Renew Magazine

Installation has begun on the first set of LED lights on George Street, in front of Sydney Town Hall. Following a successful 18 month trial in Alexandria Park, Kings Cross, Martin Place and Circular Quay, the LED roll-out is a $7 million, three year project.

In the public survey conducted after the trial, 90 per cent of people said the new lighting appealed, with three-quarters saying it improved visibility.

LED lights are made up of a semi-conductor material and consequently reduce emissions and halve energy use. “Replacing 6,450 conventional lights will save nearly $800,000 a year in electricity bills and maintenance costs,” said City of Sydney Lord Mayor Clover Moore.

The LED lights require far less electricity and last much longer, reducing the 30 per cent contribution public lighting previously made to Sydney’s greenhouse gas emissions.  This is equivalent to 2861 tonnes or taking 940 cars off the road.

Sustainable Sydney plans

Sydney has positioned itself as Australia’s first carbon neutral city, and set out in the Sustainable Sydney 2030 Plan an ambitious target to reduce greenhouse gas emissions by 70 per cent, based on 2006 levels.

To achieve this target, the UK energy expert Allan Jones has been appointed to lead the project. His previous work reduced greenhouse gas emissions in the city of Woking, Surrey by 80 per cent.

Sydney will be transformed into a low carbon city powered by trigeneration systems and renewable energy. As well as electricity supply, trigeneration can also heat and cool buildings, and is three times more efficient than current systems.

Adding to the beauty of the plan is the capacity to add a decentralised water system and an automated waste collection process.

The plan stretches beyond council sites to household strategies and also includes supplying affordable housing to the residents of Sydney, in an environmentally sustainable way.

Sydney’s switch to LED lighting is a significant decision as Australia moves to a low carbon future. “Sydney’s leadership provides a clear signal to other Australian councils: LED technology is ready,” said Caroline Bayliss from the Climate Group.

There’s a vast array of light fittings and lighting systems available, and a number of lighting technologies including the horribly inefficient but very popular incandescent, the halogen (a glorified, slightly more efficient incandescent), the fluorescent, compact fluorescent, and more recently, Light Emitting Diode, or LED.

With almost all lighting technology moving towards LEDs, this guide will primarily focus on LED technology. In 10 to 20 years, most other light sources will have disappeared in favour of the robustness, longevity and energy efficiency of LEDs.

Types of lighting
When considering lights and light fittings, you need to decide what type of lighting you want for each situation.

Lighting generally falls into four categories—general illumination, task lighting, ambient/mood lighting, and outdoor lighting. The degree of intensity will depend on personal preference and the colour of the walls and furnishings. Darker walls generally need more light to achieve the same level of perceived brightness as lighter walls.

General illumination can be of a fairly low level—enough to easily see by, but not so bright that the whole room becomes suitable for reading. However, this is a personal preference and many people like to be able to light the entire room brightly when needed, whereas others may opt for a combination of low level general lighting and small task lights near their chairs for reading.

Mood lighting may also be a concern and needs to be considered at the planning stage. The house may have a feature that would benefit from a well placed spotlight or uplighter, but lights like these are often left on for long periods and can consume a great deal of energy if the wrong lighting is used.

Garden lighting is generally either floodlighting or feature lighting, where particular plants or garden furnishings are lit individually, often by coloured lamps, for effect.

Zero energy options
While this article deals with electric lighting, there are a couple of other options that should be considered. Skylights and light pipe systems can provide more than adequate lighting levels with no use of electricity at all and, if well placed, won’t heat the room unnecessarily.

Another option is fitting reflectors to already installed fittings. Fluorescent fittings can particularly benefit from a reflector. Indeed, fitting a reflector behind a single tri-phosphor tube can result in lighting levels equal to using two cheaper quality tubes with no reflectors. This means that combining a reflector and good quality tube can effectively halve lighting energy consumption.

Energy, power and voltage
Which brings us to one of the most confusing aspects of lighting for many people.

Many lamps, particularly halogen downlights, are sold as ‘low voltage’, with the packaging implying that this equates to low energy consumption. This is rubbish. The important factor is the power rating of the lamp. Fifty watts is 50 watts, regardless of the voltage it is supplied and used at. A 12 volt bulb uses a 240 volt to 12 volt transformer to run it, so this transformer will draw 50 watts to run the bulb, plus a bit of extra that is lost in the transformer as heat.

So, when comparing bulb energy consumption, you must look at the wattage, not the voltage.

Power supplies of this type may not seem very useful, but you can in fact use them to drive LEDs for lighting with very little effort. What’s more, if you match the LED voltage to your power supply output voltage you can end up with a quite high overall system efficiency.

It should be mentioned here that there are two common types of power supplies. The first is the older type that uses a heavy iron core transformer. These are usually unregulated and their output voltage is dependent on the load placed on them. For instance, a 12 volt supply might actually produce around 18 volts with no load. This variable output makes them a little harder to use. What’s more, the efficiency of this type of supply can be quite low, so they are often not a good candidate for reuse in this manner. Fortunately, most manufacturers are changing over to switchmode power supplies.

Switchmode supplies are generally regulated so that their rated voltage is the voltage that you get out of them. Also, their efficiencies are usually better than 75% at their rated load. Like most plugpacks, switchmode power supplies have isolated outputs, which allows you to connect multiple supplies in series to get higher voltages.

The easiest way to tell which type of supply you have is by the size and weight. Iron core power supplies have a large and heavy transformer inside so they are usually bulky and heavy for their rated output. Switchmode supplies are much smaller and lighter in most cases.

Voltage matching

So how do you use your old power supplies for driving LEDs? Let’s look at an example to explain how to match the LED voltage to the power supply.

You might have a spare 12 volt, 500mA power supply. This is ideal for driving three 1 watt white LEDs connected in series. A single LED might have a forward voltage of around 3.5 volts. Three LEDs in series adds up to 10.5 volts, so any simple current limiting driver (such as a linear driver or resistor) only needs to drop around 1.5 volts (LEDs are current driven devices, so you must have some form of current limiting).

This means that the LEDs receive 85% of the power coming out of the power supply. If the plugpack has an efficiency of 80%, then the overall efficiency of the plugpack/LED driver setup is 0.85 x 0.8 = 68%. In the scheme of things, this doesn’t seem that high, but if you calculate the total efficiency of power input to light output, you will find that your home-made LED light can be more efficient than most domestic lighting systems.

For instance, if high efficiency LEDs such as Q5 bin Cree XR-Es, which have an efficacy of over 100 lumens per watt, are used, then the light fitting could have an efficacy of around 70 lumens per watt overall. This is better than almost all domestic lighting systems except strip fluoros.

LED driving options

So what are the options for driving LEDs in such applications? LED drivers fall into two categories: switchmode drivers and linear drivers.

The aim of the retrofit was to eliminate not only halogens, but fluorescent lamps as well. While fluoros use a great deal less energy than halogens and produce much less heat, they do have drawbacks, such as a long start-up time to reach full brightness, and of course the tubes contain small amounts of the very toxic metal mercury. So, of course, we were aiming to change the lighting to LEDs.

The first step was to find out what LED options were available. This retrofit had to be done to a budget, but it also had to be done to a level of quality, so it was important to find the most suitable solution rather than opting for what was easiest to get. Of course, the best way to find out what’s out there is to look online, and after considerable searching and a number of phone calls, we put together a list of the most viable options.

In the end it was decided that standard Crompton CFL downlight fittings would be used, with the CFLs replaced by LED bulbs. The final tally was eight of the ZetaLux warm whites, along with two EvoLux warm whites, which would be spare bulbs in case the tenants needed some extra light in the kitchen area. Both of these bulbs come from EarthLED and have UL listing and FCC approval. While that doesn’t mean much to Australian authorities, it shows the bulbs have been tested and approved elsewhere.