Again in World Warfare II, the American army had an issue, the identical one the Russians are dealing with at this time. It wanted absurd quantities of gasoline for its army efforts, and aboveground tanks had been big, stationary, thin-skinned targets filled with flammable materials. So the US army began digging underground caverns for its gasoline provides close to bases the place it may and utilizing gravity to run the gasoline right down to the bottom.

In 1940, the US authorities was wanting on the winds of warfare and regarded on the gasoline tanks at Pearl Harbor and stated to itself, that’s a strategic weak spot. In any case, a variety of the Pacific Fleet was operated out of the Harbor, and in the event that they couldn’t put gasoline within the ships and planes, then that they had a variety of costly metal, not a army power. In order that they surveyed the close by hills and settled on a web site 2.5 miles (4 km) from the harbor. It grew to become the Crimson Hill Underground Gasoline Storage facility.

Web site of Crimson Hill Underground Gasoline Storage in O’ahu courtesy Google Maps

They utilized some progressive building methods together with vertical tanks and increasing shafts with rock conveyors on the backside that enabled them to construct the power way more shortly than historic methods. It wasn’t in time for them to be full for the Japanese assault in 1941, nonetheless. The development space grew to become the grave web site of lots of the casualties.

Gasoline flowed via a number of pipes for several types of gasoline working down a tunnel to the harbor. A pumping station on the harbor managed the circulation. The fairly excessive elevation of the power in comparison with the harbor meant gasoline could possibly be loaded in a short time.

Tanks superimposed to point out their location at Crimson Hill facility Courtesy EPA

Initially supposed for under a handful of underground caverns with room for enlargement, the positioning quickly grew to twenty caverns able to holding 250 million gallons, approaching a billion liters, of assorted forms of liquid fuels for warfare machines.

A couple of a long time later, the priority was not fueling an enormous warfare fleet and air craft, however poisoning the bottom water of O’ahu. This grew to become a difficulty in 2014 when operations workers managed to spill 27,000 gallons (102,000 liters) of jet gasoline whereas refilling the power. That led to a bunch of soil and water desk testing, and unsurprisingly discovered that a long time of fossil fuels had left elevated ranges of unhealthy hydrocarbons within the ecosystem. Consuming water remained inside federal and state well being normal ranges.

The ability was left in operation and issues went again to regular till 2021. Two spills that 12 months. One impacted the consuming water of 93,000 army personnel, and the opposite dumped 19,000 extra gallons of jet gasoline. Numerous hew and cry. Visions of 250 million gallons of diesel and jet gasoline flowing into the in any other case tourist-friendly ocean. Sierra Membership and different teams chiming in saying it was time to close the power.

And so, in 2022 Secretary of Protection Austin gave the order to the DOD to drag the plug. So lengthy, Crimson Hill. Numerous work ensued. Plans, feedback on plans, rejections of plans, alteration of plans, beginning of labor, and so on. The army expects to totally shut the power down by 2027, however depart the tanks in place for some unspecified future use that doesn’t contain gasoline or different poisonous substances.

At present somebody reached out to me to ask about one potential use they’d thought up, which is to repurpose the caverns for pumped hydro storage of electrical energy. Up till the purpose the query was requested, I had no concept the power existed. Twenty seconds of studying urged that the positioning was extra prone to be a brand new Superfund web site requiring a long time of remediation relatively than one thing you wished to flush water via commonly. My opinion hasn’t essentially modified, however I stored going.

The primary query I requested myself was what the top peak was. That’s the peak from the floor of the water in a hydroelectric facility to the generators. It’s necessary as a result of the formulation for power from pumped hydro is mass occasions gravity occasions peak. Kilograms occasions 9.8 m/s^2 occasions meters, as a result of I’d want to finish up in helpful measurements, joules and MWh. The power in a pumped hydro facility scales linearly with peak, clearly, and whereas the stress supplied for the gasoline appeared fairly affordable, that doesn’t imply that it was appropriate for pumped hydro.

Naturally none of that was in any public documentation I may discover on the power. Maybe that’s one thing to do with army secrecy, or maybe nobody thought anybody would care. Off to a useful software which provides the elevation at a selected latitude and longitude, with these supplied by Google Maps. Elevation above sea degree turned out to be 104 meters.

However the excavated caverns themselves had been 30 meters underground. Exhausting to bomb, don’t you already know. So the utmost head peak was solely about 74 meters. In fact, with 20 unconnected tanks, the water degree doesn’t drop equally because it does in a standard reservoir, which might be one thing you’d need to repair with cross tunnels if this had been to turn into a factor. Nonetheless, the tanks are reportedly sufficiently big to accommodate a 20-story constructing, in different phrases about 280 toes or 86 meters.

Clearly there’s an issue, as a result of the engineers wouldn’t construct the underside of the tanks beneath the extent of the bottom and beneath sea degree. The Google Maps location is beneath the ridgeline, so let’s give it one other 20 meters of head peak so that every one the numbers at the least roughly make sense. 94 meters of head peak, then.

However again to the unconnected tanks, that head peak drops fairly shortly. It’s a reasonably deep however slender reservoir and when 1 / 4 of the liquid is gone, so is 1 / 4 of the top peak. For whole power storage, the common head peak of about 50 meters might be the appropriate one to make use of. (The dearth of precision is as a result of lack of precision within the knowledge.)

We’ve the mass of the roughly billion liters of water which is a billion kilograms, as a result of within the really helpful metric system main items of measurement are associated to 1 one other deliberately. Mass occasions gravity occasions peak provides us a really large quantity in joules, and after we convert that to megawatt hours we get slightly below 140 MWh of electrical energy storage.

Hmmm… that’s not that a lot, however it’s definitely not a tiny quantity. How does that examine to the electrical energy consumption of Hawaii? Effectively, the islands devour about 9,000 GWh yearly, or about 25 GWh a day. About 1,000,000 of the 1.4 million Hawaiians stay on O’ahu, so a lot of the demand goes to be there as effectively. Because the map above reveals, Crimson Hill is adjoining to Honolulu, the largest metropolis within the islands as effectively. Presumably round 18 GWh per day on common is O’ahu’s demand, and a Crimson Hill pumped hydro facility would offer nearly 1% of that. That will be a helpful addition.

In fact, there’s a wrinkle right here. This assumes that the ocean is used as the underside reservoir. Utilizing current our bodies of water as backside reservoirs is a reasonably normal observe in pumped hydro, with the Michigan facility utilizing the eponymous lake, and the Clever Land Funding Crimson John web site in Scotland designed to make use of Loch Ness.

However sea water is far nastier to mechanical gear than contemporary water. Much more minerals, salt being an apparent one, that construct up on issues. And much more microscopic life that likes to cling to issues to create a slurry that barely larger issues can develop on and so forth till you’ve a mass of barnacles and different shell fish with trailing seaweed via which you’ll vaguely see no matter was there within the first place. Probably not an awesome supply of mass for pumped hydro in comparison with contemporary water.

Leaving that apart, there’s the little matter of the fossil gasoline residues within the tanks and pipes. That stuff is leached into the rocks. I’m fairly positive that just about each Hawaiian and a variety of different individuals and the EPA would look unfavorably on commonly flushing the worst of a long time of sludge into Pearl Harbor and the Pacific Ocean. There are in all probability options for that, however they received’t be low-cost, straightforward, or in all probability as fast as constructing the power within the first place.

Is popping Crimson Hill into Crimson John Pacific a good suggestion? Most likely not, however it’s an fascinating concept. Numerous work is being executed round deserted coal mines with the intent to repurpose fossil gasoline extraction websites into closed-loop, off-river pumped hydro, so there’s precedent for way more benign repurposing of fossil gasoline infrastructures.

In fact, there’s a variety of topography in Hawaii, so it’s in all probability higher simply to construct precise closed-loop, off-river pumped hydro with a lot larger head heights and contemporary water. However that doesn’t imply somebody shouldn’t look critically at Crimson Hill and do greater than this serviette math. 140 MWh of high-efficiency storage subsequent to Honolulu that reuses current infrastructure isn’t one thing that ought to be dismissed out of hand.