UPDATE: I came back in this morning and elaborated. I was being pretty lazy with explaining the math when I wrote this, but I’ve expanded it a bit.
This is where I find a thing on Kickstarter that someone is raising money for, then I point out that it won’t work, then hundreds and thousands of people lose their money because no one listens to me anyway. Fuck ’em, it’s their own fault. Maybe they should become better at thinking.
Today’s lucky winner is called the HEATWORKS MODEL 1, and is apparently a water heater. It looks like this.
Now, as you know, I have three questions when examining a new idea that someone claims to have invented.
- Did you build a working prototype?
- If not, does your idea use existing technology?
- If not, can you satisfactorily explain what non-existing technology it will use?
If the answer to any of these questions is no, then you don’t deserve funding, or even a second glance. The reason I attached this photo is that it is, in fact a photo, which implies that they have a prototype. Of course, we can’t see any of this thing’s guts, so it might just be a plastic shell with a shiny sticker, and even if we could see the guts it wouldn’t mean that they work, but at least they’re not just playing with Photoshop and begging for money. They’re actually trying to build something.
Now, you might think that since it’s a water heater, and that water heaters already exist, inventing a new water heater would not be a difficult task. The issue is not of the plausibility of a water heater. That would be an extremely uninteresting article. The issue is one of overpromising. Let’s explore what kind of claims these people are making.
ISI Technology has invented and patented the most advanced, reliable, energy and water saving electric water heater in the world. It uses state of the art electronic technology to directly energize and heat the water molecules, rather than heating the water with old-school resistance heating elements.
That’s the very beginning of the Kickstarter description, and already there are problems. First of all, “water saving”? How could a water heater possibly save you water? It has nothing to do with the amount of water one uses, only with the temperature of that water. So already you’re just using buzzwords to make your product sound revolutionary.
Now let’s look at that second sentence. If you remove all the fluff from that sentence, it reads as follows: “It heats the water directly, rather than heating the water.” Which is pure nonsense. Most water heaters run electricity through cables, which then heat up because cables have electrical resistance, which then heat the water they’re touching. What the HEATWORKS MODEL 1 — and yes, you have to shout it every time — says is that it uses “direct electric resistance,” which takes advantage of “water’s natural resistance to heat itself.” That genuinely doesn’t mean anything. It’s possible that they’re referring to electrical resistivity, like what wire has that makes it heat up in electric stoves and lightbulbs and space heaters and basically everything that uses electricity to make heat. If they’re referring to the electric resistivity of water, they’re going to have a bad time.
You see, resistive heating only works if you can run some current through the material. If the current moves too easily, the wire doesn’t heat up much. Copper and gold are good examples, which is why your walls don’t catch fire when you have electricity running through your house. If the current doesn’t move at all, you have what’s called an insulator, like glass. Glass won’t heat up if you run a current through it because nothing’s happening. It’s like a battery in the open air. There’s simply not enough voltage to force the current through.
Unfortunately, distilled water is a very good insulator, and seawater is a very good conductor. Tap water has some minerals in it, so it’ll conduct some electricity, but it’s very hard to predict how much. The video talks about all the tech in there, so it’s entirely possible that there’s some sort of inverter that adjusts voltage accordingly, but relying on a property of water that water doesn’t always have seems like a dangerous idea.
But the bigger problem is more fundamental than that. It’s one of keeping up. Let’s imagine that you live in the US, so your wall outlets run at around 110 volts. In the video, the man says that this thing will draw current up to 45 amps. That’s a total maximum power of 4,950 watts. And that’s it. It doesn’t matter how it works, that’s all the power available to it at any given time. For the record, 45 amps is really high. My laptop charger takes in current at 1.5 and puts it out at 4.5. But the point is that we’re starting with 4,950W.
A watt is a unit of power, which is defined as energy over time. That means that the amount of energy (like, say, in the form of heat) that this object can put into water in a given time has a maximum. As it happens, a watt is defined as the amount of power it takes to produce 1 joule of energy in one second, which means that this water heater can add 4,950 joules of energy to the water inside it in a second. That’s assuming that all of the electrical energy from the wall is going into the water, which would make it 100% efficient, and obviously it’s not, but we’ll give it the benefit of the doubt for now. We’ve now established that this device can only add 4,950 joules of energy to the water in a second.
Now we’ll look at how much water is actually running through it. Imagine a shower, for instance, because that’s probably the biggest draw of hot water. My showerhead uses 2.5 gallons per minute, or .0417 gallons per second. That’s 158 grams of water. Water has a specific heat capacity of 4.1813 joules per gram per unit Kelvin, which means that it takes 4.1813 joules of energy to make one gram of water increase in temperature by one degree Kelvin. We’re working with 158 grams of water, so it’ll take 660.64 joules to make it one degree warmer.
So, how warm can we make this water? The math is pretty simple. For each second of your shower, you have 4,950 joules at your disposal, and you need to heat 158 grams of water to shower temperature. 4,950 divided by 660.64 works out to about 7.5 degrees Kelvin.
You may be noticing that that seems like a small number. You’re right. It is. You see, the Department of Energy recommends having your water heater set to 120 degrees Fahrenheit, which is 322.04 Kelvin. Since we’ve established that at the rate of a shower, this water heater can only add 7.5 degrees K to your water, that means your water will need to be 316.54K before it hits the water heater, which is 110 degrees Fahrenheit. The water in your walls is nowhere near that temperature.
The water straight out of the cold water pipes here, in Colorado, in the winter, is closer to 35 degrees Fahrenheit (according to my little thermometer). It’s cold enough to make your hands hurt just touching it. If we run that at 2.5 gallons per minute through a 4950W water heater, it’ll get all the way up to 48 degrees Fahrenheit. There simply is no way to heat that much water that fast with that little power.
I did the math backwards to show you how not-even-close this is. If the tap water is at 35ºF and we need to get 2.5 gallons of it up to 120ºF in one minute, we’ll need 31,710 watts of power. On a 110V outlet, that’s 288 amps. The breaker box for my entire two-bedroom apartment is only 300 amps. For perspective, the biggest portable generator I could find at Home Depot only generates 17,000 watts.
The problem (and it’s a good thing for us overall) is that water has an incredibly high specific heat capacity. That means that it takes a lot of energy to heat it up, and it takes a long time to cool down. That’s the reason our oceans can absorb the phenomenal amount of power (174,000,000,000,000,000 watts) that the Sun pours into them, and only vary in temperature by a few dozen degrees. It’s the reason that ice cools drinks. It’s a very unique and useful quality of water, but it also means that it’s very hard to heat it up. Think about it: a microwave operates on the order of 1000 watts, and that takes several minutes to make water hot enough for tea. Imagine if you were trying to heat up a bathtub with it.
That’s the reason that existing water heaters are so huge. They don’t heat water as you use it, they heat it ahead of time. My water heater holds 60 gallons of water, which is enough for 24 minutes of continuous shower output. As soon as I turn the shower on, the water heater starts heating, at a rate of 4,500W (about what that little one from the picture does). And yet, about half an hour later, the water’s cool to lukewarm at best. It just can’t keep up.
Now, I don’t know why no one’s pointed this out. I invite anyone to find flaws in my numbers. One person already explained to me how the heating elements work, but as far as I can tell that’s not relevant. No matter how you get the energy from the electrical system to the water, the amount of energy needed doesn’t change. So it doesn’t matter how it pretends to work. It just won’t.
Here’s the annoying part though: they already kind of know this. Buried in the “questions” portion of the page is this:
You have to read it from bottom to top, for some stupid reason, but what the CEO is saying is that you can only expect a 39-degree increase in temperature at 2 gpm. According to my numbers, that’s a very generous estimate already, though maybe he’s using European 220V outlets, which would be closer. The point is that he says two would be required for a comfortable shower. Not once in the main page does that get mentioned. In fact, here’s the diagram that appears first on the page.
That’s two showers and a sink running off the same unit, which EVEN ACCORDING TO THE CEO’S VERY DODGY NUMBERS is nowhere near enough. If you use his numbers for how much this thing can heat up the water, my apartment would need five units: two for the shower and one for each sink. If you use my numbers — which, you’ll notice, I actually showed my work on — you’ll need six for each shower and three for each sink, for a total of 24 units. At $300 apiece, that’s $7200, plus the power bills for all of them. And a normal standing hot water heater costs about $450.
I’m sorry if you spent money on this, but I just don’t see any way it’ll work.