Funding for this research was provided by:
Rural Development Administration (PJ01337602)
Korea Institute of Energy Technology Evaluation and Planning (20173010092460)
Received: 2 April 2020
Revised: 8 June 2020
Accepted: 15 June 2020
First Online: 22 June 2020
Compliance with ethical standards
: The authors declare that they have no conflict of interest.
: This article does not contain any studies with human participants or animals.