My off grid solar system here in Hawaii powers our all electric home wonderfully.
Now my wife wants to get a 240v electric dryer. This is going to use more power than the current system can handle. Do I need to add more solar panels or do I need to add more batteries to my system to accomidate the dryer? Right now I have 8 panels and 8 big, heavy , deep cycle battrries.
Probably both. But the first question is, do you have a 240v system now? If not, you’re going to have to reconfigure and make some wiring changes.
All the batteries do is provide power during the times where no source power is coming in, like at night, or to provide an extra boost when needed. If your panels provide enough juice to run the dryer during daylight hours, and your dryer use is brief and intermittent, you might be able to get by with minimal system changes.
Talk to the supplier who installed your original system.
It depends on your average load v.s your average solar resource.
If you have enough panels to generate the total amount of energy you need on an on-going basis (including the new load), but you are wasting it because you don’t have enough storage, than increasing your battery capacity will be enough. You may need a bigger inverter, though.
So you need to calculate your weekly KWh consumption vs. your KWh generation, to see if you need to add panels and/or batteries. Note that a dryer is likely to use on the order of 10 KWh per week (or more), which is more than a 1KW system can generate in a day.
Running a dryer from solar panels is unusual, though - most people opt for a clothesline or propane.
Dryers need a lot of current, can you get that much directly from a reasonable number of panels? Will you be able to run anything else when that dryer is running?
Can you get propane? I think gas dryers are more energy efficient, but propane can be expensive, and your solar power is free (after the initial investment).
Dryers usually have a cool dry setting that only turns the drum and a fan, clearly it would take longer to dry clothes, but use much less energy altogether.
Does a clothes line count as a solar power?
Seriously, why would you need a dryer in Hawaii? I realise there’s a season that’s rainy and terribly damp when things don’t dry well, of course. But if you just point a fan at them, they dry just fine. And a fan uses way less electric power than a dryer!
I vote indoor clothesline with large fan!
We have a gas dryer, which works great. if that’s an option for you, probably a better one.
Just use it in the day time, then you will just need additional solar panels.
If you want to use it at night, then batteries are needed to store all that energy.
Also you have the option of turning other stuff off when the dryer is running. This is the problem electric companies have. Everybody uses a LOT of electricity at certain times. Then they spend a fortune installing power generation facilities which only run a few hours each day. They try to get their customers to move some of the electric load to middle of the night (off peak).
This is not an accurate answer.
The correct answer can only be determined by calculating the average load vs the average energy generated. Only then can it be determined whether you need to add panels, batteries, upgraded inverter or some combination.
There are a lot of economic options to consider and solar may not be the cheapest option. First thing to consider before the dryer is the washer, you want one that does the best drying (spinning the clothes), so when you move them into the dryer they have more water already removed. This should lower your overall demand for power and allow you to downsize the system.
Chances are you will need both panels and batteries, perhaps even a significant upgrade of the entire system - maybe doubling the current capacity or more - depending on what you do have. But from how you state it it appears that you may need more batteries and or inverter capacity to deliver the power on demand (and upgrading the cabling system). After being able to supply the amount of power required you have to make sure you have enough reserve capacity in the batteries (perhaps supplemented by solar) to run the dryer for the full cycle. After all that you have to have the solar capacity to replace what you have used for drying, which you may need more panels.
There are games you can play to try to stretch what you have and ‘make it work’, but that is one of the most energy intensive appliances you can get, potentially leaving your batteries pretty discharged for long periods of time, which tend to shorten their life (assuming lead-acid).
As stated a propane drying would be much easier, perhaps cheaper including the gas you would need to buy. Or perhaps a backup generator which could kick in the augment the high demand of the dryer and also recharge the batteries at the same time (which can extend the life of the batteries).
The average clothesdryer uses 2.8 kWli. Let’s round that up to 3 kW to be safe.[/li]
An 8-panel system is probably 1.5kW to 2.5kW (but feel free to provide the actual specs) and Hawaii probably gets around 6 peak sun-hours a dayli, so let’s say 2 kW array * 6 peak sun hours = 12 kWh/day best-case scenario, probably more like 8-10 on an average day. That means the clothesdryer alone would use 25% to 40% of your average daily output, more if you use it for more than 1 hour.[/li]
So you’re using more than the panels can put out by themselves even at full sun, which means you’ll need to use part of your stored battery energy.
Assuming lead-acid batteries, you’d ideally want not much more than 50% depth-of-discharge, meaning you’ll want at least a 6 kWh battery bank for the dryer by itself, not including other loads, and only if you get a full day’s worth of sun the next day. How big is your bank? 8 of what kind of batteries? You gotta do the math. It’s probably dangerously close right now.
TLDR: Listen to the other advice in this thread. Either add several more panels and/or batteries depending your system specifics and budget, or use a fan or clothesline, or power the dryer on fossil fuels. Electric dryers are huge energy users and solar panels are slow, sustained power generators, not good for sudden peak loads – that’s what the batteries are for, but you need a big enough battery bank to absorb the shock or you’ll kill the batteries prematurely. The most practical is probably a fast-spinning clothes washer coupled with a clothesline, maybe a box fan if you need it.
