Renewable energy is natural energy which does not have a limited supply. Renewable energy can be used again and again, and will never run out. Examples of renewable energy sources include biomass, hydro energy, geothermal energy, solar energy, tidal energy, wave energy and wind energy.
In the ZCB, renewable energy is generated on site from solar energy by photovoltaic (PV) panels and from biofuel (one kind of biomass) made of waste cooking oil.
A photovoltaic (PV) panel is a device to generate electricity from sun light.
Solar irradiance of the whole ZCB site with reference to surrounding context and neighboring buildings has been studied to determine the best location for the building to collect the solar energy. Three different types of PV panels are used: multi-crystalline on the inclined roof, BIPV-thin film covering the viewing platform, and cylindrical CIGS thin film integrated in the air-tree.
The ZCB's cylindrical CIGS, as the first installation in Hong Kong, are particularly interesting because they are relatively efficient and capture both light reflected from the ground and light directly from the sun.
Solar thermal energy is also utilized in the Eco-café to generate hot water.
The total of 1,015m2 photovoltaic cells can generate 87MWh electricity per year.
Biofuel is a type of fuel derived from organic matter (obtained directly from plants, or indirectly from agricultural, commercial, domestic, and/or industrial wastes) instead of from fossil products.
The ZCB uses a Combined Cooling, Heating and Power (CCHP) system, also called Tri-generation system, to generate electricity from biofuel made of waste cooking oil. The waste heat from the electricity generation process is harvested for cooling and dehumidification. This system is renewable, as the bio-fuel used is produced in Hong Kong from used cooking oil, turning waste to energy. It increases energy utilization to 75%, as compared to 40% in a conventional power plant.
Generating over 143MWh electricity per year, this system together with the PV panels delivers more energy than needed to power the building.