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Power conditioning for Micro-Generation

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Hi everyone,

I haven't been on for a while, but the time has come for my final year (BSc Elec Systems) Project and I have an idea. The basic outline is as follows:

A power conditioning circuit to convert a wide range of input voltage (approx. 1.2v - 50v AC or DC) to a stable 12V DC. It won't be very high power, perhaps less than a watt per module but many can be paralleled together to produce higher currents at 12V. The modules are connected together through a 12V connection running next to the standard AC mains supply. Possible sources if energy include (micro) wind, solar, peltier cells, kinetic energy harvesters on doors or mats etc. Low voltage DC is safer, easier to connect together as only the voltage needs to be matched to be compatible and there are lots of 12V DC appliances that can be powered from this already on the market. While AC needs to have the phase, frequency and voltage matched to connect multiple sources.

I plan to use a buck-boost topology switching power supply to step-up the input voltage to around 100v then back down to regulated 12V. I have found a circuit (attached) from a switching regulator LM5001 datasheet which looks very similar to what I want to do although I think there will need to be a rectifier on the input to convert from AC or either polarity DC.

Basically I wanted to run my ideas past some people with more experience in power supplies etc. Any suggestions or things to avoid?

Thanks in advance,

Jules
 

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mneary

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There are no similar devices on the market, for good reasons. Keep reading.

For an AC input, a Schottky bridge uses another volt (a bridge effectively has two diodes in series at all times.). Even at 12V input, it steals 8% of your tiny power input. At 1.2V input, there goes 92% of your power.

You can build it for maybe $10, or $5 in large quantity. Half a watt (24 hrs, 7 days) is 4.38 kWh per year. If your totally free, heretofore untapped, power source is available 10% of the time, the circuit won't pay for itself for at least 82 years.

Since it only handles $0.06 per year worth of electricity, the recoup of investment is very slow.
 
OK, so a single unit would be completely pointless, but my idea is to use a pile of them all contributing a small amount. Ultimately to produce a 12V DC main next to the 240V AC so that appliances that require low voltages don't all need an individual switching power supply on standby drawing from the mains. There is nothing stopping me making different power rated units so a larger solar array or wind turbine can be connected.

So the higher the voltage, the better as the voltage drop across the schottky bridge will be less in comparison.

I think it will be a proof of concept - that a low voltage socket available in the home will be easier to interface with than the high voltage mains.
 

mneary

New Member
So the higher the voltage, the better as the voltage drop across the schottky bridge will be less in comparison.
What is your new lower bound as inpt voltage goes? If you deal only with sources > 13.8V you should be able to design an efficient buck converter that's a dollar less than the SEPIC pictured.

In my calculation for value, I used only one unit as an example. 1,700 of them could 'save' up to $100 per year. Maybe you could build that many for $15K total.
 
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