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A group of researchers has proposed a new method for sizing photovoltaic systems that do not rely on an anti-dump system and operate without the possibility of injecting energy into the grid. The novel approach requires an estimation of the annual hourly profile and the minimum power demand, as well as the use of an irradiance meter and an electrical network analyzer.
Researchers at the Instituto Especializado de Estudios Superiores Loyola (IEESL) in the Dominican Republic have outlined a new methodology for sizing rooftop photovoltaic systems in markets without net metering or feed-in tariffs, where all energy produced by the solar array must be self-consumed.
In the study « Sizing of photovoltaic systems for self-consumption without surpluses through on-site measurements: Case study of the Dominican Republic », published in Renewable Energy , the team of researchers explains that their novel approach is designed for small-scale photovoltaic systems for 100% self-consumption without an anti-dump system . In these systems, production cannot exceed the electricity demand of a household, since no mechanism prevents injection into the electrical grid.
These systems require an estimation of the annual hourly profile and the minimum power demand, as well as the use of an irradiance meter and an electrical network analyser. “The relevance of the proposed methodology lies mainly in the fact that the capital cost of the photovoltaic system without an anti-dumping system is lower compared to a system with an anti-dumping system and to conventional net metering systems,” the researchers explain.
Specifically, they used a Fluke IRR1-SOL solar irradiance meter to measure irradiance and temperature and the Fluke 1378 network analyzer, which is commonly used for industrial demands where current is in the tens to hundreds of amps. Modeling is done in an Excel spreadsheet on the monthly energy generated by the PV system over 25 years, taking into account the efficiency losses of the PV modules.
«In the photovoltaic self-consumption analysis step, the energy generated, the CO2 emissions avoided, the energy demand from the electricity grid, the self-consumption rate and self-sufficiency are calculated,» the academics emphasize. «In addition, in the last step, an analysis of the economic viability of the installation is carried out, using the net present value (NPV) method, the rate of return on investment (IRR) and the payback time (TPA) as indicators for the case study.»
The team tested the approach using a case study in the southern province of San Cristóbal. Their analysis considered a household of two adults and three children and the deployment of a 1 kW photovoltaic system at a tilt angle of 20 degrees, estimating annual energy production at 1,578.5 kWh using the PVwatts calculator.
Since the proposed method is about identifying the highest alternating current power that a photovoltaic panel can produce and involves irradiance measurements on a given day, the academics proposed a correction factor to estimate the maximum output power during the year. “In this case, the correction factor was 1.044, resulting in the maximum output power in the year being 131.5 W out of 150 W,” they specified.
They also found that the 1 kW system without antidumping was profitable, with a BPT of 4.57 years, an IRR of 23.4% and an estimated self-sufficiency rate (TAS) of 5.0%. “The deployment of this type of self-consumption is not viable for customers with consumption below 252 kWh/month,” they warned, noting that the selected household had an average demand of 394 kWh/month. |
