People have used moving water to create energy for thousands of years. Today, pumped hydro is the most common form of grid-connected energy storage in the world.
This technology is in the spotlight because it pairs so well with solar and wind renewable energy. During the day, when solar panels and wind farms may be generating their highest level of energy, people don’t need really need much electricity. Unless it is stored somewhere the energy is lost.
Pumped hydro can cheaply and easily store the excess energy, releasing it again at night when demand rises.
Here’s how it all works:
How it works
Put as simply as possible, it involves pumping water to a reservoir at the top of a hill when energy is in plentiful supply, then letting it flow back down through a turbine to generate electricity when demand increases.
Like all storage systems, you get less energy out than you put in – in this case, generally around 80% of the original input – because you lose energy to friction in the pipes and turbine as well as in the generator. For comparison, lithium ion batteries are around 90-95% efficient, while hydrogen energy storage is less than 50% efficient
The benefit is we can store a lot of energy at the top of the hill and keep it there in a reservoir until we need the energy back again. Then it can be released through the pipes (this is called “penstock”) to generate electricity. This means pumped hydro can create a lot of additional electricity when demand is high (for example, during a heatwave).
The disadvantage of pumped hydro is you need to have two reservoirs separated by a significant elevation difference (more than 200m is typically required, more than 300m is ideal). So it doesn’t work where you don’t have hills. However, research has identified 22,000 potential sites in Australia.
Pumped hydro is traditionally paired with relatively inflexible coal or nuclear power stations, using under-utilised electricity when demand is low (weekends and nighttime), then providing additional generation when demand increases during the day and into the evening.
With the rapid increase in deployment of wind and solar, pumped hydro is again gaining interest. This is because the output of wind and solar plant is subject to the variability in the weather. For example, solar power plants generate the most electricity in the middle of the day, while demand for electricity is often highest in the evening. The wind might die down for hours or even days, then suddenly blow a gale. Pumped hydro can play a key role in smoothing out this variability.
If the electricity being produced by wind and solar plant is greater than demand, then the energy has to be curtailed (and is lost), unless we have a way to store it. Using this excess power to pump water up hill means the solar or wind energy is not wasted and the water can be held in reservoirs until demand rises in the evening.
There are lots of different kinds of energy storage technologies, each with their own advantages and disadvantages. For large-scale grid-connected systems where many hours of storage are required, pumped hydro is the most economically viable option.
About The Author
Roger Dargaville, Senior lecturer, Monash University
Product Description: With the power crisis engulfing the world, renewable sources of power like hydropower have gained prominence. Thus hydropower resources are being utilized all over the world on a large scale. This book is an effort to give the rudiments of hydropower generation, as a first course meant for undergraduate students. However, pumped storage plants, which generate peak power, are dealt with in more detail. A large number of illustrations and photographs have been included, making it easy to grasp the subject.
Product Description: This publication provides introductory technical guidance for civil engineers, mechanical engineers and electrical engineers and other professional engineers, construction managers and electric power system operators interested in pump storage hydroelectric power plants and their integration into regional electric power systems. Here is what is discussed: 1. INTRODUCTION, 2. GENERAL CHARACTERISTICS OF OFF-STREAM PUMPED-STORAGE PROJECTS, 3. OVERALL STUDY PROCEDURE, 4. SEQUENTIAL ROUTING STUDIES, 5. ECONOMIC ANALYSIS, 6. ANALYSIS OF PUMP-BACK PROJECTS, 7. SOCIAL PROBLEMS.
Product Description: This unique book and DVD-ROM set - revised for 2011 - combines our ring-bound book with our comprehensive 25,000 page CD-ROM about hydropower, hydroelectric power, and related technologies such as dams, turbines, and microhydropower. The electronic book on DVD-ROM provides an unprecedented encyclopedic collection of authoritative official documents and technical reports about every conceivable aspect of hydropower - with over 25,000 pages of invaluable material presented in Adobe Acrobat PDF format. This incredible library has been revised and updated for this 2011 edition. Progressive Management has been a leader in renewable energy publishing for nearly a decade, and we believe that this exceptional collection provides the most comprehensive set of government hydropower documents ever offered! If you have a professional or personal interest in hydropower energy, you will find this disc to be an effective, time-saving, and practical source of ready-to-use information. The collection includes information about hydroelectric power and related technologies such as dams, turbines, and microhydropower. There is new material about current federal government funding opportunities and incentives, advanced hydropower technology research, turbine field testing, engineering and analysis, response of turbine-passed fish, biomarkers, and salmon research plans. Research and development activities of the Department of Energy are covered, with information on technology development, projects, history, safety, and environmental impact. There is also material from the Federal Energy Regulatory Commission (FERC) regarding licensing, compliance, safety and inspections of hydropower and the hydropower industry. Coverage includes water energy resources, state assessment reports, and more. The hydrologic cycle provides the basis for hydropower -water constantly moves through a vast global cycle, in which it evaporates from lakes and oceans, forms clouds, precipitates as rain or snow, then flows back to the ocean. The energy of this water cycle, which is driven by the sun, is tapped most efficiently with hydropower. Diversion projects channel a portion of the river through a canal or a penstock and may require a dam. Impoundment hydropower uses a dam to store water. Water may be released either to meet changing electricity needs or to maintain a constant reservoir level. Pumped storage pumps water from a lower reservoir to an upper reservoir at times when demand for electricity is low. During periods of high electrical demand, the water is released back to the lower reservoir to generate electricity. Run-of-river projects utilize the flow of water within the natural range of the river, requiring little or no impoundment. Run-of-river plants can be designed using large flow rates with low head or small flow rates with high head. Microhydropower projects-produce 100 kilowatts (kW) or less. Microhydro plants can utilize low heads or high heads. Current hydropower technology, while essentially emission-free, can have undesirable environmental effects, such as fish injury and mortality from passage through turbines, as well as detrimental changes in the quality (dissolved gases) of downstream water. Advanced hydropower turbine technology could minimize the adverse effects yet preserve the ability to generate electricity from an important renewable resource. The goal of the U.S. Department of Energy's (DOE's) Advanced Hydropower Turbine System Program is to develop technology that will allow the nation to maximize the use of its hydropower resources while minimizing adverse environmental effects. Conceptual designs of environmentally friendly hydropower turbines have been completed under the DOE-industry program.