3 ms·

Thanks for the detailed response! If you're talking about an EROEI on wind of 18, and a 20% storage efficiency, that brings down the EROEI to 3.6. Probably mor

Thanks for the detailed response! If you're talking about an EROEI on wind of 18, and a 20% storage efficiency, that brings down the EROEI to 3.6. Probably more, as not all energy will pass through the storage. Still well below replacement. Or is that already factored into the EROEI? Does that include the unmetered power usage of windmills? If so: how? Does that factor in increased power-line losses, and the cost of building and maintaining those power lines? What are the details of the windmills measured? Is that real-world data, or simulations? If real-world, where? I agree that current foodstuffs are not suitable for biodiesel. And raises food prices. But two things. One, I was talking about synthetic production. And two, that's assuming current plants. Personally, we shouldn't be looking at land-based solutions anyways. We already have space issues, at least at that scale. Look at sea-based ideas instead. Algae farming on megascales, that sort of thing. Much more efficient, much more land available, and can be situated closer to the equator. I knew I shouldn't have just said "rare-earths and the like". I am aware that rare earths are a misnomer in general. Although... Neodymium isn't rare, but the bulk of the world's production thereof is in China. Has that energy cost been factored in? Much less the other costs? (Amount of radioactive release, etc.) > As for synfuels: since you're converting surplus generating capacity, your marginal energy cost is nil. Wrong. Your marginal energy cost is the cost of building and maintaining the plant and supporting infrastructure. And even just that may be less than unity overall. It may be useful, but I'd want to see the numbers. As for the trade you mention ("Even assuming you're building capacity specific to the need, what you're trading is a non-storable, non-mobile, non-dispatchable form of energy for one which has all of those properties"), I agree partly, but the question remains: what energy input should we use? Is it worth it to build wind generators or solar power stations? Should we stick to nuclear? Or what? Fundamentally, we currently have a couple of different energy sources. Geothermal, direct solar, indirect solar (wind, hydro), tidal, "biological solar", nuclear energy, and potentially fusion. Everything else is just energy storage. (Well, to be pedantic, so is fission and fusion, but by the time we're worrying about those running out we'll have worse issues.) Current biological solar solutions are not exactly efficient. Your figures show direct solar isn't either. Wind is iffy for various reasons - maybe not insurmountable, but still. Geothermal is great, but only in limited areas. Same with hydro and tidal. Nuclear is great, but the political climate is rather iffy to put it mildly.

dredmorbius 12y ago
Taking a look at the full-cycle EROEI is something I'd like to do, but haven't. It's not necessary for any given element of a power cycle to be EROEI-positive. In fact any given energy transform will represent a net energy loss. But for the total effective cycle you've got to get more than you give. Note that at present agriculture in the US represents a 10:1 energy cost -- you get 1 unit of energy for every ten units of fossil-fuel energy you input. In Europe it's about a 1:5 ratio. Again, negative EROEI. The saving grace is that fossil fuel energy has such a high EROEI. On marginal cost of energy: if the alternative is to discard the generating potential entirely, then the marginal cost is zero. If you're building excess capacity specifically to provide fuel synthesis capabilities, you do have real costs. The US Naval Research Lab's estimate is $3-6/gallon for aviation fuel, though I'm not sure if they assume a gratis reactor. I've specced out $9/gallon with solar input. Not cheap, but a long-term stable price, vs. constantly rising fossil fuel costs. As for input energy: my assumption is generally for solar + wind -- they're simply the largest available long-term sustainable energy sources we've got (I've got my doubts on how long nuclear fuel will last, and terrestrial fusion's still unproven). The initial scheme for large-scale F-T synthesis was based on a presumption of nuclear energy input. M. King Hubbert proposed this in 1964, and the idea was picked up by Meyer Steinberg of BNL pretty much immediately. The initial proposal was that CO2 come from, e.g., limestone, but seawater was identified as a reservoir pretty early on. Steinberg's a nuclear engineer, and most of his work assumes nuclear power supplying electricity. Incidentally: in a nuclear economy, you'd still need liquid fuels, though most proposals focus on hydrogen alone. Given difficulties with its chemistry, I doubt this will prove effective. Compared with alternatives, I really see solar as the backbone of any future energy system. The only questions are how large the supported population will be, and how advanced its technology. Solar energy is what humans relied on before finding fossil fuels. And there's no assurance that we'll retain our present tech levels. Nuclear's problems are not merely political, though that's a significant hurdle of its own.

dredmorbius 12y ago

Taking a look at the full-cycle EROEI is something I'd like to do, but haven't. It's not necessary for any given element of a power cycle to be EROEI-positive. In fact any given energy transform will represent a net energy loss. But for the total effective cycle you've got to get more than you give. Note that at present agriculture in the US represents a 10:1 energy cost -- you get 1 unit of energy for every ten units of fossil-fuel energy you input. In Europe it's about a 1:5 ratio. Again, negative EROEI. The saving grace is that fossil fuel energy has such a high EROEI. On marginal cost of energy: if the alternative is to discard the generating potential entirely, then the marginal cost is zero. If you're building excess capacity specifically to provide fuel synthesis capabilities, you do have real costs. The US Naval Research Lab's estimate is $3-6/gallon for aviation fuel, though I'm not sure if they assume a gratis reactor. I've specced out $9/gallon with solar input. Not cheap, but a long-term stable price, vs. constantly rising fossil fuel costs. As for input energy: my assumption is generally for solar + wind -- they're simply the largest available long-term sustainable energy sources we've got (I've got my doubts on how long nuclear fuel will last, and terrestrial fusion's still unproven). The initial scheme for large-scale F-T synthesis was based on a presumption of nuclear energy input. M. King Hubbert proposed this in 1964, and the idea was picked up by Meyer Steinberg of BNL pretty much immediately. The initial proposal was that CO2 come from, e.g., limestone, but seawater was identified as a reservoir pretty early on. Steinberg's a nuclear engineer, and most of his work assumes nuclear power supplying electricity. Incidentally: in a nuclear economy, you'd still need liquid fuels, though most proposals focus on hydrogen alone. Given difficulties with its chemistry, I doubt this will prove effective. Compared with alternatives, I really see solar as the backbone of any future energy system. The only questions are how large the supported population will be, and how advanced its technology. Solar energy is what humans relied on before finding fossil fuels. And there's no assurance that we'll retain our present tech levels. Nuclear's problems are not merely political, though that's a significant hurdle of its own.