green cooling initiative: Energy efficiency

Energy Efficiency

Energy efficiency improves energy security

Governments are interested in energy efficiency because they have to ensure energy security. Energy use in many developing countries is rising due to more industrial activity but also due to the increased use of applications such as air conditioning, domestic and industrial refrigeration. This leads to strain on the electricity grid especially during peak hours and – unless a lot of money is invested in new power plants and an updated power grid – can cause power cuts.
Supporting efficiency measures financially or introducing laws that regulate the energy consumption of applications such as minimum energy performance standards (MEPS), labelling or appliance replacement schemes can be a cost effective way for governments to avoid or postpone having to build new power stations and to balance the increased use.

Energy efficiency saves money

Energy efficient applications can save the end-user a lot of money over the unit’s lifetime. Sometimes the initial cost of efficient units is higher than that of less efficient ones. Depending on the electricity prices the payback time of more efficient units can be as low as one year. After this period, users save money. Many countries offer subsidies for efficient units or even replace old units to help overcome the barrier of higher initial costs. For bigger industrial systems there may be grants that can be paid back through savings made by lower electricity costs.

Energy efficiency reduces CO2 emissions

The environment profits because less energy consumption means less CO2 emissions and can also mean less air pollution in the case when electricity is produced by burning coal or wood.

The energy efficiency of units in the air conditioning and refrigeration sectors depends on several factors:

  • Technology: Over the last few years, several efficient technologies have emerged. The most prominent for many applications is the inverter technology that allows for better control especially when a unit is not running at full load. Part load operation is more efficient and most units are designed to have higher capacity than is needed most of the time so that part load operation is the norm.
  • Refrigerant: The efficiency of an air conditioner or a refrigerator also depends on the refrigerant and its thermodynamic properties. Some refrigerants are more suited for some applications and climate zones than others and therefore lead to higher efficiencies. Hydrocarbons (HC) for example have very good thermodynamic properties and units with HC refrigerants are usually more efficient than the same units with fluorinated refrigerants. CO2 is an excellent refrigerant in ambient temperatures below around 30°C, but for now less efficient in hotter climates. Necessary cycle modifications for CO2 mean that it is not very economic in smaller applications such as room air conditioners.
  • Climate: Even though the energy ratings in terms of energy efficiency ratio (EER) are the same no matter if an air conditioner is bought in Sweden or India, the actual efficiency and energy consumption is very different. EERs are by definition measured at an outside temperature of 32°C and an inside temperature of 26°C, so the energy consumption depends on how close the actual temperatures are to standard conditions.
  • Design: The efficiency of a unit can be improved by optimising components. Heat exchangers and compressors can be optimised for the specific applications and most importantly the refrigerant. Stand-by losses can be reduced and controls improved.