INFRASTRUCTURE AND DISTRIBUTION

The complete cycle of low-carbon H2—Part 2

K. Gupta, M. Ethakota and P. Kuhikar, Technip Energies, Noida, Uttar Pradesh, India

Sensitivity analysis of H₂ production cost

The cost of H₂ production depends on the natural gas price for SMR, the electricity cost for electrolysis and biomass, and the electricity cost for the biomass route. In SMR, the operating cost is most sensitive toward natural gas prices, as shown in Fig. 9.

 

Fig. 9. Relationship of H₂ price with natural gas price.¹

 

In the case of biomass gasification, the cost of H₂ production depends on electricity and feedstock cost. Fig. 10 and Fig. 11 show how H₂ price varies with electricity and biomass costs.

 

Fig. 10. Operating cost with regard to power cost for the biomass route.

 

Fig. 11. Operating cost with regard to biomass feed cost for the biomass route.

 

The production cost of H₂ through electrolysis heavily depends on the electricity price (Fig. 12). The electricity price must be less than $25/MWh–$40/MWh to compare to the cost of blue H₂.

As renewable electricity prices decline around the world, green H₂ is an increasingly economically attractive option. Green H₂ production costs will further decrease as electrolyzer costs decline, as efficiency increases and as the capacity utilization factor (CUF) of renewable energy installations increases. H₂ from biomass is more appealing if electricity and biomass are available at a cheaper rate.

 

Fig. 12. Operating cost with regard to power cost for the electrolysis route.

 

Case study: H₂ for FCEVs

The transportation sector is predicted as a promising near-term user of H₂. H₂ must undergo purification, compression, storage, precooling and dispensing before reaching the vehicle. A typical flow scheme for the H₂ cycle, from purification through dispensing, is shown in Fig 13.

Purification. H₂ is used for FCEVs after meeting the quality as specified in ISO 14687:9001 (Type D). PSA is used for purification in the SMR and biomass production routes. H₂ recovery of 80%–85% is expected across PSA. In the electrolysis process, the required quality is achieved through the de-oxy and dehumidifying units.

 

Fig. 13. H₂ production to dispensing cycle.

 

 

Compression. At present, H₂ dispensing is done at either 350 barg or 700 barg, while H₂ is produced at 20 barg–30 barg from SMR (depending on natural gas pressure and process configuration), 2 barg–30 barg from biomass (depending on the use of atmospheric gasifier/reactor or pressurized gasifier/reactor) and 2 barg–35 barg from electrolysis (depending on the type of electrolyzer). In all production routes, H₂ must be compressed through a compressor. Typical compressor types are diaphragm, ionic and hydraulic. Approximately 1.8 KW/kg of H₂–2 kW/kg of H₂ of power is consumed for H₂ compression at 350 barg.

Storage. Compressed H₂ is stored to avoid fluctuations at the downstream process and as a buffer to cover a brief shutdown at the upstream process. The gaseous H₂ is stored at 500 barg–900 barg in Type 1 storage. The storage is divided into high-pressure, medium-pressure and low-pressure storage and filled through a priority panel. In the electrolyzer, the renewable electricity source is intermittent for 4 hr/d–6 hr/d, which leads to a larger storage requirement compared to the SMR and biomass routes, which are continuous processes.

Dispenser and precooling unit. H₂ is dispensed into the vehicle at 350 barg or 700 barg. The dispenser is connected with storage through a sequencing program and equipped with a precooling unit. The precooling unit cools the H₂ before it is filled into the vehicle, as H₂ tends to heat up when expended due to the reverse Joule–Thomson effect. The precooling requirement depends on the ambient condition and residual pressure in the vehicle tank. The dispensing rate varies from 1.8 kg/min–3.6 kg/min, depending on the vehicle type.

If the H₂ production cost is $2/kg, then 90% of the additional cost is due to compression, storage and dispending (CSD) operating cost, and 75% of the additional cost is because of investment, which makes the final cost $5.5/kg. The investment cost of purification with CSD (PCSD) is $12,500/tpy with PSA and $8,500/tpy without PSA. The cost contribution of each component in the dispensing cycle is depicted in Fig. 14.

 

 

Fig. 14. Cost component split in the dispensing cycle.

 

 

The final H₂ fuel price at the consumer level for different H₂ production routes is shown in Table 4. Gray and blue H₂ are the cheapest ways to produce fuel H₂ with the least investment. The production scale makes a significant difference for SMR—i.e., as the scale becomes more prominent, the costs decrease faster. Green H₂ requires the most investment and is the costliest to produce due to low efficiency and intermittent renewable electricity. Red H₂ prices are in the medium range, but they must overcome high feedstock costs and require a sincere effort for commercialization that will automatically reduce investment.

Onsite generation vs. transport. H₂ is costly to transport due to its low density. H₂ is transported in gaseous form (200 barg–500 barg) and liquid form. It is estimated that H₂ transported at 200 barg in gaseous form adds $1.5/kg–$2/kg or more to the H₂ cost—e.g., moving H₂ over 1,000 km in a truck costs approximately $3.5/kg H₂.² The transport of H₂ also results in an energy loss of 10%–12% of the H₂ itself. In general, it is cheaper and easier to produce and use H₂ onsite; however, much research is ongoing for the cost-effective transport of H₂.

Integration of H₂ production routes

The possibility of integrating all three H₂ production processes is being explored. A diagram for integration is depicted in Fig. 15.

 

Fig. 15. Integration of three H₂ production routes.

 

The electrolyzer process produces O₂ as a byproduct, and the biomass oxy-steam gasification process requires O₂. In the blue H₂ process, the captured CO₂ must be stored or used. This captured CO₂ can be combined with the H₂ from the electrolyzer to produce chemicals. The SMR process produces excess steam, which can be utilized for biomass gasification. In these ways, the processes are shown to be mutually beneficial when integrated with one another.

Recommendations. Interest is rising to establish H₂ as a solution to decarbonize various sectors, with a primary focus being transportation. H₂ also finds application in hard-to-electrify segments of industry including steel, cement, fertilizer and methanol.

Different H₂ production routes such as SMR, biomass and electrolysis, based on different feedstocks and power sources, can complement one another instead of competing. SMR is an established and cost-effective solution and can adopt carbon-capture measures to produce carbon-neutral H₂. The SMR process is a better choice where natural gas prices are low, where CO₂ disposal is easy and economical and where the scale of production is large. The SMR route can be used to establish the infrastructure of the H₂ economy.

The biomass route is efficient in disposing of biomass and has great acceptability for empowering rural agricultural economies. It can also be made carbon neutral. Commercial-scale biomass-based production of H₂ and management of feedstock supply chains are critical challenges for red H₂ production.

Electrolysis is emerging as an effective producer of carbon-neutral H₂. The electrolysis process is the best choice where excess electricity is available at a cheaper rate from a renewable source. Low renewable electricity costs and maturity of technology are essential for the success of green H₂.

All three H₂ production technologies will play critical roles in achieving the goals of mitigating climate change and advancing the energy transition. It is essential to identify the right fit and application(s) for each production pathway. The integration of all three processes may prove to be a lucrative and mutually beneficial option, and requires further study.H₂T

 

Acknowledgment

The authors express thanks to Narik Basmajian and Koos Overwater of Technip Energies for their valuable support. They also give special thanks to Professors S. Dasappa and Anand of the Indian Institute of Science at Bangalore and Dr. Vasu Gollangi of Bharat Heavy Electricals Ltd. at Hyderabad for their expert reviews.

 

Literature cited

  ¹ Gupta, K., I. Aggarwal and M. Ethakota, “SMR for fuel cell grade hydrogen,” PTQ, December 2020.

  ² International Renewable Energy Agency (IRENA), “Green hydrogen: A guide to policymaking,” November 2020.

  ³ BloombergNEF, “Hydrogen economy outlook,” March 30, 2020.

  ⁴ Hall, W., T. Spencer, G. Renjith and S. Dayal, “The potential role of hydrogen in India,” The Energy and Resources Institute (TERI), December 2020.

  ⁵ Vigna, M. D. et. al, “Carbonomics: The rise of green hydrogen,” Goldman Sachs, July 8, 2020.

  ⁶ International Energy Agency, “Energy technology perspectives 2020,” September 2020.

  ⁷ Fuel Cells and Hydrogen Joint Undertaking, “Development of water electrolysis in the European Union,” February 2014.

  ⁸ IRENA, “Green hydrogen cost reduction: Scaling up electrolysers to meet the 1.5°C climate goal,” December 2020.

 

Kalpana Gupta is Deputy Chief Engineer in the Process and Technology Department of Technip India Ltd., part of Technip Energies. She has more than 20 years of experience in the downstream oil and gas industry. She is actively involved in projects for decarbonization, sustainable chemistry and the H₂ economy. She holds a BTech degree from Malaviya National Institute of Technology Jaipur, an MS degree from the Indian Institute of Technology (IIT) Delhi and a diploma in renewable energy from The Energy and Resources Institute (TERI) Delhi, with coursework in waste to energy from the National Program on Technology Enhanced Learning from IIT and The Indian Institute of Science.

Maruthi Ethakota heads the process and technology department of Technip India Ltd. He has more than 25 yr of experience and has executed several H₂ and syngas projects worldwide. He also worked as Product Development Manager at Technip Benelux and was involved in developing new technologies for the H₂ and syngas product lines. He holds an MS degree in chemical engineering from IIT Kanpur.

Pallavi Kuhikar is a Principal Process Engineer in the process and technology department of Technip India Ltd. She has more than 13 years of experience in the petrochemicals, refining and biofuels sectors and is involved in projects for biofuels, refining, petrochemicals production and the H₂ economy. She holds a BTech degree from the Priyadarshini Institute of Engineering and Technology Nagpur.