HYBRID SOLAR LIGHTING —Light The Interiors Of Buildings With Sunlight! - IELTS Reading Answers & Explanations

You should spend about 20 minutes on Questions 1–13, which are based on Reading Passage 1 below.

HYBRID SOLAR LIGHTING —Light the Interiors of Buildings with Sunlight!

Hybrid solar lighting is a system that captures sunlight on a roof top and uses optical fibres to channel it directly into a building. The only power needed to operate it is a 9-volt battery and the energy cost reduction, worker productivity and health benefits are immense.

It was originally developed by the US Department of Energy at its Oak Ridge National Laboratory and licensed to a company called Sunlight Direct. It has already been installed in a large number and a wide range of buildings in the USA including higher education institutions, museums, department stores and other specialty stores. Initial reports declare that retail sales increase by as much as 40% when the switch is made from fluorescent lighting to hybrid solar. Furthermore, there is a major improvement in the attention spans and academic attainment of undergraduates in classrooms or lecture theatres lit by hybrid solar. It is to be hoped that the technology can soon be made financially feasible for households as well as commercial buildings.

It has been suggested that 30% of the electricity used in the USA is just for lighting and, for retailers, the estimate increases to 45%. Obviously, that figure could decrease significantly if sunlight could be brought inside. Hybrid solar lighting is predicted not only to save millions of dollars in energy costs but it is attractive for its quality which is almost identical to daylight.

A solar collector consisting of a 1.2 metre parabolic primary mirror concentrates the light toward a secondary mirror which has a special multi-layer coating that reflects only the visible wavelengths which effectively strips off the ultra-violet and infra-red wavelengths from the reflected light. This is important to reduce heat in the fibre optics which would otherwise melt. The visible light is focused from the secondary mirror towards a receiver module where it is homogenized to guarantee uniformity before it enters the fibre optic bundle which then passes into the building interior for lighting. The fibres are easily installed and replaced and unlike fluorescent lights that require energy, the hybrid solar system only needs one 9-volt battery to power the solar tracking system for a week.

The solar tracker mechanism consists of two motors that are controlled by a GPS (global positioning system) micro processor situated beneath it. This computes the exact position of the sun (based on the latitude, longitude, date and time) to within point one degree. The light collected shines brightly. Just two of these fibres emit enough light to be equivalent to a 60 Watt light bulb and there are 127 of fibres in one bundle. What if it is cloudy or rainy outside?

That's where the hybrid comes in. The lighting fixtures combine the sunlight with the artificial light from fluorescent or incandescent lamps to create a hybrid luminaire. A photo sensor in the room monitors the intensity and automatic adjustments are made in order to keep a constant level of illumination.

A room lit entirely by fluorescence has an orange glow which is not very natural. If the lighting is changed to 80% solar and 20% fluorescent, it is far more aesthetically appealing. It is estimated that hybrid solar lighting could reduce their energy bill of most retailers by 60%; and retail stores have been some of the first adopters of the new technology because of the health benefits gained from natural lighting. Studies have shown that 20% of workers under artificial light suffer symptoms of depression from Seasonal Affective Disorder (SAD). In addition, retail stores with natural lighting sold 40% more merchandise than stores with artificial light. Research has shown that biological rhythms and circadian rhythms are the secret to having successful and productive employees. Bringing in the natural light helps regulate these biological processes.

The technology has made such an impression that other scientists are looking at alternative applications: utilizing the UV light energy for hot water heating, for example. There is one limitation to the technology, however; although the plastic optical fibres are very low cost, they also have very low transmittance and extend for only around 15 metres from the solar collector. This is why currently solar hybrid lighting is primarily focused on the top and main floors of a building.

Overall, the potential electricity savings and carbon dioxide reductions are enormous. The units are designed to last twenty years and, as volumes of sales increase, the price should come down considerably. It may be a while before individual households can enjoy hybrid solar lighting but, in the meantime, there is a substantial benefit in that it is making many work and study spaces as natural and comfortable for humans as possible.