Matching Water Heater Elements to Solar PV Panels

It's hard to match the solar PV panels to a water heating element. When I first hooked it up I was all wrong and didn't make much power. But thanks to a friend (Chris), I now have a clear picture of matching PV to heaters. I needed to find the Ohms, Ω, of the resistor.
This is part three of my video series comparing solar thermal to solar PV for heating water. At the end of the experiment I will be sharing my data in case you would like to give this a try.
Now I have three PV panels hooked together in PARALLEL. This keeps the volts the same, but adds the amps. This combination of panels makes the right power for my heating element. I bought a 48 volt, 1500 watt element for this experiment. I am using Y-connectors to make the parallel connections between solar PV panels.
This is a direct connection from panels to heater. There is no MPPT controller in between.
Thanks Edwin for sharing your off-grid system. Edwin is using 6 solar electric panels in parallel to a tank style water heater. e-mail: [e-mail]
I built a free calculator to help everyone out. This calculator will suggest water heater elements for you based on your solar panels.
You will fill in the Volts, Amps, and series/parallel connections. The calculator does the hard part for you. Look on the back of your solar panels for the "Vmpp" and the "Impp". My FREE online calculator is on my website: www.davidpoz.com
Product links:
MC4 Cable: amzn.to/2Ic8UtR
MC4 Tool: amzn.to/2Gw2DGD
MC4 Y-connectors: amzn.to/2MVbAuj
48v1500w Element: amzn.to/2MUiIqZ
Multi-Meter: amzn.to/2MYxcpW
“As an Amazon Associate I earn from qualifying purchases.”

[@dudu4027]

Thanks for the vidéo. One option to increase the number of panels in series is to transform your 48v into a 96v heating element: Remove the two busbars and add a new busbar in diagonal; the two half heating éléments are now in series instead of parallel. Regards.

[@eastofoz2400]

Thanks for doing this research. I had been thinking on diverting power once batteries are full and the part I was missing was the heating element impedance and the heating element adapter. I thought of buying a tap, but this is much easier and cheaper. Appreciate what you do!

[@solarfluxman8810]

It's called impedance matching. When the source and the load have the same impedance (in this case resistance in ohms because it's DC) maximum power is transferred. Resistance is found by volts/amps = ohms resistance = volts^2/Watts (This is useful for the heating element). Good job with your video. New subscriber earned.

[@unionse7en]

..another way of looking at it....he tripled his voltage in series, but he was still limited to around the maximum of 9 amps that each panel is rated to output. In parallel he had triple the amp output capability as needed.

[@paulterry1921]

Yep, it hit the short circuit current limit, isc, but your man is still correct about maximum power transfer and impedance matching. It's why you have to tell your amp what impedance speakers you are using.....4 or 8 ohms etc. Really enjoyed vid thank you..

[@rogerphelps9939]

You might think you are transmitting maximum power, but the problem is that you are dissipating half of what you are generating within the solar panels. Power generation and distribution systems most certainly not designed like that. What is required is a DC to DC converter that maximises the voltage across a fixed load for any given input.

[@7sotos]

He should wait then at least a minute to allow impedance to be reduced and eliminated

[@mlg779]

This is probably the best solar hot water video on the internet. Thank you for the calculator.

[@gvmiketodd]

I really appreciate that you are willing to share your mistakes. No one is perfect but some people find it really hard to admit that they aren't.

[@DavidPozEnergy]

I appreciate you saying that, thanks.

[@p.brooksmcginnis1749]

@@DavidPozEnergy Hi David; We all are learning & most do make mistakes. It is a learning process. Love from Oregon

[@vigneaswarmj9257]

Well said

[@johnstone-gh9nj]

@@DavidPozEnergy Dave, Is It still working good.

[@marksaustralia6464]

Funny that those who casually concede non-perfection are those we confidently listen to. Why? Because the attitude toward uncomplicated concession, is also a badge worn that says 'No BS here!'

[@kevinroberts781]

Great video David! You are one of a select few worth watching! Can't wait for the next update!

[@DavidPozEnergy]

Thanks for watching.

[@MastercraftKARIGAR]

Great video David Lots of hard work. Thanks for sharing.

[@Jonathans_opinions]

Thanks! I started figuring all this out on my own, then I found your channel, and it’s helped a lot!!

[@TWmarkjohns]

Thanks, David, very handy video and thanks for the calculator man, I love seeing your munchkin helping with the builds, all the best Mark

[@pgo301]

You know I respect and appreciate that you have no embarrassment about admitting your mistakes, unlike too many others. And I am grateful that you did all this legwork for us in these Excel spreadsheets, which I will be using when I get further ahead in installing the panels. So Thank You for all your efforts and your true unselfishness.

[@DavidPozEnergy]

Your welcome. Thanks for watching.

[@leighamos489]

You're doing a great job Dave not all of us have an engineering background and I find layman's terms is the best way to explain to the rest of us thanks again for having the patience to do this test

[@DavidPozEnergy]

Thanks for watching. It's fun when my butt stops hurting from kicking myself. :)

[@flyty2134]

I enjoy your videos what I like about the most is when you make a mistake you admit it but more importantly you go through and explain what you did wrong and how to correct it that’s what makes your videos great.

[@DavidPozEnergy]

Thank you.

[@Nodularguy1]

Many thanks sir ! I am in the process of designing a solar electric add on to my existing gas water heater. Your calculation chart will be amazingly helpful!

[@DavidPozEnergy]

I'm glad it can help.

[@opera5714]

Recently I read a university paper that reported MPPT had a 20-35% advantage heating water over DIRECT CONNECT. That makes sense since you have seen that number referenced for charge controller. It stressed how location was key given different weather conditions. Why bother with that extra electronics when direct connect is so simple. The study however was deeply flawed. It was not done by solar people. Total heating over a year really doesn't matter. You want hot water every day regardless of weather conditions. Here is a real comparison between MPPT and direct connect of heater elements. For simplicity, a 60V 10A array and element to perfectly match that. Solar panels are current sources and the voltage of them is based on the load resistance. MPPT 10A 60V 600W DIRECT 10A 60V 600W MPPT 5A 60V 300W DIRECT 5A 30V 150W MPPT 2.5A 60V 150W DIRECT 1.2A 15V 38W As you can see, MPPT greatly outperforms direct connect in less than ideal conditions which happens most of the time. Higher resistance elements overall may work better in direct connect in lower light levels.

[@tonyblighe5696]

I am struggling to find a suitable MPPT controller that is not a charger. Any ideas? Thanks.

[@Jnshaw81]

Great job with the "IF" and "AND" functions/statements! Not too shabby for not being good at computers! Fun series David, thanks.

[@DavidPozEnergy]

It took me three days of watching Excel tutorials to figure that out. LOL.

[@CrankyCoder]

Very cool! can't wait to see how well it all works out!

[@loafandjug321]

This guy seams genuinely perplexed.

[@starckmad1779]

Good stuff as always, David.

[@scottmcintosh2988]

Great experiments thanks for sharing your findings ! Scott from NH.

[@OurSoVaLife]

This is great info. Very valuable and time and headache saving. Thank you so much

[@SuperJamster1]

Thank you. I was thinking the same line of thought as you and would have done the exact same thing. I realize panels are based on ohms but my brain thinks of them as battery's positive and negatives. This just saved me a lot of overthinking.

[@DavidPozEnergy]

Glad to help. Check out the spreadsheet on my website to make it even easier. www.davidpoz.com

[@dmpme951]

the most useful solar video.. you deserve to get 1 million hits.. thank you for the info.

[@DavidPozEnergy]

Thanks.

[@JAG9100]

Why are monks so good at protesting? more ohms means more resistance! looking good David! i like this series

[@DavidPozEnergy]

LOL

[@jasonoliver3548]

Yeah, but do you like the parallel?

[@ljprep6250]

@@jasonoliver3548 Seriesly do.

[@ljprep6250]

(groan)

[@patriciogana1685]

Thank you David! Very good information! Greetings from Chile! Be safe!!!

[@xanataph]

The impedance of the source must equal the impedance of the load for maximum power transfer.

[@martinultimatevw3779]

Great info! Got me interested in pv heating 👌

[@centralplumbing4397]

You can also heat water using a 12/24v DC element(Dernod-AMZN) directly from load output, and/or a low wattage 120v element run off of your inverter. My system: 40A Epever mppt charge controller, Outback FM80, a 40 gallon dual element water heater, a 300w 24v DC upper element and a 750w 120v AC lower element(Dernod cartridge heater-AMZN) with a 1''x1/2'' brass bushing.(2) 325w panels connected to (2) 100A 12v batteries in series running off of the Epever. (6) 325W panels on the FM80 connected to a 5k inverter run thru a (5.5k MOES-AMZN) utility/inverter AC transfer switch powering the 750w AC lower element, and selected AC loads(and washing machine/ LPG dryer). lower AC element controlled by thermostat and a timer from 9AM to 10PM(10PM cutoff is to insure some hot water for morning showers). Upper element controlled by charge controller's programmed load output 9AM to 5PM. Between 10AM and 3PM 300w DC element can produce over 400w of power, up to 3.5kw a day. AC element thermostat usually shuts off by 3PM. On cloudy/rainy/laundry days hot water is automatically guaranteed by utility power. Payback? 5kw> daily electricity savings. 2 years now no glitches, 4 person adult household. Do not waste money on solar water heaters of any kind.

[@ajarivas72]

I like your comment

[@mdnazmul-mianazmul1401]

You're mission good. Thank you guys for this amazing video.

[@uprightfossil6673]

Still over my head, but subscribed anyway so that I can learn from someone who is also learning.... To do it right! Good stuff here

[@amettamail]

Thanks for making this video! Finally the explanation I needed. Cheers!

[@TrackGeeks]

I think experiments like this are fantastic learning platforms. Sure you can buy a power controller that takes the guesswork out of it but that also robs you of the experience of learning about this stuff. How solar panels make power is something that this experiment really demonstrates. Solar panels do NO act as batteries do. They have a very high equivalent internal resistance in comparison to a battery or a heating element. When you couple a current source with a high internal resistance with a load that has a low resistance the system voltage will go wherever that low resistance load takes it. I don't think there is any expectation that this experiment is going to yield the maximum power from the solar panels. What it does demonstrate is that with a little understanding of how this stuff works you can put together something that is functional even without a bunch of electronic wizardry.

[@jasonoliver3548]

Careful everyone, where I live you need to size your wires based on the "Isc" (short circuit amps) not the max power amps!

[@andycordy5190]

😂Thank you for your generosity in sharing this. I'm learning so much. I have a dread of electricity but the principles are easy to understand.

[@raymondjones7489]

Thanks for the data...trying to learn!😊

[@kokopelli314]

I've been using a 12 gallon water heater as a shunt load for a couple years. My panels are always in parallel. I use a 1600w boost converter on the shunt output of my MPPT or sometimes directly from the panel box. The heating element is switched from a 200A relay controlled by the tank thermostat through which I run 24vac from a small transformer. The element is a cheap off the shelf 1500w 120vac. Its run flawlessly for 2 years after being in AC service for 3 when I was on the grid. I usually run it at 80vdc. I've also run it directly from the inverter, but I like to keep it separate.

[@jimh712]

Sir I'm new to your channel Stumbled across you. 😃 Totally enjoyed your comparison. and all the data...on heating water I don't know if you've realized another application for your research... I've been thinking of raising Tilapia.. But they need between 60°-80° F. And they take around 270 days to raise.. So the problem is to provide heat... You Sir have solved that problem...😃 You have provided me with the missing pieces.. Once I get off the grid and time.. I can develope my endless supply of Tilapia... My lady is going to love you... and your staggered stud walls.. I've been thinking of for some time.... and you've solved the insulation problem.... again thank you.. You have a new follower 👍👍👍👍😃😃😃👍👍 Thank you again

[@DavidPozEnergy]

Glad it is helpful.

[@solarforfuture]

got a bunch of free last gen pv panels... direct to water heater for showers and spa... then some for dc sand battery with range top elements and air heating fans for the hvac system, great channel . thanks for the tip on signature solar out of texas.. off grid in town. as nat gas price spiked 3X in SoCal

[@Solar_Tech_Liam]

All this comes down to is Ohms law, which is why you should learn math kids :-) Since a solar panel is a current source rather than a voltage source, it's output is dependent on the load's resistance, a charge controller or MPPT tracker tries to dynamically vary the load resistance to best match the ever-changing power point of the array, this is not always possible. The challenge with using a fixed resistor is that you only get peak efficiency at MPP, that may only happen during the peak of your solar window, meaning you are missing out on power during the early and late periods, the other challenge is lower irradiance conditions like a cloudy or overcast day will create a mismatch, for a water heater it's probably acceptable. The calculator is certainly handy for finding elements, but all you have to do is take Vmpp over Impp and you get your ideal resistance (E=IR or E/I = R) I say ideal because this MPP is constantly changing under real-world conditions. Nothing like the hard teacher of experience ;-)

[@TheRainHarvester]

Liam O'Brien , can putting dc in an ac heating element cause electrolysis? I realize it is mostly a short but wonder if the element is inside a steel jacket that is exposed to the water. I'm asking because someone stated it could cause electrolysis on his later video. (Not sure if I believe it, but I've been surprised before.)

[@teardowndan5364]

@@TheRainHarvester AC vs DC makes no difference since the heater consists of an outer steel sleeve, a ceramic electrical insulation jacket and the heating wire in the middle. Unless the steel outer jacket fails, there is no contact between the electric heating wire and water. If AC was allowed to be in contact with water, your whole water tank would become a potential shock hazard.

[@ratgreen]

So would the better solution be to use a mppt solar charge controller, and use the battery as the heating elements power source?

[@dejayrezme8617]

@@ratgreen Ideal would be an MPPT suspended inside the water heater haha. That way the inefficiency of the MPPT transformer as waste heat heats up the water too! 100% efficiency! :D I suspect it's cheapest to size your heating element for 50% illumination, then higher voltage will be only a little bit less efficient but you want it to work best in winter etc. Summer won't be a problem. So you'd use the Vmpp for 50% illumination instead which you can find in the datasheet of a solar panel. And you can always add more solar panels which are cheaper in the long run that MPPT. If you have the roof space. Also don't add 25% safety margin for sizing your heating element... it's not like it's going to burn through inside of the water lol. The watt rating is mostly meant for the power it produces at 240V.

[@thedillestpickle]

@@ratgreen That's a good question I was wondering the same. Then you would have a known voltage of 12 volts and could determine your ohms to optimize for that

[@AveRage_Joe]

Excellent Video! Thanks for sharing! 💥

[@johnburlake1229]

The exact info I was looking for, thanks!

[@zenzen9131]

Great information regarding the 240v element as here in the UK these are a lot cheaper than the other types :)

[@TheGhungFu]

What type of heating element are you using? DC elements are very different from standard AC elements, generally much lower wattage, and quite expensive. A 3500 watt AC element costs $15-$20. I've been off-grid over 20 years now and dumping excess PV production into hot water for about 15 years. Here's my setup: My PV system, about 7200 watts, charges my big battery bank via 4 Outback controllers. The controllers have programmable relays that can switch things on and off at selected set-points. We have three inverters including two 4000 watt Trace inverters wired for 240 volts into a standard breaker panel. The big solar hot water tank has one 3500 watt AC element in it (same as a regular residential water heater, about $15 at HD). This element is wired to the main AC breaker panel via a switch box with a standard 40 amp 240 volt air conditioner relay which gets switched on and off by one of the programmable charge controller relays. So,,, when the main battery bank is fully charged according to my set-point, the relay switches the water heater element on, dumping surplus PV production to the hot water system via the inverters. If the system's DC voltage drops below the lower set-point, the charge controller relay switches the HW element off. This way my batteries stay at full charge and surplus PV production is not wasted. I know there's a conversion efficiency loss, but it's surplus power. No big deal there. I run other things DC direct (this computer for instance) but learned to not obsess over that. The inverters are each producing less than half of their rated output to making hot water so are not getting stressed, and the system is not drawing down the battery bank; only using surplus available PV production, generally after noon.. PV is doing double duty without sacrificing any performance. Our solar tank is 450 gallons and is also heated by a 60 evacuated-tube solar water heater. We never run out of hot water. If the water tank gets to its high temp set-point in winter, a temperature relay switches a pump on to circulate hot water through our warm floor system. In summer, we usually have the PV to hot water dump switched off and use the surplus for air conditioning in the afternoon (another system I built to utilize surplus PV). This system has worked flawlessly for over 15 years, and, with some scrounging, was quite affordable. Off grid. No power bill. No water bill (water also pumped with a separate PV panel). No sewer bill, no mortgage. Part of our retirement plan. Yes, we have to adjust sometimes for cloudy spells, but that becomes habitual; minor lifestyle changes. All of that money saved can go into tax-deferred savings, or a more relaxed lifestyle. When people calculate savings that way, they can add a 35%+ premium because every dollar we save would be taxed at around that rate. Be sure to account for that in your calculations. In other words, if you are spending 200 dollars per month on retail energy, you had to earn that PLUS enough to pay the income taxes on that amount, say $270. If you didn't have that bill and put that money into maxing out your tax-deferred savings, you aren't paying those same taxes, and can earn something instead. Most folks don't look at it that way.

[@jimhofoss9982]

TheGhung Fu don’t matter, ac or dc...ac element will work just as good

[@volador2828]

Funny, I do the same. I have the outback chargers...also the trace inverters. Two 4000 watt units and one 5000 watt trace unit. They work fantastic. What we don't spend on retail goes into savings like you said! No water, electric or sewer bill, no cable bill. We only have internet! Radiant heat and a rocket stove water heater on emergency basis. It really does not get better then that....

[@That1ufo]

From my research the is no such thing as a dc element, its a marketing con with a DC sticker slapped on, you just have to match the ohms ect.

[@TheRainHarvester]

Nice cost benefit summary. More people should consider MTR, like you did! I can tell we would enjoy taking too each other! I'm near Austin. Check out my videos.

[@climatechangepreppersfaceb2148]

A DC element is very different. It has different coatings to prevent electrolysis. Get educated

[@andrewdeming141]

It is not the resistance of the heating element that is important. It is the power curve for the panels that are being used and providing a load that matches. For each point on the power curve a rectangle can be drawn that incorporates the X and Y axis as two sides of the rectangle. The area of the rectangle represents the power for each combination of the Volts on the Y axis and Amps on the X axis. The point in the curve that matches Vmpp and Ampp specified for the panel will define the largest area rectangle and therefor the max power output. (The power curve provided by the manufacturer is for a specific energy level landing on the panel and is specified in watts per square meter.) The points on the curve indicate the maximum power for all possible combinations of possible watts and volts. If all days were sunny and the panel or panels were operating at the and full power max power point then a specific resistance load could be chosen for that power point. All days are not bright sun and the max power point will move along the curve. To achieve the maximum heating power from the panels an MPPT controller is necessary. This controller will adjust the output voltage and current to create the largest area rectangle to extract the most power from the panel for the Watts per Square meter available from the sun. If you wish to do an accurate comparison between solar panels with heating elements and a water heating solar panel, your not only need to take into account the solar collection areas for each system but also insure that each system is operating at maximum possible efficiency for all conditions. The water heated panel simply absorbs whatever watts are available and transfers heat to the water. (More heat will be transferred if the temperature differential between the water and the panel is greater.) Some heat is lost to the surrounding air due to conduction. (Air temperature will not cause any less heat being transferred from the solar panel to it's tank.) The solar panels and heating element will not be operating at maximum efficiency unless an MPPT controller is used to match the source to the load. Cold temperatures will negatively affect the output of the solar water heater but the low temperatures increase the efficiency and output of the solar panels.

[@dudu4027]

That's 100% correct. However, that s a good compromise, if you want a low cost system with second hand panels and without expansive MPPT electronic.

[@mckenziekeith7434]

If you select a resistor that is close to Vmpp/Impp you will be getting close to the max power out of the panel with that resistor. (Ideally you would adjust the voltage and current to better reflect your actual operating conditions in terms of insolation and panel temperature). The actual technique that they teach in school would be to find the intersection between the V-I curve of the resistor and the V-I curve of the solar panel. To get maximum power, you want this intersection to occur at the maximum power point of the panel. It is called the load line technique. Of course, if you add panels in series, then you need to multiply Vmpp by the number of panels. And if you add them in parallel then you need to multiply Impp by the number of panels.

[@Psi-Storm]

@@mckenziekeith7434 You could get 2 heating elements. One for summer with a resistance matching close to Umpp and Impp. And another for Winter with double/triple the resistance to get a better mpp around 1/2 Impp. A microcontroller could then switch a relay between the two, depending on measured voltage, or just a manual switch for the "normal" people.

[@Swampwild1]

Psi Storm right. We all need to learn how to make these controllers work anyway.

[@darrenparachoniak7878]

Lots of MPPT CHARGE controllers out there. I'm thinking for a direct element hook-up a charge controller wouldn't be the device to use? Help!

[@erichertsens]

thank you, saved me a lot of experimenting.

[@josidasilva5515]

You can wire it in parallel or series, as long as the heating element is rated for the sum of the Voltages, and/or the wires are rated for the sum of the currents.

[@Sydneyadventuretours]

Awesome video bro way to learn from your mistakes! Keep’em coming

[@DavidPozEnergy]

Thanks.

[@nexxtron2423]

I was looking for this for a long time. I too had the same problem. I will try it now

[@mark_osborne]

Just awesome- love the spread sheet !

[@DavidPozEnergy]

Thanks Mark, Did you try plugging in your numbers from the panel in your recent videos?

[@mark_osborne]

@@DavidPozEnergy I'm sorry, I tried. I refuse to pay Microsoft's annual fee to open an .xls file and I have a .xls reader (a program I downloaded from the internet) but it won't 'operate' your file. It opens, but I can't plug in numbers. Sorry.

[@DavidPozEnergy]

OK, thanks for trying. Someone in these comments mentioned another program called "Google docs" I'm going to try to learn more about that today. I don't know if that also has a fee or not, or if my file can translate, but I'll let you know.

[@ksnax]

Awesome work on the calculator!

[@DavidPozEnergy]

Thanks.

[@jazjobse946]

Great to see so many lateral thinkers on line . 😀

[@terryfischer7988]

I like this experiment very much..... I did plug in the specs on a single 100 watt panel (17.8 volts, 5.62 amps) and it recommended "48 Volt 600 Watt 8 5/16 Inch DC Submersible Water Heating Element", but if you look at the specs on the element, it says the wattages below. So obviously one 100watt panel is not big enough for the real world, but it does show how you really better do your homework when picking out a solar/element combo if you want to maximize your output. can also be wired for 12 Volts 40 Watts can also be wired for 24 Volts 160 Watts can also be wired for 36 Volts 360 Watts

[@slrs3908]

Awesome video! Surely have saved plenty of folks time, money and frustration with the info and spreadsheet. Oh, and copy and paste the Amazon links. Works fine.

[@dgmenace73]

Thanks! A big help to my system!

[@oldmgbs2]

Good job on set up and video.

[@DavidPozEnergy]

Thanks.

[@leoprisionero]

Very informative and helpful

[@GCSol]

I used your Excel calculator to figure out what size element I needed to match up with my solar panels. I hooked everything up four weeks ago and use a Raspberry Pi to monitor it. I set it up so the solar panels keep the water heater between 130 - 138 degrees. During this time, the water heater has only turned on once for seven minutes (only because it was a rainy day).

[@mohamedsheikh2502]

Thank for this great info.

[@srenhansen3694]

Thank you, helped me a lot.

[@mohamedsheikh2502]

thanks , David for sharing this info:

[@DavidPozEnergy]

Your Welcome

[@Cjudd001]

PV is current limited. You will never achieve more than the ISC. Its great that you learnt from this. I experienced the same thing about 3 years ago . I placed 10 x 250W panels in series with a vmp total of 310V @ 8 A IMP or 2.5kw in panel roughly. The most I would get to was about 80V @ 5A. the original element was a 3.6KW element which would need around 15amps... So I used a ohms law calc to find out what R value I needed to get 8amps which was ideally a 30 Ohm element or a 1.92KW 240V element.. The closest available is a 1.8kw element so I used it and I did get favourable results but you then have the problem of swithing off 300V dc for thermostat control... Anyway long story short is yes you can match and make PV drive a HWS but the efficiency is much lower than most solar HWS setups. Ie. PV is around 16% efficient minus cable losses etc where Solar HW is up around 70% efficient. Yes PV wont freeze and burst lines hahaha. Nice video!!

[@DavidPozEnergy]

Sounds like we both went through the same thing. I laughed at the "PV won't freeze". I've had a frozen solar collector and it caused my system to be down for three weeks. Thanks for watching.

[@mondotv4216]

DavidPoz You had a PV panel freeze? I thought it was a thermal panel?

[@DavidPozEnergy]

Hi MondoTV. Yes, I had a thermal collector freeze: kzbin.info/www/bejne/bnixc3iirL2cZ5Y That is why I agree with Clint that a PV panel won't freeze. At least not in any damaging way that my thermal collector has frozen. Several people have written in on that other video sharing that they also have experienced freezing problems even in systems that were installed properly. It seems like PV has less that can go wrong.

[@mondotv4216]

DavidPoz Sorry mate - your reply seemed to imply that you had a PV panel freeze LOL

[@larryteslaspacexboringlawr739]

thank you for solar energy video

[@offgridwanabe]

Thanks for the info and spreadsheet

[@DavidPozEnergy]

Your welcome, thanks for watching.

[@mrphysics2625]

I cried for a split second when you said you put them in series :(

[@TheEkvilibrium]

Nice, thank U for detailed instruction and calculator! Greetings from Ukraine!

[@alexbik]

The thing is that PV panels give you a voltage that is more or less stable and a maximum current that depends on the amount of solar radiation. By rewiring your setup the heater works now, but if the amount of sunlight changes you may be back to square one. Here's why: Let's say it's partially cloudy. Your panels will still give you roughly the same voltage (about 0.5V per cell), but the maximum current drops. Your heater is basically just a resistor, so the amount of current it wants to draw is going to be the same as on a sunny day. But on a cloudy day your PV panels are unable to supply that kind of power. As a result, the voltage drops dramatically and your power drops even more (Power = Voltage squared devided by resistance). What you need is a Maximum Power Point Tracker (MPPT) that will actively search for the optimal current to draw from your PV panels, where the power (current x voltage) is the highest. This point depends on the amount of solar radiation.

[@josepeixoto3384]

**THAT** is very true; the ONLY way it may work,is if you DOUBLE the panels you actually need; and even so, in WINTER, do not count on it,no sun; summer no problem; here in SW Europe(Portugal) i was without ANY sun( well,around 40 watts... lol) for 11 or 12 days, now in March; the whole winter i had to be plugged in to the electricity supplier most of the time; they are called SOLAR panels,not light panels;no SUN,no juice, light alone does not cut it,you need SUN, the one that makes SHADES of things, not just light; diffused sunlight thru the clouds gives you 1/3rd IF the clouds are like cottons,white,if they are dark,almost nothing; After 2 years i regrett i spent all that money in 6 panels,MPPT, inverters (breaking down twice!!) very expensive lifepo4 batteries,and..countless hours; not worth it,and it ROBBS you of your Peace Of Mind;

[@njm663]

Hi David, I'm building a house for me and my wife, i have aplan to mount a solar energy, the house is 300 meters from the sea. Is a hot land, i will need just raise the temperature from 25 to 40 degres celsius. Afetr see your videos, i decided use 3 330 pannels dedicated to use in my hot water needs. As you show, is possible use just 1 48v heater element, 1 80amp SSR relay, 1 Timer, to on off, I need something easy, for me does not metter, if is eneficient. I have sun all day long and 300 days. Thank you so mutch for your generosity to share your knowledge.

[@MastercraftKARIGAR]

Today b4 seeing your video I tried to find out mpp resistance for 4x150w 12v panel. Which is 9.25 Ohm.

[@FixItYerself]

great information

[@sjdtmv]

Your 48v DC element is a two 750W 48V elements in one , if you change the bridging tab at the element, you can change that 48V 1500w element into a 96V 1500W element, this way you don't have to have run with a larger current, and can work with other panel configuration. I have work on the 36V elements and changed them also to a 72V element by changing the bridging tab around on the element. so with these elements you can have 36V, 48V, 72V, 96V elements

[@jefferyshall]

Spreadsheet is genius!

[@DiscoCzarnobyl]

Very useful, thanks!

[@DavidPozEnergy]

Your welcome, Thanks for watching.

[@mikevincent6332]

Fitting a high efficiency switched mode charge controller may help even more with ideal matching between panels and load, by acting as an impedance matching system. It would depend on how mismatched they still are after wiring for ideal matching etc, etc

[@rockybass3129]

Wondered before about heliostats and heating a central water volume for running steam tubines. Like some industrial scale facilities. I know it's not super simple to pull off but it seems doable.

[@Uglydollsrises23132]

#hiddenbattery The spreadsheet is awesome! This is a great "freebie!" for those who are "Ohms Law" challenged.

[@thedillestpickle]

V=iR

[@thedillestpickle]

P=i^2*R P=iV That's all you really need to know

[@a787fxr]

Thanks for the info. !:-)

[@dejayrezme8617]

I think the 25% safety margin is wrong, the power rating specifies how much power a heating element will produce at 240V. But at 500V it would still be fine since it's water cooled! The safety margin will just screw up your efficiency. PS: Thanks for all your awesome videos!

[@innaslyusarenko]

David, I sure hope you are still talking to Kameron Cuk and you guys will somehow try that special Mppt for the water heater. I also bought one and now I am waiting for when I am able to buy the panels. I understand I would need three 200 watt ones. I watched all the videos available about this MPPT, including Engineer775. I believe that he covered efficiency pretty well, with all pros and cons. Well, I would still feel better if somebody tried it first and lived to tell the tale.

[@stewartrv]

Only thing to be careful of is that you must take into account the voltage doesn't exceed that stated on the element. For example if you tried to use three or four panels in series with a 12v element you can't be sure that the insulation won't breakdown - it will probably be fine, but you cannot be sure. On the other hand if you are always lower it won't matter.

[@craigcarman354]

Well done

[@nhikoid]

Brilliant!

[@james007nhstbrice7]

David Great video Im late to the game how do you connect the 3s 1p panel that option look great thanks

[@scottbillups4576]

Liam O is on the right track. Your heating element is such low resistance that it is drawing a lot of current, an that is collapsing the voltage of the panel. A slightly higher resistance heating element, would not collapse the voltage as much, and you'll end-up with more power. The Volts/Amps curve of a panel will show you: 1) what the voltage will be, at different current draws from the panel. 2) You'll see where the maximum power point will be (basically Imax and Vmax on the data sheet) 3) you'll see that the VI curve *varies* with solar illumination and panel temperature. This means that where the maximum power point is, will constantly move around (different current draws) depending in illumination and temp. That's why the industry created MPPT inverters. MPPT will constantly apply different current draws to the panels, to find the current draw where it can pull the maximum power. For your setup, please just go buy 2 or 3 MPPT inverters (DC output), and let them track the amx power point for you, and heat the water as much as the sun+panels can offer you.

[@DavidPozEnergy]

Hi Scott, I agree that an MPPT would be great. Can you please link to a proven one that would work in a direct to load connection? Remember, there are no batteries in this setup. Thanks.

[@root4669]

You can also put multiple elements in parallel to reduce match the ohms, or in series to increase it.

[@neliosamch3195]

David Very interesting. I have to change my water heater's thermostat to a DC one because it was popping off and the safety valve blew off 3 times with boiling water. I use my water heater as a diversion from my 2p 3s pv pannels 48v charging system. Also, it will be interesting an experiment that proves pv pannels can make 10 % or more electricity when in horizontal position and the reflexion of one panel over the other. In the summer about 1500 watts but in the winter when I raise the top panels they make over 2kw.

[@DavidPozEnergy]

That's scary, but glad you had a safety valve to blow, and not the whole tank.

[@greggoryleblanc1024]

How many panels and elements would I need to get a 50 gallon drum to run at a constant temp of about 140-180 degrees during the day? Goal is to heat radiant floors during day then switch to boiler when sun goes down.

[@NaughtyGoatFarm]

Am I correct in thinking that one benefit of going with a 3s 1p setup is that the overall amps drop? Does this mean that you can use lighter duty wire?

[@briant7960]

Thanks for your videos, I'm confused now that you have gone back to series to find different elements. Does anyone know which way works better using 2x350w panels, an mppt and a deep cycle marine 12v battery? Calculate in series is 8.7 ohms and in parallel is 2.1 ohms....

[@realmenard1318]

Thank you man

[@johnaugsburger6192]

Thanks

[@ai4px]

I'm doing my pool house this way... 3 255w panels in series and a 1500w heating element in a 20gallon water tank.

[@thedillestpickle]

It will boil

[@johanhelberglongbowsknifes1185]

Hi, David awesome do you got calculator 2 ready tune it up. Great work

[@petski999]

To continue my notes on PV constant current sources, even with the paralleled panels which can now overcome the low resistance of the heater in full sunlight, if there is any overcast or the sun angle is not optimal the voltage will collapse again as it did in your first attempt. This means you will only heat effectively in direct sunlight.

[@galactophore]

thank you

[@hansdampf3011]

A 1kW MPPT controller would be great for this application. The MPPT controller will always find the best working point for the load independently of the load resistor. He will always adapt the resistance of the source to the resistance of the load to get the MPP.

[@kreynolds1123]

When Designing a system, choosing an element that would work with ones panels in series might be better than choosing an element that requires adding panels in parallel. That is because higher voltage less current through a given line looses less power over over the distance of a given power line than lower voltage higher current.

[@1magnit]

Voc = 47.7, ISC =9.92, R =4.8 Max power transfer is when R (load) = R (source) so you really need 6 panels either as 3 pairs or 2 triples

[@user-pi8us8dp3b]

thank you for the pure science and facts . So much opinion in videos these days and they are so sure... and still wrong... thank you.

[@kendenzer9263]

Your awesome.

[@ImiChitterman]

thanks for everything

[@DavidPozEnergy]

Your welcome, thanks for watching.

[@LordGryllwotth]

The element can change ohms when it get hot. I learned that when we did experiment with lightbulbs in school.

[@TrackGeeks]

Absolutely true! At these temperatures the difference in resistance between room temperature and 100C is going to be a fraction of a percent. Since a light bulb goes from room temperature to a few thousand of deg C the shift in resistance is much more noticeable.

[@ursodermatt8809]

he hasn't got a light bulb filament inside the tank. it is a heating element. the resistance of a hot water element just goes up slightly

[@goranstankovski]

Hello Your videos are great. If you find time i would really appreciate if you would answer these questions: Are you satisfied with the result? Are you getting enough hot water? Does the system have capacity to heat up the water? And to what temperature the water is heated? Thanks

[@DavidPozEnergy]

Thanks for watching the video. It was a great experiment. The next hot water tank I build will definitely be heated with PV. I have another video that will probably answer more of your questions: kzbin.info/www/bejne/gYfIeKijotSLiZI