Commissioning is a quality-assurance process designed to increase the likelihood that a newly constructed building will meet client expectations. Commissioning stretches over the entire design and construction process. It should ideally begin at the design phase, with selection of a commissioning provider who helps ensure that the building owners and designers’ intent is written into the project documentation.

The design and construction of ‘green’ buildings pose problems similar to those found in conventional building design. This compromises the intent of the design to achieve a high level of energy efficiency in its function. A good sustainable design will include systems that are “right-sized” (rather than the typically oversized mechanical systems) for the building. Over sizing equipment has become a standard design practice, because—due to design, installation, and/or operation errors, systems rarely function at their intended capacity. These errors occur because of the fragmentation between design, construction and operation, resulting from a general lack of a systems approach in the building process. Commissioning can facilitate improved integration and communication between these phases and can also ensure that right-sized systems function as intended and as specified.

If a building is not properly commissioned, it will not perform according to its design intent and will therefore have a poor energy rating. A common reason for inadequate commissioning is the tendency for projects to go over time and budget and for the contractors to drastically pull back on resources to get started on new projects. For this reason, it is widely recognised that engagement in independent commissioning is best practice, as it is carried out objectively without any conflict of interest.

The cutting of costs and resources at the initial commissioning stage will end up costing the facility more money in the long run, as extensive maintenance issues will ensue. Also, the cost of retrofitting is always more financially intensive than implementation as part of the original build.

In conclusion, it is recommended to allow sufficient investment capital to employ independent commissioning at the construction stage, as it will save countless amounts of energy, money and time overall.

At the recent All Energy expo in Melbourne (early October) I came across the Coolerado cooler, distributed in Australia by Clear Solar. This is an ingenious, simple air cooler based on a combination of evaporative cooling and plate heat exchangers to deliver cooler air than is possible with conventional evaporative cooling but without the use of a refrigerant. It therefore has the energy efficiency of evaporative cooling, but with the performance of refrigerative cooling in dryer climates.

For a detailed explanation of how it works visit the Coolerado website. Below is a quick technical summary using the psychometric chart. You may prefer the Coolerado website if you don’t understand the properties of air at different moisture levels as displayed in the psychometric chart.

The unit splits air into two streams, either side of a plate heat exchanger. Moisture is added to one stream – the working stream. Its temperature drops using the evaporative process. This then sensibly cools the air on the other dry side of the plate, the process stream. Some of the process air is then split off and made into more working air. Moisture is added to this too. This then cools further, and through the plate heat exchanger it then further sensibly cools the process stream. By doing this multiple times the resultant process air exits at near the dew point temperature of the air. And around half of the total air going through the system ends up as useful process air. 

Psychometric chart showing how the Coolerado cools air. Click on chart to enlarge it.

The chart above shows the principal of operation marked on it assuming the process stream is split up 3 times and perfect evaporative cooling (ie to the wet bulb temperature). In the Coolarado 13 stages are used to get air down to near dry bulb temperature.

As you can see in the my chart below – for 35 degree air at 20% humidity (at sea level) with a conventional evaporative cooler we can get the temperature down to near the wet bulb temperature of 19 degrees, but at 100% relative humidity. With the Coolerado we can get the temperature close to the dew point of 9 degrees, or if we are only cooling to 19 degrees do so with a relative humidity of around 55%, which is perfectly comfortable.

A variable speed fan in the unit controls the air flow and thus the exit temperature and relative humidity of the air it supplies.

For hot dry climates the Coolarado can completely substitute conventional refrigerative air conditioning. And in more humid climates it extends the usefulness of evaporative cooling.

The Coolarado website also has a chart based on historical weather data for hundreds of sites world wide, showing its applicability, including several Australian cities. Or, if you know your local weather and can use a psychometric chart, its possible to figure out its suitability. In Australia for example the Coolarado is well suited for use in Adelaide.

I’m not sure of the maintenance regime for the heat transfer plates and cooling pads - presumably similar to those of a conventional evaporative cooler, and obviously the system whilst saving energy does use water.

In addition to the energy savings another advantage of the Coolarado is it doesn’t have any refrigerants in it, so you don’t need to worry about the global warming potential of any leaked refrigerant. And the only moving part is its fan, which is a high efficiency direct drive unit, reducing mechanical maintenance requirements. 

Innovations such as this are going to help enable a low carbon economy, and as prices drop will start drive it.

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.

A recent Sustainability Assessment job took me to the corner of Victoria to the town of Mildura.  A town of around 30,000 people, Mildura borders NSW on the Murray River.  In summer the maximum temperature averages over 30 degrees and naturally there is a high demand for air conditioning and water.  Conventional air conditioning systems contribute substantially to greenhouse gas emissions through the consumption of electricity (predominantly generated from burning coal) and water, for cooling towers and evaporative cooling systems.

The idea of solar air conditioning was mentioned, which sounds great, but does it exist and is it practical?

After doing some reading, yes, solar air conditioning does exist, but despite Australia’s sunny climate there does not seem to be much awareness, knowledge and skills in this area.  So how does it work and why isn’t it widespread in Australia?

From my understanding, there are essentially two categories of solar air conditioning.

1. Ventilation based systems that use photovoltaic power to power fans via heat exchangers or  through desiccant filters  that remove moisture from the air and improve thermal comfort and;
2. Solar thermal systems that harness the sun’s thermal energy (heat) to drive the cooling system.

Photovoltaic powered ventilation based systems are very much dependent on climatic conditions and building design.  These kinds of systems take advantage of fresh air intake to a building and remove unwanted levels of humidity, improving thermal comfort and reducing cooling (heating) requirements.  These kinds of systems have generally been adopted for smaller-scale applications, including the residential market.  This form of solar cooling does not actively cool the air supplied to a building space and is therefore limited to the right environmental conditions to work effectively.

Solar active thermal systems are expensive, more complex and generally too big for smaller applications such as residential housing.  The common system uses an absorption chiller, which compared to a conventional compressor based chiller, does not use electricity to power the system, but instead uses solar collectors to heat water that is then used to produce chilled water through interaction with a refrigerant or desiccant solution.  Such systems can also be used to generate hot water for heating requirements and general hot water needs.  Such systems make good sense where ample sunlight is available and for large-scale or remote applications.

Solar Absorption Chiller

Source: http://greensource.construction.com/products/images/0704_11.jpg

Australia has a high demand for air conditioning and therefore a high demand for electrical energy through use of conventional compressor driven coolers.  The high demand of air conditioning in summer puts a huge strain on the electricity network and contributes substantially to global warming through burning fossil fuels and use of refrigerants (which have an extremely high global warming potential) in air conditioning systems.

Why then is solar air conditioning not widespread, at least for large-scale applications?  The main barriers to solar cooling include:

• The high cost of solar collectors
• Lack of skills in solar cooling technology and increased complexity
• Abundant, cheap energy with no environmental cost
• Minimum incentive to reduce peak power consumption

Overcoming these barriers really requires government intervention through subsidies, research funding, introduction of interval metering to pass on peak costs to electricity users and introducing a carbon tax or trading scheme to factor in an environmental cost on energy.

The Australian National University (ANU) is currently developing a hybrid solar air conditioning that is aimed at replacing conventional residential air conditioners.  The design employs a solar thermal powered compressor that can provide cooling and heating just like a reverse cycle air conditioner. The break-through is the ability to generate cooling like an absorption chiller, but without the need for a bulky and complex system.

The system employs what is called an ‘ejector pump’, which is capable of generating low pressure (necessary for refrigeration) and is low cost to manufacture.  A refrigerant is pumped to high pressure and then heated by solar collectors (the same used for solar hot water systems).  The ejector creates a drop in pressure (the cooling effect) by converting the energy in the refrigerant into kinetic (movement) energy by firing fluid into the ejector at supersonic speed.

Ejector Pump

Source: http://solar-thermal.anu.edu.au/low_temp/solarac/image071.jpg

Amazingly, the only electricity needed to power the ejector unit is 150 watts or 1/10 the power minimum of a conventional air conditioner.  This is set to revolutionise air conditioning as we know it and the project is moving closer to commercial viability.  With the onset of a carbon trading scheme, the rollout of smart meters beginning, energy rates set to increase and summers increasing in temperature, the economic case for this upcoming technology holds great promise.   I certainly can’t wait for this ‘cool’ technology!

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

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

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.