I live in South East GA. Converting an electric water heater to solar?

[testdepth]

I have an existing standard 40 gallon electric water heater and I want to convert it to solar if its possible?

 

[Stephen InGeorgia]

No reply huh. I'm looking into this as well as to add a 40gal before my 50gal and pre-condition the incoming well water. Backup is to have some hot water with the power out. This is the best site I've found so far. reach out to me if you want to collaborate.

How to convert AC water heater to DC

How to convert AC water heater to DC

waterheatertimer.org

 

[DThames]

Here is a product that you should look at. It is an off grid micro-inverter type unit that makes AC.

From the linked page.....
The CyboInverter offers battery-less off-grid solar systems that can take major loads off the grid. It’s easy to install and maintain, no batteries, and can still run when the grid is down. The CyboInverter H Model can connect to 4 solar panels and generate up to 1250W AC power. Each CyboInverter’s input channel has its own control and maximum power point tracking (MPPT) mechanism so that power production is maximized and the partial shading problem is eliminated.

The off-grid CyboInverter H model has the following unique features and benefits:

• Specially designed for powering dual or double element electric water heaters,
• Reduces electricity bills, avoids high tier rates, and provides quick ROI,
• Has no high-voltage or high-current DC so that it is intrinsically safe,
• Ideal for battery-less off-grid solar systems,
• Easy installation and great price,
• High efficiency and long life, and
• Offers a much simpler solution than solar thermal water heaters.

 

[Nobodybusiness]

I have an existing standard 40 gallon electric water heater and I want to convert it to solar if its possible?

Never tried it.
Seems to me DC elements would work.
Have to find a way to make break control for temperatures.

Whatever DC elements wattage is match panels in series and parallel to match..

 

[pollenface]

What voltages are you working with?

 

[Vigo]

Lots has already been said, but you have to dig through at least SOME of the prior threads in this section..

Heating elements are just resistive elements and don't actually care if you give them AC or DC. However, if you try to run them at a much lower voltage you'll have disappointing heat output. Halving the voltage gives you 1/4 the heat, so if you have a 240v water heater and hook up something like a large ~50v solar array you'll still have fairly low output with the existing heating elements even if your panels are capable of thousands of watts. Wiring in series to get at least over 100v will get you a possibly sufficient amount of heat. Since an electric heating element inside a tank of water is basically a 'perfect conversion device' nearly 100% efficient, if you stay close to the original voltage (like 240) your panels' watts rating is a good rough equivalency to how much heat you'll get, but if you pick a different voltage you have to do some math with watt's law.

You do need to use a DC-rated switching device rather than the existing thermostat, BUT you can use the existing thermostat to control that external switching device. The link shown in the 2nd post covers this.

In my recent thread on this topic someone posted a helpful link to a 'water heating calculator' https://bloglocation.com/art/water-heating-calculator-for-time-energy-power

There are technically many ways to do it. You have to narrow down to what approach you are trying to take. Just panels, no inverter, feeding DC to existing heating element? Would this be the first solar at the location or is there already another system that you are just deciding not to tie into? The more info the better.

 

[houseofancients]

if you're a tinkerer , here's a diy/opensource solution

LoadMaster XP - A Smart PV MPPT Solar Hot Water Controller

A solid-state, low-cost, reliable solution for solar hot water from PV. Zero maintenance & CO2, connected, smart combi pre-heat control.

create.arduino.cc

 

[efficientPV]

Only in recent years has PV become a viable economic source for heating water. You don't even need to buy used panels for it to be cost effective. Heat pumps are great. But if you don't already have a large inverter and battery along with tax incentives, resistive heating is more than competitive on a cost basis. I have a small PV system with only a car battery for storage. A heat pump would cost me more than $2,500 to implement. But I heat water with my existing PV and even have enough for the clothes washer to have its own 40 gallon water tank with all cycles using hot water. Direct connect is cheap and easy. Unfortunately, it is inefficient and works poorly in lower light levels. I use a power point diverter which keeps the panels at peak voltage efficiency and is absolutely the best way. The solar world has been slow to adopt new technology and these controllers are few and expensive. PV water heating is still only for the advanced experimenter. I will be posting an even easier version to build soon.

 

[Larry Oswald]

I am wondering if connecting a 240VAC standard water heater straight from the 230VAC output of a off grid solar panel fed chinese inverter/charger (battery off) and let it heat away while the sun shines would not be an easy solution. Seems like the thermal lag in the water tank would make this tolerable so long as you are not part of a large and fussy family.

Parallel question. Can my grid tie roof top system be made to heat the water tank but never have the tank use power from the grid? How could the water tank know where the 240VAC was coming from?

 

[efficientPV]

The heating elements must be electrically isolated from the grid. Often just the lower element in a tank is connected to PV. There are three phase elements which can replace factory ones. One element is still connected to the grid and the other two to PV. An additional thermostat has to be added for the PV. Going full safety really complicates wiring. I have a friend with grid tie system, and he operates his controller right off the panels. Not only that his dryer heating element is also connected. When he turns on his dryer, the controller switches from water heating to clothes drying automatically. This is advanced stuff. He even charges his car from PV without going thru grid tie. Florida lots of sun. I'm off grid and my water heater switches to the dishwasher when running.

 

[Larry Oswald]

The heating elements must be electrically isolated from the grid. Often just the lower element in a tank is connected to PV. There are three phase elements which can replace factory ones. One element is still connected to the grid and the other two to PV. An additional thermostat has to be added for the PV. Going full safety really complicates wiring. I have a friend with grid tie system, and he operates his controller right off the panels. Not only that his dryer heating element is also connected. When he turns on his dryer, the controller switches from water heating to clothes drying automatically. This is advanced stuff. He even charges his car from PV without going thru grid tie. Florida lots of sun. I'm off grid and my water heater switches to the dishwasher when running.

Cool ideas for hot water. I had not thought of using just one of the heating elements. Checking my Whirlpool the two elements are each 4500W but it seems they are never used simultaneously as the total rating is 4500W. A full 4KW water heater would overload my system. Running at 120VAC would cut the power by 75% to about 1250W. That is doable but still 10A (not 20A). Heating much slower of course. What controller is your friend using?

 

[efficientPV]

That is the nice thing about running from panels, it doesn't use any of the existing charge controller, inverter or battery. He is using a slight variation of my design with components which work up to 400V. I designed for 200V, an array of 60V to 160V. This is my garage system with a 40 gallon just used for laundry. My array is only 60V. Both existing elements are 4500W and are in parallel with each having a thermostat. Tall tanks are ideal for solar as the top 15 gallons heats easily. Not much hot water is used at one time. The lower section is pre heat and at lower temperatures there is very low heat loss. Pre heating cuts down on response time. water easily temperature stratifies. Hot water in the house has priority after other house needs are met. The garage has lowest priority. With laundry happening only every two or three days it is enough time to store hot water for one or two loads.

 

[Whats-n-Watts]

These guys have you covered. Including DC thermostat control.

DC Water Heater Elements | Missouri Wind and Solar

Choose from a wide variety of submersible DC water heating elements for direct connection to your batteries or solar panels. Great for RVs, heating stock tanks, or converting your AC water heater. Don't forget to add a thermostat.

windandsolar.com

 

[rhino]

These guys have you covered. Including DC thermostat control.

DC Water Heater Elements | Missouri Wind and Solar

Choose from a wide variety of submersible DC water heating elements for direct connection to your batteries or solar panels. Great for RVs, heating stock tanks, or converting your AC water heater. Don't forget to add a thermostat.

windandsolar.com

There has been some bad reviews of that place in past and what they sell.

 

[Whats-n-Watts]

There has been some bad reviews of that place in past and what they sell.

Good to know!