Grid-connected photovoltaic solar systems allow users to co-generate electricity or inject energy in parallel, either for self-consumption or for dispatch to the interconnected system.
The concept of grid-connected photovoltaic solar systems is compatible with a wide range of applications, which can range from power plants of hundreds of megawatts to small systems of a few kilowatts. The intrinsically modular nature of photovoltaic technology allows, unlike most conventional energy sources, a unit cost that is relatively independent of the size of the installation;
The concept of grid-connected photovoltaic solar systems
In general terms, distributed photovoltaic generators connected to the network can provide significant benefits to distribution systems, depending on the characteristics and operating conditions of the distribution network, as well as their location within it. The most important potential benefits are:
- Modulation of demand peaks when there is a certain degree of coincidence between the photovoltaic generation profile and the consumption profile of the building or feeder.
- Thermal relief for distribution equipment also implies the possibility of postponing capital investments to increase its capacity or replacement.
- Decrease in transmission and distribution losses.
- Voltage support in distribution feeders.
- Reactive power compensation in the feeder.
Characteristics of a grid-connected photovoltaic system
The number of units will depend on the nominal power required in the array and the peak power of the selected modules. The nominal power of the photovoltaic Solar Panels Monument modules or panels is normally between 200 and 450 Wp. The material commonly used in the manufacture of photovoltaic modules or panels is silicon; the typical efficiency of these modules under standard irradiance and temperature conditions (ie, 1,000W/m2, 25°C, AM1. 5) is between 14 and 22% for monocrystalline silicon and polycrystalline silicon; and between 5 and 7% for amorphous silicon.
The conditioning of the electrical power
The efficiency of the inverters is generally greater than 90% when they operate above 10% of their nominal power.
In order to always extract the maximum power available from the photovoltaic array, the inverter incorporates among its functions one or more control elements that permanently follow the maximum power point of the array (MPPT, for its acronym in English) by continuously adjusting the impedance of the load.
In relation to the safety and quality aspects of the energy produced, the electricity service supply companies require the manufacturers and users of this equipment to comply with applicable standards and provisions that guarantee that the installation and operation of the inverter, and of the system as a whole, is safe and does not adversely affect power quality.
Design of photovoltaic solar systems connected to the network
The program generates a file where the monthly values of horizontal and inclined radiation, and ambient temperature, among others, are specified.
The expression of the simplified equation is as follows:
Where:
- Pm is the maximum power of the generator under the desired conditions of irradiance G and cell temperature Tc.
- Grief is the irradiance at reference conditions.
- ref is the cell temperature at reference conditions.
- γ is the coefficient of variation of the maximum power point with temperature.
Where:
- Tc is the cell temperature.
- Ta is the ambient temperature.
- TONC is the Nominal Operating Temperature of the photovoltaic module.
- G is the irradiation.
The following losses must be considered in the installation:
- angular losses
- Non-monitoring of the PMP
Inverter sizing
To size the inverter, we start from the power of the generator and then obtain the sizing factor FS.
Generator sizing
The dimensioning starts by analyzing the necessary surface and the suitable surface for the purpose.
Actuality and feasibility
Grid-connected solar systems have now achieved profitability for most applications. The costs of its components have come down in recent years, which allows obtaining returns on investment of fewer than 2 years for places with electricity costs greater than 20 cents on the dollar.
In Ecuador, these types of systems are already profitable and have returns that range from 1.5 years to 7 years, depending on the type of customer rate.
In order to determine the feasibility of implementing a grid-connected solar system, RENOVAENERGIA has developed a spreadsheet tool that allows the user to determine the size of the ideal grid-connected solar system, as well as the cost. estimate of the same and the return time of the investment, comparing the energy that will not be consumed from the electrical network by the rate that should have been paid for that number of self-generated kWh.
