Saving money, saving the environment and saving time. These are the main reasons why using solar power in the garden and greenhouse is such a good idea!
We’ve all seen the large-scale solar power installations on buildings such as the new Apple Park, Tesla’s factories and even grocery stores.
And we probably know people who have solar panel installations on their roofs. And then there are the huge solar farms in deserts and other areas that generate enough electricity to power a small town.
These are a massive investment in materials and labour. But the pay-off is clean, free energy from the sun. Especially with all the concerns over the burning of fossil fuels to produce power.
So this begs the question: can small scale solar help us in our gardens and greenhouses? Of course, otherwise this article would be really short!
Let’s have a look at what is required.
Solar Power Equipment
There is an investment up front with any solar power project. While there are ways to save money, you need to realize that solar energy is not 100% free.
ROI or return on investment varies, mainly depending on how much energy you can produce, how much you can store and what you use it for.
There are really only two things you need: a way to generate power and a way to store it.
Solar panels have really come down in price. According to this article in 2009 the average cost of a solar panel installation was $8.50/watt. A little over 10 years later in 2020 the cost dropped down to $2.81/watt.
So it’s now more affordable than ever for the average consumer.
Now for your garden, you likely won’t need an extensive solar power array. And that’s where the camping niche helps.
There are now lots of portable solar panels available that are super easy to setup for RVs and people camping with tents.
These can range everything from very small 40 watt panels to larger 100 watt panels that are less portable. Here are a few options:
They all come with easy-to-connect cables, a charge controller for hooking up to a battery and some even come with convenient stands to tilt them for maximum sun exposure.
Honestly you can setup a panel in about 5 minutes and have it producing power. I’ve done so with two of my solar panels.
But there are a few things that will make your solar power system better.
Usually the power coming out of a solar panel is a low voltage, typically 12 volts. This is the same voltage that you get when you plug something into the accessory port in your car (which used to be used for a cigarette lighter).
While you can get various electrical devices that can run from this 12 volt source directly, some devices may need full line voltage, similar to what you get when you plug something into an outlet in your house. Usually this voltage is 120 volts or 240 volts.
To increase the voltage that your solar panel puts out, you’ll need an inverter. It basically boosts the voltage up to 120 or 240 volts so you can plug in regular devices.
Here is a good option that can support up to 300 watts of solar panels:
Batteries for Storing Solar Energy
So as mentioned, you can hook up these panels to a battery.
Now, you don’t need to do this as this is added expense. However depending on the application of using solar power, you may need that energy at nighttime when the sun doesn’t shine. Or maybe on super cloudy days when the solar panel won’t be producing maximum power.
There are different options for batteries, the one you want to use for storing solar power are marine deep storage lead acid batteries. Many of these are now no-spill, meaning that they use a gel instead of a liquid.
Keep in mind though that these batteries need to be in a spot that’s well ventilated. Usually that means outdoors. I do have a cover over mine but it is open at the bottom and back and is outdoors on my deck.
The other option is lithium and while this is a much more expensive option, lithium batteries last longer. They require a special charge controller so that does add additional expense as well.
Because of the battery’s weight it is best to source this locally.
Finally there is whatever you want to power, so I’ll go over those options in the next few sections.
Solar Powered Water Pumps
If you collect rainwater in barrels, you have to have the barrels elevated to allow you to empty the barrels. And you’ve noticed that it’s often hard to get those last few gallons or litres of water out of the barrel.
Plus with an in-ground cistern you won’t be able to use gravity to empty the rainwater.
So that’s where a water pump comes in. Usually these are submersible pumps that you toss into the barrel or cistern. But these run off electricity.
So you need to make sure you have a source for power.
While many of these pumps are 110 volts (or 220 in some countries), there are now also 12 volt pumps, mainly designed for use on boats.
Here is one that has highly rated:
These are perfect to run off a solar panel. Just hooking up a pump with a switch to a small solar panel gives you the convenience of not having to run power to where your barrels or cistern is.
And often you don’t need a battery hooked up to the system, as you’ll likely be watering in summer during the daytime when it’s sunny.
This is still something I need to setup. Right now all my barrels are gravity emptied but it’s not ideal.
Solar Powered Greenhouse fans
This is another way we use solar power and my favourite (so far).
Greenhouse ventilation is key and one way is to have fans on during the day to provide airflow around your plants and help cool the air, especially on very hot days.
Fans though can be expensive to run. So these make sense to run off of a solar panel as well.
And there is a cheap way to get fans. Most modern desktop computers have power supply fans that keep the power supply cool that converts line voltage from your outlet to a lower voltage used by the computer.
These fans are designed to run continually and put out quite a bit of air. I happen to get these free from my university when we dispose of old computers, but you can also buy them new online.
I’ve combined four of these into a fan array that I run off one 40 watt solar panel on my greenhouse roof. And no battery required.
If you don’t have a source for free ones, you can also get them online:
The advantage of using the solar panel without a battery is that as the sun comes up, the panel turns on the fans and as the sun goes down the fans automatically shut off. This saves me the time of having to turn the fans on and off manually.
Plus on cloudy days the fans will slow down and run at a reduced speed since they are not needed as much.
If you do for some reason want the fans to run at nighttime too, you’d have to add a battery. But then you’d also have to add a switch or thermostat so you can have the fans off when it’s not hot.
If you want to use larger fans that run off of regular line voltage, you would need to get an inverter to convert the panel’s low voltage.
Solar Powered Greenhouse lights
This is a project I hope to complete this winter to install some lights in my greenhouse so I can extend my growing season more.
Since you likely will use the lights at nighttime you’ll need to add a battery to the system.
Obviously LED lights will be the only way to go as they don’t require as much power as incandescent or fluorescent bulbs or tubes.
Ideally find 12 volt lights that you can directly connect to the battery to make things easier. Such as these ones:
And to control the lights, use either a timer to have the lights come on for a present amount of time. Or you can also use sensors that will turn on the light when it gets dark, although typically you don’t want the lights on all night – plants do need some darkness.
Now, you don’t need to constrain this to just in the greenhouse. You could also setup grow lights anywhere in your house and have a way to bring in solar power from outside.
Solar Powered Greenhouse Heating?
This one I’m still trying to figure out. I have some ideas but haven’t tried any out.
Realistically you probably can’t heat your whole greenhouse with solar electricity. After all our greenhouses are supposed to capture solar energy passively. But at night time and on cloudy days that source of heat gets turned off.
Localized heating is probably best. You could run a heat mat from solar to provide bottom heat to seedling trays. Most heat mats are line voltage, so you’d need an inverter to covert the low solar panel voltage to the higher voltage needed by the mats. I like heat mats that I can put directly into a tray and put my seed starting pots on top, like this one:
There are also heating cables you can bury under the soil in a raised bed or a hotbed. These again require line voltage.
Another option is to use another form of solar heat collection by heating water running through pipes exposed to the hot sun and store that water in an insulated container like an old hot water tank. Then circulate that water at nighttime through other pipes buried underneath the soil.
This option does though require solar power for the pumps that move the water around if you want a system that doesn’t need external inputs. So even though your greenhouse isn’t directly heated by the solar energy you’re producing from the panels, it is still an important part of the system.
Solar Powered Phone
You likely use your smart phone for taking photos of your garden, having it nearby in case someone needs to get a hold of you or maybe to research a plant or problem in your garden.
Or even to order pizza if you realize it’s dinnertime and you haven’t had time to cook anything as you’ve been in the garden all day!
So your phone needs to be recharged regularly. What if you could charge it with the sun?
There are now very small panels that are used by travellers to charge their phones. There are even flexible panels built into a backpack.
All you need to do is tilt the panel to the sun and plug a USB cable into it and your phone and have your phone charge as you work in the garden.
Or you can do as we did and run a cable through our kitchen wall so that we have the convenience of charging our devices anytime. Our panel is also hooked up to a battery so we can charge at nighttime.
I used an adapter that plugs into a vehicle accessory port, but if you want a more elegant panel version, this one would do the trick:
Expanding Your Solar Power System
Starting small is always the advice I give. Maybe you start off with running a pump for your water barrel. Or setup a fan for ventilation in your greenhouse.
But once you get hooked on the free power you get from the sun, you’ll likely want to do more!
Obviously adding more panels will allow you to capture more power and run more systems.
We did that by adding a large 100 watt panel that now charges our battery and portable devices. And that I’ll use to run lights and heating cables in the greenhouse plus water pumps for my rain barrels.
Collecting more power also means more battery storage. And if you never setup any battery storage to begin with, getting just one battery will help.
You might also want to add various sensors as well as better monitoring of how much power you’re producing and storing. I have some ideas on how to use a mini-computer like a Raspberry Pi or Arduino.
The possibilities are endless! And soon you’ll want to run your whole house on solar power!
So has this inspired you to start with solar power? Looking forward to hearing what you set up – comment below and let us know.
If you enjoyed this article, have something to add or have any questions, please leave a comment below.
Wishing you all the best!
Tranquil Urban Homestead, Victoria, BC