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  1. Standard member sonhouse
    Fast and Curious
    12 Jul '11 01:18
    http://www.physorg.com/news/2011-07-gemasolar-solar-thermal-power-hours.html

    Provides almost 20 megawatts 20 to 24 hours a day right now! It means 30,000 tons a year less CO2 crammed into the atmosphere!

    Great project! The only downside I see is in the photo, it is taken from a long ways away, the tower is 150 meters high and the solar field is about 700 meters in diameter. From the shadow dots you can see in the image where the sun is being blocked by the reflectors, it is clearly way less than 50 percent in usage of the available space.

    The area represents a huge radiation of energy, looks like almost 500,000 square meters and on top of the atmosphere, there is about 1000 watts per square meter, maybe 30 % of that reaches the ground, so 300 watts per meter on the Earth. That represents about 150 megawatts or so if the conversion was 100%, or 37 megawatts or so at 25% so to get 20 Mw out of 500,000 square meters seems a bit inefficient in terms of extracting as much energy as possible from each square meter.

    It is inefficient simply because of the spacing of the reflectors. There is clearly sunlight between the reflectors that could be paved with PV cells so you could get the best of both technologies.

    Clearly, engineering improvements are there to be had.
  2. 12 Jul '11 08:04
    Originally posted by sonhouse
    It is inefficient simply because of the spacing of the reflectors
    You seem to be assuming that land comes at a premium. I don't think that is the case.
    The main concern with solar is not area, but manufacturing and maintenance costs (of which land is a very small part).
  3. 12 Jul '11 08:08
    Originally posted by sonhouse
    It means 30,000 tons a year less CO2 crammed into the atmosphere!
    So an equivalent coal power plant uses about 30 tons a day of coal?
  4. Standard member sonhouse
    Fast and Curious
    12 Jul '11 12:57 / 1 edit
    Originally posted by twhitehead
    So an equivalent coal power plant uses about 30 tons a day of coal?
    Wiki says there is about 2500 kw hours of usable energy from one ton of coal. A 20 megawatt plant would generate about 175,000 megawatt hours of energy in a year and so to run a 20 megawatt plant for one year looks like it needs 70,000 tons of coal.

    The number of 30,000 tons looks even lower than it seems, they probably used that number based on 100 percent efficiency. I assumed an efficiency of about 40 percent.

    Coal generates roughly the same weight in CO2 as it weighs so a 20 megawatt plant would generate about 70,000 tons of CO2 in a year or about 200 tons per day of CO2.
  5. Subscriber joe shmo
    Strange Egg
    12 Jul '11 14:07
    Originally posted by sonhouse
    http://www.physorg.com/news/2011-07-gemasolar-solar-thermal-power-hours.html

    Provides almost 20 megawatts 20 to 24 hours a day right now! It means 30,000 tons a year less CO2 crammed into the atmosphere!

    Great project! The only downside I see is in the photo, it is taken from a long ways away, the tower is 150 meters high and the solar field is about ...[text shortened]... d get the best of both technologies.

    Clearly, engineering improvements are there to be had.
    It says at bottom that its a joint venture with Abu Dhabi...
  6. 12 Jul '11 18:54
    Originally posted by sonhouse
    .... or about 200 tons per day of CO2.
    Any idea how much coal a typical coal hopper (train) can carry. I am just wondering how many trains per day are needed to feed these power stations.
  7. Standard member sonhouse
    Fast and Curious
    13 Jul '11 00:09 / 1 edit
    Originally posted by twhitehead
    Any idea how much coal a typical coal hopper (train) can carry. I am just wondering how many trains per day are needed to feed these power stations.
    It looks like one train car carries about 120 tons of coal. For small 20 mw plant that would be about 600 cars per year or about 2 cars per day. So a 2 gw plant would require 200 cars a day, 100 times as much. 24,000 tons per day or almost 9 million tons per year. Gad! That's a lot of coal! Even for a tiny 20 mw plant!

    1000 tons per hour for the big plant, don't even know if there ARE 2 gigawatt coal fired plants. That would be 555 pounds per second! or 250 Kilograms per second. Moggles the bind!
  8. 13 Jul '11 13:22
    http://en.wikipedia.org/wiki/Taichung_Power_Plant

    largest coal powered power plant in the world...

    5,780 MW (~5.8 GW)

    http://en.wikipedia.org/wiki/List_of_largest_power_stations_in_the_world

    info looks to be out of date, but works as starting reference point.
  9. 13 Jul '11 20:17
    Originally posted by sonhouse
    So a 2 gw plant would require 200 cars a day, 100 times as much. 24,000 tons per day or almost 9 million tons per year.
    It seems your calculations were about about double the true figure - not bad at all for a quick estimate.
    According to wikipedia The Taichung plant googlefudge referenced is nearly 6GW and uses about 14.5 million tonnes a year, so a 2GW plant should use about 4.8 million tonnes.

    But then the type of coal used probably makes a big difference.
  10. 13 Jul '11 23:28
    Originally posted by twhitehead
    It seems your calculations were about about double the true figure - not bad at all for a quick estimate.
    According to wikipedia The Taichung plant googlefudge referenced is nearly 6GW and uses about 14.5 million tonnes a year, so a 2GW plant should use about 4.8 million tonnes.

    But then the type of coal used probably makes a big difference.
    you also need to consider economies of scale and power plant efficiency.
  11. Standard member sonhouse
    Fast and Curious
    14 Jul '11 01:29
    Originally posted by twhitehead
    It seems your calculations were about about double the true figure - not bad at all for a quick estimate.
    According to wikipedia The Taichung plant googlefudge referenced is nearly 6GW and uses about 14.5 million tonnes a year, so a 2GW plant should use about 4.8 million tonnes.

    But then the type of coal used probably makes a big difference.
    I wonder how many coal fired plants there are in the world, how much total world burning of coal there is. It must be a frightening number of megatons.
  12. Standard member sonhouse
    Fast and Curious
    14 Jul '11 01:30
    Originally posted by twhitehead
    It seems your calculations were about about double the true figure - not bad at all for a quick estimate.
    According to wikipedia The Taichung plant googlefudge referenced is nearly 6GW and uses about 14.5 million tonnes a year, so a 2GW plant should use about 4.8 million tonnes.

    But then the type of coal used probably makes a big difference.
    I wonder if they have fudged the figures to make themselves look more efficient than they are?
  13. 14 Jul '11 10:21 / 1 edit
    Originally posted by sonhouse
    I wonder how many coal fired plants there are in the world, how much total world burning of coal there is. It must be a frightening number of megatons.
    And don't forget all the fuel used to mine and transport the stuff.
  14. Standard member CalJust
    It is what it is
    25 Jul '11 10:32 / 1 edit
    Originally posted by sonhouse
    Coal generates roughly the same weight in CO2 as it weighs.
    The atomic weight of C is 14 and O is 16.
    So 14 kg of C makes 46 kg of CO2.

    In rough figures, therefore, 1 kg of coal makes 3 kg of CO2 (if the ash content is not too high)

    1 kWh is equivalent to 3,6 MJ.

    As a rule of thumb, depending on the grade of coal and the efficiency of the power station, if you say that 1 kWh of electricity results in approx 1 kg of CO2 you will not be far from wrong.
  15. 25 Jul '11 11:28
    Of course all these figures are just used for their wow factor or scare factor. 1 ton or 100 tonnes just sound big and scary, when in reality most of us know nothing about how much that impacts the environment.