The days of power generation at location X and material manufacture at location Y are numbered…

Energy is never „lost“: it can only change form, and if we can re-capture it before it diffuses into the surroundings, then we can minimize the loss: we can use the energy given off by one process to (partly, or completely) drive another one. A very basic example is the low-pressure, but still quite hot, steam from a power station, which can be fed via insulated pipes to residential areas for heating.

Making e-fuel production more efficient…

Another example would be a wind generator running fairly constantly in a windy part of the world. Directly on-site would be an electrolyser, making green hydrogen from water. The heat generated from this reaction would feed into the machinery for capturing CO2 from the air, which requires the absorptive filters to be heated to around 85 oC to release the CO2. Further heat could be used partly to power the fans and compressors of this plant. Energy losses would, hence, be reduced by integration.

Integration brings flexibility between energy and crucial materials…

But there’s more than just efficiency to be gained by integration: also flexibility. Integration is key to the diversification and success of biology. The cells with the largest evolutionary diversity are so-called „eukaryotic“ ones. They contain tiny machines (mitochondria) that initially burn carbon-containing energy-carriers (fats and sugars) to make electricity. This is almost immediately converted into biologically useful chemical energy (ATP), and materials for the rest of the cell. Similarly, human economies use carbon in a massive variety of products. The biological cell can easily reverse most of this biochemistry, and make energy from carbon-based substances. Plant cells basically make all of the biological energy and materials that support the rest of life on Earth, and the chloroplasts in plant basically split water — initially releasing hydrogen — just like electrolyzers that humans build.

Chemical synthesis plants that do very similar interconversions to cells have already been built. They rely on the concept of reversibility between energy-carrying chemicals and electrical energy: basically they „catalytically burn“ chemicals — in an analogous way to cells in all living organisms — to generate electricity, and use electricity to make chemicals out of raw ingredients. In so doing, they can easily constitute a single facility that serves energy storage, electricity re-regeneration and production of feedstocks for the chemical industry.

Methanol and methane: Examples of e-fuels frequently discussed…

Two very important energy-carriers and chemical feedstocks are methanol and methane. These are immediate products from well-established chemical synthesis reactions (Fischer-Tropsch, and Sabatier, respectively). Hence, we can construct facilities where, for example, methanol and methane are…

> produced with abundant natural energy on-site, with energy capture and use in other processes (see below);
> stored in quantities sufficient to even out energy troughs, particularly large seasonal ones;
> used by chemical plants on-site to make usfeul substances, with energy capture feeding back to increase efficiency;
> transported for use as portable fuel in transport sector;
> piped or transported to other users, e.g. steel/cement industry;
> used in reverse to generate electricity at times of need to feed directly into the grid.

Further reading:

> Microalgae as model system demonstrating energy/material transitions between chloroplasts and mitochondria
> Reversible Solid-Oxide Cell Stack for generating fuel from electricity, and electricity from fuel

Copyright Andrew Moore 2024