Renewable energy becomes more and more important in our daily life. On one hand, it can help fulfill the high demand of energy use; on the other hand, it can reduce global warming and greenhouse effect.

Generally, renewable energy is collected from sunlight, wind, rain, tides, waves, and geothermal heat. These types of power can be used in electricity generation, air and water heating/cooling, transportation, and rural energy services.

Recently, scientists design a new building roof that can use solar-wind-rain power to generate energy. The finding is published in Energy and Buildings.

This eco-roof system uses 5 green technologies: wind turbine, solar photovoltaic (PV), rainwater harvesting and utilization, natural ventilation, and roof sky lighting.

The wind turbines are vertical axis wind turbines. Their orientation of the rotating axis is parallel to the ridge of the roof. The turbines are connected to the electricity generators on the V-shape roof. The energy produced by wind is stored in batteries for the building usage.

The solar PV panels are mounted on the upper V-shape roof and gable roof to collect daylight for electricity generation. There are in total 108 PV panels on both roof sides. The electricity produced by the solar PV is stored in batteries for the building usage.

Part of the roof is transparent to allow the daylight rays into the building to increase the level of illumination. Therefore, it can reduce the energy use for lighting during the daytime. The location of transparent part is arranged to prevent the strong sunlight shining directly into the building.

Rainwater harvester system has two water storage tanks. The rainwater is collected from the upper V-shape roof. One tank of water is used to clean the solar PV panels and cool down the roof. The other tank of water is used for household usage, such as gardening and car washing.

Air vents are located along the ridge of the roof and below the wind turbines. When wind passes through, it speeds up at the ridge and creates a low-pressure region. This can help the warm air inside ventilated out and improve air quality of the building.

Researchers assess the eco-roof system and find that it can generate energy 21205 kWh, save energy 1839 kWh, and reduce CO 2 emission 17767kg per year.

As for the financial return, the total cost of the solar-wind-rain eco-roof system is about $51,973 in 20 years, and the expected revenue of the system is about $123,681 in 20 years. The net present value (NPV) of the energy system over a 20-year period is $71,708. The financial return is very attractive.

Citation: Chong WT. et al. (2016). Performance assessment of a hybrid solar-wind-rain eco-roof system for buildings. Energy and Buildings, 127: 1028-1042. doi: http://dx.doi.org/10.1016/j.enbuild.2016.06.065

Figure legend: This Knowridge.com image is credited to U.S. Department of Energy.