NOVA physics chapter 3 tvwo 3 (tto 3 natuurkunde)

Chapter 3

Energy sources

Anything that can provide a usable form of energy is called an energy source. For example sunlight, wind and natural gas.
Fossil fuels are also energy sources. Petroleum, natural gas and coal provide chemical energy.
Biomass is material originating from plants and animals. It provides chemical energy and produces biogas.
Nuclear fission is the splitting of atomic nuclei. It releases a lot of energy in the form of heat, used to make steam. The generator converts the kinetic energy (of the steam through the turbine) into electrical energy.
Solar energy comes from the sun, that’s a source of radiant energy. A solar collector converts the radiant energy of the sun into heat that is used to heat water. Solar cells convert irradiation into electrical energy.
Geothermal heat is heat from deep in the ground. Two wells extract the heat from the ground and pump it back again.

Energy transition is a new energy system that needs to be created and has to be: sustainable, efficient, large-scale storage and locally produced.

Heating

Heat sources are things such as a boiler, cooker, oven, etc. An electric boiler has a heating element. An electric current passes through the heating element and that makes the heating element warmed up. This turns electrical energy into heat. Such an energy conversion can be represented in an energy flow diagram.

The amount of energy never changes during energy conversion. This is called the law of conversion of energy. One joule of electrical energy gives you one joule of heat. The quality of the energy goes down, it still exists, but is not usable.

Specific heat is the amount of heat required to increase the temperature of 1g by 1 degree Celsius. Water is 4.2 J/(g*C).
Q = c * m * dT  (Q is heat in joules, c is the specific temperature, m is mass in grams, T is the time in between)
Insulating
Insulation of a wall (§3):
Qw = U * A * dT (Q is heat loss per second (j/s), U is the U value of the wall (W/(m2*C)), A is the surface area (m2), T is temperature difference between indoors and outdoors)

Heat transportation:

Conduction: heat spreads through substance (brick or glass). Molecules are passing their kinetic energy from one to another.
Convection: When heating a liquid or gas. The air next to the radiator warms up, heated air rises.
Radiation: everything emits radiation. Tiny packets of radiant energy are passed to the surroundings. More temperature difference makes more radiant energy emitting.

When the heat production and loss are in balance, there is a dynamic equilibrium. Good insulation can reduce the heat loss of a building. (see formula above)
Some ways of insulating are: double or HR++(+) glazing, fill cavities with insulation material, insulate roofs and floors, insulate heating pipes and hot water pipes, or seal cracks with a weatherstrip.

Efficiency

In the formula E=P*t you can see that you can save energy by making the power smaller (energy efficient appliances) or make t (time) smaller by using devices less often or less long.

Efficiency formula:
η = E (or P) useful / E(or P) total * 100% (η is the efficiency in %, E is in joules, P is in watts)