Air quality has become a hot topic in recent years. [Ryan Stout] was interested in improving it in his camper van, and set about doing something about it. His solution was an automated system that provided cleaner air and better comfort to boot.
The concept was simple. [Ryan]’s system is based on an Arduino clone, and uses a SparkFun SCD40 as a CO2 sensor, and an MCP9808 for temperature. When the system detects excess carbon dioxide levels, it opens the MaxxAir fan in the camper by triggering it with an infrared signal. Similarly, when it detects excessively low temperatures inside the van, it kicks on a diesel furnace for heating. In a neat addition, to avoid the fan sucking in exhaust fumes, it also closes the fan in order to avoid exhaust fumes entering the camper unnecessarily. All the hardware was then wrapped up in a simple 3D printed enclosure.
With this setup, [Ryan] has managed to cut the buildup of CO2 in his camper at night, and he credits this with reducing morning headaches when he’s out in the camper. We’d call that a win, to say nothing of the additional comfort created by the automatically-controlled heater! If you’re interested in something similar for your home HVAC system, we’ve got you covered.
I have similar setup with esphome scd40 and another esphome fan. Logic is controlled by HA.
I wouldn’t use ESP32+bloatware for critical app like this.
Ryan really should get rid of that diesel heater. There’s so many more safe and healthy alternatives for heating. Particularly if sleeping in a camper van, the focus should be on personal heating rather than space heating. A foldable electric panel heater would be a good start (needs a battery to power it 6~8 hours). But for super low-tech, perhaps filling a hot water bag with some hot water would be best. It’s a great analog solution: super cheap, safe, efficient, and can be placed inside a sleeping bag or under the sheets and keep the entire space warm the entire night.
I’m going to disagree. An electric blanket and thick quilts are nice but, campers need to move and are constrained by weight. With this metric in mind, liquid fuel heaters are way more efficient than electric heat. They also have the added benefit of driving off moisture build up and being able to keep the space comfortable during the day. The space heater should pull exterior air in for combustion and then exhaust that to the outside. The combustion gasses shouldn’t mix with the interior air supply. I would advocate for insulating the camper to reduce fuel use. In my build I have a Webasto that burns gasoline which the vehicle also runs on. It sips electricity reducing the quantity of batteries which also saves weight. Using the same fuel also means that there is one less resource to keep track of when camping.
I would consider the co2 monitoring mandatory in any habitating space. Humans put out a fair amount of the stuff so linking it to some automatic ventilation is a neat idea.
The actual weight required by a liquid fuel heater is usually more I’d suggest than the electric heater – the electric heater can be basically nothing but the actual heat generation component. So while the energy density of the fossil fuel vs battery might make the total system weight higher that is very much going to be particular use case specific – in effect how many if any battery are you carrying?
If you have access to grid power all of the time you are in the space you don’t really need battery at all so electric is basically unbeatable on the weight front, may well be cheaper (for some nations) to heat the space, and even more efficient overall (mains generation and transmission is quite efficient, where your small burner probably isn’t combusting the fuel fully).
However if you need many many days of off grid heating, especially in a colder climate or without enough insulation it is going to be hard to beat fossil fuel as the primary energy sources, the energy density is just so good compared to battery. Though even in that case you may still be better off electric in the living space and relying on an external power generator, perhaps the a tow vehicle etc – that just lets you put the exhaust a safer distance away from you.
But as always neither option is perfect for all, and to some extent there is no such thing as a bad choice either – make the decision based on what seems best to you for how you expect to use the system, and then find you end up using it very differently and actually some other option might have been better. So you live with it.
Running a generator for an electric hetaer wastes 2/3 of the fuels energy. You question the efficiency of a small liquid fueled burner for heat genertation and advocate for the use of an inefficient small engine in a generator? That is really wierd.
I thought it was clear that is for an entirely different reasoning – exhaust isn’t good to breath, so keep it further away from where you are expecting to be. Yes the efficiency of the generator to make electric to then get heat isn’t going to be great, but safer. Also if its powered by your tow vehicle it may actually be reasonably efficient – too many variables there to say categorically but car/van engine tend to be better than small generator I’d suggest.
The Efficiency comparison was intended to be local burn direct for heat vs grid supplied electric, where a small relatively inefficient burner, which seems to be pretty common at the camper van and small boat scale may potentially be beaten by the good efficiency of grid generation and transmission. Again many variable, but grids in developed nations tend to be pretty good, and small burning stuff heaters don’t tend to be good at all.
My mains power is cheap, but it’s not efficient – it’s primarily from an old coal plant. It’d only be more efficient if comparing conventional natural gas to a heat pump or a grid with quite a bit of other power. If using electricity lets someone reduce the needed heating by using electric blankets, radiant heat, etc that would also help. But it definitely takes more fuel to run a resistive heater off of a generator or a power plant than it does to make the same heat the normal way. Gas water heaters are typically close to full efficiency, for example. It’s just sometimes more awkward to route the intake and exhaust without undoing some of the benefits – we all recognize it’s counterproductive if you can’t burn fuel in a heater without having to let a lot of icy cold air in to keep the fumes/exhaust levels down.
Very true, it is a pile of design choices to be made with far to many variables for any one solution to ever be optimal. For you if your mains power is cheap and that is your primary goal electric might win, even if its not efficiently generated.
For instance my sister happens to be a tree surgeon, so has access to lots and lots of tree trimmings – so obviously for her wood fire just makes sense, it is effectively negative cost fuel as you don’t have to put any time or effort into other disposal methods. But for most probably a terrible choice, as wood isn’t an easily transportable or energy dense fuel in comparison to the common fossil fuels, and being wood the burn is never going to be as clean as camping gas canister options etc – so you really need some rather good ventilation and good access to open air at the flue so the smoke will dissipate.
Yeah, there’s cases where efficiency isn’t a concern where the fuel can be significantly worse. I just guessed that all the efficiency-minded options would be clustered near the limits of their underlying methods, so that there’s not that many distinct groups of choices.
In which case, my picture of the typical tradeoffs is that there’s a small amount of direct inefficiency from the top fuel-burning heaters and negligible amount from an electric one. Then there’s a medium amount of inefficiency from whatever amount of cold air has to enter to let the heater run, unless there’s a very good heat exchanger minimizing that. Usually you just feed outside air to the heater and return exhaust to the outside, as far as I’m aware. Finally there’s a large inefficiency in the power plants on the grid, which depends on the mix in your location and is hopefully going to improve over time. I think this last one should dwarf the losses of the others, but I admit in some places there might be some pretty clean power and some pretty crappy fuel-burners. Hydropower vs a wood stove or an ancient furnace may go badly.
Your 100 percent correct about the use case being the primary factor in deciding how to heat. If you can plug in then carrying any sort of fuel weighs more. Through my bias of preferring to be off grid I structured my argument around being disconnected.
I would push back against the generator for powering an electric heater. Fuel -> heat-> motion ->electricity ->heat has lots of run for loss. Why not take the heat and use it as is? While the Webasto is louder than an electric heater, it is WAY quieter than any generator I’ve seen.
There are serious issues with using a car engine as a primary energy generation source. It shares the same flaw as a generator but additionally has been optimized to move the vehicle and not make electricity. Idling a car for long periods is bad for it (I saw online a car that had its muffler blow up because of ice build up after being left idling over the weekend in an airport!). Regardless of potential damage, the small heaters can go for a day on a gallon of fuel. Can you idle a car on the same? One benefit of using an engine is that it probably already is piped into the cab for heat. While its a terrible idea to try and heat a car that way for camping, it’s probably better than trying to run a space heater off a small alternator.
To further prove (but mostly because its fun) the liquid fuel vs battery storage in an offgrid setting I submit this tangent:
The webasto (running on gasoline) that I mentioned consumes around 1 gallon of gasoline in a 24 hour period. (~3USD/gallon, ~6lbs) This potentially equates to 125,000 btus of heating. The equivalent BTU in watt/hours (electric storage) is 36,600k watt/hour. This would take 15x 100amp hour 24v lithium batteries to store. Those batteries (from amazon) would cost around 8,000USD and weigh 690 pounds.
If you are going to use electricity to heat, then small amounts of directed heat is the way to go. I.e. electric blanket, heated floor, ect.
Lots of the tow vehicles I’ve seen of late have been hybrid of the electric drivetrain style (at least I think they were – not always easy to tell). But in that case the ICE element is all about being as efficient at fuel-electric conversion so ideal for this use, still going to struggle to match directly using the burning heat as heat. But efficient enough probably to be worth considering when you factor in the other potential benefits.
>Why not take the heat and use it as is?
That would be great, but to me the main consideration there isn’t about maximising the efficiency, but the safety of burning stuff really near you and potentially many others all staying in a confined space. If you engineer and use the system right it can absolutely be done, but that is an if.
>This potentially equates to 125,000 btus of heating.
One question there is that actual heating off the device into the space or the entire potential of the fuel much of which will go out the exhaust? Seems a touch high for heat into the space and a touch low for the fuels potential (though I don’t really do imperial measures much and the potency of your fuel blend is lower than Europe/UK too isn’t it?). Either way I do agree if off grid is the goal burning stuff is likely the winner, though with how cheap and performant solar is getting at least for some climates you would probably be able to avoid burning stuff at all.
I do have a heater that can use diesel, but it’s a purely passive one with a cotton wick and it’s only meant to be used if there’s a power outage during a hard freeze and I need to keep the wellhouse warm. The cheap diesel heaters of a similar design seem questionable – they’re *supposed* to keep fumes out, but they don’t have a great reputation. By comparison, propane is good enough for energy density, and it’s more multipurpose than diesel or gasoline. I haven’t checked if there’s any heaters using it the same way as those others, but there’s a lot of propane gadgets so I’d expect one.
Before good LEDs and batteries, as well as common solar panels and efficient small inverter generators, propane lanterns were even an ideal light source when not on the grid. But even now that it’s not needed for that purpose, it’s still used in RV’s and when camping for cooking, heating, cooling/refrigeration (absorbtion type), and in electric generators of course. RV parks and campsites are often equipped to refill tanks, and various other places sell it, although the quantity and pricing isn’t as good as gasoline or diesel that way.
And where to get the hot water? A proper installed and maintained diesel heater is a reliable heater and gives much more comfort than such improvised low performance solutions. Why use a low tech solution, when I have a decent one? Leaking water bags are also not really helpful.
From the same heat source used for heating/cooking food. It’s as easy to say that a proper water bag will never leak.
Diesel heaters are extremely safe and have been used for years in campers and trucks.
The tailpipe levels of carbon monoxide are vanishingly small and shouldn’t find their way into the inner space anyway.
I think he should worry about CO and not CO2.
You clearly know very little about camping in a van. There is little difference between space heating and personal heating when the space you’re talking about is under 100sq ft. Electric heat is great when you are connected to the grid, but the entire point of most vans is that you are not. Diesel heaters are popular because they are the cheapest, safest, and easiest way to generate heat in a mobile vehicle.
If there was a better solution, more people would be using it.
“If there was a better solution, more people would be using it.”
The diesel heaters may or may not be perfectly good, but I think we should know by now that when there is a better solution to anything at all, the last thing most people are going to do is change their minds just because they received new information.
Like that the project achieved a level of finish that mine usually stop at.
And now please get rid of the breadboard. The system is failing by only looking at it.
Granted its a hobby project, so maybe they just wanted to write one more driver, but the SCD40 provides temperature and humidity alongside CO2 concentration, since you need that information to complete the CO2 concentration calculation.
Indeed, the sparkfun library explicitly outputs that data with a dedicated method, which is in the first example file in the library.
Also, while it is true that the MCP9808 boasts vastly superior temperature precision (0.25C), its for a thermostat in a van that probably sees 5C variation within the cabin at any given setpoint, when all the window covers are installed, the van is in the shade, and the engine is cool.
The author has some low-level MCU experience, so this system design decision makes even less sense to me.
I wish they’d spent more time explaining their part decisions beyond “I got it from sparkfun”.