STUDY ON ZERO ENERGY HOUSE (PART 1): EVALUATION OF LIFE-CYCLE COST FOR ALL-ELECTRIFIED DETACHED ZEH

Abstract

INTRODUCTION

Zero energy house (ZEH) is expected to have a significant initial cost increase compared to conventional houses. In this study, the purpose is to examine the life-cycle cost and economy of ZEH. Calculate the construction costs for ZEH, initial costs such as photovoltaic power generation, the power purchase fee from the electric power company, and the power sales fee for surplus power generation. Similarly, the running cost and initial cost for the conventional house are calculated. By clarifying the life-cycle cost that combines the running cost and the initial cost of the ZEH model and the conventional model. The increase of the initial cost and the reduction of the running cost by the energy saving effect by ZEH are examined.

 

RESEARCH METHODS

The analysis model is a standard housing model of the Architectural Institute of Japan. The model is all electrified houses. The analysis area is 11 major cities. The average U-value is 0.6 W / (m² · K) for the ZEH model (0.4 W / (m² · K) in Sapporo), the conventional model is 1.2 W / (m² · K) (0.8 W / (m² · K) in Sapporo). The annual air conditioning load calculation uses the thermal load simulation software TRNSYS ver.15 to calculate the heating / cooling load of each room for the ZEH and the conventional model in each region. Using the solar radiation from the AMeDAS meteorological data from the Architectural Institute of Japan (standard year), calculate the power generation amount per solar cell in each region. The conventional model uses the annual electricity bill as the running cost.

In the ZEH model, the annual running cost is the amount obtained by subtracting the annual electricity sales fee of solar power generation from the annual electricity purchase fee.In the ZEH model, the solar cell module, power conditioner, and installation work cost are required for initial cost and equipment replacement. In addition, 70 [10,000 yen / unit] is subtracted from the initial cost as a subsidy for ZEH. The service life of the solar power generation system is assumed to be 20 years, and once every 20 years, equipment replacement costs are recorded as running costs. The running cost is added to the initial cost, the life-cycle cost from the time of construction is calculated for each house. The number of years in which the life-cycle cost of the conventional model exceeds the life-cycle cost of the ZEH model is the ZEH investment payback period.

 

RESULTS

The annual power consumption is reduced by about 6% to 26% when the UA value is halved.Investment payback period of ZEH exceeds 25 years in 8 cities except Kobe, Kochi and Fukuoka in case A (hot water supply: COP2, air conditioning: intermittent use). Case C (air conditioning: continuous use) tends to have a shorter investment payback period compared to case A without Kobe, Kochi and Fukuoka. One of the factors is that the benefits of preventive diseases (non-energy benefits) were obtained by using continuous air conditioning. In case D (hot water supply: COP3, air conditioning: continuous use), the investment payback period is the shortest in the analysis case in any region. In Kobe, Kochi and Fukuoka, the payback period is about 10 years. In case D, the maximum investment payback period is about 27 years.