Energy Audit and Management of a Tannery Company: A Case Study of Kano State

Energy audit is considered as one of the comprehensive methods in checking the energy usage and wastage in facilities/buildings. This paper presents the results of the energy audit conducted to investigate the energy consumption pattern of tannery company from its record of fuel expenditure and electricity bills for a period of 5 years (2012 2016). Also, the use of energy models system, Energy Quick Energy Simulation Tool (eQUEST) to evaluate the consumption of the energy end users and performance of the company. Results shows peak electricity demand during the hot months from April to August due to high cooling or significant Air condition requirement. 2.37% of electricity consumed was contributed by the burning of AGO in the diesel power generators showing very less contribution over that of National grid 97.63%. The annual average consumption demand of electricity and diesel (kWh equivalent) of the company were 118960.72 kWh and 2881.17 kWh respectively. The energy modeling and simulation results shows that the sum total of the total monthly energy consumption by the end users is 138164 kWh representing the total average value of the annual energy use in air-conditioning (space cooling) was 27%, ventilation fan 2%, factory machineries 39%, heat rejection is 4%, pump and auxiliary is 2% and area lighting 26%. Also, the total monthly peak demand by space cooling was 22372.2 kWh, ventilation fan 1376 kWh, factory machineries 14294kWh heat rejection is 4461 kWh, pump and auxiliary is 1343 kWh and area light 11023 kWh respectively having a sum total monthly peak demand by the end users to be 44969.2 kWh. This represent energy use in air-conditioning (space cooling) was 41%, ventilation fan 3%, 26% factory machineries, heat rejection is 8%, pump and auxiliary is 2% and 20% area light of the annual peak demand. The Energy Used Index (average annual electricity use per tones of leather) was found to be 717.38kWh/tones of leather/Annum.


Introduction
Energy has a major impact on every aspect of our socioeconomic life. It plays a vital role in the economic, social and political development of our nation. Inadequate supply of energy restricts socio-economic activities, limits economic growth and adversely affects the quality of life [1]. In Nigeria, a lot of energy is wasted because households, public and private offices, as well as industries use more energy than is actually necessary to fulfill their needs. One of the reasons is that they use outdated and inefficient equipment and production processes, therefore, the need for energy is exceeding it is supply in view of these circumstances, primary energy conservation, rationalization, and efficient use are immediate needs. Getting all the possible energy from the fuel into the working fluid is the goal of efficient equipment operations. This leads to higher productivity and saves not only money, but also influences the life and safety of the equipment and reduces pollution [2].
Global, country-specific, and industry-specific analyses continue to show that significant energy-efficiency improvement opportunities exist in the industrial sector, many of which are cost-effective. These energy-efficiency options include both cross-cutting as well as sector-specific measures. However, industrial facilities are not always aware of their overall energy efficiency improvement potential or specific technologies and measures that can be implemented. One of the most common methods adopted around the world to address these issues is to undertake an industrial energy audit. An industrial energy audit is a necessary first step for defining energy consumption by end use and identifying key areas for energy saving in industrial operations. Without baseline energy use data, it is impossible to have a clear understanding of the current situation or to make cost-effective decisions regarding energy-efficiency strategies. An industrial energy audit is also an important impetus to encourage industrial facilities to implement energy-efficiency measures and technologies with most saving potential. In general, preliminary energy audits provide quick estimates of costs, potential cost and energy savings, as well as simple payback periods. Comprehensive energy audits, on the other hand, are enabled to provide detailed cost-effective analysis of all identified measures and technologies, based on plant's specific operating conditions. Creditable energy audits provide packages of customized recommendations for plants to consider. In this regard, an energy audit is often a key component of industrial energy efficiency programs and has also been considered as a supporting policy tool for policies such as voluntary agreements or emissions cap and trade policies [3].
Energy audits are an inspection of energy consumption habits within a building. An audit team examines utility bills, lights, plug loads, the HVAC system, and the building envelope to gather data. These data are used to create one or more models of energy consumption in the building. After these models are verified against actual building consumption, potential methods to reduce energy consumption are modeled to quantify savings from the implementation of each method. Once savings for an Energy Conservation Measure (ECM) are quantified, a financial analysis is performed to determine whether that measure is worth implementing. The worthwhile ECMs are recommended to building owners; along with details about the financial and material investment each measure requires [4].
From the literature, many studies related energy efficiency and savings based on the building sector like commercial and high-volume buildings have found [5,6].

Materials
Materials used in this research are as follows: a) Electricity bills file. b) AGO consumption file. c) Records of skin processed. d) Power ratings of factory machineries. e) eQUEST 3-6.5 version Energy simulation software. f) Laptop Computer.

Energy Audit Simulator
Computer-based simulation is accepted by many energy efficiency studies as a reliable tool for evaluating building energy use and retrofit possibilities [7][8][9]. eQUEST was decided to use because it is a user friendly freeware program that offers a comprehensive set of features: eQUEST predicts the hourly energy use and energy cost of a building given user-input information including hourly weather data, building layout, HVAC description, and utility rate structure [10]. eQUEST v3.65 was used in creating a simulation model of the case study building based on building schematic drawings. In addition to building parameters weather data was also required. The closest weather station with complete weather data available for the period under consideration is in Kano, Nigeria. Utility bills for diesel and electricity from January 2012 and December 2016 were compiled for comparison against simulated energy consumption.

Factory Machineries and Their Uses
The following are some factory machineries descriptions and their uses: a) De-dusting Machine: This is a metal mesh rotating cylinder that can provide the de-dusting process suitable to remove dust from double face leather. b) Dry Buffing Machine: This is a cylinder machines, equipped with sandpaper or emery for the processing of leather with unbuckle or suede effect, or to correct any defects on the leather grain side. Control devices with hydraulic drive are used to quickly reverse the direction of rotation of the feed roller and make it easier the manual extraction of the leather. The systems are supplemented by specific elements of the dust extraction and collection in the bags. c) Fleshing Machine: This is a machine which is scraping off of the excessive organic material from the hide (connective tissue, fat and so on). d) Shaving Machine: This is used in carrying out of shaving process in order to achieve an even thickness throughout the skin/hide, and it can be carried out on tanned or crusted leather. e) Drying machines: The objective of drying is to dry the leather whilst optimizing the quality and area yield. Drying techniques include samming, centrifuging, setting, hang drying, vacuum drying, toggle drying and paste drying. Table B8 present the power rating and estimated daily and monthly energy consumptions of factory machineries and other equipment used in the company.

Computer Laptop Specifications
HP pavilion g6 computer core "i5 system, 2.50GHz processor, 8GB RAM size on Microsoft window 7 operating system is used in the research simulation.

Data Collection
For the energy carriers, the first stage in this study was the data collection, in which a meeting was held with the Management and all key operating personnel, and they were briefed over the audit objectives, the scope of the work and description of scheduled project activities. An energy audit check list was drawn to acquire data by physical checks. The monthly consumption figures of two energy carriers (Electrical and AGO) for a period of five years (2012 -2016) were extracted from electrical consumption and diesel consumption files from physical personnel of the company. Also, information obtained by physical checks where used to construct various types of electricity used profiles, comparison tables, corresponding correlation plots.

Data Analysis
From the data collected, the following procedural steps were adopted to analyze the data, inputted and presented in the required forms: a) Data Analysis for Energy carries i. Energy types (electricity and AGO) were identified and collated. ii. The energy consumption per year for each type of energy carrier was determined. iii. The percentage breakdown of total energy consumption was calculated. iv. The energy used index (EUI) in (kWh/tones of leather/per) year was determined to establish energy utilization pattern. b) Computations for Electrical Energy consumption (kWh) and percentage (%) share for types. i. Energy carriers (National grid and AGO) In this study, monthly average electrical energy consumption and percentage share for the period of 5 years (i.e. 2012 to 2016) are computed from the relation given as follows [3]: Values for the subsequent month and years were computed and presented in the Appendix "B" table B1.
AMEEC for electricity consumption from combine energy types for the month of January was computed using equation (1)  Values for the subsequent months were computed and presented in table B1 of Appendix "B".
MAAEEC for electricity consumption from combine energy types for the year 2012 was computed using equation 2: Values for the subsequent months were computed and presented in table B2 of Appendix "B".
Also yearly percentage of energy types can be deduced using equation (3)  iii. Automotive gas oil (AGO) In this study, AGO consumption by company generator was analyzed. The average monthly diesel consumption, monthly Annual Average diesel consumption and Annual total were determined using the relation as follows [4]: The values of the average consumption for the subsequent years were computed and presented in A total of five years (2012 -2016) electricity consumption data was collected and analyze. To simplify the analysis, the consumption data was averaged over five year's period. Energy used per tones of leather (also known as energy utilization index) is used to compare the energy intensity among different years.
Sample calculation of energy used index for the year 2012. Values for the subsequent years were computed and presented in table B6 of Appendix "B".

Computer Simulation
A. Building Description The case building selected for this research is an industrial building located in the challawa industrial building area of Kano, Nigeria. It is cumulative building area is 51224 m 2 and comprises of machineries area of 41282 m 2 and 9942 m 2 for administration area.

B. Building Material and Envelope
The exterior walls of the building are 9 inches blocks with R-12 polystyrene insulation. The floor is 6 inches concrete base with ceramic/stone finish. The internal walls are 6 inches sheetrock framed on metal studs with insulation on select interiors. The building is operated under positive pressure, which eliminates any potential envelope infiltration. A screenshot of the eQUEST wizard screen for inputting building material and envelope details is displayed in figure  C1.
C. Heating Ventilation and Air conditioning (HVAC) System The building air conditioning is primarily a standard VAV and the domestic hot water is provided by a domestic hot water supply loop connected to central hot water pumps ( figure C2).
D. Building Schedules The building is in operation 5 days a week from Monday through Friday. The occupants generally begin to enter at around 7am and leave at 5pm. The building is closed on Saturday and Sunday as well as on local holidays. A typical schedule input screen for eQUEST is shown in figure C3.

Energy Carriers
Figures 1 and 2 present the monthly electricity (kWh) consumptions pattern and annual energy consumed by energy carriers (electricity and diesel) consumption pattern. These graphs were obtained using Tables B1 and B2 (Appendix B) respectively.
Figures 3 present the monthly diesel (kWh) consumptions pattern. This graph was obtained using Table B7.

Energy End Uses
The case building energy model was simulated in eQUEST using input data from Appendix A. eQUEST provides outputs in two forms: A detailed simulation output file and a summary result/report ( Figure C4). And also table B8 presents estimation of daily and monthly energy consumption per equipment (end users) for the company.
Figures 4 and 5 presents annual energy consumption by end use and annual peak demand by end use respectively.   Table B6 present the annual electricity consumption and energy used index of the tones of leather processed annually in appendix B.

Energy Carriers
The consumption pattern showed distinct seasonal variation, indicating peak electricity demand during the hot, months from April to August resulting in significant Air conditioned requirement. The annual consumption of electricity and diesel of the company are 594803.61 kWh and 14405.83 kWh and percentage contribution of the energy carriers were 97.63% and 2.37% from National Grid and AGO respectively which show that the company depended on the energy from electricity.

Energy End Uses
The energy simulation results of the building has represented that the total monthly energy consumption by space cooling was 37633 kWh, ventilation fans 3070 kWh, factory machineries 53600 kWh, heat rejection is 5040 kWh, pump and auxiliary is 3000 kWh and area lighting 35821 kWh respectively having a sum total of monthly energy consumption by the end users to be 138164 kWh. This represent an annual energy use in air-conditioning (space cooling) was 27%, ventilation fan 2%, factory machineries 39%, heat rejection is 4%, pump and auxiliary is 2% and area lighting 26% ( figure 4). Also, the total monthly peak demand by space cooling was 22372.2 kWh, ventilation fan 1376 kWh, factory machineries 14294kWh heat rejection is 4461 kWh, pump and auxiliary is 1343 kWh and area light 11023 kWh respectively having a sum total monthly peak demand by the end users to be 44969.2 kWh. This represent energy use in air-conditioning (space cooling) was 41%, ventilation fan 3%, 26% factory machineries, heat rejection is 8%, pump and auxiliary is 2% and 20% area light of the annual peak demand.

Energy Conservation Measures
Based on the evaluation/analysis of energy consumption pattern of the company, several energy conservation measures (ECMs) were analyzed and these were categorized into three groups of no cost, low cost and major cost investment measures.
A. No Cost Measures These are measures that can be implemented through operational and behavioral means without the need for system or building alteration and, therefore do not require extra cost for their implementation [11]. For the company, the following measures were identifying for implementation. That is by applying schedule of equipment, set point temperature, infiltration and schedule of lighting.
Encourage Energy-Saving Behavior A number of buildings are successfully using no-cost public awareness campaigns to reduce energy use. One popular and effective-energy awareness program is the Dorm Energy Challenge, in which residence halls compete against one another to make the largest energy reductions or simply to improve their own energy performance. This strategy can be adopted in this company in order to save energy.
B. Low Cost Measures These are measures that can be implemented for building alterations or modifications through low cost investment.
i. Use of Energy Management Device Based on Image Processing The lighting and power supply can be controlled by occupancy sensing. The feature of this device is that it controls the power supply of any place by sensing occupancy by any human. The distinguishing feature is that only human occupancy is detected. This device uses image processing and pattern recognition. This device is found to be an efficient method to implement energy management at a low cost. The Management should endeavor to install an automated occupancy sensor everyway in the company.
ii. Effective Metering system Installation of pre-payment meters in the company, to monitor/curtail power wastages and thereby reduce energy cost on electric power.

Conclusions
The electricity energy consumption pattern of tannery company buildings was investigated and the following conclusions were drawn: a) The consumption pattern showed distinct seasonal variation indicating peak electricity demand during the hot season from April to August resulting in significant Air conditioning requirement. Also, 2. c) The company building was modeled and simulated using eQUEST-3.65 to investigate the building energy performance. Results shows that the sum total of the total monthly energy consumption by the end users is 138164 kWh representing the total average value of the annual energy use in air-conditioning (space cooling) was 27%, ventilation fan 2%, factory machineries 39%, heat rejection is 4%, pump and auxiliary is 2% and area lighting 26%. Also, the total monthly peak demand by space cooling was 22372.2 kWh, ventilation fan 1376 kWh, factory machineries 14294kWh heat rejection is 4461 kWh, pump and auxiliary is 1343 kWh and area light 11023 kWh respectively having a sum total monthly peak demand by the end users to be 44969.2 kWh. This represent energy use in air-conditioning (space cooling) was 41%, ventilation fan 3%, 26% factory machineries, heat rejection is 8%, pump and auxiliary is 2% and 20% area light of the annual peak demand.

Recommendations
Based on the conclusion of this research work, the following recommendations are made for the existing building in company. a) Creation of Energy Management Units in the company system to educate staff switch off the lights directly at the end of the day or when not in use.
b) The company management should implement an automated lighting system, which helps in switching off street lights automatically during the day. c) Use of high efficient equipment: High efficiency equipment reduces the energy needed to deliver a given level of energy services or produces more energy service per unit of energy. A careful observation shows that space cooling misc. equipment and area lighting were items which consumed the bulk of the energy supplied to the company, thus flagged areas for potential improvement of efficiency. d) Reducing energy use for lighting: Energy use for lighting in company can be reduced by appropriate window design and glass to make maximum use of daylight while avoiding excessive solar gain. Energy efficient lighting systems (e.g. using task lighting) to avoid excessive background luminance levels. 9941