Is There Any Equipment Waste From Geothermal?

Geothermal energy is a renewable energy source that utilizes heat from the earth’s interior to generate clean electricity. In recent years, geothermal power has seen growing interest and development as countries seek to transition away from fossil fuels and reduce greenhouse gas emissions. The United States currently generates over 16 billion kilowatt-hours of electricity from geothermal sources annually, meeting the power needs of about 1.6 million homes.^[1] Global installed geothermal capacity reached just over 17 gigawatts in 2021, and is projected to continue expanding at a compound annual growth rate of 5% in the coming decade.^[2]

However, with the construction of new geothermal power plants comes the question of equipment waste and disposal. Like any energy technology, geothermal has an environmental footprint that must be managed responsibly. This article will explore the lifespan of geothermal power equipment, the waste generated, and strategies for reducing waste and impacts.

[1] Geothermal Energy Factsheet | Center for Sustainable Systems

[2] Global geothermal market and technology assessment

Table of Contents

How Geothermal Power Works

Geothermal power plants use wells and pumps to extract hot water or steam from reservoirs located deep underground. The hot water/steam is brought up to the surface through production wells that can reach several thousand feet below ground. Once at the surface, the hot water or steam is directed into pipes leading to a power plant facility.

In a dry steam power plant, the steam from the geothermal reservoir is piped directly into the facility to spin turbines, which then generate electricity. In a binary cycle plant, the hot water from the reservoir is passed through a heat exchanger, which transfers the heat to a separate closed-loop pipe system filled with a “working fluid” with a much lower boiling point than water. This working fluid – usually an organic compound like isobutane or isopentane – turns to steam, which then spins the turbines to generate electricity. The water and working fluid are kept in separate closed loops during the whole process.

Binary cycle plants are more common because the water that comes up from geothermal reservoirs often contains materials like silica that can damage or corrode turbine equipment over time. The binary design helps isolate the turbine loop from any contaminants or dissolved solids.

Geothermal Plant Equipment

The main equipment used in a geothermal power plant includes:

Production wells – drilled into the geothermal reservoir to bring the hot water or steam to the surface

Gathering system – a network of pipes that carry the geothermal fluid from the production wells to the power plant
Pumps – used to raise the pressure of the geothermal fluid so it can move through the system
Steam turbines – convert the energy of the high-pressure steam into rotational energy to drive an electrical generator

Generators – convert the mechanical energy into electrical energy
Condensers – cool and condense the steam back into water after it passes through the turbine
Cooling towers – allow the hot condensed water to cool down so it can be reused or injected back underground

Other equipment like heat exchangers, separators, air extraction equipment, and reinjection pumps may also be used depending on the specific geothermal plant design (“Inside A Geothermal Power Plant,” https://geysers.com/The-Geysers/Inside-A-Geothermal-Power-Plant). The major steam turbine models used in geothermal plants are designed to handle the high-temperature, low-pressure steam conditions unique to geothermal sources (“Steam Turbines for Geothermal Power Plants,” https://power.mhi.com/products/steamturbines/lineup/geothermal).

Equipment Lifespans

Geothermal systems are known for their longevity compared to other heating and cooling systems. According to sources, the lifespan of geothermal equipment averages between 25-30 years.

Specifically, the ground loop can last up to 200 years before degrading, as noted by Geothermal Heat Pump Life Expectancy and You. The pipes buried underground are extremely durable. The indoor components like heat pumps have a lifespan around 25 years, longer than air-source heat pumps that last about 12 years on average, per Everything You Need to Know About Geothermal HVAC Technology.

While geothermal systems can operate for decades, their lifespans are finite, and equipment will eventually need replacement. Proper maintenance can maximize longevity.

Replacing and Upgrading Equipment

Geothermal power plants contain various equipment like turbines, generators, heat exchangers, and pumps that have lifespans ranging from 20-30 years before needing replacement. Over decades of operation, geothermal plant owners must periodically invest in replacing or upgrading old and outdated components to maintain efficiency and performance (Replacing Heating and Cooling Equipment with Geothermal Solutions).

Some of the major equipment that gets replaced includes downhole pumps, piping, heat exchangers, and turbines. As technology improves, plant operators may choose to upgrade to more advanced and efficient models rather than doing a like-for-like replacement. This can boost the plant’s productivity and capacity while reducing operating costs and emissions (Geothermal – Renewables / Clean Power).

Replacement and upgrade costs vary widely based on the plant size and extent of work needed. A full turbine or generator replacement at a large geothermal plant could cost tens of millions of dollars. At smaller plants, replacing pumps and heat exchangers may cost hundreds of thousands to a few million dollars (WaterFurnace Geothermal Systems | Planned Replacement). Proper maintenance and monitoring can help stagger major overhauls and smooth out capital expenditure needs.

Generating Equipment Waste

Geothermal power plants utilize specialized equipment like turbines, generators, condensers, pumps, heat exchangers, and piping to convert geothermal energy into electricity. Over time, components like turbine blades, pump impellers, and heat exchangers can become worn out or obsolete and need replacing.

Some of the main types of geothermal equipment waste include:

Turbines – The high temperature steam causes blade corrosion and stress cracks. Replaced turbine rotor blades are a key waste stream.
Pumps – Pump impellers experience wear from the abrasive minerals in geothermal fluids. Old impellers and casings are disposed of during upgrades.
Heat exchangers – Scaling and corrosion reduces heat transfer efficiency. Old heat exchanger tubes and plates are discarded when replaced.

Piping – Thermal expansion, vibration, and corrosion causes piping failures over time. Replaced pipes produce metal scrap waste.
Condensers – Condenser tubes corrode and leak over decades of use. Leaking tubes are plugged then replaced entirely during condenser rebuilds.
Electrical equipment – Generators, transformers, and switchyard equipment are replaced when obsolete or faulty. Old equipment becomes electronic waste.

Proper disposal of worn or outdated geothermal equipment can help reduce environmental impacts. However, some waste contains hazardous minerals and metals from geothermal fluids.

Reusing and Recycling Options

While some geothermal power plant components may need to be replaced, there are opportunities to reuse and recycle the equipment to reduce waste. For example, according to a study, geothermal plants can reuse the hot water pumped from underground reservoirs to provide district heating before reinjecting it back into the reservoir. This allows the thermal energy to be used twice – first for electricity generation and then for heating purposes.

Old geothermal power plants can also potentially be converted into underground thermal energy storage systems. As described in a report, retired mines could be repurposed as “giant geothermal heat pumps” to store excess solar and wind energy as heat underground during off-peak hours. The stored thermal energy can then be used again when energy demand rises.

Components like turbines and pipes could potentially be refurbished and used at other facilities. Metals and minerals can also be extracted from some geothermal equipment during recycling and reused. With some creativity and investment, geothermal operators can give retired components a second life.

Proper Disposal Challenges

While geothermal energy produces far less waste than fossil fuel power plants, there are still some disposal challenges when it comes to certain geothermal equipment waste. The most difficult waste to dispose of properly tends to be mineral scale that builds up on piping and heat exchangers over time. This mineral scale contains concentrated amounts of silica, iron, arsenic, mercury, and other substances that can be hazardous in large quantities. Safely containing these minerals and preventing groundwater contamination requires careful disposal procedures.

According to a study published in the AIP Conference Proceedings, proper disposal of geothermal scale waste can cost up to $70 per ton when factoring in transportation and landfill fees. Handling liquid wastes containing heavy metals and chemicals requires additional precautions as well. Proper training and oversight is necessary when disposing of geothermal equipment waste to avoid environmental contamination.

Waste Management Strategies

Proper waste management strategies are critical for handling the equipment life cycles of geothermal plants in an environmentally responsible manner. Some key policies and innovations include:

Reusing and recycling equipment parts where possible. Companies like Ormat have programs to refurbish and redeploy used equipment at new sites (https://energy5.com/exploring-geothermal-energy-solutions-in-waste-treatment[1]).

Safely disposing of non-reusable materials. Geothermal fluid can contain hazardous minerals, so disposal procedures must follow regulations (https://energy5.com/exploring-geothermal-energy-solutions-in-waste-treatment[1]).

Converting waste heat into energy. Binary geothermal plants can capture excess heat for electricity or district heating systems. This reduces the need for separate waste incineration.

Using geothermal energy for waste processing. The heat can pasteurize sludge from water treatment plants and provide heat for waste incinerators (https://energy5.com/exploring-geothermal-energy-solutions-in-waste-treatment[1]).

Exploring new technologies like plasma arc gasification to cleanly process geothermal wastes.

Setting industry regulations on tracking and reporting waste volumes. This allows identification of problem areas.

Researching environmentally benign chemical additives to reduce scale buildup in piping.

With proper strategies, geothermal’s environmental footprint can be minimized while harnessing its many benefits.

Conclusion

As geothermal energy production continues to grow globally, the industry must plan for responsible lifecycle management of equipment and infrastructure. Though the volume of waste is far less than fossil fuel plants, there are still environmental impacts to consider.

With proper recycling, waste-to-energy conversion, and disposal procedures, the geothermal industry can uphold its reputation as a clean and sustainable energy source. Companies should design for disassembly, maximize reuse of components, and collaborate with waste management partners on safe protocols.

The future depends on transitioning rapidly away from coal, oil and gas. Geothermal has an important role to play in decarbonization. But its expansion must balance the planet’s urgent energy needs with stewardship of finite resources. With careful planning and innovation, geothermal can deliver abundant clean energy for generations to come.