Retrofit technologies

Absorption chillers perform the same basic function as conventional chillers – they generate the chilled water air conditioning systems need to provide cooling.

The major difference between absorption chillers and conventional models is that absorption chillers are driven by a heat source rather than an electrically powered compressor.

Some models burn natural gas or petroleum to provide heat, while others may use biogas, solar energy or waste heat (in the form of steam, hot water or exhaust gases) from another process such as hot water generation.

In addition to cooling, some models can also provide heating and hot water.

Blade servers perform the same function as standard computer servers, however, they do not contain any power, cooling or networking components. Instead, multiple servers are installed in a specially designed cabinet (known as a chassis) which provides these functions for all the servers it contains.

As a result, blade servers use less energy and generate less heat (which in turn can reduce air conditioning energy consumption) than standard rack mounted servers.

A building’s fabric is its structural elements: its walls, ceiling, windows, floors and doors.

How well the building fabric is insulated and sealed plays a major role in the energy efficiency of a building, as air conditioning systems may have to work harder if too much heat leaks into or out of the building. A well-sealed and insulated building fabric may even allow for a smaller air conditioning plant to be installed.

Minimising air leakage through the building fabric is essential for the operation of chilled beam systems.

Building management systems are central computerised systems used to manage a building’s operation.

Systems that may be connected to a building management system include heating, ventilation, air conditioning, lighting, security, fire services, plumbing and building access. A building management system can contribute to reductions in energy usage by automatically adjusting a building’s systems, turning them off when they are not required or optimising their running cycles.

Chilled beams are an alternative type of air conditioning system. They radiate coolness into a space in much the same way that a bar heater radiates warmth.

Chilled beams are installed at ceiling level. Pipes carrying cold water from the building’s chillers run through the beam, cooling it down and in turn cooling the air around the beam. This cool air falls to the occupied space.

Unlike traditional air conditioning systems, chilled beams don’t work by supplying air to the space – they only cool the air that is already in it. As a result, they need to be used in conjunction with a ventilation system (either natural or mechanical) to supply and exhaust air from the space.

Chilled ceilings work on the same principle, except rather than cooling an individual beam, the cold water pipes cool an entire ceiling area.

Cogeneration plants supply both power and thermal energy using a single fuel. They run on a single fuel source, such as natural gas or diesel.

For every unit of power generated, the plant also generates two units of heat. This heat is usually wasted as exhaust in a standard electricity generation plant. But in a cogeneration plant, the heat can be used to heat the building or to provide hot water.

Cogeneration systems can be set up to serve one building or multiple buildings. They also use less water to generate power than conventional electricity generation plants.

Cooling towers are heat rejection devices – they take the heat removed from a building by its air conditioning system and dissipate it outside. They do this by moving air across a stream of water: some of the water evaporates into the moving air, and this cools the rest of the water stream.

Cooling towers are an energy efficient means of rejecting heat from air conditioning systems, particularly in buildings requiring a cooling capacity of more than 700kWr and that operate for 5000 or more hours per year.

The water used in cooling towers needs to be treated, usually with chemical agents, to discourage corrosion and the growth of bacteria.

Proper commissioning, monitoring and maintenance will also ensure that cooling towers use as little water as possible. The water that flows through a cooling tower can be recycled by the system multiple times – the system needs to be set up and maintained to maximise this recycling.

All cooling towers in Victoria need to be registered with the Victorian Building Authority to help track potential sources of Legionnaires' disease.

Day lighting is the practice of arranging a building’s windows so that they allow in the maximum possible amount of natural light.

Day lighting has a number of advantages. Less artificial lighting is required in buildings where there is good day lighting and this in turn saves energy. Natural light is also thought by many experts to have a positive psychological effect on building occupants, as unlike artificial light it contains the full spectrum of light frequencies.

The major issue with day lighting is ensuring it reaches the interior space in diffuse (not direct) form. Direct sunlight can cause glare problems, which are a nuisance for building occupants. It can also introduce extra heat to the space, which the air conditioning system then needs to work harder to remove.

Devices such as light shelves (which reflect light into a space instead of allowing it to penetrate directly), window shades and blinds can be used to minimise these issues.

Flat panel computer monitors use less energy than traditional cathode ray tube (CRT) monitors. They also generate less heat than CRT monitors, which allows for energy savings as the air conditioning system needs to do less work to cool the space.

In addition to maximising the amount of natural light reaching a space, there are a range of options for making artificial lighting systems more efficient.

A trend in recent years has been to distinguish between ambient lighting and task lighting. Where once 100 per cent of lighting would have been provided by ceiling-level lights, many buildings are now opting for designs where ceiling-level or ambient lighting only provides 30 per cent of the light needed for a space. The remainder is provided by task lighting (such as desk lamps) which is positioned much closer to workers and can be turned on and off as required.

Energy efficient alternatives now exist for most forms of artificial lighting.

T5 light fluorescent tubes are smaller and more efficient than standard (T8) tubes, and are now being used in many commercial buildings. Compact fluorescent bulbs can replace standard incandescent bulbs.

Control systems also play a major part in lighting energy efficiency. Energy is wasted every time someone forgets to manually turn off a light. Automated systems which connect lights to motion and daylight sensors can negate this problem. The sensors can dim or switch off the lights when there is enough daylight entering the space, or when motion detectors don’t register any people in the space.

Motion sensors detect when a person is moving in a space.

They can be used in buildings to control various systems, such as turning lights or air conditioning off in areas where no movement is detected. This can result in significant energy savings, as the lights or air conditioning get turned off regardless of whether someone remembers to flick the switch or not.

Natural ventilation systems allow outside air to flow through a building without the use of mechanical aids such as fans. While a system can be as simple as a window that opens, most natural ventilation systems in commercial buildings are carefully designed to adjust to outside conditions.

Some buildings feature both natural and mechanical ventilation and change between the two systems as conditions outside change. These buildings are known as ‘mixed mode’ buildings.

A natural ventilation system can reduce a building’s energy usage by reducing air conditioning run time and the loads placed on the air conditioning system.

Issues to be aware of when considering a natural ventilation system include safety, security, outside noise and outside air pollutants. Natural ventilation may not be appropriate in an area with high levels of dust or exhaust fumes in the air, for example.

In a typical commercial building, air conditioning runs during business hours and is turned off overnight. Any excess heat left in the building from its operation during the day is removed when the air conditioning system is turned on again the next morning.

Night purge systems provide a low-energy solution for this issue. Rather than using mechanical air conditioning to remove the heat, a night purge system expels the heat from the building to the outside air throughout the night.

This means the air conditioning system needs to do less work to reach its temperature set point the next morning, and in turn uses less energy.

Solar energy use in commercial buildings falls into two main categories – electricity generation and water heating.

Photovoltaic cells generate electricity when exposed to sunlight and panels of them can be placed on the external surfaces of a building to supply power. Generating energy on site means the building won’t need to use as much mains power, reducing both energy bills and greenhouse emissions.

Solar hot water systems work in a similar manner – collectors are placed on the exterior of the building and use the sun’s energy to heat water which can then be used inside the building.

The most common issue encountered with solar energy systems is cost. They tend to be expensive to install, and in some cases the savings made over the system’s lifetime won’t be enough to recoup the initial investment. As with other options, solar energy systems require careful life cycle and cost-benefit analysis.

Trigeneration systems are very similar to cogeneration systems. They can supply power and heating just like a cogeneration system, and they can also provide cooling.

In a trigeneration system, some of the generated heat is used in conjunction with an absorption chiller to supply building air conditioning systems.

Like cogeneration systems, trigeneration systems can be set up to serve one building or multiple buildings. They also use less water to generate power than conventional electricity generation plants.

Traditionally, air conditioning system components such as fans and pumps have used constant speed drives (motors) – they operate at a fixed speed and can only be switched on or off.

Variable speed drives allow these components to modify the speed they operate at to better match the load that is being put on them. This can allow for significant energy savings, depending on the system. Variable speed drives also tend to require less maintenance as their ‘soft start’ capability reduces start up wear compared to fixed speed drives.

Variable speed drives aren’t necessarily a direct replacement for fixed speed drives though. System changes will probably be required to allow variable speed drives to be used and realise their full potential, as changing one or more drives from fixed to variable speed will have an effect on other system components and efficiencies.

Under the Water Efficiency Labelling and Standards scheme, all shower heads, toilets, urinals, clothes washers and dishwashers and some taps sold in Australia must now carry a label indicating their water efficiency.

These labels rate appliances on a scale of one to five stars, and replace the voluntary ‘AAAAA’ labelling scheme. The more stars, the more efficient a fitting is. Replacing old fittings with new, more efficient ones can result in significant water savings.

Some buildings incorporate wind turbines into their design to reduce the demand for mains electricity. The suitability and cost effectiveness of wind turbines will depend largely on the building’s location and typical local weather conditions.

As with solar energy systems, wind turbines can have the benefit of reducing the building’s reliance on mains electricity if implemented correctly.