Offset Electric Boiler energy usage with batteries and solar?

[Hedges]

True, but my 6kW 95% efficient inverter is only a 300W heater. It could deliver 6000W to resistance or heat-pump.

DC direct and solar thermal will have their applications, but water heating is an afterthought for most home users. So electric, even resistance, makes sense. Space heating could be a major application, too bad so little sun in the winter.

An off-grid system would ideally have surplus PV at least in summer, so water heater as dump load (AC or DC) is a no-brainer. I would prefer variable load rather than cycling batteries.
There are some DC water heater controllers that drive PWM (accomplishing PV MPPT into a resistive load), with pulsed DC so thermostats should work fine.

 

[32 volt boater]

649 Euro for 250W

Better to pay $50 for 250W (used), and just do electric heat.

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Many is the good idea that died due to economics.

How about DIY water cooled solar?

I don't know. I think photosynthesis is the absolutely best way to do solar heating.

Instead of Irrigating and fertilizing the stupid lawns, then paying someone to cut it and throw it away grow firewood.

Lawns are the No. 1 irrigated 'crop' in America. They need to die.​

https://grist.org › article › lawns-are-the-no-1-agricultur...

May 2, 2019 — A NASA-led study in 2005 found that there were 63,000 square miles of turf grass in the United States, covering an area larger than Georgia.

Homes, golf courses grow more acres of turf grass than U.S. farmers devote to corn, wheat and fruit trees — combined.

---------________

 

[Hedges]

Keep part of the yard for lawn. Enjoy milk and goat meat. And free fertilizer.

 

[32 volt boater]

Wile most suburbanite dummies put there fall leaves and grass clippings out for the trash (then drive to homedepo and pay for a bag of compost potting soil) its a free source of energy.

By running water through a compost pile, it was brought from 7 °C to a blistering 62 °C. Not much more needs to be said that the video doesn't say.

Using a compost pile to heat domestic water

This is a great little video that illustrates how we are surrounded by potential energy, we just have to put a little thought into how to harness it. We found this video at Whole Systems Design, a New England based company who identify, design, and develop human habitats. In their own words from...

www.ecohome.net

 

[Ampster]

I am self sufficient for most of my energy needs, drive two EVs, have installed grey water and rain catchment sustems and recycle almost everything I can including making my own compost. We stopped watering the rear lawn but my wife has an attachment to the front lawn despite how bad it looks in this summers heat. I did change out the sprinklers to save some water and that may be why it looks so bad.

 

[Ampster]

By running water through a compost pile, it was brought from 7 °C to a blistering 62 °C. Not much more needs to be said that the video doesn't say.

Not to mention you know what is in it when you make it yourself. I can get mine that hot and it will even kill the seedss from the weeds. I do not think that can be said of the store bought version.

 

[efficientPV]

It is a regular comedy show here on Buy It Now Solar watching people fall all over themselves trying to heat water with PV. It is proven technology that has ....
run for years,
it is cheap,
uses existing WH hardware,
uses excess PV energy that everyone just wastes,
doesn't wear down your battery,
always leaves battery with highest charge,
doesn't interfere with battery charge cycles,
doesn't use charge controller capacity,
doesn't use inverter capacity,
operates off existing panel array the charge controller uses,
uses existing thermostats,
multiple HW controllers can be operated in parallel with set priority,
totally automatic.

 

[Ampster]

It is a regular comedy show here on Buy It Now Solar watching people fall all over themselves trying to heat water with PV. It is proven technology that has ....run for years,

I enjoy the humor also but from a different perspective. I have installed two thermal solar hot water systems in the past forty years. I sold both homes before there was any need for replacement so I do not have good numbers for expected life. I do not go on roofs anymore at my age and for me the the most efficient system is a grid tied solar and HPWH. Once the water is heated the excess energy can earn some credit for use later in the season. The economics might be different for off grid.

If I was heating a swimming pool I still might consider thermal solar. It all depends on where you are standing.

 

[12VoltInstalls]

operates off existing panel array the charge controller uses,

I’m busy and not actually lazy. So I’m not dissing nor trying to get someone else to go looking for me. This is a, “do you know…?” question.

While I can think of multiple ways one might send excess PV (or actually SCC output) to a (in my case) 12V water heater element, I have looked for an integrated device that could facilitate not running the element if voltage isn’t over, say, 13.2 or whatever, and kill water heater feed over 160- or 170*F or whatever you want.

Is there such an animal?
I haven’t found one. But I do find charge controller boards and some DC temperature control relays you could hack together easy enough. But I don’t want to.

 

[12VoltInstalls]

was heating a swimming pool I still might consider thermal solar. It all depends on where you are standing.

in the pool of course​

 

[Ampster]

in the pool of course

I am 6'7" so I often find myself standing in pools where others are not standing.

 

[mechdriver]

Did you install the electric boiler? If yes, would you mind sharing the model and consumption data. I am trying to do something similar since I already have PV system installed e.g. 1000kwh per month in winters generation.

It is installed and operational. Just started to get colder here so it will be a little while before I understand my usage. It’s an Argo 16kw electric boiler AT164410C.

 

[mechdriver]

Move off LongIsland. Long time girlfriend was from that place nothing but taxes, state - county - town - village hassles and massive corruption from the parasite class on every level.

A dump load controller, also known as a diversion load controller, diverts electricity from a battery bank once the charging source (wind turbine, PV, hydro turbine, etc.) has fully charged the battery bank. www.google.com/search?q=dump+load+controller

Choose from a wide variety of submersible DC water heating elements for direct connection to your batteries or solar panels.

dc hot water heater elements - Google Shopping

www.google.com

You can covert any hot water heater to lower voltage DC.

Put the hot water heater in the attic for the summer where its already hot for obvious reasons.

View attachment 110930


I am thinking maybe an AC/DC hot water heater. Probably putting the solar DC into the bottom element would be best.

But anyway its insane inverting solar produced DC to AC, alternating current to make heat.

Tesla was cool but in the solar off grid world alternating current is just a major hassle.

Long Island is expensive. If I could, I’d live where I could not see my neighbors and had plenty of space for projects, garages, and hangars.
I think that a dump load controller is a great idea. I spent a lot of time looking into DC heating elements and rolling my own. But I work a lot so my projects usually need to be less theoretical and operate at wife levels of reliability. I look forward to more options as people and companies facilitate more electric solutions.

 

[mechdriver]

Great dialogue here everyone.
As I mentioned the electric boiler is installed and operational. I have it linked to the Taco outdoor reset control which I can set for an electric boiler’s usage parameters (such as no minimum supply temp) and crucially I set the Warm Weather Shut Down to the mid 40s F so the electric boiler can automatically takeover for the mini splits as they fall off in efficiency in intermittent cold weather and should allow them to alternate between a day/night cycle of mild/cold temps. I’m using delta T circulators for even further electrical and thermal efficiency. I did have to do a lot of work to install the electric boiler into a proper primary/secondary loop that my oil burner did not have. Also, adding a flow switch, low water cut off and various valves added to expense and effort of the install.
Unfortunately one of my two mini splits had a leak over the summer and I determined I fell victim to an apparently common problem of bad lineset insulation causing pinhole corrosion from condensation. It was really bad when google auto filled that search result. Very frustrating and little recourse other than just dealing with it. I figured line sets were good for the life of the system! I review installation instructions carefully and they never advised to seal the foam ends to prevent condensation from entering the insulation. Turns out that’s their fix for poorly chosen insulation material that creates acidic water that eats copper over time!
I caught it earlier enough I only had to replace one line set… that ran through my garage down into my basement ceiling. I replaced the line and pressure tested it for 72 hours and drew a 50 micron vacuum to ensure I had no more leaks. For better or worse, I’m finishing the basement currently and just had to unscrew the Sheetrock ceiling as opposed to busting it open.
Speaking of the basement, most of my spare time has been spending tiling the floor so supporting the electric boiler with solar, etc has not been a priority. Excited about the EG4 LL V2 and their work on getting UL certs and I feel a whole house plan is better than my initial small setup to offset the electric boiler.
Speaking of certs, I’m also taking a EPA 608 universal course so I can buy the replacement refrigerant I need.. The $175 25lb container I bought 5 years ago is empty after initially adjusting for line set length, 2 previous leaks and a reconfiguration where I moved an indoor unit (yes I recovered existing refrigerant), and it presently costs $500 and proof of EPA certification to buy a 25lb jug of 410a, which is also being phased out and I may not have a drop in replacement for my mini splits. Oh the joys of “progress” and innovation!

 

[Azeem]

It is installed and operational. Just started to get colder here so it will be a little while before I understand my usage. It’s an Argo 16kw electric boiler AT164410C.

congrats and thanks for letting me know about it.

 

[mechdriver]

I’m back to report everything has been working as intended and I actually reduced my year over year electric bill for February! Last year I ran exclusively on the mini splits as my oil burner was broken. It has been warmer this year but the combination of the electric boiler for the hydronic heat below an outside temp of 40 and the mini split otherwise running has worked really well.
I leave the mini splits which are rated down to 0 degrees F on 24/7 but as they slow down making heat the wall thermostat for the electric boiler kicks on. It usually just runs in the morning which tracks with the coldest time of the day.
I did try on the coldest overall day of the year exclusively using the electric boiler to ensure it can act as a standby unit by itself. It did the job but at 3X my daily energy usage! So the tag team of heat pump and electric resistance elements for hydronic baseboards work well together.
What does this have to do with solar? Well now I can start planning a setup knowing my utility overhead.
So at some point I’ll start a new thread on my whole home or utilities load only orientated solar setup.

 

[Shimmy]

I leave the mini splits which are rated down to 0 degrees F on 24/7 but as they slow down making heat the wall thermostat for the electric boiler kicks on. It usually just runs in the morning which tracks with the coldest time of the day.

Have you considered locking out the boiler in the morning to see how much your space temperature drops? Might give you insight into just how much you need the boiler to bridge that time.

 

[mechdriver]

Have you considered locking out the boiler in the morning to see how much your space temperature drops? Might give you insight into just how much you need the boiler to bridge that time.

I definitely can find more efficiency by adjusting the warm weather shut off that dictates when the electric boiler can turn on. I can also get thermostats that would interact with the mini splits instead of using the remotes. I have 2 multi-zone units so that’s 8 heads so a lot of thermostats. I’ve been dissatisfied with most of the thermostats for mini splits. I only change their temps in small amounts so I’m missing out on setting them further back when the house is unoccupied. But If i did I would want automation to turn them on before I get back to house as they can take time to spool up. I don’t work a regular schedule and my family also is in and out of the house all day so it’s been okay to leave them at basically 2 sets of temperatures: 64-70. 3-4 of the zones are in spaces that can stay at the lower temperatures of 62. Sometimes we forget to setback when leaving for the day.
It’s been pretty cool to watch the layers of efficiency at work in the electric boiler. The thermostat calls, the outdoor reset dictates the electric boilers target temp, the boiler decides how many elements (4 x 4Kw) to energize, the delta T circulators spin at the speed necessary to maintain 20 degree delta T for the zone. Because it’s electric it also has no problem turning on at random intervals, something a high efficiency oil or gas burner would not like to do.
My house is well insulated- all low-e windows, new doors, R-15 in the walls with 5/8” sheetrock on the interior and full brick veneer or foam backed vinyl siding on the exterior. Attic has R-30 plus a foot or two of blown in insulation with vents and 2” foam board on any interior wall in the split level attic. Tight air sealing throughout down to outlets and switch boxes. Basement has 2 inch foam board on the walls and the rim joists followed by a R-15 studded wall, then R-30 in the ceiling with Sheetrock too. Few minor areas to correct, I have soffits for the perimeter of my roof I need to drop and insulate where the attic vents meet the top plate as the original design leaves no room for insulation there. Building Science has come a long way.

 

[Shimmy]

I can also get thermostats that would interact with the mini splits instead of using the remotes. I have 2 multi-zone units so that’s 8 heads so a lot of thermostats. I’ve been dissatisfied with most of the thermostats for mini splits. I only change their temps in small amounts so I’m missing out on setting them further back when the house is unoccupied.

For my Mitsubishi units you can do an ESP8266-based control hack to simulate the remote... but I agree the logic of mini-splits leaves a lot to be desired. Mine end up trying to dehumify when they don't need to, cannot limit compressor energy, and really focus the design on continuous operation which is often not necessary.