Energy Storage and Renewable Energy - Report Example

ENERGY STORAGE AND RENEWABLE ENERGY Student’s Name: Code + Course name Professor’s name University City, State Date Background and Summary The reduction in the cost of renewable energy has yielded optimism in the transformation of the industry. Apparently, the last few decades have witnessed an increase in the demand for storing energy. The rapid development of variable resources for energy storage has necessitated the need for accommodating the new resources. The fundamental aspects of energy storage encompass the need for ramping the rapid generation of energy, balancing the services and understanding the transformation of energy from an era of excessive supply to the current high demand period. Apparently, the demand for energy will exhibit an increasing trend over the next decades. Consequently, it is appropriate to encompass the storage of the generated renewable energy rather than consuming all the renewable energy produced. It is evident that there exist proper technologies to produce and store renewable energy for future utility. However, the development of other technologies is still underway to enhance the efficiency of the generation and storage of renewable energy. The principal rationale of the energy storage technologies entails storing the surplus energy during periods of low demand such as weekends and at night and availing the energy during periods of high demand such as during the day. There are other benefits associated with energy storage. They include reducing the emissions to the environment, enhanced flexibility of the capacity and improved power quality. Furthermore, the energy storage technologies have resulted in the development of non-wire technologies in the industry. Table of Contents Background and Summary 2 Technical Details 4 Literature Review 5 Mechanical 6 Electrochemical Energy 9 Chemical Energy Storage 10 High-Temperature Thermal Energy Storage 12 Combustion Turbine Inlet Cooling Storage 12 Electromagnetic Storage 13 Project Concept 14 Methods and Justification 14 Project Plan 14 Feasibility 15 Team Management 15 Conclusion and Recommendation 16 Reference List 17 Technical Details O&M – Operation and Maintenance CAES – Compressed Air Energy Storage MW – Megawatts GW – Gigawatts SMES – Superconducting Magnetic Energy Storage Literature Review The development and operations of electrical energy storage systems and renewable energy face significant challenges associated with synthesizing it with the entire power grid. The need for reducing the escalating rates of the carbon footprint in the atmosphere has compelled various individuals and organizations to devise ways of reducing the utility of fossil fuels as a source of energy. The utility of renewable energy sources such as solar, wave, hydro and wind has proven to take a center-stage towards the attainment of the objective. The energy service providers strive to ascertain that they use environmentally friendly sources of energy to meet the ever-increasing energy demands. Between 1995 and 2009, the installed wind capacity has exhibited a significant increase from less than 10GW in 1995 to approximately 150GW. By 2012, the total wind capacity in the United States was nearly 240GW. Being a green source of energy that does not pollute the environment, it is worth taking into consideration the intermittent and uncontrollable nature of wind power (Kintner-Meyer et al. 2011). It is evident that the other green energy sources such as solar and wave are also intermittent and uncontrollable. Therefore, in the quest for guaranteeing the sufficient supply of energy to the increasing demand for energy, it is imperative to adopt efficient energy storage technologies. Energy storage refers to the system that absorbs energy at one time so as to release it at a future time for its utility. The paper focuses on the storage of electrical energy. Apparently, the storage technologies convert electrical energy into a different form of energy so as to store it for future use. The interim storage medium determines the storage technologies. Figure 1 below shows the classification of the energy storage technologies. Figure 1: Classification of the energy storage technologies An efficient energy storage system also requires control systems and intermediary communication that allows the operators of the storage systems to interact with the storage resources. It is proper to opine that energy storage and generation systems exhibit significant similarities. However, there exist significant differences that distinguish the two systems of generating and storing renewable energy. For instance, an energy system that permits the timing of the consumption of the energy suffices to be a storage system. The systems allow the operator to vary the timing of the energy consumption. Some of the energy storage technologies encompass: 1. Mechanical 1.1 Pumped Hydro Storage The pumped storage suffices to be the most used energy storage technology. It boasts of a global capacity of 129GW with the US systems accounting for 22GW. It is evident that the versatile nature of the technology allows the operators to vary the supply of energy to the different hours of the day. The operation of the technology entails the pumping of water from a lower reservoir to an upper one using electricity during instances of low power demand. When the demand is high, water flows from the upper reservoir through the turbines to recover the energy. The economic lifespan of the technology is in excess of 50 years. They also require less O & M and do not exhibit cyclic degradation. However, the siting requirements of the technologies should be specific. The installation of the reservoirs and the production plant is also costly. The storage system installed in the US serves as a peak shaving and load leveling energy management tool. The system also portrays an efficiency of between 70 and 85%. 1.2 Compressed Air Energy Storage The CAES technologies consist of electric motors that run thus compressing air into enclosed volumes. To recreate the electrical energy, the system operators feed the compressed air into combustion air turbines. Even though the combustion turbines utilize some fossil fuels in the operation, the amount of electrical energy produced trebles that of the conventional gas turbines. There exist two main types of the compressed air combustion turbines. The Germany's 321MW generator, 60MW compressor, 4-hour discharge and the Alabama's 110MW generator, 50MW compressor, 26-hour discharge (Vasconcelos et al. 2012). The US Energy Department, the Pacific Energy and Electric and EPRI are working on the development of a 300MW CAES plant with a storage capacity of 10 hours. The CAES units exhibit energy efficiencies of between 40-75%. The start-up phase of the units requires five to 15 seconds with a ramp-up rate of 20% for every 60 seconds in the charging mode and 10% for every 3 seconds while discharging. Initially, the heat that results from the compression of air gets lost to the environment. However, the modern CAES systems intend to capture this heat so as to increase the energy yield of the system. Rather than losing the heat to the atmosphere, the engineers plan to design the system such that the heat heats up the air as it passes through the inlet of the combustion turbine. The steady and slow compression of air is the other solution to preventing heat loss during compression. By so doing, the air maintains approximately equal temperatures during both compression and expansion procedures. Over-the-ground storage tanks and underground caverns both serve to store the compressed air. 1.3 Flywheels The operation of the flywheels in storing energy entails speeding up the rotors. The inertial masses rest on magnetic bearings that exhibit very little friction. The placement of the rotors in evacuated chambers also serves to reduce the friction. The motor-generator rotates a shaft connected to the rotor thus allowing the transfer of energy in and out. Apparently, the inertial masses are the primary component of the flywheel. The major attributes of the rotors (maximum rotational frequency and frequency) determine the density and the energy capacity of the rotors. On the other hand, the power electronics and the motor generator determine the flywheel’s maximum power output. Consequently, it is possible to decouple energy capacities and power of the flywheel. The power of the flywheels ranges between 100kW to 2MW with the discharge times varying from five seconds to 15 minutes. 1.4 Other Technologies The other mechanical storage technologies for renewable energy include lifting masses using hydraulic fluids, floating buoyant masses using water, and using rail cars to haul stones. 2. Electrochemical Energy 2.1 Conventional Battery Technology The technology converts electrical energy into chemical energy for storage; then reconverts the chemical energy to electrical power for utility. In a standard battery, an electrolyte separates the cathode and anode electrodes. The charging phase entails the ionization of the electrolyte. The oxidation-reduction reaction in the discharging phase recovers the energy. The lead-acid, lithium-ion and nickel-cadmium are some of the battery types used to store electrical energy. 2.2 High-Temperature Batteries They are also referred to as molten-state batteries. They exhibit similar characteristics as the conventional batteries only that the reactions occur at elevated temperatures. Sodium nickel chloride and sodium Sulfur are the major examples of the cells. The operating temperatures for NAS range between 300oC and 360oC. The operating temperature for Sodium Nickel Chloride is approximately 270oC. NAS batteries are appropriate for power and energy applications that require longer durations of energy storage. Such applications encompass renewables output smoothing, “islanding”, arbitrage and load leveling. They can provide pulse power besides having a response time of 1ms. They exhibit a general efficiency of between 70 to 90%. The discharge capacities of the batteries range between 50kW to 100MW. However, maintaining the cells in the molten state reduces the energy output to some degree (Schoenung & Hassenzahl 2003). 2.3 Flow Batteries The flow batteries portray similar electrochemical reactions as the high-temperature and the conventional batteries. However, external tanks store the electrolyte material in the flow batteries thereby necessitating the pumping of the electrolyte in the battery while charging and discharging. The construction provides an allowance for power decoupling besides easing the process of replacing the electrolyte. The construction results in an increase in the maintenance and cost of flow batteries. The other ancillary equipment and the pumps also reduce the efficiency of the batteries. The redox and the hybrid are the two types of the flow batteries. The vanadium redox batteries have proven their compatibility with the wind and PV generators. They also guarantee power reliability and quality. Furthermore, they can play a pivotal role in spinning reserve and load leveling. They are also appropriate in forecast hedging and time shifting when connected to supply-driven energy systems. The existing units are approximately 5kW in size. On the other hand, the hybrid flow batteries consist of electro-active components in the form of a solid layer. They contain one fuel cell electrode and one battery electrode. Apparently, the size of the battery electrode determines the energy stored by the battery. 3. Chemical Energy Storage The technology relies on using electrical energy to create fuels that conventional power plants can burn to recreate the electrical energy. Synthetic methane and hydrogen suffice to be some of the fuels that power plants can burn to produce energy. They have a high energy density as compared to the other technologies. The figure below shows the sample energy density values. Figure 2: Sample Energy Density Values They are broadly referred to as “Power to Gas” technologies. The process begins with water electrolysis that splits water into hydrogen and oxygen. The next phase may either involve the direct storage of hydrogen to release energy when combusted at a future date. Alternatively, the process can involve combining hydrogen with carbon to form synthetic methane before storing and burning the gas to release energy. The flow chart below exhibits the energy transformation processes in a methane plant. Figure 3: The Methane Production Plant 4. High-Temperature Thermal Energy Storage The high-temperature energy storage stores heat energy from solar facilities or utility after the sunset. A good example of a power station is the 280MW Abengoa Solana solar power facility in Arizona that commenced operations in October 2013. The facility has a six hours thermal storage capability. The stations consist of a molten salt solution, insulated tanks and concentrating solar mirrors. The mirrors transfer the generated heat to the molten solution prior to storing the solution in insulated tanks to store the heat. At sunset, the system transfers the stored heat to conventional steam boilers to produce steam. Therefore, the system stores heat energy from the sun during the day to use it in the generation of electrical power at night. To enable the system to store electrical energy, it is imperative to integrate high-temperature electrical resistance heating capability to the system. 5. Combustion Turbine Inlet Cooling Storage It is evident that the combustion turbines compress air prior to feeding it into the combustion chamber. The compression phase influences the efficiency of the system. The fact that the density of cold air is higher than that of warm air necessitates the integration of a cooling system to the inlet air to enhance the maximum output and efficiency of the system. Evaporative techniques of cooling such as the use of chillers can serve to cool the inlet air. Thermal storage guarantees the continuous operation of the chillers at night when there are efficient chilling conditions because of the ambient air temperatures. Furthermore, the cost of power at night is less costly. The heat gets into the chillers at night. Energy recreation occurs when the turbines continue to operate at maximum efficiency at night. 6. Electromagnetic Storage Electromagnetic technologies target to store electrical energy in its original form rather than converting it into different forms for storage. The use of capacitors and superconducting electromagnets suffice to be the only available technologies that store electrical energy in its electrical form. Capacitors consist of the dialectic that separates the electrical conductors. The application of charge across the plates results in the storage of electric power in the electric field between the two plates. The SMES technology utilizes the flow of direct current through a superconducting coil cooled cryogenically so as to generate a magnetic field used to store the energy. Following the complete charging of the superconducting coil, the current does not deteriorate thus attaining an indefinite storage of the magnetic field. The table below summarizes the characteristics of the different energy storage technologies (Fuchs et al. 2012). Technology Maturity Cost ($/kW) Cost ($/kWh) Efficiency Cycle Limited Response Time Pumped Hydro Mature 1,500 - 2,700 138 - 338 80-82% No Seconds to Minutes Compressed Air (Underground) Demo to Mature 960 - 1,250 60 - 150 60-70% No Seconds to Minutes Compressed Air (Aboveground) Demo to Deploy 1,950 - 2,150 390 - 430 60-70% No Seconds to Minutes Flywheels Deploy to Mature 1,950 - 2,200 7,800 - 8,800 85-87% >100,000 Instantaneous Lead Acid Batteries Demo to Mature 950 - 5,800 350 - 3,800 75-90% 2,200 - >100,000 Milliseconds Lithium-ion Batteries Demo to Mature 1,085 - 4,100 900 - 6,200 87-94% 4,500 - >100,000 Milliseconds Flow Batteries (Vanadium Redox) Develop to Demo 3,000 - 3,700 620 - 830 65-75% >10,000 Milliseconds Flow Batteries (Zinc Bromide) Demo to Deploy 1,450 - 2,420 290 - 1,350 60-65% >10,000 Milliseconds Sodium Sulfur Demo to Deploy 3,100 - 4,000 445 - 555 75% 4,500 Milliseconds Power To Gas Demo 1,370 - 2,740 NA 30-45% No 10 Minutes Capacitors Develop to Demo - - 90-94%13 No Milliseconds SMES Develop to Demo - - 95%14 No Instantaneous Table 1: The Attributes of the energy storage technologies Project Concept Following the growing concerns over the increasing carbon footprint, several energy storage technologies have evolved to reduce overreliance on fossil fuels as the ultimate source of fuel. The project targets to explore the already established energy storage technologies that store renewable energy as opposed to non-renewable energy towards the ultimate goal of energy sustainability. Methods and Justification The project intends to utilize secondary data to obtain relevant information regarding the use of renewable energy storage technologies on a global scale. The project will use data concerning the mechanical, Project Plan The project team will require two weeks to collect and analyze information regarding the recommended energy storage technologies to store renewable energy thus guarantee its availability for future use. During the period, the members of the project will also compare the merits of the proposed energy storage technologies to assess their contribution to energy sustainability and the reduction of the atmospheric carbon footprint. Feasibility Some of the challenges associated with the technical feasibility of the project include the availability of sufficient information to cover the scope of the project. As mentioned above, the project targets to determine the extent of adoption of renewable energy storage technologies on a global scale. The project team believes that the internet will provide substantial resources to cover the objectives of the project. In relation to the economic feasibility, it is important to note that the project will recommend the best energy storage technologies to store renewable energy thus cater for the increasing demand for energy and eliminate the overreliance on fossil fuels as a source of energy. Regarding the legal feasibility aspect, it is proper to state that the scope of the project is in tandem with legal requirements since it aims to determine energy storage technologies that will guarantee the sustainability of energy besides reducing the current carbon footprint. Team Management Being the project leader, I will ascertain that all the members of the project take part in the collection of data. The members will then converge on the third day following the commencement of the project to compile and analyze the results of the data collection exercise. The next phase will involve comparing and contrasting the different energy saving technologies and their contribution towards reducing the carbon footprint. Upon the determination of the most appropriate techniques, the group will embark on developing a report on the findings, conclusion and recommendations. Conclusion and Recommendation The modern energy storage technologies have played a significant role towards ensuring the availability of energy to cater for the increasing demands. Moreover, the techniques have been instrumental in the reduction of the carbon footprint in the atmosphere through the adoption of green energy solutions such as wind, solar, and wave. However, it is evident that most of the sources of renewable energy are intermittent and unpredictable in nature. Therefore, the adoption of modern storage technologies to store heat and electrical energy from natural sources and avail the energy for utility at night or when there are moderate wind and tidal power is imperative to energy sustainability. The project identified mechanical energy storage technologies such as the Pumped Hydro Storage, Compressed Air Energy Storage, and flywheels. The project also identified electrochemical energy technologies such as conventional batteries, high temperature, and flow batteries. The other technologies found by the project include the chemical energy storage technologies and high-temperature thermal energy storage. The combustion turbine inlet cooling storage and electromagnetic storage are the other modern technologies for storing renewable energy. For the world to witness a reduction in the emission of CFCs in the atmosphere because of the overreliance on fossil fuels, it is imperative to harness and store renewable energy using modern energy storage technologies. Reference List Fuchs, G, Lunz, B, Leuthold, M, Sauer, D U 2012, ‘Technology Overview on Electricity Storage’, Smart Energy for Europe Platform GmbH (SEFEP). Kintner-Meyer, M, Jin, C, Balducci, P, Elizondo, M, Guo, X, Nguyen, T & Viswanathan, V 2011, ‘Energy storage for variable renewable energy resource integration—A regional assessment for the Northwest Power Pool (NWPP)’, In Power Systems Conference and Exposition (PSCE), 2011 IEEE/PES (pp. 1-7), IEEE. Schoenung, S &Hassenzahl, W V 2003, ‘Long- vs. Short-Term Energy Storage Technologies Analysis’, Sandia National Laboratories, Albuquerque. Vasconcelos, J, et al. 2012, ‘Electricity Storage: How to Facilitate its Deployment and Operation in the EU’, Think. Read More

However, there exist significant differences that distinguish the two systems of generating and storing renewable energy. For instance, an energy system that permits the timing of the consumption of the energy suffices to be a storage system. The systems allow the operator to vary the timing of the energy consumption. Some of the energy storage technologies encompass: 1. Mechanical 1.1 Pumped Hydro Storage The pumped storage suffices to be the most used energy storage technology. It boasts of a global capacity of 129GW with the US systems accounting for 22GW.

It is evident that the versatile nature of the technology allows the operators to vary the supply of energy to the different hours of the day. The operation of the technology entails the pumping of water from a lower reservoir to an upper one using electricity during instances of low power demand. When the demand is high, water flows from the upper reservoir through the turbines to recover the energy. The economic lifespan of the technology is in excess of 50 years. They also require less O & M and do not exhibit cyclic degradation.

However, the siting requirements of the technologies should be specific. The installation of the reservoirs and the production plant is also costly. The storage system installed in the US serves as a peak shaving and load leveling energy management tool. The system also portrays an efficiency of between 70 and 85%. 1.2 Compressed Air Energy Storage The CAES technologies consist of electric motors that run thus compressing air into enclosed volumes. To recreate the electrical energy, the system operators feed the compressed air into combustion air turbines.

Even though the combustion turbines utilize some fossil fuels in the operation, the amount of electrical energy produced trebles that of the conventional gas turbines. There exist two main types of the compressed air combustion turbines. The Germany's 321MW generator, 60MW compressor, 4-hour discharge and the Alabama's 110MW generator, 50MW compressor, 26-hour discharge (Vasconcelos et al. 2012). The US Energy Department, the Pacific Energy and Electric and EPRI are working on the development of a 300MW CAES plant with a storage capacity of 10 hours.

The CAES units exhibit energy efficiencies of between 40-75%. The start-up phase of the units requires five to 15 seconds with a ramp-up rate of 20% for every 60 seconds in the charging mode and 10% for every 3 seconds while discharging. Initially, the heat that results from the compression of air gets lost to the environment. However, the modern CAES systems intend to capture this heat so as to increase the energy yield of the system. Rather than losing the heat to the atmosphere, the engineers plan to design the system such that the heat heats up the air as it passes through the inlet of the combustion turbine.

The steady and slow compression of air is the other solution to preventing heat loss during compression. By so doing, the air maintains approximately equal temperatures during both compression and expansion procedures. Over-the-ground storage tanks and underground caverns both serve to store the compressed air. 1.3 Flywheels The operation of the flywheels in storing energy entails speeding up the rotors. The inertial masses rest on magnetic bearings that exhibit very little friction. The placement of the rotors in evacuated chambers also serves to reduce the friction.

The motor-generator rotates a shaft connected to the rotor thus allowing the transfer of energy in and out. Apparently, the inertial masses are the primary component of the flywheel. The major attributes of the rotors (maximum rotational frequency and frequency) determine the density and the energy capacity of the rotors. On the other hand, the power electronics and the motor generator determine the flywheel’s maximum power output. Consequently, it is possible to decouple energy capacities and power of the flywheel.

The power of the flywheels ranges between 100kW to 2MW with the discharge times varying from five seconds to 15 minutes. 1.

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