Power consumption

Part 1 - 100 Watts x 234 lamps (if one lamp per zone) = 23400 Watts or 23.4 Kw

So, 23.4 kw x 0.07 per kwh = 1.638 per hour

Part 2 - Use light pipes with fiber-optic or mirror reflection and solar tracking collection of daylight so you can turn the lights off during daylight hours. Or, use LED lighting and solar power collectors to operate during daytime. This approach is a little expensive to install but it will pay for itself in savings many times.

Thank you

Sorry but that's all wrong.

A 100W HPS lamp will use a ballast that consumes about 12-20 watts. Depends on quality and type. So:

120 x 234 lamps = 28,080 = 28 kW x 0.07 = 1.96 per hour.

Fibre optic etc only work during the day and offer no saving at night. There would be problems getting the light tubes into an underground carpark. And much too costly.

LEDs are a very inefficient lightsource, while HPS is the most efficient known. LEDs are less than half the efficiency. Long life though so low maintenance. But practical LEDs to replace 100W HPS are way too expensive.

The way to save energy is to turn the fittings off. Unfortunately HPS do not turn off and on very well. The solution is to use fluroescent instead, preferably dimming 35watt T5 (which are as efficient as HPS). These can be dimmed to avoid over illumination (a problem with carparks as you must assume a low maintenance factor of about 0.5) and turned off when the space is unoccupied (via motion sensor). Expensive though, so you have to work out the payback period.

+10 points for including ballast loss. -9 points for assuming that they are all 20 Watts. Where was it stated that the garage was underground? Oh, and thanks for the tip about the fibre optics at night. On my planet, the Sun never sets.

And where did you get your information about LED lighting being inefficient? The fluorescent lighting industry is very, very concerned about LED lighting. The lighting industry magazines have been highlighting their use in European markets for years. "less than half the efficiency of HPS" what? No way! Your information is contaminated.

While I agree that fluorescent lighting is probably the best choice at the moment, (at least in the US market) I disagree that T5 is the solution. T8 is a much better choice because T8 lamps offer the highest lumens per watt. T5 lamps are decorator lamps and the latest fashion. That does not make them the best choice.

Using a fluorescent lamp with a dimming ballast is not an efficient use of lamp products. A dimming ballast will reduce the operating temperature of the lamp and reduce the lumens per watt substantially. Consequently your savings go away. Secondly, no two manufacturers of fluorescent have been able to make a coil (emitter) with the same electrical characteristics from one day to the next or from one manufacturer to the next, so keeping a fluorescent lamp operating at reduced power is risky because of emitter loss (i.e. reduced life)

And motion sensors are not expensive unless you try to put one in every fixture. Frequent On and Off cycles, however, shortens fluorescent life dramatically.

"A 100W HPS lamp will use a ballast that consumes about 12-20 watts. Depends on quality and type."

What???

A 100W ballast CONSUMES at least 100W! Actually a little more. I just looked at a few, the input watts are between 109 and 128W.

Maybe what you meant is that a MH fixture that puts out the equivalent light output of a 100W incandescent lamp will consume 12-20W. That I would believe.

But if he is using 100W MH lamps, the ballasts will consume slightly MORE than 100W each.

109W input example

128W input example

HPS is just about as efficient a source as you can get.

Will the design accomodate 70W. HPS without going below acceptible ltg. levels?