Germany made its ambitious goal of basing the total final energy consumption on 60% renewable energy by 2050 official in 2010. The question is how is that going? While others, institutes like Fraunhofer or the German Ministry for Economics and Energy, can surely provide better in-depth analyses than I can here right now, I want to highlight one particular point. 

While in my parallel post ‘Carrying Capacity, Degrowth and Technology’, I deliver an argument for why technology cannot be the only solution to sustainability, here I make a point for a complementary statement saying that successful energy and sustainability transitions are and will be dependent on technological innovation to recognizable extents.

If you take a look at the electricity generation in Germany by type of fuel in figure 1 you can quickly see a transition happening: Nuclear is rapidly phasing out, coal is doing so more slowly and renewables come in as a substitute. As of 2016 renewables provide roughly 35% to the yearly electricity generation in Germany. That is electricity however. How about the total energy picture where a lot of other energized domains count as well, for instance heating or all kinds of transport?

]In the next picture you see the total primary energy supply in Germany and you see that conventionally used fuels are much less phasing out. Here I distinguished between solar, wind etc. and biofuels in order to demonstrate that there is some boost in biofuel and biowaste use, too. It does slightly substitute coal and oil use in energy generation. However, as you likely notice the other renewables remain small compared to fossil fuels. Even if you add both together, biofuel and other renewables, by far, you do not attain the same 35% contribution as in electricity only. The share of biofuel plus other renewables was barely 12% in 2015 (according to the German Environment Agency it was more than 13% in 2017; This pattern and large difference between electricity and energy generation is enough reason to believe that we are nowhere near obliterating fossil fuels.

But how come it works finely for the electricity branch but not for the rest? Well as said in the total energy balance sectors like transport are included. And in fact it is transport that with 26% (tendency increasing!) of the entire world energy consumption is very hard to decouple from fossil fuels. In a recent paper a whole bunch of American researchers argue for the same case They also point out that next to transport there are other processes that are just very hard to decouple from fossil fuels and thus carbon emissions as for example extreme-heat requiring industrial processes, but most importantly electricity grid balancing (in case the sun does not shine and the wind does not blow).

Yet I want to emphasize that the transport sector should not be underestimated, the consumption of cars and their use, the demand for flights and shipping is all increasing massively!

Unfortunately, there are fundamental engineering reasons on why transport for example is so hard to decouple from fossil fuels. Have a look at the next graph: It displays a parameter space of available means for energy storage. On the y-axis you see the volumetric energy density plotted and on the x-axis the gravimetric energy density. Energy density, no matter if volumetric or gravimetric, tells you something about how much energy you get out of a medium for whatever purpose. In the graph one can clearly identify different clusters. The green cluster are the traditional fossil fuels used such as Diesel, Kerosene and Coal. Notice all of them have a very high volumetric energy density that means the amount of Joule you get out per the amount of litre is high. This is why they are so convenient and yet superior in the transport market. (Almost) nothing else can compete with the low volume you need in order to overcome a certain distance. This is why, considering the low volume needed, you can fit them easily in relative small vehicles like cars. Let’s compare to hydrogen, located alone on the outright corner of the graph, which is the long hailed fuel of the future. In its raw form, as a car fuel it is less appropriate because even under high pressure it has a low volumetric energy density, meaning you need much larger tanks in order to provide the same amount of fuel as with conventional ones. As a rocket-fuel in space flight it works better because it has a very high gravimetric energy density, so it gives a light fuel, and you do not have to worry about the size of the tank so much. Rockets are large anyway.

Other groups you can spot are brownish (bio-based materials) and turquoise (electricity storages). Unfortunately you see why electric vehicles do not conquer the car market yet. Their energy density is low, both metrics considered. It requires large and heavy batteries in order to compensate for that and thus makes the whole car expensive, at least if you want to compete with the long-distance reach of conventional cars. I for example think the future of EV’s should be light weight, focused on urban areas, introducing lots of E-bicycles and other smaller vehicles. For short urban distances one does not need the energy density of Diesel. Anyway one also sees the biological brownish group which includes wood, methanol and ethanol. Notable is that one can also engineer these substances further, into Biodiesel, to make them almost as energy-dense as conventional fuel. This is why the only respectable contribution of alternative renewable sources to primary energy in Germany (and elsewhere) comes from biofuel.

In conclusion I write these articles mostly for fun and in order to learn about coding and visualization. And for hopefully creating useful data-sets. This is why here you can download the used Excel data and here the corresponding R script. However in content-wise conclusion, unfortunately the prevalence of fossil fuels is reducible to fundamental physical properties and together with the socio-economic outlook of what the world population demands and requires (growing transport needs, steady electricity, heating or cooling etc.), it will remain not only a social challenge but a technological one too, to decarbonize and turn sustainable. This is why, in my mind, engineers around the world are essential to find further solutions in order to boost electricity use in domains like transport and heavy industry and create convenient means for decarbonized but energy dense fuels.


The transition to a more decarbonized energy system can happen via substituting non-electricity energy by electricity. Since electricity is more easily decarbonized as visible from the pictures above. Increase electricity across sectors, decrease other energy means. This is actually already happening in Germany and, to be fair, should be recognized. However, as we have discussed some energy needs are just hard to electrify because of energy density reasons. Therefore there are likely practical limits to how much energy can be electrified.