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Long Term Energy Storage Using Green Hydrogen

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Julian Jackson's picture
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Transitioning to a low-carbon energy system requires the input of very large amounts of renewable energy, including intermittent wind and solar power. To ensure sufficient power is available, clean energy needs to be stored so it can be dispatched when needed to meet demand. Lithium-ion batteries are the most popular system at present, but they only are for short-duration storage, that is, six hours or less. However there is also a strong ecological and business case for long-duration storage and the current front runner is green hydrogen, made from renewables.

Mitsubishi recently did a survey and these were some responses: 54% of participants who work for utilities (or other organizations that can directly deploy energy storage) said they needed storage that was dispatchable for eight to 24 hours at a time. Also, 35% said they needed to dispatch stored power for more than 24 hours at a stretch.

Utilities can put green hydrogen to use today with hydrogen turbines currently on the market. Initially, these turbines use a blend of natural gas and green hydrogen — but as they evolve, the fuel blend will move to 100% hydrogen as hydrogen supply and infrastructure advance. Long-duration energy storage could prove especially helpful for utilities affected by bad weather or natural disasters lasting days at a time, which can trigger extended outages and rolling blackouts. Whenever resource adequacy is challenged, long-uration energy storage supports power reliability without compromising progress toward decarbonization targets.

The US DOE announced its Energy Earthshots Initiative second target in July 2021: the Long Duration Storage Shot will spawn innovation to reduce the cost of utility-scale, long-duration energy storage by ninety per cent within a decade. Alongside this government program, many utilities are making their own large commitments to hydrogen-fueled generation. These investments, in turn, are likely to spur the expansion of hydrogen infrastructure and drive down the cost of green hydrogen (currently about $2.50/kg).

Long term energy storage will be essential to managing loads in the future, when fossil fuel and nuclear plants are being closed down, and their baseline power will have to be replaced on the grid.

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Roger Arnold's picture
Roger Arnold on Feb 18, 2022

There is, indeed, a need for serious long term energy storage if we're ever going to make an energy grid based on intermittent renewables workable. The problem with advancing green hydrogen as a solution for the required long term energy storage is that it presupposes that such a thing as "green hydrogen" exists.

For all practical purposes, it doesn't. What exists instead is fool's green hydrogen. Fool's green hydrogen is electrolytic hydrogen produced under circumstances in which every kWh of electricity consumed for hydrogen production must be compensated by a kWh of dispatchable electricity produced from fossil fuel resources. That's nearly always. Only at moments when renewables are servicing 100% of demand and there's surplus RE capacity remaining to service the load from electrolysis is it possible to produce truly green hydrogen.

Since the round trip energy storage efficiency of hydrogen is only 40%, 60% of the electrical energy that went into producing hydrogen is wasted. The carbon footprint of fool's green hydrogen. used for energy storage is then 2.5 times larger than if the load serviced from hydrogen energy storage had simply been serviced by dispatchable generation from fossil resources.

Debjit  Roy's picture
Debjit Roy on Feb 23, 2022

Very well Articulated.

While we all are striving to transform our energy needs from traditional fossil fuels to renewable resources, it's imperative to be able to store renewable energy due to its intermittent nature. Also, this storing will help us stabilize the Grid frequency and reduce changes of blackouts.

Nathan Wilson's picture
Nathan Wilson on Mar 2, 2022

The energy content of 1kg of H2 is about the same as in a gallon of gasoline, which is 34.4 kWh thermal.  That $2.5/kg green H2 price equates to 7.3 ¢/kW, which is triple the price of fossil gas, even before you pay for a storage cavern, or run it through a 40-60% efficient peaking power plant (you'll get low efficiency with lots of throttling up & down to follow variable solar & windpower).

 

The logical outcome for such an implementation is that any grid that adopted such technology would need a demand-response system to automatically turn-off the lights, heating, and air-conditioning at the homes of cost-conscious consumers (i.e. no heat on the coldest days, or AC on the hottest).  Such a system would be extremely vulnerable to cyber attacks which crash the whole grid.  In other words, society (especially the poor) would have to make some pretty big sacrifices for such a system to be accepted.

A more likely outcome from a large renewables deployment is that the transition would stall at around 50% penetration, with cheap fossil gas making up the balance, no need for expensive energy storage, and the world failing to adequately reduce our CO2 emissions.  Note that in countries with coal as the dominant fossil fuel, even 50% renewables is probably unaffordable, because fossil gas is simply the most economical way to balance renewables.

To Roger's point, with 50% renewables, there will be significant curtailment of renewable energy that exceeds short-term needs.  But that still does not mean that we'll be finally able to make green hydrogen.  The curtailment will seriously hurt the economics of renewables at around 10% discarded (or zero-priced) electricity.  But that 10% zero-priced electricity is still much too low a duty cycle for the electrolyzers that would make green hydrogen; the growth of renewables will stall before there is enough clean generation to make green-hydrogen affordable.

On the other hand, with nuclear and hydro, we can affordably reach >90% clean energy on the grid without the expense of energy storage or green hydrogen (based on the past success in France, Sweden, and Switzerland).  So no one would have to make any sacrifices (except the fossil fuel industry).

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