Author: Ahmad Fraij

LED lights are efficient type and they consume on average half the energy of the fluorescent lights and fraction of the incandescent and halogen lights. Also, LED Lights have longer lifespan and therefore, reduce the rates of replacing the faulty lights, which lead to savings in the materials and maintenance costs as well. LED Lights are safer for disposal because unlike fluorescent lights, they don’t have mercury toxicity.

First thing to consider when you decide to replace your old lights with LED type is that you should apply for a government rebate. Most of the Australian States have rebate scheme for LED lights replacement such as Victorian Energy Upgrade scheme in Victoria. If you decide to hire a specialist like us to supply and install the LED lights for you, then make sure they are approved installer by the government rebate scheme so you can get the rebate. If you hire us to do the work for you, then our partner will complete the paperwork for you to get you the government rebate.

You should also consider replacing the whole light fitting instead of replacing only the light tubes and bulbs for the following reasons:

  • Fitting may be broken, yellowed or also tough to remove diffuser due to age.
  • Lamp holders in old fittings may be corroded and may not accept the new LED Tube.
  • If the fitting fails at any stage now or in the future, you will need to upgrade the fitting at some point.
  • You need to use a quality product, as you have one chance to claim your subsidy from the government.
  • New fitting, aesthetically better look with all new internals (i.e. chip, driver, diffuser…etc).
  • All old fittings are recycled correctly.
  • More energy savings as lumens per watt are great in a fitting replacement.
  • More options such as Tri-Colour, wattage control (on some fittings)…etc.

 

Replacing the old lights with new LED lights gives you also a chance to reduce the number of the lights fittings or their lumens if the rooms are originally over lighted compared to the required light levels in the Australia Standard AS/NZS1680. This means more energy savings and more reduction in the CO2 emissions. This can be done by selecting the new LED lights output (lumen) based on the room size and the elevation of the lights above the work stations to meet the light level and recommendations stipulated in the Australian Standard AS/NZS1680. You should note that if the building operates over the night then you should take this into account when you select the required lights output.

For a free quote to replace your old lights with LED lights, please don’t hesitate to contact us.

Most of the light commercial buildings have packaged air conditioning units or ducted split air conditioning units. These units mostly fall in the capacity range of 15 kW to 90 kW and usually they are reverse cycle heat pumps to provide cooling in summer and heating in winter. When I drive around the suburb I live in Melbourne, I find numerous light commercial buildings that have either packaged or ducted split air conditioning units and most probably these units are as old as the buildings themselves and never been inspected for energy efficiency. This is in one suburb only so imagine how many light commercial buildings we have in Melbourne metropolitan or even in all Victoria. If you do the math you will find that we can save substantial energy by replacing the old inefficient air conditioning units in these small buildings with new high efficiency type.

These light commercial buildings are usually rented and the tenants don’t have the authority to approve the replacement of these units and also they don’t want to pay for the cost of the replacement. Likewise, the landlord is not welling to replace these units because they don’t pay the energy bills and the tenant pays for that. Therefore, it is lost between the landlord and the tenants and they keep run these units even if it is not efficient and waste a lot of energy.

I see some companies of LED lights and solar PV systems approach these buildings for replacing their old lights or install a solar PV system for them but I have never seen a company approach these buildings to inspect the air conditioning units and offer replacing them with higher efficiency units even though there is a government rebate scheme for such replacement in some states such as Victorian Energy Upgrade Project in Victoria.

I don’t know who to blame here? Is it the air conditioning contractors and maintenance companies, the energy consultants like us or the government for not advertising for their rebate schemes for the air conditioning units replacement?

The new high efficiency air conditioning units for these light commercial buildings come with variable speed compressors and also with variable speed supply fans, which make it very efficient. The manufacturers claim that these high efficiency units can save up to 37% in energy consumption compared with the old inefficient units. For example for a unit of 35 kW cooling/heating capacity, this equals to around 5,000 kWh energy saving and around $1,000 cost savings per year per unit. This also will result of 5.4 Tonnes CO2 avoidance of greenhouse gases emissions per year. These savings only from one unit but imagine how many units each building have and how many small buildings we have then this let us think about it seriously and how to get these old air conditioning units replaced.

In our opinion, the government has the main role to make this happens by increasing the rebates and incentives for the replacement of the old air conditioning units to encourage the landlord/tenant to replace these old units and also they should advertise about these rebates to make the landlord/tenants and the air conditioning maintenance companies aware of these rebates. The air conditioning maintenance companies have also an important role in convincing the landlord/tenant to replace the old units with new high efficiency units. Finally, the energy consultants like us should also reach out to the building owners to inform them about these rebate schemes and how replacing the old unit with new high efficiency unit will save them money and in the same time help protecting the environment for the coming generations.

For a comprehensive inspection and review of your air conditioning system, don’t hesitate to contact us.

I was reading the other day an article in AIRAH Ecolibrium Magazine (December Issue) about building a district cooling plant for the University of Queensland Gatton and it was great system that provides chilled water to the university campus in efficient way. This article let me wonder whether we can apply the district cooling and heating concept (i.e. District Energy) in a large scale here in Australia and provide chilled and hot water as a service. This let me to think more and I came to the following discussion points:

  • The district cooling plant usually uses water cooled chillers, which are more efficient than the air cooled chillers. However, most of the high rise buildings in the Australian capital cities uses also water cooled chillers and not air cooled chillers due to the high cooling capacity required. Have a look for example, on the Melbourne CBD buildings in Google Earth and you can see that most of the buildings have cooling towers on the roof. Further, the district cooling plant requires a fair area of land to be constructed on specially if it has thermal storage tanks, which is hardly available in the CBD of the major cities and if it is available, it would be more feasible to build a tower than a district energy plant. This let me think that district energy plant is not suitable for the cities CBD unless you are building a number of buildings next to each other in one time, then you can build an energy plant to provide chilled and hot water to these buildings.

 

  • This let me think about what if we implement district cooling and heating to the suburbs of the major cities. It is easier to find a land in the suburbs to build the district energy plant but not all the people in the suburbs will buy chilled water and hot water. The weather in Australia is not that extreme and many people use for example, ceiling or pedestal fans in summer instead of air conditioning. This led me to think that this concept will not be financially viable in the suburbs. I had previous experience working in district cooling field in the Gulf Countries (in the Middle East) and the weather in these countries is very extreme where the people can’t live without air conditioning and need cooling day and night and that is why the district cooling concept is financially viable in such countries.

 

  • Laydown the chilled and hot water piping network under the ground to connect it to the existing buildings and houses will not be an easy task. It requires high level of coordination with the other existing services such as sewage, natural gas, water supply, communications…etc, which make it very expensive and time consuming.

 

  • The district cooling plant consumes a large amount of water because it loses water through evaporation in the cooling towers, which imposes stress on our water resources unless we use treated sewage effluent water.

Based on the above discussion, we conclude in our opinion that district energy is suitable for the following building types in Australia:

  • University Campuses in which multiple buildings require cooling and heating most of the time of the year.
  • Hospital Campuses similar to the university campuses above.
  • New large developments located in extreme weather such as Queensland and Northern Territory and have the underground networks for the chilled and hot water included in the design stage.

As a building/facility manager you have the responsibility to keep the systems and equipment in the building running smoothly and with minimum breakdown time. However, with the current global warming and climate change, you have also the responsibility to reduce the energy consumption of these systems as much as you can to protect the environment and preserve it to the coming generation. Everybody should have this responsibility and save energy as much as they can.

Not always the energy conservation measures require high capital cost or need an expert to implement them to save energy. There are many measures that can be implemented by only changing the settings in the BMS (Building Management System) or with simple ways that are in the capabilities of the Building Manager and/or the maintenance staff.

Below are some simple recommendations and tips that can help the Building Manager saves energy in simple and non-costly ways:

  • If the operating schedules of the HVAC (Heating, Ventilation and Air Conditioning) system in the BMS start the system more than one hour before the occupancy time, then reprogram it to one hour only or less. Likewise, if these schedules keep the HVAC system run after the occupancy time, then reprogram it to stop at the end of the occupancy time. By this way, you reduce the running time of the HVAC system and save energy. You can do the same thing if you have programmable thermostats instead of BMS.
  • If the temperature setpoint of the air conditioning system in the cooling mode is less than 24°C, then reset it between 24 to 26°C. If the setpoint in the heating mode is more than 20°C, then reset it between 18 to 20°C. Remember that by adjusting the temperature setpoint by 1°C, you change the energy consumption of the air conditioning unit typically by around 10%. See our article How Much Can you Save Energy by Adjusting your Thermostat by 1°C for more details. If you have one temperature setpoint with a dead band, then widen the dead band to 3°C. All these settings can be done through the monitoring computer of the BMS.
  • Have a look to the insulation of the chilled water and the hot water pipes and fix any damages. This does not require expert and can be done by the available maintenance staff in the building.
  • Clean the air conditioning and refrigeration coils regularly to improve the heat transfer and then their efficiency.
  • Lower the domestic water heater storage temperature to 60°C if it is more and this can be done through the water heater controller or through the BMS if it is interfaced with it.
  • While we usually recommend replacing the whole old light fixtures with new LED type, still the building manager and the maintenance staff can replace only the light tubes and the bulbs with new LED type to save energy, which won’t cost much to replace them.
  • Program the computers in the building to go into standby mode after 20 minutes of inactivity.
  • Install plug timers to the tea/coffee boiler, printers and copiers to turn them off during unoccupied time and during weekends.
  • Educate the building occupants about energy saving and how to use the systems and equipment efficiently to cut any energy wastage. Changing occupants’ behavior can save substantial amount of energy with zero cost.
  • Improve cleaners switching off routine.

 

For a detailed energy audit that can provide you with comprehensive recommendations, please contact us.

We discussed earlier how to maximize the energy saving by relacing an old chiller in retrofit projects but in the these projects you are stuck with the existing chilled water system and the limited spaces in the building and you need to find ways to improve the existing system with the constraints available on site. On contrary, for new projects, you have the privilege to design and specify efficient chiller system from early stages and you can compare and analyse different system options and select the one that has the best life cycle cost.

In this article we discuss some ways to improve the efficiency of the chiller system during the design stage, however, the designer should analyse the designed system in a holistic approach to make sure they select the best system that meets the project budget and achieve the best possible efficiency.

  • Chiller:

As we mentioned earlier in our previous article, the chiller should be high efficiency variable speed chiller with magnetic bearing compressors are the best. Air cooled chillers should have EC fans for the condenser and should be equipped with adiabatic system to improve their efficiency further.

  • Chiller Leaving Chilled Water Temperature:

The chiller efficiency depends on the compressor lift, which is the difference between the suction and discharge pressures. The smaller the difference in pressures the higher the efficiency of the chiller. The pressure is proportional to the temperature and therefore, the compressor lift and then the chiller efficiency depends on the leaving chilled water temperature and the leaving condenser water temperatures for the water cooled chillers or the leaving air temperature for the air cooled chillers.

Based on the above, we can see that increasing the leaving chilled water temperature from the chiller will improve its efficiency. As a rule of thumb, for every 1°C increase in leaving chilled water temperature, there is 3% reduction in chiller energy consumption. Therefore, always design your system with high leaving chilled water temperature. Note that increasing the chilled water temperature leads to bigger coils in the AHU’s and FCU’s and therefore, the designer should carry out life cycle cost analysis to select the optimum system.

The designer should also consider selecting chilled beams or displacement diffusers for the chilled water system because these types of systems require higher chilled water supply temperature that can reach 16°C. This high chilled water temperature allows you to select smaller chillers and in the same time improve the chiller efficiency.

  • Reducing Pumps Flow Rate:

Most of the engineers design the chiller system at 5°C delta T on both the chilled water side and also on the condenser side if the chiller is water cooled. This is the old way to design the system but due to the need for energy efficiency, we need to increase delta T to 8 – 10°C to reduce the flow rate so we can select smaller pumps and save in the pumping energy. Further, reducing the condenser water flow rate for the water cooled chillers, will leads to smaller cooling tower and smaller tower fan, which also reduce the energy consumption further. Not to forget to mention that reducing the water flow rates leads to select smaller pipes, which reduces the capital cost of the project.

  • Water Cooled Chillers Connection Configuration:

We still see in most of the projects the water cooled chillers connection is parallel, while there is another configuration that makes these chillers more efficient specially for the large capacity chillers.

Series counter-flow chillers configuration as shown in the figure below reduces the chillers lift and improves their efficiency. You can see from the figure below that the chiller that has lower leaving chiller water temperature has also the lower leaving condenser water temperature and vis versa. This configuration makes both chillers see approximately the same smaller lift (26°C) than seeing the bigger lift (31°C) if they are both connected in parallel. Chiller manufacturers claim that this configuration can improve the chiller efficiency by up to 13%.

  • Using Variable Speed Drives (VSD):

Motor energy consumption is proportional to the cube of the flow rate and therefore, reducing the water or air flow rate will reduce the energy consumption of pumps and fans drastically. Thus, the followings should be specified with VSD:

  • Chilled Water Pumps with emphasis on variable primary flow configuration, which saves on the initial and running costs.
  • Condenser Water Pumps
  • Cooling Tower Fans
  • Air Handling Units Fans
  • Using Pressure Independent Control Valves (PICV):

Using pressure independent control valve for the air terminal units such as FCU’s and AHU’s is much better than using the traditional combination of the 2-way control valve and balancing valve. The 2-way control valve change the flow rate supplied to the terminal unit based on the pressure difference between its ports. This means that many times this 2-way valve will allow more water flowrate to the terminal unit than what is required. This overflow reduces the return chilled water temperature to the chiller and causes what we call it low delta T syndrome. This reduces the chiller efficiency and leads to more chillers to run, which increase the chillers energy consumption and reduce the system efficiency. Further, this overflow makes the pumps run at higher speed to meet the required overflow, which also increases the pumps energy consumption.

On contrary, PICV maintains the required flow rate to the terminal units regardless what is the pressure difference between the two ports. Therefore, it eliminates the overflow to happen and make the system more efficient.

  • Thermal Storage Tanks:

Thermal storage tanks whether it is chilled water, ice or phase change material (PCM) can be used to shift the electricity demand from the peak time to other times to reduce the peak demand charges. However, these tanks occupy big area in the building and not always it is possible to accommodate them. The largest tank is the chilled water storage tank and the ice tank requires around 20% of the volume of the chilled water tank for the same thermal capacity, while the phase change material tank requires 50% of the volume.

The chilled water thermal storage tank is the easiest option to include in the design but because of its large volume, it is not always practical to include it.

The ice conductivity is low and requires low operating temperatures, which reduces the chiller efficiency and therefore, can be used for demand shifting but for energy efficiency, a more detailed analysis should be done to make sure that operating the chillers at low ambient temperature during the night for example will outperform the reduction in efficiency due to the low chilled water temperatures.

The most common material used for PCM tanks is Eutictics and this material has freezing point of around 8.3°C, which make it the best option to choose for chilled water systems to save energy, however, the size of the tanks still a challenge to include it in the building.

  • Controls:

The building management system (BMS) should be designed and specified well and should include energy efficiency control strategies to make the chiller system operation more efficient. Below are examples of energy efficiency control strategies that should be included in the BMS:

  • Chilled Water Temperature Setpoint Reset. Note that this strategy conflicts with the variable speed chilled water pumping strategy and therefore, it is more suitable for constant flow systems and for variable primary flow systems the precedence should be for the variable speed pumping and after the flow is at minimum, then the chilled water temperature setpoint reset should apply.
  • Condenser Water Temperature Setpoint Reset.
  • Optimum Start/Stop
  • Demand Limiting

Further, the designer should specify Chiller Plant Optimization Controller, which is a controller dedicated only for the chiller plant (chillers, cooling towers, pumps and valves) and has algorithms to optimize the planet water temperatures and flows to make sure the plant equipment operate at their maximum efficiency.

For an energy efficiency design review for your chiller system and other building services design to improve it and make it more efficient, then please contact us.