A novel greenhouse roof using nano-fluids for light filtering and heat absorption

A new type of greenhouse roof that uses nanofluids for light filtering and heat absorption has been designed. The nanofluids have high absorption rate of long-wave thermal radiation and high transmittance of visible light. In order to control light and absorb heat, new structures made of transparent materials were designed. The structure was optimized by optical simulation. The results show that the absorption rate of vertical incident light is the highest when the cross section of hollow part is double rectangular. In this condition, the sunlight acceptance rate of the nanofluid can reach more than 70%. When the incidence angle increases to more than 25°, the light receiving rate of the nanofluid drops to about 40%. According to the simulation results, the experimental sample was made and the test system was set up to carry out the test under actual weather conditions. The test showed that the light transmittance of the new greenhouse structure at noon was as low as 42.61%. Compared with the double glazing, the temperature in the test box decreased by 5.5 °C. The maximum heat gain of novel greenhouse roof was 192.6 W/m2. This kind of greenhouse roof can not only reduce its visible light transmittance at noon, but also ensure the inner lighting in the morning and afternoon. It can greatly reduce the infrared heat radiation entering the greenhouse.