EU and BP Renewable Electricity Accounting Methodologies

Every EU country has a renewable energy target to be met by 2020 where the target is set as a percentage of gross final energy consumption. Since most countries are using combinations of hydro, solar and wind electricity (primary electricity) to achieve their targets, one needs a way of comparing primary electricity with energy from coal, oil and gas etc. The standard way adopted by the EU and by BP is to convert all forms of energy to tonnes of oil equivalent (toe). If coal, oil or gas is used to make electricity then there are large thermal losses doing so. BP account for this by grossing up renewable electricity by a factor of 100/38 (2.63) to account for “thermal gain” when converting from primary electricity to a fossil fuel equivalent. The EU does not do this, hence the toe figures reported by the EU and BP differ. Which methodology is correct?

In September last year, Roger Andrews had a post called EU Renewable Energy Targets: The Compliance Statistics are Suspect which raised a number of interesting issues without getting to the root of the problem. I decided to follow up with a more detailed analysis and quickly wished I hadn’t since I had to venture into the chaotic world of Eurostat – the EU energy statistics portal. Click a link in Eurostat with the expectation of learning something and you will be disappointed in a link merry-go-round. But every now and then you may get lucky and actually find some data.

If you get really lucky you stumble upon SHARES where it is possible to actually download a spreadsheet with RE data from 2004 to 2014 (note that I still don’t know how to find this page through the Eurostat portal and only came upon it by chance on Google with some help from Roger). But then compare this data with BP and you will find there is no semblance of similarity between the data sets as illustrated for hydroelectric power (Figure 1). One of the data sets is clearly wrong, but which one? Solar and wind data show the same discrepancy.

Figure 1 Hydroelectric power for EU28 as reported by BP 2015 and by the EU in SHARES. How can the two sources of data be so different? And which is correct?

The answer lies in how primary electricity (hydro, solar, wind etc) is normalised to the common datum of tonnes oil equivalent (toe).

BP give the following conversion factor:

1 toe = 12 MWh of electricity

If we take BP’s figure for EU28 hydroelectric production in 2014 of 370.3 TWh and convert using the above factor we get:

370.3 TWh / 12 MWh = 30.9 Mtoe

But if we then check what BP report on their Mtoe tab we find that they report 83.8 Mtoe for EU28 hydro in 2014 compared with 30.0 Mtoe reported by SHARES, which is the answer one gets converting using 12 MWh / toe (see above). At face value it appears that BP have made a mistake.

Its easier to think of this problem going in the other direction from fuel to electricity. Let us imagine that instead of normalising to toe that all energy was normalised to TWh instead. If we were to take our tonne of oil and burn it somehow in a generator we know that a large portion of the energy it contained will be lost as waste heat. We will not get our 12 MWh of electricity. We may get something closer to 4.6 MWh instead assuming 38% efficiency. Now, if we had 4.6 MWh of hydroelectric power that has no thermal losses associated with its production, we would need to gross that up by 100/38 if we were to compare it to oil or oil equivalents to account for thermal gain going in the opposite direction. And this is exactly what BP do noting at the foot of every spreadsheet the following:

 * Based on gross primary hydroelectric generation and not accounting for cross-border electricity supply.  Converted on the basis of thermal equivalence assuming 38%.

So let’s see if we correct the EU SHARES figures in this way if we resolve the issue (Figures 2, 3 and 4).

Figure 2 Hydroelectric power for EU28 expressed as toe. BP already gross up production for “thermal gain” going from primary electricity to fossil fuel equivalent using a factor of 100/38. Applying the same correction to the Eurostat SHARES data brings the BP and EU data into line.

Figure 3 See caption to Figure 2. Applying the same correction to solar provides a very close alignment between the BP and EUR data.

Figure 4 See caption to Figure 2. Applying the same correction to wind provides a close alignment between the BP and EUR data.

From Figures 2, 3 and 4 it should be clear that grossing the EU SHARES data up by 100/38 resolves the discrepancy between the two data sets. We can conclude this with a high degree of certainty. It is less certain whether the EU data should be adjusted up or the BP data adjusted down. I have been convinced in the past that BPs methodology was correct but based on opinions from experienced reviewers I am now undecided. This, therefore is a topic open for debate.

Concluding Comments

There are compelling reasons for wanting to compare the amounts of energy produced from different sources but this is a technical and philosophical challenge and the rules need to be clearly set out.  The Eurostat SHARES page says this:

The use of renewable energy sources is seen as a key element in energy policy, reducing the dependence on fuel imported from non-EU countries, reducing emissions from fossil fuel sources, and decoupling energy costs from oil prices. Directive 2009/28/EC on promotion of the use of energy from renewable sources established accounting criteria for the 2020 targets on renewable energy sources.

Directing us to Directive 2009/28/EC that has 97 clauses, 29 Articles and 7 annexes we find the rule for normalising hydroelectric and wind power in Annexe II:

This is opaque as mud and while I have not close read the whole directive I cannot see reference to how one should convert from primary electricity to a fossil fuel equivalent. In a vast ocean of blether the vital information is either lost or missing.

If one adopts the BP methodology then EU primary electricity production may actually be much higher than everyone thinks and needs to be increased by a factor of 2.63 when expressed as toe.

Footnote

The consequences of these findings are potentially far reaching and one point merits further investigation and that is this conversion factor from BP:

toe = 12 MWh of electricity

If that has built in conversion losses in power stations then it would be BP that was at fault. And so some further checking is in order this time using conversion factors from The World Energy Council. I want to check this conversion using thermal units.

1 toe = 10.03 Gcal

1 KWh = 860 Kcal

hence 1 toe = 10.03 cal^9 / 860 cal^3 = 11.7 MWh

BP are correctly using thermal equivalence. The question is, should imaginary thermal losses be factored into converting from one imaginary toe of hydro electric power to electricity?

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53 Responses to EU and BP Renewable Electricity Accounting Methodologies

  1. Euan Mearns says:

    Readers please note that I edited this post at the last minute from a position where I was convinced that BP are correct to one where I now have doubts.

    If I take one TOE of hydroelectric power and convert it to electricity in this virtual world of normalisation then I need to imagine there will be thermal losses going from oil to electricity and I will produce something like 4.6 MWh of electricity. Its impossible to generate 12 MWh from a tonne of oil equivalent.

    Note that I am travelling this week until Thursday and will only have occasional internet access. Roger is also travelling Monday.

    • Stuart Brown says:

      Euan, I think this is the latest version of the Directive though I can’t tell you what differences there are
      http://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX:02009L0028-20151005

      I also think you’re right that we’re talking about primary energy here.

      Article2, sec f says “gross final consumption of energy’ means the energy commodities delivered for energy purposes to industry, transport, households, services including public services, agriculture, forestry and fisheries, including the consumption of electricity and heat by the energy branch for electricity and heat production and including losses of electricity and heat in distribution and transmission”

      To me that says the energy used plus the energy involved in transposing it into the desired form plus the energy consumed in delivering it. Thanks for putting me straight!

    • Willem Post says:

      Euan,

      For conversion from delivered energy to the grid to primary energy dug from mines and pumped from wells, the USDOE uses about 1.0 for hydro and nuclear, about 2.83 for fossil, which I think is the correct approach.

  2. roberthargraves says:

    The objective of reducing CO2 emissions has been warped into renewable energy accounting fog. Does non-CO2-emitting nuclear power count as a renewable? If the EU objective is to reduce CO2 emissions, why not measure them? It’s pretty straightforward to measure fuel consumption and compute CO2 emitted at each power plant, for example.

    • jim brough says:

      Robert,
      The renewable energy accounting fog has been around for many years.
      I agree.
      CO2 emissions per kwh of electricity generation have been known for many years and nuclear is the lowest.
      What people forget is that you can not make solar cells, wind turbines or any other electricity generation technology without CO2 emissions.
      An ad in a glossy mag described Australia’s first carbon neutral brick. My polite enquiry about the accounting was never answered.

  3. Peter Lang says:

    Robert Hargraves,

    It is not straightforward to measure CO2 emissions. These are the US EPA requirements for measuring emission from fossil fuel power stations that emit more than a specified amount of CO2 per year: https://www.epa.gov/airmarkets/emissions-monitoring

    However, the regulations for monitoring emissions (not just CO2) have been changing every few years for decades. The cost of upgrading the systems is a very high compliance cost.

    The EU does estimate emissions from each power plant.

  4. Clive Best says:

    Is it really fair to convert each fuel to just electrical energy? Obviously renewables like wind and solar just produce electrical energy but modern life depends on 3 main energy streams.

    1. Transport
    2. Domestic heating
    4. Electrical power

    In the UK these are all about the same size. Transport depends on oil and heating depends mainly on gas. So even if current electricity was made 100% renewable it would do nothing to reduce transport and heating. Once you convert electrical energy to move cars or produce heat you lose efficiency again, whereas oil and gas net efficiency would increase relative to electricity generation.

    • matthew_ says:

      Good point Clive. Converting oil and gas to electricity and then using electricity to supply Transport and Domestic heating services can give a higher efficiency than if the oil and gas were used directly to supply Transport and Heat services. In that case the BP thermal to el adjustment factor for electric power stations would not be correct since el allows a more efficient use of the fuel to supply the basic service needed.

      In case someone is in doubt about the higher effieciency, here is an example.
      Consider two alternatives:
      1. One toe of gas is burned in a central furnace with 98% efficiency to supply space heating in a home.
      2. One toe of gas is burned in combined cycle gas turbine (at 50% efficiency to el) to produce electricity which is then used to drive a heat pump (300% efficiency pumping heat) supplying space heating in a home.

      Alternative two gives over 50% more home heat per toe compared to alt. one. Are both options considered equal in the calculations of the EU directive? Would converting a country from alternative 1 to alternative 2 give an improved score? It would certainly reduce the countries fuel consumption.
      Muddy indeed.

      • Greg Kaan says:

        Matthew, you are ignoring transmission losses which are normally estimated to be in the order of 30%. This loss then equalises the heat supplied in your 2 alternatives.

        The renewables advocates are almost universal in making this same assumption (a “copper plate” transmission network) when discussing distributed generation.

        I feel Clive is correct in his assessment of the BP normalisation – by assuming that electricity is the form of energy that is most valuable, the BP figures bias energy assessments in favour of renewable electricity generation. Of course it then places renewable liquid fuels, such as biodiesel and ethanol, at a similar disadvantage to fossil fuels.

        • Andy Dawson says:

          “Matthew, you are ignoring transmission losses which are normally estimated to be in the order of 30%”

          Where?

          they’re certainly nothing like that in the UK; they’re typically 2-2.5% in the National Grid – see table 1 in the following:

          http://www.poyry.co.uk/sites/www.poyry.uk/files/ZonalAverageLossesInGB.pdf

          Note the figures for generation in Northern Scotland – 600km+ from heavy load in the South of England.

          • Greg Kaan says:

            Those are TLMs are modelled adjustment factors for transmission across zones. Note how some adjustments are positive.

            The IEA and World Bank has 7-8% losses for the UK
            http://www.indexmundi.com/facts/indicators/EG.ELC.LOSS.ZS/map/europe

            http://data.worldbank.org/indicator/EG.ELC.LOSS.ZS

            But these figures are based on the end point power charges – my university lecturers warned of larger losses at actual consumption. 30% may be too large for a compact grid like the UK but 2.5% is not realisitic either

          • Andy Dawson says:

            Greg,

            Read you own link:

            “…Electric power transmission and distribution losses include losses in transmission between sources of supply and points of distribution and in the distribution to consumers, including pilferage..”.

            In other words – ALL losses – Transmission, distribution, “abstraction”, reactive, unmetered, meter error…..Those are very different from Transmission losses.

            As to the actual level of transmission loss

            https://www.elexon.co.uk/wp-content/uploads/2013/11/transmission_losses_v4.0_cgi.pdf

            (Elexon is the body responsible for running all balancing and settlements on the GB grid)

            “…When transferring power across the Transmission System, some of the power is ‘lost’. This lost power
            is known as Transmission Losses and currently accounts for about 2% of the electricity transmitted….”

            I think you need to talk to your lecturers…

        • Willem Post says:

          Greg,

          US transmission losses are about 6.5% of production fed to grids.

          In rural areas, such as Vermont, the transmission and distribution losses are about 9%.

        • robertok06 says:

          “Matthew, you are ignoring transmission losses which are normally estimated to be in the order of 30%. ”

          No way!… transmission losses of western countries in Europe amount to less than 10%… where did you get your number from?
          Please explain.

          • Greg Kaan says:

            My apologies – my memory is failable and the lecture was many years ago. Nevertheless the subject being discussed was the difference in heating efficiency between heat pumps vs bar radiators vs local fossil fuel heaters.

            The advantage of heat pumps (we refer to them as reverse cycle airconditioners and used a heating efficiency of 400%) over local fossil fuels was far less than 50%. The end to end efficiency of the bar radiator may have been 30% allowing for low efficiency coal generators.

      • Stuart Brown says:

        Since I was just looking at it I offer you Annex VII:
        “ANNEX VII

        Accounting of energy from heat pumps

        The amount of aerothermal, geothermal or hydrothermal energy captured by heat pumps to be considered energy from renewable sources for the purposes of this Directive, ERES , shall be calculated in accordance with the following formula:

        ERES = Qusable * (1 – 1/SPF)

        where

        Qusable = the estimated total usable heat delivered by heat pumps fulfilling the criteria referred to in Article 5(4), implemented as follows: Only heat pumps for which SPF > 1,15 * 1/η shall be taken into account,


        SPF = the estimated average seasonal performance factor for those heat pumps,


        η is the ratio between total gross production of electricity and the primary energy consumption for electricity production and shall be calculated as an EU average based on Eurostat data.

        By 1 January 2013, the Commission shall establish guidelines on how Member States are to estimate the values of Qusable and SPF for the different heat pump technologies and applications, taking into consideration differences in climatic conditions, especially very cold climates.”

        Off to see if the commission did issue anything by Jan 1, ’13. Mud, mud, glorious mud…

        • matthew_ says:

          Thank you Stuart.
          Then using the two alternatives for heating with gas described above, and excluding both 10% electric grid losses, and 5% gas grid losses.
          1. Heat used is 1 toe (thermal), which requires 1.02 toe of gas (primary energy) with 0% RES.
          2. Heat used is 1 toe (thermal), which requires 0.33 toe of el, which requires 0.66 toe of gas (primary energy). In addition there is the ERES supplied by the heat pump of 1*(1-1/3), or 0.66 toe of renewable primary energy. Total primary energy consumption is then 1.33 toe and 50% RES.

          Converting to heat pumps gives a better RES percentage, but also increases primary energy consumption.

    • gweberbv says:

      Clive,

      I am missing heat generation for industrial/chemical processes. This fourth stream is also important.

      For space heating one can simply declare that heat pumps should be the standard. Then you generate typically 3 to 4 kWh heat from 1 kWh electricity input. In the end this is roughly equivalent to normalizing the direct electricity production by the thermal loss factor.

      • gweberbv says:

        P.S. Using for fossil fuels for transport is not significantly more efficient than burning the fuel to generate electricity and then use electricity to move the car.
        Let’s check the numbers: The average car may consume 7 liters gasoline per 100 km. 1 liter of gasoline has a heating energy of roughly 8 kWh, so we consume roughly 60 kWh of primary energy to move the car 100 km. The Nissan Leaf consumes less than 20 kWh/100 km. Again a factor of roughly 1/3.

        We conclude: For space heating and private car transport the assumption is correct that 1 kWh of electricity that is used to generate heat or to move a car would replace roughly 3 kWh of primary energy from fossil fuels.

        • robertok06 says:

          What’s missing in all these comments on primary energy vs final, or electricity equivalent is the fact that it is important to consider the emissions from the different sources and also the country where a particular source is used.
          Example: PV made in China and used in Germany is one thing, PV made in France and used in Germany is another thing, finally PV made in China and installed in France is another thing as well. Primary energy and kWh of electricity are the same, the effects on the amount of CO2 emissions and the effect on the health of the citizens of China, France and Germany is another one.

          • Beamspot says:

            I think there are more factors to take into account.

            PV is 15% efficient at converting light to electricity.

            Solar thermal for heating is in the 60 – 70% efficient to do the same.

            So, why don’t invest into hot tap water and solar space heating instead of electricity?

            In China, solar water heating if two orders of magnitude higher (in MWh) than PV. But it seems Green Dreamers forget this always, sistematically. Why?

            Perhaps because electricity is easy to meter and control while heating not?

  5. singletonengineer says:

    Thanks for this discussion. I was vaguely aware that the concept of emissions intensity is a slippery one, in part because it is used to compare:
    1. Countries’ performance (“…5% reduction nationally between 1995 and 2005…”),
    2. In relation to GDP (“… so many tonnes of CO2-e per unit of GDP)
    3. Per capita (“… X tonnes of CO2-e emissions per person per annum…”)
    and more, including raw CO2 Vs CO2-e.

    Why not use the Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories, coupled with some kind of agreed comparison factors for non-electrical energy consumption?

    Possible reasons: BP and EU reporting probably predate IPCC and to change measurement methodologies would make year-on-year comparisons difficult.

    You have opened my eyes to a huge gap in my knowledge.This article and its predecessor were eye-openers for me, because I had been sheltered from all except the carbon intensity measure which is part and parcel of the IPCC NGGI guidelines, which I am far too lazy to digest. Here’s hoping that somebody has already done so and will clear this up for us all.

    See also: https://en.wikipedia.org/wiki/Emission_intensity.

  6. Euan mearns says:

    I think this discussion is one step removed from co2 emissions intensity. The focus here is on the simpler concept of energy use and how it should be normalised.

  7. On a point of clarification. The EU bases its RE percentage estimates on “gross final consumption”, which it defines as follows (From Directive 2009/28/EC of the European Parliament):

    ‘gross final consumption of energy’ means the energy commodities delivered for energy purposes to industry, transport, households, services including public services, agriculture, forestry and fisheries, including the consumption of electricity and heat by the energy branch for electricity and heat production and including losses of electricity and heat in distribution and transmission

    This definition includes distribution and transmission losses but apparently not power lost in generation. The operative word, I think, is “delivered”.

    • Stuart Brown says:

      Roger – Euan referred to primary energy in his last post and I queried it with him yesterday. He believed that primary energy and ‘gross final energy’ are the same thing, and on reading the quote I agree with him, as per my comment above. Surely:

      “including the consumption of electricity and heat by the energy branch for electricity and heat production”

      … includes the consumption of heat to make electricity?

      Or have I still got this wrong? There were a couple of commentators at the start of the last thread that seemed to believe they were different too.

    • Euan Mearns says:

      Roger, as you see I got cold feet after a second opinion from another expert. But I still think I am correct in siding with BP, especially in light of what you say here. If the definition does not include power lost in generation then normalising everything to TWh will result in FF being significantly downgraded (as opposed to primary electricity being upgraded) and the end result will be the same as determined by BP.

      TOE is a virtual world. A fantasy world. But it is quite simply not possible to convert a TOE of FF to electricity without incurring significant losses. The EU believing they can convert a TOE to 12 MWh electricity is IMO plain wrong. But for 5 minutes earlier today I believed the EU may be correct.

      From CDG Paris 🙂 Left Aberdeen in blizzard 🙁

      • Gentlemen: Please note that I never said the EU’s definition was right.

        I’m going to do some additional work on this to try to formulate a position, but it won’t be today.

        • Stuart Brown says:

          Guys, after a frustrating few hours yesterday I hope you’ll indulge one last comment from me, then I’m going to shut up.

          I couldn’t find an equivalence like TOE anywhere in the EU morass apart from this:
          http://ec.europa.eu/eurostat/cache/metadata/en/nrg_10_esms.htm
          “Key principles of constructing the energy balance

          The energy balances (also called energy balance sheets) are expressed in thousands of tonnes of oil equivalent (ktoe) or terajoules (TJ). The tonne of oil equivalent is a standardized energy unit defined as a net calorific value of 107 kilocalories (41 868 MJ), which is roughly the net energy equivalent of a tonne of crude oil.

          The energy balances are compiled according to Eurostat’s methodology, which is based on the physical energy content method. The general principle of this method is that the primary energy form should be the first energy form in the production process for which various energy uses are practiced. For directly combustible energy products (for example coal, crude oil, natural gas, biomass, waste) it is their energy content. For products that are not directly combustible, the application of this principle leads to the choice of heat as the primary energy form for nuclear, geothermal and solar thermal; and to the choice of electricity as the primary energy form for solar photovoltaic, wind, hydro, tide, wave, ocean.

          In case the amount of heat produced in the nuclear reactor is not known, the primary energy equivalent is calculated from the electricity generation by assuming an efficiency of 33%. In case of electricity and heat generated with geothermal energy, if the actual amount of geothermal heat is not known, the primary energy equivalent is calculated assuming an efficiency of 10% for electricity production and 50% for derived heat production.”

          That at least answers Joe Public’s comment elsewhere but doesn’t mention ‘gross final consumption of energy’ so leaves me none the wiser.

          I think we are chasing a chimera. The EU wants reporting on both the energy inputs and outputs for all sorts of industry as above, and any equivalence is hidden in their spreadsheets as you said last year, Roger. It may even differ by country.

      • robertok06 says:

        “Left Aberdeen in blizzard ”

        Welcome to the global warming era, Euan! 🙂

  8. Andy Dawson says:

    Greg,

    7-8% is a (high) estimate for ALL UK losses from station gate to consumer – Transmission, Distribution, Power factor/reactive, unmetered, meter errors and what’s politely called “abstraction” (theft to we less politically correct types). And it’s a hell of lot less than 30%.

    The transmission losses are indeed in the 2-2.5% range

    Note:

    https://www.elexon.co.uk/wp-content/uploads/2013/11/transmission_losses_v4.0_cgi.pdf

    “When transferring power across the Transmission System, some of the power is ‘lost’. This lost power
    is known as Transmission Losses and currently accounts for about 2% of the electricity transmitted.”

    As to

    “– my university lecturers warned of larger losses at actual consumption. ”

    I’ve no idea what that’s supposed to mean!

    • gweberbv says:

      Alex,

      maybe the lecturer was thinking of AC/DC converters for powering a lot of consumer electronics, lights, etc.

    • Greg Kaan says:

      Andy

      Read you own link:

      “The UK Transmission System is a high voltage electricity network. The network transfers energy from Transmission connected Power Stations to Distribution Networks. These Distribution Networks then transfer energy to our homes and businesses”

      “When transferring power across the Transmission System, some of the power is ‘lost’. This lost power is known as Transmission Losses and currently accounts for about 2% of the electricity transmitted.”

      • Andy Dawson says:

        Greg,

        Shall we discuss the difference between transmission, distribution and the related losses?

        And then you can explain which don’t apply in “distributed generation”?

        In case you’d not worked it out, you’ve rather just made my point. Transmission is the HV system that ruins (in UK parlance) from station gate to grid supply point (GSP). It runs at at least 132kV, and almost entirely at 275/400). And bugger all power is lost in it.

        Then you’ve Distribution at kV, down to 415V. Where more losses occur. Which is the level at which distributed generation is embedded.

        Then you’ve got all the other losses. Things like pilferage are significant in some developing countries (I recall seeing illegal tappings from an 11kV line in Kylesha township in South Africa), but not in developed countries.

        I’m sorry if you don’t grasp power systems terminology, but that’s an issue for your to take up with your teachers, not here.

        • Greg Kaan says:

          So you choose to ignore the local distribution losses for legitimate consumption as trivial and see all losses beyond the HV transmission network as pilferage? You have said yourself that there are more losses at the distribution level and if the IEA see UK transmission efficiency in the 7-8% range, are you saying that 6% of electricity generated in the UK is stolen?

          What does distributed generation have to do with the current discussion? The comment made was about end to end efficiency from a baseload generator (CCGT) to an end user heat pump.

          I apologised for my memory lapse above – university was a long time ago – but your 2-2.5% is far from correct, too.

          • Andy Dawson says:

            Oh, ffs…

            Let’s go over this very, very slowly…..

            Power is generated at the station. It’s stepped up and sent into the TRANSMISSION system. Transmission had a specific meaning – moving power at very high voltages over significant distances. In the UK, and most developed countries, losses are 2-3%, and UK voltages are 132kV, 275kV, and 400kV.

            It’s then stepped down at a grid supply point into a medium-low voltage DISTRIBUTION system. That’s 33kV down to 415 (3 phase) / 240v. Losses there are another couple of percent (usually a little more than is lost in transmission)

            The delta between the sum of the two and the 7-8% is down to the other losses (reactive, un metered, abstraction etc.)

            Is that clear enough?

            I mentioned distributed generation because you’d raised the issue in you original post up-thread. And because there will be distribution losses in ANY system unless you go for completely isolated households etc.

  9. Joe Public says:

    The objective being to calculate / estimate / guess CO2 savings, the water is even muddier; than above commenters have concluded when converting the heat quantities of gas to ‘oil-equivalent’.

    1. Which grade of oil is taken for reference calorific value? There is a spread of ~17.7% between kerosene and heavy fuel oil. The latter would (probably) be burnt is a power station, the former in a home.

    2. The grade of oil selected as the heat-quantity reference affects the CO2 emissions calculation. However, whichever oil grade is selected, the CO2 emissions from Natural Gas will be significantly lower.

    e.g. Emis­sions in kgCO2 / kWh: Nat Gas ~0.2; Fuel Oil ~0.28 – an approx 40% spread

    http://www.volker-quaschning.de/datserv/CO2-spez/index_e.php

    Consequently, Nat Gas can (possibly/probably) generate more useful heat per unit of CO2 than BP/EU gives credit, if the units are ‘toe’, unless their caveats account for the above two factors, which are cumulative.

  10. The 38% efficiency of converting oil to electricity has long been the standard for diesel engines as against 27% for petrol engines and turbines. However, engines to vary in efficiency.
    Large diesel engines are not usually in electricity produced per tonne of fuel (Mwh/t), but the reciprocal of g/kwh. 38% efficiency equates to 217g/kwh – though this is mechanical, not electrical energy. There will also be losses in the alternator. Modern 4-stroke diesel engines of 5-20MW as used in cruise liners and diesel power stations are rated at about 175g/kwh. That would imply about 20% losses on converting the mechanical to electrical energy.
    Whilst we need a standard to compare the CO2 impact of replacing fossil with renewables, it can only be an rough estimate, with reality varying quite widely from that estimate.
    That said, I believe the correct standard is to gross up the oil figure by 100/38. What is relevant is the equivalent oil required to output a given quantity of electricity compared to that outputted from a an alternative energy source. It makes costs per unit of electricity to the end user comparable.

  11. Euan Mearns says:

    Three slides sent by and posted on behalf of Pedro Prieto:

  12. Peter Lang says:

    Euan,

    BP account for this by grossing up renewable electricity by a factor of 100/38 (2.63) to account for “thermal gain” when converting from primary electricity to a fossil fuel equivalent. The EU does not do this, hence the toe figures reported by the EU and BP differ. Which methodology is correct?

    Here are my thoughts on this, for what it’s worth:

    This issues was the subject of much debate many years ago and I understood it had reached closure. I understand IEA is the most widely accepted official data.

    I gave up trying to use the BP energy statistics long ago because:

    1. The issue you raise here was discussed to death long ago and I understood the consensus was that the IEA method should be used (I understand BP sticks to its method because of it is of most interest to the oil industry and because of the issue of changing the legacy data and systems that are widely used by many people and organisations)

    2. ‘toe’ is not an SI unit and is more difficult to work with, as are all imperial units

    3. Over time, electricity will provide an increasing proportion of global energy supply, so I prefer to calculate the amount of primary energy needed to supply 1 unit of electricity, not convert electricity to toe

    4. The conversion factors for converting from primary energy to electricity vary widely; e.g.
    • CCGT = 60%
    • OCGT = 40%
    • Brown Coal = 20% – 25%
    • Black coal = 35%
    • USC black = 45%
    • Nuclear LWR = 33%
    • Nuclear HTR = ?
    • Solar thermal = ?
    • Geothermal = ?
    • Biomass = ?

    Lastly, this recent (March 2016) presentation by Daniel Weißbach on EROEI presents an example of one reason to not convert electricity to oil equivalent (I suggest there are many other reasons too). He says:

    • Strict exergy concept: Heat output of power plant ignored. Exergy versatile for all processes (also heating)
    • No output weighting: Do not weight the electrical output – otherwise it is no EROI anymore.
    • No input weighting: Weighting factors are market factors (price for electricity ~ 3x price for heat) with physical background (efficiency of turbines η ~ 1/3) that might change.
    • Transparency: Separate listing of exergy and heat input. So it can be easily compared with EROIs calculated by other methodologies.

    http://science-and-energy.org/wp-content/uploads/2016/03/EROI_LesHouches2016.pdf

    • Euan Mearns says:

      Peter, can you point me to the IEA web page or spread sheet where I can download all global energy statistics for the last 50 years?

      I have no problem with converting all fuels to electricity equivalent. But this means that BP are right and the EU wrong since the latter don’t account for thermal losses.

      • Peter Lang says:

        Euan,

        That seems like a rather “cute” dismissive type of comment/question. What do you mean by “all energy statistics”?

        I’ve never gone looking for “all global energy statistics for the last 50 years”. However, you and Roger have far more access and better capabilities to get data you want than I do. I was a bit surprised you had apparently not research IEA and the previous debates on this subject for your post.

        I don’t agree with your last sentence, see my previous comment on this.

  13. Peter Lang says:

    Euan,

    I meant IEA not EIA. IEA is the International Energy Agency. Here is the link to the statistics: http://www.iea.org/statistics/

    I don’t have a link to hand where the methodologies are explained. The debate about the issues your post is tackling went on for years, but that was long ago.

    I do recall that IEA made a change to their presentation of ‘electricity and heat’ somewhere around 2010 to 2014. It was explained in one (or more) of the pdf documents linked on the right side of the above link. Most likely either “Energy Prices and Taxes” and/or “CO2 emissions from fuel combustion”.

    Here is a chart of world total electricity generation by fuel 1971-2013: http://www.iea.org/stats/WebGraphs/WORLD2.pdf You can get the data from here: http://www.iea.org/statistics/statisticssearch/ You can also select the country or region or multiple countries. You can also select other criteria such as coal, gas, oil, renewables, balances, etc and select final energy consumption or total primary energy consumption.

    The SI unit for comparing energy is J, PJ, EJ, etc. TWh is a unit used by the electricity industry globally, but admittedly becoming more widely used. TWh and GWy as appropriate are widely understood.

    • Rui Rosa says:

      I understand that neither BP nor EU are correct. To be closer to physical reality.one should convert all amounts of energy to exergy at the source. In simple terms, electrical and mechanical energy are pure exergy; thermal energy can be converted into exergy by Carnot’s factor (T-To)/To; chemical energy of a given fuel can be assessed by its Gibbs potential, wich represents the maximum amount of energy possibly released or extracted in bringing the fuel into equilibrium with the reference environment (CO2 and H2O, temperature and pressure), Notice that a fuel can be burnt to be converted into thermal energy and next this into work or electricity; but alternatively in can be burnt in a fuel cell to directly release electrical energy. Whatever the path to “liberate/obtain” the final energy we use, the exergy at the source is the common measure; but the efficiency and losses are different, one might have a much higher efficiency when avoiding the thermal energy path.
      The factor applied by BP to electrical energy directly extracted from wind and sunlight is the reciprocal of Carnot’s factor, it leads to a more accurate comparison with fossil fuels (as used in thermal power plants). But would not be useful in case fuels were burned in fuel cells to deliver electricity.
      So that these comparisons may be misleading – and may not protrait the technically changing reality. In any case, exergy would offer sounder ground for comparison.

      • singletonengineer says:

        Good luck with exergy.

        The term has been around for about 60 years. You will probably need another 40 to convince the other players to play the game by your rules.

        • Rui Rosa says:

          It is OK with Exergy. The concept, under the name of Availability was first addressed in mid XIX century and became widely used in early XIX century. Theorem of Gouy-Stodola is a classical. The “new” term Exergy is the same consept. Bibliography on exergy, exergy analysis, exergy efficiency, etc. is widely used in Applied Thermodynamics. No need to convince anyone. But many people can be mislead by taking energy quantity at face value – when not caring about energy quality- exergy being an useful quantity to minimize that shortcoming.
          The conversion factors for converting from primary energy to electricity – as reported by Peter Lang – address that problem of energy “quality” but still in an incomplete and ad-hoc way.
          Clivebest offered the approach by David Mackay. I am convinced that for the time being that is thes best option, to reject conversion factors, in which case the EU statistics offer a clearer picture – on could say according to the First Principle of Thermodynamics.
          I here express deep regret for the loss of David Mackay – an inspiring and influencial academic..

  14. clivebest says:

    David Mackay, who sadly died 2 weeks ago, clarifies this energy accounting problem brilliantly in Sustainable Energy without the hot air. It is worth quoting what he wrote.

    The electrical energy produced by a wind turbine is of no use to
    a petrol engine; and petrol is no use if you want to power a television.
    In principle, energy can be converted from one form to another, though
    conversion entails losses. Fossil-fuel power stations, for example, guzzle
    chemical energy and produce electricity (with an efficiency of 40% or so).
    And aluminium plants guzzle electrical energy to create a product with
    high chemical energy – aluminium (with an efficiency of 30% or so).

    In some summaries of energy production and consumption, all the dif-
    ferent forms of energy are put into the same units, but multipliers are
    introduced, rating electrical energy from hydroelectricity for example as
    being worth 2.5 times more than the chemical energy in oil. This bumping
    up of electricity’s effective energy value can be justified by saying, “well,
    1 kWh of electricity is equivalent to 2.5 kWh of oil, because if we put that
    much oil into a standard power station it would deliver 40% of 2.5 kWh,
    which is 1 kWh of electricity.” In this book, however, I will usually use a
    one-to-one conversion rate when comparing different forms of energy. It
    is not the case that 2.5 kWh of oil is inescapably equivalent to 1 kWh of
    electricity; that just happens to be the perceived exchange rate in a world-
    view where oil is used to make electricity. Yes, conversion of chemical
    energy to electrical energy is done with this particular inefficient exchange
    rate. But electrical energy can also be converted to chemical energy. In an
    alternative world (perhaps not far-off) with relatively plentiful electricity
    and little oil, we might use electricity to make liquid fuels; in that world
    we would surely not use the same exchange rate – each kWh of gasoline
    would then cost us something like 3 kWh of electricity! I think the timeless
    and scientific way to summarize and compare energies is to hold 1 kWh
    of chemical energy equivalent to 1 kWh of electricity. My choice to use
    this one-to-one conversion rate means that some of my sums will look a
    bit different from other people’s. (For example, BP’s Statistical Review of
    World Energy rates 1 kWh of electricity as equivalent to 100/38 ≈ 2.6 kWh
    of oil; on the other hand, the government’s Digest of UK Energy Statistics
    uses the same one-to-one conversion rate as me.) And I emphasize again,
    this choice does not imply that I’m suggesting you could convert either
    form of energy directly into the other. Converting chemical energy into
    electrical energy always wastes energy, and so does converting electrical
    into chemical energy.

    So using tonnes of oil equivalent is an arbitrary choice which is electricity centric.

    • clivebest says:

      Here is the text from David MacKay formatted properly – I hope !

      The electrical energy produced by a wind turbine is of no use to a petrol engine; and petrol is no use if you want to power a television. In principle, energy can be converted from one form to another, though conversion entails losses. Fossil-fuel power stations, for example, guzzle chemical energy and produce electricity (with an efficiency of 40% or so). And aluminium plants guzzle electrical energy to create a product with high chemical energy – aluminium (with an efficiency of 30% or so).

      In some summaries of energy production and consumption, all the different forms of energy are put into the same units, but multipliers are introduced, rating electrical energy from hydroelectricity for example as being worth 2.5 times more than the chemical energy in oil. This bumping up of electricity’s effective energy value can be justified by saying, “well, 1 kWh of electricity is equivalent to 2.5 kWh of oil, because if we put that much oil into a standard power station it would deliver 40% of 2.5 kWh, which is 1 kWh of electricity.” In this book, however, I will usually use a one-to-one conversion rate when comparing different forms of energy. It is not the case that 2.5 kWh of oil is inescapably equivalent to 1 kWh of electricity; that just happens to be the perceived exchange rate in a world-view where oil is used to make electricity. Yes, conversion of chemical energy to electrical energy is done with this particular inefficient exchange rate. But electrical energy can also be converted to chemical energy. In an alternative world (perhaps not far-off) with relatively plentiful electricity and little oil, we might use electricity to make liquid fuels; in that world we would surely not use the same exchange rate – each kWh of gasoline would then cost us something like 3 kWh of electricity! I think the timeless and scientific way to summarize and compare energies is to hold 1 kWh of chemical energy equivalent to 1 kWh of electricity. My choice to use this one-to-one conversion rate means that some of my sums will look a bit different from other people’s. (For example, BP’s Statistical Review of World Energy rates 1 kWh of electricity as equivalent to 100/38 ≈ 2.6 kWh of oil; on the other hand, the government’s Digest of UK Energy Statistics uses the same one-to-one conversion rate as me.) And I emphasize again, this choice does not imply that I’m suggesting you could convert either form of energy directly into the other. Converting chemical energy into electrical energy always wastes energy, and so does converting electrical into chemical energy.

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