[JayHMorrison]

I expect solar power to become competitive

How will it become "competitive?" Competitive with what?

Explain your question. What don't you understand about the word competitive and the concept of electricity?

[Devil]

a) Solar has the potential to meet about 10% of our overall energy needs.
b) Wind has the potential to meet about 20% of our overall energy needs.

For the sake of debate, let us assume that in 20xx, we shall require 20 quads of distributed electricity, as a round figure. To round it further, say, 5,000 TWh. This would require a generating capacity of, say 1,000 GW (still rounding to convenient figures. 20% of this is 200 GW, which represents the capacity of 67,000 state-of-the-art windmills, by today's standards at a cost of ~$500,000 each (on-shore, double for off-shore) including charges for connecting to the grid or $33 billion. Fine, but there are some problems: in most localities, turbines produce only ~15% of their rated capacity because of the variability of winds (maybe 20% on top of the Sear's tower in the Windy City!), so the total output from wind would be only 3%, not 20%. AND 20% of the capacity is ALL the variable sources that a grid can withstand and maintain stability, including solar. What is little understood is that the turbines are rated at 20 m/s wind speed. At 10 m/s, the output is only about 30% At 5 m/s, it is < 10%. At 25 m/s, the output is 0%, because the blades have to be feathered or they will suffer damage.

In favourable positions, such as places with >2000 hours insolation/year, solar fares better, provided they have a sun follower. You may actually get as much as 20% of the rated capacity. 10% of the grid capacity of 1000 GW is 100 GW, which is equivalent to the average you could obtain from 700 million m². The actual installation would need 3 times this area to avoid shadowing and allowing access for maintenance. So you would need at least 2,000 km² of land and the panels would cost $70 billion (even allowing for economy of scale) plus the followers and inverters to provide just 2% of your needs.

Now, let's imagine that a power peak demand occurs when the wind isn't blowing (large anticyclone) and the sun isn't shining, perhaps at night. No variable sources power! That means that your constant output installations, such as nuke, have to provide 97.38% of the demand (hydro can take care of the rest).

The maths don't look too good, do they?

Can something else be done? The answer is yes! Scrap sink disposal units (which are environmentally bad as they overload the PWTUs with too much organic matter) and collect all refuse in special containers, along with all non-recyclable wood, paper, plastics etc.. These are carted away to a refuse-burning power station equipped with suitable waste gases treatment. The cost of the fuel is equal to that of the garbage collection service, which is necessary, anyway. This is done in several Swiss towns and they prove to provide about 9.9% of the electricity consumed in the collection area and the system can provide almost 10% CONTINUOUSLY, so requires no more back-up generating capacity than a nuke or coal-fired power station. Another advantage is that it reduces landfill capacity very substantially (by about 85-90%). This works! The disadvantage is that it is really suitable only for towns with a population exceeding 100,000, so small remote communities are left in the cold. Capital costs are not cheap, because of the need to clean the exhaust gases, but this is offset by low fuel costs.

[JayHMorrison]

Devil, you raise some valid issues on the hurdles and costs.

But the evidence seems to support that wind can handle about 20% of the electric grid load total. During some periods of time in Denmark, wind power meets 100% of the power needs of western Denmark.

I did a search to get updated info and it looks like they are projecting 29% of their electric grid will be wind powered be the end of 2005.

http://www.scandinavica.com/culture/nature/wind.htm

I am also a big fan of biomass. If we could also do 10% of the electric grid from biomass, no objections from me.

[Frank]

...collect all refuse in special containers, along with all non-recyclable wood, paper, plastics etc.. These are carted away to a refuse-burning power station equipped with suitable waste gases treatment. The cost of the fuel is equal to that of the garbage collection service, which is necessary, anyway. This is done in several Swiss towns and they prove to provide about 9.9% of the electricity consumed in the collection area and the system can provide almost 10% CONTINUOUSLY, so requires no more back-up generating capacity than a nuke or coal-fired power station. Another advantage is that it reduces landfill capacity very substantially (by about 85-90%). This works! The disadvantage is that it is really suitable only for towns with a population exceeding 100,000, so small remote communities are left in the cold. Capital costs are not cheap, because of the need to clean the exhaust gases, but this is offset by low fuel costs.

I'm in favor of trash burning plants in principle, but they require an educated, caring public who understand proper waste segregation. Dioxin, heavy metals, etc. are pretty bad if the wrong stuff gets in there, even with the best stack scrubbers available.

[Devil]

Devil, you raise some valid issues on the hurdles and costs.

But the evidence seems to support that wind can handle about 20% of the electric grid load total. During some periods of time in Denmark, wind power meets 100% of the power needs of western Denmark.

I did a search to get updated info and it looks like they are projecting 29% of their electric grid will be wind powered be the end of 2005.

http://www.scandinavica.com/culture/nature/wind.htm

I am also a big fan of biomass. If we could also do 10% of the electric grid from biomass, no objections from me.

Interesting you should quote Denmark, as they had a massive power failure on their Jutland grid because they exceeded the "magic" 20% of capacity figure, in fact, I believe, about 23%. The wind, one day, was blowing like fury, and then stopped within an hour. The running reserve could not take up the loss and every cut-out on the grid, and into Germany, tripped, plunging parts of Jutland into darkness for several hours.

Denmark is peculiar in that they have two grids, Jutland and Zealand. The main consumers (Copenhagen and thereabouts) are on the latter, whereas there are few large towns (e.g. Aarhus) on Jutland. These grids are not interconnected, but both are connected to the German grid at different points. As a result, Jutland is a nett exporter while Zealand is a nett importer. Germany could not make up the loss due to the instability of the Jutland grid.

As a result of this event, Denmark has stopped all government backing and subsidies for wind technology.

There is one small Danish island that claims to be independent of the grid, but this is not true: it exports more electricity from wind than it imports, that's all.

Note that the 18-20% limit for renewables to ensure grid stability is related to the peak capacity, yes, CAPACITY and not to the amount of electricity produced. The two would coincide only in a place where the wind blew at a constant velocity of 20 m/s 24/7/52. I don't know any place on earth where this is so, not even Cape Horn. Do you?

[JayHMorrison]

It does seem that current electric grid management strategies are limiting Wind to about 20% of total electricity. I see that over and over in any objective study.

Are their any large scale examples that contain significant solar and wind in the same grid area?

The Green party in Germany (junior party in ruling coalition) actually plans to shutdown Germany's nuclear power plants. Their solution is use all wind power. So much for that idea.

[Devil]

It does seem that current electric grid management strategies are limiting Wind to about 20% of total electricity. I see that over and over in any objective study.

Are their any large scale examples that contain significant solar and wind in the same grid area?

The Green party in Germany (junior party in ruling coalition) actually plans to shutdown Germany's nuclear power plants. Their solution is use all wind power. So much for that idea.

When Chancellor Schroeder was nominated, he had to coalesce his Social Democrat Party with the Greens to obtain a majority. This is why Joschka Fischer, at the time an extremist ecopolitician, is Foreign Minister. The payoff was that he would close down Germany's nuclear power over a period of 30 years. In fact, Fischer now wears a suit and tie with a clean shirt and has greatly moderated his stance. It now seems that he has accepted nuke as being preferable to fossil fuel. Of course, it is ridiculous to use 100% wind power and I believe their aim is a modest 15% by 2010.

[JayHMorrison]

Devil,

What do you see as the eventual mix of energy options for the power grid that makes the most sense?

If we draw the conclusion that wind is likely capped at 15% to 20% for electricity, what is the most likely option to fill the remaining 80%. I am assuming that coal becomes unacceptable in the coming years as global warming evidence accumulates.

The only option remaing that I can find appears to be nuclear. Solar, hydro and biomass all appear to be limited to under 10% each.

[Devil]

On the basis that solar and wind are both variable and must have 100% backup, it is clear that invariable sources must be able to provide the peak demand.

I believe that the first measure is to reduce the peak demand. A good way of doing this is to stagger peak hours over a grid. If ¼ of the normal daytime working population start work at 6 am, ¼ at 7 am, ¼ at 8 am and ¼ at 9 am, this staggers the peak over 4 hours, especially if done over whole states, e.g., New Jersey at 6, New York at 7, Mass. at 8 and the rest of New England at 9. The going-home time would also be staggered accordingly, so that each area could have its TV scheduled accordingly, so that Jay Leno would come on 4 hours later in NH than in NJ. On the same theme would be to forbid the sale of energy-guzzlers, such as tungsten light bulbs, poorly insulated fridges, CRT monitors and TVs and so on. If we could reduce the peak demand by 20%, this would be significant, for starters; it means the whole grid and generating capacity could be scaled accordingly.

Then 10% of current peak can be achieved by burning garbage, so this would supply 12.5% of the reduced peak. Hydro depends on the country: Switzerland is roughly 60% hydro/36% nuke/0% fossil fuel just now. However, hydro is generally very dangerous on a large scale and environmentally devastating. That really leaves only nuclear for the bulk of the supply. However, when the wind blows or the sun shines, the nuke generation can be cut down to conserve uranium, to the limit of ~20% of peak.

This is my view of the short-medium term future.