Direct to water heating.

[TRW]

Lots of interesting stuff! The reason I like this thread, is because I think the day is coming when there will be more incentive to stay off the grid. At that time if we have sufficient panels, we will have times when we have excess power. There are electric boilers that were made by a company in North Dakota, and still are. They were marketed for off peak heating, that has somewhat been diminished now, but I think they might have a place for excess power.

 

[GLC]

Lots of interesting stuff! The reason I like this thread, is because I think the day is coming when there will be more incentive to stay off the grid. At that time if we have sufficient panels, we will have times when we have excess power. There are electric boilers that were made by a company in North Dakota, and still are. They were marketed for off peak heating, that has somewhat been diminished now, but I think they might have a place for excess power.

Totally agree, even though I am connected to the grid, solar power is supplying 80 percent of my 110 needs through panels, controllers, batteries, inverters with manual switching box. And of course a very large portion of my hot water heating needs. One more thing, I just installed a split ductless air conditioner in my master bedroom that is being fed from my solar setup. Free power for air conditioning is pretty "cool". And if some reason grid goes down in the summer months, we can escape to the bedroom and remain cool.

 

[TRW]

Very interesting story, You have a system that is tied to the grid, but also have some independent solar?

 

[GLC]

My solar setup is not tied to the grid but my house is tied to the grid. I nave a manual transfer switch where I can run solar to power certain circuits or grid power as needed.

 

[efficientPV]

We ought to have better water tanks that last like the Marathon except with some extra ports for heating elements. Every household replaces about five tanks in a lifetime. Anode bars are eaten away in as little as three years.

 

[GLC]

We ought to have better water tanks that last like the Marathon except with some extra ports for heating elements. Every household replaces about five tanks in a lifetime. Anode bars are eaten away in as little as three years.

I love the idea of tanks with extra ports!!!!

 

[efficientPV]

A lot of people think the electrodacus system will save them. It just doesn't work till you have about five elments to switch in and out. Nice idea but pretty impractical given the hardware available.

 

[GLC]

Actually I have one element in the bottom of one tank and it works very well 90 percent of the time for all of our daily hot water needs. If I had a extra 40 gallon tank to store hot water in I think I would be good for 2 or 3 days without sun.

 

[Daddy Tanuki]

i totally did not mean to derail anything by bringing up heat pumps. absolutely do not think they are perfect for all situations and all people! those technology connections videos are real great educational material for less experienced visitors (that was my thought in sharing them). probably just goes over a lot of stuff the people in this thread already know

despite a thermoelectric peltier element being less efficient than a compressor based heat pump, the peltier can very easily switch on and off to transiently shed extra power. the TEC is a resistor after all, so being cycled does not harm it*, whereas a compressor has minimum on times and fairly high current requirement to operate usefully. TEC can efficiently operate at <100W easy and for microseconds at a time safely.

i'm trying to design various thermal management systems, and a more integrated approach can have some upsides for my use cases.

just thinking out loud, if i do build a DIY water heater, probably would test/evaluate peltier element to get the water up to a moderate temp and get free cooling, then use resistive heating to get it to the peak temp.

also add like 4-6" of polyisocyanurate on all sides of the thing

hope this is not too OT, cheers


*peltier elements can degrade from certain frequencies of heat cycling over longer times, so keeping it coupled to the water would help ameliorate that design risk factor.

l like you thoughts about the cycle usage. I work ON ac/r on a regular basis and the biggest failure of the compressor is a short cycle.

 

[Paul Green]

This is what I do to heat my 50 ltr hot water tank

I have 2500 watts of panels. I have a 1500/3000 watt 12 volt to 220 volt Indian made inverter

My 240 volt immersion heater is 1800 watts and has 3 settings low. Medium. High. (An inbuilt voltage regulator) on the low setting. The heater takes 390 watts.

Hey presto.

Problem solved

Therefore.

If a manually adjustable voltage regulator (Dimmer Switch) is installed on the supply to the heating element . You can set how many watts the element gets.

Hope this helps

 

[Frick]

An interesting discussion, I’m enjoying this.

I ran a test the other day, Used Santan 250 watt panels laying in the grass on a hot summer day.
Denord 36v water heater element, dual loop @2.2 ohms each.
I only used one of the two loops for this test.
with two panels in parallel produced 29.33v @14.6a or 428 watts in full hot sun. not bad.
using one panel saw a voltage drop to 19.4v @ 10amos or 194watts. Also not bad.
two panels with solid solid full clouds still saw 4amps .
these were all stright solid connections with only a shunt inline. It says that using the Electrodacus system with diversion and likely 70% of my panels diverting all day will heat the water I want while being dead simple and reliable. I built a basic temp controller from a Inkbird controller through dc Ssr’s.

 

[Frick]

Also, I left three dead grass rectangles in the grass in the hour they sat there that got worse over a few days. (One santan panel was bad and I set it aside) which was a poor idea since we are in process of selling the house.

 

[efficientPV]

Sunny day thinking. My wife doesn't want to hear a story about the clouds. She wants hot water to do the dishes. Off axis, tiny clouds eat away at power. Even a little power all day makes a big difference. If you have the space and access to cheap used panels direct connect is fine. It is raining and I'm still making some hot water. For the chart below, just think of 10A as 100% of what an array can produce.

Panels at 60V Direct connect Increase in power with power point

10A X 60V = 600W 10A X 60V = 600W

9A X 60V = 540W 9A X 54V = 486W 11%

8A X 60V = 480W 8A X 48V = 384W 25%

7A X 60V = 420W 7A X 42V = 294W 50%

6A X 60V = 360W 6A X 36V = 216W 67%

5A X 60V = 300W 5A X 30V = 150W 100%

4A X 60V = 240W 4A X 24V = 96W 250%

3A X 60V = 180W 3A X 18V = 54W 333%

2A X 60V = 120W 2A X 12V = 24W 500%

1A X 60V = 60W 1A X 6V = 6W 1100%

If you have unlimited funds, no clouds, and space for an array this isn't a problem.

 

[TRW]

An interesting discussion, I’m enjoying this.

I ran a test the other day, Used Santan 250 watt panels laying in the grass on a hot summer day.
Denord 36v water heater element, dual loop @2.2 ohms each.
I only used one of the two loops for this test.
with two panels in parallel produced 29.33v @14.6a or 428 watts in full hot sun. not bad.
using one panel saw a voltage drop to 19.4v @ 10amos or 194watts. Also not bad.
two panels with solid solid full clouds still saw 4amps .
these were all stright solid connections with only a shunt inline. It says that using the Electrodacus system with diversion and likely 70% of my panels diverting all day will heat the water I want while being dead simple and reliable. I built a basic temp controller from a Inkbird controller through dc Ssr’s.

Thanks for the input. You said " these were all straight solid connections with only a shunt inline. Can you explain that to a novice like me?

 

[Frick]

Thanks for the input. You said " these were all straight solid connections with only a shunt inline. Can you explain that to a novice like me?

Sure. It means I cut the wires and crimped on ring terminals to the solar wires to attach to the shunt and the water heater terminals. It’s the simplest method of connecting panels to shunt (to measure current) and directly to water heater element. In the future version there will also be a DcSSR to interrupt the circuit when the water tank reaches set max temp.

@efficientPV I guess my point in all this is every different application with its criteria and trade offs have its ideal set up. after many years in high end industrial automation and computer control, I enjoy dead simple reliable set ups with minimal fancy expensive parts that could fail and that I would have to maintain. engineer and match compononts to natively work in their ideal way. A trick I learned as a Porsche mechanic at a young age. They were often far simpler than competitors cars yet worked better by careful design. my application doesn’t have space or shade issue beyond clouds, it does have an issue of fixing and replacing components in a far away land on a mountain without an address where such parts don’t exist. My overpaneling is cheaper than the mppt controllers I would need if I look at it that way, also less to break or replace potentially 1-3 times over the life of the panels, a cost I consider to be important. I may one day get another mppt controller and side by side it in the same water tank with data loggers just for giggles, others have done it and I’ve seen much variance in results.
the next setup I’m building does away with most of the panels and uses a new hydro system I’m developing that is easy to deploy in shallow stream applications and fully fault tolerant of all the normal pitfalls and maintenance.

half my distribution set up is 24vdc so the nice inverter I have can be turned off much of the time. Yes I have line losses and less available power, but for lights and fans and our cold room it all runs without an inverter, and the cheap surplus panels cover that loss with minimal one time expenditure. I expect I can reduce inverter time by 75%, potentially extending its life somewhat before the capacitors degrade over time And render it useless.

thanks for the data, I don’t fully follow if that is theoretical or your own test results, but my tests showed 85% of rated output in hot 10+ years old panels in good sun, to 12% of rated output in full thick cloud cover. Without the side by side to equalize all variables, it’s hard to quantify The mppt difference. I didn’t get out the light meter and record irradience, though I likely should have, this was more a quick test of heater elements and panels as a set.

 

[TRW]

Sure. It means I cut the wires and crimped on ring terminals to the solar wires to attach to the shunt and the water heater terminals. It’s the simplest method of connecting panels to shunt (to measure current) and directly to water heater element. In the future version there will also be a DcSSR to interrupt the circuit when the water tank reaches set max temp.

@efficientPV I guess my point in all this is every different application with its criteria and trade offs have its ideal set up. after many years in high end industrial automation and computer control, I enjoy dead simple reliable set ups with minimal fancy expensive parts that could fail and that I would have to maintain. engineer and match compononts to natively work in their ideal way. A trick I learned as a Porsche mechanic at a young age. They were often far simpler than competitors cars yet worked better by careful design. my application doesn’t have space or shade issue beyond clouds, it does have an issue of fixing and replacing components in a far away land on a mountain without an address where such parts don’t exist. My overpaneling is cheaper than the mppt controllers I would need if I look at it that way, also less to break or replace potentially 1-3 times over the life of the panels, a cost I consider to be important. I may one day get another mppt controller and side by side it in the same water tank with data loggers just for giggles, others have done it and I’ve seen much variance in results.
the next setup I’m building does away with most of the panels and uses a new hydro system I’m developing that is easy to deploy in shallow stream applications and fully fault tolerant of all the normal pitfalls and maintenance.

half my distribution set up is 24vdc so the nice inverter I have can be turned off much of the time. Yes I have line losses and less available power, but for lights and fans and our cold room it all runs without an inverter, and the cheap surplus panels cover that loss with minimal one time expenditure. I expect I can reduce inverter time by 75%, potentially extending its life somewhat before the capacitors degrade over time And render it useless.

thanks for the data, I don’t fully follow if that is theoretical or your own test results, but my tests showed 85% of rated output in hot 10+ years old panels in good sun, to 12% of rated output in full thick cloud cover. Without the side by side to equalize all variables, it’s hard to quantify The mppt difference. I didn’t get out the light meter and record irradience, though I likely should have, this was more a quick test of heater elements and panels as a set.

OK, thanks for the info, I like the direction you are going, I like the idea of using excess power when available, and without the loss of the invertor when it can be done safely.

 

[Frick]

OK, thanks for the info, I like the direction you are going, I like the idea of using excess power when available, and without the loss of the inverter when it can be done safely.

it is advantageous to me in two ways, one it leaves the inverter not under constant full load every day, 2 even with an inverter failure i still have pressurized hot water and lights and such (24vdc pumps)

 

[Tecnodave]

There are many voltages of water heater elements available, 12 volt heaters have long been used by farmers to keep cattle water troughs from freezing. these are commonly available and there are solar specific heaters that are dual elements that can be wired for 12 volt, at reduced power , 24 and 48 volts by parallel or series connection. I use several Trace C-40 PWM controllers in diversion mode to use excess battery charging power to multiple low voltage heater elements, i have more than enough hot water except when the Pacific Ocean wants to share its fog, etc. Diversion will not happen until batteries are at 80% or so and out of bulk charge, the hot water is a side benefit of the p.v. panels and far cheaper that a solar hot water system.

 

[Pierre]

150L PV Water Heating System – Geyserwise

Here is a product that I am going to experiment with. Firstly I just want to buy the AC / DC element and feed the DC side directly from the PV panels. Also note that the element is not a standard resistance type but uses ceramic chips. Full details on the website.

 

[curiouscarbon]

l like you thoughts about the cycle usage. I work ON ac/r on a regular basis and the biggest failure of the compressor is a short cycle.

Thank you for your feedback. I am grateful to have your perspective.

I wonder if short cycling is less of an issue with newer inverter based AC units.. Due to gradually ramping up and down? Anyways, cheers!

Wanted to make DIY thermostat after a “smart” thermostat forgot how to use wifi.. then remembered that it’s necessary to have hard delays for the machine to settle and whatnot… moved onto a safer project ?