function of a voltage regulator

6 Posts
Dec 30, 2008 05:46 pm
function of a voltage regulator

If I place a voltage regulator between a micro-hydro generator and a battery bank, does the regulator lower the voltage and supply a constant voltage to the battery bank?

thanks
 
Dec 31, 2008 04:55 am
Re: function of a voltage regulator

Without the mention of specific equipment I can only give a generalized answer.
It depends. Not all charge controllers and micro-hydro genny's are created the same.
In order to have a constant specific voltage going to a battery bank from a charge controller fed by a source that can fluctuate, there would need to be a resistor bank of some sort, as well as a means of monitoring voltages and, the ability to automatically add or take away resistance as needed to maintain the desired voltage/amperage.
 
6 Posts
Dec 31, 2008 09:20 am
Re: function of a voltage regulator

To be more specific, I want to connect a Auqair In Stream Generator to a DC water heater element using a DC-DC converter (like the Buck Booster PST-DC/2812-8) between the generator and the element.

I'm trying to find a way to eliminate batteries.  The power from the Generator will only be used to heat water.... nothing else.  I need something between the Generator and the dc heating element to buffer the charge.  Since the generator provides power 24/7/365, I don't need a reserve power source.


 
163 Posts
Dec 31, 2008 12:52 pm
Re: function of a voltage regulator

Roger,

Heater elements are quite simple. They do not care about voltage levels or if it is AC or DC current passing through them. Current passing through any resistor will create heat. For safety purposes, you may want to pickup an AC heating element from a local hardware store and replace the DC element that you currently have with that. They will have a rated wattage, which tells you the amount of current they will draw depending on the voltage placed across the two ends of the element.

John
 
6 Posts
Dec 31, 2008 03:46 pm
Re: function of a voltage regulator

John

Thanks for the help!!

Are you saying that I should use an AC heater elements rather than one of the DC units?

If I understand you correctly,  I can hook the hydro generater (12V - 120W) straight to the element without a
DC-DC converter to assure a constant 12V.  If so, that is nirvana.

Roger
 
163 Posts
Jan 2, 2009 10:53 am
Re: function of a voltage regulator

Roger,

I was assuming that your generator was AC. My bad.

Your 12V hydro generator will work just fine on a 12V heater element without the need for any buck booster.

However, I am once again making the assumption that your 12V heater does not have any sort of electronic controller in place that requires 12V, and that the disconnect is some sort of thermal switch that will cut the 12V supply to the heater element once the water reaches a certain temperature.

John
 
6 Posts
Jan 2, 2009 12:53 pm
Re: function of a voltage regulator


Your 12V hydro generator will work just fine on a 12V heater element without the need for any buck booster.

However, I am once again making the assumption that your 12V heater does not have any sort of electronic controller in place that requires 12V, and that the disconnect is some sort of thermal switch that will cut the 12V supply to the heater element once the water reaches a certain temperature.

John

Thanks John    Your answer leads me to my next two questions:  a) since the voltage & wattage from the hydro generator may vary slightly, what wattage should the element be?  I have found DC elements from 20W to 600W.  The generator should produce a max of 180W.

b) Once the fluid in the first water heater reaches a set temperature, I want the charge to be diverted to a second water heater DC element.  What type of temperature controlled relay  switches would work in this type of application?

Thanks
Roger
 
Jan 4, 2009 07:49 am
Re: function of a voltage regulator

That does clear things up quite a bit. You have a water powered genny that produces a nominal 12 vdc and you want to dedicate that electric power to 12 vdc water heater elements only.
There is no need for the dc to dc converter unless you were to use a 24 vdc genny on 12 vdc elements trying to overcome a line loss because of an unusually long wire run. Is this the case? How long will the wire run be from genny to elements?

As for which size element would be best...
This would have to be determined by the highest amperage anticipated but you don't want to size it to big. It may take a little experimentation. What is the manufacture rating? It would seem that this is proportional to water speed. Do you know your water speed?
Example; if the genny consistently produces 8 amps at 12 volts nominal, then there is a possibility that a 240 watt element may "act" as a dead short and prevent the genny from spinning but this is the smallest element I could find. Also, depending on the size of the water heater tank(s) and hot water usage, you may not need a thermostatic switch but the tank(s) should have a properly working T/P valve that can vent safely without harm to personnel or property. A whistle up high maybe, like the old steam boats. Too much T/P the whistle blows releasing T/P, the tank "calls" for  make up water, etc., etc.. As for the relay you mentioned, if it were me, I would wait and see just how well the one preformed first but if your insistant on having two tanks, each with one element(?) it will take a transfer relay rated for 20 amps dc. There are a couple of ways to achieve this. Ideally you would not want a transfer relay with a coil that would stay energized to maintain current to one or the other element. This could get costly. It might be more cost effective to utilize one larger tank. It will all depend on several factors such as those I mentioned above.   
http://www.survivalunlimited.com/diversionloads.htm
http://www.whistleman.com/html/how_whistles_work.html
 
351 Posts
Jan 4, 2009 01:11 pm
Re: function of a voltage regulator

I think Roger needs to clarify what he is attempting with the two water heaters.  How much water is he trying to heat, How much of a temp rise is he looking for, how much water is drawn out per day (and replaced by cold water), etc.
Assuming 60 degree F. water to be heated to 120 degrees, there is only enough power for roughly 15 gallons/day.
The second water heater may be out of the question.
 
163 Posts
Jan 5, 2009 10:23 am
Re: function of a voltage regulator

Roger,

Maximum power transfer takes place when the resistance of the load is the same as the internal resistance of the supply. Here is a quick review of the math:

Power (measured in watts) = Volts(V) * Amps (I)
Ohms Law: Voltage(V) = I(current) * R (resistance)

For maximum power transfer you want a 180 Watt heating element.

A 180 watt generator means that you will be producing 15 amps of current at 12 volts. The resistance of your heater element will therefore be 12 divided by 15 (R =V/I) or less than 1 Ohm. This is a very low resistance, so you want as large a wire as possible from your generator to the heater element otherwise a significant portion of the 12 volt output will be "dropped" across the wire leading to the element thus reducing the power transferred from the generator to the heating element.

Ideally you would like the entire 12V of the source generator to be across the heating element, but if for example the total resistance of your wire run is 12/15 ohms or exactly the same as your heating element then only 6 volts of the 12 volt source will be "dropped" across your heating element "load" and the power transferred will only be 6(V) * 15(I) or 90 watts which is only 50% of what your source generator is producing. In practice it will actually be less, but I don't want to make the math any more confusing.

Your second question is a bit difficult to answer without more details on your setup and what you are trying to achieve.

John
 
6 Posts
Jan 6, 2009 10:45 pm
Re: function of a voltage regulator

What I WANT to do:

- Hydro generator will produce 24V @75W - 90W depending on how much rain feeds the stream.
- Power will run to our house 120' from generator (I have not attempted to determine wire size yet).
- Power will run directly into a dual contact thermal-relay-switch. 
- Normally the switch will feed a 60 gal. water heater (A) with dual heating elements.  The bottom element, tied to the relay switch, will be a 24V-100W element....the top element will be a regular 110V element.
- (A) is filled with glycol to be used in a closed-loop radiant floor heating system.
- When the temp in (A) reaches 120f, the switch will transfer the current into a domestic water heater (B).  The bottom element in (B) will be 24V and this is used as the dump load.
- When the temperature in (A) falls below 100f, the relay switch will redirect the current back to (A).
- We do NOT want to use batteries in the system, but I realize that I may have to.

My primary concern at this point is the heating element.  The volume of water flowing in the generator system will vary when it rains, so the wattage output will fluxuate.
This may require the batteries to assure the element receives proper wattage.  Correct?Huh?

Also, I have found a relay switch for this application.

Thanks again
Roger
« Last Edit: Jan 6, 2009 10:51 pm by Roger Leslie »
 
163 Posts
Jan 7, 2009 12:30 pm
Re: function of a voltage regulator

My primary concern at this point is the heating element.  The volume of water flowing in the generator system will vary when it rains, so the wattage output will fluxuate.
This may require the batteries to assure the element receives proper wattage.  Correct?Huh?

As stated previously, your heater element does not really care if it is receiving the proper wattage (current actually). You only need to be careful that you do not give it more current than it is rated for otherwise it may burn out.

If you have a 24V 100W heater element then it has a resistance of approximately 6 ohms and this means that it will consume 100 watts of power when 4 amps of current flows through it.

The 4 amps of current comes from 24volts being dropped across 6 ohms. I(4) = V(24) / R(6) and Power 100W = Volts(24) * Amps(4).

If your generator "pushes" less than 4 amps of current through the element then its just not going to get as hot as it possibly could. This is akin to turning down the amount of gas flowing to a burner by adjusting the knob on the stove. The water in the kettle will still boil, its just going to take longer. However, if you push 8 amps of current through that same element then it may burn out.

You may want to double check that everything is 24V.

John
 
351 Posts
Jan 7, 2009 01:32 pm
Re: function of a voltage regulator

Oh my gosh,  it’s the “Jack Rabbit” in stream generator. I didn’t realize that they were still available.  The US distributor quit handling them some time ago.

If the company hasn’t tweaked the machine or redone their production curves, you will find that they are optimistic.  Don’t be surprised if your actual production is about 15% lower than published.
Also, are you working with measured stream speeds, or are you estimating them ?  If you are estimating, I would suggest you measure, now.

You are building a complicated system to gain the heat of about a 75 watt light bulb (maybe 60W ?).
It is not enough to heat your house, or your domestic water. So it will take coordination with the 110v system in both tanks.  By removing the second element of each (to install the 24V) you are dropping the recovery time/ultimate daily capacity of both systems.

I don’t like generating electricity to heat water, at least not when direct solar heating is viable. But if I was too far north or had some other compelling reason to do it, I would install a 10-15 gallon tank in front of my domestic water heater as a preheater. Use all my generated power there. If the tank ever reached max temp and the thermostatic switch opened, a diversion load controller (or other relay scheme) would shunt the power to a second heater element in an outside water tank.  With normal hot water use, the diversion would never happen. It would only kick in when you are gone more than a day. If you are going to be gone longer than a day or two, shut down the hydro.

By using all the power as preheat to your domestic hot water heater, the hot water heater will automatically, use that much less energy.  You will get full benefit of the energy, without the complications of trying to transfer it between two systems, or coordinate it with the 110V systems.   

Ken
 
6 Posts
Jan 7, 2009 08:42 pm
Re: function of a voltage regulator

I want to thank all of you for the excellent information!!!  You have been extremely helpful!!

After running the numbers, even if I can achieve 80% efficiency, it will take over 16 years to get a return on my investment (after tax credits).  So this brilliant idea is going into a rather large pile of my other brilliant ideas.

For those who have suggested a solar water heater, I agree that it would be a great idea.  Unfortunately, no one location on our land gets more than 3-4 direct sunlight during the winter.  We live in a narrow valley next to a beautiful stream.....with very little head.

Thanks Again
 
Jan 9, 2009 07:43 am
Re: function of a voltage regulator

Don't give up Roger! Theres more than one way to, err, well, skin a cat. Not that I go around skinning cats or anything. Any way the point is, as Mr Hall pointed out, there is other options. His being probably the most cost effective. There is still the issue of that wire run. I am sure Alt-E Store has a chart or something to look at that will allow you to determine wire size and cost. Have you considered 48 volts nominal?
 Another option that comes to mind, albeit not as cost effective, yet, is to produce Hydrogen gas as close as possible to the "stream genny." Then in turn store and utilize the Hydrogen as an energy source.
A place to start.

http://www.geocities.com/hydrogenpower1/experiments/simple_electrolyzer.html
More to read,
http://www.h2eco.org/links.htm
and still more.
http://www.hydrogen.gov/
 
351 Posts
Jan 9, 2009 03:40 pm
Re: function of a voltage regulator

3-4 hours of winter sun, particularly if it is near mid-day can still give you a surprising amount of heat gain for a hot water system.  Mid summer, even more.
You might want to spend a little time on the subject. If you are in a cold climate, possibly something like this.
http://store.altenergystore.com/Solar-Water-Heaters/Climate-freezes-Closed-Loop-Systems/Closed-Loop-Systems-for-1-4-People/Closed-Loop-PV-Powered-w-Tank/AET-PV-w-80-Gal-Tank-64-SqFt-Collectors/p172/
In warmer areas, you can get by with a less expensive option.

At the very least, you will have learned something and have another bright idea for your pile.  But you may find it to have a fairly short payback, particularly since you seem to be all electric on your hot water.

Ken
 
3 Posts
Jan 12, 2009 09:35 pm
Re: function of a voltage regulator

You know, trying to heat water with such a small generator just doesn't seem sensible. That's a pretty expensive way to get the job done when you consider the typical hot water tank has a 3000W element. I don't think you'll be happy with the extremely modest amount of hot water produced. I'm planning to install the very same generator in an existing photovoltaic setup, to keep the battery bank charged and minimize the use of the backup generator, and here the modest generator output is actually significant to the system. If I were you I'd think about a larger storage tank coupled to a coil in your woodstove's firebox (I'm assuming you have a woodstove?) which would produce tons of hot water for less investment. I'm doing to do that later this year. Using electricity to heat air or water is just about the worst thing (economically) you can do. Just my two cents worth. Good luck!  Paul
 
1 Posts
Jan 13, 2009 02:30 pm
Re: function of a voltage regulator

Dear Roger,

     The effect of a "voltage regulator" will depend upon just what it IS that we are calling a "voltage regulator"
I think so.
     A battery really likes a steady, constant, even-ish current until full, when it's terminal voltage will rise to an easily discernable "fully full" voltage.  What this voltage is depends upon the battery, of course.  A "12v" car battery will charge at about 12.5 volts for ages, and then rise to about 14.- when full.  One has to become used to watching these things.
    "Regulators"
     ----------
    Most "regulators" simply "saw-off" so many volts, which if you multiply by the current going thro (Amperes), you know the power which the regulator is wasting into heat for you.  If you use this sort of thing in series between the generator and the battery, then when the charge current will vary a lot as the battery charges.    The situation being - by Ohms Law - that the current in the circuit will be determined by the Generator volts, minus the battery volts, minus the volts wasted for you by the regulator  e.g. 23-5-11 or 7 volts divided by the total resistance of the circuit generator (5 Ohms, say) cable -
0.25 Ohms say, and battery .1 Ohm, say which is a total of 5.35? Ohms, so the current would be 7/5.35 Amperes in this instance.   Generally, the sum is  I (amperes) = Sum of voltages in the loop, divided by Total resistance of the loop.  It's very simple, but we need to actually KNOW what these mysterious components actually ARE - in real electrical terms rather that techno-jargon !!
      Better - and far cheaper than a "regulator" is simply a resistor of a suitable value - Ohms  - and heat dissipation rating - Watts.   This will give a more constant charge "profile".
      A hydro-electric plant I imagine gives a pretty constant output (compared to wind, at least) and so you need to choose a battery as near as possible - but lower of course - to the usual voltage of the generator.  Next decide what a comfortable current for the generator is, then do the sums:
    R will need to be (Genvolts - Batt.volts)/Happy.current
     You may find a very long and not so fat, cable will do the trick.  I hope you have a reasonable volt and amp-meter.
   Don't forget a "diode" of suitable amp rating, to stop the battery turning the generator if the brook gets low !!
     I have been doing Wind-energy for about twenty years and if you send me an email, I can send you some pretty serious info and picture or two.
         Best wishes + Happy New Year
                 G. 'bert Vaughan,
 Nikiup, Veliko Turnovo, Bulgaria   bert.windon @ gmail.com
 

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