Non-conventional renewable energy sources

Now we are using traditional power plants such as oil, natural gas, coal and water power with the consumption of more than 50 billion barrels per year. As world population continues to grow and the amount of fossil fuels begins to diminish, it may not be possible to provide the amount of energy demanded by the world using only fossil fuels to convert energy. That is why it is so important to use such renewable sources of energy as the sun, wind, geothermal energy and others. Research is being carried out in these fields.

Renewable energy sources, also called non-conventional energy, are sources that are continuously replenished by natural processes. A renewable energy system converts the energy found in sunlight, wind, falling-water, sea-waves, geothermal heat or biomass into a form, we can use such as heat or electricity. Most of the renewable energy comes either directly or indirectly from the sun and wind and can never be exhausted, and therefore they are called renewable.

Solar energy: Solar energy systems use radiation from the sun to produce heat and electricity. There are three basic categories of solar energy systems: solar thermal systems use solar collectors to absorb solar radiation to heat water or air for space heating and water heating; solar thermal power plants use concentrating solar collectors to focus the sun's rays to heat a fluid to a high temperature. This fluid generates steam to power a turbine and a generator; photovoltaic (PV) systems use solar cells that convert solar radiation directly into electricity.

Wind energy. Wind turbines use blades to collect the wind's kinetic energy. Wind flows over the blades creating lift, which causes the blades to turn. The blades are connected to a drive shaft that turns an electric generator, which produces electricity.

Hydropower. Hydropower is electricity produced from flowing water. There are two general types of hydropower: conventional hydropower uses water in dams or flowing in streams and rivers to spin a turbine and generate electricity; pumped storage systems generate electricity by moving water between two reservoirs at different elevations.

Geothermal energy. Geothermal energy is energy from the hot interior of the earth. Fissures in the earth's crust allow water, heated by geothermal energy, to rise naturally to the surface at hot springs and geysers. Wells drilled into the earth allow a controlled release of steam or water to the surface to power steam turbines to generate electricity.

It is important that all these advances in developing new sources of energy and improving the old ones help to solve the energy problem as a whole and they do not have negative effects on the environment.

2. Find Russian equivalents to the following English words and word combinations and learn them by heart:

non-conventional;renewable energy;source; oil; natural gas; coal; consumption; per year; fossil fuel; to diminish; to convert energy; geothermal energy; directly; to be exhausted; ray; fluid; photovoltaic (PV) systems; wind turbine; conventional hydropower;geothermal energy; interior; environment.

3. Answer the following questions:

1. What kind of fossil fuels do the traditional power plants use?

2. Why does the amount of fossil fuels begin to diminish?

3. What renewable sources of energy do you know?

4. Can renewable sources of energy ever be exhausted?

5. How is solar energy generated?

6. How is wind energy generated?

7. What factors are very important in developing new sources of energy?

4. Discuss these issues in the group (or write an abstract):

1. Disadvantages of solar energy system.

2. Developing new sources of energy in our region.

Text 5

1. Read and translate the text:

Energy losses

When energy is transformed from one form to another, or moved from one place to another, or from one system to another there is some energy loss. This means that when energy is converted to a different form, some of the input energy is turned into a highly disordered form of energy, like heat. Functionally, turning all of the input energy into the output energy is nigh impossible, unless one is deliberately turning energy into heat (like in a heater). In addition, whenever electrical energy is transported through power lines, the energy in the power lines is always more than the energy that comes out at the other end.

Electricity is transmitted at high voltages to reduce the energy losses in long distance transmission. Power is usually transmitted through overhead power lines (OHPLs). Underground power transmission has a significantly higher cost and greater operational limitations but is sometimes used in urban areas or sensitive locations. Transmission efficiency is improved by increasing the voltage using a step-up transformer, which reduces the current in the conductors, while keeping the power transmitted nearly equal to the power input. The reduced current flowing through the line reduces the losses in the conductor. According to Joule's Law, energy losses are directly proportional to the square of the current. Thus, reducing the current (amperage) by a factor of 2 will lower the energy lost to conductor resistance by a factor of 4.

Energy losses essentially take place in transformers and cables. The efficiency of large power transformers in step-up and step-down substations is quite high and may reach 99 %, but this depends mostly on the real power delivered. A transformer operating at power close to the assigned value has the best efficiency. Medium and low voltage transformers are of different types and their efficiency may range between 90 % and 98 %, again depending on the power delivered.

It is the contrary for cables. Those carrying high current sustain more heating and therefore endure more energy loss because of the Joule effect, which is an increase in heat resulting from current flowing through a conductor. Essentially, electrical current passing through a conductor raises its temperature and this heat flows away as lost energy. This raises design considerations for overhead lines for long distance transmission cables and underground ones, which deliver energy from the step-down substation to the user.

Electricity supply companies generally try to limit energy losses in overhead lines to about 2.5 %. So, the total losses range between 3 % and 5 % between the power plant and the step-down substation. Between the step-down substation and users the losses can be about the same or even greater. Therefore the overall losses between the power plant and users can easily be between 8 % and 15 %, which suggests that there is still some opportunities to improve efficiency in the transmission/distribution system and hence reduce CO₂ emissions.

2. Find Russian equivalents to the following English words and word combinations and learn them by heart:

energy loss; to convert; input energy; output energy; heat; through power lines; long distance transmission; underground power transmission; cost; urban area; transmission efficiency; to flow; directly proportional; to reach; to deliver; electricity supply; to limit; total losses; to suggest; CO₂ emissions.

 

3. Answer the following questions:

1. When do the energy losses occur?

2. Is it possible to turn all of the input energy into the output energy?

3. What is a disadvantage of underground power transmission?

4. Where is underground power transmission sometimes used?

5. Where do energy losses take place?

6. How can energy losses be reduced?

7. What are the overall losses between the power plant and users?

4. Discuss these issues in the group (or write an abstract):

1. Measures for reducing energy losses.

2. Turning all the input energy into the output energy is impossible.