Terreno geotermico

Mini-geothermal energy gains ground

The use of small-scale geothermal plants could respond to the electricity needs of many countries worldwide.

by Chris Dalby
09 November 2020
7 min read
by Chris Dalby
09 November 2020
7 min read

Geothermal energy is one of the least-utilized forms of renewable energy globally. Of the 6,586 TWh of electricity generated by renewables in 2018, only 1% was produced by geothermal sources, according to The International Renewable Energy Agency. Renewable sources such as hydro, wind and solar energy have dominated media headlines —and investor wallets— due to their relative ease of implementation, proven track records, and typically lower costs than geothermal production. Geothermal plants require access to a high-temperature resource inside the Earth like steam or very hot water.

One main impediment to building geothermal power plants is the necessity of drilling through hard to break igneous and metamorphic rock, and the associated costs of specialized drilling. This contributes to the capital required to develop a plant. For example, a 40 megawatt (MW) power plant was estimated in 2001 to cost between US$42.5 and $67.7 million to build. As early as the 1980s—which saw an increase in geothermal energy interest due to the global gas crisis—the technology was thought of in terms of providing gigawatts of power.

This made the expensive-to-build plants unsuitable for many smaller applications. But small-scale geothermal power plants can now be developed to provide under 5MW of power. And while this technology has been available for some time, low costs and a high degree of flexibility are now making it an increasingly attractive option. Like any technology, the explosion of mini-geothermal began when it found its niche, either backing up existing large-scale geothermal infrastructure or offering a real chance at energy independence for remote or off-grid communities.

Geothermal innovation in Iceland

Whether it's solar panels, wind farms or small-scale geothermal production, the quest for countries and communities is the same: energy independence. Using geothermal energy to achieve independence, however, is often dependent on natural resources and how accessible they are. Iceland produces 25% of its energy from geothermal plants, and 90% of its population relies on heat from this source, most of which comes from large-scale facilities. The island's largest energy generator, the Hellisheidi power station, stands at 303MW and is the sixth-largest geothermal plant in the world.

The Hellisheidi geothermal power station

The country's abundance of geothermal wells have made small-scale geothermal plants a feasible option as well. Mannvit, an Icelandic energy company, is planning for a number of facilities to provide alternatives to their larger-scale counterparts. Mannvit's geothermal division manager, Kristinn Ingason, recently spoke about the development of smaller, portable plants that use the residual heat from their larger plants. She explained that facilities known as wellhead stations are designed to use geothermal energy at lower temperatures, which typically goes unused by larger installations like Hellisheidi. They are built next to geothermal wells in order to utilize the high pressure coming out of the ground to generate energy.

Powering remote communities

One of the most advanced projects for small-scale geothermal plants designed for remote communities is a joint Dutch-Indonesian project, known as MiniGeo. About the size of a shipping container, this plant runs round the clock, emits next to no CO2 and provides between 100kW and 1MW of electricity. If Technology, the company behind MiniGeo, already boasts significant experience in the larger geothermal market thanks to its realization of one important fact: mini-geothermal could provide a real chance for remote communities to become energy-independent. According to the company, their plants can democratize power consumption, allowing remote communities a lower-cost alternative to an expensive central grid.

They can also serve as a green option to replace diesel generators these communities often depend on, especially in developing countries. While the mini-geothermal plants are not intended to be competitive with structured grids, “In an off-grid scenario, this doesn't matter because there is no grid connection. In this scenario, the MiniGeo is a very competitive power source," wrote Think GeoEnergy, a geothermal news site. Comparing costs to other types of off-grid conventional and renewable energy solutions, mini-geothermal has the advantage. The MiniGeo plants run at $0.1-0.2 per kilowatt/hour, compared to $0.3 for off-grid solar panels and $0.5 for diesel generators.

Indonesia's island of Haruku will be the first to try MiniGeo to replace diesel generators producing 1.5MW of energy for around 25,000 inhabitants. Other examples of self-contained small-scale geothermal power plants have been seen in Japan, but small island communities seem to be ideal targets. While planned geothermal plants in the Solomon Islands and Vanuatu have fallen by the wayside, several Caribbean islands may soon benefit.

What's next?

The small-scale geothermal market has its early adopters, but these often are because individual cities or regions believe in the concept, rather than adoption being part of a national energy strategy. There are still technological and business challenges to overcome, but the versatility of small-scale geothermal power —whether in offering independence to communities, making use of otherwise wasted energy resources— will surely make it a long-term winning bet.