May 3, 2020 § 1 Comment
Several of my readers asked me to comment on Michael Moore’s latest film, Planet of the Humans. One asked specifically for commentary on the contention in the film that progress in the use of renewables causes increased use of fossil fuels. I slogged through the one hour and forty minutes and did not find it said just that but could see how that could be inferred.
The film conducts an equal opportunity trashing of most darlings of clean energy: solar energy, wind energy, biofuels, electric vehicles (hydrogen and battery driven) and biomass energy. Did note keep count, but the last probably gets burnt the most. Prominent environmental organizations come in for lashings, either for supporting one or more of those listed above or for taking donations from folks who made money doing something deemed objectionable, such as logging. The usual whipping boys, oil and gas, and even coal, are mostly spared. In fact, the omissions are almost as interesting as the inclusions.
The film title notwithstanding, the content is very US centric. While externalities are discussed, such as tailings from mined minerals, the biggest atmospheric pollutant killer, particulate matter, does not get even a footnote. This even though the bulk of this pollution is from biomass combustion. They trash biomass but miss this connection seemingly because their messaging is on how wrong everybody (especially prominent environmental NGO’s) is on biomass being renewable. Even 100-minute documentaries have time limitations, I get that. Particularly when essential minutes must be spent on two takes on an allegedly 500-year-old cactus being bulldozed for the Ivanpah solar thermal plant. We were spared a prairie dog being brutalized. But important minutes were spent on primates on a leaf denuded tree.
I will first address the issue of increased use of fossil fuels with further penetration of renewables. Solar energy is properly criticized for its diurnality requiring back up generation or storage. Footage is devoted to outdoor events powered by solar having backup generators or power from the grid. Event support people are interviewed in what is cast as an expose, sadly of a well-known issue. But even though fossil fuel is often used to level the load where solar is the main source, any use of solar displaces fossil fuel derived electricity. I suppose one could argue that this shortcoming of solar will always keep fossil fuel in business. But that ignores advances in storage which do not, or minimally, require fossil fuel. Also, and here is the US centric part, the over a billion folks without electricity can most advantageously be served by solar (many are in high solar intensity regions) combined with microgrids, potentially eliminating grids and the fossil fuel powered plants connected to them. Backup power can be with biomethane derived from animal waste. This is by way of example only. The point is that folks with nothing will settle for something, warts and all, when it comes to affordable energy.
Speaking of biomethane, this film does not parse the biofuels field. It paints with a broad brush, using ethanol from sugarcane and corn as the whipping boys. This is too easy. Many, including I, consider ethanol from food crops to be a bad idea, even if it can be accomplished without accompanying deforestation and open field burning of residue (practices implied as commonplace in the film). For fuel substitution in gasoline or diesel, methanol from a variety of sources, not the least animal and municipal waste, is far preferable. This last is not mentioned, and I do not expect it. This film is about problems, and the wrong headed thinking by all but the narrator, not resolutions.
The broad-brush strokes are particularly evident in the very long critique of biomass combustion. The contention is made that biomass is not a renewable resource. While, once again dealing in absolutes, they still managed to strike a bit of a chord with me. The fundamental premise of biomass being renewable is that plants consume CO2 and when they die, the CO2 released is the same as if it is combusted. The argument goes that one is better off burning for a use rather than letting it die. And, if a new plant is grown in concert with the combustion, the biomass burnt is carbon neutral. By contrast, fossil fuel combusted has no offset regeneration. Accordingly, biomass combustion is a net positive on carbon emissions.
Reality intrudes. If trees hundreds of years old are used for this purpose, even if replanted, the time scale of regeneration is inadequate. On the other hand, if fast growing trees are grown and harvested for this purpose and replanted on a planned basis, one is closer to neutrality. The most benign, and unarguably sustainable source is slash. This is the residue of tops, branches and leaves left after logging operations. Add to that the woody waste from sawmills. Finally, small diameter trees removed to encourage the growth of the more desirable forest species (or for reducing the impact of forest fires), are also a viable source. We are left to conclude that many factors are involved in determining whether biomass combustion can be considered a net positive for carbon mitigation. Declaring all woody biomass as renewable, as some jurisdictions have done, together with associated credits, is counterproductive. It could, and likely does, encourage harvesting of forests without proper management. Policy in this area ought to be more nuanced.
The film is generally long on criticism and short on solutions. Were I a proper reporter, I would watch the film over again to confirm this abiding feeling. But I simply do not have the stomach for it.
May 3, 2020
August 2, 2020 § 12 Comments
The two principal sources of renewable energy share a serious shortcoming. As has been discussed in these pages over the years, wind and solar do not generate electricity when the wind does not blow, and the sun does not shine. Germany gets 40% of its power from renewable sources. But on certain days, that percentage jumped up to 75% and on other days it plummeted to 15%. The (literally) rainy days had electricity augmented from a variety of sources, including batteries. But the days of surplus sometimes required idling of the generation.
Great advances have been made in lowering the cost per unit in both wind and solar. But the need to level the load has never been more important because those very advances have increased the footprint. Some have rushed to use natural gas generators to fill the intermittency gap. This has caused consternation, with some positing the notion that renewables perpetuate fossil fuels because of this dependency. This concern ignores the fact that storage is being investigated at many levels.
Electrochemical storage is the only reasonable option for devices that are carried or move. In many cases, the options are even more limited to light weight batteries. But stationary applications have other options. One that has been in use, where feasible, is pumped water storage. Excess electricity is used to pump water to a high storage site, such as at a dam. When needed, it flows back down to generate electricity. Danish windmills utilize Norwegian hydroelectric sites for this purpose.
The flavor of the day is hydrogen. Excess electricity is used to electrolyze water, producing hydrogen and benign oxygen. The hydrogen may be stored on location to be used to power turbines to produce electricity when needed. In this it serves a similar purpose as does natural gas for the back up generators. As in the case of natural gas, the relatively low duty cycle stretches the pay back period of the capital equipment. Efforts are under way to reduce capital and operating costs. In the former area, expensive platinum electrodes are being replaced with base metal with novel coatings. Operating efficiency improvements are also being targeted. By its very nature, the method is conducive to small scale distribution. Electrolysis to produce hydrogen may be here to stay.
Produced hydrogen could find applications other than for generating electricity. An interesting variant has been piloted for over a year in Cappelle-la-Grande, a town in northern France, by the energy firm Engie, where the hydrogen is blended into existing natural gas pipelines. Hydrogen is a very small molecule and initially there were concerns regarding leakage. But a 25% blend was found to be retained and did not materially corrode the pipes. Furthermore, household burners were found to operate efficiently with that mix. In fact, the mix produced a cleaner burn. Most European countries permit the blend. Some are considering repurposing natural gas lines to exclusively distribute hydrogen.
Hydrogen is an important reagent used in all refineries. Hydrogenation of edible oils is another application. But the workhorse application for this source may well be the admixture into natural gas lines for domestic and industrial use. Because of the low volumetric energy density of hydrogen, storage of hydrogen in the form of ammonia is also being considered. The liquid is easily stored and transported under conditions similar to those for propane. The conversion to ammonia, using nitrogen from air, is straightforward. Utilization can be directly as a fuel in an internal combustion engine, or by catalytic dissociation back to hydrogen for use in that form in a fuel cell for an electric vehicle or any other purpose. Research is under way for improvements in this space, including ammonia production at lower temperatures.
Pipeline transport of hydrogen is feasible but expensive, especially for small volumes. Ammonia, on the other hand, can be transported in pipelines at a cost of about USD 0.20 per kg hydrogen per 1000 miles. This is less than 5% of the expected cost to produce renewable hydrogen at solar and wind installations. The US currently has nearly 3000 miles of ammonia pipelines. Ammonia is a leading candidate for renewable hydrogen storage and distribution.
The main takeaway from this discussion is that renewable energy requires storage, and that storage in fluid form is likely to lead the way. An alternative to using the stored fluid to generate electricity is to use it for a different purpose. This solution for monetizing electricity from periods of excess supply would require the supply troughs to be augmented from another grid source. Hydrogen and ammonia will be important players in the renewable energy world. Alas, silver bullets went out with the Lone Ranger.
August 2, 2020