The modestly-sized US state of Utah is about to have an outsized influence on the geothermal industry. As of last month, Utah is now home to the world’s first operational geothermal-hydropower plant, and the global energy company Enel has already laid plans to bring this innovative, energy efficient technology to its other facilities around the world.
The new plant could also finally help kick the US geothermal industry into high gear in the US. The country has been a global leader in geothermal-sourced electricity, but the majority of its installed capacity comes from a single state, California, and that includes geyser-based technology with roots in the early 1900s.
What Is Medium Enthalpy And Why You Should Care
Enel describes The Cove Fort plant as a medium enthalpy plant, which basically means that it is located at a less than premium site for geothermal energy recovery (enthalpy is a measurement of heat in a system).
That’s important because the Earth is loaded with low and medium enthalpy sites. The problem is transferring the geothermal energy from these sites into electricity in a way that makes sense financially and technologically.
The two high efficiency systems that use geothermal fluid directly — namely, dry steam and flash steam — can’t be used at low and medium enthalpy sites due to their relatively low temperatures.
The third alternative is to use a system called a binary cycle, which is what Cove Fort deploys. Basically, a binary cycle plant uses geothermal fluid (the primary fluid, aka brine or water) to heat another fluid (the secondary fluid or working fluid).
The US Renewable Energy Laboratory provides this general explainer…
Binary cycle power plants operate on water at lower temperatures of about 225°–360°F (107°–182°C). Binary cycle plants use the heat from the hot water to boil a working fluid, usually an organic compound with a low boiling point. The working fluid is vaporized in a heat exchanger and used to turn a turbine. The water is then injected back into the ground to be reheated.
The key environmental advantage of binary cycle plants is that the two fluids never come into contact or mix with each other. The result is that emissions from the facility are kept to a low or practically zero level.
For these reasons, the Energy Department is among those predicting that binary cycle will dominate the industry in future years.
A More Energy Efficient Geothermal Power Plant
With the new Cove Fort plant, Enel has come up with a way to get the best of both worlds — a low impact, high efficiency power plant.
That’s where the hydropower part of the equation comes in. Simply put, Enel has sunk a turbine into the well that re-circulates spent water back underground, and gravity does the rest.
According to Enel’s statistics from an initial test run earlier this year, the hydro generator offsets about 8.8% of the plant’s energy consumption.
That offset translated into an increase in the plant’s overall output by slightly more than 1,000 megawatt-hours over the July-to-September test period.
But wait, there’s more.
The hydro generator helps to reduce wear and tear on the injection well, by acting as a regulator for brine being discharged back into the ground:
The presence of the generator creates pressure against the brine flow, which reduces the flow’s turbulence into the well, hence minimising the likelihood of any potential damage to the well. The result is a first-of-its-kind innovation that can reduce operational and maintenance expenses, while also having the potential to generate additional revenues.
I know right? Here is Francesco Venturini, head of Enel’s Global Renewable Energies division, enthusing over the potential for bringing the Utah experiment to the rest of the world:
“We are creating innovative solutions that are making renewable energy better, stronger and smarter. As a result we have once again discovered a more resourceful way to maximise plant operations and power generation with the aim of using this technology at our facilities around the world.”
Upcycling An Abandoned Geothermal Area
Enel’s Cove Fort success story also has implications for reclaiming abandoned or played out geothermal sites that formerly relied on steam-type generation.
The Cove Fort site area was thought to be ripe for the picking in 1974, when new federal geothermal regulations were implemented. A dozen or so companies acquired leases on federal, state and private lands in the area and many exploratory holes were drilled, but nothing panned out:
…the high cost of drilling, high corrosion rates, low reservoir pressures, and the apparent limited extent of the high-temperature reservoir led to a premature conclusion by Union Geothermal Division in 1980 that the field was not economic for large-scale electric power production…
Or, almost nothing. From the late 1980’s into the 1990’s the area began producing electricity on a relatively small scale for the Utah Municipal Power Authority, but that facility was sold and shuttered in 2003.
Nothing else happened until Enel came along. It acquired the right to develop the Cove Fort facility in 2007 and opened it in 2013 as a binary cycle plant.
For the record, the global company Ormat Technologies is a partner in the project.
Onwards And Upwards For Enel
Enel (more precisely, Enel subsidiary Enel Green Power North America) also chose the US to log another global first-of-its kind back in 2012, when it started up the Stillwater hybrid facility in Nevada. That plant combines geothermal with solar thermal and photovoltaic technology.
Enel has been on something of a tear in recent years. Back in 2011 it began adding major solar projects to its portfolio, and in 2013 it qualified to bid on geothermal projects under the US Army’s $7 billion renewable energy initiative.
Moves since last January include a solar, wind, and hydroelectricity deal in Peru that adds up to 326 megawatts of utility scale renewable energy, and in October CleanTechnica noted that the company was on track to install 1 gigawatt worth of wind turbines in Oklahoma by the end of 2016.
Last May Enel also won the right to move forward with a distributed solar plan for Minnesota after a judge was convinced that electricity from the 16-site project would be cheaper than natural gas.
Photo (cropped): via Enel
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