In the face of the climate change, energy consumption is one of the main issues to be solved. Energy audits are useful tools that may contribute to develop energy efficiency initiatives. The purpose of this paper is to provide insights into how energy audits, with a scope on air conditioning (AC) systems, contribute to develop energy efficiency options for a government building in the city of Hermosillo, Mexico. The methodology is based in the energy audit framework proposed by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE). Results show that, in a typical day of maximum consumption, AC represents 64% of the total electrical consumption, while office equipment accounted for 22%, and lighting 14%. Additionally, AC system has a yearly consumption of 54,419.40 kWh with an emission estimate of 24.92 tons of CO 2-eq/year. Three approaches for energy efficiency proposals were addressed through AC systems: Improvement of the operation and consumption habits, maintenance and reconditioning of facilities, and replacement of AC units. While Mexico has international commitments through environmental treaties related to contribute to climate change mitigation, this study shows that, at least one government building still produces potential impacts that can be deterred by addressing structural and behavioral changes related to AC operation. Finally, this study may be used as reference for energy efficiency practitioners or decision-making authorities in the public administration field for developing better energy policies for government buildings.
Climate change is defined by the United Nations Framework Convention on Climate Change as “a change of climate which is attributed directly or indirectly to human activity that alters the composition of the global atmosphere and which is in addition to natural climate variability observed over comparable time periods” [
The concentration of atmospheric carbon dioxide has been an indicator linked to climate change which has been used as evidence of the effects generated by human activities on the chemical composition of the atmosphere, including greenhouse gas (GHG) emissions, such as those created during the burning of fossil fuels [
To reduce and/or eliminate the adverse effects of climate change, it is necessary to implement adaptation and mitigation measures. Adaptation is the adjustment process to the current or expected climate change and its effects, and mitigation refers to a human intervention aimed to reduce GHG sources or to improve the storage of those emissions [
In terms of adaptation measures, in developed countries, short-term interventions have been the primary approach because that represents less risk as compared to long-term strategic planning, which has an increased vulnerability and difficulty in regards to the implementation of actions in the future [
In Mexico, carbon dioxide equivalent (CO2-eq) emissions reached 748 million tons in 2010, representing a growth of 33.4% as compared to the emissions in 1990 [
In order to avoid a temperature increase of 5 to 6 degrees Celsius by the end of this century, energy efficiency programs must be established in all sectors across all of the countries globally [
Regarding the economic benefits of energy efficiency, these are almost always viable in the long term because they help to reduce emissions and strengthen energy security; however, economic incentives are necessary to develop the potential of energy efficiency and increase private financing for these initiatives in the short term [
Some countries have adopted policies and measures to increase energy efficiency levels in buildings in order to reduce their total electricity consumption [
One tool aimed at energy efficiency is conducting an audit that detects operational problems, improves the comfort of the occupants, and optimizes energy use in existing buildings [
An energy audit provides key information that can be utilized to carry out interventions to reduce what is known as the “energy efficiency gap”, which consists of insufficient investment by both the public and private sectors in energy saving technologies in buildings, from which one of the primary causes for this is the lack of timely information [
The purpose of this paper is to provide insights into how energy audits contribute to develop energy efficiency options that can reduce the potential environmental impacts related to electricity consumption of a government building in the city of Hermosillo, Mexico.
An Energy Audit (EA) for a government agency building located in the city of Hermosillo, Sonora in the northwestern area of Mexico. The purpose of the audit was to identify opportunities for improvement through the identification of better energy options and to promote a culture of energy efficiency among the government personnel with the ultimate goal of contributing to the reduction of greenhouse gases (GHG) emissions. The scope of the audit was the air conditioning (AC) system, which provides the indoor comfort conditions for an optimal performance of the activities carried out by the personnel in the administrative areas.
The study was carried out from September 2016 to July 2017 and covered all of the facilities. The methodology used for the EA was based on a program originally proposed by the American Society of Heating, Refrigerating and Air-Conditioning Engineers [
The main steps involved in conducting the EA are as follows. A pre-evaluation is done to gather basic geographic data and general information of the building. An in-situ evaluation is performed to collect further data, to identify energy efficiency opportunities, and to hold preliminary meetings to explain the process to the various stakeholders. Next, an analysis is done to review all the data obtained, to prioritize the opportunity areas from lowest to highest economic cost, as well as to establish potential savings’ estimates. Finally, a report is delivered at a final meeting with the stakeholders to provide explanations, recommendations, and an action plan.
To obtain and process data for the study, several instruments were utilized.
・ Measuring tape: The measurement of each office, as well as the total area of the building, is important to determine accurately some energy indicators. In the absence of architectural blueprints of the structures, it was decided to take measurements manually of each audited area.
・ Thermographic camera, Model E5 Flir: This instrument takes thermal photographs, which show the full range of temperatures present in the location through an image containing different shades of colors. The lighter and brighter colors indicate higher temperatures, and the darker colors indicate lower temperatures. Thermal images were taken with the purpose of creating a thermal map of the typical conditions in the work environment.
・ Digital Camera: With this device, images of the physical conditions of the building were taken.
・ Excel: Once the on-site evaluation and the collection of all data were complete, databases were generated using Microsoft® Excel® software in order to analyze the energy results, to obtain indicators, and to study potential scenarios for the proposed recommendations.
Hermosillo, Sonora, where the building is located, has a climate that ranges from dry to very dry with warmer temperatures most of the year reaching high values close to 50˚C (122˚F); consequently, the use of AC is necessary. The official working hours for the employees are from 8:00 a.m. to 3:00 p.m. on Monday through Friday; however, there are employees who continue to work longer into the afternoon occasionally.
The building, inaugurated in 1954, first hosted a primary school and later was adapted to serve as government offices. The total area of the building, including the exterior offices, is 790.91 m2. The original structure has been maintained; also, offices were built in several of the corridors on the ground floor and upstairs.
According to the electricity bills issued by the Federal Electricity Commission (CFE), the government building had a consumption of 96,320 kWh over the period of November 15, 2015 to October 16, 2016. According to the Emissions Calculator for the National Emissions Registry of the Secretariat of Environment and Natural Resources and the Inter-American Development Bank [
One of the first necessary tasks was to create a blueprint of the building. Thirty-eight sections were identified within the sixteen administrative areas. For instance, the three largest administrative areas were Administration and Finance, with 110.72 m2, Environmental Management, with 108.36 m2, and Executive Commission, with 94.69 m2.
For each section of the whole administrative areas, a detailed inventory of air conditioning, lighting, as well as electronic and electrical office equipment was created, including information about the types of equipment, the models, the levels of power, the timeframes for typical daily use, and an estimated daily energy consumption for each.
For example, in a typical day of maximum consumption, with all the devices turned on, the AC system represented 64% of the total electrical consumption, while office equipment accounted for 22%, and lighting was only responsible for 14%, as seen in
Administrative area | Quantity | Type | Brand | Refrigerant type | Electric power W | Time of use h | Consumption kWh | Cooling capacity BTU/h |
---|---|---|---|---|---|---|---|---|
Administration and Finance | 1 | Fan-coil | Lennox | R410A | 3916.0 | 7 | 36 | 36,000 |
1 | Mini-split | Rheem | - | 2200.0 | 7 | 178 | 24,000 | |
1 | Window | York | R22 | 1789.0 | 7 | 318 | 17,843 |
Source: Own elaboration.
Item | Quantity | Estimated Daily Energy Consumption kWh |
---|---|---|
Air Conditioning (AC) units | 36 | 431.91 |
Equipment (electronic and electric) | 178 | 148.78 |
Lighting (lamps and bulbs) | 318 | 90.30 |
Total | 670.99 |
Source: Own elaboration.
Additionally, the condition of the thermal insulation in the building was reviewed, and the various types of materials used, including their different coefficients of thermal conductivity, were identified. For instance, the external brick, the external panels (Durock®), internal panels (Drywall®), glass, polycarbonate, glass windows, cast concrete used on the ceilings, and the expanded polystyrene panel used on the ceiling lamps were all noticed within the building. The characteristics of these various materials, as well as their geographical orientation, were necessary to identify so that the areas where there is greater heat transfer that is occurring between the exterior and interior of the offices could be determined.
Furthermore, the state of the windows was also recorded, including the condition of the polarizer film that some of the windows had, as shown in
A sampling of thermographic photographs, as shown in
Additionally, the roof conditions were also analyzed. On the top floor of the main building, a lack of maintenance was identified since the waterproofing was in poor condition and included unprotected areas, as illustrated in
The consumption pattern identified a monthly average of 8026.66 kWh, with an average cost of $2.00 Mexican pesos, the equivalent of $0.1081 US dollars [
per kWh consumed. The month with the greatest demand for electricity was estimated to be from June 16 to July 16, 2016 with a demand of 13,520 kWh. Furthermore, as shown in
Assuming that on a typical summer day all of the equipment is in use, there is a consumption of 670.98 kWh. Thus, if one month has 21 business days, then 14,090.58 kWh are consumed monthly. If this amount is compared with the month of highest consumption, which was recorded at 13,520 kWh, a difference of 570.58 kWh or 4.22% is estimated, which is very close to the actual value.
When organizing the energy consumption by administrative area on a typical summer day, it can be identified that three areas combined, the Administration and Finance, the Environmental Management, and the Executive Commission, represent 48% of the total, as detailed in
On the other hand, on a typical winter day, when the air conditioning systems are usually turned off, the consumption is estimated at 239.08 kWh per day, having a monthly estimation of 5020.68 kWh, with office equipment representing 62% of the total and lighting 38%. Comparing this estimate with
Annual Energy Consumption | Total Area | Number of Employees |
---|---|---|
96,320 kWh | 702.94 m2 | 56 |
GHG Emissions | Energy Use Intensity | Consumption per capita |
44.11 tons of CO2-eq | 137.02 kWh/m2/year | 1720 kWh |
Source: Own elaboration.
Administrative area | Lighting kWh | Office equipment kWh | Air conditioning kWh | Total kWh | Total consumption % | Accumulated % |
---|---|---|---|---|---|---|
Administration and finance | 13.18 | 49.69 | 55.33 | 118.20 | 18 | 18 |
Environmental management | 8.74 | 15.82 | 78.89 | 103.44 | 15 | 33 |
Executive commission | 9.18 | 14.97 | 74.17 | 98.32 | 15 | 48 |
Common areas | 12.88 | 14.36 | 25.62 | 52.86 | 8 | 56 |
Purchasing office | 5.46 | 7.18 | 25.90 | 38.54 | 6 | 61 |
Administrative Control and Development Body | 5.38 | 5.11 | 25.55 | 36.03 | 5 | 67 |
Human Resources | 1.79 | 7.43 | 22.82 | 32.05 | 5 | 71 |
General Legal Management | 5.38 | 8.56 | 17.85 | 31.79 | 5 | 76 |
Conservation | 2.47 | 3.86 | 25.06 | 31.39 | 5 | 81 |
Technical Coordination | 2.74 | 7.42 | 19.60 | 29.77 | 4 | 85 |
Meeting room | 2.91 | 0.29 | 22.4 | 25.60 | 4 | 89 |
Communication | 1.79 | 7.58 | 11.20 | 20.57 | 3 | 92 |
Exterior lighting | 15.71 | n/a | n/a | 15.71 | 2 | 95 |
One-stop shop | 1.79 | 1.16 | 11.20 | 14.15 | 2 | 97 |
Information technology | 0.45 | 4.74 | 8.40 | 13.59 | 2 | 99 |
Commissioner Advisor | 0.45 | 0.61 | 7.91 | 8.97 | 1 | 100 |
Total | 90.30 | 148.78 | 431.90 | 670.98 |
Source: Own elaboration.
the consumption generated between January 16, 2016 and February 16, 2016, a difference of 300.68 kW or 6.37% is estimated.
For the purpose of this paper, an emphasis on the AC system was made. Hence, it was determined that the AC system is used for six months a year. Consequently, since it consumes 431.90 kWh on a typical summer day, its yearly consumption is 54,419.40 kWh, which is 56.5% of the total annual electricity consumption, representing an emission value of 24.92 tons of CO2-eq/year.
An installed cooling capacity of 621,799.00 BTU/h was identified as being 51.82 cooling tons. 36 AC units were recorded including 14 window type units, 20 mini-split type units, and 2 fan-coil type units. Another aspect to consider is the presence of 12 different AC manufacturers. Due to the absence of a technical plate on some of the equipment, only the refrigerant type for 22 AC units was registered; 19 used refrigerant R22, and three used refrigerant R410A.
In summary, the following opportunities for improvement were found in the AC units along the building.
Window type AC units: see
・ Equipment with vibration problems, most likely caused by unbalanced turbines
・ Air leaks in window frames which results in equipment that works without reaching the desired temperature, so the compressor stays on
・ Compressors with vibration
・ Electrical installations are in poor condition so there is a loss due to lack of adjustment in panels, which cause the wiring and circuit breakers to heat up
・ AC air outlet obstruction
Mini-split type AC units: See
・ Return and suction lines without lining
・ Service valves with loose plugs
・ Condensing machines with insufficient anchorage
・ Drainage system incorrectly installed so leaks are visible on the walls
・ Poor lines installation, which can generate oil traps and damage the compressor
Fan-coil type AC units: See
・ Unlined suction and discharge lines
・ Return without a connection to the handler, which results in the equipment works in full camera
・ Pipe taken off the air outlet
・ Air outlets with an accumulation of dust and dirt
A final report was delivered to the government agency representative with three main proposals related to the AC usage for improving the energy efficiency as well as reducing the environmental impact of the building related to electricity consumption. It is important to highlight that, at the edition time of this paper, these measures still are being analyzed by authorities and their implementation will depend on the decisions made accordingly.
Proposal 1: Improvement of the operation and consumption habits
In June of 2017, the Code of Ethics and Conduct, as well as the rules of integrity for public employees of the State Public Administration, were published [
In line with such a code, the first proposed measure is one that requires a lower economic investment. As a first step, employees should be trained about the benefits of carrying out actions that result in energy efficiency, including the three aspects of sustainability, which are social, environmental, and economic.
An internal policy needs to include that during the season when electricity is in high demand from May to October, AC units must be set to a temperature range from 24˚C to 26˚C. During operating hours, all doors and windows must remain closed, and, in case of leak-related problems, a report to maintenance personnel needs to be filed. Other possible measures might include disconnecting devices that are not in use and turning off office equipment as well as indoor lights at the end of the workday.
It is important to assign an employee to serve in the role of an energy efficiency supervisor. This position may rotate periodically among the employees in order to strengthen an overall energy efficient culture. This supervisor would have several functions and characteristics, including but not limited to, coordinating the actions aimed at reducing electricity consumption in the building, having access to all offices, and being the only person authorized to handle thermostats and controls. In addition, this individual will turn on the AC progressively, not all at once, at the beginning of the work day, either manually or automatically scheduling that gradual ramp up, and provide reports organized by administrative area to the necessary corresponding authorities.
Proposal 2: Maintenance and reconditioning of facilities
The current AC units are made by 12 different manufacturers, which makes it difficult to carry seasonal services or to request orders for eventual replacement of components since some of the commercial brands have few roots in the national market. Each piece of equipment has its own specific problems, such as a compressor change, pipe leaks, return lines, unlined suction, a lack of anchoring in condensers, and vibration problems due to unbalanced turbines among others. It is important to install bases for the condensers on the mini-split type AC units to avoid heating if it comes in contact with the roof or a fall due to the vibrations or wind that could potentially damage the operation.
Only two out of the 20 mini-split type AC units installed have a static anchoring system, so the remaining 18 need to be fixed. It is necessary to maintain the AC units, especially the fan-coil type, since a lot of dirt was detected in the exits of the ducts, as well as a duct that had completely decoupled from the ventilation grid, which is causing a reduction in efficiency. The fan-coil type AC units operate by thermostats with basic functions; for this reason, it is proposed to replace them with programmable digital thermostats to automate the operation of the equipment by the day and time. A full diagnostic by an external provider for the whole AC system and implementation of minor measures, as described above, would represent a total investment of $1400.00 US Dollars.
Proposal 3: Replacement of AC units
From the 36 AC units, three use refrigerant R410A, and 19 use refrigerant R22, four of which were recently purchased. The remaining 14 could not be determined due to the absence of a technical plate on the equipment. Since Mexico ratified the Montreal Protocol in 1987 [
For this reason, the replacement of window type and conventional mini-split type AC units by mini-split type AC units with inverter technology operating with refrigerant R410A would be ideal measure. This change could result in an estimated range of annual electric consumption savings of 4545.42 kWh to 15 066.59 kWh, which translates into avoiding the emission range of 2.08 tons of CO2-eq/year to 6.9 tons of CO2-eq/year. Nevertheless, changing the entire AC system would require an investment of $20,000.00 US Dollars. Since this is a non-profit government entity with limited financial resources, the emphasis must first be on the AC units that could affect the greatest change for the lowest cost investment, and then, as much as possible, gradually change the other units over time.
As Mexico is one of the countries that ratified the Montreal Protocol [
In line with the findings from Dubash et al. [
As a conclusion, AC systems are one of the main contributors to energy consumption, approximately 50%, particularly in arid zones. Therefore, undertaking energy audits may trigger key initiatives that will reduce electricity consumption and improve the energy efficiency in government buildings while still providing a comfortable work environment, by minimizing the facility’s potential environmental impacts.
Authors want to thank Luis Federico Olivarría-Ávila, Ana Magdalena Sotomayor-Tovar, Omar Alexis Cabanillas-González, Alan Arnoldo Alcantar-Gómez, and Hilary Platt-Lopez, students of Sustainability Graduate Program at University of Sonora, for their valuable support to the project.
The authors declare that, to the best of their knowledge, no conflict of interest of any type exists.
Velazquez, L.E., Perez-Rios, R., Munguia, N.E., Zepeda, D.S., Neudert, C. and Esquer, J. (2018) Environmental Approach for Energy Audits on Government Buildings: A Mexican Case for the Air Conditioning System. Journal of Environmental Protection, 9, 278-293. https://doi.org/10.4236/jep.2018.93019