As mentioned in the previous post, my new energy storage report, Energy storage conundrum, which mainly addresses issues previously discussed on this blog; but the Report goes into considerably more detail about some of them.
One issue to which the Report has many additional details is the issue of hydrogen as an alternative to batteries as a means of energy storage. For examples of previous discussion on this blog about hydrogen as a storage medium for grid backup, see, for example: “The Idiot’s Answer to Global Warming: Hydrogen” from August 12, 2021 and “Hydrogen is unlikely to ever be a viable solution to the energy storage conundrum.” from June 13, 2022.
At first glance, hydrogen seems to be the obvious solution to the most difficult problems of energy storage to back up intermittent renewable power generation. In particular, seasonal wind and solar power generation models require a storage solution that can pick up excess electricity production gradually over consecutive months, then discharge stored energy over the course of a year. No current battery technology can do anything like that, largely because most of the stored energy would simply dissipate if it were left in the battery for a year before being used. use. But if you can make hydrogen from some source, you can store it somewhere for a year or even longer without significant loss. Problem solved!
Well, there must be something wrong with hydrogen, otherwise people would have used it extensively. And indeed, the problems with hydrogen, while different from the battery storage problem, are nevertheless enormous. Mostly, to produce large amounts of hydrogen without the greenhouse gas emissions you’re trying to avoid turns out to be extremely expensive. And then, when you have hydrogen, it’s very difficult to distribute and handle it.
Unlike oxygen or nitrogen, which is ubiquitous as a free gas in the atmosphere, almost no free hydrogen is available for use. They are all linked together in hydrocarbons (aka fossil fuels – coal, oil and natural gas), carbohydrates (also called plants and animals) or water. To obtain free hydrogen, it must be separated from one substance or another by the input of energy. The easiest and cheapest way to get free hydrogen is to separate it from the carbon in natural gas. This is usually done by a process called “steam reform,” which results in carbon from natural gas being released into the atmosphere as CO2. In other words, obtaining hydrogen from natural gas using an inexpensive steam reforming process offers no carbon footprint benefits over burning natural gas alone. So if you insist on getting the free hydrogen without releasing carbon, then you’ll have to get it from the water by an electrolytic process. Hydrogen obtained from water by electrolysis is called “green hydrogen” by environmentalists, due to the avoidance of carbon emissions. Unfortunately, electrolysis requires a very large energy input.
How much will it cost to produce green hydrogen as a storage medium for a mostly wind/solar grid? My Report first notes that as of today there is almost no production of this green hydrogen:
To date, there has been virtually no commercial production of green hydrogen, because electrolysis is much more expensive than steam regeneration of natural gas, and therefore uneconomical without government subsidies. government. JP Morgan Asset Management’s 2022 Annual Energy Report states that ‘Current green hydrogen production is negligible…’
So we don’t have any major operational projects from which we can get data on how expensive green hydrogen is. In the absence of that, I thought to do an exercise to calculate the wattage of solar panels needed to produce 288 MW of capacity for some jurisdictions where panels can provide electricity directly to consumers or produce alternative hydrogen by electrolysis that can be stored and then burned in a power plant to produce electricity. (The 288 MW figure was chosen because GE makes turbines for natural gas power plants with this capacity and says it can convert turbines to use hydrogen as a fuel.). Here is that assignment as written in My Report:
Consider a jurisdiction with a steady electricity demand of 288 MW. . . . The electricity needs of our jurisdiction can be adequately supplied by burning natural gas in the plant. But for now, let’s say we want to use solar panels to supply the plant with enough electricity and/or hydrogen to supply the company with 288 MW throughout the year. What is the capacity of the solar panels we have to build? Here is a calculation:
• Throughout the year, the jurisdiction will use 288 MW × 8760 hours = 2,522,880 MWh of electricity.
• We started by building 288 MW of solar panels. We will assume that the solar panels produce at a 20% power factor over the course of a year. (Sunny places like the California desert can get 25% power factor from solar panels, but cloudy places like the eastern US and all of Europe get 20% less capacity; In the UK, typical annual solar capacity factors are less than 15%). That means 288 MW of solar panels will only generate 288 × 8760 × 0.2 = 504,576 MWh in a year.
• So, in addition to 288MW of solar panels that directly produce electricity, we need more solar panels that produce hydrogen to burn in the power plant enough to generate the remaining 2,018,304 MWh.
• With 80% efficiency in electrolysis, 49.3 kWh of electricity is needed to produce 1 kg of hydrogen. GE says its 288 MW plant will burn 22,400 kilograms of hydrogen per hour to produce at full capacity. Therefore, it takes 49.3 × 22,400 = 1,104,320 kWh, or about 1,104 MWh of electricity to capture the hydrogen to run the plant for one hour. For 1,104 MWh of power input, we get 288 MWh of electricity back from the GE plant.
• Since the power factor of the solar panels is 20%, we will need to operate the plant for 8760 × 0.8 = 7008 hours of the year. That means we need enough solar panels to produce 7008 × 1104 = 7,736,832 MWh of electricity.
• Again, due to a 20% power factor, to generate 7,736,832 MWh of electricity using solar panels, we would need panels with five times the production capacity, or 38,684,160 MWh. Divided by 8760 hours in a year, we would need solar panels with a capacity of 4,416 MW to generate the hydrogen we need for backup.
• Plus 288MW of solar panels that we started with. So the total capacity of solar panels that we will need to power the company is 288MW using green hydrogen as backup is 4,704 MW.
In other words, to use natural gas, you only need a 288 MW plant that provides 288 MW of electricity consistently throughout the year. But to use solar panels plus green hydrogen backup, you need the same 288MW plant to burn hydrogen, plus more than 16 times that number, or 4,704 MW of solar panels capacity, to direct power supply and generate enough hydrogen for backup .
That calculation assumes a production factor of 20% of the power from the solar panels over the course of a year. Turns out the actual solar power factors are like 10-13% for Germany, 10-11% for UKand so 12.6% in New York. (california, less cloudy, with a power factor in excess of 25%.). Doing the same series of calculations using a 10% power factor for the solar panels, you would need about 9,936 MW of solar panels to provide a steady 288 MW of electricity for the year, with green hydrogen as the storage medium. your storage.
In other words, you will need about 35 times the capacity of your solar panels than the amount of electricity you are committed to providing. The reasons for the big difference include: the sun doesn’t shine completely half the time; most of the time when the sun is shining it is low in the sky; places like the UK, Germany and New York are more cloudy than not; and there is a significant loss of energy both during the electrolysis of water and subsequently the combustion of hydrogen.
Anyone and everyone should feel free to check my arithmetic here. I am quite capable of making mistakes. However, some people have checked this out.
My Report will then attempt to translate the huge incremental capital costs of all these solar panels into a very rough cost comparison of trying to generate 288 MW of fixed electricity from solar panels. solar cells and green hydrogen compared to just burning natural gas in a plant. I received cost figures for the turbine plant and solar panels from a US Energy Information Administration March 2022 report. Use that data:
[T]cost of General Electric turbine power plant 288MW [would be] about $305 million and the cost of 4,704 MW of solar panels [would be] about 6.25 billion USD.
If you need 9,936 MW of solar panels because you live in a cloudy area, then $6.25 billion becomes about $13 billion.
My very rough calculation in the Report, assuming a 20% solar power factor, is that electricity from solar panels plus green hydrogen storage will start to cost between 5 and 10 times more expensive. with electricity from burning natural gas. Assuming 10% solar power factor, make it 10 to 20 times more expensive.
And after all this, we still haven’t solved the additional technical challenges that are so important when working with very light, explosive hydrogen gas. A few examples from the Report:
- Creating enough green hydrogen to power the world means electrolysis of the oceans. Fresh water supplies are limited and are especially scarce in the best places for solar energy, namely deserts. When you electrolyze the ocean, you not only electrolyze the water but also the salt, which then produces large amounts of highly toxic chlorine, which must be neutralized and removed. Alternatively, you could desalinate the seawater prior to electrolysis, which would require additional energy input. There are people working to solve these problems, but the solutions are remote and can be very expensive.
- Hydrogen is only about 30% energy dense by volume like natural gas. This means that it takes about three times the pipeline capacity to transport the same amount of hydrogen energy as natural gas. Alternatively, you could compress the hydrogen, but that would also be an additional and potentially large expense.
- Hydrogen is much more difficult to transport and handle than natural gas. Using existing natural gas pipeline infrastructure for hydrogen is difficult, because many existing gas pipelines are made of steel, and hydrogen causes steel to crack. Subsequent leaks can lead to explosions.
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