Rod Adams wrote:Me: How do you expect for windmills and solar panels to produce power when the wind is not blowing and the sun is not shining?
There are indeed times when the wind is not blowing and the sun is not shining. Similarly, there are times when one is not near an electrical outlet, and wishes to use a portable electronics device, say a cellular phone.
One could conceivably use a device that would be able to draw energy from an electrical outlet when you are near one, and return energy when you are not near one. In common parlance such a device is called a "battery".
Energy storage is a fairly common phenomenon. Batteries of all shapes and capacities store electrical energy received from an electrical generator for a few days or years. The human body stores energy in fat cells after meals. Coal, natural gas, and oil store energy received from the Sun thousands of years ago.
While there are times when the wind is not blowing and the sun is not shining, there are very few times when gravity is not acting on everything on the surface of the earth.
Provided that the amount of energy that can be collected when the sun is shining (high part of the cycle, if you will) is enough to cover a bit less than twice the anticipated usage over the entire cycle (starting when the sun starts shining, and ending when the sun starts shining again after not shining for a while), it is, indeed, possible to supply a constant amount of energy throughout the cycle. Although the traditional kinds of electrical batteries are fairly unpractical for higher amounts of energy to be stored, energy can be converted to other types.
Consider, for example, a large container of a liquid, situated near an elevation difference. Experience with exisiting generating stations located at dams (for example, the Hoover Dam brought up earlier in this thread) suggests that once water (a liquid) is at a higher elevation, it is possible to generate energy in the form of electricity using this elevation difference. Further experience with pumps such as the ones that allow people living in skyscrapers to have water flowing from their taps tells us that it is possible to use mechanical energy to move water to a higher elevation.
What if, then, we used energy when it is available to move a liquid to a higher elevation, then return it to a lower elevation to generate energy when the natural source is not providing its energy? This process is fairly similar to charging a battery in a cellular phone and then being able to use it when we are not near a source of electrical power.
Let us assume that the operation of such a system is about 75% efficient. (Literature suggests efficiencies of around 70-85%; I am assuming the lower end of the scale for the sake of the argument, though it could surely be at or near the high end if necessary.) Because we would still need to provide energy during both part of the cycle in addition to storing the energy to be provided during the low part of the cycle, we need the energy produced during the high part of the cycle to be 0.5 + 0.5 * (1 / 0.75) = 1.17 of the energy we aim to provide over the entire cycle. Even if our storage method was only 33% efficient, we would still need only twice the energy to be used for the whole cycle.
Should we decide to put this idea to use, interesting opportunities arise. For instance, using a covered or closed system rather than one in which the liquid is exposed to the atmosphere would reduce the evaporation losses and improve on the 75% efficiency figure I've used. Using a liquid denser than water would reduce the volume of liquid required to store the required amount of energy, though perhaps at a cost of lower pumping efficiency if the denser liquid is also more viscous. If using wind power, one could use the mechanical energy of rotating blades directly to pump water without the use of an intermediate form of energy such as electricity.
Of course, just as with different types and sizes of batteries, pumped water is not the only form in which energy can be stored. If acceptable insulation is used, energy could be stored in a material in the form of heat and removed later on. Mechanical energy can be stored using the inertial effects associated with a flywheel, although eliminating friction to a sufficient degree is non-trivial.
We see, then, that energy from intermittent natural sources such as solar irradiation and wind can be stored when it's available to be used up when it isn't; essentially invalidating the argument at hand regarding the continued dependency on traditional power sources.