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Lecture – 4 Transmission, Distribution and Storage of Energy Widodo W. Purwanto Departemen Teknik Kimia Sistem Transmisi and Distribusi Petroleum Industry Natural Gas Industry © PEUI -2006 LNG value chain © PEUI -2006 Coal to Products Electricity RE Energy Storage Type of energy storage Chemical Electrochemical Capacitor Supercapacitor Superconducting magnetic energy storage (SMES) Mechanical Batteries Flow batteries Fuel cells Electrical Hydrogen Biofuels Compressed air energy storage (CAES) Flywheel energy storage Hydraulic accumulator Hydroelectric energy storage Spring Thermal Molten salt [1] Cryogenic liquid air or nitrogen Seasonal thermal store Solar pond Hot bricks Steam accumulator Fireless locomotive Energy Storage Status Electricity storage Grid Energy Storage Grid energy storage is used for management of the flow of electrical energy. For large-scale load levelling on an interconnected electrical system, electric energy producers send low value off-peak excess electricity over the electricity transmission grid to temporary energy storage sites that become energy producers when electricity demand is greater. This reduces the cost of peak demand electricity by making off-peak energy available for use during peak demand without having to provide excess generation that would not be used most of the day. In addition, grid-connected intermittent energy sources such as photovoltaic and wind turbine users can use the electric power network to absorb surplus produced and meet needs during periods when the intermittent source is not available through the use of net metering. Effectively the intermittent source displaces energy that would have been produced by other sources. The grid connected system does not store energy on behalf of the intermittent source, instead it relies on the load following capability of other generating units. At high penetration levels, however, grid energy storage is needed to absorb the peak solar and wind outputs, when they exceed load demand. Solar and wind are nondispatchable; they need to be accepted Form of storage 1.1 Pumped water 1.2 Batteries 1.3 Compressed air 1.4 Thermal 1.5 Flywheel 1.6 Superconducting magnetic energy 1.7 Hydrogen Load Levelling The demand for electricity from consumers and industry is constantly changing, broadly within the following categories: Seasonal (during dark winters more electric lighting and heating is required, while in other climates hot weather boosts the requirement for air conditioning) Weekly (most industry closes at the weekend, lowering demand) Daily (such as the peak as everyone arrives home and switches the television on) Hourly (one method for estimating television viewing figures in the United Kingdom is to measure the power spikes during advertisement breaks or after programmes when viewers go to switch the kettle on [19]) Transient (fluctuations due to individual's actions, differences in power transmission efficiency and other small factors that need to be accounted for) There are currently three main methods for dealing with changing demand: Electrical devices generally having a working voltage range that they require, commonly 110-120V or 220-240V. Minor variations in load are automatically smoothed by slight variations in the voltage available across the system. Power plants can be run below their normal output, with the facility to increase the amount they generate almost instantaneously. This is termed 'Spinning Reserve'. Additional power plants can be brought online to provide a larger generating capacity. Typically, these would be combustion gas turbines, which can be started in a matter of minutes. The problem with relying on these last two methods in particular is that they are expensive, because they leave expensive generating equipment unused much of the time, and because plants running below maximum output usually produce at less than their best efficiency. Grid energy storage is used to shift load from peak to off-peak hours. Power plants are able to run closer to their peak efficiency for much of the year. Electric storage options Cost of 20 Capacity Storage hrs. storage Technology ($/kW) ($/kWh) ($/kW) 1 Compressed Air Energy 350 370 Storage (CAES) (350 MW) 10 Pumped hydroelectric 900 1100 100 Advanced battery (10 MW) 120 2100 300 Flywheel (100 MW) 150 6200 300 Superconductor (100 MW) 120 6100 Source: Schainker, 1997 (reproduced in PCAST, 1999) CAES is clear choice for: • Several hours (or more) of storage • Large capacity (> ~100 MW) Compressed air energy storage (CAES) CAES model Spilled power (if storage full) PC CO2 Compressor Air Losses Spilled power CAES capacity Transmission line capacity PWF Generator Losses X hS PG Air storage Direct output (≤ PT) Fuel Transmission losses Total system output (≤ PT) Battery Energy Storage Systems Comparison of Different Battery Energy Storage Systems Electrochemical Flow Cell Systems Comparison of Redox Flow Cell Energy Storage Systems Kinetic Energy Storage Systems (Flywheel Storage) Hydrogen Based Energy Storage System Hydrogen Storage Natural gas storage US LNG Storage US Underground Storage Peak Shaving LNG LNG terminal CNG storage cylinders – volume versus weight comparison Cylinder Types Cylinders – All Metal Fully Wrapped Composite with Metal Liners Hoop Wrapped Composite Fully Wrapped Composite with Non-Metallic Liners A Comparison of the CNG Cylinders Types Storage methods for natural gas and comparison with ANG ANG fuel container Energy density Storage capacity