How To Heat A Greenhouse With Solar Panels

A greenhouse can be a great environment for plants to grow in, where you have full control over the growing conditions and hence can grow plants and vegetables throughout the year. In the winter months, when the temperatures dip to very low levels, heating the greenhouse to maintain ideal growing conditions becomes imperative.

One effective way of heating the greenhouse during colder temperatures is by using a solar heating system. Depending upon the temperature within the greenhouse and its size, solar heating can be very efficient. In places where the temperatures can drop to sub-zero levels during the winters, you need to combine solar heating with other heating methods.

Types of Solar Heating Systems

Now there are two types of solar heating systems: Active and passive solar heating systems.

Active solar systems consist of PV solar panels to capture solar radiation and convert it into electricity to run fans, blowers, and pumps to generate and distribute heat throughout the greenhouse.

Can a Greenhouse be Heated with Solar Panels?

When talking about heating a typical mini or hobby greenhouse, PV solar panels will mostly be used to charge batteries that will power a space heater at night. At day time, you don’t really need a space heater especially if the greenhouse is built facing the sun. If that is not the case, you can use the solar energy from the panels to power fans to circulate warm air from outside into the greenhouse.

So in theory, yes, you can say it is possible to heat your greenhouse with solar panels. You require PV solar panels, a set of batteries, a solar charger, an inverter, and a heater. There is a whole process involved like any other solar power application.

But is it practical? That is an important question that depends on certain factors like the size of your greenhouse, the heat requirement based on the ambient temperature, the rating of the panels and the batteries, and the consequent cost involved.

Below, I have explored the practicality of heating a greenhouse with solar panels with the help of an example.

Is it Practical to Use PV Solar Panels for Heating?

If you’re a bit into solar power and calculations, I’ll just show you whether it is practical to heat a greenhouse with solar panels. if you’re not much into it, you can just skip this section and keep reading below.

1. Let us suppose you have a greenhouse attached to your house outside, roughly around 150 sq ft.
2. In winter months, when nighttime temperatures drop to sub-zero levels, you will need a heater of at least 1000 Watts to keep the temperature at a thermostat level of 60 F which is suitable for growing most plants that require mild weather conditions.
3. Let us suppose you receive good heat from the sun for roughly 4 hours in the day.
4. So to charge the batteries of rating 12V 400 AH, you have 4 hours. So the current flowing through the battery to run the 1000W heater will be 1000/12 ~ 83A.
5. As the battery rating is 400 AH, at 83 A, it will run the heater for ~5 hours.
6. To keep the heater running for an optimum duration of 14 hours, you’ll require at least 3 sets of 12V 400 AH batteries.
7. To charge a single battery of 400 AH for 4 hours, the current required will be 400/4 = 100A.
8. So to charge one battery of 400 AH, the panel rating needed is 100*12 = 1200 Watts. For 3 batteries, you’ll require 3600 Watts rating PV solar panels.
9. Considering a 200W 12V solar panel, the total number of panels required will be 18. Let’s assume one 200W 12V panel costs around $500, the total cost of the panels will be $9000.
10. Coming to the cost of batteries, one 100 AH deep cycle battery costs around $200. So 12 batteries will cost $2400.
11. Add to it the cost of the heater and the thermostat, the total apparatus will roughly cost you around $12000 as per conservative estimates, without considering energy losses during conversion from solar to electric and electric to heat energy; which are significant.
12. Even if you want to heat the greenhouse at daytime when you won’t be needing the batteries, the panel rating required would be too much to justify it.

Even if the solar panels last for say 20 years, along with the replacement cost of the batteries, this whole method is very costly as we have seen. Whether you’re into this for hobby purposes or commercial production, the initial cost for setting up an active solar heating system can be steep.

For a much lesser price, you can run an electrical heater directly powered by electricity. Or if you are into saving electricity, you can opt for natural gas heaters, like paraffin or kerosene heaters which are quite safe or even propane heaters.

If you do want to make use of solar power and panels for heating, another option is to use solar-heated water or hydroponic heating. The costs will be much less and the heating efficiency will be greater.

So as far as practicality is concerned, heating your greenhouse with solar panels is not a good idea. The high cost of running it will take away all the fun in using the greenhouse.

Heating a Greenhouse with Solar Panels

In some cases, the cost of using this system will go down and if you are very keen to use this setup for heating, you can still use it. The cost will get reduced in the following 3 scenarios:

1. You live in a place where night temperatures do not drop much. You can use a heater of a lesser rating.
2. You want to use the heater for a shorter duration in the night.
3. You are using a smaller-sized mini greenhouse.

Despite the high cost of the solar panel heating system, there are a few pros as well.

• It is considered environmentally friendly, as it does not emit any harmful gases.
• Extremely reliable, so much so that you will probably never experience downtime, because the sun rises every morning, so solar energy will be stored daily.

Different Types of Solar Panels

In order to heat a greenhouse with solar panels effectively, you need to buy the right ones. When in the market for the best solar panels for greenhouses, you will come across two common types – monocrystalline and polycrystalline solar panels, each that offers their own set of advantages and disadvantages.

First things first – both types of panels serve the same function in your overall greenhouse solar heating system, where they capture heat from the sun and then transform it into electricity. Further, both types are made from silicon – a material that is the preferred choice for solar panel construction.

Even though both can be great choices for your greenhouse, there are a few key characteristics that set them apart from each other. One of the notable differences between the two is the type of technology used, while polycrystalline solar panels consist of solar cells that are made from myriad silicon fragments melted together, monocrystalline solar panels consist of solar cells that are made from a single crystal of silicon.

Polycrystalline solar cells are generally less expensive than their monocrystalline counterparts, but on the flipside offer lower efficiencies. And because they consist of several fragments of silicon put together, they are often dubbed “multi-crystalline”.

So, which of the two types of solar panels can heat a greenhouse effectively?

Well, while both types provide a great service life of 20+ years, monocrystalline solar panels are more efficient and a bit more expensive than polycrystalline solar panels. An example of an energy-efficient Monocrystalline PV solar panel kit is the Renogy 200W 12V solar panel kit with the Wanderer Charge Controller. Even if you do not use solar panels for heating your greenhouse, this solar kit can be handy in other cost-saving measures like powering a cooling fan, lights, or heating water for the plants and soil.

Monocrystalline panels feature a black hue, whereas polycrystalline solar cells showcase a blueish hue. But regardless of which one you choose, they don’t affect the performance of each type of solar panel. And since home greenhouses aren’t usually built on a large scale, and most have space restraints, monocrystalline solar panels can help you maximize your electricity production since they are more efficient.

The Setup of a Solar Panel Heating System

For setting up a PV solar panel heating system, you’ll need solar panel kits, which include wires, solar panels, and solar chargers. Then you’ll need deep cycle batteries, a DC to AC inverter, a thermostat, and the space heater.

Through the heat received from the sun, the solar panels charge the DC batteries. These batteries, in turn, are connected to a DC to AC inverter as the heater runs on AC voltage. The batteries are thus used to power the heater.

Tips on Effectively Heating Greenhouse with Solar Panels

The installation of solar panels in your greenhouse plays a crucial role in their effectiveness and efficiency. The perfect orientation of the solar panel is when it is set perpendicular to the sun’s rays. With regards to the optimal tilt angle, it should be at an angle that is equal to the latitude of the location. Also, the face of the panels should face the true south if you’re in the northern hemisphere.

Adding to this, be sure to install the solar panels in an area that is not shaded between 9 am to around 3 pm in the afternoon, because any level will significantly affect the performance of the solar panel. The best way to maximize efficiency is with direct sun exposure. Another great tip to heat a greenhouse with solar panels effectively is to make sure you insulate it well to reduce heat loss and ensure efficient heat transfer.

Final Thoughts

As we have seen, heating your greenhouse with the help of solar panels and a heater can prove to be a costly affair. Instead of that, there are different hybrid methods of heating such as passive solar heating systems involving a heat exchanger, thermal mass, and solar-heated hot water which are much more energy-efficient and affordable.

Have you thought of using solar panels for heating your greenhouse? What method are you using currently for heating your greenhouse?

Do let us know in the comments!