NOVELTY - A solar cell unit (A1) comprises hollowed cylindrical shaped or rigid solid rod substrate (102) having first and second end; and several photovoltaic cells (B1) linearly arranged on substrate. The photovoltaic cell comprises first and second photovoltaic cells having back-electrode (104) disposed on substrate; semiconductor junction layer disposed on back-electrode; and transparent conductive layer (110) disposed on semiconductor junction. The transparent conductive layer of first photovoltaic cell is in serial electrical communication with back-electrode of second photovoltaic cell. INDEPENDENT CLAIMS are included for the following: (1) a solar cell assembly comprising several solar cell units (A1) arranged in coplanar rows; or solar cell assembly (A2) comprising several solar cell units (A1) geometrically arranged in a parallel or a near parallel manner for forming a planar array having a first face and a second face; and several internal reflectors, where each respective internal reflector in the internal reflectors is configured between a corresponding first and second solar cell unit in the elongated solar cells such that a portion of the solar light reflected from the respective internal reflector is reflected onto the corresponding first and second elongated solar cell; and (2) a method involving passing a fluid through a substrate, where the substrate is hollowed cylindrical shaped; and several photovoltaic cells (B1) linearly arranged on the substrate.    USE - As solar cell unit useful in solar cell assembly (claimed) for converting solar energy to electrical energy.    ADVANTAGE - The back-electrode supports the photovoltaic current generated by photovoltaic cell with negligible resistive losses. The outer transparent tubular casing layer has excellent UV shielding properties and the inner transparent tubular casing layer has good water proofing characteristics. The use of multiple transparent tubular casing layers reduces costs and/or improves the overall properties of transparent tubular casing. The use of additional transparent tubular casing layers reduces the thickness of the expensive transparent tubular casing layer and thus achieving a savings in material costs. The use of monolithic integrated designs increases the voltage across the length of the solar cell unit. Thus decreasing the current and reducing the current requirement of individual solar cells, as a result there is no need for electrode strips. The monolithic integration strategy has the advantage of minimal area and minimal number of process steps. The highly electrically conductive material allows the vias to have very narrow line width and still be effective. This helps to reduce semiconductor junction area loss.    DESCRIPTION OF DRAWING(S) - The figure shows processing steps for manufacturing the solar cell unit.    substrate (102)    back-electrode (104)    absorber layer (106)    junction partner layer (108)    transparent conductive layer. (110)