Projects:2019s1-192 Gravitational Energy Storage
The cost of extending conventional power grids makes it difficult to supply remote locations. There are established solutions, such as diesel-generators, but these are expensive, and are more suited to corporations, or large communities. There are low-cost solutions for small remote communities, in the third-world. These typically involve the use of batteries, but there are problems with batteries: they have finite lifetimes; they use chemicals that are scarce and toxic; they are difficult to repair (using simple tools); they suffer from internal leakage. There are solutions that have been used in remote communities (in Africa) where the storage is gravitational. Gravitational storage is much more convivial. Gravitational storage is very robust, with a long lifetime; it does not use exotic materials, it can be easily repaired using simple tools; there is no internal leakage. The main disadvantage of gravitational storage is low energy-density. It would take a very large mass, falling through a very large distance, to match a car-battery, for example. The loads have to be chosen appropriately, low-power LED lighting, for example. Also energy conversion has to be very efficient. In this project we will examine the possibility of using permanent-magnet synchronous machines, and power-electronics to efficiently store energy in gravitational form, and then to efficiently recover that energy at a later time. The plan is to design, build and test a small-scale solution, as a proof of concept.
Contents
Project Team
Students
- Keilah David
- Kai Yang
Supervisor
- Andrew Allison
Introduction
Gravitational energy storage is that changing the height of the solid matter can be stored or released by a lifting system driven by an electric motor/generator. Compared with fossil fuels, this type of energy is more environmentally friendly. Gravitational storage is very rugged and has a long service life. It does not use special materials and can be easily repaired with simple tools. There is no internal leakage. There will be no other pollutants discharged at the same time. However, this system is not perfect. It needs heavy enough weight and enough height to get enough gravity potential to generate electricity for the motor. This means that the gravity energy storage system needs enough space to run.
Aim
The aim of the project is to develop (design, build and test) a small scale gravitational energy storage solution and effectively and efficiently store and recover energy by using permanent-magnet synchronous machines, power electronics and appropriate loads.
motivation
The motivation of the project is to supply energy to remote communities and third-world countries cost-effectively and provide a much cleaner, cheaper and more robust form of energy supply.
Background
The input power of the motor comes from the gravitational potential energy generated by the weight drop. According to the formula, E= mgh. The gravitational potential is proportional to the mass of the weight and the height. Therefore, heavy enough weight and enough height can get enough gravity potential energy. The pumped hydro is an application of gravitational energy storage.
Case Study
Three Gorges Dam
The Three Gorges Dam is the world's largest hydraulic gravity dam, located in Sandouping Town, Yiling District, Yichang City, Hubei Province, China. The installed capacity is 22,500 megawatts and consists of 32 turbine generators with a power of 700 watts and two small large motors of 50 watts. The dam produced 98.8 TWh and 103.1 TWh in 2014 and 2016, respectively. The Three Gorges Project completed all construction tasks in three stages, with a total construction period of 17 years. The first stage (1993-1997) is for construction preparation. The construction takes 5 years to mark the river closure. The second stage (1998-2003) is the second phase of the project. The construction takes 6 years to mark the initial storage of the reservoir, the first batch of generating units and the permanent ship lock. The third stage (2004-2009) is the third phase of the project. The construction takes 6 years to mark the completion of the complete power generation and hub project. When it comes to the economics, in the early stage of fundraising, the State Council decided to levy a fund of 3 cents per kWh of the Three Gorges Project in 1992. Since 1994, the Three Gorges Fund has adjusted to 4 cents per kWh. On March 18, 1994, the property rights of Gezhouba Power Plant were placed under the China Three Gorges Corporation, and part of its power generation profits could be used for the construction of the Three Gorges Project. The source of funds for the construction of the Three Gorges Project is also solved by using the power generation income, loans, and issuance of bonds of the Three Gorges Power Station. After the completion of the first project, the Three Gorges Corporation issued bonds, 98 Three Gorges bonds (2 billion yuan), 99 Three Gorges bonds (3 billion yuan), and 01 Three Gorges bonds (5 billion yuan) were issued one after another at the Shanghai Stock Exchange and Shenzhen. The stock exchange is listed. By the end of 2001, the Three Gorges Corporation had issued 11 billion yuan of corporate bonds to the society. By the end of 2001, a total of 76.230 billion yuan was invested in the construction of the Three Gorges Project. At the same time, the China Development Bank loaned 2.8 billion yuan, the Swiss export credit agency Bundesrat Exportrisikogarantie loaned $143.1 million to the Three Gorges Dam project, and the Canadian Export Development Cooperation (EDC) funded $38 million. The above funds will be used for the second and third stage. In terms of raw material suppliers, AGRA Monenco signed a $25 million contract in 1994 for project management systems to provide system layout and engineering, testing, operational guidance and training. Dominion Bridge, Inc. A contract worth $64 million was signed with Chongqing and Sichuan Province to supply cement for the dam. HUAXIN Cement also supplies cement to the dam. General Electric of Canada and Siemens and the German engineering company Voith Hydro signed a $320 million contract in 1997 to provide six turbines for the dam. French electrical equipment and engineering company GEC-Alsthom supplied eight turbine generators to the Three Gorges Dam in 1997 with Asea Brown Boveri (ABB) and Kvaerner Energy. Siemens and GE Canada and Voith-Hydro jointly supplied six generators to the dam. In terms of profitability, China Southern Power Grid needs to pay 250 RMB per kWh, and China National Grid needs to pay 250 RMB per kWh. Each province that receives electricity from the Three Gorges Dam will have to pay an additional fee of RMB 7 per MWh. Other provinces must pay an additional fee of RMB 4 per MWh. The Tibet Autonomous Region does not charge any surcharges. It is expected that the dam will be returned after 10 years of full use, but the full cost of the Three Gorges Dam was recovered on December 30, 2013, with a payback period of four years. The construction of the Three Gorges Dam also brought about the relocation of local people and the destruction of the surrounding environment. While building the dam, the Three Gorges Corporation also needs to pay the local residents' moving expenses and restore the local ecological environment.
