Topic 23: Energy

All living things require energy to do the work necessary for survival and reproduction. But what is energy? Energy is simply the ability to do work, (1) ____ work is done when a force moves an object. Let’s consider your own needs for a moment. You need energy to turn on and turn off your computer. You need energy to (2) ____ of bed in the morning. And, yes, you need energy to reproduce. So where does energy come from and how do we use it? On Earth, energy ultimately comes from the sun. Plants use the sun’s energy to make sugar. Organisms, in turn, use sugar as a (3) ____ of energy to do work.

Plants use energy from sunlight to make sugar and oxygen from carbon dioxide and water. The process by which carbon dioxide and water are (4) ____ to sugar and oxygen using sunlight is referred to as photosynthesis. This is an endergonic reaction, meaning energy is required by the reaction. Specifically, energy is required to put the carbon dioxide and the water molecules together to form sugar. Sun (5) ____ the energy needed to drive photosynthesis, and some of the energy used to make the sugar is stored in the sugar molecule.

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Water is of vital importance to all living things. Without it, all living things will surely die. We also use a great (1)_____ of water daily in our homes, in factories, and in power stations. Most of this water is fresh water and it comes to us from reservoirs, rivers and lakes.

The Earth’s surface is (2)_____ by large areas of water which we call oceans and seas. If you have tasted the water from the sea, you will know that, unlike fresh water, seawater tastes salty. This is due to the (3)_____ of sodium chloride which comes from the land. Rivers carry it to the sea.

Although (4)_______salt nor fresh water has (5)________color, the sea often looks blue in the sunlight. The reason is that sunlight is made up of many colors. Some colors disappear quickly in the sea but blue light bounces back or is reflected, to the surface. This makes the sea look blue. Hence, a stormy sky will make the sea look grey.

After years of hype and false starts, the shift to clean power has begun to accelerate at a pace that has taken the most experienced experts by surprise. Even leaders in the oil and gas sector have been forced to confront an existential question: will the 21st century be the last one for fossil fuels?

It is early, but the evidence is mounting. Wind and solar parks are being built at unprecedented rates, threatening the business models of established power companies. Electric cars that were hard to even buy eight years ago are selling at an exponential rate, in the process driving down the price of batteries that hold the key to unleashing new levels of green growth.

“This clean energy disruption has just started and what is striking is how much of a financial impact it is already having on some companies,” says Per Lekander, a portfolio manager at London’s Lansdowne Partners hedge fund, who has tracked global energy markets for more than 25 years.

“It hit the electricity sector first, in Europe in 2013 and then the US two years later. Now it has spread to the auto sector and I think the oil industry is next.”

The shift has come as increased government efforts to curb climate change and smog have driven down costs and spurred technical advances, creating a green energy industry that looks nothing like it did a decade ago: expensive and sluggish.

Today, China and India have picked up the baton and are driving a sector that has spread to every continent. The result was a banner year for green energy in 2016.

Geothermal energy is the heat from the Earth. It’s clean and sustainable. Resources of geothermal energy range from the shallow ground to hot water and hot rock found a few miles beneath the Earth’s surface, and down even deeper to the extremely high temperatures of molten rock called mác-ma.

Almost everywhere, the shallow ground or upper 10 feet of the Earth’s surface maintains a nearly constant temperature between 50° and 60°F (10° and 16°C). Geothermal heat pumps can tap into this resource to heat and cool buildings. A geothermal heat pump system consists of a heat pump, an air delivery system (ductwork), and a heat exchanger-a system of pipes buried in the shallow ground near the building. In the winter, the heat pump removes heat from the heat exchanger and pumps it into the indoor air delivery system. In the summer, the process is reversed, and the heat pump moves heat from the indoor air into the heat exchanger. The heat removed from the indoor air during the summer can also be used to provide a free source of hot water.

In the United States, most geothermal reservoirs of hot water are located in the western states, Alaska, and Hawaii. Wells can be drilled into underground reservoirs for the generation of electricity. Some geothermal power plants use the steam from a reservoir to power a turbine/generator, while others use the hot water to boil a working fluid that vaporizes and then turns a turbine. Hot water near the surface of Earth can be used directly for heat. Direct-use applications include heating buildings, growing plants in greenhouses, drying crops, heating water at fish farms, and several industrial processes such as pasteurizing milk.

Hot dry rock resources occur at depths of 3 to 5 miles everywhere beneath the Earth’s surface and at lesser depths in certain areas. Access to these resources involves injecting cold water down one well, circulating it through hot fractured rock, and drawing off the heated water from another well. Currently, there are no commercial applications of this technology. Existing technology also does not yet allow recovery of heat directly from mác-ma, the very deep and most powerful resource of geothermal energy.

(Source: https://www.renewableenergyworld.com)