Energy Efficient DC Lighting
Lighting is a very popular use for alternative energy power sources. The convenience of electric lighting in a remote cabin can be obtained with a relatively small power system. There are a variety of options available for designing an alternative energy lighting system, but deciding on the best system for a particular need is fairly simple.
- AC vs. DC Lighting
- Types of DC Lighting
- Lighting System Suggestions
- Related Product Information
Almost all on-grid electrical systems use 120 volt AC lighting. AC lighting fixtures are widely available at hardware stores and even many department and grocery stores. The convenience of choosing AC lighting is that accessories are easily obtained at relatively low prices. Also, when installing a new wiring system, AC power can run on much smaller gauge wiring, lowering materials costs.
There are two major drawbacks to using AC lighting in an alternative energy system. First, in order to run 120 volt AC power from a storage battery bank, an inverter needs to be installed into the electrical system to convert DC battery power to AC. This can significantly increase the overall system cost. The second drawback is that AC lighting is much less energy efficient than a DC system, meaning the renewable energy generators need to be capable of producing more power to run the same number of lighting fixtures.
Low Voltage* Lighting
DC lighting has the advantage of being very energy efficient. A smaller solar panel or wind generator can be used to run a DC lighting system than would be required for an AC system. Also, since DC lighting can be powered directly from the battery bank, the added expense of installing an inverter is not necessary. Although DC lighting fixtures are more difficult to find, standard incandescent and halogen lighting fixtures can be easily connected to 12 volt DC power.
The major drawback to DC power is in the wiring. Direct current requires larger gauge wiring than AC power, which increases material costs considerably. In essence, if the wiring runs between light fixture and battery bank will need to be 35 feet or more in length, or if the building is already using an inverter for other reasons, AC lighting should be considered to save on wiring and fixture costs.
Since AC lighting equipment is easily obtained, and more familiar to the average consumer, we will concentrate on the varieties of DC lighting available, and their various advantages and disadvantages. (One note on AC lighting: many efficient AC fluorescents will not always run reliably on inverter power, especially modified sine wave current.) For indoor lighting, incandescent, halogen and fluorescent fixtures can be used.
Incandescent lighting is the least expensive of the three types of lighting, but is also the least efficient. However, DC incandescent bulbs are still about 30% more efficient than equivalent AC bulbs. Wattages ranging from 5 to 100 watts are readily available for DC systems. As far as lighting fixtures are concerned, DC and AC incandescent bulbs will fit in the same fixtures. Any standard size lighting fixture can be used in either type of system. For a DC system, the fixture will be wired to a DC power source, and fitted with a DC bulb. For an AC system, it will be wired to AC power, and an AC bulb will be used.
Halogen lighting tends to be more expensive than incandescent bulbs, but are approximately 30% more efficient than a DC incandescent bulb of the same wattage. Also a lower wattage halogen bulb can be used to produce the same amount of light. Halogen bulbs produce full-spectrum light, which appears brighter than limited spectrum incandescent output and causes less eye-strain. 12VDC halogen bulbs can be used in the same lighting fixtures as DC incandescents, either directly or with adapters, and the regular fixtures simply need to be attached to a 12VDC power source, instead of a 120VAC source.
Fluorescent lighting is generally three to four times as efficient as halogen or incandescent lighting in a 12 volt system, but has a much more limited selection of fixtures available. While halogen and incandescent bulbs can use the same fixtures as regular 120VAC bulbs, fluorescent fixtures must contain 12 volt DC specific ballasts. Electrically inclined individuals could purchase a regular 120 volt fluorescent fixture and substitute 12VDC replacement ballasts for the 120VAC originals, but in general it is probably best to purchase a DC specific fixture.
On the other hand, while specific 12 volt bulbs must be purchased for halogen and incandescent lighting, all fluorescent bulbs are essentially the same. Once a 12 volt fluorescent fixture is purchased, any regular fluorescent bulb can be used in it. The exception is compact fluorescent bulbs designed to fit in regular lighting fixtures. With these bulbs the ballast is attached to the bulb itself, and a special DC compact fluorescent bulb would have to be purchased for a DC lighting system.
For a small remote cabin, a DC lighting system is an excellent first step into alternative energy. The convenience of electric lighting without the noise of a generator powering it is a significant benefit with a relatively low price tag.
For larger homes, if major living areas are close to a convenient battery storage area (like an attached garage), a mixed AC/DC lighting system is a relatively simple way of reducing monthly power bills or maximizing efficiency of an existing alternative energy system. DC lighting could be used in living areas, with AC lighting in the less-used and more distant bedroom areas.
There are many options to consider for integrating low voltage DC lighting into almost any electrical system. A consultation with an experienced DC electrical dealer can help in designing an optimal lighting system for any need.