In ‘Lighting’ Category
Energy saving products guide
We all have to reduce energy use, carbon price or not. Lance Turner identifies the home energy use culprits and nominates the best appliances, gadgets and DIY options for an energy smart home.
Okay, so you think you are relatively energy efficient, but those energy bills just keep going up. The cost of energy isn’t going to fall any time soon, so the trick is to simply use less without making life harder or more complex.
READ MORE »There’s many things that can be done to reduce energy use. We are surrounded by ‘stuff’ that uses energy, but does it really have to use as much as it does? Are there better options, and what should you look for when upgrading?
While many would argue that we could all do with having fewer gadgets and gizmos (and that’s a valid argument), the world has become an electronic one and that isn’t likely to change any time in the near future. So, given that, we should try to reduce the energy used by all these gadgets as much as possible.
Where the energy goes
So just where does all the energy that your home and its appliances use actually go to? Figure 1a, below, shows a breakdown for the average Australian home (Baseline energy estimates from Australian Greenhouse Office, 2008).
The biggest energy user is heating and cooling, followed by water heating and ‘other appliances’, which covers pretty much every appliance and device in your home except cooking and refrigeration. It also excludes standby loads, which is listed separately. A standby load is the energy used by an appliance when it is not being used for the task it was designed for. For instance, when your microwave is sitting there displaying the clock but not cooking, the energy it is using is the standby use.
But it’s not just about energy use, but also the greenhouse gas emissions from that energy use that must be considered. After all, some energy sources are much cleaner than others.
Read the full article in ReNew 117
New uses for old phone chargers
New electronic devices usually come with a charger or power supply. But what happens to those power supplies when the appliance dies and you buy a new one? Lance Turner shows how to reuse them for some simple but resourceful lighting projects.
The power supplies that come with most small appliances, such as mobile phones, are generally very similar. They are usually rated somewhere between 5 volts and 12 volts and may have current outputs up to about 2 amps.
READ MORE »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.
Read the full article in ReNew 109
Do-it-yourself: Bringing sunlight indoors
There’s no doubt that the ultimate lighting is sunlight, but how do you light a room that is unable to have a skylight fitted? Lance Turner takes a look at how it’s done.
It’s not always easy to bring the sun indoors, but with a little ingenuity, it can be done. There are several methods that can be used to transfer light from your roof to a room needing a bit of brightening up.
READ MORE »The first method is the common skylight. These usually consist of a transparent or translucent panel in the roof and a corresponding diffuser panel in the room directly below it. The space between the roof panel and the ceiling diffuser is usually enclosed to make a duct. The skylight may be vented to help eliminate heat ingress while allowing in the light.
A skylight is the simplest solution where the room to be lit is directly below the roof. However, there are situations where this isn’t the case and another option is required.
Light doesn’t have to move in a straight line from the roof panel to the room diffuser. If you need to separate the two panels by a short distance horizontally then you can use a ducted system. These use an internally reflective duct or tube to bounce the light from the roof collector to the room diffuser. They can be thought of as a crude fibre optic system and can be quite effective in getting the light where it’s needed. The Solatube system is a good example of these.
Both the direct lighting and the ducted type skylights are quite common in Australia and are readily available. If you think your home could benefit from fitting a skylight or light duct or two (or three) then pick up the phone book, there are plenty of manufacturers and installers listed there.
There are times when the room to be lit is far away from any suitable roof area, such as when it is on the ground floor of a multi-storey building. While this may seem impossible to solve, it is in fact quite easy with the use of fibre optic cable.
Read the full article in ReNew 108
Dumping the halogens
Lance Turner looks at a LED retrofit that improved illumination with a huge reduction in energy use.
When we decided to take a look at a downlight retrofit to eliminate halogens from a home, we asked around the office if anyone had recently done this. Amazingly, no-one had, but one staff member did have an investment property that had halogen downlights and was slated for upgrading. So, together we sat down and worked out the best option for the upgrade.
READ MORE »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.
Read the full article in ReNew 111