Electricity
Electricity - a very special kind of medium
Electricity is the “purest” form of energy used in schools and at home. Although gas and heating oil are used to heat the building, and perhaps to run a combustion motor, electricity can be used for any purpose: for heating, for generating warm water, for lights, for running electric motors, and for operating computers or any of the other communication devices (fax, telephone, even the recess bell).
However, many resources are required to generate and distribute this valuable energy. In Germany, many large and small power plants produce electricity exclusively.
CO2-emission due to electricity
The generation of electricity puts great strain on the climate. Although it is true that electric devices do not emit emissions, it should not be forgotten that within its production process electricity generates pollutants and carbon dioxide. The carbon dioxide emissions from the consumption of one kilowatt of electricity are two to three times higher than the emission from natural gas or crude oil. This is due to the high losses during conversion in the power plant. Emission factors indicate the amount of carbon dioxide generated by energy sources in one kilowatt hour. This includes every single step involved in the preparation of the energy: winning and transport of the energy source, the conversion steps that also require energy, and the actual use on site.
Work and power – still confused?
The amount of electricity consumed on a particular day, week, or year is measured in kilowatt hours. This unit is listed on the power bill and used as the basis for calculation. This unit is comparable to the consumption of litres of heating oil (1 litre corresponds to the amount of energy in 10 kilowatt hours) or cubic meters of natural gas (1m 3 = 10 kilowatt hours).
The term “power” often leads to confusion: power is measured in watts or kilowatts and is shown on normal light bulbs, energy saving lamps, and electric devices as the connected load. The power indicates how much energy is consumed per time unit: a high connected load indicates high consumption per time unit. However, determining consumption depends on the length of time a device is in operation.
For example : A coffee machine has a high connected load of about 700 watts. However, since the coffee is ready in 5 to 10 minutes, it only uses 0.1 to 0.2 kilowatt hours. A television in stand-by mode waiting for someone to switch on may only have a connected load of about 10 watts, but uses a quarter kilowatt hour per day, as much as making coffee twice.
Electricity requirements in the school
Typical power consumption in schools is composed as shown in the figure below. The dominant influence of lighting is obvious.
In very large school buildings with ventilation systems for the rooms, the percentage of electricity used for lighting is lower and the percentage used by the ventilation system is higher. A load measurement can be used for a more detailed examination of the power consumption in the school. The curve visualizes areas with a potential for savings. Moreover, it indicates the load peaks or the times when the most power is consumed (= the highest electric rating used in the school, unit: watt or kilowatt). A typical load curve is shown in the following figure. The connection load during a cloudy winter workday is shown here. The curve starts at midnight and ends 24 hours later. The dominant influence of lighting is obvious during school hours. Even the breaks are noticeable, since the lights are sometimes turned off at these times.
Lighting
Specialists use special terms when discussing lighting. To be able to join in the conversation, remember the following points:
Bulbs are for tulips. Light bulbs and energy-saving bulbs are actually lamps. This refers to an illuminant. Everything else that is normally called a lamp (table lamp, etc.) is the light fixture or the housing. Therefore, this document sometimes refers to incandescent lamps, energy-saving lamps, and fluorescent lamps. These terms do not need to be used in daily conversation, but knowing the correct usage can be helpful in discussion with representatives of the city or the electrician.
normal incandescent lamp(60W); fluorescent or energy-saving lamp (11W)
What ist the difference between the various types of lamps?
Incandescent lamps: A Wolfram wire is heated to emit light, but 95% of the emission is just heat. Incandescent lamps have no business in schools.
Fluorescent lamps: A gas is ionised in the lamp and accelerated electrons trigger an illuminant that radiates visible light. Fluorescent lamps are 5 to 6 times more effective than incandescent lamps. Therefore this lamps are used whern energy-efficient light is necessary.
Energy-saving lamps: These lamps use the same technology as the fluorescent lamps, but are “folded” together and can replace incandescent lamps. To generate the same amount of light as an incandescent lamp, an energy-saving lamp consumes only one-fifth of the power.
Even today it is discussed whether lamps should be switched off for short periods to save electricity. The answer is always: Yes! However, it helps to be able to explain the reasons in detail:
Product life
The product life of an incandescent lamp does not depend on how often it is switched on and off. However, this does not apply to fluorescent lamps. Fluorescent lamps are operated with a converter that supplies the illuminant in the tubes with high voltage. Modern electronic converters cause very little damage to the fluorescent lamp when it is often switched on and off. Old conventional converters, on the other hand, did shorten the life of the fluorescent tubes when they were switched on and off. If the entire system is taken into account, including the energy required to produce new fluorescent tubes, it is still worth switching off the lights for short periods. The new “energy-saving lamps” have electric converters that protect the illuminants during switching, even if these lights are switched on and off constantly for one minute.
Inrush current
To switch on the lights neither fluorescent lamps nor incandescent lamps or energy-saving lamps require much electricity. Therefore, there is also no reason to leave the lights on during a break.
