I have an environmental monitoring system set up in a rain forest and the whole system only requires <400W power consumption. Our field station is quite far from the site, so we are trying to buy a generator with longer run time (>12 hours). I am thinking of connecting two Ryobi 2,200W generator using a inverter generator parallel kit. According to the website, “8.75 hours run time at 400 watts and 5 hours at 900 watts”. I wonder if this way can make it last longer, maybe >14 hours? Thanks very much!
Most generators aren’t designed to be connected to other generators. You have to be very careful connecting generators together. They have to match in voltage and frequency, and they have to be exactly in phase when you throw the switch to connect them. Even then, they won’t necessarily share the load evenly. In fact, it’s fairly easy to end up with one generator running slightly ahead of the other, and having it power not only the load but also power the second generator, which then becomes a motor.
There are some generators that are designed to be connected together, and they usually have a cable of some sort that connects between the two so that you can connect them without frying anything and so that they’ll also share the load once they are connected. I googled some Ryobi generators (since that seemed to be the one you were interested in) and some of them do have load sharing capability. It requires you to purchase a separate kit for it though. You seem to be aware of this kit, so this is mostly a discussion for others coming into this thread.
In an ideal world where the generators perfectly convert fuel into power, doubling the generators and having them share the load should double your time. In the real world, mechanical inefficiencies are going to shorten the time you’ll get. You might make it to 14 hours, but then you might not. Without actually seeing specs and doing any testing and basically just pulling a number out of my backside, I’m figuring you’d end up with somewhere in the range of 12 to 15 hours.
The running time of your typical diesel or gasoline powered generator is based on the size of its fuel tank. Rather than mess around trying to get two generators to share the load and run longer, I would instead focus on adding a bigger external fuel tank to it. That will be a lot cheaper and a lot easier, and more fuel efficient overall. Doubling the fuel tank of your 8.75 hour generator will double its running time to 17.5 hours.
Just out of curiosity, would it be more or less efficient to get a large battery and hook the generator up in a hybrid like fashion so it kicks in when the batteries are low to replenish them? Kind of like one of them new fangled hybrid cars?
This makes an incredible amount of sense. Two generators may allow one to take over the full load in case of a failure in the other, but then you’d need bigger fuel tanks in both anyway to insure you stay running for the full time.
If there’s a nearby stream, would microhydro and a battery bank be a practical supplement/alternative?
Solar might also be a viable option, depending on the location of the site (not all rain forests are tropical) and the season. And either hydro or solar would reduce the amount of stuff you have to schlepp out to the remote site (since you wouldn’t need to fuel them).
As said above a larger fuel tank is what you need for longer run time, but there does seem to be some options.
400 W seems like a large requirement for a environmental monitoring system. The lower this power requirement can become the more able alternative energy or hybrid energy solutions may work a lot better then a generator.
You may be able to get that time you need to get to that station to refill/maintain it down to once a week or less if you can get that power requirement down significantly.
I’m no expert, but I’m pretty sure one of the distinguishing features of a rainforest is the lack of light at ground level due to tree cover.
ETA: though maybe the OP’s field station is in a clear area.
Do you need to power down a generator to refuel it? Isn’t the solution to running it longer to just add fuel every X hours?
Presumably they’re not designed to run indefinitely, but you don’t really need a bigger tank if someone’s “every 8 hours” job is to go pour more fuel into the generator.
Maintenance is going to be an issue. Most small generators call for a 100-hour oil change interval, which works out to nearly two oil changes a week if you try to run it 24/7. You might be able to stretch that to weekly changes with full synthetic oil, but I wouldn’t want to bet the success of a project on it.
400 watts seems high for a monitoring station - these things are usually engineered to run at “flypower” levels that can be handled with something like a couple of sealed lead acid, aka SLA, batteries such the ubiquitous 1280 pack that’s found in countless burglar alarms and UPS units. If you can engineer it to run on two battery packs in parallel, you can swap the packs sequentially and not lose power.
As a plus, two batteries will weigh less than gasoline, and aren’t an environmental risk. (How much paperwork will there be if you spill a couple gallons of gas or a quart of used oil in the rain forest?)
Batteries won’t weigh less than gasoline with the same energy content. There’s a reason why all-electric cars haven’t taken over the marketplace.
I don’t think the issue of the battery weighting less but the time required to continuously refill a fuel tank needed to run a generator for all power compared to the time required to maintain a solar/battery bank or a generator/battery hybrid system for a remote outpost monitoring station.
Carrying a few batteries every year or two may be easier then carrying 8 gallons of fuel 2x a day every day.
I just envisioned the Robinson Crusose solution, which would be to have a long series of bamboo pipes strung together, leading back to the base camp, and every few hours he pours a few more gallons of fuel into a big funnel…
but I agree that a bigger tank attached to the generator will probably give you the most bang for your buck.
A few batteries every year or two will not replace 8 gallons of gasoline twice a day. The only way you’d get it to run on those batteries would be by lowering the power consumption by orders of magnitude, and if you did that, that would be the real reason for your savings, not the change of power supply. Plus, I’m sure that if that much reduction in power consumption were possible, that the OP would already be doing it.
The OP also asked is 2 generators would accomplish this, with this I assume this person is perhaps more in a personnel management role (or the shlub who has to refill the tank) w/o the expertise knowledge in the scientific/power generation engineering background and thus asking for help.
The specific energy of gasoline is on the order of 10,000 watt-hours per kilogram. Lithium-ion batteries are on the order of 200 watt-hours per kilo. Powering the system with batteries would mean moving 50 times as much mass in lithium-ion batteries vs. gasoline (lead acid batteries would be another five times worse).
OK, rephrase that, then. If it were possible to run this thing on orders of magnitude less power, someone on the OP’s team would have already done it, even if that someone isn’t the OP himself.
And those batteries require a source of electrical power to recharge them.
Out of curiosity - what is it that you are doing that requires 400W ?