Advice for adding AC to existing DC solar setup

DIY
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I already have DC in my van with 300W up top and around 900W ground mounted outside which can be connected and disconnected via and Anderson connector. I added the ground mounts for winter however they are not needed now we are entering spring for my daily electricity needs and the 300W is pretty much adequate and certainly will be in the next weeks and beyond until autumn again.

So, rather than have them sit unused, I am now thinking how I could utilise the ground mounted array on my land. I have few desires but a couple I have thought of are water distiller and induction cooking. These would allow use of the large surplus but as such, being a large amount of power I want to use up it seems like it might be time to think about adding AC since higher powered appliances will mostly be AC.

Now I would prefer to make this outdoor setup separate from the van rather than run things in and back out again as it is more convenient not to have to go under the van all the time to connect and disconnect now it is not essential for my basic power requirements in the van. I am still ignorant really of how AC is setup with solar except a vague idea you use an inverter. This is because before I had no desire for higher powered stuff and so just ignored information related to AC.

Also I was afraid of the higher risk with AC. So as such what extra safety precautions must be taken when dealing with it? How much more dangerous is it than a simple 12V setup?

The outdoor array is of voltage of around 73V open circuit.

What I am still unclear of is what extra equipment would be required given the above intended goal of a separate system. WOuld I have to get another MPPT as well as the inverter? If so what voltage should it be if I do not need it to be a specific DC voltage for anyhitng else and just want to convert it to AC? Is it better to get a higher voltage such as 48V in this case? I am still not clear why there are not products that convert straight from ‘raw’ solar DC straight to AC via an inverter? Why is that?

I was also advised I need a battery as well but so long as I only want to use the outdoor stuff in the day I shouldn’t need one should I? Due to it being only during these peak summer months I don’t want to spend too too much on this. So suggestions to keep costs down would be welcome. With that in mind could I also save some bucks by getting a pwm instead of an mppt? I know it is less efficient but it doesn’t need to be super efficient due to the higher output during these seasons if it would still work.

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12VDC is quite safe, sure the energy realeased in a short circuit can be the same as with 120V or 230V AC, but at least 12VDC is safe to touch.

Theres loads of different electrical codes around the world, so for detailed answers you would best contact a local electrician. Even for an offgrid system. Depending on where you live you might be allowed to install the AC system yourself, or not.

Depends on where the MPPT of the ground mount system is installed. If its on the panels/on the system, then you dont need another MPPT. If its mounted inside the van, then i guess using it would mean routing things through the van, which you want to avoid.

You may need to change settings like charge voltages depending on whether the MPPT is connected to the van in the winter or the AC system in the summer.

Every victron system needs a battery. Im sure theres offgrid inverters out there that do work without batteries, but at least on the victron side you do need a battery.

I guess, but im not sure. I havent touched a PWM charger in years i think, i dont even know if you can adjust charge parameters on them. I guess, thats the very basic of function.

I think the main issue is here. Heating water takes a lot of energy. A 900Wp system can roughly generate 3.2kWh per day during summer. A 3kW appliance needs to run for an hour to use 3kWh. Now you might say, but boiling water for an hour is more than i need.

The issue is, those 3.2kWh you get per day, dont get produced all in one hour. At max you will get 0.9kWh in an hour because thats what your panels can produce. So unless you want to boil water at only 900W, and only if those 900W are actually being produced, you will need some battery in order to use it through an inverter.

Now of course you can also use the DC power directly, without a battery or an inverter. A heating element is just a wire resistor, that also happily takes DC. Theres heater controls available to retrofit existing tank water heaters to directly take DC in order to heat the water, to avoid rules and regulations that come with connecting your PV panels to the public grid. Sadly this only works with resistive loads, your induction plate very likely will not take DC, it might just refuse to work or release the magic smoke.

Theres for example this DC tank heater control

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Thanks for the comments. Hmm in this case then it makes it seem not worth the added risk since I don’t really care about AC appliances and overall happy with DC. Looking from another perspective can you recommend DC devices which I could use in the current 12V system which would take more energy to use up my surplus from a perspective of off-grid living stuff which would be useful for that.

If I don’t think of anything else to use it up I might just leave them out in the sun disconnected. I read some say this is bad for them as it increases heat but I read a good point online when researching that when your battery hits full then this is just the same as them being disconnected anyway since the MPPT shuts down. I notice that they will give full charge to the battery within only a couple of hours when connected anyway, now it is out of winter and so they are pretty much in a disconnected state most of the day anyway unless it is very cloudy and/or rainy or such bad weather.