<story><title>Arizona solar plant achieves six hours after sun goes down</title><url>http://phys.org/news/2013-10-arizona-solar-hours-sun.html</url></story><parent_chain><item><author>Lagged2Death</author><text>I&amp;#x27;ve been puzzled for some time: Is anyone &amp;#x2F; why isn&amp;#x27;t anyone working on more flexible and responsive coal and nuclear plants? Instead of storing renewable energy, it would be more efficient, less complex, and less capital-intensive (one would think) to consume the renewable energy immediately and make up the difference between supply and demand with flexible traditionally-fueled plants.&lt;p&gt;I&amp;#x27;m sure there&amp;#x27;s a good reason. I just don&amp;#x27;t know what it is.</text></item></parent_chain><comment><author>DougWebb</author><text>By flexible, do you mean &amp;quot;able to ramp up to meet demand and ramp down when not needed&amp;quot;?&lt;p&gt;Any power plant that uses steam turbines is going to have a long ramp-up time to boil a huge quantity of water needed to produce the steam. Nuclear plants do this, and I imagine most&amp;#x2F;all coal plants do as well. Hydroelectric plants don&amp;#x27;t need to because the falling water drives the turbines directly.&lt;p&gt;The first thing I thought of when I read the article is that this power plant can&amp;#x27;t be very efficient. It&amp;#x27;s using steam turbines, but six hours after sunset there isn&amp;#x27;t enough heat to keep the turbines going. That means they need to reheat every morning. It seems like it would have been better for them to include a coal plant for nighttime operations to keep the steam boilers hot and keep the turbines going all night. That would be flexible, because the coal burners could start up quickly to keep the already-hot water boiling. (Can&amp;#x27;t use nuclear this way because you can&amp;#x27;t really turn a nuclear reactor on and off.)&lt;p&gt;I&amp;#x27;m totally guessing here, but I suspect they didn&amp;#x27;t include an alternate nighttime operations fuel because this is a &amp;quot;100%-Green&amp;quot; project that either wouldn&amp;#x27;t have gotten funding if there was a coal plant involved or it was just intended as a demonstration of the solar capability and didn&amp;#x27;t need to be practically efficient.</text></comment>
<story><title>Arizona solar plant achieves six hours after sun goes down</title><url>http://phys.org/news/2013-10-arizona-solar-hours-sun.html</url></story><parent_chain><item><author>Lagged2Death</author><text>I&amp;#x27;ve been puzzled for some time: Is anyone &amp;#x2F; why isn&amp;#x27;t anyone working on more flexible and responsive coal and nuclear plants? Instead of storing renewable energy, it would be more efficient, less complex, and less capital-intensive (one would think) to consume the renewable energy immediately and make up the difference between supply and demand with flexible traditionally-fueled plants.&lt;p&gt;I&amp;#x27;m sure there&amp;#x27;s a good reason. I just don&amp;#x27;t know what it is.</text></item></parent_chain><comment><author>rwmj</author><text>As an uninformed guess: you want to minimize the number of heating and cooling cycles because that causes joints to crack.  They used to keep steam trains running for days at a time (meaning they were kept fired overnight even when not used) to avoid cooling cycles.&lt;p&gt;Actually I would also be interested to know the real answer to this too.  There was an interesting article in the Economist this week about the problems of the constant power output of nuclear and coal plants.</text></comment>