Hydraulic Services Systems - Coursework Example

1.0. Introduction Water heating systems constitute 10% of the fuel consumption in commercial setups translating to an energy consumption of approximately 0.8 quads. Restaurants, hospitals, lodgings, and hotels record the highest amount of fuel consumed by commercial premises. The high cost of electricity in comparison to natural gas limits the utilization of electricity as a source of energy to power water heating systems (Buoro, Pinamonti, and Reini). Contractors, builders, and architects have a unique role in influencing the efficiency and performance of hot water systems for both existing and new buildings. However, it is important to note that existing buildings present a greater challenge hence the need for more aggressive strategies in redesigning the installed hot water systems in order to harness their efficiency. Nevertheless, the focus on the hot water load remains inevitable despite the fact that it may lower the efficiency of the water heaters (Dupeyrat, Ménézo, and Fortuin). 2.0. System descriptions: There are two systems considered under the present review namely the hot water system and the solar water heating system. The subsequent sections provide a detailed review of the system features for the two systems, their installation considerations, commercial applications, and comparative features. 2.1. Hot water systems Re-circulating loop and storage tank systems represent the widely applied technology on water heating in the commercial sector. Typical re-circulating loop hot water systems also possess a tank used for water storage. In order to reduce the hot water waiting time at the use points or faucet, the system continuously pumps hot water around its distribution loop thus providing instant hot water on demand by the users. On this note, the re-circulating loop hot water systems are associated with heat loss along the distribution loop hence the need for periodic re-heating in order to maintain the water temperatures (Wu et al.). On the other hand, tankless hot water systems are useful in reducing standby losses that are prevalent with water heating systems. Japan and Europe constitute the major markets for tankless water heating systems with the United States and Australia progressively adapting the technology. Nevertheless, advancements in flow technologies have reduced the adoption of tankless water heating systems in both commercial and residential applications (Lund et al.). An optimal hot water system consistently and quickly delivers hot water irrespective of the variations in climatic conditions and load using minimal energy with the least possible amount of water wastage. It is important that hot water systems promptly deliver hot water as an attribute of high performance. However, some systems become overwhelmed when the demands for water exceed the capacity of the system over short durations of time. The performance of hot water systems depends on the building design, distribution systems, usage characteristics, type of water heater, and climatic conditions (Hofmann, Babadagli, and Zimmermann). 2.1.1. Components of hot water systems The tankless hot water systems comprise of heating elements whose activation depends on the water flow particularly when there is demand for hot water. The heating of the water instantly takes place as it flows through the system based on the demand at a given time. The system does not store hot water to meet the anticipated demand hence no storage tank installed. The system has modifications depending on the energy source to cater for both natural gas and electricity (Kilpeläinen et al.). In the electric model of the hot water system, the heating elements are in direct contact with water thereby allowing for the direct transfer of converted heat energy from electrical energy. The heating process takes place as water flows through the system and automatically stops upon halting the water flow. Gas-based hot water systems have heat exchangers for transferring heat from heated gases in a combustion chamber. The system requires a supply of combustion air as well as an exhaust vent to expel flue gases (Dupeyrat, Ménézo, and Fortuin). Figure 1: Centralized hot water system for a large building 2.1.2. Design considerations and recommendations Lack of optimal performance of a hot water system reflects failure in the consideration of the design, installation requirements, and the efficacy of the system components. Before installation of a hot water system, it is important to consider the building’s architecture, the anticipated load, as well as use point characteristics, type of water heaters, distribution systems, and strategies for reducing the load (Hofmann, Babadagli, and Zimmermann). The design of a building provides invaluable information that guides the installation of hot water systems. General considerations include minimizing distribution of use points throughout the entire building. In addition, logically grouping use points as well as bathrooms vertically and horizontally reduces the distance to water heaters, and locating the water heaters at the center of the use points contribute to an optimal system (Ranger). 2.1.2.1. Location Location of the water heater centrally improves the waiting time for hot water and reduces wastage of water as well as the piping associated heat losses. Proper plumbing eliminates the requirement of a recirculation system by improving the waiting time for hot water. Installation of additional water heaters may be warranted by higher demands for hot water thus improving the system’s capacity (Wu et al.). 2.1.2.2. Peak Periods The amount of load especially during the peak periods is very important in the design of a hot water system. The system should have the capacity to satisfy the needs for hot water during the peak hours common when there are many simultaneous users, or high demands within a short timeframe. Addressing these issues leads to an optimal system that consumes minimal energy while meeting the hot water needs for the premises (Dupeyrat, Ménézo, and Fortuin). 2.1.2.3. Selection of the fixtures and appliances Selection of the fixtures and appliances also contributes to the efficiency of a hot water system. This is important because the type of fixture or appliance influences the hot water load of the system. Most of the existing appliances in both commercial and domestic premises such as faucets, showerheads, dishwashers, and clothe washers have inefficient water use or flow rates (Wu et al.). Distribution systems for the hot water systems are an important factor to consider during the installation process. In the recent past, plastic pipes have received a higher preference in distribution systems in comparison to the copper pipes. Plastic pipes are cheaper and require less skill during installation unlike the copper pipes that cost more in terms of raw materials and the installation costs. During installation of a distribution system, one should consider the length of pipes as well as insulating the pipes during installation in order to optimize the system (Dupeyrat, Ménézo, and Fortuin). 2.1.2.4. Temperature Characteristics The temperature of the supplied water depends on the heat losses associated with the distribution system. The volume occupied by the distance between the use points and the water heater’s location determines the minimum amount of water wasted by the system. Tankless hot water systems lead to a slightly higher amount of water loss because it discharges cold water for the initial 15-30 seconds before the heating peaks. It is also important to consider the human behavior associated with water losses especially when the system does not instantly discharge hot water when turned on (Hofmann, Babadagli, and Zimmermann). 2.1.2.5. Selection of Type of Water Selection of the type of water heater should take into account the maintenance requirements of the system. Tankless hot water systems require routine maintenance in order to preserve the heat exchanger’s performance. Sometimes the maintenance costs exceed the energy saving values translating to poor economics despite the energy savings. The water heater selected should have the capacity to synergize and conserve more energy at an effective cost (Dupeyrat, Ménézo, and Fortuin). Figure 2: Re-circulating hot water system 3.0. Solar water systems The abundance of free and clean solar energy continues to transform the market industry of water heating through the technology of the solar hot water system (SHWS). Solar water heating technology has attained maturity over the past decades with wide spread application in institutional establishments, commercial premises, factories, and homes. Indeed, the technology significantly reduces the amount of conventional energy utilized in various setups by providing clean and free energy alternatives. The last decade has seen the expansion of solar water energy solutions on the international markets (Buoro, Pinamonti, and Reini). Solar water heaters comprise of a collecting system that collects solar energy as well as an insulated tank that stores the water after heating. A solar energy incident situated on the panel’s absorber with special coating is responsible for heat transfer from the underneath riser pipes to the absorber panel. The water within the system undergoes re-circulation within the collector system through the absorber panel thus raising the water temperatures to a maximum of 800C (Herrando, Markides, and Hellgardt). Solar hot water systems fall under two broad classifications namely the open loop and the closed loop systems. In the open loop systems, either forced circulation or thermo-syphon systems, the system exposes the water to the atmosphere at some point during the heating process. Such systems are less expensive and easy to install hence ideal for small institutions or domestic use. In the forced circulation systems, electrical pumps propel the water through to the collectors and subsequently the storage tanks. On the other hand, closed loop systems comprise of installed heat exchangers thus protecting the system from elements of hard water drawn from boreholes as well as freezing temperatures associated with cold regions (Xu et al.). Various factors influence the decision of an ideal solar hot water system namely the amount of solar radiation, available space, fluid’s quality of heat transfer, weather conditions, and the amount of heat required. Generally, solar hot water systems are less expensive, do not cause air pollution, and very suitable for warm regions (Sadhishkumar and Balusamy). 3.1. Types of Solar water Heaters There are two types of solar water heaters depending on the collector systems used namely solar water heaters with the Flat Plate Collectors (FPC) and solar water heaters with Evacuated Tube Collectors (ETC). ETC based SWHs comprise evacuated glass tubes with a double layer of borosilicate for provision of insulation while the external wall of the interiorly situated tubes are coated with material possessing absorbing properties. This enables the system to absorb solar radiations and conduct it to the water flowing through the tubes. FPC based SWHs absorb radiations using an insulated metallic box with a glass sheet covering its top. The interior of the box comprises of selectively coated absorbing sheets that allow conveyance of water through the tubes (Sadhishkumar and Balusamy). Figure 3: Solar water system design 3.2. Design of Solar water systems There are two sub-categories of solar systems on the basis of active heating fluid namely the drainback solar heating system and the pressurized solar heating system. In the drainback model, the system pumps water through its collectors as well as heat exchangers during the day and flows back to a small tank for storage at night. The pressurized type circulates an antifreeze solution that is non-toxic through its collectors as well as the heat exchangers before passing it to the water. The basis of the two systems dictate various design requirements that should be adhered to in order to set up an optimal system (Xu et al.). 3.2.1. Installation of Solar Water Systems Installation of a solar water system requires an un-shaded area preferably on the roof top thus providing uninterrupted supply of solar radiation. The number of solar panels to be mounted depends on the requirements for hot water within the commercial premises. Installation as well as maintenance costs depend on the nature of the roof and its accessibility. Very stiff and tall roofs may require the use of a crane in order to access the installation site of the panels. In some cases, need may arise to dismantle the collectors before transferring them to the installation site (Herrando, Markides, and Hellgardt). 3.2.2. Plumbing options For Solar Water Systems Plumbing options for the solar hot water system will depend on the pH, iron content, and hardness of the water since these determine the longevity of the plumbing material. Water with a high content of iron may cause the instantaneous heat exchangers to foul prematurely. Hence mechanisms should be installed for treating the water and bringing it within the normal limits in order to have an optimal system. Solar pipes within the drainback system require a continuous slope hence the need for adequate planning before plumbing (Padovan and Manzan). 3.2.3. Wiring options for the solar water heaters Wiring options for the solar water heaters are also important considerations for the heating system and these greatly depend on the anticipated load. The system may be installed in such a way that the pump receives power from a single panel, or integrated with the entire system for a common power source. Installation of a backup power source also influences the wiring requirements of the solar hot water system (Xu et al.). Finally, installation of the solar hot water system should consider the appropriate mounting of the collectors. In most cases, mounting of the collectors is done on the rooftops although they may be flashed into the finished roofs. Mounting the collectors on the rooftop allows them to stand off on feet that are bolted down. Need may arise to support the collectors in large arrays using aluminum frames (Padovan and Manzan). 4.0. Commercial applications of hot water and solar hot water systems Tankless hot water systems have been extensively applied in commercial set-ups that require a continuous supply of hot water. The demand for hot water in commercial premises ranges from minimal hot water demand to very high demands. For instance, hospitals and hotels have higher requirements for hot water while offices and small retail centers have lower hot water requirements. Some tankless hot water systems have very large capacity with a hot water flow rate of up to 80 gpm hence ideal for specialized industrial processes (Wu et al.). In commercial set-ups with an occasional hot water demand, tankless hot water systems are efficient as point-of-use-installations. This is beneficial because of the minimal heat losses that the system offers in comparison to the re-circulating loop systems. Figure 4: The Hilton Hotel in Australia has an integrated hot water system that supplies hot water to the swimming pool and other distribution points In Melbourne, hot water systems and solar water heating systems have been widely applied in a variety of industries including dairy farming, chemical treatment plants, as well as pre-heating systems. Some of the premises with water heating system installations include hospitals such as St. vincents Private Hospital, The Alfred Hospital, and the Royal Melbourne Hospital. Hilton Melbourne South Wharf, Hotel Windsor, and Radisson on Flagstaff Gardens Melbourne represent some of the hotels with hot water system installations. Wineries such as Crush Wines Distribution Pty Ltd, Panton Hill Vineyard & Winery, and Yarra Valley Winery Tours also have solar water heating systems. Finally, refineries in Melbourne have also embraced the hot water system technology including the refinery Post Production Services, 888 Refining Australasia Pty Ltd, and Mobil Altona Refinery. Figure 5: Solar water heating system in New South Wales 5.0. Comparison between solar water systems and hot water systems The two systems generally vary in reference to the costs associated with their installation and maintenance. Generally, hot water systems are more expensive compared to solar water heating systems. Solar energy is freely available as opposed to electric energy used in hot water systems. Nevertheless, the cost for electricity used in powering the hot water systems is marginal and available regardless of the weather conditions unlike solar energy. This makes the electric hot water system is more reliable regardless of the weather conditions especially in places where there is limited access to sunlight. In both systems, the consumption patterns for hot water on a daily basis do not significantly influence the electricity savings. Hot water systems save maximum energy during winters whereas the solar water heating system saves maximum energy during summer. In regards to annual savings for electricity, both systems save more energy when the hot water demand is higher. 6.0. Conclusion The choice of a water heating system depends the water requirements of a commercial premise, the installation as well as maintenance costs, the source of energy to power the system, the anticipated load on the system, and the user behaviors of premise occupants. This information is very crucial when designing and installing the preferred water heating system. Installation of hot water systems should be integrated with the architectural designs of the building in order to have an optimal system. 7.0. References Buoro, Dario, Piero Pinamonti, and Mauro Reini. “Optimization of a Distributed Cogeneration System with Solar District Heating.” Applied Energy 124 (2014): 298–308. Print. Dupeyrat, Patrick, Christophe Ménézo, and S. Fortuin. “Study of the Thermal and Electrical Performances of PVT Solar Hot Water System.” Energy and Buildings 68 (2014): 751–755. Print. Herrando, María, Christos N. Markides, and Klaus Hellgardt. “A UK-Based Assessment of Hybrid PV and Solar-Thermal Systems for Domestic Heating and Power: System Performance.” Applied Energy 122 (2014): 288–309. Print. Hofmann, Hannes, Tayfun Babadagli, and Günter Zimmermann. “Hot Water Generation for Oil Sands Processing from Enhanced Geothermal Systems: Process Simulation for Different Hydraulic Fracturing Scenarios.” Applied Energy 113 (2014): 524–547. Print. Kilpeläinen, P. O. et al. “Pressurized Hot Water Flow-through Extraction System Scale up from the Laboratory to the Pilot Scale.” Green Chemistry 16.6 (2014): 3186–3194. Print. Lund, Henrik et al. “4th Generation District Heating (4GDH): Integrating Smart Thermal Grids into Future Sustainable Energy Systems.” Energy 68 (2014): 1–11. Print. Padovan, Roberta, and Marco Manzan. “Genetic Optimization of a PCM Enhanced Storage Tank for Solar Domestic Hot Water Systems.” Solar Energy 103 (2014): 563–573. Print. Ranger, Gary C. Hot Water Supply System. Google Patents, 1993. Google Scholar. Web. 3 Apr. 2017. Sadhishkumar, S., and T. Balusamy. “Performance Improvement in Solar Water Heating systems—A Review.” Renewable and Sustainable Energy Reviews 37 (2014): 191–198. Print. Wu, Wei et al. “Simulation of a Combined Heating, Cooling and Domestic Hot Water System Based on Ground Source Absorption Heat Pump.” Applied Energy 126 (2014): 113–122. Print. Xu, J. et al. “Performance Investigation of a Solar Heating System with Underground Seasonal Energy Storage for Greenhouse Application.” Energy 67 (2014): 63–73. Print.  Read More