Energy-Saving Usage in Lighting
Good lighting is a fundamental requirement for the efficient operation of a farm. It is required for both farmers and in the case of animals, for stock. For example, research on the performance of dairy stock indicates that enhanced lighting levels can improve lactation and growth. For humans, it supports visual acuity, performance and safety both through higher lighting levels and better colour rendering. But lighting is also costly to provide and run, so choosing the most suitable fitting layout and control equipment is important.
Natural lighting can make a very big contribution to dairy buildings, both in cubicle housing and for parlours and other areas. Providing 10-15% roof light area will be enough to provide between 100 lux and 500 lux through natural lighting, depending on the time of the year. The key to sustaining this is to maintain the cleanliness of the roof lights. Transparent wall sections are also effective. Naturally lit buildings need to be well ventilated to counteract the effects of heat build-up from solar gain.
Even with the best natural lighting resource, artificial light has to be used to guarantee light in all conditions, times of day, and times of year. Artificial lighting is costly to provide so it is always best to make the most of natural light and use artificial light to provide the rest.
Lighting output and level
These are specific in units of lumens and lux. The difference between the units lumen and lux
is that lux takes into account the area over which the luminous flux is spread (Table 1). A
flux or luminous power of 1,000 lumens, concentrated into an area of one square metre,
lights up that square metre with an illuminance of 1,000 lux. The same 1,000 lumens spread
out over ten square metres produces a dimmer illuminance of 100 lux. Mathematically, 1lx =
1m/m2. Lux is not a linear scale, so a doubled lux level does not appear as twice the
brightness to the eye. In fact, you have to increase lux levels by four to double the
perceived light level, or by 16 to double it again.
Tasks and lighting requirement
Table 2 gives some guidance on lighting levels and desirable light properties. There are few definitive standards in this area, so this table contains figures from practical experience and from similar practice references.
There is a wide range of lighting sources to choose from (Table 3) and each type has its own unique set of characteristics. These include: capital cost; efficiency; longevity;
colour; appearance; temperature; shadow potential; and, start-up time. It is important to try to consider the relevance of these when choosing the right lamp type. The
quality of the fitting and its ability to avoid being impacted by ammonia gases is very important, which LEDs are very prone to. LED retrofits work economically on pig and
poultry farms, but a retrofit on most farms has to be justified, as lights are not on a lot of the time.
This is important as it will determine the performance of the lighting for the life of the system. It is therefore worth getting some professional help to get the lighting
- consider the way lighting is used on an everyday basis: where is the right place for the switches?; and, is it possible to get different lighting levels by simply
grouping and switching the lights in banks?
- are lights in a position where they can be readily cleaned and where the bulbs can be safely changed?
- consider reflectivity of roofs and walls – colouring surfaces white or a light colour can increase the lighting level
- fittings in most cases will have to be water and dust proof – make sure the ones you choose are up to standard.
Energy-saving opportunity in lighting
Fact sheet produced by Barry Caslin, Teagasc, Rural Economy and Development Programme.