ENERGY EFFIENCY MEASURES IN EDGE
© International Finance Corporation 2021. All rights reserved. EDGE User Guide 108
Potential Technologies/Strategies
Simple air-conditioners fitted in windows and through-the wall unitary air-conditioners are the most common
type of air-conditioners used in individual residential units. Apartment buildings may use packaged air-
conditioners located on roof tops with ducted air flow. However, these are the least efficient types of systems.
Various air-conditioning systems are available that achieve higher cooling efficiency, including split air-
conditioners, multi-split air conditioners, VRF systems and chillers.
Split air-conditioners are direct expansion (DX) mechanical refrigeration systems with a single condenser unit
outside serving a single fan coil unit (evaporator) inside the building, with refrigerant carried between the two in
narrow tubes through the wall. These do not require ducts, and are more efficient than ducted systems. But
they can only serve fan coil units located at a limited distance from the external condenser unit.
Multi-split air conditioners are like split systems, except that a single large condenser unit is connected to
several fan coil units with individual tubes. The added advantage is the fewer number of outside units. But these
systems can only serve spaces that are at similar temperature conditions.
Variable Refrigerant Flow (VRF) systems have one condensing unit with multiple indoor units, each of which
can be individually controlled. These systems use refrigerant as the medium for heat transfer. The system runs
by modulating the amount of refrigerant that is sent to each evaporator, running only at the rate needed to
deliver the cooling required by each internal unit. They systems are a step up from multi-split systems because
they can serve zones with different thermal needs, including zones that may be in heating mode while other
zones are in cooling mode. VRF systems accomplish this through compressors that can modulate their speed
and the refrigerant flow. The refrigerant is distributed through a piping network to multiple indoor fan-coil units,
each capable of individual zone temperature control through a common communications network. The system
runs only at the rate needed to deliver the temperature change required by each internal unit. To realize
savings from a VRF system, the spaces must be zoned separately with their own individual thermostats.
The three basic types of VRF systems include: cooling only, VRF heat pump that provides both heating and
cooling but not simultaneously, and VRF with heat recovery that provides heating and cooling simultaneously.
VRF systems may be a particularly good option for buildings with multiple zones or wide variance in
heating/cooling loads across many different internal zones. As these systems provide individual control and are
the most versatile of the multi-split systems, VRF systems may be the best for buildings such as homes, offices,
retail buildings, education, healthcare buildings, or hotels and resorts.
The outdoor units can be fitted to as many as 48 internal units. Due to the way the internal units are connected
to the external unit, a breakdown of one internal unit will not compromise the rest of the system. The speed of
the outdoor compressors can change to operate in a range of 6% to 100% capacity. Capacities have typically
ranged from 5.3 to 223 kW for outdoor units and from 1.5 to 35 kW for indoor units, but new products are
continually being introduced. Multiple outdoor units can be used if an even greater range of capacity is required.
Note that the same measure applies to a Variable Refrigerant Volume (VRV) cooling system, which is a patented
name for a type of VRF system.
Chillers. Chillers deliver cooling through chilled water which has much higher heat capacity than air, allowing
heat to be transferred more efficiently. Chilled water is circulated to provide comfort cooling throughout a
building. The system has four components: i) Compressor, ii) Condenser, iii) Thermal expansion valve, and iv)
Evaporator. The compressor compresses the refrigerant and pumps it through the air conditioning system at a
designed flow rate and pressure. The compressor technology is a way to distinguish the type of air-cooled