My invention aims to produce biodiesei from micro-algae at low cost to replace the hydrocarbon fuels. Aim is to modify the design of conventional photo-bioreactor to increase its capacity for algae growth and Increase the yield at minimal cost. By changing the design of photo-bioreactor making it in form of long triangular structure with rectangular boxes present at each side of the triangle has provided more space for the cultivation of algae at minimal cost. There will be three photo-bioreactors one above the other with slanting side present at a varying angle of 30-60 depending upon the sunlight failing on the area. All the three photo-bioreactors will be connected via pumps and pipes to ensure continuous flow of algae water. Placing long reflectors long the side of photo-bioreactor to reflect sunlight onto them has helped to increase yield. Also the presence of solar panels on each side of photo-bioreactor provides sufficient energy required to run the machinery. The reuse of byproducts during the products has reduced the overall cost. Thus finally we are able to increase the yield of biodiesei from algae and reduce its cost.