Techno-economic feasibility assessment of a photovoltaic water heating storage system for self-consumption improvement purposes

Abstract

Photovoltaic excess energy export to the grid starts to be a common issue among residential grid-tied PV systems. Its impact is more significant when the feed-in tariffs are not available (Moroccan case) or if they are far from competition. Load shifting, batteries and thermal energy storage all have the potential to diminish the excess energy sent to the grid. However, the water heating strategy has received little literature attention so far. In this study, we seek to assess the techno-economic feasibility of using the PV excess energy in a hot water storage tank by means of a diverter as the main water heating system for a bioclimatic building. The excess energy of a 2kWp grid-tied PV system has been monitored for one year with a 1-min time resolution. The data is used within a TRNSYS numerical simulation for the city of Marrakesh, Morocco. In comparison to an ordinary solar thermal water heating (STWH) system, the results of the simulation revealed that both systems maintain the setpoint temperature using practically the same amount of auxiliary energy. Additionally, a 52.23 % relative improvement to the self-consumption rate has been obtained by integrating a PV water heater (PVWH). The Levelized Cost of Energy found to be 33 % lower for the PVWH compared to that of the STWH solution, evaluated at 0.06 and 0.09 $/kWh respectively. In addition, PVWH's Payback Time period was four years, while that of the STWH was six years. Ultimately, the Net Present Value was significantly higher for the PVWH (1840.28 $) than for the STWH (1008.8 $).