Canary Islands look to volcanic heat for energy

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Canary Islands look to volcanic heat for energy

On the threshold of the fifth anniversary of the eruption that transformed the landscape of La Palma for ever, volcanism is once again at the centre of the Canary Islands’ energy debate. Not because of the threat of a new eruption, but because of the possibility of harnessing the heat that remains beneath the ground to produce electricity. Yet one question is on Canarians’ minds: can the subterranean heat of volcanoes be turned into a source of energy capable of replacing fossil fuels? The answer is beginning to take shape.

139 researchers back geothermal development

A total of 139 researchers, scientists and specialists linked to universities, public bodies and research centres in the Canary Islands, the rest of Spain and other countries have signed a manifesto defending the responsible development of geothermal energy in the archipelago. The statement comes just days after drilling carried out in Vilaflor de Chasna confirmed the existence of a deep hydrothermal system with characteristics suitable for energy use.

Unlike solar or wind power, which depend on weather conditions, heat from beneath the ground provides baseload energy that is firm, constant and manageable 24 hours a day. Geothermal energy is an exceptional candidate to finally shut down the thermal power stations that burn fueloil and diesel to keep the electricity grid going when there is no wind or no sun.

Why isolated grids make geothermal attractive

This is an advantage, because the archipelago has a problem that shapes its energy transition: its electricity systems are isolated. Unlike mainland Spain, if the wind stops blowing on an island or night falls, there is no way to call on electricity from France or Portugal through large interconnections to cover the shortfall. That forces a heavy reliance on thermal power stations burning fueloil and diesel — expensive, polluting fossil fuels that remain necessary to ensure the lights stay on when renewables are not enough.

Geothermal energy, by contrast, does not depend on whether it is night or day, whether it rains, the wind blows or there is a calima. The heat is there, beneath the ground, and can be converted into electricity constantly. Add to that another advantage that is especially important for an island territory: energy independence. The Canary Islands spend hundreds of millions of euros a year importing fuels that arrive by ship from abroad to keep their electricity system running. The geothermal resource, if it is finally shown to be exploitable on a commercial scale, would instead be 100% homegrown. The heat would not have to be brought in from anywhere; it would be right under the islands’ feet.

A long road from exploration to generation

But it is no light undertaking. The development of deep geothermal energy, with boreholes that can exceed 2,000 metres, requires different phases of research and exploration before it is known whether a given resource can be used to produce electricity profitably and safely. It is necessary to understand what is happening beneath the subsoil, locate the reservoirs, study their temperatures and characteristics and verify, through successive drillings, whether there is enough of a resource to develop an energy installation. The Canary Islands are at that turning point right now.

After years of research and drilling, the latest results are beginning to sketch out a scenario in which volcanic heat could cease to be merely a geological characteristic of the archipelago and also become a source of energy. According to the Royal Spanish Academy, geothermal energy is a set of internal phenomena of the Earth. Its second definition is the scientific study of geothermal energy, considered as a source of power. In reality, though, it goes further than that.

What geothermal energy is and why the islands suit it

Geothermal energy is a form of renewable energy that harnesses the natural heat of the Earth’s interior. It is based on exploiting the temperature of the subsoil to generate electricity or heat. Although the potential of geothermal energy is conditioned by the geological characteristics of each territory, the Canary Islands offer particularly favourable conditions for its development thanks to their volcanic terrain. The heat can be found at relatively accessible depths.

When temperatures are sufficiently high, underground water can turn into steam and be used to drive a turbine connected to an electrical generator. In this way, the thermal energy stored beneath the ground is transformed into electricity. In other cases, when temperatures are lower, the heat can be used directly for heating, hot water or certain industrial processes.

One of the main advantages of geothermal energy is that, unlike other renewable sources such as solar or wind, it does not depend on the sun shining or the wind blowing at a given moment. A geothermal installation can produce energy continuously, 24 hours a day, as long as the resource is available and properly managed. It is also a source of energy that takes up relatively little surface space and can help reduce fossil fuel consumption and the emissions associated with electricity generation.

€105 million from European funds

The roll-out of this new energy source has a historic investment of around €105 million from European funds, channelled through programmes such as the IDAE’s Deep Geothermal scheme. These resources will make it possible to launch the first major prospecting and drilling campaigns in the Canarian subsoil. The research will initially focus on Tenerife, Gran Canaria and La Palma, the three islands with the best geological conditions for locating high-temperature geothermal resources. Each has millions of euros allocated to determining whether that potential can become a stable source of electricity generation.

Tenerife leads the way at Vilaflor

Relevant steps have already been taken in Tenerife. The public-private consortium Energía Geotérmica de Canarias (EGC) has identified signs of a significant geothermal resource at a depth of some 2,300 metres in the municipality of Vilaflor. The next challenge will be to confirm through further drilling whether that resource is technically usable and can support a future generation plant. The timetable the promoters are working to sets 2029 as a key horizon. If the exploration campaigns and drillings confirm the existence of an exploitable resource, that could be the year the Canary Islands’ first geothermal electricity generation plant comes into operation.

The interest in this technology goes beyond producing electricity. The islands’ energy system remains highly dependent on imported fossil fuels, which makes generation more expensive and increases the system’s vulnerability to fluctuations in international markets. Geothermal energy would make it possible to incorporate a homegrown, constant source capable of producing energy 24 hours a day, reducing that dependence. Moreover, compared with the large areas required by some renewable installations, geothermal energy takes up relatively little land — a particularly relevant factor in an archipelago with a high proportion of protected spaces.

If the drillings confirm current expectations, the Canary Islands could find themselves facing a strategic opportunity: turning their own volcanic nature into a clean, stable and homegrown source of energy.

The hurdles facing geothermal energy

An energy source like geothermal power requires major investment, complex drilling and very precise knowledge of what is happening thousands of metres below ground. Add to that the possible environmental impacts, the technical difficulties and, above all, the need to secure the backing of the communities living alongside the projects.

1. High financial risk: the so-called ‘mining risk’

One of the main obstacles is economic. Before knowing whether a geothermal deposit can produce electricity, the subsoil must be drilled and explored, and doing so at great depths can mean investments running into millions. The problem is that a borehole does not guarantee finding a usable resource. It may turn out that the water temperature is insufficient, that the flow rate does not reach the necessary level or that the characteristics of the reservoir make commercial exploitation unviable. In such cases, much of the investment made during exploration may not be recovered. This is what is known as ‘mining risk’: spending large sums of money without yet having certainty that there is an energy resource beneath the ground that can be exploited profitably.

2. The impact on the landscape

Geothermal energy has a relatively small footprint once the plant is up and running, but the exploration phase is far more visible. Drilling campaigns require heavy machinery, work platforms, access roads and auxiliary installations that can temporarily alter the landscape. In the Canary Islands, where land is limited and much of the ground has some degree of protection, this issue takes on particular importance. What is more, some of the places with the greatest geothermal potential are in surroundings of high scenic and tourist value. The challenge, therefore, is to reconcile subsoil research with protection of the territory and to minimise the impact of the works as far as possible.

3. Protecting water resources

Another aspect that demands greater guarantees is the protection of groundwater. The Canary Islands depend to a large extent on their aquifers, water galleries and wells for fresh water, so any activity involving drilling into the subsoil must be carried out under strict controls. Geothermal wells pass through different layers of ground and can reach water reservoirs at high temperature and with a high concentration of minerals and salts. For that reason, the correct construction and sealing of the boreholes is essential to prevent communication between different subterranean levels and to avert possible effects on aquifers. It is not just a question of finding heat: it must also be guaranteed that exploration and subsequent exploitation are carried out without compromising a resource as strategic as water.

4. The risk of induced seismicity

Geothermal activity can also generate small seismic movements, especially in certain systems that require the injection of fluids under pressure into the subsoil. By altering the pressure conditions of deep rocks, microseisms can occur. According to experts, in a volcanic territory like ours, where seismic activity is part of the islands’ own geological dynamics, this aspect requires particularly careful monitoring. Continuous monitoring of seismic activity and control of pressures during operations are therefore essential elements in reducing and managing this risk.

5. Corrosion and wear on equipment

Heat is not the only element that makes exploiting the resource difficult. Geothermal fluids can contain high concentrations of salts, minerals and gases that are especially aggressive to the materials used in wells and generation installations. This composition can cause corrosion, scaling and wear in pipes, valves, heat exchangers and other components. The consequence is higher construction and maintenance costs, since resistant materials must be used and systems designed to work for years in extreme conditions. It is one of the technical challenges that will determine the extent to which a geothermal resource can be not only usable but also economically competitive.

6. The social and administrative challenge

And there is one final obstacle that is not beneath the ground but on the surface: social acceptance. Most of the nuisance and impacts of a geothermal project are concentrated precisely during the early phases, when electricity is not yet being generated. For months or even years, residents may live alongside heavy machinery, noise, vehicle traffic, drilling and temporary changes to the landscape without yet receiving the benefits of the future installation. That time lag can fuel local opposition and complicate the processing of projects. In small territories, where available space is limited and there is a high sensitivity towards the landscape and natural resources, securing the backing of local communities can become a decisive factor.

For that reason, the development of geothermal energy does not depend solely on finding a resource beneath the ground. It will also be necessary to explain its risks transparently, establish environmental control mechanisms, guarantee the protection of water and the territory and involve the affected populations in the benefits it may generate. In short, the great challenge of geothermal energy is to demonstrate that the heat beneath the islands can be turned into energy without shifting its environmental, economic and social costs onto those who live above it.

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