It is estimated that the average SME could reduce its energy bills by 18 – 25% by adopting energy efficiency improvement measures with an average payback period of less than 1.5 years. It is also estimated that 40% of these savings do not require any capital investment (UK Department of Energy & Climate Change, 2015). In this section, some best practices and guidelines for energy footprint reduction of SMEs are presented. The proposed measures could be simple and cheap (or even free of charge) or more complex and costlier. They could refer to different sections or aspects of the enterprise operation.
There are various simple measures related to operational and maintenance activities that can be implemented within SMEs to improve their energy efficiency (Fawkes et al., 2016; Fernandes et al., 2016):
- Maintenance activities should be carried out by specialized and experienced technical staff. There should be sufficient time to complete the relevant maintenance work according to relevant quality standards. Following a maintenance routine and a mid-term schedule is of outmost importance. In the case of replacement activities, the spare parts to be used should be the most modern and efficient ones.
- In the case of recurring plant failures, it should be ensured that the root causes are identified. For this purpose, experiments and tests should be conducted and everyone must contribute to uncover them. It is very important to ensure that any root cause should be addressed effectively without causing another failure elsewhere in the facility.
- During the installation of new equipment or machinery, it must be ensured that all the relevant parts and components are installed properly following the guidelines of the manual(s) provided by the manufacturer. Additionally, the actual installation should be reviewed carefully before handover in order to ensure that it is as per design.
- Regarding equipment size, it should be ensured that equipment specifications meet the operational requirements and match the actual demand without excess capacity.
- Regarding equipment operation, it should be verified that the relevant machinery can be turned off easily and safely when it is not being used. Facility and equipment safety rules should be strictly There should be safety valves and appropriate protective devices that ‘guarantee’ the safety of the facility and the installed machinery. The ability also to restart facility’s operation at short notice is very important for achieving improved energy efficiency.
- If there is a variety of available machines one should choose to use the ones that exhibit the highest efficiency. It is evident, therefore, that production managers supervisors, and/or staff should be aware and have good knowledge of the minimum, normal and maximum operating conditions of all the available equipment.
- Production processes should be designed in such a way so as to minimize idle time of machinery. Also, there should be an effort to stop machines’ operation as soon as possible and start them as late as possible. Production processes should be carefully monitored and reviewed aiming at identifying potential for efficiency improvement.
- It should be ensured that all thermal and electrical insulation is in good condition minimizing heat losses and eliminating electricity leakages.
There may be significant energy saving potential for enterprises in the buildings they occupy. The importance of monitoring in the energy management of buildings has already been analysed. Improving the building fabric via the application of appropriate thermal insulation leads to a reduction of heat losses, thus, helping to achieve considerable energy (and operational cost) savings. Such a solution could be sometimes quite costly and labour intensive. Nevertheless, there are various simple and low cost measures that can enhance the energy efficiency of existing buildings (Fawkes et al., 2016; IPCC, 2006):
- Windows present a common source of heat losses in buildings. For that reason, their frames should be regularly checked and maintained in good condition in order to ensure that they can be closed tightly and are draught-proof. Single glazed windows should be replaced with double or, if it is possible, with triple glazed ones. The application of proper shading systems could also prevent building spaces from over-heating.
- Like windows, doors could also be tested in order to ensure that they are draught-proof and can be closed tightly. The replacement of the existing doors with thicker ones and the implementation of self-closing mechanisms could also help to control the temperature of internal spaces consuming less energy.
- Walls and roofs should be regularly checked in order to spot existing gaps or holes which should be repaired/closed applying appropriate filling materials. Additionally, dedicated audits could be carried out in order to explore the potential of reducing thermal losses through the application of proper thermal insulation.
Improving and/or modifying HVAC systems could contribute significantly to achieving energy efficiency in office buildings, production plants and other facilities of SMEs. HVAC systems should be properly regulated in order not only to ensure appropriate comfort and health living conditions for the staff of the organization, but also to minimize its energy consumption. The main parameters that should be monitored and controlled are: humidity, temperature and air quality. Some simple and practical measures that ensure good and efficient operating conditions of HVAC systems include (Fawkes et al., 2016; UK Department of Energy & Climate Change, 2015):
- Appropriate control systems that regulate room temperature should be employed. Office temperature, for instance, during winter months (heating operation) is recommended to be set to 19°C. Obviously, it could be set lower than 19°C in corridors, storerooms and areas of higher physical activity. In the summer (cooling operation) the corresponding air temperature is recommended not be lower than 24°C. Regarding cooling temperatures, there is an empirical rule according to which an increase of the set cooling air temperature by 1°C will result to an increase of energy consumption of the order of 3% by the chiller.
- Cooling systems release/reject heat to the environment, namely to ambient air. It is evident, therefore, that in order cooling systems to operate efficiently, they should have good and unobstructed access to ambient air. Thus, the positioning of cooling units with respect to existing furniture, equipment and/or machinery is very important. Space restrictions and/or poor engineering judgment might result in positioning cooling units close to hot air exhausts or in a way that they have restricted ambient air flow, inevitably lowering the overall efficiency of the system. Facility space arrangement should cater for cooling systems to have unobstructed access to the coolest possible ambient air.
Simple measures, techniques and technologies could be applied in order to reduce the energy consumed by lighting systems. The most common and efficient measures are presented and discussed below (Fawkes et al., 2016; The Business Case for Power Management | ENERGY STAR, n.d.; UK Department of Energy & Climate Change, 2015):
- There are sensors and automatic devices that can identify human presence in a room/space of a building or a facility. Such devices could be deployed to turn on the lights of the corresponding room/space only when the room/space is occupied.
- There are standards and norms that specify the lighting level in a room/space according to the activity that is being carried out in the room/space. In order to achieve energy savings over-lamping should be avoided.
- All incandescent lightbulbs should be replaced by more energy-efficient LED lighting in order to save energy.
- It is often highlighted that company spaces do not exploit to its full potential natural lighting. Designing spaces in such a way so as to use natural light from windows and/or skylights at its maximum, has almost no cost, mitigating at the same time electricity demand for artificial lighting. This is why objects that block windows, e.g., filing cabinets, should be relocated, while the space arrangement should always aim at maximizing the use of natural light, e.g., working desks should be positioned near windows.
Improving water quality in industrial SMEs is very important. Water in liquid state or in its gaseous state, i.e., steam, is commonly employed to carry and transfer heat within a plant, equipment, thermal devices, etc. Water is not pure; it contains various elements such as mineral salts, dissolved organic matter, and microbiological organisms. Although the quantities of these elements in water are minute, they adversely affect water properties and the operational efficiency of thermal equipment and devices of a production plant. It is imperative, therefore, to control and monitor water quality closely. Including regular water testing in maintenance schedules of SMEs could ensure improved quality of feed water into boilers and a reduction in energy consumption, and in water purchase and treatment bills (Fawkes et al., 2016).
Various simple and affordable measures/actions to achieve energy savings have been already presented. Nevertheless, the highest energy efficiency improvements could be achieved through extensive changes related to process design and/or energy supply. Compared to simpler measures, extensive changes are always associated with high (investment) cost and the corresponding high business/financial risk. Such changes might include the implementation of appropriate CHP plants, the redesign of production lines and/or procedures, the application of sophisticated prediction, simulation and control techniques, and the connection of the facility to the local heating or cooling network to channel waste energy or heat (Zhang et al., 2021).
Renewable sources and energy storage
SMEs have a high potential for the installation of on-site rooftop solar PV systems. Both for the manufacturing and services sectors, as much of the relevant processes are electrified, it is expected that their energy load demand could be matched with periods of high solar generation. Solar water heating could be also adopted as an alternative for heating or pre-heating. This allows water to be heated well above 80˚C. Additionally, onsite battery storage might be also worth considering as battery prices decline. Batteries enable not only a greater on-site exploitation of solar PV systems throughout the day, but they also provide a backup option in the event of grid failure. For the food and beverage sector, in particular, energy could be also stored thermally in water, phase changing materials, or in the bulk mass of food products in refrigeration (Food and Beverage | Energy.Gov.Au, n.d.; Royo et al., 2019)
Combined heat and power (CHP)
Conventional (thermo-electric) power generation technologies, exhibit relatively low fuel-to-power efficiencies, simply because considerable amounts of high-temperature heat are lost to the environment through the stack. This is the reason why common conventional (thermal) engines exhibit energy efficiency rates which do not normally exceed 38% – 40%. Specifically, energy efficiency rates for reciprocating engines are in the range of 28% – 38%. Energy efficiency rates of small gas turbines (nominal power up to 5 MW) vary between 20% to 25%, whilst the corresponding efficiency figures for bigger gas turbines (nominal power between 5 MW and 500 MW) are in the range of 25% to 35%. Modern gas turbine power plants with a nominal power higher than 500 MW might reach efficiency rates close to 50%. CHP technology captures and utilizes the thermal energy (heat) which is released (lost) to the environment. The captured thermal energy can be used to produce steam, which in turn can drive a steam turbine to generate electricity. At a smaller scale, CHP systems, industrial gas turbines or reciprocating engines fuelled by gas or oil are employed. Apart from electricity generation, the captured heat can be used in other thermal processes such as steam generation or water heating. Typically, the overall efficiency of CHP plants is much higher than the one exhibited by conventional power plants, namely of the order of 75% – 85% (Fawkes et al., 2016).
It is estimated that waste heat represents about 20% – 50% of the overall industrial energy consumption. This is because waste heat can be generated in several forms within an industrial SME, e.g., as hot exhaust gases, cooling water, or heat loss from equipment surfaces and heated components. All thermal industrial processes may reduce their heat demand by utilizing part of these heat losses, appropriately termed as recovered (waste) heat, employing heat (recovery) exchangers. The captured heat is commonly used to preheat the inputs to heat chambers reducing the overall energy demand of the relevant process. Recovered heat may be used by a neighbouring industrial facility. Currently, there are various heat recovery technologies available that can be implemented in industrial plants. In order this technological option to be successful, there should be an easily accessible source of waste heat and a relevant industrial or commercial heat demand to be satisfied, as well as the appropriate recovery technology. SMEs that intend to implement waste heat recovery technologies, should carry out special audits by appropriate staff and/or advisors in order to determine the requirements of their industrial facility and evaluate the technoeconomic feasibility of this solution (Fawkes et al., 2016; Jouhara et al., 2018).
Waste heat to power
The temperatures involved in production processes of certain industrial sectors might be above 1,000°C. Typical examples of such industrial sectors are steel and cement industries. Their corresponding waste heat generated is associated with temperatures reaching 750°C. In some other processes, such as CHP plants and boilers, waste heat might be available at considerably lower temperatures ranging between 160°C and 180°C. The generated waste heat can be converted to power, following the approach that is commonly known as Waste Heat to Power (WHP) technology. Different WHP technologies can be implemented depending on the temperature of the available waste heat. Waste heat available at high temperatures, for instance, is appropriate for the preparation of steam which may be used for electricity generation employing a steam turbine. On the other hand, waste heat available at relatively lower temperatures may be also used to generate electricity with a technology quite similar to the one of steam turbines. In this latter case, however, the working fluids to be used, should have a boiling point much lower than that of water. It is evident, therefore, that industrial SMEs that generate high temperature waste heat should certainly investigate WHP options in their effort to enhance their energy efficiency and reduce their energy footprint (Fawkes et al., 2016).
UK Department of Energy & Climate Change (2015) SME Guide to Energy Efficiency, Department of Energy & Climate Change.
Fawkes, S., Oung, K. and Thorpe, D. (2016) Best Practices and Case Studies for Industrial Energy Efficiency Improvement, Copenhagen Centre on Energy Efficiency. Copenhagen.