Sol-Ark Smart Feature Uses for Overnight Heating Ideas?

[myles]

Hey Guys,

I wanted to create a separate thread to probe around and see how people are using the sol-ark smart feature to store energy overnight that doesn't involve batteries.

What is the smart feature: It is a feature that enables a load output to kick in once the batteries are charged and the load on the unit is less than what is being generated by PV, so you don't waste any generated power.

A bit of background, I am in Canada, in Manitoba, and we have COLD winters, sometimes we see -40F, and sometimes it is prolonged for multiple days or nights, and that of course happens when the sun is not emitting its power as well. My goal behind this is mainly for winter. My build will have propane as main heat source put into hydronic floor heating in a very efficient and air tight build package, and a backup generator in case batteries running low overnight. However, wouldn't it be great to not need to use as much propane and generator power? Obviously YES! So my plan was to slightly oversize my solar system in lieu of the less production in winter, and utilize the smart feature on the solark to "dump" that energy into some sort of heat storage enviroment.

PV System specs so far:
1. 12KW solar panel array
2. 12kw sol ark
3. 16s4P 48v battery setup, each cell 280ah
4. chargery 16 bms 100A each, qty 4 one hooked up to each bank (i think buying these was a mistake but will find out)



I am looking for feedback on the following ideas:

1. Dump excess heat into the garage floor to superheat the garage then use circulation pump to stabilize temps overnight in the house portion instead of using propane boiler to do this.
2. Having a large hotwater tank only for storage of hot glycol that is heated from the excess power, superheating this so that overnight a mixing valve will pull the heat out and put it into the floor of the house portion.


do we have others that have done anything similar with success? I've searched around and can only find the water heater method, which does appear to be the best, but feedback as always is appreciated :D

 

[SolarPrep]

myles:

Some comments:

First, read up on the "Build it Solar" website. Lots of great info there.

Super-heating your garage floor is a bad idea. You will get massive thermal cycling, and that will cause cracking. Slab heat is not intended to be run with high temps. On top of that, you won't store any heat, because a slab is a huge, effective heat sink and emitter.

Typical glycol used in heating systems breaks down faster the higher temperatures go. If you really want to heat to a high temp, you will need a commercial formulation, and it will be very expensive. It is a waste of time and money to attempt this.

A large hot water tank is a great idea. You can build one yourself, and save a lot of money. If you put it in a corner, it can use the support of 2 walls, and be simple to build. Again, look on Build it Solar. If you end up doing a typical large box with an EPDM liner, you will want to keep temps to a prescribed limit. The idea is to go big. Insulate the crap out of the box, and pay extra close attention to the lid, and how you detail the lines in and out. Again, Build it Solar.

Keep your eye out for a large stainless tank. They are more common than you might think. Easy to insulate.

It is way more functional and economical to try to keep the water temp lower, especially if in slabs, or underfloor applications.

Have you considered a simple drain-back system?

The general consensus (I believe) is that it is now cheaper to go with more PV panels, and use electric heat. I happen to be a fan of hot water, because you can pump it anywhere you want to use it. It also makes a great dump load for excess PV. My wife was just commenting last night how cozy our basement is with the heated floors. The temperature stays the same all year around, never more than 1 degree variance. Even when we hit -33F a couple years ago. If you end up doing a hot water based system of any kind, think about using Wirsbo Hepex. It is the best, bar none.

 

[myles]

Thank you so much for your input I will go research!

 

[Ralphloren]

.

 

[mwk1000]

I built this edpm lined tank in 2005 1600 gal and use a boiler custom heat exchanger setup to heat the house. 100->175->100 ( temps heat to 175-180 over night run all day repeat ) thermostats to forced air furnace hijacked blower and added water to air exchangers. It has been heating our home since then VERY well. Soooo Getting old and LOVE the idea of dumping all that extra PV right here ! Save some wood cut/split work at least I would not waste any produced PV power. Just need a reasonable heating element to use if anyone is aware of a fairly large 30+amp with a thermostat control I would be in heaven I saw the Fronius ohmpilot https://www.zerohomebills.com/product/fronius-ohmpilot-9-0-3/ but it seems to be only European grid format compatible ...

Does anyone know of something similar for the US market ?

 

[Wet1]

During the winter months when the heat is needed the most (especially in more extreme northern locations), most will find you'd need a pretty large PV system to have enough surplus power to do any significant home heating. Short days, low angles, snow, etc all work against PV production and makes it a pretty poor choice for heating your home. With a 12k system, I can't imagine you're going to have all that much left over after covering your loads, charging batteries, etc when you only produce around 20kWh (?) per day to begin with in the dead of winter, certain not enough to make a big impact regarding heating your home. Don't get me wrong, if you have extra capacity, by all means put it to work... but I wouldn't plan on it really reducing your heating loads all that much way up north!

BTW, if you do end up doing this, I would look at using a heat pump if at all possible as resistive heating is a lot less efficient. But again, I question if it's worth putting to much money and effort into such a system.

You might find the best way to do this is to just use your house as the storage unit itself, or replace the propane fired heat during the day with a mini-split... Use a MS during solar production hours to produce heat, basically over heating the house by several degrees (or just using it to take the place of some of your propane supplied heating), then kill it once the PV system shuts down. This is possibly going to give you your best bang for your heating buck with PV... plus not having to build or engineer anything. Just a thought.

 

[efficientPV]

These are just general ideas. Resistive heating is best done from the actual PV voltage instead of after the controller with batteries. Low voltage and high current will have higher line losses. Best to leave the battery alone with full charge, lower cycling and give the battery a chance to actually fully go thru charging cycles. A charge controller which doesn't have an additional shunt to determine what is coming out of the battery will never do proper charging.
I heat all my water with PV taking any excess proportionately to maintain PV voltage at near power point to be efficient. Many just throw away power which could heat water. Successful PV systems by their very nature have to be oversized in order to recover from bad days. Why not heat water. Winter is a difficult time with shorter days and often more clouds. Hard to imagine a lot of excess. I have people that heat camps with PV when they aren't there preventing dampness and freezing. Hydronic systems can be quite expensive. Here is an oil filled I modified to provide some heating right off a 60V array. While rated at 1500W, just 400W makes this not touch safe unless the room is really cold.

 

[mvonw]

I'm in a cold climate place too and was planning on connecting the dump load to a small (200watt) thermostatically controlled DC heater to heat my insulated battery cabinet with 6 Trophy batteries (with heaters) , My thought is this will reduce the amount of heating the batteries will need to do and get me a few more watts into the batteries on sunny winter days. In summer, the thermostat will control a fan that ventilates the battery cabinet. When the temperature in the battery cabinet gets above 25C, the system will automatically turn on heater to heat the insulated shed my batteries/inverter are in (where the battery cabinet is). None of this is really probably necessary, it's just fun to see how much I can optimize things. I already have too many solar panels for my Sol Ark 12K to handle., Maybe eventually another Sol Ark.

 

[mwk1000]

[During the winter months when the heat is needed the most (especially in more extreme northern locations), most will find you'd need a pretty large PV system to have enough surplus power to do any significant home heating. Short days, low angles, snow, etc all work against PV production and makes it a pretty poor choice for heating your home. With a 12k system, I can't imagine you're going to have all that much left over after covering your loads, charging batteries, etc when you only produce around 20kWh (?) per day to begin with in the dead of winter, certain not enough to make a big impact regarding heating your home. Don't get me wrong, if you have extra capacity, by all means put it to work... but I wouldn't plan on it really reducing your heating loads all that much way up north!]

I agree , I did the math a while back and even with my 18K system it makes a small contribution. But hey it's a few less logs to split And a pretty good "dump" for zero export in the winter at least. Summer time it might be problematic though I am just trying to understand my options without dumping huge $$ into batteries.

 

[Hedges]

Summer, it is probably cheapest to discard surplus available PV power and then purchase from grid when you need more power than you produce.

i.e. if you don't have net metering, just do zero export. Do laundry when the sun shines, but don't store power in batteries. Whether huge $$ into batteries or small $$, they cost more than grid (except for some cheap e.g. DIY)
Batteries are suitable for critical loads, internet if grid is down etc. where cost per kWh doesn't matter.

If you do need heat every night and have surplus every day, then thermal storage probably makes sense.