# Combine multiple variable energy sources for constant energy output?

Discussion in 'General Electronics Discussion' started by LDrechsler, Nov 27, 2011.

1. ### LDrechsler

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Nov 27, 2011
Hi,

So, I'm new to this forum...and electronics in general. I've done a little work with Arduino microcontrollers and have same basic knowledge of electronics (volts, amps, ohms, etc).

I have this project in my head that combines wind, hydro, and solar power to create a stable 120V, 60Hz output. The first stage of my project is to simply use a PV cell, home-made water wheel connected to a small hobby AC motor, and a home-made wind turbine connected to another small hobby AC motor.

Is there a pre-made device that can combine all the different sources into a single output? Could it be something a beginner might build?

Lorien

2. ### timothy48342

218
1
Nov 28, 2011
I am brand new to the forum, too. I am not an expert here by a long-longshot, but since your post is a few hour old, you need someone to say SOMEthing. (your post has interest to me becaue of my interest in extracting enery from nature)

I probably can't help much but... Who knows, maybe I will give some missinformation and someone will chime in to correct my error and end up helping you. HA! (Also a "bump" for you.)

I don't know of any existing device that does what you want. One thing I am thinking is that the AC from the hobby motors can not be directly combined with the DC from the solar source. (Also, they probably cannot be directly combined with each other due to frequency and phase issues.) One easy way to combine them all would be to just rectify everything to DC. Stick a diode in series with any AC source so that is provides "pulsed DC". (DC? that is ON[+V] then OFF[zeroV] rather than AC that is ON[+V] then also ON[-V].) Also a diode is series with each device would prevent any backflow from one device to another. By "backflow" I mean that for instace say the sun is shining brightlly but there is no wind. The solar cell might produce current that could be captured somehow but instead flows backward through your wind turbine forcing it to spin backward. (or more likely to sit still and just dissipate a bit of heat, but either way, energy from the solar cell is wasted by flowing backward through one of the hobby motors.)

Let's say you have a diode in series with every device, and electricity is flowing in one direction only. Sometimes plenty, sometimes not-so-much, sometimes pulsed. Pulsed DC can be smothed out a bit with a large capacitor(the bigger the better) or even a battery of some sort. Of course the voltage from any source that is going to charge up a battery needs to be high enough to do so. If your solar cell is only producing about 2 or 3 volts, then it won't charge up a 12 volt battery. A bank of multiple solar cells would do the trick. (I no nothing about your other hobby generators any their outputs.)

Assuming you can keep a deep cycle 12 lead-acid battery charged up, I think the next step would be to use an inverter to convert 12VDC to 120VAV60Hz.

BUT... (this is why I havn't done what you are doing, but it is not a "closed book". Someone needs to figure this out. MAYEBE YOU!) The voltage level from the devices you mentioned seems to low to work with. A single solar cell puts out less than 4V when the sun is shining bright. (multiple cells is series could put out whatever is needed) If the max voltage from the other genertors is very low it is hard to use. If you have enough volatge to recharge some sort of chemicle battery, then your golden. (12v or something else) If not, then where to go from there is tough, So, that is where I have been stopped. (I keep mentioning 12V because it is mainstream. People with boats like their radios to work, and so 12V deep cycle marine batteries are easy to come by. They are just like a car battery except that they are not damage so easily by being drained.)

I DO KNOW that there exist some circuits that produce a higher volatge DC output form a lower voltage DC source.

Bottom line is that you have got devices that produce energy and there has GOT TO BE a way to gleen that energy and put it to some use.

--tim
(So that is my first post. You are all getting to know me through my "fervor" for energy solutions.)

3. ### Harpy

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Nov 3, 2011
I have also pondered this question quite a bit, the simple answer is no there isn't a viable system currently available, otherwise alternative energy power supplies would be much more prevalent than they are currently.
The primary issue is that you have highly variable supplies, to combine them somehow they need to be synchronised and converted to the same form and potential.
Hydro is probably the easiest supply to control if you have a reliable water source to produce a constant output.
Solar is most common because of the universal availability and relative reliability, the new generation smart chargers can extract charge voltages from the cells even when they are only producing low voltages, this is done with pulse width modulation, so that a constant output voltage is created, but the current varies with the output of the cells.
Wind is the hardest, primarily because of reliability & the fact that available power is proportional to the cube of velocity, so if wind speed doubles then power available is quadroupled. So appropriate design and scaling is quite specific to the wind patterns of the site, they produce virtually nothing below their design speeds, then there is a relatively narrow band when good power is produced, then if the wind speeds up much more there is a danger of self destruction if the unit goes into overspeed.
Do not be deterred though, at the very simplest setup you can have independant DC battery packs for each setup and then just have a simple system to switch between the systems to go to the inverter for your AC supply.
Suggest you evaluate your site for suitability and chose one of these sources as a primary supply, then design around it and add the other two as you go along, have seen a lot of great successes, but even more rusting failures, not because of the units themselves, just because the systems weren't matched to the sites appropriately.