A Successful retrofit
A Successful retrofit
An example of a successful retrofit of existing traditional lanterns in central London in the early 1970s and 80s.
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The lanterns originally had 1 500-W incandescent lamps which in the first retrofit were replaced by 400-W high-pressure sodium lamps; total annual savings were ~US$ 240 000 and the load reduction ~300 kilowatts.
However, when later fitted with high-tech optics, the lampscould be further reduced to 250-W HPS. This not only reduced light escaping into the sky, but as an extra bonus also caused less disturbing glare for people living in the area. Note the black shield on the pre-retrofit luminaire (upper photo) which was mounted there to protect someone living nearby from intrusive glare. Once the luminaires were converted to advanced optics, the shield was no longer needed.
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