shortonsense wrote:culicomorpha wrote:Now I don't know how much energy it takes to make the array, but I would be willing to bet my life it is a lot less than 65.7GWh. That is to say, the EROEI is absolutely > 1
Really? I would say you have done a fantastic calculation, blazing through your calculation with the efficiency of undoubtedly a fine engineering background and years of experience.
Except....I didn't see the calculation for the actual feedstock of energy going into this system....why not?
Certainly I did consider the input energy.....it is, after all, required to make the 500 megawatts I referred to. I have no objection to megawatt hours, I was abbreviating for my own sake, but I tend to be literal, so if others catch me out for not being specific I say hats off to them. So hats off to you.
To create the 65.7 GW/h you calculated we need to consider the energy input and some rough estimate of efficiency, as well as what you focused on, which was simply building the array. Ignoring the array ( it being a minor part of the system ) I simply considered all relevant energy input, rather than counting only a small one such as the array. After all, while our local solar furnance might provide quite a bit of free energy, its contribution is still required to make nearly everything on this planet work properly.
Assuming we are operating at 20% efficiency ( sunlight to on site power, and yes, we can argue specifics but I don't believe such precision is required based on the engineering obviousness of the argument I am making ), the energy input to create the 65.7 GW/h ( can we just call it 1.21 JIGGA WATTS!! in our best Chrisopher Lloyd voice?
) would be on the order of 328.5 GW/h, so the real question is, how in the world was such an AWFUL system ever invented, considering the horrible nature of the EROEI? If it had been a peaker which invented this, they would never have filed with the patent office, the idea being so hideous!
Oh, for goodness sakes.
I’ll clarify this for the sake of other people reading this forum, but you so misunderstand energy and power concepts that I would strongly suggest that other readers either check shortonsense’s math themselves or ask someone else who does know how to do these calculations.
OK, EROEI is energy returned (or output produced - in this case, by the Sun) divided by the energy input (or the energy required to build the array. Mathematically speaking,: EROEI = Eout/Ein
Output energy, as I calculated above, is around 65GWh, and this figure already includes the efficiency of the array.
Input energy required to produce the array includes mining all the materials: glass, silver for the mirrors, copper for the plumbing, etc etc. All these inputs require energy in mining, transportation, manufacturing, and in assembly and maintenance (human energy - i.e. food). And that food has energy inputs as well, so from a practical matter, it is quite complicated to actually determine the true energy cost of producing the array.
Let’s be exceedingly generous, and say that we used 1GWh to produce the array. That’s a SWAG, but my intuition is that this is a very high figure. This is roughly equivalent to the annual electric consumption for 70 million US homes, based on average household electric consumption for
2007, as reported by the EIANow that we have estimates for the output energy and the input energy, we can calculate the EROEI:
EROEI = Eout/Ein = 65.7GWh/1GWh = 65.7
This is obviously greater than 1.
FWIW, I would strongly suggest you pay more attention to your dimensional units. Concepts of power and energy are easy to confuse, and if you get sloppy with your units, you can make silly mistakes – as you did above.
Confusion of watts, watt-hours, and watts per hour Terms such as watts per hour are often misused.[8] Watts per hour properly refers to the change of power per hour. Watts per hour (W/h) might be useful to characterize the ramp-up behavior of power plants. For example, a power plant that reaches a power output of 1 MW from 0 MW in 15 minutes has a ramp-up rate of 4 MW/h.