Energy Harvesting
Energy harvesting ( literally translated as energy crops ) is defined as the extraction of small amounts of electrical energy from sources such as ambient temperature, vibration or air currents for mobile devices with low power. Energy Harvesting avoids limitations in wireless technologies by wired power supply or batteries.
Possibilities of energy harvesting
- Micro effects Piezoelectric crystals generate when force is applied ( for example, by pressure or vibration) electrical voltages
- Thermoelectric generators and pyroelectric crystals obtained from temperature differences electrical energy
- On antennas, the energy of radio waves, a form of electromagnetic radiation, are collected and used for energy. An example of this are the passive RFIDs.
- Photovoltaic, electrical energy from the ambient lighting.
- Osmosis
- Some wristwatches are driven by the movement of the wrist. Generally a strong imbalance on an axis through the carrier, the core function of the clock is usually involuntary thereby caused to rotate and the rotational energy mechanically or electromagnetically fed. Variations with linear electric generator, for example, find in torches, in which case usually has to be very intense and therefore arbitrary due to the rather high energy demand of a flashlight, the acceleration of the movable core.
- Floor panels generate power by running over pedestrians. The plate is lowered by up to 1 cm, and was added so that up to 50 watts of power from the system by the weight of people. In Toulouse / France there are, the project -Elec Trott ( Trott -Elec; pavement ƒlectrique - electrical sidewalk ). The energy produced is used to illuminate the road werden.Ähnliches was realized for dance floors and small electrical appliances by a company from Rotterdam.
Energy conversion by the piezoelectric effect
The direct piezoelectric effect converts mechanical pressure into electrical voltage. As an energy producer in particular piezo igniter are known which convert the usually introduced by hand-operated mechanical energy into a spark. More recent applications in this field are radio switches in which the necessary for the coded radio signal energy is also provided by manually operated piezo elements. In the field of autonomous sensors piezoelectric elements can produce the energy required for the measurement method and a possible radio transmission, in which they present vibrational energy change in the " environment", similar to the principle selbstaufziehender watches.
Examples of sensors that should be commented as possible without wiring, are eg rain or light sensors, which are attached directly to the windshield of a car and take advantage of the existing body vibration to produce energy.
Energy conversion by the thermoelectric effect
1821 Thomas Johann Seebeck discovered that between ends of a metal bar, an electric voltage is produced when the rod is a temperature difference ( temperature gradient) prevails. Jean Peltier 1834 found out that, if two conductors are brought into contact with different heat capacities and electronic electrons from one conductor to the flow through an externally applied electric current in the other, this causes a change in the temperature in the conductors. With suitable materials, it is possible thereby to Peltier elements, for example to generate electricity for cooling or temperature differences reverse to generate electricity from temperature differences.
Benefits of thermoelectricity are:
- No moving parts
- Maintenance-free due to the materials used
- Simple reversal of heat flow
- Possible use of natural sources of heat or residual heat
A disadvantage of thermoelectric generators is the low efficiency of less than 10 %. However, it is anticipated that an increase in efficiency is possible through the use and development of new materials in the foreseeable future. Currently, one strives thermoelectric generators also reinforces the use of waste heat, eg in cars, cogeneration plants, waste water treatment plants or waste incineration plants to use.
Energy conversion by photo -electric effect
With the use of the photoelectric effect in photovoltaics, light energy is made by a solar cell directly usable for electrical consumers.
Circuit technology
The tensions and services which are of the generators available, are very small and usually require corresponding analog technology. Corresponding components are on the market. The technique is also available for the amateur with simple means.