Usually, the counterweight to be calculated in elevator construction consists of the empty mass of the elevator car plus half the payload. This means that the elevator can recover energy both when it is loaded going down and when the empty elevator car is driven up via the elevator motor. This energy is lost when braking systems are used. The regenerative return of energy to the grid is only possible via a regenerative frequency drive (VVVF). Using graphene ultracapcitor technology for the Kinetic Energy Recovery System (KERS) to recirculate and store the energy means the energy can be recalled from the ultracapacitor pack when the elevator consumes again.
The KERS can be applied to new installations or retrofitted to existing lifts. As a rule, the systems have a capacity of up to 15 KW. If, however, a higher demand for stored energy is necessary, it can be achieved by installing multiple ultracapacitor systems in parallel.
"There are around 640,000 passenger elevators and 110,000 freight elevators in use in Germany today. Even with cautious estimates, hundreds of millions of elevator trips take place every day - an enormous energy requirement that should be supported by modern storage systems," said Taavi Madiberk, the CEO of Skeleton Technologies. It has developed a graphene material to boost the energy density of the ultracapacitors and is in volume production of the technology.
“Ultracapacitors provide a high power density and amazing durability. With optimized sizing, plug-and-play functionalities, and the best possible efficiency due to SiC based DC/DC converters, recovering energy in braking applications makes a lot of sense,” said Pilar Molina, CEO of Epic Power.
The system is already in use in a number of public, residential, and commercial buildings throughout Europe.