Placeholder Image

字幕列表 影片播放

  • We have been exploring future technologies for energy storage on the grid a lot lately.

  • To me, it's the most important technology 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 old argument in the comments, no they aren't

  • cheaper because of subsidies. In 2017 the fossil fuel industry received

  • subsidies totalling 447 billion dollars worldwide, dwarving the 128 billion renewables received.[1]

  • Despite renewables providing a larger share of new capacity installations in 2017 at around

  • 75% of total new electricity generation capacity. [2] 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. 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 the renewable industry, and 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 later be released to drive an impeller turbine 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 provides 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 Turlough Hill, Ireland's first

  • and only pumped hydro station. Construction began on this landmark infrastructure project

  • in 1968 and after 6 years of laborious excavation the final components of the generators were

  • installed and became operational in 1974. Since then Turlough 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, Turlough Hill has taken thermal power generation from coal, oil and peat fueled

  • stations, which could not be turned off at night, and released that power during the

  • day when needed most.

  • However, today it has become a valuable resource as Ireland rapidly increases it's wind power

  • generation. Helping the country to gradually decommission those heavily polluting fossil

  • fuel plants and replacing them with wind. Ireland, with it's windy position on the

  • edge of the Atlantic, has prime real estate to begin growing it's offshore and onshore

  • wind resources and with the help of energy storage, become a net exporter of energy.

  • To its neighbours in the UK and wider Europe.

  • However, the question I find myself asking, is how many Turlough Hills would Ireland need

  • to fully convert to renewables?

  • To understand the scale of the task at hand, let's imagine a 1 cubic metre cube 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 end point.

  • The mass of a 1 cubic metre of water is 1000 kilograms, so with every 1 metre 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 2.725 Watt Hours. That's not a lot.

  • That could run a 100 watt lightbulb for just 98.1 seconds, but we can't convert that

  • energy perfectly. Turlough Hill is about 80% efficient, so that would be closer to 78.5

  • seconds. If we raised it to 286 metres, the head of Turlough Hill, that 1 cubic metre

  • 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 water like this through a generator over nearly 6 hours.

  • Let's see how the power station buried deep within this 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 metres 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 metres high. 23 metres wide and 82 metres long to install

  • the four 73 megawatt generators deep inside the mountain. [3]

  • Animation 2a 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

  • impellers 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 50 Hertz Frequency. However, there are wicket 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 Turlough Hill to quickly

  • ramp it's 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 Turlough Hill to quickly switch from generation

  • to pumping.

  • At maximum flow rate, water rushes through the machine at 28.3 cubic metres per second.

  • For a total of 111.3 cubic metres per second if all four 73 megawatt generators are used.

  • That is an ungodly rush of water. One hundred and eleven metric tonnes of water, every second.

  • At this flow rate the 2.3 million cubic metre upper reservoir would be drained in a little

  • over 5 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 drive shaft 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 292 MW of power.

  • Capable of providing about 4.8% of Ireland's total electricity needs at its peak demand

  • of about 6000 MW, which occurs at about 5.30 pm every day.[4]

  • This is truly a massive battery that helps Ireland immensely in smoothing out it's

  • erratic wind generation. Over the last month, this is what wind generation in Ireland looked

  • like. [5] Going to a maximum of 4249 megawatts over 80% of Ireland's maximum demand, to

  • a minimum of 300 megawatts, just 5% of 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 Turlough 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 pumped

  • 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.[6]

  • Over that period roughly 50% of power generation came from fossil fuels. So, let's say we

  • need 2420 megawatts of power generation.

  • That would require 8.3 more pumped hydro stations like Turlough hill to satisfy at any one moment,

  • but the problem is, Turlough Hill can only run for 5.3 hours at peak generation.

  • This power generation would need to be available 24 hours a day, so we are going to need 4

  • to 5 groups of 8 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 Turlough Hill, that reservoir would need a volume of 85 million

  • cubic metres. That is roughly the same volume of Ireland's 9th 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 metres, 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 cut off point is defined by a ratio of head height to horizontal distance.

  • Anything greater 1:10 is usually deemed uneconomical. [7] So a 200 metre head could have a maximum

  • horizontal distance of 2 kilometres between the reservoirs.

  • Turlough Hill has a head to height ratio of about 1:5.

  • Next, the site needs to be relatively close to population centres 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. Freshwater resources are valuable and interfering with them often comes with

  • environmental concerns. Even with a closed loop storage system, like Turlough 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 ground water gathered by the lower reservoirs catchment

  • area.

  • Because finding suitable sites for pumped hydro storage is difficult, we have designed

  • algorithms [8] 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 it's

  • lower reservoir. [9] 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 environment

  • concerns often block the few suitable sites we can 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 freshwater

  • is scarce.

  • A seawater pumped storage facility was tested to limited success in Japan [10], 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 very 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 use the Atlantic ocean as it's lower reservoir.

  • Others, like Quidnet Energy, are looking to instead pump water into underground rock layers

  • under pressure, which would then be released to drive a generator when needed.

  • Pumped 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 it's 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 I

  • see be utilized by 2050. [11]

  • A combination for 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 being the only feasible option 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 it's 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 a climate disaster.

  • This video was created in partnership with Bill Gates, inspired by his new bookHow

  • 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.

We have been exploring future technologies for energy storage on the grid a lot lately.

字幕與單字

影片操作 你可以在這邊進行「影片」的調整,以及「字幕」的顯示

B2 中高級 美國腔

抽水蓄能的真相(The Truth About Pumped Hydro)

  • 3 0
    joey joey 發佈於 2021 年 06 月 12 日
影片單字