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)

A Tidal Stream Generation system reduces some of the environmental effects of tidal barrages by using turbine generators beneath the surface of the water. Major tidal flows and ocean currents, like the Gulf Stream, can be exploited to extract its tidal energy using underwater rotors and turbines.

Tidal stream generation is very similar in principle to wind power generation. Water currents flow across a turbines rotor blades which rotates the turbine, much like how wind currents turn the blades for wind power turbines. In fact, tidal stream generation areas on the sea bed can look just like underwater wind farms.

Unlike off-shore wind power which can suffer from storms or heavy sea damage, tidal stream turbines operate just below the sea surface or are fixed to the sea bed. Tidal streams are formed by the horizontal fast flowing volumes of water caused by the ebb and flow of the tide as the profile of the sea bed causes the water to speed up as it approaches the shoreline.

As water is much more denser than air and has a much slower flow rate, tidal stream turbines have much smaller diameters and higher tip speed rates compared to an equivalent wind turbine. Tidal stream turbines generate tidal power on both the ebb and flow of the tide. One of the disadvantages of Tidal Stream Generation is that as the turbines are submerged under the surface of the water they can create hazards to navigation and shipping.

Other forms of tidal energy include tidal fences which use individual vertical-axis turbines that are mounted within a fence structure, known as the caisson, which completely blocks a channel and force water through them. Another alternative way of harnessing tidal power is by using an “oscillating tidal turbine”. This is basically a fixed wing called a Hydroplane positioned on the sea bed. The hydroplane uses the energy of the tidal stream flowing past it to oscillate its giant wing, similar to a whales flipper, up and down with the movement of the tidal currents. This motion is then used to generate electricity. The angle of the hydroplane to the flow of the tide can be varied to increase efficiency.

Tidal energy is another form of low-head hydro power that is completely carbon neutral like wind and hydro energy. Tidal power has many advantages compared to other forms of renewable energy with its main advantage being that it is predictable. However, like many other forms of renewable energy, tidal energy also has its disadvantages such as its inflexible generation times dependant upon the tides and the fact that it operates in the hostile conditions of the oceans and seas.

(Source: http://www.alternative-energy-tutorials.com/)

Coal, oil and gas get more than $370bn a year in support, compared with $100bn for renewables, the International Institute for Sustainable Development (IISD) report found. Just 10-30% of the fossil fuel subsidies would pay for a global transition to clean energy, the IISD said.

Ending fossil fuel subsidies has long been seen as vital to tackling the climate emergency, with the G20 nations pledging in 2009 to phase them out, but progress has been limited. The new analysis shows how redirecting some of the fossil fuel subsidies could decisively tip the balance in favour of green energy, making it the cheapest electricity available and instigating a rapid global rollout.

The transition from polluting fossil fuels to clean energy is already under way. Annual investment in renewables has been greater than that in fossil fuel electricity generation since 2008 and new renewable capacity has exceeded fossil fuel power each year since 2014. But progress is slow compared with the urgency required, said Bridle. “There is no question that renewables can power the energy system,” he said. “The question now is can we transit quickly enough away from fuels like coal, and subsidy reform is a very obvious step towards that.”

Reform of fossil fuel subsidies could have a significant impact on global heating. An earlier IISD study of 20 countries with large fossil fuel subsidies found that a 30% swap to renewables would lead to emissions reductions of between 11% and 18%. Most experts define fossil fuel subsidies as financial or tax support for those buying fuel or the companies producing it. The IMF also includes the cost of the damage fossil fuel burning causes to climate and health, leading to an estimate of $5.2tn of fossil fuel subsidies in 2017, or $10m a minute. Ending the subsidies would cut global emissions by about a quarter, the IMF estimates, and halve the number of early deaths from fossil fuel air pollution.

Bridle said funding fossil fuel subsidies was “madness”, but said ending them could cause short-term price rises and political difficulties, as the benefits of lower costs in the future and reduced air pollution are less obvious. “There are political problems but it is worth persevering because the prize is so big,” he said. “You have to bring people along with you.” Gençsü said governments must ensure that the most vulnerable people were not adversely affected by changes.

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

Once restricted to space stations and satellites, photovoltaics are now gaining popularity and becoming an increasingly viable option. Every day, the sun releases an enormous amount of energy, far more than the entire population consumes. Being that the sun is a sustainable, renewable, and inexhaustible source for generating electricity, not using it seems almost counter-intuitive, especially considering the social and environmental impacts of other forms of energy generation. But the technology to create electricity from the sun is by no means simple and still has some limitations, the most significant being price.

The process of turning the sun’s rays into electrical energy all starts in the so-called photovoltaic cell. These cells are produced with two chemically altered silicon layers of which one is missing elections and the other is electron-overloaded. When the photons from the sunlight reach the surface, these electrons gain the ability to move, generating a flow that creates an electric current. Each cell generates a small amount of energy and a panel is usually made of between 36 and 72 photovoltaic cells. By connecting several panels together, a photovoltaic system is created. Eight to ten panels is enough to power a small house. Evidently, however, this statistic is influenced by some factors, such as the efficiency of the panels, the amount of sunshine in the region, and the energy demand of the residence itself.

Importantly, photovoltaic solar panels produce electricity in the form of direct current, meaning the electricity must pass through an inverter to transform it into alternating current - which is what is normally used in buildings, appliances, sockets, and light bulbs.

Photovoltaic systems can facilitate energy generation in remote locations where infrastructural networks do not reach. In these cases, the system uses batteries to store electricity when less energy is used than is consumed, such as at night or on very cloudy days. However, it is also possible to use photovoltaics in systems connected to the power grid. In these cases, the excess energy goes to the electricity grid, creating energy “credits” for the building in question. In some countries, it is even possible to sell surplus energy, making the building a power plant for neighbors and method of paying off the investment more quickly.

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