Heating and Cooling Options

A project log for DIY Truck Camper

Open source truck bed camper for the masses.

DustinDustin 12/06/2021 at 04:180 Comments

Climate control is one aspect of this project that has proven very difficult to finalize designs for. There are two extremes, and countless options in between. The first extreme is doing nothing. No active heating or cooling. The second extreme is to add all the usual energy hungry appliances and rely on them year round. Having lived with both, I prefer to have full climate control. That being said, I understand exactly how much energy that requires, even for a small space. Having built an off grid camper already, and designed the solar system, I know what it took to hear and cool that thing. The energy requirements were immense. In Ohio we have extreme weather. Winters can be well below zero for days or weeks on end, with power outages lasting as long. Summers are quite hot, but the humidity makes it dangerous when your body just can't cool down. 

Im currently living in a truck bed camper to prepare for this camper build. I've had air conditioning the entire time, and it's the only reason I could be in here when it was hot. It's dangerously hot without it. This camper was built without AC, but it's still dangerously hot without it these days. I have a propane furnace, but don't use it because it needs a thorough cleaning and is expensive to run. It also outs so much moisture into the camper that it runs the risk of rotting from the inside. Still, it's nearly 50 years old and going strong. I just wouldn't want to be without a power hookup in this thing. 

Dealing with cold weather is easier for me than hot and humid. Heating is going to be a combination of electric space heaters for on grid backup heat, a small wood burning stove for off grid heating, and a diesel heater as the primary. As much as I hate burning fossil fuels, I do know that a diesel heater is quite efficient and effective. They're also cheap at under $200 USD for an 8Kw(kilowatt) portable model with 4 outlets and 12 volt DC input. It can be run in or off a vehicle and moved as needed. It has a thermostat and is fully automatic. In comparison, electric heat is expensive, and puts a massive load on the electrical system. I can't cook and heat at the same time, even with my induction cooktop and cast iron. The maximum energy I can get from electric heat on a standard household 120 volt outlet is 1.5Kw. it barely keeps up with temps above freezing. Compared to the 8Kw of the diesel heater, it's quite anemic. Diesel has the advantage of being able to run extended periods of time on battery power. Even if all power goes out, I could take the starting battery from my truck and run the heat to get me through for a while. 

My favorite heating option is wood. I love a wood fire and the nice dry heat. I've heated a very large home with wood and it's just the most comfortable and comforting. For this reason I will be sign for a wood stove in my camper. When all other systems fail, a wood stove is still an option. The problem I have with this is that the fuel takes up a significant amount of space and can be hard to find out in the desert where I plan to go soon. I'm considering looking for wooded land near the mountains, which would solve my wood problem. I'll carry a small stash of emergency wood with me as I travel. 

I want to mention heating from battery power. Unless you have a collosal lithium solar battery, it isn't viable, even in the sunniest of locations with massive solar panels. If money,weight, and space are not limited, it can work very well. I created a 12 volt DC furnace on the off grid camper build. It was a metal pipe housing two 300 watt solar dump load air heaters. They could heat that camper, on slightly chilly evenings, but drew so much power as to be a burden. The battery bank in that camper was 300 amp hours, or about 3,240 watt hours of usable capacity, if memory serves me right. Let's call it 3,000 watt hours. That means it could supply 300 watts, for 10 hours on a full charge. That's plenty to run half of the heater through the night. The full 600 watts would deplete the entire bank in 5 hours. Less with the blower fan running. 600 watts is not enough to heat that tiny camper in winter conditions. It wouldn't be comfortable, and you'd wake up with no power left at all. The solar bank couldn't run the furnace either. That solar system cost nearly $10,000 after everything was said and done. $3,000 in batteries alone. It was not cheap. There want enough roof space to out enough solar panels to charge a battery bank large enough to heat the camper. There wasn't enough room for batteries either. As much as I would have loved to heat it with solar, it was too much.

There is a way around this that's cheap and easy, but it has other drawbacks. Thermal mass. If I could use the sub to directly heat enough thermal mass, that heat could be pumped directly back into the camper at night. Something like a large tank of water would have been perfect. Considering this camper was being pulled by a Tesla and weight was a serious limitation, this wasn't an option. I did install a 6 gallon solar water heater though, but that drew 600 watts and became a problem early on. My truck could handle extra weight for batteries and thermal mass, but then fuel gets expensive and the extra load in the truck racks up repair and maintenance costs. 

So, for heating I'll be going with wood, diesel, and electric. 

As for cooling, I'll either install a mini split unit or a heat pump if I can find something suitable. I'm planning to design the camper to stay as cool as possible without active cooling, but there will be times when it won't be enough. This will be a full time home for me, so I need to make sure I can actually stand to love there. Things like skirting, putting an awning over the entire camper, parking in shade, and insulating the camper proper will help dramatically. If needed, I can always run the trucks engine to generate power for the cooling. I can also carry a small generator. I'll likely do this as they can be converted to propane, which means they can be run on biogas,which is a sustainable resource. The truck engine itself can be converted to biogas or wood gas, which are long term goals. When I have land of my own, I will build up a large biodigestor and biogas reserves to fuel lights, heat, vehicles, and electrical generators. This camper and truck are a small test platform for a much larger project. 

Anyway, I think I've covered everything. Electric, diesel, and wood for heat. Electric AC or heat pump for cooling, run either off grid power, truck engine, or generator u til something more sustainable be be acquired. I'm gaining very valuable experience in this current camper and gathering the tools and materials for this project. I should soon have a garage to work from if all goes well. More updates to come soon.