PLC (Power Line Communication) uses power lines to connect equipments to the network. President Eiji Kobayashi of HD-PLC Alliance, which promotes HD-PLC, a PLC communication method originating in Japan, uses ‘Green Ubiquitous’ as the keyword in making HD-PLC unique (refer to previous interview). In this second part of the interview, he talks about the 'Green Ubiquitous' world, which HD-PLC is aiming for.

•——‘Green Ubiquitous’ is not a very familiar word to many of us. What kind of concept is it built on? Please tell us how it relates to HD-PLC.

Kobayashi: ‘Green Ubiquitous’ aims to realize a world that can connect to the network from anywhere, while curbing the impact on the environment. In this day and age, even if a product can make our life more convenient, it cannot simply go into production if it has a big impact on the environment. I will talk about how HD-PLC can contribute to realizing a ‘Green Ubiquitous’ society in two ways.

One way is by reducing the number of cables used for networks. Ordinarily, to connect equipments to the network, cables are necessary. However, a large amount of CO₂ is emitted in producing those cables. Therefore, by reducing the number of cables, we can reduce the amount of CO₂ emissions, which is a big factor in protecting the environment. Since HD-PLC uses pre-existing power lines, new cables are unnecessary; there is a possibility that cable production and additional CO₂ emissions can be suppressed. This is the first way.

To take a real example, when fifteen PLC adaptors were set up in a LAN on a school campus which used to be connected by just using cables, the total length of cables used were down to 300 meters from 900 meters. To produce 600 meters of cables, the reduced amount, 27.6kg of CO₂ is emitted. This amounts to 2760 soccer balls worth of CO₂ in volume.

• An example of when an on campus LAN is switched from cables to PLC. By using PLC, total length of cables were down to 300 meters from 900 meters; cables were reduced by 600 meters. CO₂ emitted during production of the cables amounts to 2760 soccer balls worth

Small Difference makes a Big Impact

•——We see that CO₂ emissions reduced by not using new cables are not small. But can't wireless LAN be another option, in that it doesn't use any cables?

Kobayashi: That leads me to my second point. One advantage of HD-PLC is the low amount of electricity it uses. When wireless LAN is idle, it uses 4 watts per hour; the newest models use 7 to 14 watts. However, the new PLC adaptors will only use 3 watts per hour, down to 1 watt when idle.

The difference in electricity used may be small, but in a ubiquitous society, all kinds of equipment are connected to the network. This means that the electricity used in the whole society, when totaled will make a big difference. Realizing a ubiquitous society only using a small amount of electricity, meaning only small amounts of CO₂ is emitted, is the second way HD-PLC can help realize a ‘Green Ubiquitous’ society.