a combination of both a catalyst and highly diluted hydrochloric acid is used for static application.
Box 1: reaction H2-fuel
NaBH4 + 2 H2O è 4 H2 + NaBO2 + heat
1 kg of hydrogen (500 mol) requires 4.7 kg of sodium borohydride (125 mol) and 4.5 kg water (250 mol). When the reaction creates 1 kg of hydrogen, 40 MJ of heat is produced.
Half of the hydrogen atoms are derived from sodium borohydride and the other half from the (ultra-pure) water.
The reaction is instantaneous.
This process and the reaction rate have been validated by TNO. In a laboratory setup, 98% of the theoretically present hydrogen and heat were produced immediately upon addition of the activator liquid.
In Japan, China, and the US, a patent on this reaction process has been granted. In Europe the patent is pending.
Compared with other methods to produce hydrogen for use in fuel cells H2-fuel has a number of benefits:
- Storing, producing and consuming hydrogen under atmospheric conditions reduces transportation and storage costs and requires no energy to compress hydrogen. There are also no security risks and no heavy-duty pressure tanks are required to store the hydrogen;
- When bound to a solid substance or diluted, the hydrogen’s volume is smaller than that of hydrogen as a gas. The cost of transportation to supply filling stations is therefore lower than when hydrogen gas is supplied;
- Compared with solutions in which hydrogen is transported under pressure a vehicle requires less tank volume. The operating range of a vehicle running on H2-fuel is expected to be much higher than that of a vehicle with the same fuel tank capacity that runs on compressed hydrogen. The range is two and a half times as great for cars with a pressure of 700 bar, and five times as great for trucks with a pressure of 350 bar;
Box 2: ratio of operating range of hydrogen under pressure and H2-fuel
The volume per kg of hydrogen is 9.225 kg. This consists of 4.5 l of water and 4.725 kg of sodium borohydride. The specific weight of sodium borohydride is 1.07 kg/l. Mixed with 4.5 l of water, the slurry takes in 4.5 kg/1.0 + 4.7 kg/1.07 = 8.9 l per kg of hydrogen. In a 60 l tank 6.7 * 98% kg = 6.6 kg hydrogen can be stored. A Hyundai ix35 with a 120 l tank can transport 5 kg of hydrogen. At the same tank volume the operating range of a vehicle running on H2-fuel is therefore two and a half times as great as that of compressed hydrogen gas at 700 bar.
Production and use do not produce harmful emissions. The only emission is water vapor from the fuel cell, which is partly reused. The hydrogen’s carrier (spent fuel) is retained in the vehicle and can be used again after it has been recycled;
Figure 1: Diagram of process inside vehicle
- The production or recycling of the energy carrier can take place completely CO2 neutrally with sustainably generated wind or solar energy at a time when there is an abundance of sustainable energy. Consequently, the use of H2-fuel can reduce the temporary imbalance between supply and demand;
- The production of H2-fuel does not require any scarce raw materials. In addition to energy and water, it requires sodium and boron, which are recycled with only small losses. The largest suppliers of boron are Turkey and the United States.
- The existing distribution network for fossil fuels can be used. Adapting it requires a small investment in proportion to the cost of constructing new hydrogen filling stations with compressed hydrogen, and it is also possible in urban areas.
- In addition to the generation of electricity through fuel cells, heat can be provided by means of a catalyst.
- Furthermore, temporary surpluses of sustainably generated energy can be stored and released later.
The combination of these properties leads to a comparatively low cost per kilogram of hydrogen, when this principle is applied on a large scale and the processes are optimized further.
- Based on the purchase of the various raw materials the cost per kilogram of hydrogen is lower than the cost which is currently possible. The cost is approximately € 5.5 per kilogram instead of € 10 per kilogram;
Figure 2: Comparison of cost per kilogram of hydrogen
Explanatory note to Figure 2
The cost per kg of hydrogen for local electrolysis and gas and steam reforming was quoted from the ‘Driving a car that runs on hydrogen in Overijssel’ study. The cost of hydrogen when produced centrally differs. If hydrogen is supplied free of charge, the price is close to € 6 per kg. When produced centrally through the steam reforming of methane, an approximate € 3.80 per kg is added (striped column).
H2-fuel can be produced for less than € 6 per kg. A kg of hydrogen requires 4.7 kg of sodium borohydride and approximately 5 liters of (ultra-pure) water. Sodium borohydride costs € 1.03 per kg (supplied in Rotterdam). The price of UPW is less than 1 cent per liter. The total cost per kg of hydrogen with a release efficiency of 98% and € 0.30 for domestic transportation and handling costs per kg is € 5.26. No energy is required for the reaction inside a vehicle. Energy is released.
- By recycling the residues that remain in the tank into new H2-fuel saving, on purchasing costs is possible. If surplus wind energy is used, the energy carrier can be produced 100% sustainably. At standard electricity prices, the cost of this step is higher than when sodium borohydride is purchased. This is explained by the low efficiency of electrolysis where the production of the required hydrogen is concerned. If methane is used, the cost is lower (see figure below, recycling B);
Figure 3: Schematization of reaction in vehicle (left) and recycling of spent fuel in factory into new energy carrier
- A further optimization is possible by producing the hydrogen required for the synthesis of the energy carrier internally through the H2-fuel reaction instead of through electrolysis. A part of the energy carrier is then supplied for external use by the end user and a part serves as raw material for the production of the new energy carrier. This double use is possible because approximately half of the hydrogen is produced from water which is consumed and the other half is produced from hydrogen atoms which are released in the energy carrier’s reaction;
- The third means of optimization in the production of the energy carrier is the use of the heat that is released when hydrogen is produced internally. This causes the energy that needs to be added to the synthesis process to be lower. This yields further cost savings of more than 65 cents per kilogram;
Figure 4: Schematization of reaction with means of optimization to improve sustainability
(B) and lower costs (C-D)
- In practice, as a result of these means of optimization, the cost per kilogram of hydrogen in the fuel cell for the end user can fall from € 5.26 per kilogram to € 4.10 per kilogram. The cost of the installation must however still be added. At a theoretical efficiency of 100% in the factory and no recycling losses a price of € 3.30 per kilogram should be possible;
Figure 5: Comparison of cost per kilogram of hydrogen for various process optimizations of H2-fuel
- On the basis of the cost per kilometer calculated in the Driving a car that runs on hydrogen in Overijssel study (see Figure 6), this cost is expected to already be competitive at the current price of diesel. The existing alternatives require a much higher diesel price for a comparable or lower cost per kilometer than diesel. Using the assumptions made, the cost of H2-fuel per kilometer for trucks is comparable to that of diesel at a diesel price of € 0.68 to € 1.05. On top of that, there are the benefits to the environment and the climate.
Figure 6: Comparison of break-even diesel prices for various production alternatives for hydrogen
In addition to the mentioned optimizations, there is a possibility that the applications from the publications of Dr. Ying Wu (USA) and the Arhus Scientific Institute (Denmark) for the synthesis of sodium borohydride in H2-fuel technology can be applied, which could lower the cost per kilogram of hydrogen further.
This has not happened yet because it is uncertain whether the laboratory results indicated in the publications are actually achievable. The publications leave questions unanswered regarding the actual effect. Answering these questions will require the cooperation of the Århus Institute or the validation of these processes.
Annex: explanatory notes on costing
In this annex, the costings for the different steps of the H2-fuel process are explained. This does not yet include the cost of the installation. In many cases, these are preliminary assumptions. In terms of yield, the reaction of H2-fuel with ultra-pure water (UPW) has been validated by TNO (step A). For the synthesis process (steps B-D), several processes are available in the literature. These would have to be combined with the process patented by H2-fuel systems BV in a subsequent development step (step A).
Table 1: Steps in the optimization of the cost of H2-fuel
Cost of transportation
Regarding the cost of transporting the raw materials to the filling stations no distinction has been made between the various alternatives and transported raw materials. In total, approximately 4.8 kilograms of sodium borohydride needs to be supplied per kilogram of hydrogen. The ultra-pure water is produced on-site from tap water.
The cost of freight transport is € 1.05 per kilometer. The capacity of a category 6 truck is 6000 kilograms. A surcharge of 20% applies to tank trucks. It is assumed that, on average, 150 kilometers will have to be traveled to the filling stations and 150 kilometers will have to be traveled back. The cost per kilogram of raw material is then € 0.063. For the end user, this is € 0.30 per kilogram of hydrogen.
Cost of electrolysis
The electricity cost for the electrolysis is determined using a wholesale price of € 0.09 cents per kWh or € 0.025 per MJ. The practical efficiency of electrolysis is relatively low. The production of half a kilogram of hydrogen requires 90 MJ. Because of the assumption that recycling losses are 5%, 5% of sodium borohydride is added and 95% x 90 MJ = 86 MJ is required to produce hydrogen to convert spent fuel into sodium borohydride. This costs the customer € 2.14 (86 MJ x 2.5 cents per MJ) per kilogram of hydrogen.
Cost of synthesis and recycling of spent fuel
The electricity cost of the synthesis is determined using the same wholesale price of
€ 0.025 per MJ. If surplus wind energy could be used, the cost is lower.
If hydrogen from electrolysis is used for the synthesis (step B), an estimated 105 MJ of energy is required to produce the energy carrier. This is equal to the theoretical energy increase, at 90% efficiency and at 5% supplementation of sodium borohydride (95% * 99 MJ / 0.90 = 105 MJ). The cost for this is 105 MJ x 2.5 cents per MJ = € 2.62.
If hydrogen from internal reaction is used, synthesis requires an estimated 168 MJ of energy to produce the energy carrier. This is equal to the theoretical energy increase, at 90% efficiency and at 5% supplementation of sodium borohydride (95% * 159 MJ / 0.90 = 168 MJ). The cost for this is 168 MJ x 2.5 cents per MJ = € 4.19.
When the internal reaction’s heat is used (assumed 70% efficiency), synthesis requires an estimated 168 MJ – 70% * 40 MJ = 141 MJ of external energy to produce the energy carrier. The cost for this is 141 MJ x 2.5 cents per MJ = € 3.52.
Calculation of the cost of purchasing NaBH4
The cost for purchasing sodium borohydride consists of the cost of purchasing in China and the cost of transportation from China to the Netherlands in a 20-foot container. For large volumes (more than 20 tons), the cost is $ 1.00 per kilogram FOB China. At an exchange rate of € 0.89 per dollar, 1 kilogram of sodium borohydride costs € 0.89 per kilogram.
Transporting 21,640 kilograms from Shanghai to Rotterdam in a 20-foot container is estimated at € 3000. Transportation adds € 0.14 per kilogram. The cost including transportation is then € 1.03 per kilogram.
Per kilogram of hydrogen in NaBH4, 9,383 kilograms of NaBH4 are theoretically required. Per kilogram of hydrogen end use and a yield of 98% of the theoretical maximum 9,383/2/0.98 = 4.8 kilograms of NaBH4 are required. The cost for this is 4.8 kilograms x € 1.03 per kilogram = € 4.92 per kilogram of hydrogen. In the case of recycling losses, 5% must be supplemented each time. This equates to 5% x € 4.92 per kilogram of hydrogen: € 0.25 per kilogram of hydrogen.
Calculation of UPW cost
The cost of using ultra-pure water (UPW) consists of the cost of tap water and the cost of the additional purification at the filling station. Each kilogram of hydrogen requires approximately 5 liters. (4.5 liters with some losses):
- The cost for bulk consumption of tap water is € 0.55 per m3. This amount is based on Vitens’ rates for businesses.
- The cost for the purification installation was estimated on the basis of the following values specified by Pure Water Group Ruckhen.
Service life installation 10 years
Installation cost € 40,000
Operating costs € 3,800 per year
Production capacity 5 m3 per 24 hours
Production days per year 353 days (12 days of maintenance)
The production capacity is 1765 m3 per year.
At 8% interest, the price per cubic meter for purification is:
(€ 5,961(annuity investment) + € 3,800)/1,765 m3 = € 5.53 per m3
The cost per m3 incl. tap water is then € 6.08 per m3
The UPW cost for 1 kilogram of H2 is € 0.03 per kilogram of H2 for 5 liters.
 Slurry: the energy carrier has not been dissolved in the water, but has been divided into small discrete particles, so that the slurry can be pumped.
 When kilograms of hydrogen are referred to in this report, this relates to the amount of hydrogen which the end user can use as a power supply for the fuel cell or the catalyst. Half of this amount consists of the hydrogen in the sodium borohydride and the other half of the ultra-pure water with which the sodium borohydride reacts.
 Crystal Energy Projects BV (2010), Driving a car that runs on hydrogen in Overijssel Study
 Source category 6; www.detransporters.nl/tarieven.