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Many people are using solar lights in their gardens, whether they are to provide light near the garden beds or show a lit path through the plants during twilight hours. These not only light up our backyards but also save us money from wasting electricity thanks to being solar-powered. These garden lights are usually placed in an open environment for aesthetics as well as lighting the garden for easier viewing in all conditions. However, without these being plugged into a grounded source of electricity, people are also asking: how do solar lights work in a garden?
Solar lights in a garden have solar panels on their top sides, and these panels convert the sun’s power into electrical power throughout the day. Instead of utilizing the power instantly, the solar panels will store the electricity generated from sunlight in rechargeable batteries or cells during the daytime. In the evening, energy-efficient LED(s) are turned on by the automatic sensors in these lights, and the solar-powered lights will light up the garden using the stored energy in the batteries.
Now, let’s have a look into the details of the components inside solar garden lights in the following subsections. This will help you understand more clearly how these lights work and why they are efficient, consume less energy, have a long lifespan, and are easy to install.
How Solar Garden Lights Work
Photovoltaic (PV) cells are used by solar lights to transform sunlight into electricity during the day. LEDs (light-emitting diodes) are used to produce the light in these fixtures, and they have an incredibly long lifespan and use very little electrical energy to run. Batteries are charged using the PV cell energy, and the LED lights are powered by those batteries at night. Modern solar lights are able to charge efficiently even on overcast days or in partial shade because of the advancements in photovoltaic technology.
- A tiny built-in solar PV module is present in every solar-powered light. Sunlight is absorbed by this module, which converts it into electrical power, the amount of which is determined by the intensity of the light.
- This power is then stored into a rechargeable cell or battery in the form of chemical energy that is concealed within the garden light’s casings.
- A photoresistor (sensor) makes the decision of when to turn the light on. The photoresistor prevents the light from operating during the day, but when it starts to sense little or no light, it will turn the light on. This helps avoid the unnecessary wasting of energy.
- The chemical energy of a cell or battery is converted back into electrical output, and this powers the light after the photoresistor allows the light to turn on.
Basic Components in Solar Garden Light
A solar garden light is made up of a number of components that work together to efficiently create electricity from solar irradiation, store it, and then use it to illuminate the garden. The overall components are the same in most models of solar garden lights, even though there are several changes in how the elements are set up to get the greatest results and efficiency for the area in which a light is intended for. Let’s examine the standard solar garden light system’s components in this subsection of the article.
Every solar light comes complete with mounting hardware and tilting brackets, ensuring that the solar module is strong and correctly slanted to absorb the maximum amount of solar energy. Given that the solar module will be exposed to weather changes and wind for years, it is made to be durable and strong as well as lightweight.
The size of a solar module depends on the size of the LED lights and charging batteries inside.
Solar garden lights, or garden aesthetic lights, run during the nighttime hours when sun is not present. Due to the lack of sunlight and charging power during these time frames, there must be rechargeable electrical energy storage elements (batteries or cells) within the lights that can store energy and give power back when needed.
Small solar lights used in gardens may have single or multiple rechargeable Ni-Cd or Li-ion cells in them according to their output. The backup time of the garden lights depends on the number of cells and the number of LED lights it has.
As an example, if we have a 3W garden light (LED) and 4 rechargeable cells with total capacity of 30Wh, the light will be around to run for around 10 hours. The calculations for this are shown below:
(In the case of Li-ion cells, the terminal voltages are 3.7V.)
Four cells in parallel will store energy.
Similarly, we can also calculate the approximate backup time if we have knowledge of the battery size and the garden light’s LED power.
Automatic Light Sensor
During the sunny hours of the day, we don’t want our solar garden lights to turn on as this would just be a waste of energy. There is an electronic circuit in most garden lights that automatically turn on the lights when the sun is not present but allows them to stay off when it’s time for them to charge during exposure to sunlight. This circuit consist of a light sensor and a resistive voltage divider circuit. When there is light falling on the sensor, it keeps the garden light turned off.
Light Emitting Diodes (LEDs)
For solar garden lights, we need efficient output that consumes less power so the losses are minimal. In these cases, it is best to use LED lights to brighten the garden. These run on batteries through an energy management circuit for constant voltage.
Energy Management System
As mentioned above, the power from the solar modules is not constant, and it also depends on the intensity of the sun and the irradiance level. Therefore, the power needs to be regulated for charging the batteries and running the LEDs properly.
To charge the batteries at a regulated and constant power, there is an energy management system that controls the battery-charging voltage. It is also responsible for turning the circuit off and on to avoid overcharging and over-discharging the battery to avoid any damage to the circuit and batteries.
This energy management system also monitors the output from the automatic light sensor circuit and makes decisions regarding turning the light on or off according to the settings.
Although it varies across manufacturers, some of the additional components one might find in these lights includes wrappings, fixture arms, and mounting brackets, all of which are typically included.
Pros of Using Solar Garden Lights
Using PV-based solar lights in your garden has many advantages over conventional light bulbs that run on electricity. Some of these benefits are listed below:
- They use green and clean energy to run.
- By storing energy during the day, you can light your garden on that same clean energy.
- They are more energy-efficient as they use LEDs that consume just a little bit of energy to light up the garden and have negligible power losses (as compared to conventional light bulb of same luminosity).
- They can run throughout the night by themselves and without interruption, so they can be used as security lights.
- They are very easy to install and do not require complex circuitry to set up.
- They do not need any wiring or cable laying as they have all of the necessary power sources and storage inside of the casings.
- LED bulbs have a longer lifespan than conventional light bulbs.
- For better landscape aesthetics, you can install multiple lights on strings as well.
Disadvantages of Solar Garden Lights
Unfortunately, using solar PV lights in your garden has a few disadvantages as well. These include the following potential problems:
- During the winter months and on cloudy days when the sun doesn’t shine enough, the batteries will not charge well, and you will not get full backup power for your lights.
- Batteries and LED lights operate in very narrow ranges of voltage, and sophisticated circuits are included in solar lights that increases their prices.
- Although LED lights and rechargeable batteries last longer than other lighting alternatives, the replacement of these are complex and expensive.
- In the case of solar light strings, the entire string of lights will shut off when even one light in the string is not working properly.
Will my solar light in my garden glow during winter nights or cloudy days?
The charging of the battery inside of solar lights depends on the intensity of the sunlight provided during the day. PV modules and most solar lights are designed in such way that they charge the batteries completely within 6 hours. If they do not receive enough power due to the winter season or a cloudy day, the batteries will not get charged and the amount of backup power available (and thereby the overall active lighting time) will be reduced.
What should I do if I want to increase the backup power available to power my solar light?
Most of the time, you cannot do much to increase the backup power available for a solar light as the components are enclosed in a tight casing to keep them away from dirt and water that may enter the circuit. If you can somehow open the casing and add some additional cells in parallel without damaging the setup, you can increase the amount of backup power stored to power your solar light.
What is the IP rating of the product?
Ingress Protection (IP) is the rating of a piece of electrical equipment’s enclosure to protect it from solid particles and liquids. The first number that follows after IP represents the size of solid particles, and the second number shows the angle of a jet of liquid from which the casing can protect the inner electronics. The value of dust particles starts from zero (no protection) to 6 (no dust particle is allowed). The value of water protection ranges from zero (no protection) to 9 (high pressure, high stream jet pressure protection).
What should the IP rating of a solar light be?
Solar lights are placed in an open environment and subject to direct sunlight and other environmental conditions, so these should preferably be rated at IP68, meaning no ingress or dust permitted (6) and high protection against continuous exposure to water (8).