Reposted by NOT MANY PEOPLE KNOW THAT
January 9, 2021
Guest post by Joe Public
Click here to access 201126_Drax_20Q3_005-1.pdf
Drax’s most recent Quarterly Bulletin has a section on storing excess wind power:
I picked out these particular claims for observation:
1. Why is the capacity and discharge rates of these electricity storage systems not mentioned? The British quadruple-pumped hydropower plants have a total storage capacity of 26.7 GWh and a delivery rate of 2.86 GW.
http://www.withouthotair.com/c26/page_191.shtml
2. “… 28 TWh storage … comparable to the entire natural gas storage facility in Great Britain in the form of underground salt caverns.”
2.1 Not entirely correct. It is comparable to the entire natural gas storage facility Gt Great Britain has in the form of underground salt caverns plus LNG storage. We have ~ 18,000 GWh conventional storage plus ~ 13,000 GWh LNG storage.
https://mip-prd-web.azurewebsites.net/DailySummaryReport
2.2 The calorific value of hydrogen is fair 3.3 kWh / m ^ 3 vs. approx. 11.1 kWh / m 3 for Nat gasTherefore, low energy density H2 has less than 30% of the energy content of Nat Gas per unit volume at STP.
Hence our energy storage capacity for hydrogen is not 28TWh, but only 8.4 TWh with the same pressure.
3. “… Maybe some of these wind farms should produce something other than electricity. With electrolysers, electricity and water can be converted into hydrogen. The excess electricity generated in 2030 could generate 670 million kg of hydrogen. That would be enough to fill 133 million fuel tanks in fuel cell vehicles like the Toyota Mirai or to heat nearly 2 million homes. “
3.1 It’s disappointing to see the intentional obfuscation by mixing units – (the Weight of hydrogen produced) to deny readers the opportunity to easily compare relative numbers. Why did the report’s authors fail continue to use electricity-Industrial units of TWh / GWh that you have already used in your article?
1 kg of hydrogen contains 33.33 kWh of usable energy.
http://www.h2data.de
3.2 With the production of “37 TWh excess electricity” in 2030, 670 million kg of hydrogen could be generated. “
The “37 TWh of excess electricity” therefore produces 670,000,000 kg of hydrogen. But this hydrogen mass only has 22.3 TWh usable energy. ie 66% more electrical energy is required to make one unit of energy available via the hydrogen power.
3.3 It was said “…. (670,000 tons of H2) would be enough to fill 133 million fuel tanks in fuel cell vehicles …”
There is no mention of the energy required to compress low-density H2 into these 133 million fuel tanks.
Approx. 4 kWh of energy would be required to compress 1 kg (33.3 kWh) H2 to 700 bar.
https://www.hydrogen.energy.gov/pdfs/9013_energy_requirements_for_hydrogen_gas_compression.pdf
This means that (4 / 33.3) 12% of the available “37 TWh surplus electricity” is required to simply compress the H2 into those 133 million fuel tanks. This then means that only 33 TWh are available to produce the H2 just (22.3 TWh × 88% =) 19.6 TWh of usable H2 are available if it is stored at 700 bar.
Consequently, 37 TWh initial electrical energy input leads to only 19.6 TWh of hydrogen are available at the entrance to the vehicles’ fuel cells.
1.89 energy units Input to receive 1 energy unit in the fuel cell.
The fuel cell is then only 40% – 60% electrically efficient. This means eThe end-to-end process efficiency requires approximately 3.78 units of energy input to get 1 unit of energy OUTPUT from the fuel cell.
https://www.energy.gov/sites/prod/files/2015/11/f27/fcto_fuel_cells_fact_sheet.pdf
4th The authors believe that “hydrogen could potentially be brought ashore at a lower cost by piggybacking the existing oil and gas pipelines that have limited use as the North Sea fields develop.” Don’t explain what they are, however as “piggyback”.
4.1 Do you think it is feasible to inject hydrogen into an operational oil pipeline? Do you realize that natural gas imports must meet National Grid’s strict quality control standards that hydrogen does not meet?
https://www.nationalgrid.com/de/gas-transmission/data-and-operations/quality
4.2 Regarding steel pipelines – both underwater and on land – the authors may not be aware of the chemical effects of hydrogen:
“Conversion of the UK gas system to hydrogen transport” explains:
“At ambient temperatures and pressures below 100 bar, the main concern is the integrity of high strength steel Hydrogen embrittlement. Hydrogen diffuses into all surface defects that occur due to material defects, construction defects or corrosion, which leads to a loss of ductility, increased crack growth or the formation of new cracks. These ultimately lead to material failure. It is believed that higher pressures increase the likelihood of material failure, although no threshold value has been defined independently of other factors … “
https://www.sciencedirect.com/science/article/pii/S0360319913006800
Paul’s additional comments.
- Their calculation that we need 1000 times more storage than currently sums up why storage can never be the answer to a long-term interruption (as opposed to the daily requirement), especially since pumped storage accounts for about 95% of the current storage, which cannot be easily increased .
- These projections are based on 40 GW offshore wind, so the problem of excesses becomes much more acute when more wind capacity is added later.
- The excess wind power of 37 TWh corresponds to about a quarter of the total wind power. If this surplus had to be thrown away, it would effectively add a third to the cost of wind power.
- As Joe rightly points out, the capacity of salt caverns in terms of hydrogen is not 28 TWh. It is less than 8 TWh, which means that most of the excess cannot be converted into hydrogen and stored.
- Claims of enough hydrogen to fill 150 feet of fuel tanks would mean maybe 3 million hydrogen cars. In reality, it is unlikely that there will be more than a few thousand people on the move by 2030, and there is little prospect of many more in 2050. There may be a market for fuel cells in trucks and buses, but it will most likely be decades away. (Aside from everything else, where do cars and trucks get their hydrogen from in winter when there is no excess wind power?)
- It is good to see that they confirm that excess wind power will also be available on the continent, even with low wind power.
But I’ll leave the final comment to Drax!
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