In recent years, CO2 emission have acutely increased all over the world. This is also the case in Japan. A great increase in CO2 emission is claimed to be responsible for the global climate change, which obligated Japan to reduce GHG emission by 6% relative to the figure for 1990. There are many ways of reducing CO2 emission, one of which is energy saving. In Japan, the energy saving has been intensively promoted in the industrial sector, but not in the commercial and residencial sectors, nor in the transportation sector.
Thus in this article we have focused on energy saving in the commercial sector. We have studied as an example environmently-sound construction, so called ``Eco-Office'' (located in the National Institute for Environmetal Studies) which provides detailed data on energy-consumption and climate condition. Based on the data, we have calculated the dynamic heat load and electric power demand using the response factor method. We have also invetigated how we could increase the rates of self-sufficiency in electric power and energy.
First, we have developed the model of estimating dynamic heat load, utilizing the response factor analysis. This is to compare the room temperature calculated accounting for heat extraction from the data with the observed one. We have found that the coefficient of correlation were 0.87 in Febrary and 0.65 in August, and thus that they are not so low.
Using this model, we have examined the effect of energy-saving measures installed in the Eco-Office. We have found that the use of insulation saved 13.8% in electric power and 13.4% in energy. In addition, double glazing was estimated to save 0.7% and 0.7%, all heat exchanger 16.5% and 16.0%, solar thermal panel -3.3% and 4.4%, photovoltanic 20.0% and 19.4%, and the Eco-Office in total (all measures installed) 48.9% and 54.4% in electric power and in energy, respectively.
Next, we have investigated how Eco-Office can fulfill the energy demand by its own PV and solar panel. Now the rate of self-sufficiency in electric power is 29.3% (if electric power is not permitted to be sold, it is 26.7%), the rate in energy is 35.5% (32.9%). In contrast, if the present PV is exchanged with better one with 15% conversion efficiency (it is the best commercially available), the rate of self-sufficiency in electric power would increase to 80.1% (if electric power is not permitted to be sold, it is 49.2%) and the rate in energy would increase to 86.0% (55.2%).
The Eco-Office occupies about only 20% of the total floor of the building. Using all areas of its roof can barely achieve the above figure in self-sufficiency. Thus, at present, to construct a building self-sufficient in energy remains to be difficult. However, there are many options besides the above that can improve energy efficiency: for example, air conditioning optimization, various air conditioning equipment efficiency and so on. Thus, it would not be dreaming to construct a particular building self-sufficient in energy in future.