A Japanese research team has evaluated the affordability of photovoltaic battery systems with heat warmers and air conditioning units in nine regions of Japan. They analyzed three pricing policy and two loan types and identified a trade-off between the net question and the costs according to the capacity of the solar-plus storage system.
Researchers from the Japanese National Institute of Advanced Industrial Science and Technology have carried out an economic analysis on the use of a photovoltaic battery (PV -BT) system with heat pomp poners (HPWHS) and air conditioning (AC) units installed in Japan.
The system was analyzed in nine regions of Japan – Kansai, Kyushu, Shikoku, Chubu, Chugoku, Tokyo, Tohoku, Hokuriku and Hokkaido – against different price policy and lenses.
The results are presented in the research paper “Economic analysis of a photovoltaic battery system for an electrified detached house with a heat pump boiler: effect of time variable electricity prices‘Published in the magazine Energy.
The research paper says that the affordability of PV-BT systems has not been evaluated in detail before, especially when it has been admitted with HPWH and AC units. The researchers investigated the affordability of PV-BT systems based on a 20-year operating period. The electricity costs and the demand of peak power were determined on the basis of the net question, and an economic analysis was carried out by considering the electricity costs and PV-BT system prices for a year of one year.
The analysis was based on real data from smart meters that collect power consumption and usage time. A total of 5,751 data points of one year measured between 2017 and 2023 were collected from the households. In the nine regions it was assumed that households have a PV system of 10 kW and a battery of 10 kWh. The results were compared with a reference case without a PV-BT system. In addition, various PV values ranging from 5 kW to 10 kW and various BT values ranging from 0 kWh to 12 kWh.
All houses were analyzed under three price regimes: usage time (tou), real -time price (RTP) and Progressive Rate (PR). Japanese electrical energy companies have changed tou regimes per region, consisting of two or three price periods per day. In the RTP system, electricity is sold to consumers based on transmission costs and service costs based on the Japan Electric Power Exchange trade price, which changes every 30 minutes. The prices of the PR system also vary per region, with the lowest rate that is available for monthly use of less than 120 kWh, an average speed for using 120 kWh to 300 kWh and a high percentage for the use of more than 300 kWh.
Image: National Institute of Advanced Industrial Science and Technology, Energy, CC by 4.0
The analysis considered two types of loans. Loan A was aimed at new construction, with an interest rate of 1% per year and a repayment period of 30 years, while loan B was aimed at retrofit activities and consisted of an annual interest rate of 4% and a reimbursement period of 20 years.
The study also considered both current and future objectives. The basic and objectives for the installation of a PV system on the roof were estimated at JPY 255,000 ($ 1,731)/KW and JPY 150,000/kWh, while for the installation of a battery was estimated at JPY 134,000/kWh and JPY 70,000/kWh. Maintenance costs were adopted on JPY 35,000 per four years, and the Feed-in-Tariff (Fit) was JPY 16/kWh for the first 10 years and JPY 7/kWh for the following 10 years.
The researchers discovered that electrified houses based on HPWH and Zonne-Plus storage systems only reach affordability under certain circumstances defined by the loan, fit, repayment costs and maintenance costs.
“Higher PV and battery capacities improved the self-supply of the electrified household, but increased the total costs due to the interest in connection with the reimbursement of the PV-BT system loan,” the researchers said. “Moreover, the peak demand was reduced by moving the HPWH and AC operations to correlate with PV generation.”
The researchers said these findings suggest that installing a PV-BT system can reduce the net requirements of households, and added that low PV-BT system installation costs and low interest rates make the PV-BT system affordable for reimbursement.
The research paper concludes that the high installation costs in connection with PV-BT systems are a barrier for many households.
“That is why the total demand for electrified houses must be investigated in the context of the electricity company to promote CO2 neutrality, because the current findings raise new questions about the overall demand profiles achieved by shifting the HPWH and AC requirements,” adds the paper.
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