A modular energy harvesting device comprising: a light-to-electricity converter module including: a light-to-electricity converting device for receiving sunlight and converting the sunlight to electricity, said light-to-electricity converting device defining a light-to-electricity converting device plane; and a first connection portion comprising a first electrical connector being electrically connected to said light-to-electricity converting device to allow flow of electrical current from said light-to-electricity converting device via the first electrical connector; and an elongated cylindrical energy storage module having a longitudinal axis, said energy storage module including: an energy storage device for storing electrical energy; and a second connection portion for releasable mechanical and electrical connection to the first connection portion of said light-to-electricity converter module, said second connection portion comprising a second electrical connector being electrically connected to said energy storage device to allow flow of electrical current from the light-to-electricity converting device of said light-to-electricity converter module to said energy storage device by means of electrical connection formed between the first electrical connector of said light-to-electricity converter module and the second electrical connector of said energy storage module, wherein the first connection portion of said light-to-electricity converter module and the second connection portion of said energy storage module are configured in such a way that the longitudinal axis of said energy storage module is perpendicular to the light-to-electricity converting device plane of said light-to-electricity converter module when said energy storage module is attached to said light-to-electricity converter module. a light-to-electricity converter module including: a light-to-electricity converting device for receiving sunlight and converting the sunlight to electricity, said light-to-electricity converting device defining a light-to-electricity converting device plane; and a first connection portion comprising a first electrical connector being electrically connected to said light-to-electricity converting device to allow flow of electrical current from said light-to-electricity converting device via the first electrical connector; and a light-to-electricity converting device for receiving sunlight and converting the sunlight to electricity, said light-to-electricity converting device defining a light-to-electricity converting device plane; and a first connection portion comprising a first electrical connector being electrically connected to said light-to-electricity converting device to allow flow of electrical current from said light-to-electricity converting device via the first electrical connector; and an elongated cylindrical energy storage module having a longitudinal axis, said energy storage module including: an energy storage device for storing electrical energy; and a second connection portion for releasable mechanical and electrical connection to the first connection portion of said light-to-electricity converter module, said second connection portion comprising a second electrical connector being electrically connected to said energy storage device to allow flow of electrical current from the light-to-electricity converting device of said light-to-electricity converter module to said energy storage device by means of electrical connection formed between the first electrical connector of said light-to-electricity converter module and the second electrical connector of said energy storage module, an energy storage device for storing electrical energy; and a second connection portion for releasable mechanical and electrical connection to the first connection portion of said light-to-electricity converter module, said second connection portion comprising a second electrical connector being electrically connected to said energy storage device to allow flow of electrical current from the light-to-electricity converting device of said light-to-electricity converter module to said energy storage device by means of electrical connection formed between the first electrical connector of said light-to-electricity converter module and the second electrical connector of said energy storage module, wherein the first connection portion of said light-to-electricity converter module and the second connection portion of said energy storage module are configured in such a way that the longitudinal axis of said energy storage module is perpendicular to the light-to-electricity converting device plane of said light-to-electricity converter module when said energy storage module is attached to said light-to-electricity converter module.