Many believe that renewables are the only long-term approach to reduce GHG emissions radically. In the absence of fossil fuels with CCS, electricity has to be generated for heating, lighting, and motive power across all economic sectors (residential, industrial, commercial, and transportation), provide energy on demand and keep the power grid stable. What technologies other than wind and sun can be used or need to be developed to meet this enormous demand under stringent quality demands? Can this be achieved or does energy have to be rationed?
Nuclear must be part of the solution but it faces a number of challenges. There are concerns over spent uranium fuel disposal (Yucca Mountain was abandoned), locating new plants (usually on existing permitted sites), and nuclear proliferation (Iran and North Korea). Also, nuclear plants are based loaded and cannot follow load, so if the remaining generation is renewables that has to match load. Should more effort be spent in developing iquid fluoride-thorium reactors to alleviate the concens over waste disposal and proliferation (less reactive waste produced)? These cannot be turned down either so when demand is low should the excess power be used for electrolysis to produce hydrogen that is used for load following? Will nuclear fusion ever be developed (can these reactors be turned down?) It apears that a lot of development is required for these new technologies to come into service, which may be later than required to limit global temperature rise to 2C. By comparison CCS is currently ready for deployment, although not without some risk, and may offer the best short-term solution to reducing CO2 emissions.
There is new research going into producing hydrogen gas from urea (from sewage). If this research is successful, we would have a renewable source of hydrogen. Couple that with hydrogen fuel cells (once it becomes fully commercialised), and you have renewable energy.
Do you know the potential production capacity of hydrogen by digestion? It is a slow process so may not be a major source of hydrogen, but still valuable nevertheless. Potential production sites are certainly widely distributed so localized usage may be more appropriate rather than collection and transmission/transportation to a distribution centre. Maybe fuel cells for power production connected to a nearby grid connection? Any additional ideas?
I don't know much about the conversion process, but I did find an interesting article on it: https://core.ac.uk/download/pdf/1146130.pdf
But yes, placing a urea extraction and conversion plant next to a waste water treatment plant with a hydrogen fuel cell power station nearby would essentially work out to continuous electricity generation from human waste. It would require large scale infrastructure changes, as well as retrofitting current waste water treatment plants, and so while I definitely see this as viable in the long run, I don't expect to see it anytime soon.
Firstly, I think it is worth noting that a clean baseload option is central to meeting the climate change target. IEA has been saying that for some years (https://www.iea.org/newsroom/news/2016/november/speeding-up-carbon-capture-and-storage-needed-to-meet-climate-goals.html) and Global CCS Inst says it more directly ( https://www.globalccsinstitute.com/news/institute-updates/paris-climate-change-targets-cannot-be-met-without-ccs-cop23)
The other baseload options are of course nuclear but just when it was looking to make yet another comeback, Fukusima happened and it is a set back that has already permeated into Europeans shutting down their plants, followed by Korea etc. There are projects happening but more or less where the countries cannot get out of their commitments already made. It is not going to be a dominant option for at least another decade.
Gas both CCGT and reciprocating engine options (for fast response) could well be the mainstay as long as we keep finding gas. Of course we can't make that assumptions. Although LNG is now available to many countries now thanks to the FSRUs - it remains an expensive midmerit to peaking fuel for poorer power hungry nations where the growth is.
Geothermal and biomass are known options but are limited. The World Bank geothermal initiative created a framework to de-risk the exploration part which has been a show-stopper. It seems to work but both technologies are not only very specific to location and quantum but remain a high risk option in many other terms.
CSP was promulgated as a clean baseload option but after a few larger scale implementation, it is now realized that they are complex projects too again with quite specific resource conditions that would limit its potential. The DEWA CSP project created a bit of excitement with its 7.3 c/kWh cost but mind you it comes with a minor investment tag of $14 billion with it!
Solar PV with battery and offshore wind may be the next two cabs waiting to take off. It remains to be seen how much we can push the frontier on cost for both. They would not of course be anywhere near a 'baseload' option. I have to say that after looking at all the excitements of renewable development in Australia as if those will take over coal in a flash, I looked at the generation statistics of 2017 and RE accounted for 6% of the generation - not a lot!
So I think I agree that decarbonzing coal and to some extent gas is critical.
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