Bright future: How Hong Kong can harness the potential of solar energy

We must give credit to Elon Musk for bringing up the issue of solar energy in Hong Kong. We should have a solar policy; when so many people here use sunscreens all year round, common sense tells us that there must be plenty of solar energy to harness.

Hong Kong is located favourably in the subtropics, with an annual mean daily solar power of about 4 kilowatt-hours per square metre per day, even after accounting for overcast days during the rainy seasons. For an average village house with a roof area of 70 square metres, that equates to about 280kWh of solar energy irradiation on the rooftop per day.

Yet, we are not using renewable energy from the sun wisely. The sun heats up the roof and we burn fossil fuels to power air conditioners to cool the room below. Even though the efficiency of converting solar energy into electricity is about 10 per cent, in practice, solar panels atop a village house could generate 840kWh of energy a month, worth some HK$1,000.

An electric vehicle typically needs about 25kWh of electricity to fully charge, and has a range of at least 120km. So, a village house rooftop solar system could fully charge an electric vehicle every day, eliminating the need for petrol, and reducing our carbon footprint. Considering that most city cars only cover about 30km a day, a full charge could last four days, or one village house rooftop solar system could meet the demands of three or four electric vehicles per day.

City Hall car park offers another opportunity for installing rooftop systems. Car owners do not want to park on the top floor in summer because of how hot their cars can get. If we put raised solar panels on the top floor, we could harvest the solar energy for charging electric vehicles and reduce the heating of cars parked below the panels. Parking revenue would also increase.

Land is scarce in Hong Kong, but there are plenty of “underutilised” areas. Converting closed landfills into solar farms is becoming increasingly popular around the world. We still have three big operating landfills and, although the prevalent practice here has been to restore landfills to grass and woodland, or sports facilities, two of our landfills are too far away to make them ideal for sports facilities. The total area of the three landfills is about 260 hectares, equivalent to 20 Kowloon Parks, of which most of the restored land is slopes, and thus not suitable for sports facilities. Instead, we should convert this underutilised land into solar farms. The slopes could house over 200 megawatts of solar panels, enough to power 10,000 electric vehicles.

Japan, meanwhile, is building a solar farm on water, covering the Yamakura Dam reservoir (around 18 hectares) with 50,000 solar panels, generating 13.7MW of power when complete. Singapore is considering doing the same. We have two huge reservoirs which could house large floating solar farms. If we look hard enough, we can always find places for solar installations.