Solar power

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mulad
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Solar power

Postby mulad » July 30th, 2013, 11:08 am

Over on the Minneapolis Energy Municipalization thread, solar power has been brought up a few times as being not yet ready for prime time. Does anyone have a good source for further details on that? I guess I've been watching solar prices drop precipitously and figuring that it made sense at this point to begin moving into it quite a bit.

I've been interested in solar for around a decade now, and I've felt that it made sense for a long time particularly since it doesn't require much land in comparison to things like biofuels from crops (ethanol, biodiesel, etc.) and even wind (where the land below can still be used for crops or whatever, but turbines need to be spaced out a lot).

I'll have to re-run the numbers at some point because I never logged the inputs in great detail, but back in 2007 I estimated that a square mile of corn could only power about 10 modestly-sized cars per year (assuming a typical annual mileage somewhere between 10,000 and 15,000, and subtracting out the ~75-80% of energy output that was required to run the process), though some other crops would probably work better for ethanol. Biodiesel was closer to 50 cars when produced from soybeans, though the best known feedstock at the time was palm oil, and a square mile of that land could possibly power 1,000 cars. But solar panels bumped the number of cars into the tens of thousands (I wrote 50,000 in my old blog post, but I was probably rounding up a bit).

So while I'm sure accountants will cringe at the idea of solar for quite a while, it has long scored well in my book. I've always been a bit worried about the input and output streams of nasty chemicals from the manufacturing plants, though of course farms aren't exactly clean either with their massive amounts of runoff.

Oh, and I'll mention that the Twin Cities is at about the same latitude as southern France and northern Italy, since people always claim we don't get any sun. We're at 45 degrees latitude, which allows the neat trick of putting panels on the sides of things, like at the RiverCentre ramp in downtown St. Paul:

Image

Other thoughts on whether solar is worthwhile or not?
Last edited by mulad on July 30th, 2013, 2:22 pm, edited 1 time in total.

David Greene
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Re: Solar power

Postby David Greene » July 30th, 2013, 1:13 pm

mulad wrote:Over on the Minneapolis Energy Municipalization thread, solar power has been brought up a few times as being not yet ready for prime time. Does anyone have a good source for further details on that? I guess I've been watching solar prices drop precipitously and figuring that it made sense at this point to begin moving into it quite a bit.
It makes sense now for homeowners. We looked into this a few years back and as soon as we have enough money saved up we're putting panels all over our roof and garage. Yes, there is a subsidy and yes that subsidy is important in reducing the time to cost recovery, but honestly we're not really concerned about cost recovery. We like the idea of getting most if not all of our electricity from renewable sources.

I don't think big centralized solar farms are necessarily the right idea. A distributed grid of smaller installations seems more practical. When we get ours in place we'll be selling excess electricity to Excel.

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Re: Solar power

Postby RailBaronYarr » July 30th, 2013, 4:51 pm

Couple good reads on solar/distribution edge stuff from David Roberts at The Grist:

http://grist.org/article/whats-threaten ... -the-grid/
http://grist.org/climate-energy/solar-p ... utilities/
http://grist.org/climate-energy/imagini ... w-lorises/

Side note: I love when people breathe a sigh of relief when they see/hear that a parking ramp is made more sustainable by adding solar to help power it.

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Re: Solar power

Postby Mdcastle » July 30th, 2013, 9:26 pm

I'm not against using solar power to generate electricity for general use if there's not huge taxpayer subsidies, but the idea solar power -> electric cars ignores the fact that electric cars don't even come close to meeting my needs, so presumably not those of a number of other people.

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Re: Solar power

Postby David Greene » July 30th, 2013, 10:00 pm

Mdcastle wrote:I'm not against using solar power to generate electricity for general use if there's not huge taxpayer subsidies, but the idea solar power -> electric cars ignores the fact that electric cars don't even come close to meeting my needs, so presumably not those of a number of other people.
But they do meet the needs of me and my wife perfectly and I suspect many more people are in the same situation.

No one is saying they're a solution for everyone. But I do blieve they are a solution for a heavy majority of commuters. They are part of a solution to address our energy and climate problems.

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Re: Solar power

Postby RailBaronYarr » July 31st, 2013, 8:31 am

Mdcastle wrote:I'm not against using solar power to generate electricity for general use if there's not huge taxpayer subsidies, but the idea solar power -> electric cars ignores the fact that electric cars don't even come close to meeting my needs, so presumably not those of a number of other people.
Solar power only requires subsidies to be const competitive because other energy sources do not pay for their social costs (and, are also heavily subsidized). As for cars, electric vehicles are only as 'green' as the energy source that provides the electricity (not taking in to consideration the manufacturing process and batteries), and they do nothing to solve the environmental issues caused by wide-spread car use (parking lots, roads, etc). They;re a marginal improvement for people who occasionally use their cars, but even with an improved range would not be a panacea for the ills cars have produced.

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Re: Solar power

Postby David Greene » July 31st, 2013, 9:34 am

RailBaronYarr wrote:As for cars, electric vehicles are only as 'green' as the energy source that provides the electricity
My only quibble with your post is that electric vehicles make use of electricity generated at large plants, which should be more efficient than every vehicle running an ICE. So even if you're getting electricity from a coal plant, it very likely could be an environmental win over running a (very inefficient) gas engine.

Of course the more you can do to produce the electricity cleanly, the better it is. That's why we want solar panels on the garage.

Totally agree about the physical costs of everyone driving a car. It doesn't matter what the propulsion system is.

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Re: Solar power

Postby MNdible » July 31st, 2013, 10:11 am

I think the biggest benefit for solar energy is the ability to put electric generation right next to where it's being consumed. That way you limit the losses due to transmission, which can be staggering, depending on distance. This is also part of the reason why HERC micro-scale wind generation and additional hydro generation at St. Anthony Falls makes sense to me.

I do remain skeptical, though, that it's everything it's cracked up to be. Solar panel manufacturing involve a lot of nasty chemicals -- fortunately for us, that's mostly happening out of sight in China. Panel longevity and disposal is also an issue.

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Re: Solar power

Postby gahwi003 » July 31st, 2013, 10:53 am

David Greene wrote:
RailBaronYarr wrote:As for cars, electric vehicles are only as 'green' as the energy source that provides the electricity
My only quibble with your post is that electric vehicles make use of electricity generated at large plants, which should be more efficient than every vehicle running an ICE. So even if you're getting electricity from a coal plant, it very likely could be an environmental win over running a (very inefficient) gas engine.

Of course the more you can do to produce the electricity cleanly, the better it is. That's why we want solar panels on the garage.

Totally agree about the physical costs of everyone driving a car. It doesn't matter what the propulsion system is.
Not in china! A U professor studied this exact phenomenon and found gas engines were more efficient than the coal plants. Again, this is in china.

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Re: Solar power

Postby FISHMANPET » July 31st, 2013, 11:00 am

I don't really think you can make a direct comparison of different forms of energy generation. A coal power plant is probably more efficient than a coal car, but we don't have coal cars. A gasoline or diesel power plant is probably more efficient than a gasoline or diesel car, but we don't have gasoline or diesel power plants.

But I think that powering a car with natural gas generated electricity is cleaner than a gasoline car (though not as clean as wind/solar/nuclear). So if we have to be burning fossil fuels, natural gas would be better than coal (but we have so damn much coal!)

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Re: Solar power

Postby David Greene » July 31st, 2013, 11:04 am

gahwi003 wrote:Not in china! A U professor studied this exact phenomenon and found gas engines were more efficient than the coal plants. Again, this is in china.
That is...staggering. A really good gas ICE is about 30% efficient. It's hard to imagine a power plan less efficient than that.

Diesel can get you to 50% but even then it's hard to imagine a less efficient power plant.

Note that steam turbine propulsion systems are < 50% efficient but steam turbines in power plants are much more efficient.

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Re: Solar power

Postby David Greene » July 31st, 2013, 11:10 am

FISHMANPET wrote:I don't really think you can make a direct comparison of different forms of energy generation.
It depends on how you define "efficient." If you're look at the energy density of the fuel and compare it to the resulting work accomplished, I think it is fair to make the comparison. I'm not a chemist but as I recall thermodynamic efficiency (which is what is usually reported) tries to account for the heat loss during combustion. Comparing heat loss across energy sources also seems fair.

The power plant efficiencies don't account for transmission loss, supporting MNdible's point about distributed generation.

Hopefully a real chemist can shed some more light.

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Re: Solar power

Postby RailBaronYarr » July 31st, 2013, 1:12 pm

It's not about efficiency, at least not that a thermodynamics nut would need to explain. It's about the total pollutants emitted throughout the entire energy value chain. Very hairy subject to get to the true bottom of. For ICEs, you have direct emissions, but also emissions in finding, acquiring, refining, and moving oil. You have a certain amount of emissions in manufacturing the vehicles. For electric vehicles, you have a different set of equations.. how much energy (coal, natural gas, hydro exploration/etc/etc) and resulting emissions does it take to send power to your home/charging station, including the losses along the lines? How much more harmful is manufacturing an EV vs ICE, and implications of the batteries after their lifecycle. As I understand it, taking the current average of US electricity source and transmission, EVs are close to and sometimes worse than the ICE pollutant chain (which can and will change over time, but slowly because generation facilities are large, 30-50 year capital investments, plus the political realities of implementing new technologies or distributed sources like solar/wind).

Same comparisons can be made for general comments regaring solar vs fossil fuel plant generation. An ideal system, in my mind, leverages high-voltage power (the grid) generated from a mix of energy sources (that are not named coal) with distributed power (solar, wind, micro natural gas turbines, etc) for the off-peak (daytime) demand, supplementing peak grid demand, and backup for possible grid outages. Cleaner sources of grid energy should be located near population centers to reduce line loss when possible (St Anthony Falls example) (and hey, if we can get more people to live closer together on average, there are some savings, too!).

But once again, these efficiency gains and pollution reduction methods are great, but only one piece of the puzzle. Driving a Prius 30 miles each way to work is not as green as a 7 mpg pickup making a 5 mile round trip commute. Land-use pattern changes can have drastic impacts on the actual amount of energy we all actually need on a daily basis. I'm of the opinion that focusing solely on efficiency gains (or finding a source of energy that equals today's output but cleaner) will only drive more consumption, negating the positive impacts.


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