Method and apparatus for storing energy

1. An energy storing system, comprising

a plurality of weights ( 12 );

a first storing unit ( 14 ) and a second storing unit ( 16 ), wherein the first storing unit ( 14 ) is arranged below the second storing unit ( 16 ) and each of the storing units ( 14 , 16 ) comprises a guiding track ( 18 , 20 ) on which weights ( 12 ) can be placed and along which weights ( 12 ) can be moved, wherein each of said guiding tracks ( 18 , 20 ) comprises a first portion ( 22 , 26 ) and a second portion ( 24 , 28 ), wherein the second portion ( 24 , 28 ) is arranged below the first portion ( 22 , 26 ); and

a loading unit ( 30 ) configured to lift at least one weight ( 12 ) from the first storing unit ( 14 ) to the second storing unit ( 16 ) during a first period thereby converting electrical energy to potential energy, said loading unit ( 30 ) further configured to lower at least one weight ( 12 ) from the second storing unit ( 16 ) to the first storing unit ( 14 ) during a second period, thereby converting potential energy to electrical energy, wherein the loading unit ( 30 ) is configured to collect a weight ( 12 ) from the second portion ( 24 ) of the first storing unit ( 14 ) and to place said weight on the first portion ( 26 ) of the second storing unit ( 16 ) during the first period and to collect a weight ( 12 ) from the second portion ( 28 ) of the second storing unit ( 16 ) and to place said weight ( 12 ) on the first portion ( 22 ) of the first storing unit ( 14 ) during the second period.

2. The energy storing system according to claim 1 , wherein each weight ( 12 ) comprises means such as wheels ( 13 ) configured to allow said weight to move freely along the guiding track ( 18 , 20 ), on which said weight is placed, from the first portion ( 22 , 26 ) to the second portion ( 24 , 28 ) of said guiding track ( 18 , 20 ).

3. The energy storing system according to claim 1 , wherein the loading unit ( 30 ) comprises a loading stage ( 32 ) having a stage guiding track ( 54 ) configured to co-operate with the respective guiding track ( 18 , 20 ) of any of the storing units ( 14 , 16 ) to facilitate transfer of a weight between the loading stage ( 30 ) and the respective guiding track ( 18 , 20 ).

4. The energy storing system according to claim 1 , comprising a multitude of storing units arranged at different heights.

5. The energy storing system according to claim 1 , wherein the duration of the second period is different from the duration of the first period.

6. A method comprising the following steps

providing a plurality of weights;

providing a first and a second storing unit, wherein the first storing unit is arranged below the second storing unit;

lifting at least one weight from the lower storing unit to the upper storing unit during a first period thereby converting electrical energy to potential energy; and

lowering at least one weight from the upper storing unit to the lower storing unit during a second period, wherein the duration of the second period is different from the duration of the first period, thereby converting potential energy to electrical energy.

7. The method according to claim 6 , wherein the second period is shorter than the first period.

8. The method according to claim 6 , wherein the second period is longer than the first period.

9. The method according to claim 6 , wherein the first period is an off-peak electricity period and the second period is a peak electricity period.