Niche renewable energy sources, like geothermal and wave, have a key role to play in the transition to net-zero, not least when it comes to stability of supply.
When most people think of renewable energy generation, they imagine massed ranks of wind turbines on wind farms, or perhaps fields full of solar panels.
But wind and solar are far from being the only options for zero-carbon electricity. Indeed, there is a myriad of possible renewable energies: from geothermal to marine energy, hydroelectricity (currently the most widely used renewable), biomass and hydrogen. Many are seeing a surge of investor interest as recognition grows of the potential of some of these more niche power sources to re-shape the renewable market.
Geothermal on the rise
Often known as the 'forgotten renewable', geothermal energy has been getting more and more attention in recent years. Simply put, geothermal energy uses the earth's natural heat to create electricity by taking super-heated water from geothermal hot spots and pumping it to the surface where the steam it produces can be used to spin a turbine.
"Scientists believe if we can tap just 2 percent of the thermal energy found between about 2 and 6 miles deep - depths that are regularly drilled today - we can access 2,000 times the annual energy needs of the U.S.," says Dr. Joseph Moore, the Principal Investigator of geothermal research organization Utah FORGE.
Many believe the United States is the geothermal market with the most potential. But geothermal is currently a relatively small player even in the United States, supplying just 0.4 percent of the country's electricity in 2019. California, which has the most geothermal resources of any state, generates just 5.5 percent of its electricity from geothermal.
Aside from cost, one of the major limitations is that three factors must line up for a geothermal reservoir to provide energy: heat, water, and permeability. But experiments are underway to see if it would be sufficient to meet just two of these three conditions - potentially opening up geothermal potential in areas previously considered unviable.
The Utah Frontier Observatory for Research in Geothermal Energy (FORGE) is one organization looking into whether permeability can be artificially 'created' via so-called Enhanced Geothermal System (EGS) reservoirs. The development of EGS is considered essential if the United States is to meet its target of 60,000 megawatts of geothermal electricity by 2050 (today it produces about 2,500 megawatts).
"Although it is impossible to predict when we will begin producing electricity from EGS reservoirs, the research Utah FORGE is conducting represents an important steppingstone toward widespread development of geothermal energy not only in the United States but across the planet," says Moore. "Everyone should be optimistic."
Developing marine energy
One of the major advantages of geothermal - as opposed to solar and wind - is that it provides a regular and predictable energy supply and does not depend on weather conditions. This advantage is also the case with marine energy, a catch-all term that is usually used to mean generating electricity from turbines driven by tides and waves.
"Wave energy delivers its output at a different time to wind and solar power. If you want to get round-the-clock generation to meet your demand, you need a mix of technologies. And wave and tidal can provide that generation at different times," says Tim Hurst, managing director of Wave Energy Scotland.
At the moment, like geothermal, tidal and wave energy have relatively small footprints - Europe added just 200 kilowatts of wave energy capacity in 2020 compared to 14.7 gigawatts of wind energy. But the potential to upscale is immense.
Scotland harnessing its oceans
Scotland's position perched at the top of Europe gives it a particular geographical advantage when it comes to marine energy. "There is a huge resource for tidal and wave in Scotland - the biggest in Europe. There are significant resources in those areas. We also have a history of offshore engineering, and we have an offshore oil and gas sector that has a lot of the capability that we would require to deploy this technology," says Hurst. "And in Scotland we have the political will to deploy this that is lacking in other countries."
A major advantage of wave and tidal energy over wind and solar is that it has less of a visual impact - as the platforms and turbines are much less obtrusive, sometimes entirely underwater. The west coast of Scotland is considered a more suitable location for tidal and wave energy, while the east coast is better suited to offshore wind farms.
As much as 10 percent of Scotland's energy needs could be met by wave energy alone, according to some estimates.
Like geothermal energy in the United States, it's clear that wave energy in Scotland will play an important role in helping the country become net-zero, not only by adding another power source but by helping to guarantee stability of supply. "Our plan is that we will be developing the first pre-commercial arrays up to about 2025 and then technology that could be deployed on a large scale by around 2030," says Hurst.
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