Compared to intermittent renewables such as solar and wind, hydropower is currently somewhat overlooked in the conversation about green energy.

Nevertheless, it is still a power source with a long and considerable track record and will be a necessary component in realising the common goal of net zero emissions. The International Energy Agency (IEA) forecasts that hydropower capacity will need to double by 2050 to achieve the target of limiting global temperature rises to 1.5°C.

Hydropower is unusual among renewable energy sources as it is not intermittent. Instead, it provides a steady, consistent source of power that can easily be handled by electricity grids. Crucially, it is not dependent on weather conditions like those that affect solar and wind power. Overall, hydropower accounts for 60% of the world’s renewable energy production. Yet despite its reliability, it is deemed the ‘forgotten giant’ of renewables.

Another advantage of hydropower is that it can be paired with other renewables. For example, the reservoirs at the Linth-Limmern power stations in Linthal, Switzerland, are connected to a nearby solar farm. This ensures that the shortcomings of solar (namely its intermittency and reliance on optimal weather conditions) are mitigated by the consistent delivery from pumped storage hydropower.

An investment in affordable energy 
An essential but often neglected characteristic of hydropower plants is their sustainability. This can be understood not only in terms of their environmental impact, but also in terms of their longevity and profitability in the medium to long term. Hydropower plants typically have lower maintenance costs than other renewable energy facilities.

Considering their many benefits, there are plenty of reasons to refurbish the many ageing and outdated hydropower stations in Europe. A successful recent example is the Bitsch power station in Wallis, Switzerland. An integral piece of energy infrastructure in the Swiss grid since 1969, the power station was approaching the end of its life when the decision was taken to upgrade it.

The restoration of two 120 megavolt ampere (MVA) vertical synchronous generators has vastly improved the efficiency and flexibility of the power station, which is the sixth largest hydropower plant in Switzerland. As a result of these upgrades, the 340 MW power station was granted a new lease of life and will now deliver power until 2048.

Why upgrade hydro infrastructure?
As a hydropower plant ages, its key components tend to wear out, become prone to failure and generally do not function at their original level. Refurbishment not only increases the lifespan of a plant, but it can also enhance safety and potentially offer better performance.

One of the best reasons to invest in hydropower is that so much of the infrastructure already exists. Therefore, it is the case of adding to or upgrading an existing system, compared to building from scratch. For example, a non-powered dam could be converted into a hydropower station with minimal disruption to the surrounding ecosystem.

Hydropower plants are highly flexible. The production of energy can be raised or lowered with ease and plants can be energised and powered down relatively smoothly. Today’s electricity market largely depends on flexibility, and this hands hydropower an advantage over solar and wind – demand for power is never static, so the capability for a dynamic response is valuable.

Pumped storage hydropower offers particular flexibility. It is a system comprising two interconnected reservoirs at different elevations that offers an immense capacity for energy storage. In fact, pumped storage hydropower plants account for 85% of the global electricity storage capacity (190 GW).

An example of this in action is the case of the Nant de Drance ‘natural battery’ plant in the Swiss Alps. When the demand for electricity is high, water is released from the upper reservoir, down a series of 425 metre penstocks to the six 150 MW reversible Francis turbine-generators in the power plant. When power demand is low, such as at night, the turbines reverse and water can is pumped back up to the upper reservoir, ready for use during the next period of peak demand. Previously, this kind of flexibility was only achievable with fossil fuels, highlighting the significance of hydropower’s role in the green transition.

Abundant existing infrastructure and greater flexibility than other renewables are major incentives to ensure the modernisation of older hydropower plants.

One of the best reasons to invest in hydropower is that so much of the infrastructure already exists. Therefore, it is the case of adding to or upgrading an existing system, compared to building from scratch.

Hydropower infrastructure is ageing
Despite its proven capabilities, hydropower infrastructure is ageing. The major hydropower construction wave in the developed world took place from the 1960s to 1980s and around 40% of the global fleet is now 40 years old.

The exact age depends on region. China has the youngest fleet (an average of 15 years old), while the North American fleet is the oldest, with 70% of plants being over 40 years old. European and Eurasian (mostly in Russia) plants are only slightly less old, with 60% of the total fleet also being over 40 years old.

Once a plant reaches between 45 and 60 years old, it must be upgraded to bring its performance and flexibility in line with modern standards. This ageing infrastructure provides the majority of many nations’ renewable energy. As these countries increase their transition away from fossil fuels, this investment will become more important.

But operators can go beyond just upgrading essential plant equipment, such as pumps. Digitalising hydropower infrastructure is an excellent way to improve a plant’s flexibility and efficiency. Adding digital, data-driven solutions also increases safety standards through enhanced and more precise central management. This means issues such as flood control and drought management can be dealt with more effectively.

The extent to which a plant can be modernised is largely dependent on a country’s regulations. On the other hand, countries with liberalised energy markets are at the whims of private operators – the returns must be deemed sufficiently worthwhile to justify the investment and losses of revenue incurred during the enforced downtime.

It is also important to ensure that plant refurbishments are planned in advance. Environmental and water regulations may well have changed since the plant opened, so operators must consider whether their plans conform to these standards. In addition, water flows may have changed since the plant began operating, so this needs to be considered. Understanding both of these in advance will mean less friction down the line.

Upgrading plant infrastructure: best practices 
Renovating a hydropower plant requires considerable planning. Here are some best practices to ensure success.

• Understand your current situation. Right from the start it is important to take stock of the plant’s current inventory and status. This means accounting for all components and their conditions. At the very least, operators should monitor the temperature of their turbines, generator stators and generator bearings. The output requirements for the plant should also be at the forefront of any renovation.
• Know what the goals are and set priorities. During the planning stage, it is key to articulate what goals the renovation is designed to achieve. By doing this, decision makers and stakeholders will be able to budget with an end result in mind. But setting a budget early on is still important – it will force decision makers to set clear priorities and time frames for action.
• Find out what is available. As mentioned above, renovations are not just a chance to maintain plants, but to upgrade them with modern technological innovations. Digital solutions to enhance plant management should be explored and cross-referenced with current inventory. This way, decision makers will easily be able to identify opportunities for modernisation.
• Be proactive. To make future upgrades even easier, decision makers should plan the current renovations with future developments in mind. This means planning upgrades that are forward compatible. Systems with forward compatibility are designed to process some of the data their future versions will use, effectively future-proofing the plant.

From the past to the future
The revitalisation of global hydropower fleets should be a top priority during the energy transition. As the world economy moves to reduce dependency on fossil fuels, we need a reliable, affordable source of renewable energy – we have this in hydropower.

Because the infrastructure is largely in place, the expansion of hydropower is far easier than building new energy infrastructure. What’s more, hydropower is not intermittent, meaning that it is not weather-dependent and is always reliable. Far from competing with them, the existence of hydropower actually enables the expansion of other renewable sources such as solar and wind.

Upgrading plants is something that must be planned in advance. As such, decision makers must stay abreast of the changes to environmental and water regulations that have occurred since the plant began operations.

The flexibility of hydropower means that nations can produce reliable, sustainable energy themselves without disrupting ecosystems or being reliant on imports. In an era where both the environment and energy security are of great concern, this is an invaluable option.