fossil fuels are not going away

[emordnilap]

Agreed that we will burn the difficult ones, but I suspect the much more difficult ones will stay safely in the ground for centuries to come. They will never be exploited because we (industrial society) will never be able to spare the physical resources for the capital intensive development of these (at best) marginal resources.

Maybe. I'm not at present convinced. EROEI has always been irrelevant, if the end product makes the money.

Of course, we can and will burn enough coal to fry the planet, but that is another matter.

Oh, definitely.

[DominicJ]

Maybe. I'm not at present convinced. EROEI has always been irrelevant, if the end product makes the money.

Very true, at the end of the day, we burn 100 units coal in generating plants, send it across wires to houses, and end up with 60 units, if we're lucky.

[PS_RalphW]

Maybe. I'm not at present convinced. EROEI has always been irrelevant, if the end product makes the money.

Very true, at the end of the day, we burn 100 units coal in generating plants, send it across wires to houses, and end up with 60 units, if we're lucky.

Err, units of what? Not primary energy conversion , (25 - 35%) not transmission losses (80 - 90 %) .

I have never seen coal transmitted down a wire. This is a meaningless comment.

[DominicJ]

Fine.
We burn coal containing 100 units of energy in an electricity plant to transform it into electricity contain 60 units of energy.

Energy invested is less than energy returned.

[ujoni08]

I'm not sure, but I think the EROEI in this example should be comparing the energy invested in mining the coal, to the energy we get from it.
Then it's also about whether we have a choice. Even if there are massive losses in generation and transition, we have to take a hit, because we need the energy at the point of use, i.e. factories and homes, and don't have many easy options at this point. So yes, I think the EROEI is not the only factor in all cases, but must be one of them, along with demand, price, etc.
Or am I talking guano?

[emordnilap]

So yes, I think the EROEI is not the only factor in all cases, but must be one of them, along with demand, price, etc.
Or am I talking guano?

No, you're not.

EROEI only ultimately matters when we start getting up to a planetary scale. In economics, it's largely irrelevant once the profit is there.

If someone burns X number of barrels of oil, Y cubic metres of gas and Z tons of coal and turns something you're prepared to buy from them and give them the profit they want, then that's what they'll do.

In the meantime, the planet is frying, as RalphW points out.

[clv101]

Fine.
We burn coal containing 100 units of energy in an electricity plant to transform it into electricity contain 60 units of energy.

Energy invested is less than energy returned.

60% efficient coal to electricity? That's going some! The best IGCC plants are only around 50% efficient, and that's before any transmission. In the UK 100 units of energy in coal is transformed into 36 units of electrical energy (DUKES 5.10).

[DominicJ]

ah yes, 60% is lost, not 60% generated

[Standuble]

I'm a bit of a noob but wouldn't the efficiency of output energy (retrieved energy divided to previously contained energy) be irrelevant in the context of EROEI? I thought EROEI would only apply in regards to the output energy in relation to the input energy. They wouldn't care if they were only getting 40% of the energy from the total amount in the coal if they were only using half that amount of energy in the initial reaction to extract that energy. They would care if they knew an energy source would consistently be a net loss with no way to bring it back.

Feel free to correct me if I've made a cock up.

[RenewableCandy]

The 40% you mention is one of the factors that go to make the EROEI. It's multiplied by, for instance, (energy spent mining/chemical energy in resulting coal). Wonder whether they take into account the energy content of the moners' meals (for example)? And so on...

[vtsnowedin]

The 40% you mention is one of the factors that go to make the EROEI. It's multiplied by, for instance, (energy spent mining/chemical energy in resulting coal). Wonder whether they take into account the energy content of the moners' meals (for example)? And so on...

The energy content of the miners meals would be covered by the wages paid to them if you computed your EROEI in dollars or other currency. So to the energy used to build the mining machinery and the fuel to run it whether just a power shovel and truck or a deep water drilling platform. Add it all up then divide by the value of the oil or coal sold. Worked the other way and the total costs will give you the minimum price you can sell the resultant energy for.

[ceti331]

Fine.
We burn coal containing 100 units of energy in an electricity plant to transform it into electricity contain 60 units of energy.

Energy invested is less than energy returned.

i think EROEI refers to resource extraction /raw energy generation only.

Coal->electricity->end user is like comparing raw joules in food to Joules expended by your hands and feet.

Along the scale energy is turned into information. electricity is generated because it can perform more varied tasks than coal. (similarly food can allow your hands to perform more varied tasks).

perhaps when economics is working right, profit measures how efficiently energy is being turned into information?

in the coal electricity example you'd have to compare the power station to delivering coal and having mini coal-powered electricity generation in peoples homes (the energy required to build lots of small devices)


Interestingly I've heard of people trying to make fuel cells for natural-gas -> electricity which might save transmission losses ? (i usually balk when i hear 'fuel cell' because i think of people being tricked into thinking hydrogen is an energy source..)

[PS_RalphW]

Laptop makers have experimented with methanol/ NG fuel cells in stead of batteries. The theory is that the fuel canisters are less heavy to cart around than extra batteries. However, most laptops are owned by people with ubiquitous access to mains electricity for recharging, so the idea has not taken off, and airport security gets very grumpy if you start carrying chemical canisters onto aircraft these days.

[kenneal - lagger]

According to some chap called Chris Vernon and others in "Fleeing Vesuvius" once EROEI gets below 5 the energy return is not great enough to allow a society to function for long. The energy profit isn't enough to generate enough income to keep the society going at the levels that it is used to and decline starts.

Tar sands, with an EROEI of about 5, are subsidised by natural gas deposits which can't realistically be used anywhere else. Once that natural gas runs out the cost of building a nuclear power station or burning some of the oil produced to get more oil will mean that the return lowers and the tars sands will not generate enough energy profit to keep us going.

Society can't run without an energy profit greater than 5 overall because there isn't enough of a return, once societies inefficiencies and requirements are taken into account, to make it worthwhile extracting that energy source.

[SleeperService]

The same Chris Vernon also mentions a 13 to 1 ratio between energy expended to point of use. There's a link somewhere to a recent lecture that specifically mentions this.

And here I am at 02:21

Edit: Link in this thread can't remember how far along it is though

http://www.powerswitch.org.uk/forum/vie ... hp?t=19848