Off-grid hybrid solar/hydro system with diversion load to heat water?

[Shawn McCracken]

Hello,

We are a small NGO (Third Millennium Alliance (https://tmalliance.org/)) that has created the Jama-Coaque Reserve in Ecuador’s endangered Choco rainforest. We have a small research station in the reserve and added a small hydro-electric station a couple years ago. To make it easy we chose a Turgo 500 watt hydro generator that outputs 120 VAC. We soon realized we needed more power and added a 24v-300Ah battery bank (4x Sunbright 150Ah gel batteries wired in series/parallel). To charge the battery bank we use a Cotek CX-2415 Battery Charger that plugs into the outlet from the hydro generator. The one problem we have is not being able to get through the peak of the dry season (~2-3 months) with continuous power from the hydro-electric generator. We have increased our head and created a dam to collect all the water but it’s just short of being enough. If we get some rain it will come back online for a few days and that’s it.

We’ve decided to add a couple solar panels to the system to get us through the dry season and maybe allow us to heat some water for showers (water coming out of the mountain springs is really cold!). What we are needing to know is how to design our hybrid system with a possible diversion controller to heat water. We already have a brand-new Aims Power 60 Amp Solar Charge Controller 12/24/36/48V. We plan to purchase two 365w/24V solar panels in Ecuador (maybe expand with 2 more in the future when we get a fridge). In my research I’ve found relatively little on setting up a hybrid system like this. I believe we should be able to connect the solar charge controller to the batteries with the Cotek charger coming from the hydro generator. Most of the year both chargers will be working to charge the batteries, so what settings should we use on the chargers to keep them from working against each other?

If we want to heat water with the excess power from the solar side of the system I know we need to add a diversion load controller (DELETED: change charge controllers). We are thinking to get a Xantrex C60 Charge Controller 60A that has a DC diversion mode (DELETED: and we’ll just sell the Aims Power unit in Ecuador). (DELETED: I understand we need to use a solid state relay with this setup). We are thinking we'll use a 55 gallon drum as a hot water tank. We don’t need hot showers just warmer, especially for our people doing research at night and needing a shower at 1 or 2 in the morning when they finish work. I realize that in the dry season when we lose the hydro generator we will have less water heating time.

We would appreciate any advice and recommendations the community has. Thanks for any and all you can provide us.

Thanks,

Shawn

[Rob Beckers]

Shawn, why not use a solar hot water heater? I'm pretty sure they are ubiquitous in Equador, I'd think locally made and reasonably cheap. In the dry season there should be plenty of sun, and it will be much more efficient in turning sunlight into hot water.

Regarding charge controllers and batteries: You can have multiple charge controllers all charging the same set of batteries. Nothing wrong with that. Each charge controller just sees the battery Voltage (it doesn't know what the other charge controllers are doing, and it doesn't matter). It will contribute based on its settings and the battery Voltage it sees. Just set them all up with the same bulk-absorb-float Voltage and let it rip.

With MPPT charge controllers cheap nowadays that's what I'd use. You can plug multiple panels in series, and run just one set of wires to the charge controller. We've had very good luck with the EP-Solar/EPEver brand. They are 100% Chinese, cheap, and with many hundreds sold proven very reliable.

-RoB-

[Shawn McCracken]

Thanks Rob! A solar water heater is an option we've considered but they are expensive in Ecuador, haven't found one for less than about $900. Transporting it to our little research complex might be challenging too. The road only gets so close and then you have to hike in and up a mountainside for a little bit. We figured we could do the diversion load setup for a couple hundred dollars.

Upon further research, I've found that we would hook the diversion load controller up to the batteries. But it doesn't seem like it will work to have the solar and hydro charge controllers connected to the batteries with the diversion load controller. I just can't seem to understand how diversion load controller and charge controllers will play nice with each other.

We were gifted a brand new Aims 60A MPPT charge controller and have sourced some fairly inexpensive 24V panels. We will get this up and running in October.

Thanks again!

Shawn

[Ralph Day]

Charge controller puts power into the batteries, diversion controller takes it out. While the diversion controller is dumping out the charge controllers are still putting power in...hence the dumping occurs.

Ralph

[Shawn McCracken]

Thanks, Ralph!

So how do you go about setting it all up so that the charger controllers aren't always charging in bulk mode (i.e. higher voltage) when the diversion load controller is dumping? I assume you want to avoid the continuous high voltage.

Thanks,

Shawn

[Ralph Day]

My previous post was a factor of my vast ignorance. I know how that's supposed to work, but have never setup or worked that way. My dump load control is handled by my Midnite solar Classic 250's (one for solar, one for wind) bought through our host's store.

The classic's aux modes actuate a 12vdc solid state relay. The relays energize 120vac outlets which I can plug heaters, fans, a water distiller or whatever into. The aux parameters are programmable for various conditions. I have mine set to actuate on absorb and float modes.

Someone should be able to help with the setpoints for your diversion controller. Sorry if I got your hopes up.

Ralph

[Shawn McCracken]

No worries, Ralph. I appreciate the response. Hopefully, someone can help with setpoints!

Thanks, Shawn

[Andy Rhody]

Real interesting:

Maybe set the Dump about .2 volts below the controller set point.

Example: 12 volt system.

Controller disconnects panels at 14.4 volts.

Diversion starts dumping at 14.2 volts..

That way the dump comes on just before the controller disconnects so the as Ralph said, while the diversion control is dumping, the charge controller is still putting power in.

This was a whiskey post.

[Shawn McCracken]

Thanks for a starting point and reasoning of where to start with the setpoints!

[Brian McGowan]

It is late so I am just going to throw this out there and come back later if you have questions.
First for making hot water consider just throwing 100' of black plastic tubing on the ground in the sun and pumping water through it from your tank to heat the water up.

For dump load take a look at this stuff. Read carefully. I have not used any of this but it is pretty straightforward and relatively inexpensive.
http://hydrogenappliances.com/batteryregulator.html

Water heater dump load
http://hydrogenappliances.com/dump.html

Lower wattage dump load water heater elements and controllers
http://hydrogenappliances.com/hotwater.html

[Shawn McCracken]

Thanks, Brian! I agree that the more passive water heating system is probably the way to go. Maybe even just put a separate solar pump on it to cycle water during the day. I appreciate all those links and will have a look. I just hate having excess power being generated and not used, when we have some uses.

[Brian McGowan]

I hate having excess power not being used also. I made and programmed an Arduino control processor to monitor and control my solar PV system. I was annoyed that charge controllers would choke down the panels to save the batteries so I made this to distribute energy once the batteries were charged to keep the panels and charge controller working as hard as possible.
Once batteries are charged to 16.5 volts for 5 minutes it turns on my inverter which feeds power into several circuits I have in the house to power things like my fridge, entertainment system, washer, chest freezer and computer room/modem.
This stays on until the voltage gets below 15 volts for 5 minutes.
If the inverter is already on and the voltage gets above 16.5 volts again it turns on a secondary load until the voltage gets below 15.5 volts when it shuts off.
Anyway, those links should provide some devices you can use to dissipate excess energy and if you get some kind of controller from them I think you can set it and should use what Andy recommended for setpoints. My guess is you will want the smaller elements as you only will have 2 panels up front. The #SJH24600 - for 24 volt heater ONLY 6" model on the third link about 1/3 of the way down will be a 600 watt unit.
You will have to work the math when you actually get what you are going to get and have it set up. I am sure if you have further questions you can come back here and everyone will help.
good luck