Solar Photovoltaic
Photovoltaic Systems
The function of a photovoltaic system is to generate electricity from sunlight, either in the form of DC or AC, to meet the demand of electrical loads. A photovoltaic system is made up of a photovoltaic array and the balance-of-system equipment such as charge controllers or inverters, electric cables and switchgear, surge arrestors, etc.
Photovoltaic arrays at locations in the northern hemisphere such as Hong Kong are usually installed facing south with a tilt angle near to the latitude of the location, so as to maximize the amount of electricity generated over the course of a year.
Photovoltaic systems in Hong Kong can be classified into two main types - stand-alone systems and grid-connected systems. These can further be divided into ordinary photovoltaic systems and building-integrated photovoltaic (BIPV) systems. For BIPV systems, the photovoltaic modules are integrated into the building envelop as part of the building structure. They replace some of the building components on the roof or on the facade, and produce electricity to meet a portion of the electricity demand of the building.
(a) Standalone photovoltaic systems operate without any interaction with the utility grid. Most standalone photovoltaic systems comprise of solar panels , a charge controller and storage batteries to supply power to DC loads. If the system has to supply power to AC loads, an inverter is needed to convert the DC power into AC power. As sunshine is intermittent in nature, storage batteries are needed to store some of the electricity generated by the solar panels , so that when sunshine is insufficient, the system can still supply power to the loads.
Above: A standalone photovoltaic system supplying DC and AC loads
Standalone photovoltaic systems are usually found in locations where connection to the grid is not convenient or not economical, such as telecommunication equipment or telemetry stations in remote locations. Solar-powered lighting poles are also installed in different locations in Hong Kong. There are also some earlier BIPV systems designed to operate as standalone systems.
(b) Grid-connected (or grid-tied) photovoltaic systems in Hong Kong are connected to grid This link will open in a new windowindirectly. The AC output of the photovoltaic system is connected to the electrical distribution system of a site or a building, and therefore the photovoltaic system operates in parallel with the electricity supply from the grid to meet the electricity consumption of the site or building. In this way, storage batteries are not required. More information is given in the This link will open in a new windowGrid Connection section and This link will open in a new windowSolar photovoltaic - Grid Connection section of this website.
Above: 350 kW system at EMSD Headquarters