My work focuses on making buildings sustainable...
Cities / How can we make zero-carbon high-rise a reality?
As urbanisation around the world drives demand for high-rise buildings, I think making those buildings zero-carbon is one of the biggest challenges facing engineers.
Even if you use known passive and active design strategies to reduce energy use in a building, you still need quite a lot of energy to ensure occupants are comfortable. The building can generate its own renewable energy, of course, but the energy from renewables such as solar PV is directly proportional to the surface area of a building. The extra surface area of a high-rise building isn’t enough to offset the extra energy demand of each additional floor.
So if we want zero-carbon high-rise buildings, we need to make renewable energy generation more efficient and reduce energy use. I don’t think this can come from better building design alone. Energy management, energy audits, measurement and verification are also needed to ensure building operations are efficient.
For example, I think we need to use more passive design in buildings, and install more task lighting to supplement natural lighting. We could also adopt less formal dress codes at work so that buildings don’t need to be kept at the same temperature all year round. And encouraging a diet that’s lower in meat would make a difference too.
Reducing energy use also relies on behaviour change. Younger generations in Asia seem to be more eco-conscious than their elders, as authors Mark Clifford and Janet Pau argue in their book Through the Eyes of Tiger Cubs, and I’m confident that their forward-looking approach will help reduce energy use.
However, I think efforts to achieve zero-carbon should go beyond individual buildings and extend to improving the overall efficiency of a community by integrating district energy systems. A micro energy grid enables systems to work together across different buildings, producing economies of scale. If you centralise energy conservation systems, you can make them as much as 20-25% more efficient, applying better technology at bigger scales. We’ve seen savings like this on the Korea Micro Energy Grid (KMEG) project in China.
District energy systems can provide power, heating and cooling for all. As well as improving efficiency, you can also manage maintenance more effectively by having a single entity responsible for it. And as individual buildings don’t have to accommodate their own equipment, they can use the valuable floor space for other things.
In Hong Kong, two developments that will use district cooling are underway: West Kowloon Cultural District Development and Kai Tak. The Kai Tak system is due to be completed in 2021 and is expected to save around 85 million kWh of electricity annually. That’s equivalent to cutting about HK$76.5m off the electricity bill and reducing carbon dioxide emissions by 59,500 tonnes.
I think these district energy systems with micro grid schemes point the way to a zero-carbon high-rise future.