looking for advice on PV and Micro hydro AC diversion loads

Wilensky

New Member
Joined
Feb 10, 2022
Messages
4
Location
Kootenays, BC, Canada
I'm having a hybrid PV/mircohydro system installed to power an off grid camp/resort. I'd like to use any excess power to heat water. In a perfect world I'd like to run an air to water heat pump to do so.

based on my initial research i only see guidance of about running a dump load from the charge controller of which I'll have 1 for the microhydro and another 2 for the PV and from either I believe the dump load would need to be DC.

question:

Is there anyway to combine excess generation from any or all sources, bypass the battery bank and covert to AC to power something other than a restive heat element (i.e. the compressor on a heat pump)?


Apologies if this question is non sense, this is all pretty new to me.
 

400bird

Solar Addict
Joined
May 23, 2020
Messages
958
Do your PV and micro hybrid charge the same battery bank?

Depending on your other equipment you could definitely have something watching pack voltage or watching for a signal from a charge controller and turn on an AC load.

Dump loads are commonly DC, sure, but there's no reason you need to stick to that. I think an AC load might redefine dump load, but I believe you can make it work.

I believe with a DC dump load, it's set up so the load is larger than the possible current output of your PV or micro hybrid. Then Ohm's Law takes over and all excess power can be used.

With an AC dump load you can't close the loop quite so easily. You'd with either need multiple you could turn on in stages depending on how much excess power you have, or one large dump load. But, then you risk partially discharging the battery.

Seems like there'd be a lot of extra work involved to get it to work perfectly, but you could probably get close enough easily. But, not as easy as a DC dump load.
 

Wilensky

New Member
Joined
Feb 10, 2022
Messages
4
Location
Kootenays, BC, Canada
yes, the plan is for both to feed into a single battery bank.

if i understand correctly your first suggestion, having an AC load kick on based on SOC seems the simplest, but i'm concerned id over work the batteries (is this a thing?) and when the bank was not in bulk charge id still need to dump at the charge controller.

Partially discharing the battery to heat water is not an issue as i plan to provide hot showers to campers using the heat pump in summer. could you explain what you mean by having "one large dump load. But, then you risk partially discharging the battery."? The heatpump i'm considering has a input of 2.5 ish kW, which might be taking the concept of "one large dump load" too far...
 

400bird

Solar Addict
Joined
May 23, 2020
Messages
958
So with a DC dump load, you disconnect the microhydro from the battery and connect it straight to the load? (This happens internally to the charge controller ideally)
If your hydro is producing 100 watts or 2,500 watts it doesn't matter it all goes into the DC load and nothing more. I don't think there's any way to run a motor from a DC dump load. Many use it for water heating.

If you try to use an AC dump load, you would leave the hydro connected to you battery and turn on your 2,500 watt heat pump.
But, what if you're only making an extra 2,000 watts of power at the moment?
You'd end up pulling 500 watts from the battery.
I can't say if that would cause you an issue. Maybe you have the dump load run for 60 minutes, you'd pull 500Wh from the battery. Then, disconnect the dump load and that 2,000 watts of "excess" production recharges the energy you just used to run the heat pump for an hour, in 15 minutes!

But, if you've only got 100 watts of excess power the math gets rough. If you ran the dump load for 15 minutes, it would take 6 hours to recharge the 600 Wh your dump load just pulled from the battery.

Moving this extra energy through the battery will contribute to shortening battery life. Its unlikely to make a huge difference.
 

再生可能 エネルギー

Solar Enthusiast
Joined
Nov 28, 2019
Messages
187
The heatpump i'm considering has a input of 2.5 ish kW, which might be taking the concept of "one large dump load" too far...
Which heat pump do you have in mind? A 2.5kW seems to be a 15A type?

Note: I have been looking at various heat pump, but I could not find real technical information.
I was looking at some 5kW 240V (75 gallon - with a 3/4" water inlet)

It seems that the 5kW is the electrical heating that can be used to get quick hot water, but can be disabled.​
About the compressor, I could not find consumption information.​
I just imagine that the compressor consumption might be similar to a refrigerator or freezer?​


I would be very interested to know if you have any consumption and in-rush current information for your heat pump
as I would like to determine what kind of inverter I would need.

I'm having a hybrid PV/mircohydro system installed to power an off grid camp/resort. I'd like to use any excess power to heat water. In a perfect world I'd like to run an air to water heat pump to do so.
I'm curious to know in what part of the country and for how many months your resort will be open?

If open only during the summer, to heat water, I wonder if a gas would be more economical (using a big 100 Gallon propane tank).

Do you have an idea of the water consumption you need. I just wonder if an On-Demand (propane or electric) water heater
instead of a water tank would be simpler and more efficient. I believe that Heat pumps are slow to re-heat large amount of water.

By the way, are you completely off grid, in this case how much daily electrical consumption do you need?
Are you providing an electrical plug to each user for at least lighting purpose?

Since you may have only 6 hours of sun in the summer, how much battery storage do you have
to provide power at night and in case of cloudy days.

based on my initial research i only see guidance of about running a dump load from the charge controller of which I'll have 1 for the microhydro and another 2 for the PV and from either I believe the dump load would need to be DC.
question:
Is there anyway to combine excess generation from any or all sources, bypass the battery bank and covert to AC to power something other than a restive heat element (i.e. the compressor on a heat pump)?
My approach would be to charge the batteries first, and then to run the heat pump as long there is enough solar production.
So the idea is to have the batteries used only as a buffer in case of some clouds, and to keep them as full as possible otherwise.

But my situation might be a little bit different. I'm in a building where I want to use solar energy for lighting​
instead of using the grid to lower the elctricity bill. The daily consumption is around 15kWh, mostly at night.​
If the batteries are too low, I can switch back to the grid, something that might occur in winter when the days are short,​
with bad weather and low solar energy available, and longer night consumption.​
For the hot water, there are already two 75 Gallons water tanks in series using natural gas.​
The monthly consumption is about 300 Therms (at $2 a Therm), so something I'd like to improve.​

I plan to add an heat pump to pre-heat the water, using excess of solar energy, except maybe during the winter,
and use the natural gas heaters mostly when the demand is high.

I might run the heat pump as a supplement to pre-heat the water,​
using the grid, all the day long, or only earlier in the morning before sunrise,​
but I would need to perform some experiments to see if this would be cost effective.​
I plan to use a small inverter for lighting and a larger Inverter for the heat pump, that I could turn off.​

I don't have yet installed a heat pump, so the big issue that I have in my current design is to determine
the heat pump consumption, but heat pump documentations are very poor in this regard.
 
Last edited:

WYtreasure

It's not happy hour, I'm just like this.
Joined
Nov 23, 2021
Messages
1,692
Location
Thunder Basin Wyoming
I'm having a hybrid PV/mircohydro system installed to power an off grid camp/resort. I'd like to use any excess power to heat water. In a perfect world I'd like to run an air to water heat pump to do so.

based on my initial research i only see guidance of about running a dump load from the charge controller of which I'll have 1 for the microhydro and another 2 for the PV and from either I believe the dump load would need to be DC.

question:

Is there anyway to combine excess generation from any or all sources, bypass the battery bank and covert to AC to power something other than a restive heat element (i.e. the compressor on a heat pump)?


Apologies if this question is non sense, this is all pretty new to me.
Nice goal, and I do not find your question to be nonsense.

Would you mind adding your location to your Account Details? Knowing where you are allows us to offer much better advice. As the previous poster has implied, your lack of details makes it a bit difficult to efficiently assist you.
What kind of dump loads would you consider, if you know enough about them to answer that question? If you don't know that answer, it's perfectly understandable.

Can I get a 20' trailer in a beautiful spot and walk to a quiet fishing hole from your resort? 😃 🎣
 

12VoltInstalls

…myself everything do I…
Joined
Jan 18, 2021
Messages
4,253
Location
Vermont
The terms “diversion load” and “dump load” are a bit misused here.

You use a ‘dump’ constant load of some sort on hydro to keep the thing from free-wheeling and destroying itself. You can diy a controller with little $15 controller boards and relays, or simply buy a decent controller for wind/hydro that has that function programmable in its interface.

The top-tier SCCs and some better lower priced units can manage full-battery load diversion of solar power to, say, a water heater, a pump, soapstone, or back to the grid- basically something that creates energy storage.
Or buy some controller boards and appropriately rated relays to do the diy trick. But you’ll need to buffer and time delay switchover to avert relay flutters.

Depending on your water turbine size, various retail charge controllers can handle your full-battery diversion to do ‘work.’ Or simply run a charge controller to send excess solar and hydro to whatever place you want.

There’s youtubes of people who are doing now what you’d like to. I’d watch a few and steepen your learning curve and arrive back here with the resulting questions.
 

Wilensky

New Member
Joined
Feb 10, 2022
Messages
4
Location
Kootenays, BC, Canada
@400bird thanks fro the replies. i think i may need clarification on how storage systems work. say my bank is full but my micro hydro is still happily producing its 800 W. if i then turned on a 2.5 kW load would i be able to pull that 800 W directly plus the remaining 1.7 kW from the bank or would I pull 2.5 kW from the bank with the 800 W then going to recharge the freshly available battery capacity at what ever rate teh bank coudl currently absorb (which, I'd image, might not be a ton because the bank woudl be nearly full). if its the former then i i might not have an issue because ill need to heat water anyway so really nothing is lost (assuming a well insulted tank).

@再生可能 エネルギー I have not narrowed down a HP yet but i'm looking at the Sanden CO2 heat pump and the Arctic Heat pump. our site is located in a mountain valley in SE British Columbia Canada. PV generation is limited in the winter:

monthsun risesunsetDaily Ave Genmicro hydrodaily total
1​
14​
15​
2.0​
19.2​
21.2​
2​
13​
16​
6.4​
19.2​
25.6​
3​
12​
17​
13.2​
19.2​
32.4​
4​
11​
18​
23.2​
19.2​
42.4​
5​
10​
19​
29.1​
19.2​
48.3​
6​
9​
20​
32.9​
19.2​
52.1​
7​
10​
19​
32.6​
19.2​
51.8​
8​
11​
18​
26.4​
19.2​
45.6​
9​
12​
17​
15.0​
19.2​
34.2​
10​
13​
16​
6.5​
19.2​
25.7​
11​
14​
15​
1.3​
19.2​
20.5​
12​
14​
15​
1.2​
19.2​
20.4​

those "sunrise" and "sunset" values are estimates of when the sun will clear the mountain ridge in the morning and drop below it in the evening (jsut just downloaded hours production from POV watts and did not count any generation outside those hours.

The plan is to be a year round operation but with a wood fired boiler for heat and hot water (and hot tubs) in the winter. I'm trying to avoid importing any fuel onto the property so I want to avoid propane hot water. There will not be plugs at each campsite, right now the plan is to have 6 x 15 Amp hook up sites for people to stay at over night to charge house batteries (no air con, AC/DC fridges or electric hot water allowed/possible), but mostly i expect people to boondock or tent camp and access any powered services centrally. As to daily loads for hot water and electricity, i have some rough ideas and will be OK with my set up but i will be over generating in the summer and and i don't want to waste anything (hence dump/diversion load question). understanding daily power draws from a heat pump will likely require detailed energy modelling as it will be impacted by a combination of conditions at the condenser and evaporator.

@WYtreasure added my location, I'm in the Kootenays in southeast BC. ive got a pretty good idea of my regional generation, my question basically boils down to how can i use every last drop of power generated and avoid a resistance heat element, and we've got brook trout on the property and a lovely lake a few km down the road, so i guess that's a yes.

@12VoltInstalls when you say "top-tier SCCs and some better lower priced units can manage full-battery load diversion" is this still a DC load? and I'll have a look for any videos, thanks.
 

12VoltInstalls

…myself everything do I…
Joined
Jan 18, 2021
Messages
4,253
Location
Vermont
is this still a DC load?
Other than a resistance load, I don’t think you can do much with “wild AC” so I’m pretty sure that’s all rectified (DC) or both rectified and inverted (120VAC)

Honestly I’m not an expert. I just catalog information in my head - but I can’t remember names lol

I don’t know much on hydro but my observation is you need to get to a-studying and become your own expert or this could become painful LOL. :)
 

Wilensky

New Member
Joined
Feb 10, 2022
Messages
4
Location
Kootenays, BC, Canada
Thanks all.

this looks like what i want to do (except with water heating vs air con), basically just turn on the heat pump when the SOC and production are optimal. I think I'll still need a DC dump load but hopefully it will never be trigger if all my other controls are working correctly. I'll try to update when i get things up and running.
 
Top