Solar power & Wind Power for residental use

[KennyG]

KennyG, Thanks for that. Is my understanding correct that, as with molten salts in a solar powered system (where the sun's heat is concentrated to heat the salts to a liquid state - typical temps exceed 1000F according to the 'net, the heat is then used to produce steam to drive generators?

If that is so, then the salts are storing heat, which is capable of continually being renewed to working temperature by the reactor (if I understand correctly) since you are saying that all but 1% or so of the heat is unused in the steam production. That would make it similar to the way the solar heated method operates (this keeps me on topic!!) except that the solar method stores the heat for use overnight, and uses much more of the stored heat, possibly/probably/definitely enough that the salts return to a solid state due to the drop in temperature, therefore needing to be reheated to a much greater degree than that used in the nuclear method.

The nuclear also has the advantage of being able to add more heat on a permanent basis, (must add more to maintain the cooling process?) whereas the solar relies on the sun during daylight hours. Or, if the stored heat at sunrise in the solar method still remains high enough to produce steam for the generators, it merely needs to be "topped up" as with the nuclear method. I do not know, because the blurb is all about being able to produce electricity from the sun during the night. As with most things in life neither side gives you the full info.

Yes, the "solar thermal" plants heat the salt and the heat in the salt is used to boil high pressure water, run the turbines and generate electricity. After the sun goes down, the salt can continue to generate steam until the salt temperature drops. As the temperature drops, the steam cycle efficiency drops, from as high as over 40% to probably less than 30% until the temperature drops low enough the salt begins to solidify. Keep in mind when we say "salt" we aren't talking about table salt, we're talking about a chemical compound in the salt family. Solar plants use salts that melt at 300 deg F to 400 deg F. You can't let the temperature of the storage facility drop to the solidification temperature because reheating takes a long time. Nuclear reactor salt will usually have a higher melting point because nuclear characteristics are more important than a low melting point.

Nuclear reactors, like any other steam cycle based generating facility convert 30 to 50% of the heat to electricity. During operation, most of the heat comes from nuclear fission. When the plant shuts down, that heat is no longer being generated. However, decay heat is generated from the results of the fission process. That is initially about 1% of the original power generation and slowly decreases over a period of time. The ability to "store" or "absorb" energy in the molten salt reactors is advantageous from a safety standpoint, but not important for operation because you can generate heat at any time from the reactor in operation.

Interestingly enough, the European/US countries have focused on molten salt as a coolant, while the Russians have focused on molten lead. They have similar characteristics and advantages. I'm not an expert in this area, but it appears salt is better from a contamination control/nuclear design aspect but lead has advantages from a materials stability (less corrosive) viewpoint.

 

[OldMcDonald]

B&D/KennyG, Thanks both for your replies. I find them very informative. I am sure others do too.

I used the terms salts rather than salt - because everyone immediately thinks table salt, because I understand (as I posted earlier) that the ones used in the concentrated solar are a mixture of Sodium nitrate and Potassium nitrate. At the end of the generating plant's life, they can then be used as fertiliser. Idle curiosity, but do either of you know what is used for salts in nuclear? I follow the reasoning for using a different mix for nuclear. Thanks to you both again.

 

[techman]

The increase in electric rates in the past decade+ are not due to renewable subsidies but mostly to increases in fuel costs, and utility profits.

paul

 

[OldMcDonald]

Is the US undermining India's solar power programme? - BBC News

Pertinent to this thread.

 

[KennyG]

There have been a number of salts used in nuclear designs, primarily sodium chlorides and sodium fluorides, often with some Lithium or Berylium for nuclear physics characteristics. In some designs the fuel (Uranium or Thorium) is actually dissolved in the coolant salt. I'm sure there is work going on now on different approaches.

 

[buickanddeere]

The increase in electric rates in the past decade+ are not due to renewable subsidies but mostly to increases in fuel costs, and utility profits.

paul

proof ? How can green power be paid subsidized wholesale rates without increasing the retail price ?

 

[Egon]

proof ? How can green power be paid subsidized wholesale rates without increasing the retail price ?

Why should a subsidy raise the retail price??

Another view point:
There may be pension plan deficiencies also.
Plant rebuilds also to add to the cost.
Smart meters added to cost.
[video]http://www.ontario-hydro.com/index.php?page=salaries_2014[/video]

 

[techman]

proof ? How can green power be paid subsidized wholesale rates without increasing the retail price ?

Simple. The subsidy is from the government, not the utility

 

[3930dave]

Why should a subsidy raise the retail price??

Another view point:
There may be pension plan deficiencies also.
Plant rebuilds also to add to the cost.
Smart meters added to cost.
[video]http://www.ontario-hydro.com/index.php?page=salaries_2014[/video]

Pension exposure is significant.

As of May 2014, Ontario had dropped $2Billion (Bravo) so far, on "smart" meters.

I'll post the Auditor General's report that # came from in the electricity cost thread, as it more relates to that topic than OP's.

http://www.tractorbynet.com/forums/rural-living/301721-what-earth-does-electricity-cost-30.html

Post # 291 in linked thread.

Another thing I found interesting in that report was that Germany looked at broad-scale implementation of "smart" meters, and decided that it didn't make sense. Unfortunately, few people read these reports, and fewer still base their voting decisions on them.

Rgds, D.

 

[truckdiagnostics]

Why should a subsidy raise the retail price??

Another view point:
There may be pension plan deficiencies also.
Plant rebuilds also to add to the cost.
Smart meters added to cost.
[video]http://www.ontario-hydro.com/index.php?page=salaries_2014[/video]

So in your system that runs on pixy dust at night the meters are free and there is no pensions for the workers maintaining the solar grid and the solar panels never break down and don't need to be maintained.