4 ms·

I always wondered if some sort of "closed loop fuel" model was viable. The appeal of conventional fossil fuels are high energy density and well established tec

by hakfoo 4y ago

I always wondered if some sort of "closed loop fuel" model was viable. The appeal of conventional fossil fuels are high energy density and well established tech to convert it back to useful energy. What if we had a station with some tens of thousands of litres of petrol sitting around. When the grid is strained, we burn the fuel, but in a generator carefully engineered to capture all waste. When renewables exceed demand, we use the available cheap energy to distill the waste back into burnable petrol. Now, obviously "petrol" and "generator" can be replaced with other options to optimize performance or economic viability (maybe it's hydrogen and a fuel-cell rather than petrol and a generator, but I'm not sure if those are actually working at scale or just trotted out by Toyota to distract from them being late to the EV party) It probably wouldn't be hugely efficient (the distilling would consume more energy than burning ever generated, after all), but it could be a way to handle "I'll pay you tomorrow for a hamburger today" with more flexibility on siting than, say, pumped hydro. I suppose the big question is how tight the closed-loop can be. It's not a winner if you end up losing 1% of your fuel stash on every daily cycle.

Manuel_D 4y ago
Essentially you're proposing capturing the CO2 emitted by fossil fuel heat engines and converting it back to hydrocarbons using the Sabatier process. There's several barriers to this: 1. Capturing the carbon emissions. The exhaust if a gas turbine is a high temperature mix of air and C02. Separating out the CO2 requires either cooling it or a chemical process to capture the carbon dioxide. Both of these processes are every energy intensive. 2. The Sabatier process needs a source of hydrogen. Typically this is done through steam reformation, but that emits CO2. Electrolysis or thermochemical water splitting needs to be done instead, and these are both energy intensive and expensive to do. 3. The Sabatier process itself also requires energy, as it's putting the carbon in a higher energy state. It'd probably be easier to just use the hydrogen in step 2, but that's still a difficult undertaking that nobody has done cost effectively as of now.

by hakfoo 4y ago

Manuel_D 4y ago

Essentially you're proposing capturing the CO2 emitted by fossil fuel heat engines and converting it back to hydrocarbons using the Sabatier process. There's several barriers to this: 1. Capturing the carbon emissions. The exhaust if a gas turbine is a high temperature mix of air and C02. Separating out the CO2 requires either cooling it or a chemical process to capture the carbon dioxide. Both of these processes are every energy intensive. 2. The Sabatier process needs a source of hydrogen. Typically this is done through steam reformation, but that emits CO2. Electrolysis or thermochemical water splitting needs to be done instead, and these are both energy intensive and expensive to do. 3. The Sabatier process itself also requires energy, as it's putting the carbon in a higher energy state. It'd probably be easier to just use the hydrogen in step 2, but that's still a difficult undertaking that nobody has done cost effectively as of now.