Application and Pros & Contras on Geothermal Energy

APPLICATIONS 

Industrial processes

Most of New Zealand’s geothermal energy goes to produce electricity, but it can be used for any processes where heat is required. The main non-electrical user is the Tasman Pulp and Paper Mill at Kawerau, which was built in 1957 and deliberately sited to take advantage of the underlying geothermal field. The heat is used for digesting wood pulp, drying timber and paper, and generating electricity.

Geothermal prawn farming

The world’s only geothermally heated prawn farm was established in 1987 on the banks of the Waikato River, next to the Wairākei power station. The first prawns were imported from Malaysia in 1988, and by 2005 the 5.8-hectare farm was producing about 20 tonnes per year. The farm heats its own water with heat exchangers, which draw heat from the power station’s waste water before it flows back into the Waikato River.

This is a good example of what is known as ‘cascade use’, where geothermal heat has a function past its primary purpose. Cascading improves the overall efficiency of a resource by using its waste products. In the case of the prawn farm, cascading also reduces the discharge of hot water into the river, where it can harm aquatic life.

Horticulture

Geothermal waters are used for heating greenhouses on a small scale (covering 10 hectares in total), especially for the commercial, out-of-season production of vegetables, flowers and fruit. This includes a large greenhouse (0.8 hectares) for growing orchids for export, and another set up to grow capsicums with heat from the Kawerau geothermal field.

Geothermal Energy in Infrastructure & Electricity

Geothermal energy is also used to heat sidewalks and roads in order to prevent freezing in the winter. Most recently, the Netherlands began using geothermal energy to keep bike lanes from freezing in the wintertime, for instance.

 Electricity Generator

§  Flashed Steam Plants — The water “flash” boils and the steam is used to turn turbines.

§  Dry Steam Plants — These plants rely on the natural steam that comes from the underground reservoirs to generate electricity.

§  Binary Power Plants — These plants use the water to heat a “secondary liquid” which vaporizes and turns the turbines. The vaporized liquid is then condensed and reused.

§  Hybrid Power Plants — In these plants, binary and flash techniques are utilized simultaneously.

PROS AND CONTRAS

Pros

Sustainable and Renewable

-The hot water we use will be replaced by rain.

-The heat inside the earth will always be there.

-More heat is made every day in the Earth’s core.

-Independent of weather.

* Hence The heat from within Earth is in no danger of running out.

Geothermal Energy is Cheap

-Geothermal energy is cheap – new power plants can make electricity for

  about the same as coal power plants.

Geothermal Energy is Clean

- No fuel is burned, so there is no air pollution.

- The steam is turned into water and put back into the earth.

Contras 

·         Not widespread source of energy.

·         —High installation costs.

·         —Water can be corrosive to plant pipes, equipment

o    If water not replaced back into reservoir, subsidence can occur.

·         —Some high mineral / metal wastewater and solid waste is produced.

·         —Smelly gasses – H₂S, Ammonia, Boron.

·         —Release of steam and hot water can be noisy.