Decided to go solar (just a little)

RimaNTSS · Jun 6, 2022

My old shed had to be destroyed and replaced by new (not really new) container type 6,6x3m box. It had leaking roof, rotten window and door. Walls are also not in good condition. So, I decided to renovate the container and install solar panels on it's roof. It will take some time, of course. Solar panels will be connected directly to heating elements, to heat the water for household needs. I think that ~4,5kWt total power will be adequate. And that is without inverters, just for water heating.

Terryl · Jun 6, 2022

Why use electrical solar panels to heat water, get some solar water heating panels, I use some to heat the shop during the winter.

The water come in at 56 degrees F, and sometimes comes out at 180 degrees F, I know this as the relief valve on the system is rated to 180 degrees F, used an old water heater as storage, you could use a standard electrical solar panel to run a pump.

I have both an in-floor system and fan driven radiators.

RimaNTSS · Jun 7, 2022

Terryl said:
get some solar water heating panels

It is far away from the home and I do not want pipes with liquid going so far. Will think about solar heater in the future. But today, only electrical panels.

RimaNTSS · Jun 16, 2022

Have some progress with frame building. The leaning will be 30* ish. I am not sure yet do I need to add additional strength pieces (painted them yellow). In addition, there will be 4 tubes all along the frame for fixing the solar panels.

Terryl · Jun 16, 2022

RimaNTSS said:
It is far away from the home and I do not want pipes with liquid going so far. Will think about solar heater in the future. But today, only electrical panels.

If it's too far from the house to run water, and your not going to use an inverter to convert the DC from the panels to AC,(as stated in your first post) then it's too far to run the DC voltage to the house to heat it directly, (unless you use some very large guage wire) you will loose quite a bit of voltage on the DC side, also do they make a DC powered water heater???

RimaNTSS · Jun 16, 2022

I do not see a big difference (if any) between AC and DC heating elements. Secondly, no need for large gauge wire if there will be 200V DC running at max 25A. I will need 2,5mm2 wires. Of course, the sun is not always at it's maximum, therefore I will need to use more than one heating elements to use generated power more optimally.

Terryl · Jun 16, 2022

It's not the heating elements that would be the problem, it's the thermostat that controls the elements, on a AC powered water heater the thermostat's contacts are rated for 220 volts AC, I don't see anything for a DC rating on most electric water heaters, using DC would melt the contacts eventually if used for switching 25 amps at 200 volts DC.

The contacts would be switching at a full load on the DC circuit, were as the contacts on a AC powered one would switch at a zero crossing. (AC in you part of the world switches back and forth at 50 times a second)

I did some looking around and found DC powered water heaters.

How far is it from the panels to the heater location?

Terryl · Jun 16, 2022

I found this about using DC to power a AC water heater.

Code:

https://www.quora.com/Can-we-use-AC-water-heater-direct-with-DC

I've done quite a few solar installs in my time, if you need info I'm here to help.

RimaNTSS · Jun 16, 2022

I do not think I will be using a thermostat at all. Why should I? I have ~2 tons of water in the hot tub in the garden. And additional 1,5t in the house in the heating system. So, I doubt that it will be possible to boil such amount of water with the amount of solar panels I plan to install. I will be using DC Solid State Relays (SSRs) for connecting/disconnecting heating elements.

RimaNTSS · Jun 16, 2022

That is schematics for my installation. 12 solar panels, 6 in series and another 6 in parallel connection. 6 voltage relays will monitor voltage on one of the solar panels. Depending on voltage, the relays will be switching on/off heating elements to keep panels working near their maximum power point.

Terryl · Jun 16, 2022

If this is not going into a hot water storage tank, (like in a house) then I should work OK, if you are going into a tank then a pressure/temperature relief valve should be installed on the tank.

If no tank is going to be used then a small expansion tank should be used, it will keep you from bursting water lines.

And don't forget a in-line circuit breaker or fuse on the DC lines, if for some reason one the heating element shorts out you don't want to be replacing the wiring.(it does happen)

And a thermostat keeps the water temp at a desired level, you don't want to scald any one.

My solar floor heating system was heating about 1000 cubic feet of concrete, it got to about 180 degrees F coming out of the panels, it kept popping the thermal relief valve on the storage tank, I had to add a thermal mixing valve (acts like a thermostat) at the panels to keep this from happening.

It's best to be over cautious then have an unexpected problem.

RimaNTSS · Jun 17, 2022

Of course, I will install circuit-breaker and also thunder protection.
Heating system in the house consists of 1,5t water tank which gets heated by palette stove. The tank has 70L expansion tank and it is open air system (you can boil the water and no additional pressure will be created in the system. There is another 150L indirect heating water tank (for shower), it is heated from the main tank. The system is working and it will continue to work after I add a couple of heating elements to it.
Unfortunately, there are no heated floors, just water radiators.

RimaNTSS · Jun 21, 2022

More or less have finished with the frame building. Solar panels should arrive soon (maybe even this week). Heating elements and some switches came today.

RimaNTSS · Jul 4, 2022

Finally, brought home solar panels. Those are a little different than I planned in the beginning, but should be OK anyway.

RimaNTSS · Jul 6, 2022

Modified the stove of the hot-tub by installing 2 heating elements at it's bottom. Now the stove can be heated by electricity or wood, or both at the same time.

RimaNTSS · Jul 8, 2022

Just finished the installation.

RimaNTSS · Jul 10, 2022

I do not know what looks better right now, my antenna or new solar panel array. They both look perfect.... I think.

RimaNTSS · Jul 15, 2022

Still waiting for Solid State Relays to arrive from Ali. There is the box where all the control element will be located. Discovered that voltage relays have some deviations in parameters. And there is no way to calibrate them. So, precision of work of my solar system will be about 0,5V.

RimaNTSS · Jul 20, 2022

Connected all solar panels directly to heating elements with total power ~ 3,2kW, and during the day got more than 25kWt/h of free energy. With that energy heated the hot-tub to 33*C temperature. Of course, the hot-tub is not insulated and lots of energy goes directly to global warming, but anyway. I think that after I replace the heating elements to proper value ones and install the simple automatics, the performance of the system will be dramatically increased.

Terryl · Jul 20, 2022

Great job....I'd like to know what type/brand of soild state relays and voltage relays you used, I have a project in mind.

But it's not totally free until you exceed your total costs to build the system.
System kilowatt hour times the cost of one kilowatt hour charged by your electric company... Mine is 11 cents US per KWh
My in floor heating system paid for it's self in 8 1/2 years.

Decided to go solar (just a little)

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