Saving Energy in Hotel Air Conditioning Systems with Variable Speed Drives

Carlos Aguirre-Danfoss in cooperation with the Alliance to Save Energy

The majority of people like to feel at home during their stay at a hotel. The food and beverages, the interior quality of the room all contribute to a great extent to the comfort of guests. However, an inefficient HVAC system (Heating, Ventilation and Air-Conditioning) can overturn the satisfaction experienced by the clients in even the fanciest of hotels.

By installing Variable Speed Drives (VSDs) to control, for example, the Variable Air Volume (VAV), ventilators in the cooling tower, pumps for water condensation, chilled water pumps, etc. you are ensured that the entire system provides only what is necessary for a given occupancy demand.

The conditions of present competitiveness demand a greater efficiency in the operation of the Hotels in addition to other parameters important in the relation between cost/utility of the building.

The consumption of energy in Hotels is very significant as well as the price of electrical energy alternates becoming more expensive. Savings in energy consumption of up to 50% in HVAC systems of a Hotel can be reached depending on the installation, location, demand, etc. in comparison with traditional systems.

The turnaround time of the investment is generally smaller to 24 months thanks to the savings of up to 50% of the electric consumption of energy.

Many of the existing systems of HVAC operate at 100% of their capacity during the day and night. This is independently of what this variation demands. Usually the systems determine the proportions to fulfill the worse case of the demand that is usually maximum occupation on the warm days.

Typical Thermal Load of a Hotel

Different methods exist to fit to the operation of the pumps and/or ventilators of HVAC systems in function of the existing demand in a Hotel.

The traditional methods involve mechanical solutions independently operating on a constant level independent of the present demand. The water or air volume is then controlled, obstructing the flow by means of floodgates or valves according to the case. The most common uses are:

• Floodgates/ Valve of Control
• Inlet Guide Vanes
• Variations of Speed

To continue, we present two graphs that show the difference in the electric consumption in Kw between a mechanical solution and the one of an electronic control by means of Variations of Speed.

System with obstruction of flow System of variable flow

By Floodgates or Valve by variation of speed
According to the previous graphs, we can appreciate that in the traditional mechanical system, even when we fulfill the requirement of water or air flow to be able to satisfy the demand of comfort of air conditioned by means of the obstruction of the ducts or pipe using floodgates or valves, respectively, what we cause is the increase in the pressure and a very poor reduction of the electronic consumption.

In the system with variations of speed we appreciate, for example, that with one reduction in the flow by 50% we obtain a single consumption of energy of the 12.5% of the maximum capacity of energy in Kw of the motor in question.

The Alliance to Save Energy is a nonprofit organization established in Washington D.C. that works in Mexico. For information or educational resources, please contact Ms. Stephanie Campbell (202)530-2224 or fax (202) 331-9588 in Washington, D.C.