Geothermal Energy Source – Renewability & Sustainability

A geothermal energy source is called a renewable resource because set against the Earth’s heat potential any proposed heat removal is negligible. Planet earth has roughly a hundred billion times the total energy consumption of the world in a year (calculated in 2010)….

About 20% of the is residual high temperature from planetary accretion, 80% is related to the higher radioactive rates of decay from the past and the rest is heat remaining from planetary accretion.

Natural heat movements aren’t in balance, and the earth is slowly and gradually trying to cool off on geological timescales.

Geothermal power is also regarded as sustainable because of its capacity to support the Earth’s complicated ecosystems.

Through the use of geothermal resources of energy present, humans over the years won’t endanger the ability of future generations to utilize their own resources in the same way that they are today.

In addition global warming may well be mitigated because of the low emissions that geothermal energy has.

Despite the fact that geothermal electricity is internationally lasting, removal must be supervised to avoid local depletion. During a period of decades, individual wells get lower local temps and levels of water until a fresh balance is arrived at with natural movement.

The 3 oldest sites at Geysers, Wairakei and Larderello have undergone a lower output due to depletion locally.

Water and heat, in an unknown ratio, were extracted quicker than they were replaced. The reduction of production and re-injection of water could, in theory, mean that their full potential could be recovered.

Similar recovery methods have been put into action at some places. Sustainability in the long term has been shown at Lardarello in Italy from 1913.

It has also been demonstrated at the Wairakei field, New Zealand from 1958 and at the California, Geysers from1960.

Dropping electricity creation might be boosted by drilling more resource boreholes, as at Ohaaki and Poihipi.

The power station in Wairakei has been operating much longer, using its first unit back in November 1958, and it gained its peak output in 1965. This was 173MW.

But even then the provision of high pressure steam was starting to fail and the system was rated down to an intermediate pressure and level of 157MW.

Diagram Hot Water Geothermal energy source

This became about 150MW in 2000 and about 5 years later two isopentane systems were added on, improving the station’s productivity by about 14MW.

Following several re-organisations much of the detailed data available was lost. For example one particular re-organisation in 1996 resulted in the lack of data for the early days of Poihipi (began in 1996), and almost all of Wairakei’s history.

Environmental Effects Of A Geothermal Energy Source

Liquids extracted from deep in the earth include an assortment of gases, particularly ammonia, methane, hydrogen sulfide and carbon dioxide.

These gases are responsible for global warming and acidic rain. In addition noxious odors are possible. Current geothermal electric sites emit typically 122 kilograms of Carbon Dioxide per megawatt hour of electricity. This is a small part of that produced from normal fossil fuel processes.

Sites that produce large amounts of acids and volatile chemicals are often fitted with control systems to lessen the emissions.

Furthermore, aside from gases that are dissolved in the hot water water, poisonous elements such as antimony, arsenic, boron and mercury may be found in minute amounts in the geothermal water.

Environmental damage can be caused as these chemicals can come out of solution form the water and solidify during the cooling of the water.

The present day practice of injecting geothermal liquids that have been cooled, back into the planet earth to stimulate production has the advantage of minimizing this environmental risk.

Compressors and pumps in direct geothermal heat systems may require energy from a polluting source.

This parasitic amount of energy is a small percentage of heat productivity normally, so it is obviously less polluting than heating up electrically.

However, if the electricity is made by igniting fossil fuels, then the final emissions of this geothermal energy source may be compared to that of burning the fossil fuels for heat directly.

For instance, an electrical geothermal heat pump (powered from from a natural gas plant) would emit just as much pollution as a furnace of the same size (a natural gas condensing furnace).

So the environmentally worth of direct geothermal heating processes is highly reliant on the emissions strength of the relevant electric grid.

Land stability can be compromised by the construction of new sites. For example, the Wairakei field in New Zealand has experienced subsidence.

Earthquakes can be caused due to hydraulic fracturing with certain geothermal systems.

Basel, Switzerland was where the suspension of a project happened because of more than 10K events being measured on the Richter Scale over six days of water injection treatment.

A geothermal energy source has nominal freshwater and land requirements.