Lighting accounts for around 15% of the energy bill in most homes, and around 25% in commercial buildings. It is supplied by electrical power plants using fossil fuels, and is responsible for a significant percentage of carbon dioxide emissions, a leading cause of global climate change. Because of this, the building industry has targeted lighting as a key element in sustainable design, and there is now a global movement to develop and implement lighting solutions that meet people’s needs and concerns, and address environmental regulations.
The most sustainable lighting is natural daylight. It is not only a free renewable resource but it also has well-documented health benefits. Careful architectural design is required to maximise natural light in a building while maintaining indoor temperature regulation and reducing direct light glare. The strategic placement of windows, skylights, light shafts, atriums and translucent panels in harmony with other building components, such that light is reflected evenly throughout internal spaces, is known as daylighting design.
Sunlight Transportation Systems
An emerging new technology is that of sunlight transportation. Natural sunlight is collected on roof panels and transported into a building via fibre optic cables for distances up to 15 metres. These sunlight-piping systems can be used in combination with <#66#>solar panels<#> to integrate natural and artificial light systems, so that there is always light in the home.
Energy Efficient Light Bulbs
The sustainable building industry is primarily focused on energy efficient lighting solutions. Standard light bulbs, known as incandescent bulbs, are known to be highly inefficient. Electricity is passed through a metal (tungsten) filament that heats to over 2000º Celsius and glows to give off light. Only 10% of the electrical energy is converted to light; 90% is wasted as heat. Halogen bulbs are similar but instead have a small pocket of halogen gas that reacts with tungsten to produce light. They burn brighter, use less electricity and last twice as long as a standard bulb, but are still inefficient compared with other forms of bulbs.
Energy efficient light bulbs use significantly less energy than incandescent bulbs, and also last longer. There are two main kinds: Compact Fluorescent Lights and Light Emitting Diodes.
Compact Fluorescent Lights (CFL)
These are small versions of full fluorescent lights, and consist of a glass tube coated with phosphor, filled with gas and a small amount of mercury. Electricity jumps off electrodes on the end of each tube, and excites the mercury molecules to emit ultraviolet light. This excites the phosphor coating, which emits visible light that shines out of the tube. CFLs give off the same amount of light as incandescent bulbs, but they are up to 80% cooler, are 4 times more energy efficient (to replace a 60-watt incandescent, you only need a 15-watt CFL), last 10 times longer (up to 20,000 hours), and are responsible for the emission of 70% less carbon dioxide.
CFLs come in many different configurations and wattages, and are suitable for all lighting purposes. Although more expensive to buy than a standard bulb, they easily recover their costs in energy savings. On the downside, they contain trace amounts of mercury, which is hazardous to health and the environment. Care needs to be taken to ensure the glass tube doesn’t break and that the bulbs are disposed of safely.
Light Emitting Diodes (LED)
LEDs are small, solid light bulbs that are lit by the movement of electrons in a solid semi-conductor material as electricity is passed through it. This is also called ‘solid state lighting’, because it uses a solid material, as opposed to gas (CFL) or filament (incandescent). LEDs are extremely energy efficient, lasting over 100 times longer than incandescent bulbs, and up to 10 times longer than CFLs. They have low heat generation, low power requirements, and are highly durable because there is no filament or tube to break.
LED is a relatively new technology, and currently the bulbs are most suitable for track and recessed lighting, where a pointed light is required rather than radiated light. They are more expensive than CFLs, but energy savings over their lifetime means their cost is soon recouped. Because their power inputs are minimal, LEDs are readily combined with solar panels to provide reliable, energy efficient lighting day and night.
The Future is Bright
Along with technological solutions like energy efficient light bulbs, and using renewable energies for their electricity source, simple practices such as turning lights off, using dimmers and timing switches can all help to make lighting more environmentally friendly. Unfortunately these practices are not yet available with all energy efficient bulbs. Furthermore manufacturers still need to address issues of waste, pollution and energy in their products’ life cycle. The building industry is committed to reducing the environmental impact of lighting, and new buildings now include lighting design issues from the outset. While there is still a long way to go before lighting can be said to be truly sustainable, the future of sustainable lighting looks bright.