Part I – How much energy do we actually use?

One think that frequently worries me as far as the whole “energy debate” is concerned is the general lack of understanding by some poeple as regards how much energy we use and what we use it for. Many get distracted by electricity thinking it is all that matters. However, in most western countries electricity accounts for only about 10-25% of primary energy supply. So yes, even if we can get to 100% of that with renewables (or 85% with nuclear as the French have done) where does the other 90-75% of the energy come from?

Then there’s the thorny issue of how this energy is consumed. Much of this energy is consumed in the form of heat generation, transportation fuels and industrial process inputs. We might be able to run trains on electricity (from wind farms or nuclear plants depending on your point of view) but what about planes? And all the electricity in the world will not provide petroleum based feedstock for a pharmaceuticals plant. To use alternatives to fossil fuels in these processes some sort of “transition medium” or “transition fuel” is needed and that means going through several stages of energy conversions and hence reduced efficiency and poorer economics. Thus in order to provide a definitive answer to the question where does our future energy come from? We need to first ask how much energy do we use? And what do we use it for?

Lies, damn lies, statistics and energy statistics

I will now attempt to answer these questions. There are many suppositions about energy and how much is used and in what form. The true picture may surprise many people, not least because the energy picture has altered radically in the last decade due to the explosive growth in Asia. The numbers I will use below come from the following sources, principle the IEA’s (International Energy Agency) Key world Energy Statistics Report 2009 and 2010. Other sources include the EIA, the World yearbook: Energy Data and the energy textbook Energy by Aubrecht.

I would make a cautionary note from the start, the study period for these figures is (2007-2009) during which the world was going through a severe economic downturn, which severely depressed energy usage levels, notably those of fossil fuels, in particular oil. Thus its probable that once the world recovers from its current woes that energy consumption will rise (again fossil fuels in particular). The figures for the post-recession period can be found here.

One source of confusion when picking ones way through energy statistics, is the different energy units used in energy stats and reports: BTU’s, kWh’s/person/day, tWh, GW/yr, millions tons of oil (mtoe), barrels of oil (bbl), barrels of oil a day (bbl/day), short tons of coal (stc), cubic feet of natural gas (cfg), billion cubic metres of gas (bcm), etc. My personal favourite is the EIA’s quadrillion BTU’s (who nobody outside of the EIA seems to have a clue as to what it means…..thought I wonder if that’s deliberate!). To simplify things I’ve converted everything above into kWh’s (that’s 1kW used over an hour period i.e 3.6 million Joules of energy = 1 kWh), thought I may be forced to use other units here and there. Of course, given the scale of the numbers considered, I’ll largely be forced to use Trillion kWh/yr i.e 1e12 kWh/yr.

Biomass…or not?

The total global energy output figure you arrive at also depends on whether you include Biomass or not. Many international energy experts tend to treat biomass somewhat like they’d treat a dead cat (ignore it), as the bulk of this figure represents firewood burnt in rural parts of developing countries (i.e. fuel that was gathered with no profit going to multinational energy companies) and which is not necessarily being extracted at a sustainable rate (so thus it should not really be looked on as a “renewable” energy source).

Other forms of biomass include landfill waste combustion, which is only “sustainable” if people keep throwing away stuff that can otherwise be recycled (and much of the energy inputs here come from other sources, principally fossil fuels so there is a risk of double counting). Even the “true” renewable forms of biomass, such as ethanol and other biofuels have bit of a big question mark over them. After one accounts for the energy expended in their production (often in the form of fossil fuels) the claim that they are low carbon and infinitely renewable is put into doubt. Consequently many analysts simply leave biomass off their charts altogether, but I’ve included it below, as it does represent a critical energy source we’ll need to either maintain or replace with something else at some point. It’s also probably better to risk a slight over estimate (given what was said before about the recession) than be left with an energy shortfall in the future.

A Nuclear Question 

You will note that some sources will quote a figure for nuclear power in the order of 712 mtoe (approximately 8.9 trillion kWh/yr) and 2,731 billion kWh/yr. Indeed the IEA gives both these figures in the space of a few pages. What gives? This is where the issue of inefficiency we’ll be discussing later kicks in, as well as the concept of TPES (Total Primary Energy Supply) against TPC (Total Primary Consumption). The first figure above (712 mtoe) represents the total energy generated by nuclear plants. But much of this is wasted through inefficiency or because the plants are running at times when the power isn’t needed (and essentially gets thrown away). The second figure 2.7 trillon kWh/yr represents the TPC, how much of this generated energy actually makes it onto the grid. Of course this factor applies to other energy sources too, but the descrepency is most notable when it comes to nuclear power.

Production v’s Consumption

As a result of the points made aboveI’ve broken the graph down into three sets of figures, one with biomass included, a second with biomass excluded, both representing TPES. Thirdly I’ve tried to estimate the TPC (i.e. the “output” energy) from fossil fuels using average efficiency rates and deducting the amounts consumed in industrial processes. As fossil fuels are consumed with an average 25-50% efficiency this reduces the final total energy consumption figures as shown in the final column (in brackets), as compared to the primary consumption figures given (and the percentages in the first two columns). We aren’t of course assuming 100% efficiency for nuclear or hydro (in the first column), it’s just that “tWh” figures given by the IEA ignore the efficiency of these sources as the fuel is either free, or (in the case of nuclear) only a fraction of the overall costs, as compared to fossil fuels where fuel costs often represents the bulk of the final operating costs. There is probably a margin of error of around 4-5% in all of these numbers due to frequent conversion of units from one form to another, plus the fact I’m using multiple sources of data.

Global total primary energy consumption 2010 report

As regards the last column of percentages, I would urge caution not to read too much into these figures, as again, the numbers give in brackets for fossil fuels are merely to get around the problem of allowing us to compare like for like (i.e fossil fuels at typical efficiency v’s renewables and nuclear sources on a level playing field). In many cases we still need to use the higher figure in the first kWh/yr column in terms of planning how we replace them.

A couple of things immediately jump out at you looking at the chart above, its interesting to note that more energy comes from cooking fires (biomass) in the developing world than all the world’s nuclear plants, dams, wind, solar and geothermal sources combined! Current “completely renewable” (i.e PV geothermal & wind, etc.) output is tiny but growing fast. One notable difference between the 2008 and 2010 report is that renewable production has grown significantly since then. It has jumped from 527 billion kWh to 1.1 Trillion kWh per year (roughly 85 mtoe) in late 2009 a near doubling in just over 2 years. Even so it’s a long way to go. However, the key point I’m trying to get across is the size of the mountain we’ve got to climb. Arguing where in the foothills renewables are currently having a brew is going slightly off topic (nuclear are a little further up the mountain but seem to have come down with a bad case of HACE since Fukushima).

Buried in the text of these reports I’ve linked to (pg 44 of the IEA 2010 study), is an acknowledgement that carbon emissions have risen from 15.6 Billion tons of CO2 in 1973 to 29.4 Billion tons of CO2 in 2008, a near doubling in just 35 years. This rapid rise in carbon emissions and the increasing alarm it is causing among environmentalists is completely understandable.

Consumption paths

As I stated at the outset it’s important not just to define how much energy we use, but equally how it is consumed. Globally for example electricity accounts for roughly 20.2 Trillion kWh’s or 1,614 mtoe, or about 14% of the primary energy supply or 17.2% (pg 28, IEA 2010) once we neglect non-energy users of fossil fuels, plus losses in refining and processing.

Breaking down the consumption pathways towards the end (pg 33 onwards of IEA 2010) we see that 61.4% of oil (2150 mtoe), 5.9% of gas (77.46 mtoe) and 0.4% of coal (3.2 mtoe) is used for transport, suggesting that 2230.8 mtoe of our final supply (8,428 mtoe, from IEA, 2010) or 26.4% is used for transport purposes. Heating would probably be of a similar level (thought at a global level it’s hard to come up with an exact figure but a general 40% in colder climates to 25% in warmer climate would be normal). This would suggest in our obsession with electricity and fears over “the lights going out” we’re ignoring the bigger issues of transport fuel, almost all of which comes from oil, and heat production, almost all of which comes from natural gas and coal.

About daryan12

Engineer, expertise: Energy, Sustainablity, Computer Aided Engineering, Renewables technology
This entry was posted in climate change, economics, energy, nuclear, peak oil, politics, power, renewables, sustainability, sustainable, Uncategorized. Bookmark the permalink.

8 Responses to Part I – How much energy do we actually use?

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