Exhaustion of Fossil Fuel
As mentioned earlier in the discussion of "oil", it is expected that fossil fuels, including petroleum, will be in short supply in the next century. Some might think that we will be short of energy, but that is not the case. To be accurate, there will be plenty of energy around, despite the possible shortage of convenient-to-use energy resources.
Great Solar Energy
Much of the warmth of the earth's surface comes from the sun. It is said that all the energy consumed by humankind in one year (equivalent to about 8 billion tons of crude oil) is equal to the energy of only one hour's radiation from the sun. In other words, what humankind is utilizing as energy resources is only a tiny fraction (1/17,500) of all the energy the sun puts out. This means that we are far from being deprived of energy. On the contrary, we have much more energy than we can use, and now we are starting to worry about "global warming" as a small amount of energy is beginning to remain on the earth instead of being released into space. Wind power generation and wave activated power generation also utilize solar energy under certain weather conditions. As for oil and coal, they are something like stored-up solar energy created by the photosynthesis activities of organisms that date back a few hundred million years. So, it would be only natural for you to think: "The next generation could use sunlight as an alternative energy!" In reality, the most popular system for residential use that generates energy from natural resources is solar water heating systems that can be installed on roofs. By now, approximately 4.6 million systems have been installed in Japan. This type of system, which is capable only of heating water, is an excellent performer as it can utilize more than 30% of available solar energy.
Recommendation for Photovoltaic Power Generation
Let's consider photovoltaic power generation in this issue. In Japan, we receive approximately 1kW of solar energy per square meter. If 1,500 daylight hours are allowed, approximately 4,500kWh of electricity, which is sufficient for average household consumption for a year, can be generated by photovoltaic modules of about 30 square meters and with a conversion efficiency of about 10%. In Ecological Units, this is 5.3 eu per day and is far more than sufficient.
Those who are engaged in electric power businesses often say that energy generated from natural resources cannot replace petroleum as an alternative energy because they have low density and are unstable. For example, a photovoltaic power generation system cannot create power at night or sufficient power on a cloudy day. Not only that, it may take a few decades before such systems start to pay off economically. Therefore, it is probably best to position such systems as a means to assist conventional systems rather than expecting quick replacement.
Today, the most important issue among electric power companies in Japan is peak load. In recent years, due to widespread use of air conditioning systems, electric energy consumption tends to peak during daytime from July to September. Electric power companies are forced to enhance their facilities to meet this peak demand, while electric energy created at nighttime, including that at nuclear power plants, becomes excess because such plants cannot change their operational output between day and night. Electric power companies are working hard to meet the peak demand by storing unused energy with the use of ice storage air conditioning technology called "Eco Ice" and pumping-up hydraulic power generation systems. These systems can help stagger the peak time but generate energy consistently.
In contrast, photovoltaic power generation system creates the greatest possible energy when it is most required and keeps quiet at nighttime when there is no need to create energy. The system does not emit carbon dioxide, sulfur dioxides, nor nitrous oxides. In addition, its maintenance can be left to each household. It would only be beneficial if electric power companies endeavored more earnestly to promote such a wonderful system with all its advantages. The photovoltaic system could replace conventional systems that are currently in the dominant position if, by some chance, photovoltaic modules with outstanding performance were successfully developed. It is therefore recommended that initially, we give the system a minor role while anticipating its potential.
Written by Shinji Yagi
Reference and Notes
Basic figures are based on data released by the New Energy Foundation.
30 square meters:
Currently popular photovoltaic modules can generate approximately 3kW. The cost for installing such modules for a space of 30 square meters is approximately 3 million yen, which can be reduced to a little more than 2 million yen if subsidy is granted. An association established by private owners of such modules complains in its homepage (http://www.globe.or.jp/fanta/forum/sun/index/html) that people buy cars rather than photovoltaic modules, referring to its cost calculations. This homepage is enjoyable. Reports are posted by its members who introduce themselves as power stations. In the meantime, housing construction companies, including Misawa Home, are trying to reduce the costs for installing photovoltaic modules by introducing roof construction materials that combine photovoltaic modules and position such housing as housing that is self-sufficient in electricity consumption.
".....efficiency of about 10%.....":
This figure is expected to improve in the future due to technological innovations. If the use of photovoltaic modules becomes more widespread, it is inevitable that not only resource issues but also waste problems would arise in the long term. Thus, it is important to choose materials that are environmentally friendly.
".....cannot replace petroleum as an alternative energy.....":
"Ecotopia", a work of fiction written by E. Callenbach, is well known among environmentalists as it concerns an environmental utopia that emerges on the West Coast in the U.S. In this book, a young heroine happens to find (conveniently) a highly efficient material for photovoltaic modules. It is certain that there are idealistic and fundamentalistic aspects to the decision to entrust our future to photovoltaic power generation and much of the criticism directed toward alternative energy is, in fact, focused on these aspects. It is about time for us to change our way of thinking and adjust to the life style which is only viable with the amount of energy that is currently available, rather than looking for alternative energy on the assumption that we will continue to use electricity as we like.
Peak Load:
Eco Ice is an ice storage air conditioning technology that creates ice at nighttime so that buildings can be cooled during the daytime. Pumping-up hydraulic power generation creates energy by utilizing two adjoining ponds (e.g. artificial lakes) with different water levels that are connected by pipes. The system is operated by the fall of water from one pond to the other to create energy during the daytime, while it is operated by pumping up water from the lower pond to the higher pond during the nighttime. Together, the two work as a storage battery and are largely dependent on the nighttime electricity rates set by electric power companies themselves, which are 80 to 90% less than daytime rates.
"........electric power companies endeavor to promote more......":
It appears that they are all seeking to obtain subsidies for photovoltaic systems, including Tokyo Electric Power Co., Inc., which is working together with the environmental NGO, Citizen Forum 2000, for that purpose.
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