Vegetable farmer's bright idea for cheaper electricity

Vegetable farmer burnishes green credentials by using solar power to fuel hydroponic system - and slashes his electricity bill in the process

PUBLISHED : Monday, 05 May, 2014, 5:01am
UPDATED : Monday, 05 May, 2014, 5:29pm

With electricity bills set to rise across Hong Kong, a vegetable farmer has found a way of slashing his energy costs as well as his carbon footprint.

Henry Ngai Hon-shun has long taken pride in hydroponic farming, a method that involves growing plants in nutrient-enriched water that is widely regarded as a more efficient and environmentally friendly method of food production.

But Ngai aims to make the process even greener and cheaper by using solar power to slash his carbon footprint and energy costs by a quarter.

His action comes after warnings from the government that an increase in electricity demand will force prices to rise.

In March, with support from CLP Power's public education fund, Ngai installed a set of concentrated photovoltaic and flexible thin film solar panels, connected to the company's grid, to power his water pumps.

The three concentrated panels and eight flexi-panels will help Ngai's Organic Waste Recycling Centre in Sheung Shui save 3,000 kilowatt-hours of energy per year. At a rate of HK$1 per kWh, that would shave HK$3,000 a year, or 25 per cent, off his HK$12,000 yearly power bill.

"Although water is recycled, powering the water pumps has traditionally been the most carbon-intensive process for hydroponic farms," Ngai said.

"Using solar would help make the whole concept even more environmentally [friendly]."

His 0.27 hectare hydroponics farm grows salad vegetables including romaine lettuce and rocket, which are sold mainly to hotels wanting locally sourced organic vegetables. It is one of Hong Kong's first businesses to install concentrated photovoltaic and flexible thin film solar panels.

The concentrated panels focus sunlight onto fewer and smaller semiconductor photovoltaic cells than a regular solar panel, but can produce the same amount of power.

They have a 25 per cent power conversion efficiency rate but are less effective on overcast days than flexible thin film panels, with a 10 per cent efficiency rate.

Over the course of a year, the overall power conversion of the two types of panels was about the same, CLP marketing and customer services director Chow Lap-man said. He said solar was a good alternative energy source, but not a primary source because it was "at the mercy of the skies".

CLP will measure the panels' efficiency over the next year.

Solar photovoltaic systems in the city generated 2.2 million kWh in 2012 - 0.005 per cent of total electricity generation.