As our society depended for so long on nonrenewable energies, the climate emergency finally accelerated an energy revolution. The challenge today is how to store and optimize renewable energy we generate so we can get the most out of them.
Once upon a time, there was a society where almost everything that people possessed needed to consume non-renewable electricity and/or large quantities of fuel. Over time, the people realized that its energy consumption model increasingly expanded the hole in the ozone layer, due to the issuing of something called greenhouse gases.
Soon, this society became aware of what was going on and decided to limit these emissions and try not to increase the global temperature by more than 2 degrees compared to pre-industrial levels. These efforts included the creation of global conferences, CO2 markets, the common use of terms like climate change, zero-emissions processes, energy models, electrification of consumption, hydrogen as an energy vector, sustainable and resilient energy systems, etc. and much more. That society is not too far away and it’s the one we all share.
It’s been a while now since we started to commit to renewable energy. Since then, these technologies have undergone significant development and seen an exponential increase in their installed capacity, including hydraulic power plants as clean energy plants thanks to non-emission generation.
Some of the advances made are spectacular feats of engineering, like the Haliade-X from GE Renewable Energy, in Rotterdam port in the Netherlands, which is one of the most powerful offshore wind turbines in the world, with a capacity of between 12 and 14.7 MW, a 220-meter rotor and 107-meter-long blades, one rotation of which could power a house in the UK for two days.
We’ve also managed to construct photovoltaic plants with as much installed capacity as a combined cycle power plant (power plants that produce gas by combining a gas turbine with a recovery boiler and a steam turbine). For example, the Francisco Pizarro photovoltaic plant in Cáceres has a capacity of 553 MW and covers an area equivalent to 778 football fields.
Now we come to the perennial doubt raised with managing power from the sun and wind: what happens when there is too much renewable energy? And what about when it’s too cloudy or there’s no wind? Because let’s face it – we all want to get home to a cozy house and take a hot shower, whatever the weather.
Here we need to provide a certain context: every developed country has its energy supply assured thanks to two aspects. The first is what’s called the energy mix – the sum of power deriving from generation plants using different technologies (renewable and conventional). The second is the transmission and energy distribution network emanating from these plants. The way the operators of electrical systems achieve the delicate balance between power generation and meeting hourly demand levels still seems an almost magical feat.
When we don’t have sun and wind, we make use of combined cycles, but burning gas to generate electricity makes us feel bad because we’re being as green as we would like to be and we fear that we’re not reaching our European commitments to reduce emissions. In addition, when there is too much energy from renewable resources available, curtailments occur, which is the deliberate reduction in output below what could have been produced in order to balance energy supply and demand or due to transmission constraints.
It would appear that we have hit a ceiling in terms of boosting energy production, but is that really the case? Let’s take a look at some of the most viable solutions for managing the lack or excess of renewable energy in the electricity system.
The solution lies in energy storage systems. Although it may seem surprising, there are several methods for storing energy: compressed air systems, flywheel, hydrogen, thermosolar devices using molten salts, super condensers, etc. However, the solutions grabbing the headlines, and which are one of the assets we insure, are lithium-ion battery containers called BESS (Battery Energy Storage System) and reversible hydropower plants. So what exactly are they and how do they work?
Both technologies present advantages and disadvantages:
1. BESS work by storing electricity in periods of low demand or when there is excess production and releasing it when demand is high or when there are interruptions in the power supply. The charge in these batteries can come from both the electricity grid itself and renewable energy installations (it’s very common to find battery containers in photovoltaic plants). They feature a Battery Management System (BMS) that continuously monitors battery status, controlling factors like charge, temperature and life cycle to ensure safe and efficient operation. One of the differences between BESS and a regular battery is the Energy Management System (EMS) software it uses, which facilitates detection of when it’s time to release stored energy, which enables effective management.
Advantages:
o Constant and reliable electricity supply.
o Facilitate greater penetration of renewable energies in the energy mix.
o Bring flexibility to managing energy demand.
o Categorized as backup systems because they maintain the stability of the network.
Disadvantages:
o Lithium-ion battery cathode materials are not abundant, are expensive to extract and are usually found in developing countries.
o These materials can be harmful to both the environment and people.
o The most worrying aspect from an insurance perspective is their propensity to catch fire (thermal runaway).
o Although costs have fallen significantly in recent years, they remain expensive systems to produce, especially for large-scale applications.
2. Reversible hydropower plants, also called pumped storage power plants, can generate electricity and store it. Electricity production in reversible hydropower plants occurs in exactly the same way as in a conventional hydroelectric plant: a sheer drop in height is used so to make the water turn a turbine. What distinguishes a conventional hydraulic system from a reversible one is its ability, in addition to generating energy, to store it for subsequent use. The plant has two reservoirs, one upstream and one downstream. During periods of low energy demand or when there is excess energy generation, the power plant uses excess electricity to pump water from the bottom reservoir to the top reservoir. The water is stored I the top reservoir and when demand for electricity surges, it’s released, passing through the turbines and generating electricity as it falls back down to the lower reservoir.
Advantages:
o Clean, emission-free energy production.
o Energy flexibility: can easily adjust electricity production in line with demand at all times.
o Responsiveness: a reversible hydropower plant can start generating energy within a matter of minutes. This speed makes it an effective solution for managing sudden demand surges or to offset the loss of capacity from other energy sources, which provides stability to the electricity grid.
Disadvantages:
o Impact on the environment: the construction of the plant and reservoirs can produce changes in the ecosystem and, in turn, affect the local flora and fauna.
o Dependence on water resources: water is a renewable resource, but its availability may be affected by factors such as the season of the year, changes in rainfall patterns or periods of drought.
o Initial investment: although the relative cost of energy is low thanks to its long useful life, the initial construction cost is very high.
Article collaborators:
Sandra Caballero is a risk engineer in the Engineering Area of Mapfre Global Risks. With a total of 20 years of experience, 16 of them have been developed in the industrial maintenance area and the last 4, in the position she currently holds in MGR.
