The Great Green Hope

A non-starter by the numbers.

Green Hydrogen has emerged as the great green hope of the climate change alarmist community. It would be produced using emission free, intermittent renewable energy generated by wind and solar generators. It could be used for long-duration energy storage, as motor vehicle fuel and as a replacement for natural gas in residential and commercial space and water heating and in numerous industrial process applications. The quantity of Hydrogen required would depend on the ultimate applications and the percentage of those applications served by the green Hydrogen.

Production of green Hydrogen in the quantities required to make a meaningful contribution to achieving Net Zero in these applications would require that sea water be used as the source., since it is far more abundant than fresh water, which is in limited supply in many parts of the world. The Hydrogen would ultimately be combusted or otherwise reacted, releasing water vapor, approximately 70% of which would return to the oceans directly as rainfall while the remainder would return to the oceans indirectly.

The current industrial approaches to producing Hydrogen by electrolysis require the use of pure water. There are approaches to producing Hydrogen directly from sea water being researched, but none have so far been demonstrated on a commercial scale. The current approaches to purifying sea water for electrolysis consist of filtration and distillation and condensation or reverse osmosis desalination. The “all-in” cost of a 100 million gallon per day sea water desalination plant is approximately $1 billion.

The pure water production of this desalination plant would then be fed to a hydrolyzer, which would be capable of producing approximately 1 kilogram (kg) of Hydrogen per 11 kg of inlet water. (100,000,000 gal * 8 lb. per gal / 2.2 lb. per kg = 364,000,000 kg) water or (364,000,000 kg / 11 kg water per kg Hydrogen = 33,000,000 kg) Hydrogen. The higher heating value of Hydrogen is 39.39 kWh per kg or (39.39 kWh/kg * 3,413 Btu/kwh = 134,438 Btu/kg). Therefore, daily Hydrogen production of (33,000,000 kg * 39.39 kWh/kg = 1,300,000,000 kWh) or (1,300,000,000 kWh * 3,413 Btu/kwh = 4,436,456,000,000 Btu) could be produced from this desalinated water stream. At an electrolyzer cost of approximately $1,000 per kw, the cost of a plant with this capacity would be (1,300,000,000 kWh * $1,000/kW / 24 hrs = $54,167,000,000) and the cost of the Hydrogen produced would be approximately $5-6/kg or approximately ( $5.50/kg / 134,438 Btu/kg = $40.91 per million Btu,) compared with ~$3.00 per million Btu for natural gas. Others have estimated even higher costs.

The resulting Hydrogen must then be transported and stored for later use. Hydrogen can be stored as a high pressure gas, as a cryogenic liquid or with an absorbent or adsorbent, depending on the intended use of the hydrogen. Hydrogen for use as a vehicle fuel would typically be stored as a 5,000 - 10,000 psi gas and delivered to the vehicles from a storage cascade. Hydrogen used as a replacement for natural gas or propane for residential and commercial space and water heating or for process applications would be compressed to approximately 1,000 psi, piped to the point of use and regulated to lower pressure for use.

Hydrogen for electricity production could be stored in underground caverns and fed to either fuel cells or gas turbine generators to generate electricity at an approximate efficiency of 60%.

The US currently consumes approximately 32 trillion cubic feet of natural gas per year for all applications. The output of the desalination plus hydrolyzer facilities described above would be approximately 4.4 billion cubic feet per day, or approximately (4.4 bcfd * 365 days per year = 1.6 trillion cubic feet per year), or 0.5% of current annual natural gas consumption.

US DOE is funding significant Hydrogen production and storage research which might reduce the Hydrogen costs calculated here. However, if Hydrogen is to be a major player in long-duration energy storage, or as a transportation fuel, its application cannot wait to begin until the results of this research are commercialized.

Originally published here.