Geothermal Energy — The New Way to Invest in Heat
Geothermal energy is heat (the "thermal" part of the word) derived from the Earth (the "geo" part). It is the energy contained in the hot rocks, and the hot fluids that fill the fractures and pores within the rocks, of the Earth's crust. Under the right conditions, geothermal energy can be utilized to generate electricity, and this is why we are interested.
According to thermodynamic calculations performed by many bleary-eyed graduate students over the decades, if the Earth had simply "cooled" from a molten state, it would have become a completely solid mass of iron and rock within a few hundred million years of its formation. But the Earth has been an active, dynamic planet for nearly 4.5 billion years, so something must be going on deep inside to keep the planet hot. The current belief is that the source of heat energy within the Earth is long-term radioactive decay occurring within the crust and mantle.
The uses to which these geothermal resources can be put are controlled by temperature. The highest-temperature resources are generally used only for electric power generation. Current U.S. geothermal electric power generation totals approximately 2,800 megawatts (MW), or about the same as five large nuclear power plants. Uses for low- and moderate- temperature resources can be divided into two categories: Direct use and ground-source heat pumps. I am not going to say that geothermal energy is infinite in scale, but the heat sources within the Earth are immense, and a well-managed program has the potential to be operational for many decades, if not centuries.
The Pros and Cons of Geothermal Power
Now that we have looked at the basic engineering of geothermal power, let's look at the business and policy side of things. First, you should understand that extracting the Earth's heat and selling geothermal power is subject to the same regulatory structures as almost all other energy-generation and transmission entities in the country.
Also, geothermal energy is capital-intensive; hence, it takes time to pay off any major investment. At the same time, geothermal power competes against the rest of the electrical grid. This means that the cost basis for a geothermal power plant has to be competitive against plants that produce electricity by burning coal, natural gas, or even oil, as well as the recently growing solar thermal energy industry.
There is plenty of good news for geothermal energy, though. Once a plant is up and running, geothermal power is quite reliable. Geothermal plants offer a continuously available (24/7) power source, with historic reliabilities in excess of 90%, which is comparable to the reliability of many nuclear plants. Compare this with wind-generated power at 25-40% reliability (the wind does not always blow when you need it), or solar-generated power at 22-35% reliability (the sun sets each night, among other drawbacks). Reliability is a critical issue in terms of operations, because plant owners usually bear the risk of getting charged back by utility customers for what is called shortfall energy. This means the power that a utility purchases on the market if the main source is not operating up to capacity.
There is more good news for geothermal, in the form of policy support. Geothermal energy does not deplete like an oil or natural gas deposit. Many hot springs of the world have been bubbling warm water or steam since prehistoric times. So geothermal power is considered a renewable form of energy production, and in our own era, it benefits from the renewable energy "production tax credit." The production tax credit, plus five-year depreciation schedules, means that there is an effective U.S. government subsidy of over 63% of the capital cost of renewable energy projects. (Think of it as spending dollars that cost only 37 cents.) So right away, renewable energy projects, and geothermal projects in particular, are beneficiaries of significant investment tax breaks that would make any oilman jealous.
If you scan the market, you’ll be hard pressed to find pure-play geothermal companies. But as the technology takes hold, more and more of the companies will pop up on your radar.