INDUSTRIAL ENERGY SYSTEMS
Industrial Energy Systems
Executive summary
Energy is an essential input in any industrial process. Energy in industries is used in virtually every stage of the production process. Therefore, production cannot take place without energy and the cost of energy influences the final cost of the product. As a result, there is an energy component in the final cost of the product. To ensure competitiveness in a free and unregulated economy, producers must reduce the prices of their products to levels below that of the competition. To achieve lower product prices, the usage of energy in the production must be reduced or replaced with cheaper energy forms such as renewable energy (International Renewable Energy Agency 2014). Minimization of energy consumption involves undertaking a comprehensive energy audit aimed at identifying areas of inefficiencies, making recommendations to remedy and mitigate the inefficiencies, and implementing the recommendations.
In industrial plants, electrical energy is used to run electric motors, pumps, heaters, lamps, and the control equipment. Also, fossil fuels such as diesel are used to run heavy industrial engines and fire boilers. When energy is applied into an industrial process, it’s converted from one form to another such as from electrical to mechanical. The amount of energy consumed in a process and per unit of product produced depends on the efficiency of the appliance used in the production process. Efficient appliances convert a high percentage of the applied energy to the required form while inefficient devices convert a large amount of the applied energy to unusable forms such as waste heat. Also, energy efficiency reduces the strain on the energy infrastructure. In the United Kingdom, 20% of the total energy in the country goes to support industrial processes (De Montfort University 2009). Therefore, energy efficiency in in the country would lead to economic development as fewer resources will be used to expand and maintain the infrastructure. This report presents an energy audit of a vegetarian pie manufacturing plant built in the 1970s. The report will identify areas of inefficiencies and recommend remedial measures.
Figure 1: Schematic diagram showing the flow of energy in a manufacturing plant. Source: De Montfort University, 2013.
Figure 2: Pie chart showing energy consumption pattern in a typical industrial plant. Source: De Montfort University, 2013.
A vegetarian pie is an animal-products-free pie made from an assortment of vegetables and other grocery products and wheat. The production process involves cooking and baking these raw materials in moderate conditions to achieve a nutritious pie rich in plant products (Delicious n.d.). The pies are designed in different shapes and with different components to attract customers such as the one shown in figure one below.
Figure 3: A kales, chestnut, and mushroom pie. Source: Delicious Magazine
The equipment used to cook the pies is powered by oil fired boilers. Other equipment used in the plant include chillers, pie filling machines, cutters, and conveyer belts which are all electrical powered.
The boiler
Figure 4: A cut-away diagram of an oil fired boiler. Source: Feedwater.co.uk
Boilers burn a fossil fuel known as heavy fuel oil and the chemical energy in the fuel is converted to heat energy. The heat energy produced is then used to heat up water which evaporates thereby forming steam. Lagged conduits then pick up the steam and channel it to the point of application such as steam cookers. Burning of the fuel oil produces smoke rich in carbon dioxide and small amount of carbon monoxide, both of which are greenhouse gases (Kitto 1996). To control the accumulation of greenhouse gases in the atmosphere, energy efficiency is observed. Consumption of less energy reduces the carbon footprint of the plant making it more environmentally friendly (International Energy Agency 2007).
When the fuel oil is introduced to the burner in the boiler furnace, it’s mixed with oxygen and ignited by sparks from an ignition device. Heat generated in the combustion chamber is transmitted to the water in the boiler through a heat exchanger. The resulting steam is directed to the heating load and then condensed and circulated through the system again by pumping it to the boiler as feed water. The flow of energy is as shown in figure 1 below.
Figure 5: Abstraction of energy and water flow through a boiler
Boiler efficiency is given as the ratio of the amount of heat supplied to the water in the heat exchanger to the amount of heat supplied by the fuel. Therefore, the efficiency is determined by the furnace design and the nature of the heat exchanger. An efficient furnace design should enable complete burning of the fuel to ensure low or little energy wastage. Such a furnace design has to ensure combustion of all fuel matter to prevent un-burnt gases from escaping as exhaust. Also, the entire furnace should be lagged to prevent heat loss to the atmosphere. Heat exchangers are responsible for the transfer of heat from the furnace to the boiler water. There are two types of boilers, fire tube and water tube boilers. Fire tube boilers have hot flue gases confined within tubes while the water occupies the rest of the space in the heat exchanger. Conversely, water tube boilers have water confined in tubes which are surrounded by the hot flue gases (Atta n.d.).
Chillers
Industrial chillers are used to keep products cools to prevent damage from microbial microorganisms. Chillers are electrically powered and operate around the clock. An inbuilt thermostat toggles the chiller between an on and off state depending on the temperature levels within the chiller. In chillers, electrical energy is converted to mechanical energy which is then used to compress the glycol refrigerant. The potential energy in the compressed glycol is used for cooling when the refrigerant evaporates (Smith, n.d).
Motors
Electrical motors are used to run conveyer belts in industrial plants and operate other machinery such as mixers, cutters and lifting cranes among others. Motors convert electrical energy to mechanical energy through electromagnetic induction. The rotation of the motor shaft creates a torque which is then applied to do work.
Energy saving opportunities in the vegetarian pie factory
Lowering boiler oil consumption
Typically, oil consumption in a boiler is determined by the hours of operation and the heating load. However, automated controls and efficient boiler design can be used to lower fuel consumption. Since the boiler was fabricated and installed in the 1970s when automated control systems such as supervisory control and data acquisition (SCADA) systems were non-existent, then its efficiency can be expected to be very low. Also, the old technology coupled with years of operation and subsequent degradation might have lowered its efficiency. Automatic control system regulates the operation of the boiler such that the fuel burnt in the furnace supplies just the required heat. Also, the control equipment stops the operation of the furnace when no load is applied on the boiler (Shankar 2008). Other measures that can be applied to economize consumption include preheating of the feed water using the exhaust flue gases through the use of devices known as economizers (Energy Solutions Center 2003).
Use of variable speed drives to control motor speed
Variable speed drives are devices that regulate the torque and speed output of synchronous motor by reducing the voltage and frequency if the power from the mains (Turkel 1999). A synchronous motor runs at full speed and torque even at no load conditions leading to wastage of electrical power. To lower electrical power consumption in synchronous motors, variable speed drives are used to regulate the motor speed and torque in line with the loading thereby conserving energy. Reducing electrical energy consumption also reduces the plant’s carbon footprint.
Use of renewable energy in the plant such as solar energy
Solar energy can be used to complement the grid supply and fossil fuels in applications such as water heating and powering electrical devices (De Montfort University 2010). Solar energy, being a renewable form of energy, is inexhaustible and free. Solar photovoltaic panels convert electromagnetic radiation in sunlight to electricity. This electrical energy can be used to power light electrical loads such as lighting systems, roof fans, and small air conditioning systems. Also, solar water heaters can be used to preheat boiler feed water before it’s fed into the boiler, which would drastically reduce the fuel consumed by the boiler and raise its efficiency (Kalogiroua & Tripanagnostopoulosb 2007).
Conclusion
Energy is an essential input in a production process as all industrial activities involve the use of energy in one way or the other. The cost of energy is manifested in the price of the final product produced in a manufacturing plant, therefore, it essential that its consumption is maintained at the lowest point possible. Low energy consumption ensures competitiveness of a business and hence it’s financial success. In a vegetarian pie manufacturing plant, energy is used to fuel boilers, run conveyor belt motors, pumps, and cutters among any other devices. The boiler in the plant is fired by heavy fuel oil and possible areas of energy conservation include automation, lagging, and improvement of the furnace design. Also, a solar water heating system can be used to preheat the feed water to raise the boilers efficiency and lower fuel consumption. Variable speed drives can be used to lower energy consumption in motors by aligning speed and torque output with the loading done on the motor. Implementation of variable speed drives, solar water heaters, and optimization of the boiler design will lead to energy savings in the pie manufacturing plant.
References
Atta, T. n.d. Difference between Fire tube boiler and water tube boiler. [Online] (updated 2016) Available at: http://www.green-mechanic.com/2014/08/difference-between-fire-tube- boiler-and.html [Accessed 21 Feb. 2016].
Delicious, n.d. Vegetarian pie recipes. [Online] ( updated 2016) Available at: <http://www.deliciousmagazine.co.uk/collections/vegetarian-pie-recipes/>[Accessed 21 Feb. 2016].
De Montfort University. 2013. Lesson 2.2: Manufacturing Processes.
De Montfort University, 2010. Lesson 2.1 Materials extraction and primary processing.
De Montfort University, 2009. Lesson 1.1 Industrialisation and Energy.
Energy Solutions Center. 2003. Economizers. [Online] (updated 2007). Available at: <http://www.cleanboiler.org/Eff_Improve/Efficiency/Economizers.asp>[Accessed 22 Feb. 2016].
Feedwater.co.uk. n.d. Industrial Boiler Types. [Online] (updated 2016) Available at: < https://feedwater.co.uk/industrial-boiler-types/>. [Accessed 21 Feb. 2016].
International Energy Agency, 2007. Tracking Industrial Energy Efficiency and CO2 Emissions.
International Renewable Energy Agency. 2014. Renewable Energy in Manufacturing. [Online] (updated 2016). Available at: <http://irena.org/remap/REmap%202030%20Renewable- Energy-in-Manufacturing.pdf.>[Accessed 22 Feb. 2016].
Kitto, J., 1996. Air Pollution Control for Industrial Boiler Systems. [Online] (updated 2016) Available at: http://www.babcock.com/library/Documents/br-1624.pdf. [Accessed 21 Feb. 2016].
Shankar, K. 2008. Control of Boiler Operation using PLC – SCADA. [Online] (updated 2016) Available at: <https://www.idc- online.com/technical_references/pdfs/electrical_engineering/Control_of_Boiler_Operatio n_using_PLC%20-%20SCADA.pdf. > [Accessed 22 Feb. 2016].
Smith, R., n.d. Chillers Save on Energy and Water Consumption. [Online] (updated 2016) Available at: < http://www.airbestpractices.com/sustainability-projects/water- conservation/chillers-save-energy-and-water-consumption> [Accessed 21 Feb. 2016].
Turkel, S., 1999. Understanding Variable Speed Drives (Part 1). [Online] (updated 27 Aug. 2012) Available at: <http://ecmweb.com/content/understanding-variable-speed-drives- part-1> [Accessed 2 Feb. 2016].
Kalogiroua, S. & Tripanagnostopoulosb, Y., 2007 Industrial application of PV/T solar energy systems. Applied Thermal Engineering, 27 (9), pp. 1259–1270
Appendix
Figure 6: A water tube boiler. Source: green-mechanic.com.
Figure 7: A fire tube boiler. Source: Source: green-mechanic.com.
Figure 8: Schematic illustration of a chiller system. Source: airbestpractices.com
