There are many smart engineers on LinkedIn, which is evident from the content of posts. Right now, many of those posts are about the energy transition. There is enough technology out there to keep any geek happy for millennia. However, there is something missing from the discussions, a fundamental understanding of energy systems and energy chains. This week I am mostly thinking about the fundamentals of energy systems. I do not have much choice; it is the first week of my MSc module ‘Introduction to Energy Policy’. I have to admit it has given me pause for thought. A real head-scratcher. I have also come to think that anyone involved in advocating technology for energy transition should take the time to do an ‘Energy Primer’. I have a few reflections that I thought I might share.

You will not be surprised to hear that in the very broadest sense GDP (wealth) correlates reasonably well with energy use. No surprise that since 1800, the industrial revolution, and what has followed, is accompanied by a rapid increase in the consumption of primary energy. But not all countries are created equally. Japan and the USA have very similar GDP growth, but Japan has used a lot less energy than the USA. It seems for whatever reason, culturally, Japan is just more energy efficient than the USA.

What you might not know, is that the world has been decarbonizing its energy since 1850 from about 115 KgCO2/GJ in 1850 to 70 KgCO/GJ in 2010. So if that is true, why the rush to decarbonize? The problem is that the global rate of decarbonization has been about 0.3% annually, about six times too low to offset the increase in global energy use of some 2%. We are decarbonizing slower than we are increasing energy usage. Despite gains in carbon efficiency, total carbon emissions have gone up. This fact points to the conclusion that energy efficiency is a problem in equal measure to carbon-based primary fuels.

Now here is the kicker. The carbon crisis means we are moving towards renewable energy. Good, right? Well maybe good, maybe bad. This energy transition is coming at the expense of the quality of the energy. What do I mean by quality, surely renewable energy is better quality. Well true, it is cleaner, but renewable energy has lower quality. It all comes down to energy density. The problem is oil, gas, and coal packs a hell of a punch when it comes to energy density, and renewables just cannot beat that. Look at it this way, wind and solar energy use the instantaneous wind and sun available today. By contrast, a single seam of coal represents thousands to millions of years of the sun shining to create carbon material via photosynthesis, not to mention the millennia of geological-mechanical energy required to squash all that organic matter into a concentrated form (coal). It is the same for oil and gas.

We can normalize primary energy sources and compare them as energy density Watts per m2

  • Coal mine 5000 W/m2
  • Coal-fired electrical generation station 500 W/m2
  • Solar PV 5-20 W/m2
  • Wind 2.5 W/m2
  • Biomass 0.5 W/m2

If you think about these numbers, you begin to realize that as you move towards carbon-free renewables, you will need a lot more stuff and a lot more space to generate this lower-quality energy. To put it into context, you will need about twenty thousand wind turbines to supply enough electricity to electrify all of the cars in the United Kingdom. This number is for just cars, not all transport. You can build more giant turbines, but bigger turbines need to be more space, so you do not win on footprint with more giant windmills. The other quality problem is that wind and solar, unlike coal, oil, and gas are not easily storable. We can easily store oil and its products. But wind and solar need to be converted to a convenient carrier and stored. There was a reason coal was used to peak shave high demand, that is because it is storable and the supply of electricity from coal can be turned up and down in reasonably short order. Gas is even more flexible.

‘Why are you worried about price? Is you customer performance or price sensitive?’You cannot have your cake and eat it if you want to move towards renewables, there needs to be a big increase in energy efficiency because there is going to be a decrease in the ‘quality’ of the energy.

So the move toward renewable puts energy efficiency at the center of the relationship between economics and energy systems. There is something called the first-law efficiency (from Nakicenovic, see references below). Efficiency is defined as the ratio of the desired (usable) energy output to the energy input. You have to think about the full chain of energy from source to consumption. You have to map all of the conversion losses along the route that the energy conversion takes. For example for electric vehicles, you have to think about wind turbines, electrical transmission, charging batteries, and then discharging the battery to convert back to electrical to drive the motor and mechanical energy to drive the car forward. You have to be careful in your consideration of the energy carrier. For example, if you use Hydrogen, as a carrier the efficiency ratio changes. So for green hydrogen, you have the chain, Wind turbine, electrical energy, electrolyzer, the chemical energy of hydrogen, conversion of hydrogen back to electrical energy via a fuel cell, to driving a motor and mechanical energy to drive the car forward. Both are clean forms of energy, but they have very different efficiencies. Wind to Wheel, the energy efficiency for Electrical Vehicles is about 75%. For Hydrogen as a carrier, it is about 35%.

So why does efficiency matter, because in the move to renewables we will have to accept a dramatic drop in the quality of the energy. This means we will have a lot less energy to play with and we are going to have to get a lot more efficient in our usage. It is not good enough to talk only in terms of cost, convenience, and cleanness. Any energy system we put in place, inclusive of the source, conversion, carriers, and use, will have to get a lot more efficient.

My observations are that:

We have to be ruthless in selecting the most efficient energy systems; and
We need to spend much, much, more on energy efficiency. For example, improving heat retention in our homes, reducing our reliance on personal transport, finding the most efficient overall energy systems, and so on.

Funky geekery and shiny new tech are great, but we need to do the basics in thinking about and delivering more efficient energy systems. We need to be careful that we do not spend all our pocket money on fun stuff with lower overall efficiency.

ERRATUM 14th Feb 2021:

Further works assuming the largest wind turbines suggest electrification of EVS can be achieved with 3000 wind turbines, and not 20,000 as reported here.

How many wind turbines to save the world? (

Further Reading

This article is not intended to be a treatise, but to encourage people to do some deeper think and maybe a little research. Here is some suggested further reading:

Grubler, A., T. B. Johansson, L. Mundaca, N. Nakicenovic, S. Pachauri, K. Riahi, H.-H. Rogner and L. Strupeit, 2012: Chapter 1 – Energy Primer. In Global Energy Assessment – Toward a Sustainable Future, Cambridge University Press, Cambridge, UK and New York, NY, USA and the International Institute for Applied Systems Analysis, Laxenburg, Austria, pp. 99-150.

Sustainable energy – without the hot air. David MacKay. David MacKay FRS: : Contents (

David Cebon, Author at The Centre For Sustainable Road Freight (

Energy Cycle Efficiency in Vehicles- Does the EV Really Win? | LinkedIn

So: Exactly How Much Electricity Does it Take To Produce A Gallon of Gasoline? | LinkedIn

Nakicenovic , N , P. V. Gilliand R. Kurz , 1996a : Regional and global exergy and energy efficiencies. Energy , 21 (3): 223 – 237.

Nakicenovic , N. , A. Grubler , H. Ishitani , T. Johansson , G. Marland , J. R. Moreira and H.-H. Rogner , 1996b : Energy primer. In Climate Change 1995 – Impacts, Adaptations and Mitigation of Climate Change: Scientific-Technical Analyses, Contribution of Working Group II to the Second Assessment Report of the Intergovernmental Panel on Climate Change . R. T. Watson , M. C. Zinyowera and R. H. Moss (eds.), Cambridge University Press , Cambridge, UK , pp.75–92.

Rosen , M. A.and I. Dincer , 2007 : Exergy: Energy, Environment, and Sustainable Development . Elsevier , Amsterdam, The Netherlands.

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