Developers and property managers are constantly seeking ways to minimize the use of electricity.
This can be achieved by migrating from filament based light bulbs (above) to fluorescent (CFL) or even better to LED bulbs. Other ways include using timers, motion detectors or light sensor technology.
CFL Light Bulb
But the most challenging one has been the one that harnesses the natural (and free) light provided by the sun.
The most common way to harness this power is twin stall skylights or roof windows on the roof and that allow for natural light to penetrate. The downside to them is that they only provide light to the area directly below it.
Another option is a sun tube designed to provide natural light into corridors, stairs, cupboards, bathrooms, etc where the installation of a skylight or a roof windows are not feasible. The way it works is that a roof-mounted dome captures the light and channels it through a reflective tube down to a diffuser located on the ceiling of the space where you want natural light. The benefits to the tube is that they can go 30 feet or more from the dome and because the tube is flexible the light can be directed where you need it. The best example is an installation of a light tube from the roof into a poorly lit basement. Companies that sell tube systems also provide diffuser options.
Light tube sketch and diffuser
Light tube cost between $150 and $400 and the installation could run anywhere between $300 to $2,000 depending on site conditions.
While these tubes work well and are an affordable way of harnessing free natural light they are intended for use in residential applications of 100-500 sf
Another option for areas that are not accessible to rooftops is to install the Coelux skylight. This product is an artificial window that claims to reproduce the natural sunlight and space of the outdoors. This product renders a very realistic natural light but the drawback is that the cost is prohibitive for a commercial application. (This product uses electricity)
Coelux Light Panel
Sun port recently installed a system in the Lowline Park of lower east side of Manhattan that uses mirrors to channel natural light into this below grade park.
Natural light is channeled through a series of compact up the convinces over for distances of up to 600 feet. The sunlight is directed to a concentrator with parabolic mirrors. The sunlight then travels through a series of relay lenses until it reaches a diffuser.