How Solar Yard Lights Work

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How Solar Yard Lights Work

If you have a yard and have ever thought about lighting it at night, then you have probably heard about solar yard lights. They are still pretty expensive, but their advantage is that you don't have to run any wiring for them. As long as a location gets direct sunlight, you can put a light there in about 15 seconds.

These lights are extremely interesting because they are almost like mini-satellites. They generate and store their own power during the day and then release it at night. This is just like a satellite that stores solar energy while it is on the sunny side of the planet and then uses that energy when it's on the dark side. In this article, you will learn exactly how it happens!

The Basics

A solar light consists of the following components:

If you pop off the cover, you will find that all of the working components are mounted as a single unit. On the back side you see this:

Next, we'll take a closer look at some of these components.

You can see the battery, LED and controller board. If you cover the light sensor, the LED turns on, like this:

Here are close-ups of the LED and the controller board:

On the other side of this module is a four-cell solar array, measuring 2 inches by 2 inches (5 cm x 5 cm), and the photoresistor:

Here is a closer view of the photoresistor:

See How do the streetlights turn on automatically at night? for more information on how photoresistors work.

Now let's see how the whole setup works to light your yard at night.

If you have read the article How Solar Cells Work, you have a basic understanding of solar-cell technology. A solar yard light uses standard solar cells in a very straightforward application.

A single solar cell produces a maximum of 0.45 volts and a varying amount of current depending on the size of the cell and the amount of light striking the surface. In a typical yard light, therefore, you need four cells wired in series (see How Batteries Work for a discussion on series wiring). In this yard light, the four cells will produce 1.8 volts and a maximum of about 100 milliamps in full, bright sunlight.

The solar cells are wired directly to the battery through a diode (which prevents the battery's current from flowing back through the solar cell at night). The battery is a completely standard AA Nicad battery. A battery like this produces about 1.2 volts and can store a maximum of approximately 700 milliamp-hours. During the day, the battery charges, reaching maximum charge except on shorter winter days or days when there is heavy overcast.

At night, the solar cells stop producing power. The photoresistor turns on the LED. How do the streetlights turn on automatically at night? shows you a very simple circuit using a transistor and a relay to control a light using a photoresistor. In the case of this light, the relay is replaced by two other transistors.

The controller board accepts power from the solar cell and battery, as well as input from the photoresistor. It has a three-transistor circuit that turns on the LED when the photoresistor indicates darkness.

The LED draws about 45 milliamps with the battery producing about 1.23 volts (0.055 watts). It produces about half of the light that a candle would. The Nicad battery, when fully charged, can operate the LED for about 15 hours.

Half of a candle's light is not very much, and if you have ever purchased one of these yard lights you know that it really is not enough to provide illumination. You use them more for marking a trail -- they are bright enough to see, but not really bright enough to illuminate the ground to any great degree.

The reason why these lights are so expensive right now is because of the solar cells and, to a lesser degree, the Nicad battery. Solar cells remain expensive because they are manufactured from silicon crystals in cleanroom conditions. They are much less expensive than they were 10 or 20 years ago, but still fairly pricey. As a result, solar yard lights cost $10 to $20 per light.

The yard light shown here uses a single LED. More expensive lights may offer a combination of an LED and a small halogen flashlight bulb. The LED is on all the time, and the light bulb turns on for a minute or two when a motion sensor detects movement.

For more information on solar yard lights and related topics, check out the links on the next page.

Solar lights are all around us – they have numerous residential and commercial applications across the UK and overseas. Products as diverse as outdoor solar wall lights and solar street lights are readily available and easy to use.

Solar lights are an ideal choice when you’re looking for exterior lighting that doesn’t need to be wired into the mains (after all, there isn’t always a mains connection nearby). They’re fully powered by the sun, not the grid, so they’ll help you to reduce your utility bills and become more energy self-sufficient while protecting the environment.

If you’re thinking about installing these innovative devices at your home or workplace, you may be curious about the technology behind them. Have you ever asked yourself how do solar lights work exactly? Have you ever wondered how they use the sun’s rays to generate electricity and illuminate everything from gardens to billboards? How do they know when to come on?

To bring you up to speed with the fundamentals, here’s the straightforward Synergy guide to the design and function of solar lights.

Key Parts of a Solar Light

Each of the following key components plays an important role in solar lighting:

Solar panel – captures solar energy
Rechargeable solar battery – stores the green electricity produced by the panel
Photoresistor – this light-sensitive sensor stops the solar light coming on when it isn’t needed
LED lamp/panel – provides impressive, high-lumen illumination. ‘LED technology generates light up to 90% more efficiently than incandescent and fluorescent lighting,’ (tree hugger, a sustainable living guide)

The Importance of Photovoltaic Technology

High-quality solar lights work hard to provide you with powerful, reliable lighting from dusk ‘til dawn. But they’re far from idle during the daytime too – that’s when they’re busy absorbing solar energy in order to charge their batteries.

They do this with the help of photovoltaic (PV) technology. Its name is derived from ‘photo’ (the Greek word for light) and ‘voltage’ (which refers to the electrical pressure pushing charged electrons around a circuit).

Let’s explore this technology in detail, as it’s really the key to understanding how solar lights work.

Producing Green Electricity during the Day

Imagine you’ve just installed a solar wall light at your property. Let’s say the compact, sleek Synergy M 3 Series SY-16 Solar Wall Light is now mounted on the wall by your front door or garden gate. Like all Synergy solar lights, it features an integrated solar panel – you can see this on the top of the unit. Thanks to the solar panel, the solar light can take advantage of photovoltaic technology.

Solar panels are populated with photovoltaic cells (solar school) (also called solar cells), which are normally made of silicon, a fundamental part of many electronic devices. We particularly like using monocrystalline silicon – it’s extremely pure, long-lasting and efficient. ‘The cells don’t need direct sunlight to work and can even work on cloudy days,’ says the Energy Saving Trust. So they’re suitable for all sorts of climates.

Each PV cell has a negatively charged layer containing silicon electrons and a positively charged layer. When the PV cells are exposed to the sun’s rays, light particles that are brimming with solar energy collide with electrons. This gives the latter the momentum they need to travel to the positively charged layer.

The flow of electrons creates an electrical current. In other words, the solar light has used solar energy and photovoltaic technology to generate 100% green electricity.

The electricity flows through wires leading to the rechargeable solar battery and charges it. The battery stores the electricity until it’s time for the solar light to illuminate its surroundings.

Providing Reliable Illumination at Night

The photoresistor stops electricity reaching the LED lamp/panel when it senses daylight, to avoid unnecessary illumination and power wastage.

When the photoresistor no longer senses daylight, electricity is directed to the LED lamp/panel and powers it throughout the night.

When the photoresistor senses daylight again, it ensures the LED lamp/panel switches off.

Synergy – Enhancing the Performance of Solar Lights

It’s important to emphasise that not all solar lights are created equal. Synergy solar wall lights, as well as our other solar lights, stand out from the crowd because they benefit from a variety of performance-enhancing features, ensuring they serve you as well as possible.

For example, our solar wall light range includes:

Adjustable solar panels and LED lamps/panels
Continuous or motion-activated illumination options
Seasonal/mood lighting modes
Thermal protection to prolong battery life
Corrosion resistance

Plus, even in bad weather our solar lights can work at full efficiency for a week or more on a full charge.

They really are life-enhancing.

Whether you're looking to improve efficiency, reduce costs, or stay ahead in the market, Solar Street Light can offer significant value, and you can make better choices tailored to your specific needs.