The Truth About Pumped Hydro

we've been exploring future technologies for energy storage on the grid a lot lately to me it's the most important technologies humans need to develop in our battle against climate change solar and wind technologies have reached maturity and are capable of providing more than enough energy for all of humankind for a fraction of the cost of older fossil fuel power and before i hear the same argument in the comments no they aren't cheaper because of subsidies in 2017 the fossil fuel industry received subsidies totaling 447 billion dollars worldwide dwarving the 128 billion renewables received despite renewables providing a larger share of new capacity installations in 2017 at around 75 of total new electricity generation capacity renewables are cheaper cleaner and sustainable that's why countries are investing in renewables that's the point of subsidies it's government funding for economy sustaining infrastructure and the faster we can transition the better countries will become less reliant on constant imports of fossil fuels from war-ravaged regions will create new jobs in renewable industry and not to mention because we are looking down the barrel of a climate crisis that is going to send the world into chaos if we don't address it now the primary factor holding renewables back today is this energy storage problem lithium ion batteries and other novel battery technologies are rapidly becoming the forerunners to form the brunt of our energy storage needs while hydrogen looks poised to seize long duration energy storage applications however in all of this analysis we have glossed over the oldest and most dominant form of energy storage a simple method of energy storage that converts electricity to potential energy by pumping water to an elevated reservoir where it can be later released to drive an impeller when the electricity is needed pumped hydro is one of the oldest technologies still in use in our modern day electricity grid it's a rugged long-lived and mature technology that has provided an incredibly valuable service to grids across the world for more than a century there have been calls around the world to increase our energy storage capacity in this tried and tested technology however as we will find out it's not quite as simple as investing in the infrastructure to learn more about this essential technology i visited turlock hill ireland's first and only pumped hydro station construction began on this landmark infrastructure project in 1968 and after six years of laborious excavation the final components of the generators were installed and became operational in 1974. since then turlock hill has provided valuable load shifting services for the irish electricity grid requiring just one overhaul of its facilities in 2012 38 years into its operation that is an impressive life cycle historically turlock hill has taken thermal power generation from coal oil and peat fuel stations which could not be turned off at night and released that power during the day when needed most however today it's become a valuable resource as ireland rapidly increases its wind power generation helping the country to gradually decommission those heavily polluting fossil fuel plants and replacing them with wind ireland with its windy position on the edge of the atlantic has prime real estate to begin growing its offshore and onshore wind resources and with the help of energy storage can become a net exporter of energy to its neighbors in the uk and wider europe however the question i find myself asking is how many turlock hills would ireland need to fully convert to renewables to understand the scale of the task at hand let's imagine one cubic meter of water we can raise its energy by increasing its height we can calculate the increase in energy using the equation for gravitational potential energy which is simply the mass of the object multiplied by the acceleration due to gravity multiplied by its height here we are defining height as the difference in height between our starting point and our end point the mass of one cubic meter of water is one thousand kilograms so with every one meter gain in height we add 9810 joules of energy we will convert to watt hours here as it's a more commonly used unit 9810 joules equals about 2.7 to 5 watt hours that's not a lot that could run a 100 watt light bulb for just 98.1 seconds but we can't convert that energy perfectly turlock hill is about 80 percent efficient so that would be closer to 78.5 seconds if we raised it to 286 meters the head of turlock hill that one cubic meter block of water could power that same light bulb for 22 451 seconds or about 6.2 hours we of course couldn't drip feed that water like this through a generator over nearly six hours let's see how the power station buried deep within the mountain works to get there we drove down this tunnel it felt like we were entering some villain's lair from james bond the tunnel is 600 meters long and the granite rock was blasted out of the mountain using explosives until the desired location of the internal cavern was met here they cleared a cavern 28 meters high 23 meters wide and 82 meters long to install the four 73 megawatt generators deep inside the mountain the cavern cross section looks like this we enter the cavern here on the upper level where the pony motors are located these are electric motors which take electricity from the grid to spin impellers located on the lower level which pumps water uphill when we need to generate electricity this valve also on the lower level opens to allow water to flow through the impeller this now rotates the impeller in the opposite direction and drives the generator located just under the pony motor this is a single machine that is capable of both pumping water and generating electricity there is no control over the rotational speed here it's a fixed speed generator locked to the grid's 50 hertz frequency however there are wicked gates between this valve and the impeller which limits the flow rate into the impeller and allows the generator to be throttled down to 5 megawatts this is an important feature that allows turlock hill to quickly ramp its production up or down with grid demands it also features a compressed air evacuation system that allows the impeller chamber to be quickly emptied of water using a blast of compressed air this allows the impeller to quickly reverse direction without the resistance of the water impeding it allowing turlock hill to quickly switch from generation to pumping at maximum flow rate water rushes through the machine at 28.3 cubic meters per second for a total of 111.3 cubic meters per second if all four 73 megawatt generators are used that is an ungodly rush of water 111 metric tons of water every second at this flow rate the 2.3 million cubic meter upper reservoir would be drained in a little over five and a half hours when this valve opens to the water pressing down on it with the force of 29 atmospheres you can feel the ground beneath you shake i was in the driveshaft access room during generation and the power behind it was truly awe-inspiring this massive chunk of steel rotates at 500 revolutions per minute driving the rotors to rotate inside the magnetic stators to generate 73 megawatts of power that's an enormous quantity of water and electricity it felt like the entire mountain was shaking around me together these four generators can provide up to 292 megawatts of power capable of providing about 4.8 of ireland's total electricity needs at its peak demand of about 6 000 megawatts which occurs at about 5 30 pm every day this is a truly massive battery that helps ireland immensely in smoothing out its erratic wind generation over the last month this is what wind generation in ireland looked like going to a maximum of 4 249 megawatts over 80 percent of ireland's maximum demand to a minimum of 300 megawatts just 5 of the maximum demand thankfully ireland's grid operator has become incredibly skilled in forecasting wind generation using weather data this graph shows the actual wind generation and this is the forecasted generation this ability to predict what power will be available ahead of time allows ireland's grid operators to predict when quick response generators like turlock hill and natural gas power plants will need to kick in and take up the slack going forward though we will want to completely eliminate this natural gas generation so let's look at the average natural gas generation in ireland and figure out how much pump storage would be needed to replace it this will be a little imprecise and won't account for many scenarios but we can get a general idea of the challenge that awaits us i started by downloading the generation data from the irish grid dashboard website and found the average generation for the past month which came out to 4840 megawatts over that period roughly 50 percent of power generation came from fossil fuels so let's say we need 2 420 megawatts of power generation that would require 8.3 pumped hydro stations like turlock hill to satisfy this demand at any one moment but the problem is turlock hill can only run for five and a half hours at peak generation this power generation would need to be available 24 hours a day so we are going to need four to five groups of eight pumped hydro stations available to come online at different periods of the day that would require about 37 stations of equivalent size now keep in mind that ireland is a relatively sparsely populated country new york city has a larger population than the entire island of ireland 37 facilities like this for such a small population is a massive undertaking if we were to create one massive reservoir with the same head as turlock hill that reservoir would need a volume of 85 million cubic meters that is roughly the same volume of ireland's ninth largest lake and trying to find space for that on top of large hills and mountains isn't easy finding suitable sites for pumped storage is difficult extremely difficult we need not one but two reservoirs capable of holding massive volumes of water separated by a meaningful height at least 200 meters but the horizontal distance between the two reservoirs needs to be relatively short as a long passage between the upper and lower reservoir will result in greater energy losses due to friction and viscous fluid effects the cost of boring the tunnels between the reservoirs will also be higher typically the cutoff point is defined by a ratio of head height to horizontal distance anything greater than 1 to 10 is usually deemed uneconomical so a 200 meter head could have a maximum horizontal distance of two kilometers between the reservoirs turlock hill has a head to height ratio of about 1.5 next the site needs to be relatively close to population centers to avoid transmission losses or expensive purpose-built high-voltage transmission lines to connect to a distant grid we also need a supply of fresh water which is a much larger logistical issue than people anticipate fresh water resources are valuable and interfering with them often comes with environmental concerns even with a closed-loop storage system like turlock hill where water is just swapped from one reservoir to the other without an outflow this water can evaporate over time thankfully it's rarely sunny and rains so often in ireland that any evaporation is more than replaced by groundwater gathered by the lower reservoirs catchment area because finding suitable sites for pumped hydro storage is difficult we've designed algorithms that scour over databases of map data looking for suitable sites and there are plenty of proposed sites currently vying for planning permission or already under construction but there isn't enough to satisfy our total energy storage needs ireland has just one active site seeking permission to begin construction the estimated cost of the facility will be 948 million dollars and will use a disused strip mine as its lower reservoir it now has eu backing but still hasn't begun construction a decade after first being proposed the combination of high initial capital cost and environmental concerns often block the few suitable sites we can't find this progress is too slow to this end some companies are looking to fix these problems a pumped storage facility that used salt water instead of fresh water would open some locations where fresh water is scarce a seawater pumped storage facility was tested to limited success in japan but that experimental facility eventually closed due to lack of demand for the electricity this could open many new possibilities and would be particularly valuable for places like california where fresh water is a valuable asset and solar energy is abundant one such facility was proposed in county mayo in ireland on this large flat-topped mountain directly next to the sea a flat-topped mountain of this size could house a massive upper reservoir and simply used the atlantic ocean as its lower reservoir others like quid net energy are looking to instead pump water into underground rock layers under pressure which would then be released to drive a generator when needed pump storage is a reliable and long lasting energy storage method it's not going anywhere it is coming under pressure from competition from cheaper batteries that don't require massive 1 billion dollar investments but its ability to store energy for longer durations will ensure its continued use one energy storage method isn't going to fix this problem we are going to see a world where multiple methods are used this graph taken from a fantastic paper on levelized cost of storage shows the mix ic being utilized by 2050 a combination of several forms of batteries for fast frequency response and short duration load shifting with pumped hydro being used for longer duration storage from 12 to 72 hours while hydrogen is the only feasible method for longer duration storage there won't be just one solution that solves this energy storage crisis this problem is going to need a holistic analysis of the grid and its needs electricity generation is just one aspect of how humans need to adapt to a more sustainable existence on this planet we have a long way to go in our quest to avoid climate disaster this video was created in partnership with bill gates inspired by his new book how to avoid a climate disaster which approaches this problem with the exact holistic analysis i mentioned above you can find out more about how we can all work together to avoid a climate disaster with the link below [Music] you

Channel: Real Engineering

Views: 564,713

Rating: 4.748817 out of 5

Keywords: engineering, science, technology, education, history, real

Id: JSgd-QhLHRI

Length: 16min 53sec (1013 seconds)

Published: Sat Feb 20 2021

Reddit Comments

[u/erikannen]

I visited the Raccoon Mountain Pumped-Storage Plant in Chattanooga, TN and fell in love with this concept. It uses water from the Tennessee River via Nickajack Lake and can make up to 1,652 megawatts for 22 hours.

In the United States, I'm curious how mountaintop removal sites in Appalachia could somehow be used for pumped hydro to (1) provide economic opportunity for the area while (2) creating some bigass batteries for the regional grid. I love win-wins like that, like this geothermal approach that can provide tons of green jobs to the fracking industry.

[u/arbivark]

wyoming has very strong winds for wind power generation, and steep mountains well suited for doing pumped hydro. there was a guy trying to line up a transmission line so wyoming could power LA. haven't heard an update for a while. it's not ideal for solar, but land is cheap so solar could be included as part of the mix.