PV Gap

Becky Said:

how is energy produced from burnin fossil fuels, solar energy, water power, wind energy and nuclear energy?

We Answered:

(1) Fossil fuels -- oil, coal, and gas plants all do the same thing. They burn the hydrocarbons to heat water, the water boils and releases high-pressure steam, and the steam spins a turbine, which creates electricity. Complaints? Sure, it's cheap, but it's messy and Al Gore told me so.

(2) Solar cells -- silicon wafers embedded within a transparent plastic are hit by sunlight. A photon of sunlight will hit a silicon atom and knock off an electron. This electron will drop into a circuit and race around the track on its way back to where it started. Moving electrons are the essence of electricity, so this is the direct creation of energy from sunlight. Complaints? It looks ugly on my neighbor's roof and I don't want to look at it, plus, you need a stupid amount of area to generate enough electricity to be worth it (which is completely false, but that's the belief).

(3) Solar reflection (steam) -- long, long rows of shiny mirrors shaped like open parabolas are scattered in more and more rows and rows. At the focal point of these long parabolic mirrors is a pipe full of water. The water will be heated by the focused thermal energy, and will move through the pipe to the point at which the water, and then a secondary step of "waste" steam will both spin up turbines and generate electricity. Complaints? Too much space (not true).

(4) Solar reflection (generator) -- many, many computer-controlled, movable mirrors with adaptive optics (they can change shape) are situated around a central tall tower. At the top of the tower is essentially just a boiler, but full of something like liquid sodium, not water. The mirrors focus the sunlight on the boiler, which can be heated to temperatures of 550 F or even higher. This high-temperature fluid is either pumped into holding tanks, or pumped itself directly to a heat exchanger. Whichever one of these occurs, they just create steam, like everything else, and spin up a turbine electrical generator. The benefit of these high temperatures that can be achieved, and the use of a high-temperature fluid like liquid sodium is that it will hold on to that energy for a much longer time than water, so you can actually continue to efficiently use solar power long after the Sun has gone down. Some people like to call these Solar Power Towers, because they like things that rhyme. Complaints? Too much space (not true).

(5) Water (tides) -- in areas of the world with very high tidal flux (big difference between high and low tides), like the Bay of Fundy in Nova Scocia, Canada (50ft or more), you'll build something like a wall across the mouth of the bay/whatever with openings in it. These will usually be circular with what would look like a really dense collection of strange airplane propeller blades. When the tide comes in it will move through the holes, spinning the blades. The higher the tide, the faster the spin. The spin is just once again the spin of turbine blades, or at least something that will be geared to a turbine core, and spin it in that manner. Complaints? Ugly and damaging to the ecosystem (which may legitimately be true, just to be fair).

(6) Water (deep current) -- you drop in HUGE turbine blades deep into the ocean along the deep continental shelf. These currents aren't fast, but they're very large, with a lot of momentum, which would once again spin the turbine blades to create electricity. This method, however is probably the least likely to ever happen. It's difficult to implement, and doesn't have any real superior advantage to make up for the trouble. Complaints? Too expensive for what you get (probably true).

(7) Wave -- you put hundreds of buoys the size of your dining room offshore, just about anywhere, because everywhere has waves. These buoys bob up and down with the wave, and this is one instance where there isn't a bladed turbine being spun (finally!). Instead, it's the pure movement of the waves that moves loops of copper wire up and down, side to side, whatever is happening with the motion, and creating electricity that gets wired back to shore. Now... this is still electromagnetic induction, but at least it's different than a spinning turbine. I love this method -- very efficient, powerful, and doesn't get in anyone's way. There are a couple of other wave energy-capture methods, but they're basically just experimental (save for one off of Scotland), and don't work very well. Complaints? It's ugly and will destroy the ecosystem (false, you can't see them from shore, and does nothing to the ecosystem).

(8) Wind -- Tall towers with very large (long and thin-ish) blades, only three or four at a time. Sometimes, these blades will rotate vertically around an axis, but most of the time, they look like a child's pinwheel and basically function the same way. The wind blows, the blades catch the wind, the blades spin, the spinning spins a turbine, and electricity is created. Complaints? Ugly, too

Ian Said:

how do you purify water without solar energy?

We Answered:

You can use iodine tablets, add a small amount of bleach, boil it, or use an ultrafilter.

Roger Said:

How can I boil water using solar energy using only a pan and metals?

We Answered:

Do you specifically want boiling water? Or do you want to cook with the solar radiation?

You can cook with a solar oven. Just google the words "solar oven" and you will come up with lots of plans on how to make them, and places that sell them.

I think solar ovens can get hot enough to boil water, but I'm not sure. They take about four hours to cook a meal, at peak sunlight time...a meal can be a whole chicken and vegtables.

~Garnet
Homesteading/Farming over 20 years

Dennis Said:

Can someone please tell me some good and bad things about saving solar energy in water or stone from one day t?

We Answered:

Solar energy, you meant, the heat that is stored in some insulated containers which contains substances such as water or stone? Why should there be anything bad in it? The rays of the sun that you are exposed to everyday has given you Vitamins and food from the plants that utilized it. Of course, you should not forget the sunburn due to overexposure, but that is nothing extraordinary. The solar energy turned electrical in your Storage batteries are no different from other Emf source. The good and bad will just stem from your handling of it.

Micheal Said:

Please and TY Solar energy can preheat cold water for domestic hot-water tanks. What quantity of heat is obt?

We Answered:

According to the listed reference, the specific heat of water is 4.184j/(g-degree C). 100kg is 100,000g.

Q = m*c*?T = (100,000)*4.184*(45 - 10) = 14.64*10^6 joules

If you use c = 1 kcal/(kg-degree C), the answer is:

100*1*(45 - 10) = 3500 kcal.

Jennifer Said:

What happens to your energy/hot water if you are using solar power and it's cloudy for several days in a row?

We Answered:

Most solar water heating systems are installed as a preheater to a backup water heater. The collectors heat the water in a super-insulated storage tank. The hot water output of that goes to the cold water input of a backup heater; electric, gas, oil, whatever. So on rainy days, the tank is insulated so it doesn't lose much of the heat that it made, but it may send 90 degree water to your backup heater instead of the 50 degrees you get from the city or well. That's 40 degrees less that the backup needs to heat, but still always provides hot water to the house. But on sunny days, your backup heater doesn't need to turn on at all. Many people actually turn the backup off in the summer.

Georgia Said:

How can you separate salt from sea water using solar energy?

We Answered:

Yes, just let the water evaporate in the sun and what's left is salt...and whatever else was soluble in it.