2012-08-14 Regarding 'Solar Energy in the Context of Energy Use'

The late Professor David MacKay, FRS submitted to the Royal Society the paper: 'Solar Energy in the context of energy use, energy transportation, and energy storage',

I received an advance copy and was invited to comment on it.

He took no account of the thermodynamic minimum energies required for the various tasks, or of energy quality. These show the scope for energy savings, both absolutely and by cascading reject heat from one process to another end-use (as in CHP). When considering the power and energy densities of wind power, he based them on the gross area of the wind farm, rather than the net area of the towers etc, say 100 x smaller. Also, while he mentioned offshore wind, he still related the power demands to national land areas. Moreover, he omitted consideration of floating wind turbines, even though prototypes were already in operation. In the UK case, these could harness wind power over most of the Exclusive Economic Zone, with an area over three times that of the land. He also made no mention of renewable synthetic fuels for long-term energy storage. Yet Power-to-Gas processes were already being demonstrated at several plants in Germany of up to multi-MW scale.

The published version of MacKay's paper is: 2013-07-01, 'Solar energy in the context of energy use, energy transportation and energy storage'

This now mentions energy saving, referencing the work of Jochen et al, but not the 'thermodynamic minima' for end-uses.

It now considers balancing variable solar power with storable products, including 'Gasoline from air', with the electricity required coming from nuclear power and on- and offshore wind farms. However, while noting the low overall efficiency, he does not mention the possibility of cascading process losses to meet the demand for heat. He mentions the possibility of continued use of fossil fuels (with CCS), and of nuclear fuel. Yet he fails to acknowledge that these are unsustainable (being depletable), unaffordable (from experience) and with the potential for major disasters.

It is indeed fortunate for all life-forms that savings and renewables offer humankind 100% sustainable energy solutions. This has been shown by many modelling studies, including those carried out in Germany. (See: 'Electricity from Wind and Storage', Slide 6).


2012-08-14 Regarding 'Solar Energy in the Context of Energy Use'
The late Professor David MacKay, FRS submitted to the Royal Society the paper: 'Solar Energy in the context of energy use, energy transportation, and energy storage',