A zero net energy office building is one which consumes no net energy. Its an office that uses very little energy, then has some form of renewable energy to generate all the power it requires.

With current off the shelf solar technology, presuming little or no shading, its possible to get around 100 kWh  of energy per year per square meter of solar panels at latitudes of around 40 degrees, more in sunny locations at lesser lattitude. For a single storey building, with a roof covered with solar panels, and little shading, keeping office energy consumption to 100 kWh/m2 is easy, and in fact I’ve audited quite a few small offices that are nothing special but only use in the order of 100 to 120 kWh/m2. But a grid connect solar system nowdays costs in the vicinity of  $700 to $1,000 per square meter, which is pretty  expensive, so there are very few zero net energy offices in existence.

Aggressive energy conservation and use of off the shelf technology (like skylights) can mean that office energy consumption is kept down to somewhere between 30 to 50 kWh/m2, meaning only half the roof needs to covered with solar panels, or allowing for some shading. For example our office uses only 30 kWh/m2/year, but is shaded in winter, we could make it energy neutral now just by covering around 2/3rds of the roof in solar panels.

So it is possible now, in 2009, to have a zero net energy office, but its not easily affordable, yet. And if your office is 3 storeys or higher, its becomes very hard to achieve no matter what your budget.

Technological advances however, are happening rapidly and I believe that by 2020 a zero net energy low-rise office may be affordable. And importantly this should be achievable by retrofitting an existing office building, with no need to especially construct a new building. Some of these technological changes are:

• The emergence of LED lighting. Assuming by 2020 we have LED lighting of around 200 lumens per watt. Allowing for some daylighting, and good use of task lighting, it may be possible to have annual lighting use less than 8 kWh/m2/year.
• Computer efficiency improvements. Assuming that with thin client architecture and high efficiency monitors by 2020 an office PC uses 15 watts, and that a 200 watt server can then serve 30 clients, computer energy use would be around 3 to 4 kWh/m2/year.
• There are many likely pathways for HVAC, which will depend on climate. A likely pathway for temperate climates is 100% fresh air HVAC systems, with air to air heat exchangers, but also using legacy internal ducting to allow high flow full economy cycles. Fans will be highly efficient, and heat pumps will have high efficiencies at a range of loading conditions, with the conditioning of air separated from ventilation to lower fan energy use. Couple this with light weight retrofit phase change materials (PCM) to provide thermal mass (eg plasterboard with encapsulated PCM), white roofs (where there are no solar panels), glazing treatments and new insulating membrane technologies to improve the thermal performance of the building. Seal the building well, and combine with good use of sensors and intelligent control all of which limits HVAC energy use to say 15 kWh/m2/year.
• Miscellaneous loads: high efficiency fridge at say 150 kWh/year; near zero standby loss hot water system; high efficiency multi function devices, totalling say 4 kWh/m2/year.

This will result in total office energy use of around 30 kWh/m2/year.

With aggressive energy conservation occupants should be able to to get down to say 15 to 20 kWh/m2/year.

Assume solar panel efficiency is more than double current efficiency and the installed price per watt of a grid connect system is one third of the current cost. This will provide 260 kWh/m2/year at a cost of say $500 per square meter.

A single story unshaded office where aggressive energy conservation is practiced will then need only 8% of its roof covered with solar panels, at a cost per square meter of building area of only $40.

A three storey half shaded office building would need most of its roof covered.

It should be possible to have a 7 storey building energy neutral if unshaded and the roof is covered with solar panels. Of course if additional solar panels can be added to walls it should be possible to get even taller energy neutral buildings.

By 2020 the net zero energy low-rise office building should be easily affordable, and in fact it may well be standard good financial practice to convert existing office buildings to energy neutral ones. So even building owners with no interest in acting to slow climate change will have energy neutral buildings. And most low rise office buildings then - whether they are 100, 50, or 1 year old -  could be energy neutral.

I say “should” and “may” because I still have some doubt as to whether a couple of the technologies that modify the thermal performance of a building –  particularly PCMs, and retrofit membrane’s that improve its insulation properties – will be affordable. But then again with focus a lot can change in 11 years, and as more of us demand better energy performance from our buildings I believe that this will spark the innovation needed to make zero net energy office buildings common place.

You can help make this a reality by acting now to make your building more efficient. Do what is affordable now. Then repeat regularly - technology is now advancing quickly. You’ll create the demand that will drive the innovation that will create the technology that will make energy neutral buildings common place.

Most commercial buildings in Australia have moved away from incandescent bulbs to compact fluorescents, which are much more energy efficient and last longer. The limitations of CFLs are slow warm up time, early failure if frequently switched, and high cost for dimmable CFLs. Additionally some speciality bulbs, such as chandelier bulbs, don’t have readily available CFL equivalents. But as CFLs are four or five times more efficient than incandescent in our energy audits we always try to build a strong case for switching to CFLs.

But incandescent may be getting a second life. Australia enacted the first legislation banning  sales of low efficiency lamps (incandescent) and the US followed. With a much larger market than ours this has sparked some innovation in the design of incandescent lamps.

Philips now has a incandescent that is 30% more efficient than a standard incandescent. Osram is shortly coming out with one 25% more efficient.

These sort of efficiency gains still leave CFLs as clearly the superior option, but as there is more research undertaken the incandescent could get even better yet.

If incandescent efficiency can be improved by 20% a year, it will take six or seven years to catch up with where CFLs are now. Which is a long time, unless there is an innovation that provides a quantum improvement in efficiency.

LED lights on the other hand are now getting close to CFL efficiency.

Its great to see all this lighting innovation happening, and hopefully we will soon see screw in and plug in bulbs that are more efficient than CFLs

Research recently undertaken by Siemens says that the lifecycle efficiency of LED lights is equal to that of compact fluorescents.

Measuring the lifecycle efficiency involves looking at the energy to manufacture and dispose of the product, in addition to the energy it uses whilst in operation.

The report was released by Osram, which is owned by Siemans, with the testing taking place by the Siemens Corporate Technology Centre for Eco Innovation, and reported on in the New York Times.

There aren’t many details yet though as to how the research was undertaken or the numbers behind the claims. For example, was the LED light used in the comparison of equivalent brightness to the CFL. 

But it does show that LEDs are getting closer to being the light of the future.

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.

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

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.

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.