PV Gap

Lauren Said:

A question about Solar Panels. Please help!?

We Answered:

a battery provides DC voltage. most electrical devices use AC voltage. to change DC to AC you need an inverter .

the problem with solar power is that you have to be able to store energy for use at night or cloudy days. batteries are the best way to do this, but it takes alot of them--too many, in fact to be very practical given current battery technology. in addition, there is nothing "green" about a battery. batteries are one of the most polluting devices on earth.

Raymond Said:

Is there a way to store light, specifically the image in a mirror?

We Answered:

A hologram. It doesn't "store" the light, but it stores a pattern made by the light.

You can slow down or even pause light, though:

Scientists slow light:
http://curious.astro.cornell.edu/questio…

Scientists freeze light:
http://news.bbc.co.uk/1/hi/sci/tech/3308…

Marvin Said:

How do solar power systems for your house both on and off grid work mechanically?

We Answered:

On grid, yes you do need an inverter to send power to the grid, in fact you will require a standardized control module that will shut off your supply to the grid if the grid is powered down, it will not allow your system to send power below the voltage on the grid, or out of phase with the grid.

You can have batteries even while on grid, to keep your own home powered up while the grid is down,

The size of inverters you need is based on your generating capacity if you are on grid, but will be significantly greater off grid. When you use batteries they increase your amperage compared to just your panels.

Panels are an array of cells.

Photo voltaic cells have a semiconductor that allows electrons to flow only in one direction, and for instance aluminum foil plates that kick electrons out, ready to travel in which ever direction they are allowed.

Alternatively concentrating thermal collectors create steam to power a steam engine of some kind, often a turbine. In places that have lots of clear sky concentrating thermal collectors are very effective.

Direct current dc moves in one direction, the way a battery and a solar panel create it.

We have designed and built our houses and factories etc to use AC, because AC converts from one voltage to another readily, and converts to DC.

Voltages both AC and DC are all open to design criteria. Normally solar panels will deliver some multiple of 12 volts to the battery or to the inverter. Mostly 12 and 24 but this is not cast in concrete.

How much battery power do we need off grid? If we move all of our power use to daytime, not much. We can do a lot of that.
But almost always we design things to allow us to ignore the fact that we are using solar power.

Battery storage can be as costly as solar panels when we plan to use all of our power from batteries. To cut down on costs we use too few batteries but add more as we find that to be needed.

Inverters need to be large enough to carry the largest concurrent load, which again can be reduced by having intelligent load switching mechanisms, but it is more economical to buy a single inverter large enough to carry most of our loads and a second that stays shut off until it is needed.

It does not make sense to try to go for all DC appliances. It does not make sense to heat water with solar electricity if we can use thermal solar.

Hugh Said:

can photosynthesis be used to produce energy?

We Answered:

Your question could be, "Can sunlight be used to produce energy?" Which of course is yes with solar panels. The reason I wanted to change the question somewhat is because the idea of producing energy is the correct question, but how and which ways are the best to do so?

On NPR they discussed experiments in which the carbon dioxide formed from burning coal was captured, not with alkali to produce a carbonate to store somewhere, but with water and to grow algae in sunlight. While that helps to reduce the carbon dioxide in the atmosphere, algae are not exactly the easiest thing to use to power your automobile. That will always be problem with any photosynthesis system. You will have captured the sun energy in reducing carbon dioxide into sugars and other other organic compounds. However, you still need to process this biofuel into a more convenient fuel.

As an alternate, you could capture the sunlight into electricity to electrolyze water to generate hydrogen. Then you could use a hydrogen technology or parlay it into a liquid fuel.

So, lets think more futuristically, what we need is a method to capture the energy of sunlight and make a direct conversion into a safe and usable form of energy and in a high quantum yield (the fraction of the sunlight that becomes stored energy). There are patents describing the conversion of carbon dioxide into methanol by electrolysis. However, I don't know that any of these are at a commercialization stage yet. In their raw form, they are just using electricity from anywhere (solar panels, wind farms, nuclear, or coal powered), but imagine if someone could discover a way to harness plants (or their chemistry) to make methanol without the cells and other parts that make the cells grow, but may not be needed to produce a fuel.

Sarah Said:

Solar Powed Shed connecting battery to flood light?

We Answered:

You will be running ac from inverter, so there's not much voltage drop going to happen. Your inverters going to eat up your battery pretty fast, I think.

Julio Said:

Height Adjustable Roof Racks for Solar Panels?

We Answered:

doesn't look too useful to me.

First of all, solar panels are very expensive, what are you doing to prevent it from being stolen?

Second, this pivots only a small angle in one direction. You need two degrees of freedom and the ability to pivot to at least 45 degrees in any of 4 different directions.

Third, the added wind resistance when raised will offset any power gained.

Fourth, what is controlling the adjustments?

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