Regional Energy Efficiency Project

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2 Translated from the original publication of BUN-CA ( F9812a Fundación Red de Energía - BUN-CA Air conditioners: Best practices in energy efficiency / Fundación Red de Energía BUN-CA ; Translate by Lucinda K. Taft. 1 ed. San José, C.R. : Biomass Users Network (BUN-CA), p. ; 27 X 21 cm. (Collection: Best Practices in Energy Efficiency) ISBN: Energy Efficiency. 2. Air Conditioners. 3. Rational Use of Energy. 4. Energy Resources. I. Title. All rights reserved. Copyright 2007, BUN-CA. 1st edition, March 2010 San José, Costa Rica This publication was prepared by BUN-CA in the context of its Regional Strategy for Energy Efficiency and it can be used freely for non-commercial purposes, with proper acknowledgement of the author. This publication has been made possible thanks to the execution of the PEER Program (Regional Energy Efficiency Program in the Commercial and Industrial Sectors in Central America), implemented by the United Nations Development Programme (UNDP) and funded by the Global Environment Facility (GEF), under the framework of Operational Program No. 5 of the Climate Change Thematic Area and the terms of contract No The opinions expressed in this document are those of BUN-CA and do not necessarily reflect those of the cooperating agencies. This publication is also developed with the funding from the Kingdom of the Netherlands, through the Program of South-South Cooperation and managed by Fundecooperacion in Costa Rica, the Sustainable Development Secretariat in Bhutan and CePeD in Benin. Note: We are grateful to the many consultants who made technical contributions to this publication. 2

3 Table of Contents Energy efficiency 3 I. What is air conditioning? 4 II. Operation of air conditioners 4 III. Description of the main components 5 IIII. Best practices for energy savings In equipment operation In the maintenance and cleanliness of the equipment In equipment selection In the reduction of heat sources Proper use of a/c 8 Energy efficiency The costs of electricity generation and average demand are raising worldwide, this, in the face of greater competitiveness and socioeconomic development. The urgency of increasing the installed capacity of the interconnected system in the Central American countries to meet the electrical needs of the different consumer sectors is motivating the implementation of cost-efficient actions in the end use of electricity. The electrical equipment used in most industrial processes and in commercial installations generally has low levels of efficiency. In addition, the installed equipment has often exceeded its useful life or is approaching that limit, causing considerable energy waste and resulting in higher operational costs for companies and higher greenhouse gas emissions as a consequence of the growing use of imported fossil fuels in the production of electrical energy. The Energy Network Foundation (Fundación Red de Energía or BUN-CA, in Spanish) and the United Nations Development Programme (UNDP), with funding from the Global Environment Facility (GEF), are developing the Regional Energy Efficiency Program in the Commercial and Industrial Sectors in Central America (PEER), an initiative that is helping to remove barriers to knowledge and technical information toward the development of markets for efficient electrical equipment. The objective of this series of packets for Best Practices in Energy Efficiency is to strengthen technical knowledge throughout Central America, by offering a thematic series of best practices on topics of air conditioners (A/C), electric motors, commercial refrigeration and lighting, to promote electrical energy savings in the industrial and commercial sectors. 3

4 I. What is air conditioning? Air conditioning (A/C) is the process that cools, cleans and circulates the air, while simultaneously controlling its humidity. Air conditioning equipment removes heat from an enclosed area according to the thermal comfort conditions desired, through the use of a fluid called refrigerant. Figure 1 shows a mini-split type air conditioner. Mini-split equipment Window equipment Figure 1. Air conditioning equipment II. Operation of air conditioners The basic air conditioning cycle gathers heat on the evaporator and disposes of it on the condenser. The amount of heat disposed is approximately the same amount gathered on the evaporator, as shown in Diagram 1. a Diagram 1. Basic cicle of refrigeration c d Source:

5 The following processes occur in this cycle: a. Heat is gathered by the refrigerant in the evaporator. b. The compressor increases the pressure and temperature of the refrigerant and pushes it toward the condenser, causing heat transfer. c. The heat discarded in the condenser is transferred to the exterior environment using some means such as natural air or cold water. d. The expansion valve lowers the pressure of the refrigerant creating a pressure differential, allowing the process to repeat itself indefinitely. III. Description of the main components The main components of an air conditioning system are: Evaporator: This is a heat exchanger (a radiator located inside the unit) where the refrigeration effect occurs, by allowing the refrigerant to absorb the heat removed from the spaces being cooled (Figure 2). In Diagram 1 you can see the placement of the evaporator in the air conditioning system cycle. Figure 2. Evaporator Condenser: This is a heat exchanger (radiator) that uses the heat in the gaseous refrigerant coming from the compressor to convert it into a liquid-gas mixture that gives off the heat removed from the conditioned space via condensation, which is why it is placed outside the area (Figure 3). Diagram 1 shows the placement of the evaporator in the air conditioning system cycle. Figure 3. Condenser Compressor: Mechanical equipment that compresses the refrigerant into vapor form, increasing its pressure and temperature, then transports it through the tubing as a hot gas to the condenser. The compressor, in this case, is acted on by an electric motor (Figure 4). Figure 4. Compressor Expansion valve: A mechanical device that lowers the pressure of the refrigerant as it passes through from the condenser. The refrigerant leaves the valve as a low-temperature low-pressure gas, going through the tubing to the evaporator (Figure 5). Figure 5. Expansion valve 5

6 Refrigerant: This is a fluid that acts as a cooling agent, with special properties for achieving evaporation and condensation points. Through changes in pressure and temperature, it absorbs heat from one space and dissipates it in another. There are several kinds on the market, depending on the desired use (Figure 6). Figure 6. Refrigerants Fan: Circular mechanical element that moves the flow of air through the condenser and/or the evaporator (Figure 7). Figure 7. Fan Thermostat: The function of this device is to automatically turn the air conditioning system on or off, in order to keep the area acclimatized or conditioned within the temperature range desired by the user (Figure 8). Figure 8. Thermostat IV. Best practices for energy savings 4.1 In equipment operation Regulating equipment in the comfort zone Comfort factors are directly related to people s productivity, because intense heat accelerates heart rate and transpiration intensifies when relative humidity is high, appreciably diminishing physical and intellectual output. The temperature should be as comfortable as possible (between 23ºC and 27ºC [73.4ºF to 80.6ºF]). In fact, an area occupied by people who feel cold is simply a waste of energy, and a temperature setting of 24ºC [75.2ºF] is recommended so as not to sacrifice user comfort. BUN-CA prepared a case study on the substitution of a chiller type central air conditioning system, executed by the Technological University of Panama. 6

7 Consider the on-off cycles. It is recommended that the compressor operate with the fewest number of on-off cycles possible, because each time the A/C equipment restarts, it requires more electrical power and causes more wear and tear. Turn off the equipment when it is not in use. If there is no automated system, create a culture among users and those in charge of maintenance of turning off the A/C equipment when it is not in use. Do not leave unnecessary lights turned on. Lamps generate heat when they are turned on, which causes greater power usage by the A/C unit. 4.2 In the maintenance and cleanliness of the equipment Properly maintain the equipment Maintenance should be carried out periodically (at least two times per year) to ensure that the condenser, the evaporator and the filters are clean and free of dirt, and to verify that the refrigerant is properly charged; having too much or too little refrigerant volume means more electricity consumption. Consult the manufacturer s manual to check the recommendations for maintenance cycles. 4.3 In equipment selection Choose proper size equipment Equipment that is too large for the space to be air conditioned requires a higher initial investment and it will use more electrical power and have elevated energy consumption during operation. Buy high quality parts It is recommended that only good quality parts and components be purchased, preferably original ones, so that the equipment operates efficiently and its useful life is prolonged. Use equipment of the same brand Use of the same brand and model of equipment is preferred to simplify the acquisition and control of the spare parts inventory. Replace inefficient equipment When necessary, replace equipment that is inefficient or that has completed its useful life and substitute it with other efficient equipment, with an Energy Efficiency Ratio (EER) of 10 or higher, such as devices with the Energy Star seal. Energy Star Energy Star is an internationally recognized seal issued by the United States Environmental Protection Agency and the Department of Energy for reducing electricity consumption and protection the environment. 7

8 4.4 In the reduction of heat sources Seek ways to reduce solar radiation Using exterior elements such as blinds, curtains, tarpaulins, polarized or reflecting films and external shades or canopies can reduce direct incident light from the sun s rays and thus the solar heat load. Eliminate air infiltration Infiltrations of hot air from the outside into the air conditioned spaces should be reduced as much as possible. A good seal against air leaks in windows and doors will lead to electricity savings from the reduced use of the air conditioning system. Install efficient insulation High efficiency insulation material should be used in the walls and roofs of the air conditioned space as much as possible. Trained technical personnel should install the insulation. Use vegetation The solar heat load can be reduced by placing trees and plants in front of external walls and windows. Minimize the use of skylights Skylights considerably increase the heat load from solar radiation. Install an extraction hood Kitchen equipment in air conditioned spaces should have extraction hoods remove vapors. This measure appreciably reduces the heat load from food vapors during cooking, as well as maintenance requirements. Set minimum ventilation levels Outside air ventilation levels should be adjusted to the recommended minimums. Smoking inside acclimatized spaces is not recommended. BUN-CA prepared a case study on the substitution of window type air conditioners with mini-split units, executed by the Hotel Frontera, Nicaragua. 8

9 4.5 Proper use of A/C Use ventilation If possible, open the windows and use built-in or portable fans or ventilators instead of air conditioners. Some air conditioning equipment allows use of the fan without cooling. Distribute air efficiently Fans can be used to distribute fresh air throughout internal environments when the air conditioner is operating, thus reducing the time it takes to acclimatize the entire space. Automate the A/C Programmable thermostats are recommended for use with the air conditioner to regulate the temperature for times when few people are working, so as not to turn off the equipment completely. In large spaces, equipment that is turned off at midday will have to work at higher power to re-cool the area when the users return. The use of occupancy sensors can help improve A/C equipment performance. Place thermostats correctly Do not use sources of heat such as light bulbs, coffeemakers, computers or televisions near the air conditioner thermostat. The heat from these devices will make the equipment operate longer. Consider work hours There are peak hours when the heat load is higher, and other hours when it is minimal; therefore, air conditioning equipment should be chosen that can handle partial thermal loads or use small spaces instead of a large one. Technical standards for air conditioners When buying new equipment, take into account the technical standards and energy efficiency labeling for the air conditioning systems developed in each country, which specify minimum efficiency performance indices and direct one to the acquisition of more efficient equipment. To reference the technical standards, consult the national standards entity in each country 9

10 Observations (Note other useful practices here) For more technical information on energy efficiency, visit our Web page at 10

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