Is the “Solar House” One Solution?
By “Awake!” correspondent in Japan
THE bright-red disk on a white background that serves as the national emblem of Japan is also a silent reminder of the time when the sun was worshiped throughout this land as the goddess Amaterasu Omikami. In recent times, Japanese attention once again has been directed heavenward, but this time in search of a reasonably priced source of energy.
Actually, for many years solar water heaters have dotted the roofs of tens of thousands of Japanese homes. However, it was not until the oil problems of 1973 and accompanying threats of energy rationing that serious attention was given to the use of solar energy on a scale larger than for private homes.
Along these lines, a notable step was taken at Numazu City, Japan, which has a population of more than 203,000 and is located between the foot of Mount Fuji and the sea. Officials and engineers there decided to decrease the city’s consumption of oil and electricity by using energy from the sun. The first practical result was the construction of the new Kanaoka Hall and City Office Annex, appropriately called Taiyo no Ie, that is, “House of the Sun” or “Solar House.” During its first year, this building saved Numazu City $5,000 just by using the sunshine that fell on the roof. Would you like to know more of the details that make this ‘sun house’ a success?
Tapping the Sun’s Energy
It is said that the earth receives 20,000 times as much energy from the sun as humans use. So the potential of this energy source is obvious. The two main hindrances to using solar energy are: (1) it is not continuous (the earth’s rotation and cloud cover causing interruptions), and (2) the low intensity necessitates large collector areas to harness the energy.
The many different systems being considered to harness the sun’s energy range from simple reflector cookers that can boil a liter (about 1 quart) of water in 20 minutes to photovoltaic cells (usually made of silicon) that convert the solar energy directly into electricity. In southern France, a large solar furnace using 3,500 small mirrors focused on a central point produces temperatures as high as 2,980 degrees Celsius (5,396 degrees Fahrenheit). Some scientists advocate placing collectors in orbit and sending the energy (in the form of microwaves) to large receivers on earth. Others feel that the electrical needs of the United States can be met by placing solar energy collectors in a vast area of desert land and then using that energy to produce steam for turning turbines.
Yes, there may be many ways of harnessing the sun’s energy, although much more research needs to be done before most of these methods can be put to use on any large scale. However, the system at “House of the Sun” already is in operation, saving money and resources by using the pollution-free energy of the sun. It has been so successful that Kyohiko Watenabe, assistant head of the Home Building and Repairs Department of the Environmental Bureau in Numazu, feels that within three years similar systems will be required on all new government buildings.
Instead of waiting until a total solar energy system was perfected, Numazu City officials decided to use what already had been developed. The system is simple, but operates at 30 percent efficiency. It collects enough energy each sunny day to heat or cool the two-story building with 716 square meters (7,707 square feet) of floor space, and to provide hot water for washing and for making tea. When it is rainy or cloudy, an auxiliary boiler may have to run one day in three. Nevertheless, getting two thirds of the heating energy from the sun in a country that has to import 98 percent of its oil certainly is a noteworthy step. How does this “House of the Sun” harness the energy of its namesake?
Two hundred and twenty-four collectors are lined up on the roof, all of them lying at a 25-degree angle to catch the direct rays of the sun. Each collector has a glass cover to let the light pass through. Water circulates through small black tubes inside, where it is heated. This heated water flows into a 20-ton storage tank, where the temperature may reach the boiling point. When this stored water gets cooler than the water in the collectors on the roof, a small pump circulates it through radiators inside the building, and fans distribute the heat. Because chemicals are in this water to prevent rust and sludge from forming, it is not drinkable. But a separate five-ton container inside the big storage tank is heated to provide water for washing and the making of tea.
By applying the principles used in a refrigeration unit that is powered by gas, solar energy also cools the building. Therefore, the hotter it gets outside, the more energy becomes available for cooling. Walking into the “Solar House” on a very hot summer day and finding that the inside temperature is 25 degrees Celsius (77 degrees Fahrenheit) is convincing proof that there are practical ways of utilizing solar energy.
“Solar House” in Numazu is a practical example of utilizing an abundant source of energy, one that is especially usable between 35 degrees north and 35 degrees south latitude. Numazu officials were so convinced that they had taken a step in the right direction that a solar heating and cooling system was installed in a new nursing home in the Ashitaka Mountain area of the city.
The floor space of this new home is twice that of “Solar House,” and so its solar energy system’s capacity is more than double that of the “House of the Sun.” Five hundred and twenty-two collectors on the roof provide energy for heating and cooling the home, as well as furnishing hot water for tea and bathing. Because an extra 100 square meters (1,076 square feet) of collector area was provided for possible future expansion, the efficiency of this unit is 37 percent and energy can be stored for later use.
Solution to Future Energy Problems?
Are there any difficulties or disadvantages in using a solar energy system? Yes. Balancing the flow of water through the two-square-meter (22-square-foot) collectors and pipes was the biggest problem. But this was overcome, and the system at the “Solar House” has continued working with relatively little maintenance. Probably the biggest drawback is initial cost, this being much higher than that of conventional gas or oil systems. However, with the savings in energy, the added expense for the system at “Solar House” will be paid for in seven years, or even sooner if the price of oil continues to rise. The nursing home at Ashitaka cost an extra ¥18,500,000 (US$61,667) to build, but it is estimated that this expense will be recovered in 4.2 years of operation. Why is this so? Because energy expenses for heating and cooling are ¥750,000 (US$2,500) a year at Ashitaka, but in a comparable facility also housing 50 persons and using conventional systems, the yearly cost is ¥5,200,000 (US$17,333).
So what impression has the “House of the Sun” made on us? First, it has taught us to look at solar energy realistically. This is not a total energy system. Electricity is required for the lights and office machines, as well as the pumps and fans connected with the solar system. Also, if it rains or is cloudy, the auxiliary boiler must be used. (This is not an independent system, but merely heats the water in the solar energy system.) On the other hand, when the sun is shining, which is about two thirds of the daylight hours, the energy that otherwise would be reflected back into the atmosphere or absorbed by the roof is being put to work through a virtually nonpolluting system.
Secondly, the fact that a city was willing to break away from the normally accepted means of heating and cooling impresses us with the need to evaluate the way the earth’s resources are being used. Many people fear that at the present rate, the fossil fuels will be used up in a relatively short time. However, due to the convenience of burning such fuels, people are slow to adopt new methods that may require adjustments in their energy consumption or a greater initial investment, even though these may have better long-range prospects.
Thirdly, reliance on solar energy helps to build appreciation for simpler things and those that we may have taken for granted. Interestingly, the city engineer who showed us around the “Solar House” said that until these buildings were constructed, he never really had appreciated what it means to have the sun come up every morning. Just think about that for a moment. If the sun were not shining, the temperature everywhere on earth would be minus 240 degrees Celsius (−400 degrees Fahrenheit).
Even without rooftop collectors, solar energy affects our lives in many ways. By means of light from the sun, plants change carbon dioxide from the air and hydrogen from water in the soil into carbohydrates that become our food. Wind is an indirect form of solar energy, for the heating and cooling of land masses and the atmosphere cause the breezes to blow. Every day, heat from the sun evaporates from the earth the vast amount of water that later falls as rain or snow. When that water is collected into rivers and reservoirs, man can tap the sun’s stored energy by means of waterwheels and hydroelectric generating systems.
Every year the earth receives 700 quadrillion kilowatt-hours of energy from the sun. Yet that fantastic amount is but a minute fraction of the sun’s total output because it shines outward in all directions. To what extent man in the future will be able to harness this virtually unlimited supply of energy remains to be seen. But that he can—if he chooses to do so—put solar energy to practical use becomes evident when we consider modern buildings such as the “House of the Sun.”