Energy conservation isn’t just for summers any more
Last summer when the antinuclear movement was receiving a lot of media coverage, the government and utilities justified their plans for reopening nuclear power plants with statistics purportedly showing how dangerously close to capacity electricity usage is in the summer, when everyone has their air conditioners on. Thanks to energy conservation efforts on everyone’s part there were no overloads, but in terms of households, reibo (cooling) only accounts for 2 percent of overall energy usage when measured in calories. Danbo (heating), on the other hand, accounts for 25 percent of home-energy usage.
Of course, there are various methods for heating homes in Japan. In addition to electricity, there is natural gas, liquid propane gas and kerosene (toyu), but electricity has been increasing in recent decades as a means for home-heating. Between 1980 and 2005, the use of kerosene, which is utilized in space-heating “stoves,” declined from 71 to 45 percent in terms of heating needs in the Kanto area, while both natural gas and LPG increased from 21 to 35 percent and electricity from 8 to 20 percent. However, when you factor in all of a home’s energy needs — cooking, lighting, bathing, etc. — electricity accounts for 50 percent, kerosene 17 percent, natural gas 20 percent and LPG 10 percent of household energy consumption. That was for all homes in Japan in 2009. In 1973, electricity only accounted for 28 percent of overall household energy usage. So with the promotion of all-electric houses in recent years, the overall portion of home heating by electricity has probably gone up even more.
The peak period for electricity usage in the wintertime is between 5 and 6 p.m., and during the current sharp cold spell, electricity usage as reported by Tokyo Electric Power has been over 90 percent during the peak time slot. The main difference between wintertime and summertime is that power plants reduce capacity in the winter, so 90 percent represents less power usage in the winter than it does in the summer. Most air conditioners run on electricity, but as shown above heating systems use a variety of methods, so electrical usage is deemed to be less. But since electricity usage in the winter is on the increase, why aren’t power companies warning people to cut back when the usage gets close to the limit, as they did last summer?
Maybe it’s because the human body is less tolerant of extreme cold than it is of extreme heat. However much cooling technologies have benefited civilization and human health, air conditioning for the most part is a luxury. Heating isn’t, and as electricity becomes the most common form of home heating consumers will need to know more about how to conserve it.
Last November the Chunichi Shimbun published an article on how to properly use heat-pump-style air conditioners for heating. According to an expert interviewed in the article, this style of heating is becoming much more common in Japan but most people use their air conditioners improperly for heating. Most units are placed close to the ceiling in a room, which is fine when they are being used to cool, but since heat rises they have be adjusted carefully when used to heat.
Many people make the mistake of setting the louver that directs air flow toward the bodies in the room and then cranking up the thermostat until the air feels warm against their skin. However, when “wind” blows directly on a person the air feels cooler than it actually is. The point is to warm the entire room in a uniform manner, and to do that you don’t need to set the thermostat high. All you need is proper air circulation, so the expert recommends putting an electric circulator on the floor to distribute warm air more evenly throughout the room.
Space heaters are also less efficient in this regard, since, as the name suggests, they only warm the air immediately surrounding the unit. When using a space heater, whether electric or kerosene, it’s a good idea to have a ceiling fan set to “winter” mode, which directs the flow of air downward. But the expert insists that, in terms of overall energy conservation, heat pump air conditioners are superior since, unlike conventional heaters, they don’t directly change the power supply into heat. What they do is extract the ambient heat from the air outside the house and transfer it to the interior of a house. When used properly, a heat pump costs about ¥6.4 per 1,000 kilocalories of heat transferred, while a kerosene stove costs about ¥10.5 per kcal created.
Beware, however, of using heat pumps in very cold places, such as Hokkaido. When the outside temperature drops below 7 degrees celsium, the heating efficiency also drops because there is much less ambient heat to extract from the outside air, and when it gets to the freezing level the outside heat-exchange unit doesn’t work very well. In such areas it’s best to use a combination of heat pump and kerosene/gas.