  Converting renewable energy into ammonia has been recognized as a promising
way to realize ``green hydrogen substitution" in the chemical industry.
However, renewable power to ammonia (RePtA) requires an essential investment in
facilities to provide a buffer against the strong volatility of renewable
energy and the limited flexibility of ammonia synthesis, which involves the
three main stakeholders, namely, power, hydrogen, and ammonia. Therefore, the
sizing and pricing of RePtA play a core role in balancing the interest demands
of investors. This paper proposes an optimal sizing and pricing method for
RePtA system planning. First, power to ammonia (P2A) is modeled as a flexible
load, especially considering the limited flexibility of ammonia synthesis,
which has been verified using real dynamic regulation data. Second, the
multi-investor economic (MIE) model is established considering both external
and internal trading modes. Then, a two-stage decomposed sizing and pricing
method is proposed to solve the problem caused by the strong coupling of
planning, operation, and trading, and information gap decision theory (IGDT)
method is utilized to handle the uncertainty of renewable generation. Finally,
real data from a real-life system in Inner Mongolia are utilized to verify the
proposed approach. The results show that the system proposed has a yield of
8.15%.
