Geothermal Power Could Become a Good Alternative for Making Electricity

It now makes up just a sliver of the electricity generation pie. But experts at the Massachusetts Institute of Technology say that enhanced geothermal systems (EGS) could have far wider applications and be especially useful in times of high energy prices and carbon constraints. Not only are the systems much cleaner than

fossil fuels but they also provide a continuous flow of energy—all at competitive prices.

Geothermal energy is a very large resource and has the potential to be a significant contributor to the energy needs of the world. Geothermal now provides less than 1 % of the world’s power, although it could supply as much as 20 % in the coming decades.

How Geothermal Power Works? To get there the tools to perfect deep drilling and water flow through the underground navigation system are needed.

Geothermal resources are available nationwide in the USA. But the highest- grade sites are in western states where hot rocks are closer to the surface, requiring less drilling and thereby reducing exploration costs. Once there, those wells must then be linked with natural or induced fractures in the rock to allow the water to flow through.

Water is pumped via the wells through these fractures in the hot rock and up to the surface to run electric generators at the surface. Unlike conventional fossil-fuel power plants that burn coal, natural gas or oil, no fuel would be required. The environmental effects of geothermal power are “markedly lower” than either fossil fuels or nuclear power. And unlike wind and solar systems, a geothermal plant works night and day.

This environmental advantage is due to low emissions and the small overall footprint of the entire geothermal system, which results because energy capture and extraction is contained entirely underground, and the surface equipment needed for conversion to electricity is relatively compact.

It’s not an easy objective, though. It costs a lot of money to drill wells in large part because explorers need to drill deep into the earth, often 5,000 feet or more below the earth’s surface. Meeting water requirements for geothermal plants may be an issue, particularly in arid regions.

Further, the water that is used to create electricity must be kept separate from drinking water supplies to prevent contamination. Additionally, the potential for seismic risk from fluid injection needs to be carefully monitored. The cumulative effect of all those obstacles has led skeptics to conclude that geothermal energy will remain a nominal power source.

Peggy Daniels Becker, Alternative Energy

Make a presentation on one of the alternative sources of energy successfully used in the world.

UNIT ELEVEN

Read the first paragraph of the article. What kind of material are engineers from Stanford University working on?

Read the whole article and mark the statements as true (T) or false (F).

a) The resulting transistors are less than a centimeter thick._______

b) Organic transistors prove to be more efficient than their silicon analogues._______

c) It takes just a little more than two months for the transistor to disappear in a human organism._______

d) Being harmful for a patient, silver wires are not used in making medical electronics. _____

e) There is no need in conducting any further tests to create working devices.___

f) Beta-carotene (the molecule that gives cucumbers their colour) might, act as a semiconductor._________

 

A desirable solution

Biodegradable electronics for medical devices take a step closer

The idea of creating biodegradable electronics for implantation into the human body has been around for a couple of decades, but no one has yet managed to do it. However, Zhenan Bao and Christopher Bettinger, who are chemical engineers at Stanford University, have just made a start. They have created transistors from a sulphur-containing hydrocarbon called thiophene, a polyester called polylactide co- glycolide (PLGA, for short) and polyvinyl alcohol (PVA). All of these chemicals are approved by America’s Food and Drug Administration for human use.

To make their transistors, Dr Bao and Dr Bettinger chopped sheets of PLGA into 1cm squares and deposited thin silver contacts on to them. They then coated the PLGA with thiophene, which acts as a semiconductor, interspersed with PVA, which acts as an insulator. The result is a flexible transistor a few millimetres thick.

Such organic transistors are not as efficient and powerful as silicon transistors, nor are they anything like as small. But they can be manufactured cheaply. More to the point, they break down slowly in warm, salty conditions of the sort found in the body. In laboratory tests intended to mimic the body’s interior, they disappeared after 70 days, leaving behind only the wires - which, being made of silver, are not toxic.

To create working devices it will be necessary to double-check that the other ingredients are not toxic, too, despite their FDA clearance, and also to make the other components of electrical circuits, such as capacitors and resisto rs, in a similar way. Dr Bao is also investigating other compounds with potential uses in this area, such as beta-carotene (the molecule that gives carrots their colour), which she thinks might, like thiophene, act as a semiconductor. If she succeeds, it should be possible to devise electrical control circuits for instruments such as drug-delivery devices that could be implanted and then left alone to do their thing for a month or two before vanishing.

The Economist