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[mainiac]

There was a factoid i read once that 90% of Australia's Arable landmass would need to be dedicated to producing biofuel crops to supply all of Australia's needs.

I doubt it.

Australia has about a third the arable land that the US currently has currently cultivated land.  The US with that cultivated land produces 15 billion gallons of ethanol along with enough food to feed ourselves (only a very slight net importer) and waste 40% of our food while we're at it.  So Australia could produce 5 billion gallons of ethanol along with the food for about 100 million people.  Australia consumes about 5 billion gallons of gasoline a year and has a population of 23 million people.  Now 5 billion gallons of gasoline is equivilent to about 7.5 billion gallons of ethanol because gasoline is more energy dense.  So you'd need to jigger things a little, you don't need to feed 100 million people after all.  But Australia wouldn't need to go to absurd lengths to produce it's own ethanol, it would look like the US does right now.

[Orange Wizard]

There was a factoid i read once that 90% of Australia's Arable landmass would need to be dedicated to producing biofuel crops to supply all of Australia's needs.

I doubt it.

Australia has about a third the arable land that the US currently has currently cultivated land.  The US with that cultivated land produces 15 billion gallons of ethanol along with enough food to feed ourselves (only a very slight net importer) and waste 40% of our food while we're at it.  So Australia could produce 5 billion gallons of ethanol along with the food for about 100 million people.  Australia consumes about 5 billion gallons of gasoline a year and has a population of 23 million people.  Now 5 billion gallons of gasoline is equivilent to about 7.5 billion gallons of ethanol because gasoline is more energy dense.  So you'd need to jigger things a little, you don't need to feed 100 million people after all.  But Australia wouldn't need to go to absurd lengths to produce it's own ethanol, it would look like the US does right now.

Also, Australia doesn't use gallons

[Reelya]

I'm not getting those numbers to reconcile.  When I do nuclear with optimistic assumptions for "median" (4 year construction, middle costs equally distributed over 4 years) I still get a present value cost per Mwh of 70.  And when I do solar with pessimistic assumptions (1 year construction before output, maximum price) I get a present value cost per Mwh of 235.  If I do solar with optimistic assumptions (minimum price, 3 month construction) I get 122.

The numbers, IIRC, are based on historical averages up to 2012. Solar power price probably has dropped in recent years.

"Probably". Right.

http://www.computerworld.com/s/article/9244836/Solar_power_installation_costs_fall_through_the_floor

December 16, 2013

The cost of installing photovoltaic solar arrays has dropped to $3 per watt of electricity they produce - about the same as coal-powered plants cost to build - creating a watershed moment in the development of clean energy, experts say.

The average price of a solar panel has declined by 60% since the beginning of 2011, according to GTM Research. And, according to CleanTechnica, a website dedicated to renewable energy news, the price of solar power has fallen rom $76.67 per watt in 1977 to 74 cents today.

Average installation costs are definitely at the bottom-end of the data you provided on page 1. Giving the median of current and historical prices of solar is therefore meaningless, when the commodity is 100 times cheaper than 35 years ago. You can't say the same thing for e.g. coal or uranium.

[alway]

Another interesting power storage method: http://www.scientificamerican.com/article/energy-storage-hits-the-rails-out-west/

During periods of low electricity demand, power is dispatched from the nearby grid to pull a chain of weighted train cars uphill. And there they will sit—losing no power to degradation—until the grid has a period of high power demand. Then they are sent rolling downhill. Their momentum sends electrons back to the grid through a system of regenerative braking that uses the turning power of the wheels to generate electricity.
...
ARES predicts its operation will cost only half of what a pumped hydro project with similar energy output would require, and should have a much smaller environmental footprint.
...
During slow periods, the cars may discharge their cargo at the top and go back down, empty, for more, as heavier loads allow for increased generation capacity.
...
Ramp-up times average from five to 10 seconds. That's not quite as good as a chemical battery, which can output its full capacity immediately, but is significantly better than the rate of a combined-cycle natural gas plant, which ramps up about 8 percent of its output per minute.

Basically, you need really powerful, easily varied output power production/storage methods to make a largely renewable grid work. Solar and wind go up and down, resulting in the need for rapidly toggled power stations. Based on a quick google, nuclear doesn't fit that quite as well, since it takes around 30 minutes to go from low output to full output. So this sort of storage for normal grid fluctuation control would be pretty necessary if most of the grid were to be transferred to the rapid-variation clean energy.

[WillowLuman]

Ah, here is a subject I've done tiring academic work on.

The main way to use energy better is to cut down on transmission. Areas should try to use locally available sources of power, rather than having it brought over long distances, and long transmission is highly inefficient. It's better to have a wind turbine or solar panel on your roof than to depend upon a solar or wind farm; this not only reduces transmission waste but means less space is used overall. And when in-situ generation is not possible or sufficient, it's better to have a local power plant than to have a massive one servicing places 80+ miles away. There is no one energy source that will be the best in all situations or places, but rather a combination must be used to best suit the needs of each area in the most efficient way possible.

For traditional combustive power, biofuel is by far better environmentally than anything mined, because it is ultimately carbon neutral. Whatever carbon comes from burnt plants had to have been pulled by those plants from the atmosphere in the first place, but buried carbon has been out of circulation for millions of years, and so burning it increases the carbon in the atmospheric reservoir. Someone pointed out wood earlier, but wood is a terrible choice for biofuel. It is highly inefficient for mechanical energy, and takes a long time to grow back. A much better energy crop would be agave, which can grow in arid regions and has approximately 40-60% higher yield for biodiesel than corn. Or algae, which can grow in (and help purify) waste water and can have approximately 200-1000% higher yield for energy than corn.

Conventional nuclear power is cleaner on the short term and offers massive energy yields, but at the cost of massive, expensive long-term problems dealing with highly toxic waste. However, new technology such as re-breeder and pebble-bed reactors can cut down on waste and reduce risks of leakage, though some waste will always be produced and must be managed for a long, long time. Thorium may provide not only a cleaner but a more common and higher yield nuclear fuel, though. Developments in fusion continue, and if the problems of containment and sustenance can be solved, it offers massive, massive yield with massive efficiency, but likely still won't be viable for some time yet.

Mathematically, wind power contains enough energy to meet current demand nearly 200 times over, provided there was a way to transmit it with no loss. As such, people living in any area would be able to offset their reliance on other sources to at least some degree by supplementing them with wind turbines. Helix turbines may provide not only more efficient means of gathering power than the traditional "tripod" shape, but also present a more solid profile to flying creatures, preventing collisions, and produce less noise.

[alexandertnt]

Basically, you need really powerful, easily varied output power production/storage methods to make a largely renewable grid work. Solar and wind go up and down, resulting in the need for rapidly toggled power stations. Based on a quick google, nuclear doesn't fit that quite as well, since it takes around 30 minutes to go from low output to full output. So this sort of storage for normal grid fluctuation control would be pretty necessary if most of the grid were to be transferred to the rapid-variation clean energy.

We can store solar power as heat, by using the sun to heat up fluids rather than by using photovoltaic panels.

[10ebbor10]

That's a rather expensive and inefficient solution however. Also, it's not that fluctuation resistent.

[DJ]

Flywheels

[alexandertnt]

That's a rather expensive and inefficient solution however. Also, it's not that fluctuation resistent.

Are you sure? According to Wikipedia, Solar Two can generate full power with no light for 39 hours.

As for the price, I suppose photovoltaic panels become cheaper and giant mirrors dont.

[Sheb]

Biofuels, at least the current sorts are horrible. We just don't have enough land. Algae are awesome, but you need much more infrastructure. I remember doing the math and you'd need 100000 sq km of algal tanks to produce enough biofuels to replace all our oil us.

[DJ]

Oceans' surface is 361 000 000 km^2, so there's more than enough room for that.

[Sheb]

Well, it's still a hell of lot of infrastructure.

[10ebbor10]

That's a rather expensive and inefficient solution however. Also, it's not that fluctuation resistent.

Are you sure? According to Wikipedia, Solar Two can generate full power with no light for 39 hours.

As for the price, I suppose photovoltaic panels become cheaper and giant mirrors dont.

Still doesn't help much if it's cloudy for an entire weak. Anyway, molten Salt solar only has a capacity factor of 60-70%, which is signficantly better than 20% of normal solar, but still not that cheap.

The Gemasolar thermosolar plant (Solar Two commercial succesor) has 19.9 MW generation capacity and cost about 250 million euros (estimates vary between 220 and 260. Also 80 million of that was subsidized, so that reduces capital costs). If you want to replace a 1 GW nuclear plant with that, you're looking at 17 billion euro. 12.5 billion if you exclude capacity factor differences. 

[Mech#4]

Well, it's still a hell of lot of infrastructure.

That's if it's all flat like a field though, yes? Could you design a structure like a giant beehive with lots of small compartments built through it, each growing algae. It could be like a giant sponge; pour water/sugar/whatever algae like through the top and let it filter through. 3D printing could build the individual cells as it might be too complicated for factory construction.

[Sheb]

Well, you need light for your algae, so you structure has to be more or less flat.