Hydropower as the Future of Energy Storage:

Transcription

1 A FROST & SULLIVAN WHITE PAPER Hydropower as the Future of Energy Storage: The Revival of a Trusted Technology Sponsored by Toshiba

2 Contents Introduction 3 Why We Need Diversity in US Power Portfolio 3 Hydropower A Potential for Market Resurgence? 5 Using an Existing Resource 5 PSPP Leads the Market in Energy Storage 8 Hydropower Awakening of an Historic Technology 9 Key Advances 9 Benefits of an Adjustable Speed Pumped Storage System 9 Toshiba s Role in Hydro Across Time 10 Pumped Storage for the US Improvements at Work Today 10 Are there Risks and Challenges with Hydropower? 11 Impact on Water Ecosystems 11 Up-Front Costs 12 The Future is Bright 12 Bridging the Gap 12 2

3 Introduction Why We Need Diversity in US Power Portfolio Global demand for carbon free power has grown tremendously in the last two decades. Germany and Denmark are both on track to eschew most to all of their conventional power generation sources in favor of renewable energy by In the US, about half of the states have renewable portfolio standards that will mandate that 15 to 25% of installed power generation be from renewable energy sources by 2020 or California has even increased its original target of 33%, to 50% renewable power, by Wind and Solar Power Wind and solar power have enjoyed double-digit growth rates thanks in large part to these mandates and government incentives that help the technologies be more economically viable against established fossil fuel and nuclear power. Prices have also fallen, especially for solar photovoltaic (PV) power, which has seen a decrease in price of over 75% from 2008 to According to the EIA, solar and wind added 9.6 and 8.1 GW of power, respectively, in For the first time in history, this was more than what was added in the same year for natural gas power (8GW), though natural gas overall fuels the largest share of installed power in the US (34%). Wind and solar are expected to continue their growth vis-à-vis other technologies, and may reach 20% of installed power generation in the US by These technologies have many advantages: they operate fuel-free and produce no carbon emissions, and have wide appeal with the general public. Wind and solar, however, also come with some challenges that make them significantly less efficient than conventional power. Due to the intermittent nature of how they generate power only when there is adequate sunlight or wind one megawatt of installed wind or solar will only generate 15% to 20% of the power, over time, that one megawatt of fossil or nuclear power will generate. The time of day in which that power is generating is also hard to control, and may not align with peak times of power demand. This unpredictable, on-and-off voltage from solar and wind is also technically problematic to the power grid or a building to use. Mitigating the Challenges of Wind and Solar Power To mitigate these challenges, energy storage comes into play, and energy storage systems (ESS) have also seen rapid growth. If a renewable power source can channel the electricity it generates into charging a battery, for example, then that battery 3

4 can discharge an even and steady source of power to the grid or a building. It can also discharge that power when it is most needed: a solar system can charge a battery at mid-day, when solar radiation is at its highest, and the battery can discharge that power in the evening when demand peaks and solar generation is waning. Batteries receive much of the attention in discussing energy storage. They have a long history, both with industry and consumers. Battery technology research is well funded, and as a result batteries are getting increasingly more reliable, powerful, and smaller. They can also be relatively easy to scale up or down to meet the demands of the installation. Battery energy storage systems (BESS) are regularly included in rooftop PV installations, at wind farms, and also along the grid for overall grid power stabilization. Batteries have some technical concerns as well. They can be highly susceptible to stressors such as heat, cold and humidity. Anyone who has owned the same cell phone for more than two years may have observed that the frequent charging and discharging cycle of a battery necessary for renewable energy storage and general grid stabilization has a detrimental effect on its longevity. However, while we have few if any options for replacing batteries in most applications, whether cell phones or electric vehicles or pacemakers, there are other options for energy storage at the grid level. Hydropower accounts for nearly half (46%) of the country s renewable power 46% 4

5 Hydropower A Potential for Market Resurgence? Using an Existing Resource While batteries get most of the press, another energy storage option already exists, and is one that actually accounts for over 95% of grid power storage. It has also been a steady part of the US power landscape since the beginning of the country s electrification: hydropower. Hydropower accounts for about 6% of the nation s power, and nearly half (46%) of the country s renewable power. The US has over 100 GW of hydropower currently installed, and the Department of Energy estimates it could add another 50% by Humanity has long used water for power and energy. As with harnessing the wind to drive sails, water wheels have been used for grinding flour for thousands of years. By the 1700s, the concept of using a water wheel for energy was being developed in France. Hydropower in the US started to take hold in the 1880s, when the first water-driven electricity system was used to power a storefront and movie theater in Grand Rapids, Michigan. Within about a decade, true hydropower plants began to be built across the US. Hydropower plants use gravitational potential energy falling water to spin a hydro turbine, which runs a generator to create electricity. Hydro turbines come in three main configurations: The Pelton turbines is the most basic and least efficient turbine design. The design resembles a water wheel that turns as water spills over it. A Kaplan turbine improves on the design by having blades that are angled at an axial direction to the flow of the incoming water, in an arrangement similar to the propeller of an early propeller-driven airplane. The Francis turbine combines both designs in a turbine that is more efficient than either, both in terms of maximum efficiency as well as over a wider range of speeds. Hence, running a Francis turbine below or above its ideal speed will still result in more power generated than the other two models. This is an important factor for pumped storage power plants (PSPP) because they need to be able to up- or downshift their power output at a moment s notice to manage loads on the grid. 5

6 BASIC HYDROPOWER WATER TURBINE DESIGN AND WATER FLOW Pelton Francis Kaplan A pumped storage power plant is a one configuration of hydropower that uses gravity and water to drive a turbine, however the water is in a close-looped, dual reservoir system, rather than falling from a dam. Pumps use electricity during low-power demand times, such as at night, to move water from a lower reservoir to a higher reservoir. During high demand times, the water is released and turns the turbine to generate electricity. PSPP is an ideal energy storage system that can store water as gravitational energy. PUMPED STORAGE SYSTEM Source: Toshiba. 6

7 Hydropower overall, and PSPP in particular, has sparked the interest of industry and the government in recent years to mitigate the challenges of grid fluctuations in a way that is economically viable and environmentally responsible. The DOE expects of the 50GW to be added to the US in the next 25 years, about 36GW will be in new pumped storage. PSPP are a highly efficient and flexible technology. A hydraulic turbine and generator can reach 90% efficiency, whereas other renewable technology such as wind and solar PV typically have maximum efficiencies of about 40% and 24%, respectively. This means that per installed megawatt, a PSPP will generate at least twice as much power than an installed megawatt of solar or wind. While hydropower plants can be expensive to build, they are easy to maintain due to the simple-structured design. And when considering their long life spans hydropower plants can be in operation for upwards of 30 to 40 years without needing major repairs or overhauls. When compared to the 20 to 25 year lifespan of many wind and solar plants, the long term value, of the plants becomes apparent. Also, older hydropower plants can be retrofitted to improve efficiency and increase power output as technologies improve and demand increases, unlike wind and solar. While the technology has merits on its own, PSPP is truly beneficial when working in collaboration with wind and solar, both in terms of energy storage along the grid as well as integrating wind or solar in the PSPP plant itself. Over 95% of the energy storage used for grid stabilization is from hydropower 95% 7

8 PSPP Leads the Market in Energy Storage As noted earlier, while battery energy storage is a key technology for renewables, over 95% of the energy storage used for grid stabilization is from hydropower. PSPP has numerous advantages that make it attractive for energy storage. PSPP Ideal for Load Balancing Energy storage along the grid is necessary to help supply fit demand. This balance is needed at a seasonal level, such as delivering more electricity to warm climates during the summer months to account for air conditioning. It s also needed throughout the course of a day arguably a more difficult and critical task. PSPP is a straightforward way to shift peak loads from low usage at night to the various peaks experienced during the day. Daytime power shifts can happen in minutes, and PSPP s versatility includes rapid response times in sudden load changes: the technology can start up in as quickly as three minutes, and adjust loads within one minute. Hence, if a sudden summer storm blocks solar PV power during a point of high power demand, PSPP can be deployed to balance the load for a safer and more consistent flow of power across the grid. PSPP is Even Better With Other Renewable Power Typical PSPP will use pumps to direct water to an elevated accumulation reservoir. The water is released and, leveraging gravity, spins a turbine generator to power. Power from the grid is usually used to pump the water, at night when prices and demand are at their lowest. Hence, PSPP do, indirectly, contribute to carbon emissions as it uses electricity from the grid that is most likely generated from fossil fuels. However, these emissions can be mitigated by using renewable energy on-site to drive the water into the holding reservoir. Solar or wind generated power could charge a battery energy storage system (BESS). The BESS would pump the water back into the reservoir at night. This is one of the most technically advantageous ways of using solar and wind power because, as noted earlier, their intermittent generation cannot be used to directly power equipment such as the massive pumps used in PSPP. The result of such a configuration fulfills the promises of renewable power: no fuel and no carbon emissions, but at a lower cost, with much higher efficiency, and without intermittent power fluctuations affecting the grid. 8

9 Another environmental benefit of PSPP is that because the technology needs reservoirs of varying heights, but not a river/dam configuration of a conventional plant, it can be sited anywhere that can geographically support two such reservoirs. Damming a river carries environmental concerns of changing the natural flow of water along with its impact on wildlife. The US can expand its conventional hydropower sources and limit further river impacts by using existing dams of which, in the US, about 75% are only dams and do not have on-site hydropower. There are many cases which PSPP can be installed in existing dams, thereby reducing some of the environmental concerns around hydropower. Hydropower Awakening of an Historic Technology Key Advances Although the basic concept of hydropower has changed little, the technology continues to make strides in power and efficiency. Some key advances in the technology include: Splitter Runners Configuration: Design and development of pump turbines with a splitter runners configuration. This configuration with more blades of alternating lengths has the advantage better management of turbulent waters. Adjustable Speed Pumped Storage System: One of the greatest advances in hydropower was the development of the adjustable-speed PSPP, a technology that was originally developed by Toshiba for a plant in Japan in Then it was reimagined, reengineered and put into a commercial use in the 1990s. Benefits of an Adjustable Speed Pumped Storage System PSPP typically use generators that run at constant synchronous speeds. This means the associated turbine is essentially locked in at generating energy at the same output, which, as an energy storage solution, makes it less versatile in responding to fluctuations on the power grid. Toshiba devised a way to create the world s first adjustable speed pumped storage generation system at the Yagisawa Hydroelectric Power Station for Tokyo Electric Power Company Holdings, Inc. in

10 Toshiba also built the world s largest capacity PSPP, the Kazunogawa Hydroelectric Power Station. The plant has the world s highest hydraulic head, 785 meters, and when completed will have a massive output of 1,600 MW. The plant is not only a feat of engineering due to its significant power output, but also because it demonstrates the benefits of adjustable speed pumped storage. It has smooth and even operation, even at partial loads, and an ability to do so at a wide range of speeds. The plant also showed improved efficiency at both full and partial loads over what was currently in the market. And, as is critical for peak power shifting, the plant demonstrated instantaneous adjustment of power input/output, so as to react immediately to mitigate power grid fluctuations Toshiba s Role in Hydro Across Time Toshiba, a global hydropower market leader, delivered its first Japanese-made hydroelectric station in Since then Toshiba has delivered over 1,800 hydropower generators totaling over 74 GVA of power, and over 2,300 hydro turbines totaling nearly 60GW of capacity. Thanks to its diversified portfolio, Toshiba provides a complete solution including total system engineering, equipment designing, manufacturing, procurement, assembling, testing and maintenance. Along with new installations, Toshiba has focused on improving the large base of existing hydropower plants. A great example of this is the Ludington plant in Michigan. Pumped Storage for the US Improvements at Work Today Ludington is a PSPP on the eastern shores of Lake Michigan, less than 100 miles from Grand Rapids where world first real-world use of hydropower electricity was demonstrated. Built in 1973, the plant began a major overhaul in 2011 that is expected to be complete by The project is carried out with concerted efforts of a multi national team consisting of Toshiba Corporation in Japan, which carries out design, Toshiba Hydro Power (Hangzhou) Co., Ltd. in China, which manufactures major components, and Toshiba America Energy Systems in USA, which carries out site work. In order to minimize the outage period accompanied by the overhaul, each stator is assembled in the building outside the generating pit, prior to commencement of each unit outage. 10

11 Toshiba began planning the overhaul by using a state-of-the-art technology to optimize pump-turbine performance. As a result, the overhaul will provide a 15% capacity addition, expanding the plant s output from 312 MW to 360 MW at the same head. Toshiba is manufacturing and shipping the world s largest hydro turbine for the plant. It also provides new motor-generator that will uprate the system from 325 MVA/388 MVA to 455 MVA. The rated voltage of the generator motor is the highest value in Toshiba s experiences of hydro generator and hydro generator motor. Along with the replacement of pump-turbine runner and motor-generator stator, other improvements included: New thrust bearing design Stay vane modifications Rotor pole refurbishment New static excitation systems, switchgear, and isolated phase bus Refurbishment of pony-motors The Ludington plant is a clear example of how PSPP can be accomplished, and improved upon, at a large scale for better grid stability and a reduced carbon footprint. Are there Risks and Challenges with Hydropower? Impact on Water Ecosystems Hydropower does have some challenges to contend with. As noted before, one concern with hydropower overall is its environmental impact on water ecosystems. PSPP can circumvent much of this impact with their closed-loop system, and in many cases do not require a new dam on a river, when an existing dam can be utilized. Thanks to hydropower s long life span both with PSPP and conventional plants power output increases are efficient and cost effective ways to significantly increase energy generation at existing sites, without the environmental intrusion of a new plant. 11

12 Up-Front Costs Another challenge for hydropower is its up-front costs. Capital costs for building hydropower are significant. However, several notable long-term factors weigh heavily in hydropower s favor such as: Longevity: The plants can go 30 to 40 years without major repairs or overhauls. Low to no fuel costs and risks: While fossil fuels in the US are primary fueled by domestic supplies of coal and gas, these supplies are finite and subject to price fluctuations. Hydropower is by design fueled by water and gravity, and hence have minimal exposure to fluctuation fossil fuel prices. Near-zero emissions: Which help guard against future environmental legislation, such as what has helped drive the decommissioning of coal plants. And near-zero emissions since hydropower basically generates power by water and gravity. Efficient: Efficiency of near 90%, with near-constant level of operation. Low maintenence: Ease of maintenance over the long term. The Future is Bright Bridging the Gap Hydropower has had a strong presence in US power, since the early days of power plants. It has provided near-carbon emission free power as well. The DOE estimates that 85% of all renewable energy generated in the US between 1950 and 2015 was from hydropower it is only in the last decade that this proportion has fallen to less than half due to the rapid growth of solar and wind. However hydropower remains an important part of the energy mix, and the dominant form of energy storage. New influences in generation and power management are adding complexity to the traditional system, and energy storage is expected to be one of the fastest growing markets for the US energy industry. By adding PSPP, the US can quickly and cleanly ramp up its energy storage needs with assets that are built to last a century or more. The need for clean, sustainable power has never been greater, and PSPP can bridge the gap of power that is environmentally, technologically, and fiscally responsible. 12

13 WHAT NEXT? Learn more about Toshiba s innovative energy solutions: toshiba.com/power This is the third in a series of Frost & Sullivan white papers on the future of energy in the US, the series will dive deeper into the following subjects: Energy Storage Energy in America Hydrogen Energy 13

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