This paper investigated and proposed a new running-cost subsidy system utilizing the environmental value of solar thermal in order to promote expansion of solar thermal use. The program is not a conventional subsidy program for the initial cost but a new program of providing a subsidy for running a system while confirming user status. It is for the national or local government to provide incentives in accordance with the environmental value based on the amount of solar thermal use. The similar scheme to the proposed system, there is Green Thermal Certificate system in Japan, Australia REC system and UK RHI system, and we discussed the common points and differences between the proposed system and these similar systems. Feature of the proposed system is, by the conversion factor that defines for each measurement method is to convert the amount of solar thermal use to the environmental value amount, and the user can select how to measure. It was verified as NEDO research project for the accuracy of the measurement method. This project has adopted specified measuring instruments as reference and conducted experimental study using actual or artificial loads at residential houses and condominiums in a total of 101 fields across the country. The study set out the target values of error within ±10% for built-in simple calorimeters and external simple calorimeters and less than ±20% for deeming measurement. The study has confirmed that both built-in and external simple calorimeters give high precision in measurement: the average errors of the annual solar heat consumption volumes stood at -1.0% and +2.6%, respectively. As for deeming measurement, the annual solar heat consumption volume has been calculated with the EESLISM simulation program. The calculation has used as parameters HASP meteorological data in the regions with apparatus installed, characteristic values of equipment, expected hot water supply loads and other elements. As a result, the average error of the annual solar heat consumption volumes was -12.2%, which has also satisfied the targeted error range. The subsidy per MJ for the standard cost scenario of a domestic solar hot water system (modified 3.0 to 3.5 people household, solar collector area: 4m2, and hot water tank: 200L) is 5.50 yen. It is based on the national average amount of solar thermal use of simulation calculation (5,647MJ/annual) under the condition of hot water demand M2 (400L/daily hot water supply) at 20 sample places in Japan. The amount of subsidy by measurement method is approx. 310,000 yen, 280,000 yen, 260,000 yen and 220,000 yen when it is measured with a specified measuring instrument, external simple calorimeter, built-in simple calorimeter and deeming measurement, respectively. The subsidy per MJ under a similar UK RHI system is 6.35 yen and its amount is approx. 400,000 yen (four-people household, 4m2 of solar collector area, and 250L of hot water tank) and thus the proposed system is not difficult even slight difference in the estimation conditions is taken into consideration. The basic national energy plan has a goal of requiring new houses and buildings to comply with energy-efficiency standards in stages. Solar thermal utilization is essential to realize the government goal and the program will contribute to its realization as one of measures.
ASJC Scopus subject areas
- Environmental Engineering