Pooling low DC voltage into high AC voltage?

This is a fundamental question and hopefully not in the wrong forum.

Question is:

Can multiple, small dynamo's (driven by small windmills) generating low DC current be accumlumated somehow into a single higher voltage AC current? I'm assuming that some sort of inverter is required but I'm not very electrically inclined.

The reason I ask is because I'm putting together some ideas to develop a prototype of sorts to test a theory of mine. I will elaborate more once I learn the fundamentals so I will at least know it is feasible.

Thanks,

W.E.S.B

The answer is no. An ac voltage is a sinewave while a DC is a flat line the line and sinewave go through potential functions with respect to time. If your trying to make hight votlage ac you might connect your alternators together and then use a inverter and step transformer to get your high voltage. I hope this answers your question.

Plenty of ways to get usable voltage AC from DC... as you said an inverter is the easiest route, but you lose a lot of power in the form of heat. A simple capacitor and diode bank can be used to bring the voltage up and then a few transistors to give you a sine wave, although it won't be a true sine.. it will be square. The caps and diodes are cheaper than a step up and you have barely any loss.

Again though, the easiest way is just use a standard inverter circuit. If you're investigating the use of windmills as an alternative energy source, you'd also really want to try and run as much off the lower voltage high current output as possible to conserve energy.

Why not just make the voltage AC to begin with. As others have said, you will lose a lot of power converting it. If you don't know where to find generators and this is why you are going with DC, just use any AC motor. It will give off current if you turn it.

Originally posted by scienceguy94
The answer is no. An ac voltage is a sinewave while a DC is a flat line the line and sinewave go through potential functions with respect to time.

I find this of interest, assuming that you mean by flat line as in a horizontal line with no variations of y, what are the potential functions? I can't imagine that there would be too many difference for DC since it is simply a flat line.

The device in electrical terms to change AC to DC or DC to AC is called a rectifier which you will find in a alternator. I had to make one AC to DC few years ago out of large diodes soldered in a square fashion for my 3 watt laser. Which it took a serious step up coil of something like 1250 to 1500 volts to light it up. Quite scary messing with high powered toys. Please be careful :p

A rectifier is just AC to DC. It cuts the wave in half so you end up with pulsed DC. Most devices dont care they see it all the same, but if you have a circuit that does care the best thing to do is run this choppy DC signal into a pair of transistors that open up a clean source.

W.E.S.B.,

I'm interested in what you're planning...I had a similar thought but with regards to domestic solar-power, the idea being that a whole street is fitted with panels to the roof of every property, and the DC current generated is fed into a neighbourhood DC/AC converter and then fed back into the national power-grid, earning the neighbourhood revenue.

That would be a LOT of solar panels...

The typical sized house would need almost its entire roof covered with panels to be self sufficient and off the grid. Consider a safe rule to use of having 1kW available per room. The excess energy would be needed to keep batteries charged for power when the sun is down.

A good system uses panels to provide power for lights, entertainment, and other low current needs. Air conditioning, blowers, and any other high current equipment would then be run off the grid.

the usa does have major problmes with its energy net and with every thing on it.
usa has a netvoltage of 110 v
europa has 230 v
the usa has got many cables on poles above the ground
Europa got every thing under ground with the exeption of the main powerlines from the powerplants to the places were the main powerflow is separated and delivered to the homes at 230 v.
the usa has a problem with out dated powerlines, and because of its 110v they have great fire hazzards .

Actually it's 220 coming in off the pole.

The 220 is then split into opposite phased 110 circuits. This allows us to power high voltage appliances such as clothes dryers and whatnot, while still giving us the lower voltage 110 for smaller devices.

110 is advantageous over the EU 230. 230 requires higher rated components and safety standards. 110 does not, making devices cheaper and simpler.

It's actually a nice thing to have the lines on poles instead of in the ground. When there's a failure, or a need to upgrade, you dont have to dig up someone's yard, house, street, ect.

And there is no fire hazard from the lower voltage. If anything the EU higher voltage is more dangerous as it is able to short across larger gaps.

Originally posted by scienceguy94
The answer is no. An ac voltage is a sinewave while a DC is a flat line the line and sinewave go through potential functions with respect to time. If your trying to make hight votlage ac you might connect your alternators together and then use a inverter and step transformer to get your high voltage. I hope this answers your question.

with an inverter you don't really need a step up transformer. your primary winding is center tapped with a small number of turns, your secondary winding has the number of turns needed to make the turns ratio correct for what ever voltage you want on the output. i.e. 12v in with 10 turns would need 100 turns for 120 v out

Originally posted by apc
Plenty of ways to get usable voltage AC from DC... as you said an inverter is the easiest route, but you lose a lot of power in the form of heat.

yes and no

linear transformers don't lose much untill they are loaded down and then as you approach a short on the output, the power used by the transformer goes way up.

in a ferroresonant transformer you lose about 100 watts energizing it at no load. if you use some of the extreamly low Rds on mosfets (about 10 each side is a nice start) you can virtually eliminate the power loss in your switching transistors. i've gotten down to less that 10 watts dissipation on the switching tansistors under 1kw load.

there's also a couple of advantages that a ferro has over linear transformers.

a linear can produce a sinewave output, but you have to do some fancy switching to achieve it. in a ferro instead of interlacing your e-i laminations you bundle all the e laminations together and mill a few tenths of an inch off the center leg. then when you add your coils and top it off with the i laminations you will get a signwave with simple switching on and off. infact a very pretty sinewave compared to what you get out of your wall

in a linear you short the output you also reflect the short to the input and if you don't detect it quick enough your switching transistors smoke faster than tommy chong and a joint. a ferro on the other hand, when a short is placed on the output the voltage folds back and only a fraction is reflected back to the input and your switching circuit doesn't go poof.

a linear also has to have output sensing feedback to control the switching circuit, a ferro on the other hand,also known as a constant voltage transformer, is self regulating so you don't really need any output sensing feedback. you just set your turns ratio to produce the desired output voltage and then for regulation you adjust your capacitor on the tank circuit

the only down side to a ferro is the amount of power needed to energize the tank circuit

Ah I hadn't even considered that! Excellent!