Yeah I do agree, most of them seem to go out every few years. If I were trying to make hot water from solar personally i would store the energy in battery form and use a heat pump water heater for producing hot water, or use some form of direct water heating like the black hose method. if need be connect it to a plate heat exchanger for higher temps at the outlet. It seems like his method would be most practical when building from scratch as you mention, or for Commercial operations perhaps. Another possibility might be using one of the mini-splits that uses water as a medium to transfer energy, a couple of them I have seen have a tank that can be connected in line to heat water from the heat that is being pumped out of the space being cooled.
Direct to water heating.
- Thread starter Keith C
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My goal was to have a place to put the energy when the batteries are full, and no grid to sell it to.
efficientPV
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Yes, sometimes efficiency isn't the deciding factor at all. I would find it nearly impossible to use a HPWH in my situation at camp. I have one at home I supplement with PV resistance heating. It acts as a super fast dump for excess energy. You need to look at the fine print for the claims on these. Adding a battery and inverter makes it pointless. Of all the technologies PV heating is the most suitable in my system. My system seems to be totally lost on viewers. They all want stand alone systems for water heating. While this make a lot more sense than having the home office on solar, it is not the point of my system. I only use existing panels and harvest the normally wasted energy. And charge controllers just waste an enormous amount of energy. So, my water heating is pretty much FREE. How can you argue against that. This fact seems to just fly past everyone.
Even when the batteries aren't full, these is excess power not being sent to the batteries.
If I can teach just one thing it is that those who sell 12V and 24V heater elements should be lined up and shot. There are three element 12KW heating elements that will fit into a standard water heater. That leaves one element still for AC and two 12 ohm for DC, or three that can be switched in and out.
Even when the batteries aren't full, these is excess power not being sent to the batteries.
If I can teach just one thing it is that those who sell 12V and 24V heater elements should be lined up and shot. There are three element 12KW heating elements that will fit into a standard water heater. That leaves one element still for AC and two 12 ohm for DC, or three that can be switched in and out.
If you have that much solar, put in a solar hot water heater. The panels recirculate water and you then store it in a standard, well-insulted water heater tank. If you want to use solar-generated electricity to heat the water, use an on-demand electric heater - you'd need far less power.
That is a great concept and has improved a huge amount. I have one, and it works well, but there are some obstacles that modern day PV can eliminate. One is handling the liquid to the roof, and cold weather, and pumping it, and springing a leak. So while I would never discourage a water transfer system, I still like the idea of buying a reasonable cost panel and heating water. The PV panels are far cheaper now than 10 or 20 years ago.
efficientPV
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What happened to that video you were going to do?
Here is data from my garage water heater for laundry only. Remember, it only grabs energy after the other water heaters for the house are satisfied. You can see the effect of the shorter days heading into October. The big last day dip is from doing three loads of laundry. It has worked way beyond what I had hoped for. This is 8900 data points for 31 days. I ended the test because it is the end of camp season and I'm packing up.
How can i buy dmppt 450
efficientPV
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Better read the instructions real well before buying electrodacus stuff. It requires many multiple low voltage heater elements to work which is impractical for most. You likely need less than 2KW of heating. For more conventional tanks there is the techluck or AC7391. There are others even more obscure. I don't personally endorse any of them.
AC7391 video
EricBarbour
meh
Some proof would be helpful
efficientPV
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Proof! I get all my hot water from excess PV. If you have a successful PV system, it can run on bad days with storage, That means you still have enough energy to run things and still recharge your battery. That means you have extra energy on most days. Anytime you go into float the energy the panel could be producing is just wasted. Mornings when all energy should be going to the battery I still get some going to heat water. It is all hidden from you and unless some device is placed on the system to harvest it you will never know any better. People chasing after a few extra percent efficiency in the charge controller they buy are wasting their time.
Ampster
Renewable Energy Hobbyist
The batteries are what are the inefficient part of the system. If you want to talk efficiency use a heat pump water heater. Moving heat is way more efficient than creating heat with resistance.
Nothing you said proved that charge controllers waste a lot of energy.
efficientPV
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Heating water is complex and based on actual situation. Sometimes they really suck at the application and always have to have a battery. I have a HPWH and supplement it with PV resistance. PV water heating is an instant dump application and you can get the water hotter for overnight.
It is good to be skeptical. Most of what you hear on solar forums is total bullshit.
It is good to be skeptical. Most of what you hear on solar forums is total bullshit.
Ampster
Renewable Energy Hobbyist
As pointed out on another thread. Chilling water can also be efficient. I agree energy storage can be complex and it often depends on where you are standing. I presume the BS solar forums you are referring to are the thermal solar ones. There is BS everywhere but the economics favor PV solar except pool heating.
rin67630
Solar Enthusiast
Isn't it a bit silly to warm water electrically from a solar panel?
You will get 10% efficiency at its best while solar vacuum tubes get 95%. with far les complexity.
Bill Taylor
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I think that's the smartest thing I have ever heard on this forum!
You are correct. It is always bothered me that in most solar systems, the batteries are full by 1 or 2 o'clock in the afternoon. There's not much you can do about that, you have to oversize the system to make up for some cloudy days. The rest of the day, the charge controller is in float, wasting power. I've been looking for the Holy Grail forever. Something to increase the efficiency and use up some of that lost power. Eliminating the controller and using voltage controlled switches to turn on appliances is about as good as I've found. It only works if you are paying attention, though. It's hard to set up a customer's system like that, unless they are willing to pay attention to what's going on with their power. Which isn't always the case. So I end up putting a charge controller on every system. It always seems like a terrible waste.
Taking a shower with the possibility of 300voc at the faucet is one reason why DIYs suffer the high resistance loss and stay low voltage.
