CUTTING ENERGY USE INTELLIGENT CONTROLS
Improving the effi ciency of chiller compressors
Within the cooling system, the chiller compressors are the largest energy users, consuming up to 70% of the total energy within the system. Smartcool Systems claims its intelligent compressor optimisation strategy can cut energy use of chillers with advanced BMS control by 10 to 15% (kWh). Base demand is also reduced by an average of 10% (kW), providing dramatic cost savings in areas with heavy peak demand charges.
The Smartcool solution can be retrofi tted between the compressor and the primary controller. Alternatively, in a scenario involving a chiller and building management system (BMS), an indirect interface provided by the chiller manufacturer can be used to give a higher level of interface.
distribution systems. The electromechanical and electronic
control of a quarter of a century ago are a long way from the ‘space age’ digital control of the 21st century. Dedicated microprocessors oversee ‘intelligent’ self-tuning control mechanisms, with opportunities for unprecedented monitoring and automated fault detection. And, importantly for a sector that must
deliver unfailing service to its customers, the microprocessors also oversee the prediction – and so prevention – of faults that have not yet arisen. This same sensing and control technology may be adapted and augmented to create
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Smartcool continuously collects data on the operating profi le of the equipment, learning how the existing control system interprets demand, and how the plant is run to accommodate that demand. Using this information, Smartcool intelligently varies the compressor capacity, dynamically shedding load when it is not needed to reach the cooling requirements. The variation in capacity is constantly adjusted to suit the changing load conditions, maximizing the amount of time the compressor operates at its highest rated effi ciency.
It has worked with a number of hotel chains around the world to improve the energy effi ciency of their chillers.
Smartcool installs its retrofi t solutions and conducts an initial monitoring and verifi cation process to prove energy savings. The company says its solutions can be disabled after installation, allowing for an easy comparison of energy consumption with them on and off. Combined with metering of the amperage for each phase of each compressor in the system, temperature logging of the controlled space and
ambient conditions, and regression analysis of the data, Smartcool says the system provides customers with a clear picture of the improved energy effi ciency of their chiller.
Smartcool claims Hilton Hotel Malta has cut its energy consumption by 78,840 kWh per year, saving more than ¤12,000, and expects a return on investment in less than 24 months. Its CO2 emissions have been reduced by 69,222 kg. Smartcool installed its ESM product to optimize three Trane chillers at the Hilton. Two centrifugal and one screw chiller provide the majority of the air conditioning for the entire hotel. ‘The installation of the Smartcool system on our chillers was carried out without disruption to our operation. We are very pleased to have reached and exceeded the expected savings,’ says Joseph Restall, Chief Engineer at the hotel. Similar results were achieved for two Trane centrifugal chillers at the JW Marriott in Miami, Florida, says Smartcool. It claims annual savings of 115,146 kWh with a payback under 24 months and a CO2
emissions reduction of 70,450 kg. The graph below shows the basic monitoring and verifi cation results from four weeks of testing at the JW Marriott. Smartcool was switched from On to Off (or vice versa) every seventh day, and these switch days are discarded from the results. Regression analysis was conducted to account for variations in load on the system caused by changing ambient temperatures. This fi nal analysis demonstrates an overall reduction of 8% in kW consumption by the chiller compressors, with no impact on internal temperature or humidity.
The Radisson SAS Hotel in Dubai, UAE achieved energy savings of 187,089 kWh in a Smartcool project targeting its two York chillers with screw compressors. The hotel reduced its carbon footprint by 110,185 kg and had a return on its investment in just 15 months.
October 2012 CIBSE Journal 21
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