The energy landscape is changing, is an old solution the answer to our new problem?
We already looked at the basic principles of Pumped Storage Hydropower, in this Article we will explore the topic in more detail.
Renewable energy is increasing its share in the market as the world seeks to reduce greenhouse gas emissions.
Particularly in Australia where we have an abundance of potential for renewable energy. The issue lies in the timing. Renewables are inconsistent, ‘non-dispatchable’ is the term we have heard from the federal government. The sun and the wind cannot be switched on and off as required. As renewables become a bigger and bigger part of the energy mix an intermediate step is needed to store excess energy during peak production and send it to consumers during peak demand.
The obvious choice to fill this gap is Pumped Storage Hydropower offering the largest capacity of the energy storage technologies at the lowest cost per unit. Pumped Storage Hydropower is the bridge to 100% renewable energy for Australia and maybe even 500%.
Now you can see the need! Let’s jump into the world of Pumped storage hydropower to answer all your questions.
Let’s start with the basics: What is pump storage hydropower?
What is Pump Storage Hydropower?
Pump storage hydropower, also referred to as Pumped Hydroelectric Energy Storage (PHES), is a system that stores energy on a large-scale.
If you have ever been a student of geography, then congrats! You know the basic concept of hydroelectric power production.
To understand it better, think of it as using gravity and water to produce electricity.
The water flow down the penstock from the upper reservoir the energy is captured by the turbine as it spins. The spinning turbine is coupled with a generator uses a magnetic field to generate electricity that can be distributed and used by society . The water, the gravitational energy captured flows into a lower reservoir.
Simple, right? But that’s only half of the story of Pumped Hydro
The other half of the Pumped Storage Hydropower story is where the “pump” part of the name enters into play. When there is excess power in the grid the process is reversed, the water in the lower reservoir is pumped back to the upper reservoir using electricity. This captures the energy like charging a battery.
Combined with solar and wind generation, pumped storage hydropower is perfect companion. It adds reliability and dispatchability to the sporadic and opportunistic generating capabilities of wind and solar. It’s no surprise that PSH is making up for over 95% of the world’s energy storage capacity.
What is the technology used for Pumped Storage Hydropower?
Gravity!
We have long been obsessed extracting energy stored in the form of chemical energy by burning them to create heat. Wood, Coal, Oil, Gas.
But what if we tell you that Pumped Storage Hydropower stores energy in the water at high altitudes. Yes! You read it right. It is more commonly known as gravitational potential energy.
Pumped Storage Hydropower implies uneven altitudes to create a difference in gravitational potential energy that is coupled with a turbine to produce electricity. The gravitational potential energy of water at high altitude converts into kinetic energy of flowing water that rotates the turbine to convert the kinetic energy of the turbine to electrical energy.
Some of you may raise a point that “Isn’t PSH on a par with a hydroelectric power plant with a dam?” You’re halfway right!
The journey of generating power and supplying it to homes remains the same. What’s different is the nature using which water is fed to the system.
Conventionally, this is performed using an impoundment facility with a dam storing water from a river. This system requires constant source of water from the river, either as constant inflow or seasonally stored in the dam for when the river flow is low. Pumped storage hydropower does not necessarily rely on any external source of water. It employs a pump that refills the upper reservoir from the lower one after releasing the water to produce electricity.
How does Pumped Storage Hydropower work?
The previous section may have raised some questions in your mind regarding the efficiency of the system. The pumping indeed consumes a portion of the overall power generation to pump the water from the lower reservoir to the upper reservoir.
However, a mindful load balancing can make up for the efficiency. During power production, the excess energy produced can be used to power the pump. The energy that may have othewise been wasted can be stored for later power generation when required. The round-trip efficiency of Pumped Storage Hydropower varies between 70-80% depending on the methods adopted. In some instances where excess energy was efficiently utilized, this figure has also struck the 87% mark.
Substantial rainfall can be a lucky break for the pump and the system to compensate for the decreasing water levels due to evaporation.
The highlight of PSH is remarkable Load Management.
During peak hours of the day, water gushes from the upper reservoir into the turbine, and energy is produced to meet the electricity demand of peak hours. The discharged water is collected in the lower reservoir.
During off-peak hours (late night and early morning), the discounted energy is used to pump water back from the lower reservoir to the upper reservoir to refill it for the upcoming peak hours. This job is often performed by the turbine itself in the case of a Reversible Pump-Turbine (RPH).
*Note* PSH has historically been paired with baseload producers like nuclear power stations where shutdown and start up is slow and expensive. New PSH will be paired with renewables which are at the mercy of the weather. The idea is the same but the peak and off peak times will be different and equally affected by the generation side as the demand side of the equation,
Now, What is a Reversible Pump-Turbine?
Reversible Pump-Turbine Storage Hydropower
Reversible pump-turbine hydropower (RPH) is an economical solution for generating power at a lower cost. As the name suggests, it has a dual property of acting as a turbine during power generation, and as a pump in off-peak hours to pump the water back to the upper reservoir.
RPH goes hand in hand with a reversible generator-motor. It serves as a generator during flow from the upper reservoir and acts as a motor to pump and store water for the opposite cycle.
The intricate design of RPH comes at a relatively high cost. furthermore, specialized electrical and hydraulic systems are required for the operation increasing cost even more. However, it is typical more economical compared to the duplication required for separate pump and turbine design.
Basic Parts of Pump Storage Hydropower
Upper and Lower Reservoir:
Two reservoirs on different heights to enable difference in gravitational potential energies.
Intake Tunnel:
Water flows down this tunnel from the upper reservoir.
Discharge Tunnel:
Water flows through this tunnel into the lower reservoir after passing through the turbine.
Turbines:
The turbines are attached at a lower altitude and are rotated by the force of falling water.
Generators:
Generators are linked to the turbines and convert kinetic energy into electrical energy
Cost of Pump Storage Hydropower
Pumped storage technology provides a long-term and economical energy solution. Unlike other hydroelectric plants, PSH needs fewer turbines to serve in peak hours since it is free from climate dependencies.
PSH can be handy in emergency situations like flooding by acting as a water storage option. In fact, increased water level means that there is no need to pump the water back to the upper reservoir – saving cost!
An efficient load management system in PSH can result in free and even negative electricity costs in off-peak hours. This means that the government pays you for consuming electricity.
Seems unreal, right? This is what Germany did in 2018 when the power generation rate through renewable sources exceeded the consumption rate.
Pumped Storage Hydropower can serve for around 75 to 100 years – although construction can take up to 10 years. Not to mention that the system demands a hefty initial capital investment and a particular geography to establish. Nonetheless, maintenance and operating costs are relatively low.
History of Pump Storage Hydropower
Pumped Storage Hydropower has been contributing to the electric grids for decades. It started off in Switzerland in 1907 and gained a reputation in the 1920s. Initially, it was used as a secondary source of power generation alongside coal and nuclear energy to lend a hand in peak hours. The growth, however, was hindered for a decade after the introduction of gas-fired peaking plants.
But with increasing awareness of clean energy, PSH came back into the limelight and continues to make an impact to date. According to the report of IRENA in 2017, China leads the list with a PSH storage capacity of 32 GW, Japan with 28.3 GW, and the USA with 22.6 GW.
Advantages and disadvantages of Pump Storage Hydropower
Advantages
Disadvantages
- Self-fed source of power generation making it reliable and continuous.
- Effective load management serves consistently in peak hours of demand.
- Serves up to 100 years.
- The largest source of energy storage capacity in the world.
- Independent of climate variations.
- Easy and cheap to maintain.
- Clean, emission-free, and renewable source of electricity.
- Can store water to some extent in flood situations.
- Requires a special geographical location and topography to build.
- Large initial investment.
- Construction can take up to 10 years.
- Pumping consumes energy decreasing the efficiency of the system in comparison to other hydroelectric power methods.
Wrapping Up
Pumped Storage Hydropower is a strong candidate for providing dispatchability as renewable increase. It is also the largest energy storage facility over extended periods – Emission-free!
It is predicted to skyrocket in the future with an estimate of 2000 GW worldwide by the year 2050. Now, it is a matter of time before PSH construction takes off in Australia.