Lower Your Peak Demand With Natural Gas Chillers

Natural gas engine-driven chillers can help commercial building owners reduce electric peak demand charges and lower operating expenses. Although they may cost more to purchase and install, most engine-driven chillers offer a simple payback within three to five years. Other potential advantages of gas chillers include variable speed control, high part-load efficiency and waste heat recovery.

Technology

Gas engine-driven chillers have been in use since the 1960s. They utilize the same refrigerant compression cooling system as conventional electric motor chillers. The major difference is that the compressor is powered by a natural gas engine instead of an electric motor. Engine-driven chillers are roughly the same size as their electric counterparts and thus can be easily installed. Gas chillers are available with reciprocating, screw and centrifugal compressors.

Recent advances in gas technology has resulted in improved system performance and lower maintenance requirements. In particular, the use of microprocessors provides close monitoring capabilities combined with control of system parameters. This helps to facilitate preventive maintenance and allows for remote monitoring and troubleshooting.

Applications

Gas engine-driven chillers are most commonly used for space conditioning in a variety of commercial building types. They can also be used for process cooling, commercial and industrial refrigeration and ice making. Industries that can benefit from natural gas cooling include:

• Healthcare
• Schools and universities
• Office buildings
• Retail
• Hospitality
• Manufacturing
• Ice rinks

Engine-driven chillers make the most sense in applications where the electric demand charge is high. Because cooling is generally the most significant cause of electric demand spikes, gas cooling has the potential to largely minimize or flatten electric peak load in a building. Engine-driven chillers should be operated to maximize electric peak shaving. Thus, many facilities with engine-driven chillers operate a hybrid plant, which has both an electric and gas chiller installed. The gas unit is operated during times of peak electric demand.

Benefits

Engine-driven chillers offer a number of potential advantages over electric motor systems:

• Lower operating costs by reducing peak loads in applications with high peak demand charges. Energy costs can also be lower even though gas engine efficiency is lower than electric motor efficiency.
• Heat recovery for refrigeration or for process and space heating. This can result in greater operating efficiency than similar electric units.
• Fuel choice includes natural gas or other sources, such as biogas, to provide cooling and hot water for space conditioning or process applications.

Factors to Consider

Because engine-driven chillers can have a higher equipment and installation cost initially, the system payback needs to be justified by overall operating cost savings over the projected life of the unit. Engine-driven chillers are most effective in applications where a three to five year payback is acceptable. Maintenance costs will also need to be factored into this equation.