In the peak oil and climate change spheres, their are plenty of absolutes about renewable energy thrown around, as is common in many areas of thought. Some of them are more useful and/or accurate than others. The main problem with this generalized approach to renewable energy is that renewable energy isn't any one thing, but more a collection of very different energy sources and collection methods. Something like what sci-fi is, Sci-fi/Fantasy isn't actually a single genre but a collection of a dozen or so overlapping genres (even the difference between Fantasy and Sci-Fi is muddy). The most accurate absolute is that renewables cannot simultaneously solely support a middle class lifestyle (either the current European or American) and produce the energy needed to replace themselves.
One absolute that is not so useful or accurate is this one from the Automatic Earth "Technologically harnessable renewable energy is largely a myth", even through in the original article its more accurate. They refer to higher technology for use in country wide electricity grids, like PV panels, however if you just said that statement without any qualifiers (like they did), then it is completely false. Windmills for grinding grain or waterwheels to run machines directly are technologically harnessed renewable energy, so is solar passive technology, they're just not currently considered 'high' technology (they were back in the medieval ages).
Now I have problems with that AE article, I support the Zero Carbon Australia side, but them I'm training to be an engineer in the sustainable field and so I'm almost certainly biased. I also think that for a variety of reasons we can expect electricity to be fairly common in the future (though much more common in urban areas than in rural areas), but that's another post since it would take some explaining the various corollaries and way's this could be done and the benefits. As it stands, that quote from them is only even vaguely accurate if you classify technologically harnessed renewable energy as used for grid electricity and using modern high technology (as in PV panels or large wind turbines) forms of extraction. But I'm going to take them on their word and use that phrase without those qualifiers, so technology as a blanket statement for any tools or human artifact, since if someone quoted that from the AE or saw that referenced and didn't check, they wouldn't see the qualifiers. Also standing on its own, it provides a good example of a very stupid absolute phrase.
So the first thing you could say about it is that technologically harness-able renewable energy exists, PV, wind turbines, hydro dams etc are pieces of technology that are harnessing renewable energy even if they themselves aren't sustainable on the long-term. however there's the fact that the Romans (and other ancient civilizations) had water wheels, which were artifacts of technology that harnessed renewable energy, windmills are thousands of years old and while solar (in a form other than food) is a recent addition, its feasible to make a very basic solar thermo-electric generators with ancient technology as well as solar cookers.
The meaning of renewable energy is also important, they used it to mean only electricity for the grid which as a blanket statement is absurd. Electricity doesn't need to be used in a grid, heat is another form of energy, so is chemical, kinetic, potential etc. At it's most basic renewable energy refers to sunlight and the various processes it powers, like the wind and hydrological cycle and a few others sources such as tidal and geothermal, which aren't sun powered. The harnessed forms of these energy flows isn't the renewable component, that's the continuation of the flows. But more importantly renewable energy technology isn't any one thing.
As I mentioned above renewable energy technology definition is similar to Sci-fi/Fantasy's, its a collection of dozens of different groups that sometimes only have tangential connections. PV panels and a focused solar thermo-electric generators do the same thing, turn sunlight into electricity, but otherwise they're incredibly different technologies with very different limits, manufacturing, support structures, capabilities and so on. Tidal operates on similar principles to hydro, yet it's not ultimately powered by the sun like hydro is (sunlight drives the hydrosphere, whereas tidal is powered by the orbit of the moon). Biomass produces chemical energy, either as food, ethanol, bio-gas, bio-diesel, wood and so on, which is unusual among renewables who normally provide heat or mechanical energy.
So obviously in terms of capabilities and limitations, they aren't the same. The manufacture of PV panels is completely different to the manufacture of thermo-electric generators (one requires very advanced materials while the other only basic metals) which is again different to the manufacture of solar hot water, or solar furnaces. And so on, basically renewables don't share that many traits with each other, even the typical low EROEI isn't shared by all, hydro's is about 40, though the Wikipedia page says it's 100 in the US. Also important is how these attributes interact with society and the response this draws from society. Renewable energy technology is a collection of various disparate
technologies (low to high tech) that uses energy flows that are continually
replenished by nature, beyond that very few hard and fast rules apply to
all renewable technologies (subsets will have hard and fast
rules amongst themselves). Qualifiers are needed when talking about renewables as a whole.
The absolute that PV panels can't support a modern consumer lifestyle and produce the energy to make itself is accurate and useful partly because it has a qualifier. If the lifestyle its supporting is changed, say to only using 1/4 of its current energy use, then the analysis is different. At that level of energy consumption the PV panel could could support the lifestyle and power its manufacture, though social complexity may be to low to produce them. However an important point needs to be addressed, silicon is not the only material that PV panels can be built out of. Other alternatives exist, like organic solar cells and dye-sensitized solar cells, and there complexity limits could be very different once those technologies are developed.
Weatherize before you solarize is the appropriate phrase, reduce energy
consumption and renewables become far more viable and able to support
themselves at a lower tech base than otherwise. One of the good points about the Zero Carbon plan is that it aims to reduce overall energy consumption by about 60%. Part of that reduction is exploiting the high efficiency of electricity in heating and transport, which is why the plan includes a 40% rise in electricity use. Various processes are very efficient when electricity is used, such as induction furnaces (compared to blast furnaces) or ground heat pumps for heating or cooling which are more efficient than other active heating/cooling systems (through passive housing is a better first option).
So how well renewables work out depends largely on the context their used in, change the context (such as energy use) and how they work changes. Of course the current way we use renewables isn't viable and our societies will have to change because of that, however there is a specific way that happens. Human societies change over time in a process, not sudden leaps or drastic changes, the only times that happens is when some cataclysmic event happens, such as an eruption or 90% death toll due to diseases (Overshoot isn't cataclysmic and even the shortest timescales it will last decades). Some things change and events happen, then some more changes happen and eventually society has reinvented itself. Its a continuous process that when you glance over history looks to be stepwise, but when your living in it, it isn't stepwise but more often a continuous change. If we want to pass through Overshoot with the least amount of trauma and suffering, this needs to be taken account of and used. Demonizing steps in this process just because they aren't the final product is both stupid and in the long run counter-productive.
I'll use Zero Carbon as the starting point for an ideal process, no complications, no roadblocks and the plan works as almost as advertised. This is not how it would go, but this is to provide an example of what I mean in a simple way. So lets say that the various Zero Carbon plans; energy, transport, building, land use, industrial processes and coal export replacement are enacted and they work. Since only the energy plan has been released, we'll use their plan that all transport is electric or biofuel, energy use is 40% of what it is now, also lets assume population is stable (makes it simpler) and so on. So over ten years (or the more realistic 20-30 years) what has changed. Well the society is broadly the same, yet it only uses 40% of the energy, runs on renewables, new supporting technologies have been developed and if all goes well direct solar and wind technologies are being developed and the basic versions implemented (more solar hot water systems). Public transport has exploded in both coverage and usage, well being by measures of material/energy usage would be lower, growth would have stopped or even reversed and Dutch disease would no longer be a problem due to lowered exports and imports, social complexity would also be lower. Additionally the demographics of the economy would change as more people move from services and mining into manufacturing and agriculture.
This is important, since infrastructure changes are slow and expensive the best strategy is one that uses existing infrastructure and phases in technologies and new infrastructure slowly. Now the 10 year plan they have is probably unrealistic, at least with the level of effort that could be mustered for it. 20-30 years is more likely, even though it's taken longer for other similar energy revolutions in the past. The difference this time is that the Zero Carbon plan uses and expands existing infrastructure (electricity grid) rather than building its own. After all before coal could be used for transport you needed to build railways and coal ports, oil required its own infrastructure while the proposed renewables can simply be plugged into the grid which can then power transport (here I refer to public transport only, Cars are different) and such. Any improvements aside, the grid is already there and has been built, which saves a lot of time and resources. While their could easily be alternate forms of infrastructure, we don't know what they are and how to easily build them, that's something for the future.
Lets assume that the society is still unsustainable on the long run and further changes (after a gap of several decades) happen over 20-30 years (this could be because coal and gas have to be used to make up energy shortfalls from optimistic projections or some of the technology used cannot be made at that level of social complexity or internally). These changes could be to use more direct solar, in the Zero Carbon plan direct solar makes up a small amount of energy use, along with more direct use of wind and hydro/tidal for industry and home usage. So solar furnaces start being used, along with solar steam generators for sterilization or industrial heat production, small scale machine shops are powered by small rivers when possible or windmills, various factories (mills for grinding grain is traditional) are now directly powered by windmills and animals are being used again in certain areas for agricultural work and transport. This results in various things such as reduced production and again even lower imports and exports etc.
Now the society looks noticeably different from what we have now, but it doesn't look as different from the previous society and it evolved from our current society in two steps. And so on down the line until a stable eco-technic society arrives and climax community is reached, by that point the society could only have the most tenuous similarities to ours but it got their by gradual changing and going through many different stages on the way. Our current strategy shouldn't be to create a perfectly stable and self-sufficient renewable energy base right away, if that option ever existed its well gone, but to create the conditions and start walking down the path that will get us there with the least suffering and difficulty. That may involve stuff along the way that seems counter productive to the end goal, such as expanding the electric grid to allow viable large scale use of renewables, or an expansion of farmland, but that facilitates one or more stages. We need an overall meta-strategy on the century scale (basically a goal and a vague idea of what needs to be done) that tactics over the decades can be slotted into to eventually reach the undefined endpoint.
Now the process outlined above is the best case scenario, its likely to be far more difficult, ragged and a lot of it will be propelled by various short and long term crises. But it points out a few topics that need to be discussed and looked at. Infrastructure change and the meta-costs of technologies, the differing scales societies operate on, supporting technologies and how renewables could develop over the long term. These topics are incredibly important to understand how societies could change and adapt in the face of Overshoot. The main point though is that societies change over time in an organic way, they do not suddenly leap into new forms fully formed. People adapt, change behaviours or implement different technologies as they go, eventually the changes add up and you can say that the society has changed from one form to another. It is a process that mostly happens on a larger scale than individual human lives, through everyone contributes to it.
More on those topics next week.