Gone are the days of dim, barely flickering solar lighting that once lined residential paths and gardens. Outdoor solar lighting is making a comeback and is more popular than ever given the improved technology and function. The solar lights used in homes today utilize super-efficient solar collectors, more powerful batteries, and low-voltage LED bulbs, making them a stylish, yet earth-friendly way to illuminate the exterior of your house.
And today, solar cells are fixed to outdoor lights of all sorts—security lights, deck lighting, Christmas lights, and of course garden lighting. Nowadays they’ve got motion sensors that set lights to turn on in occupied spaces and photo sensors that ensure your lights are only on when the sun’s light is dim. It’s clear that solar outdoor lighting has come a long way from its first uses.
Solar, a brief history
Enormous quantities of energy reach the earth from the sun—6,000 times more than is actually consumed by people every year. This energy can be collected and used for various electrical purposes— just think of the potential for powering our lives cleanly and sustainably! The would-be advantages of solar energy have been evident to scientists for centuries who have been working diligently to harness this power in new and interesting ways, but it’s only been within the last few decades that real progress has been made.
What makes the sun’s energy so powerful? Photons. They’re the essence of solar energy. Discovered by a French physicist named Antoine Henri Becquerel in 1839, photons were not readily converted into electricity (volts) using photovoltaic (PV) cells until the 1954, when they were used primarily in space exploration applications. Today, PV cells are being used throughout the world to power anything from lights to computers, mobile devices to kitchen appliances.
How do solar collectors work?
PV cells, also known as solar cells, are made with semiconductors, such as silicon. When photons hit the PV cells—and remember, even on cloudy days there’s enough solar energy to produce power—their energy is absorbed by the semiconductor material. The electrical current is then run through an inverter to convert DC (direct current) power into AC (alternating current) power. AC energy can then be used to power a variety of electrical devices such as lights, computers, mobile devices, and appliances.
But if solar energy only reaches the earth when the sun is shining, how is it used to power things like appliances and lights at night? For this, we depend on the energy-storing power of batteries. Daytime solar energy is collected and stored in batteries connected to solar cells. Then at night, after the sun goes down, the lights tap into the charged batteries and provide clean, virtually cost-free illumination.
Solar energy has been in use by many industries for a long time. Highway safety equipment, oil companies, and telecommunications systems have tapped into this energy source by installing solar cells on call boxes, road signs, and remote communications towers. Of course, space agencies have also made use of this tremendous force, too.
But industry isn’t the only beneficiary of the green power that is solar energy. Do you remember when solar calculators first emerged? Since then, solar cells of all shapes and sizes have been installed on all kinds of consumer goods, including radios and camping gear, motor homes and boating equipment, and yes rooftops, too. And industry continues to find exciting new solar applications. Consider that it’s now being used to power lawn mowers, hybrid cars, in parking lots (where they provide shade as well as power), and even street lighting. And with the efficiency of solar cells increasing all of the time, they’re becoming even better at collecting solar energy.
Keep in mind, though, that solar technology isn’t without its problems. Some semiconductor materials, such as copper indium diselenide or cadmium telluride—both highly toxic substances that can cause serious human health problems when inhaled or handled—make discarding PV systems somewhat challenging since they are technically considered hazardous waste. At this point, there are no formalized recycling programs in place to properly dispose of these materials, but thankfully, solar panels commonly last 30 years or more, so we’ve got time to figure out a way to safely recycle them.
Eco-advantages of solar lighting
The lighting industry has been refining the principles of solar power for use in their products for many years, making solar lighting one of the most easily-accessible options for consumers. And the potential for energy savings is huge. The US Department of Energy tells us that lighting accounts for around 22 percent of all electricity consumed by Americans. That’s $55 billion of electricity every year or 100 power plants worth of energy. Believe it or not, the average home produces more than two times the greenhouse gases generated by the average car, so reducing your overall electricity consumption from lighting will go a long way to shrinking your overall carbon footprint.
But why are conventional lights so much more costly? These energy-guzzlers require so much power because of the inefficient technology they employ. The incandescent bulb—that’s your standard light bulb—is incredibly poor at converting energy into light. In fact, by and large it uses only 10 percent of the electricity it draws to produce light. The rest goes to generating heat! This waste costs us in two ways: obviously it requires more energy to produce brighter light, but with all the heat it throws, it also adds to our cooling bills. Turning lights on during a hot day will actually make your fans and air conditioners work harder in order to cool your home.
Our consumption of electricity is a major source of pollution and climate-changing gases. Most power stations in the US (50 percent!) consume coal as their energy source, making them one of the dirtiest industries within our borders. Coal burning emits the highest quantities of mercury as well as large volumes of sulfur dioxide, nitrous oxide, and bundles of carbon dioxide. These chemicals become airborne and eventually land up in waterways where they harm wildlife and poison our drinking water.
Coal isn’t the only dirty energy source in the US. We also import enormous quantities of crude oil from other countries, which is refined into various other substances including fuel oil, diesel, and natural gas (to name a few). Like coal, burning these fuels creates many harmful chemicals and gases, including methane and carbon dioxide—two troublesome heat-trapping gases.
And then there’s nuclear power. Most nuclear power plants use uranium in a fission process that splits atoms apart. The net result is radioactive waste which remains harmful to humans and other organic life for hundreds of years. Storing and protecting this waste product is expensive and dangerous in more ways than one. The risk of radiation poisoning from nuclear by-products is great, but that’s not the only threat. The potential for Chernobyl-like disasters during normal operation is always a possibility, and so is the likelihood of terrorists targeting these facilities to inflict maximum destruction.
So, it’s in our best interest to find renewable methods of illuminating up our lives. Enter solar lighting. Generally speaking, outdoor solar lighting consists of four main components: highly-reflective, super efficient light bulbs, photovoltaic panels, batteries, and a small microprocessor that controls the system and ensures that the batteries do not become over-charged. Improvements in these components are what have boosted solar outdoor lighting’s reputation in recent years.
The magic of LED bulbs
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Light Emitting Diodes (LEDs) are solid state bulbs that are even more efficient than even the new and efficient compact fluorescent (CFL) bulbs. Although LEDs are somewhat expensive, they use only about 20 percent of the energy consumed by common incandescent bulbs and they last 133 times longer, making them extremely cost-effective. Since most last between 50,000 and 100,000 hours each, when used in night-only light fixtures, these bulbs should keep going for approximately 20 years.
They have other important benefits. Since they aren’t constructed with a filament like incandescent and CFLs, they’re very durable and difficult to break. Their solid state is what makes them nearly impervious to bangs and bumps. What’s more, they don’t heat up anywhere near as much as conventional bulbs. Incandescents produce nearly 85 British Thermal Units (Btus, a measure of energy) per hour, where LEDs produce on 3.4 Btu/hour.
They’re small—about one-fourth of an inch each—making them ideal for small applications, like power-indicators on computers and small appliances, lighted buttons in remote controls, etc. But when combined in clusters of two to 36 bulbs for greater light intensity, they give off much brighter light.
LEDs provide very focused light, so they are very well suited to replace standard light bulbs for things like track light fixtures, task lighting, and portable equipment like light flashlights and headlamps. They’re also becoming increasingly popular in outdoor lighting applications where they can be used for driveways, gardens, pathways, and security lights. And since they come in a variety of colors and configurations, there are numerous possibilities for outdoor use.
Improved battery technology
But a wireless light fixture is only as good as the battery that powers it. Nickel metal hydride (NiMH) batteries are the most common rechargeable batteries used in outdoor lighting today. They were first developed in the 1980s and have been heralded as more eco-friendly options ever since.
Unlike the old nickel cadmium (NiCd) standbys, NiMHs use a hydrogen-based alloy instead of cadmium. Cadmium is an extremely toxic metal that can be inhaled during the manufacturing process and can leach into soil and water when not recycled properly. It has been known to cause many serious health conditions, including renal abnormalities, cancer, pulmonary edema, and even death.
So, NiMH batteries are more environmentally-friendly than traditional NiCd options. They’re also much more efficient since they provide two to three times the power capacity of NiCds. And while rechargeables are often somewhat more expensive to purchase than one-use batteries, these ones are relatively inexpensive compared to other rechargeables. And they’ll last for years (compared to the short lifespan of non-rechargeables) so are worth the upfront cost.
Install these little power houses into outdoor lighting, combine them with solar collectors and ultra-efficient LED bulbs, and you’ve got a great light-making machine. But what increases their efficiency even more are photo sensors installed in many outdoor lighting fixtures. These simple devices constantly monitor sunlight levels, waiting until the light dips to a certain point before turning the lights on. This ensures that the solar outdoor lights are used only when the light dips below a certain level, which cuts battery consumption and wear and tear on the bulbs, too.
- There’s no wiring, so they can be installed in non-powered areas of your property, and without digging trenches
- They run energy-free, cutting your lighting electricity needs dramatically
- Since they’re off the grid, they’ll work even when the electricity goes out
- They’re extremely reliable and will work even after cloudy days
- LED units last much longer than incandescent or CFL fixtures, requiring fewer bulb changes
- They require much less energy than incandescent, which will lower your overall carbon footprint
- Nickel metal hydride batteries are generally used, which are less toxic than nickel cadmium batteries
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