Making multiple sources play nicely together

permaculturegeek · January 2016

Hi,
Where we live, redundant power sources are essential - we have a lot of days of low sunlight (aka fog - we're not in Arizona!), and a hydro source which is vulnerable to storms and isn't 100% dedicated to our house.
So, the solar system is fairly new (praise be to replacement insurance policies!) and sends through between 10A and 15A when it's sunny. (Our batteries are 12V, 500AH capacity). It uses "standard" solar cells because everyone ignored our suggestions that amorphous cells would perform much better in our environment. The solar is on a Wellsee 50A solar controller (room for expansion!)
The hydro has a long cable run, since it is equidistant between two houses. So it has high cable losses. Typically we can get a background 2A 24/7 (leaving enough pressure for other users on the 1.4km pipe) or about 6A if we hog the water. The hydro is controlled manually - direct connection to batteries, and we walk up and turn the water on and off. FYI, hydro and wind power cannot run through a solar controller, because those controllers simply disconnect the load when the battery is full - and if you remove the load from a hydro or wind generator it spins free and wrecks its bearings fast.
Of course both systems are protected by diodes to prevent reverse voltages.
With these figures, the solar does the lion's share of the charging, with the hydro as backup, or to keep things ticking overnight. We have markedly less power to play with over winter!

Our problem is, that if the hydro is running, it puts out a floating voltage sufficient to charge the batteries (the voltmeter at the pelton wheel often reads over 15V). The Solar controller sees this voltage as the battery voltage, so it stops charging. If we go to town in the morning (as we do several times a week) it may well be cloudy/foggy enough to have the hydro on, so we risk missing out on all the solar power if the sun comes out (as it did today) or getting inadequate power from solar if we turn the hydro off and it stays sunny.

How can we isolate these systems from each other so that they can work together? - without spending a fortune!

South Africa · January 2016

Two thoughts pop to mind, if out hosts do not have solutions:
1) I read while back that Morningstar Tristar controllers can operate together, when each are connected to their own source, and the same set of batteries. They will work together and not debate who charges first: http://www.morningstarcorp.com/products/tristar-mppt/
2) Measure the incoming current/Volts, if X, relay goes on/off. That way you disconnect that source from feeding power, favouring the other source.

permaculturegeek · January 2016

South Africa said:
2) Measure the incoming current/Volts, if X, relay goes on/off. That way you disconnect that source from feeding power, favouring the other source.

...except we can't just cut off the hydro. My idea for a hydro controller (at the pelton wheel itself) is a device which measures the voltage of all the batteries connected, sends power to that which is the lowest, and if all are ok, operates a voltage-contolled irrigation valve to shut the water off. I have met someone who thinks he could achieve that (Hopefully to IP66 ruggedness!). Dodgy to rely on analog data over 100m of cable - probably needs digital meters talking to each other by radio - not cheap!

Come to think of it, that would see the solar charging voltage when the panels are going, and not send hydro to that set of batteries.

vtmaps · January 2016

I am not familiar with the Wellsee controller. I presume it uses the standard bulk-absorb-float renewable energy charging protocol. In this charging protocol, the controller will push as many amps as it can into the battery until the battery voltage gets up to the absorb setting (usually around 14.4 volts or a bit higher). At that point, the battery is "pushing back" on the controller and you cannot get more amps into the battery without raising the voltage. If there are multiple charging sources, the controller will stop pushing amps into the battery when it sees the voltage go higher than its absorb setting.

Your scheme to use a voltage controlled valve to shut off the hydro might be workable, but where are you measuring the voltage? I suspect that you will need a small (5-10 watt) solar panel to control a relay... and adjust it so that it is activated only at a certain minimum insolation.

Another problem is that those valves can draw a fair amount of power (you need to decide whether to use a normally open or normally closed valve).

--vtMaps

South Africa · January 2016

Permaculturegeek, you said " The hydro is controlled manually - direct connection to batteries ...". So I thought it can be done battery side. If solar input is X, then ignore hydro. Using a relay, at night, solar incoming is zero, or on stormy days, volts in are low, so relay switches and uses hydro until solar is up again.

Relay is powered by solar panels in other words.

Or am I missing the plot totally?

vtmaps · January 2016

South Africa said:

on stormy days, volts in are low, so relay switches and uses hydro until solar is up again.

Relay is powered by solar panels in other words.

Are you suggesting that voltage be measured on the panels? If so, that won't work... the panel voltage will be the battery voltage (with a PWM controller) or higher (up to Voc) with an MPPT controller.

What OP needs to do is control the relay by the solar panel's potential to make power. OP needs to measure the current from the array under load to know if there is enough power to turn off the hydro. It would be much simpler to just buy a small 5 watt panel to power the relay. When there is enough sun on the 5 watt panel to close the relay, the hydro would be shut off. With a simple resister to adjust the sensitivity, the OP could switch off the hydro at any insolation level he chooses.

--vtMaps

South Africa · January 2016

vtmaps said:

Are you suggesting that voltage be measured on the panels? If so, that won't work... the panel voltage will be the battery voltage (with a PWM controller) or higher (up to Voc) with an MPPT controller.
--vtMaps

Interesting. If I measure the voltages before the controller at night, they are like +-3v.
Batt side of the controller it is the batt volts as you say.

zoneblue · January 2016

permaculturegeek said:

So, the solar system is fairly new (praise be to replacement insurance policies!) and sends through between 10A and 15A when it's sunny. (Our batteries are 12V, 500AH capacity). It uses "standard" solar cells because everyone ignored our suggestions that amorphous cells would perform much better in our environment. The solar is on a Wellsee 50A solar controller (room for expansion!)
The hydro has a long cable run, since it is equidistant between two houses. So it has high cable losses. Typically we can get a background 2A 24/7 ...Our problem is, that if the hydro is running, it puts out a floating voltage sufficient to charge the batteries (the voltmeter at the pelton wheel often reads over 15V). The Solar controller sees this voltage as the battery voltage, so it stops charging.

Theres a number of things that need clarification there. First, batterys accept charge, they are the total arbiter of what goes in to a battery. This is assisted by the charge controllers in use. In normal application you would have one CC for the solar and a second for the hydro. You would set both devices to have the same voltage setpoints for absorb and float. If for whatever reason this is not the case then the two charge sources will tend to argue. However assuming the controllers are vaguely sensible / conventional, then all that will happen when one source takes the battery to a higher voltage than the other controller is set up for, is the other controller will go dormant. Thus no fancy work arounds should be required, just gear that conforms to normal practice.

So, wed better have complete specs for the entire system. I think we can suggest a lot of improvements for this setup. It sounds like:
- you are trying to run 12V from the turbine to the battery. Thats a recipe for severe voltage drop, and is completely avoidable because most peltons put out higher voltage AC, which is usually rectified and transformed at the battery shed. There are a few turbines that are native "12V", but they are more toys..
- running a battery voltage of 12V for any kind of full time off grid application is no longer done. 24 or 48V systems are now the norm, as they allow smaller cables, smaller Ah banks, and smaller electronics all around.
- cable loss calculations will turn up some interesting things here i think.
- the controller for the hydro has to factor overspeed governing, to protect the turbine from spinning itself stupid when the there is no load on it. Historically, this was done by using a shunt controller and a diversion load. Now adays high voltage controllers can also be used.

Sorry if this is not answering your quesiont (and actually sounds kinda abrupt), but its given in the spirit of lets see how we can bring this system into a happy working state. This forum has a lot of combined experience.

zoneblue · January 2016

Wellsee, like this one?
http://www.e-bluelight.com/goods-66-WELLSEE+WS-MPPT60+50A+1224V+solar+battery+charge+controller.html

Its younger brother doesnt inspire much faith:

https://www.youtube.com/watch?v=umRNiJ1oLwo

Ethan Brush · January 2016

+1 on what zoneblue said. Multiple sources with multiple charge controllers are usually not a problem. I don't understand this:

permaculturegeek said:

Our problem is, that if the hydro is running, it puts out a floating voltage sufficient to charge the batteries (the voltmeter at the pelton wheel often reads over 15V). The Solar controller sees this voltage as the battery voltage, so it stops charging.

Sounds like using a single diversion controller would be a good way for you to go.

vtmaps · January 2016

Ethan Brush said:

+1 on what zoneblue said. Multiple sources with multiple charge controllers are usually not a problem.

Sounds like using a single diversion controller would be a good way for you to go.

I think the OP is using an unregulated hydro source for charging.... it also sounds like there is limited water supply, so when hydro is not needed the OP would rather cut off the water than produce and divert the power.

--vtMaps

mike95490 · January 2016

For Hydro, you need to use a motor controlled butterfly valve. Sorry.
A regular irrigation valve slams the water OFF. Sprinkler systems can take this, but hydro systems use higher flow and pressures and the hydrostatic shock will blow the pipe apart. Maybe you can come up with some sort of staged 4 parallel valves, controlled by a timer (no flow allowed in sunlit hours) and enable/disable each valve 3 seconds apart to reduce the shockwave,
Even different brands of good charge controllers work well together, Midnight and Morningstar are both used in my system

zoneblue · January 2016

And if its in a 3 or 4 inch line, whatever the valve its going to cost some serious biscuits.

Making multiple sources play nicely together

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