U.S. utilities that are mapping out plans for achieving 100% carbon-free power are running into the same challenge: they haven’t figured out a cost-effective way to get there. The clock is ticking, as utilities typically operate with a 20-year planning horizon. Additionally, more than 130 US cities and municipalities and several states have committed to 100% renewable energy, with implementation dates ranging from 2040-2050.
“There is no one solution, no one technology. The optimal solution will be a mix of technologies,” said Joseph Ferrari, general manager for utility market development at Wärtsilä North America, a smart technologies company focused on marine and energy markets. The company has been specifically researching ways that utilities can meet clean power mandates.
For California, the fastest and cheapest path to 100% clean energy will involve expanding solar and wind generation, while adding fast starting, flexible, generation plants. The idea for these plants, according to new Wärtsilä white papers, is that they burn gas now and use synthetic renewable fuels produced using power-to-hydrogen and power-to-methane processes as those technologies advance.
Wärtsilä’s modeling work suggests that a large distributed energy storage system that is capable of providing weeks – rather than hours – of renewable energy storage can be developed using these synthetic hydrogen and/or methane fuels, which can be stored indefinitely.
In these approaches, the amount of battery storage needed in a utility’s power system would be reduced; power generation from synthetic renewable fuels would occur only as needed to maintain reliability when both short-term battery storage and renewable energy sources are unable to meet load.
“For renewable developers, using power-to-hydrogen and/or power-to-methane processes could help them optimize their renewable energy resource,” Ferrari said, adding that to thrive, renewable developers need to be able to sell all of the electricity that they produce.
“What our studies have shown is that as you reach 100% renewables, the amount of oversupply and over-generation from solar in particular, on an annual basis, is staggering. It has nowhere to go and is literally wasted,” Ferrari said.
“Either [synthetic] fuel reduces the costs of the system,” he continued, noting that in both instances the idea would be to use excess renewable power to produce these carbon-free and carbon-neutral fuels.
Perfect the enemy of the good?
A power-to-hydrogen pathway’s biggest advantage over a power-to-methane pathway is that it is carbon-free; its exhaust is water. Also, when produced using excess solar or wind, electrolysis can be produced almost anywhere.
Hydrogen’s drawback is that even though hydrogen is inexpensive to produce, it can’t be used in a power system without a complete overhaul of the entire gas-fuel infrastructure. According to Ferrari, this is because the current utility infrastructure can only handle 15-30% hydrogen by volume.
“The biggest advantage that [renewable power-to-methane] has over hydrogen is that the entire United States is crisscrossed with gas pipelines, compressors and storage systems, that can all be used today with renewable synthetic methane. None of this infrastructure can be used as-is for 100% hydrogen, and there are no thermal power plants that can burn 100% hydrogen today,” Ferrari said. The cost to build a 100MW thermal plant that uses hydrogen should be in the same price and performance range as a natural gas plant, he noted.
The cost of modifying and upgrading pipelines and other components to accommodate hydrogen is unknown, however. Also, the design of pure hydrogen engines and turbines is still some years off for commercial application, according to Ferrari. Direct air carbon capture (DACC) technology, which is central to the power-to-methane process, is further along, he added.
The power-to-methane pathway for decarbonizing the electric power sector involves using renewable energy that would otherwise be curtailed to produce carbon-neural methane. According to Ferrari, this could be done in a three-step process that involves DACC of CO2 from the atmosphere (as the source of carbon), electrolysis of water (as the source of hydrogen) and methanization to combine the carbon and the hydrogen to produce methane. Because the carbon used to create the synthetic fuel is recycled from the air, the combustion of the methane would be carbon neutral.
In this type of synthetic methane approach, the final molecule can be stored and transported using the existing natural gas infrastructure, and the methane produced using this process can be used in any thermal technology that can burn gas.
A common criticism of both power-to-methane is that it is extremely energy intensive because all three steps require energy.
“Power-to-gas is less efficient than some other forms of energy storage, but it’s using energy that would otherwise be totally wasted and unused by the power system,” he said. “Even if it costs more surplus energy to make one useable unit of electricity for the grid, it can be stored and banked for months of duration. If you tried to do that with batteries, well, it would drive systems costs through the roof,” he added.
Battery storage parallel
Ferrari believes that the power-to-methane route is today where battery storage was 10-15 years ago. “Batteries have their place, but it’s becoming clear renewables plus batteries at the scale of California is untenable… What is needed are storage mechanisms with durations of weeks, not hours,” he said. “Even though the need for this will not manifest until close to the 2045 deadline in California, for this to be viable in 2045 a lot of work needs to be started now,” he added.
“From what I’m seeing, it is already started,” Ferrari said, noting that Colorado recently mandated that certain percentages of gas in the pipelines be renewable by set dates. “This will force gas companies to get renewable methane from somewhere. Bio-sources and landfills can only go so far,” he said. Similarly, in California, a new renewable fuels bill that would require at least 20% of gas in the pipes in CA be renewable by January 1, 2030 was introduced in February. The bill, if passed, would allow renewable fuels that reduce or avoid greenhouse gas emissions to be used.
“These mandates will do to the power-to-fuels industry what RPS standards did for solar and what storage mandates did for batteries. [It would] accelerate adoption, introduce competition and reduce price over time,” Ferrari said.
Tread carefully
DACC technology has its fair share of critics who see it as offering a lifeline to the fossil fuel industry because of the burgeoning industry’s ties to fossil fuel companies and its use of the existing polluting infrastructure.
“That could not be further from the reality. Methane or other synthetic hydrocarbons do not reduce carbon footprints, they eliminate them. Every CO2 molecule released from combustion was taken from the air to begin with, no fossil fuels involved anywhere in the process,” Ferrari said. At some point fossil fuel use will be phased out, and at that point the only option the aviation and shipping industries will have is to use renewable, synthetic carbon-neutral hydrocarbons, which requires DACC, he added.
Already, an effort to use a power-to-fuel process to make synthetic carbon-neutral jet fuel is underway at Rotterdam The Hague, he pointed out.
Even so, some environmental lawyers say that any legislation that would enable DACC technology to be used by utilities would have to be written with extraordinary care to make it clear that utilities cannot use DACC to blow through their carbon budgets. Carbon Engineering, Climeworks and Global Thermostat are among the handful of companies active in the DACC space currently.
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Using DACC synthetic methane with Allam cycle turbines to capture CO2, the LCOE is projected to be equivalent to existing combined cycle plants, and sequestration would only add half a penny a kWh for carbon *negative* electricity. Further, given that it’s desirable to tax CO2 emissions, it follows that CCS should be subsidized.
“Transport and storage costs would add between –1 and 1 US$ct kWh–1 to this range for coal plants, and about half as much for gas plants:
https://www.ipcc.ch/site/assets/uploads/2018/03/srccs_chapter8-1.pdf
I’m commenting mostly on this paragraph:
“What our studies have shown is that as you reach 100% renewables, the amount of oversupply and over-generation from solar in particular, on an annual basis, is staggering. It has nowhere to go and is literally wasted,” Ferrari said”.
I used the hourly wind generation and hourly load data for the entire year of 2017 in MISO. I multiplies the actual wind generation each hour by various numbers to see when an hour saw wind generation exceed consumption, and by how much.
To oversimplify, when MISO had 6.5 times the current (2017) wind resource of 17,225 MW’s, it generated 50% of its total consumption, with 0.7% of that total generation (or 1.4% of the total wind generation) being above existing consumption. At 9.5 times the current wind resource, MISO saw 70% of its total consumption with a little less than 9% of total consumption being generated by wind above the need.
I realize that the fit between load and wind generation may not be as good in other parts of the country, and I consider that the absurd preoccupation with solar over wind may have tweaked another similar effort in a less than optimum direction, but I disagree with Ferrari that this is “staggering”. Even 100% generation of MISO’s actual need by wind alone would result in only 26.2% of total potential above-demand generation.
It is important to recognize the ability of the wind industry to feather blades and to reduce generation when it is not needed. This above-demand generation is likely to be a desirable commodity, once there is enough of it. I don’t know who would build a facility to depend on excess power which was available only five or ten percent of the time, even if it was priced at half or less of the wholesale price. I suspect that in the early years that excess generation will be sold at modest discounts to wholesale, to existing customers who have flexibility and can use some dispatchable load.
More to the point, when thinking these issues through with the right information, it is obvious that the optimum future is going to be about half and half wind and solar, with solar’s share growing only when solar’s cost is substantially lower than wind. Solar must be cheap enough that solar plus storage is cheaper than wind without to command much more than 50% of the market. I haven’t worked out what share of the market is likely to belong to solar without storage because MISO doesn’t have an hourly load data set for an entire year for solar. If anyone knows where an hourly set for wind exists for a year for a large scale region where both an hourly set for solar and an hourly set for all consumption exists, please let me know at Ned.Ford@fuse.net
With the MISO analysis I am comfortable believing in a future which has no more than about 20% of total capacity served by some form of storage. I am eager to agree that hydrogen or methane in existing natural gas plants is the presumptive winner in the storage race at this time, but there are a lot of contenders, and a lot of storage exists already, including most of the existing hydro and pumped storage.
I also would like to call attention to “Carbon Engineering” a company which has a great website, and is selling gasoline and jet fuel made from renewable electricity and water (taking carbon out of water is essentially identical to taking it out of the air, and apparently saves them a step). They are doing so at a premium, but they are also building their own renewable generation and expect to be competitive (I would add, probably once oil prices return to post-coronapause norms).
Let’s make a couple of things clear: Carbon Engineering is not capturing carbon from the air any more if they ever were. Air and water exposed to air exist in equilibrium for carbon content, and seek it if that balance is disturbed. Taking carbon from the atmosphere to use as a fuel is not going to draw down atmospheric carbon, since it goes back into the air as soon as it is burned. It is a means of facilitating 100% renewable electricity, not an excuse of any sort that promotes or justifies continued fossil fuel use. And we already have the means to eliminate 100% of fossil and nuclear plants for less money than continuing to operate them, and all other fossil fuels including plastics and chemical feedstocks. Read an article in Science titled “Renewable Bonds” in September, 2019 to get a sense of how this is unfolding.
The entire movement to clean energy is delayed time and again by activists who do not understand the economic drivers of our energy industries. Since 1998 FERC has implemented wholesale competitive electric exchanges. While some states and some utilities still have captive customer bases due to state laws and retrograde practices, all of them are affected by the trends created by wholesale deregulation.
The development of wind and solar is being fought by existing fossil and nuclear plant owners, but they do not have the control to prevent clean energy from entering the mix if the lawmakers do not give it to them. Efficiency is the third leg of the clean energy mix, and I’m ashamed of the activists who do not trust the utilities enough to learn how to tell whether efficiency programs are valuable.
Finally, we need about 120,000 MW’s of new wind and solar every year for 20 years to make this happen. Divide this number by U.S. generation and multiply by your state’s share of it, and make that your goal for your state. U.S. wind construction is expected to be double what it was last year, and solar will be 50% larger if the virus doesn’t help or hinder. Since late 2017 wind and solar prices have been lower than the cost of electricity from existing fossil and nuclear plants (and hydropower, for what that’s worth) just about everywhere in the world.
Let’s get our priorities straight. Expand the rate of new wind, solar and efficiency, and everything else will follow, because it is desirable. This is the first growth opportunity the electricity industry has seen in over 60 years, and they haven’t even realized it yet.
Comment to:
“What our studies have shown is that as you reach 100% renewables, the amount of oversupply and over-generation from solar in particular, on an annual basis, is staggering. It has nowhere to go and is literally wasted,”
My observation is that such power-to-hydrogen units are best applied in low voltage grid (in the EU – networks under management of DSOs) and combined with the gneeration coming from the same locality. We have implemented such cases as this one (https://www.next-kraftwerke.com/company/case-studies/electrolysis-hydrogen-with-excess-renewables) in southern Germany, where the electrolyser is taking advantage of ‘excess’ electricity from wind park located in the same DSO network and is used to. The electrolyser is steered from our VPP to:
– avoid exports of electricity from DSO level to TSO level in the first place
– generate green hydrogen for the nearby industrial clients and gas netowrk in the municipality
– depending on price forecasts and the current utilization of the gas and electricity network, to deliver control reserve to the national grid at any given second.
Try with cars and ships and jets then homes buildings and factories before trying to make eatable bio foods that are non harmful and can clean up the soil from industrial farming.