Carbon Conservation & Energy Efficiency


Bruce Rowse & Team

Archive for the ‘Energy efficiency’ Category

Voltage reduction could save 15 million tonnes of greenhouse gas – part 2

Monday, July 13th, 2009

A few months ago I wrote a blog posting about how tighter regulation of electricity supply voltages could save Australia 15 million tonnes of greenhouse gas a year.

However a comment on that posting suggested that voltage reduction may not result in any useful savings.

Below I report on the results of an experiment we undertook to identify how much power can be saved, if any, by operating equipment at a lower voltage.

We measured a variety of single phase loads at different voltages. A variable transformer was used to vary the voltage. A German made Power Tech plus plug in power meter was used to measure voltage, current, power and power factor at the different loads. Loads experimented with included typical single phase lights, computer equipment and a fan.

experimental set up to measure power draw at different voltages of a range of single phase loads

experimental set up to measure power draw at different voltages of a range of single phase loads

The experimental set up is shown above. Below is a graph showing the results of the testing.

graph of power draw vs voltage for a variety of single phase loads

graph of power draw vs voltage for a variety of single phase loads

This graph clearly shows that for common lighting loads power consumption decreases with decreased voltage

  • Incandescent lamp (resistive load)
  • T8 fluorescent (inductive load)
  • T5 fluorescent (electronic ballast)

The reduction in power consumption with the T5 fluorescent (with an electronic ballast) was unexpected.

The fan, with a single phase (shaded pole?) motor, also used less power with lower voltage, interestingly the power factor improved as voltage was lowered, with the power factor the highest at 220 volts.

The PC computer and monitor both showed lowest power consumption at 230 and 240 volts, but power consumption generally did not decrease with voltage. Power factor improved a little at lower voltages.

This experiment shows that for a variety of loads power consumption is in fact less at lower voltage.

For heating or cooling loads equipment may need to run longer when at lowered voltage to reduce the same amount of heating or cooling, with no net energy savings.

Three phase synchronous motors are unlikely to use any more or less power (a theoretical assertion, we don’t have the equipment to test), having the motors run at 230 volts rather than 240 or 250 volts however is unlikely to cause motor damage due to excess current as the voltage difference is only small.

But with lighting and many single phase motors power consumption drops with lowered voltage.

My back of the envelope calculations still come up with a saving of around 15 million tonnes of greenhouse gas if voltages were closer to the 230 volt standard rather than being at 240 to 250 volts.

If high voltage drops in distribution were a problem additional network infrastructure could be used to deliver a more consistent voltage across the network. 2009 is the year of the “smart grid.” A smart grid could mean multitap transformers that can be changed on the fly to deliver a more consistent 230 volts across the whole electrical network.

LED lighting – the way of the future

Saturday, July 11th, 2009

If LED lighting continues to develop as fast as it has over the last five years, within ten years it may well be the main form of lighting in use across the world. And lighting in new buildings may look radically different to what it does now.

The major advantage of LEDs is that they are a directional light source. Most other artificial light sources on the market radiate light in all directions. Incandescent light bulbs, compact fluorescent lamps, fluorescent lamps and high intensity discharge lamps such as metal halide all radiate light in all directions.

For example in most fluorescent office light fittings typically only 60% of the light produced by the fluorescent tube is emitted as useful light. A great deal of the light is lost because it goes  upwards or sideways rather than down. Using a reflector may increase the amount of useful light provided up to 80%. But even the most efficient fluorescent light fittings on the market rarely have a light output ratio of above 80%.

LED lights on the other hand produce all their light in a single direction. Light fitting designers can take advantage of this to efficiently direct light exactly where its needed, with very little lost or wasted light.

Go into a progressive hardware or electrical store and you can already see a variety of LED lights being sold.

Fluorescent lamps are the most commonly used lamp in the world. LEDs however are not yet competitive with fluorescents for three main reasons:

  1. Energy efficiency is similar but not yet better. A high performance fluorescent tube will produce 100 lumens per watt. Put it in an energy efficient fitting, with a light output ratio of 80%, and the overall lighting efficiency is 80 useful lumens per watt of electricity. The best white LEDs on the market (that we are aware of) produce 75 to 80 lumens per watt. This is good, but not yet better than, fluorescent.
  2. Reliability. Unlike fluorescent tubes, which are generally reliable no matter who makes them, LEDs are often unrealiable. We have purchased LEDs from many different manufacturers, and over half have failed within the first year of use.
  3. Price. LEDs are still expensive.

This, however, is changing. Energy efficiency is improving, the major lighting manufacturers are increasing their focus on LEDs, and prices are dropping.

Energy efficiency of LEDs has increased markedly in recent years, in 2006 the best LEDs were approaching 60 lumens per watt, by the end of 2008 they were up to 77 lumens per watt. 

Reliability. The three main global light manufacturers – Osram, Philips and Sylvania – are all now selling LED lights. As major global brands they are unlikely to risk the cost and reputational damage of supplying unreliable products. As LED products become more main stream we can expect reliability to improve.

Costs are now starting to decrease as well. Whilst it is difficult to purchase a LED fluorescent substitute light for less than $80, only two years ago the price was $100.

When LED lights are achieving energy efficiencies in excess of 120 lumens per watt, lamp costs of less than $2 a watt, and low failure rates (less than say 1%) lighting as we now know it will be superseded. It will be possible to retrofit LEDs and cut lighting energy use by 50% or more in almost any building. New buildings, with lighting designs built around LEDs, may well be providing office – standard illumination for 2 watts of electricity use per square meter or less (current best practice is around 5 watts per square meter).

These new lights may look very different. Light fittings may become panels with hundreds of LEDs on them. Or ceilings may end up with stripes of LEDs across the ceiling. Or ceilings will end up with sockets into which panels of LEDs can be plugged in, so that its easy to move LEDs around in response to the lighting needs of a room (more above a desk, less in the corridors).

If control and sensing technologies can become sufficiently low cost buildings may well be set up to provide lighting whose intensity varies with occupancy and usage.

The rapid development of LEDs is exciting. It gives me hope that, when it comes to lighting, humanity will be able to greatly reduce its carbon footprint in the not too distant future.

Measurement number one for Wesfarmers in reducing their carbon emissions

Friday, July 10th, 2009

Earlier today I interviewed Cameron Schuster, Sustainability Manager of Wesfarmers Limited. Wesfarmers owns Coles, Bunnings, Kmart, Officeworks, Target and a large number of other businesses.

Cameron’s says the following three things are critical to any organisation wishing to cut their carbon emissions.

  1. Measure. Wesfarmers is putting in an internet based measurement and reporting system in place. This will provide store managers and others easy access to information about how they are performing.
  2. Win senior management commitment
  3. Entrust and empower people throughout the organisation to initiate activities to reduce their carbon emissions. Lots of small initiatives can add up to large carbon savings.

As with my interview with Toyota the theme of continuous improvement comes through in this interview. Wesfarmer’s carbon reduction strategy also has a strong emphasis on energy efficiency.

Click here to go to the interview with Cameron, or here to view Wesfarmer’s most recent sustainability report.

How to cool for free

Wednesday, July 8th, 2009

Free cooling takes advantage of cold outside air to cool a warm building. Strictly speaking “free cooling” isn’t free as energy is used by fans to move air from inside to outside. Free cooling is beneficial for any building where there are significant heat loads inside.

Server rooms and data centres can benefit enormously from free cooling, and in fact is the main reason why Google’s major server rooms are located in cold climates. It’s also beneficial for large office buildings where internal heat loads from people, lighting and office equipment mean that the core of the building is warm, even though it may cold outside. Buildings with glazing facing the sun can often benefit due to the heat load from solar heat gain. Its been our experience that in temperate climate’s such as Melbourne even small buildings can benefit from free cooling.

To cool for “free” your building’s air handing system needs to have an “economy cycle” installed. An economy cycle has a large fresh air intake, and also a large spill or relief air outlet. Rather than recirculating most of the air in the building as is normally done, with an economy cycle the air is not recirculated, it simply comes in, provides cooling, then is vented out again.

If an economy cycle is not operating, not only is fan energy used to recirculate the air, but energy is used to provide cold refrigerant or chilled water to coils that cool the air that is being recirculated.

Your building’s air handling system may already have an economy cycle fitted. Its worth while finding out if it does, and if so, if its operating properly. Common problems that limit the effective use of an economy cycle are:

The actuator motor in this photo has come off its shaft and is hanging uselessly from its cord

The actuator motor in this photo has come off its shaft and is hanging uselessly from its cord

  • Very tight temperature settings with a narrow deadband (see an early blog post on what is a comfortable office tempature for more on dead-bands)
  • Faulty actuators. These may not be fully opening or closing the supply air, return air and spill air dampers.
  • Faulty dampers. Dampers may be broken, rusted in position or seized.
  • Controls that can’t enable an economy cycle, even though all the hardware is in place.
  • Out of calibration sensors, that don’t call for an economy cycle when needed.
  • The supply air vent is located in a warm plant room, so that an economy cycle won’t work even though its cold outside.

On the other hand your system may not be set up for an economy cycle. This is the case with many packaged air conditioners. In this case to get free cooling an economy cycle may have to be retrofitted. This involves increasing the sizes of the supply and spill (relief) air dampers and ducts as needed, the fitting of motorised dampers, and upgrading of the controls.

Diagram showing how a simple free cooling system can be fitted into a server room currently cooled by split system air conditioners. A controller will close dampers, shut down the fan and start the split system if outside air can't keep the room cool

Diagram showing how a simple

Small server rooms cooled by split system air conditioners can often be easily set up for free cooling by setting up the necessary duct work. The more equipment in the server room the bigger the savings.

In cold and temperate climates free cooling should always be considered as an energy saving measure.

During our energy audits re will often undertake a detailed system inspection and data logging to verify the correct operation of existing economy cycles, or undertake a cost-benefit analysis of installing an economy cycle if not yet installed.

How efficient are centralised steam systems?

Friday, July 3rd, 2009

We have recently been working on a site with a centralised steam system. It has two natural gas fired boilers supplying steam to a number of plant rooms, with the steam used to generate domestic hot water and heating hot water amongst other things. So how efficient is this system? And are there alternatives to steam that use less energy?

The short answer is that the steam system is very inefficient. It could be replaced with a decentralised system using a combination of hot water boilers and, where process steam is needed, small steam boilers. This would halve energy use.

Centralised steam systems have losses designed into them that cannot be avoided. Firstly the boiler blow down results in energy wastage. Then, because of the high pipe temperatures, any heat losses from uninsulated pipe is higher than it would be if the temperature was lower. Failed steam traps waste energy by not using the steam before it turns to condensate. And leaks and steam vents waste valuable condensate. Finally because still steam will eventually condense and needs to be taken away by a steam trap then reheated the standby losses are high. All these losses add up to large inefficiencies.

Steam is a old technology, and its use should be limited to only where absolutely necessary. Using steam to generate hot water is very inefficient. Much more efficient would be to use a high efficiency condensing flue hot water boiler, a direct exchange boiler, which will use half the energy to generate the same benefit. Heat pumps could also be considered if a water temperature of no more than 60 degrees Celcius was required.