1:1:E:3. Hydrogen

Long-term sustainability of a base requires solving the problem of providing heat and power during the Antarctic winter. For several months out of the year, a base below the Antarctic circle will be cut off from its solar resources. During this time, it must rely on chemical fuels. Various forms exist. Hydrocarbon fuels are energy dense, portable, and compatible with well-established technologies, but must be imported. This creates a bottleneck. Storing energy that's generated from sunlight during the summer is the most attractive option for a sustainable presence.

A note about the technical figures in this section: As this is an exploration of concepts, and we're trying to establish minimum requirements, some values have been rounded down. When this has been done, the new values are within 1% of the originals.

ELECTRICITY to HYDROGEN to ELECTRICITY (EHE):

Proposed Hydrogen Energy Scheme

The concept is simple:

1. Generate electricity using solar panels during the summer, when sunlight is abundant.

2. Run it through an electrolyzer to split water into hydrogen and oxygen.

3. Collect the hydrogen, and use it as fuel when it's needed.

Hydrogen gas can run combustion engines, power fuel cells, and be burned to provide heat. The process is clean, safe and reliable. The system acts like a rechargeable battery, storing energy for later use.

Hydrogen has an indefinite shelf life, high energy density (by mass), and good cold-weather performance; unlike propane or butane, it won't freeze in Antarctic temperatures. The benefit therein is twofold: first, no energy needs to be wasted keeping the fuel warm, and second, fuel cells or generators can be started immediately without first having to melt frozen fuel.

Step 1: Production

Various electrolyzers are available commercially as off-the-shelf systems. The specifications of the Cummins HySTAT-10 are used here. This is a small-scale, modular unit that uses an alkaline solution of water and potassium hydroxide or sodium hydroxide to produce hydrogen.

HySTAT-10 performance:

Energy use: 55-60* kWh / kg H₂

Max. hydrogen production capacity: 0.875 kg H₂ / hr

Energy density of hydrogen (LHV**) = 119 MJ/kg = 33 kWh / kg

Therefore, this electrolysis system can produce a volume of hydrogen gas containing 28.875 kWh, every hour, using 55 kWh of energy input.

The efficiency of this step is 52%

*Depending on age: older units are less efficient. Efficiency is projected to decrease by 1% for every 8,500 hours of operation.

**LHV = Lower Heating Value, in which exhaust gases are vented.

Step 2: Storage

The hydrogen must be compressed and stored. Possible ways to do this include:

1. Storing it under pressure in hollow tanks.

2. Dissolving it into a chemical matrix (like lithium hydride) within the tanks.

Whichever option is superior in terms of safety and reliability will be employed.

Compressing hydrogen gas for storage will cost energy, decreasing the overall efficiency of the EHE system; how much this will impact efficiency is being investigated.

Step 3: Use

The hydrogen the electrolyzers produce during the summer will be used during the winter, providing heat and electricity to run the station. Most of this electricity will come from fuel cells, which reverse the electrolysis reaction, producing water and heat as byproducts.

Fuel cells are generally about 55% efficient¹. The station's overall fuel efficiency can be increased if fuel cell waste heat is used to supplement hab heating requirements; this is an argument for locating fuel cells near or inside habs' thermal envelopes. Capturing as much waste heat as possible from all electrical power sources will be SOP for the station.

::Several example station configurations and resulting solar array sizes, based on hydrogen needs. This section will explore running on solar-hydrogen exclusively, with other techniques discussed on the main page. Temperature data points from Byrd is useful, because as an inland base, they are much lower than what's expected near the coast. If the station is designed to withstand Byrd temperatures, it should be well prepared for real-world conditions. Basically, take coldest month's average temperature, and plan for entire year to be that cold. Make sure enough hydrogen can be produced to meet this need. Additionally, have double the amount of biodiesel needed to meet this need on hand, as a backup. Diesel generators and heaters will have been used at the beginning of the station program, and now provide redundancy.

Based on data collected at Byrd Station (between 1961 and 1990²)

Not factoring in the energy lost compressing the hydrogen gas for storage, or the energy gained by capturing waste heat, the EHE system has an estimated maximum overall efficiency of 28.6%.

¹ Fuel cell efficiency <FUEL CELL EFFICIENCY LINK>

² Byrd climate data, via NOAA sftp://ftp.atdd.noaa.gov/pub/GCOS/WMO-Normals/ANTARCTICA/AM/89125.TXT