Integrated Autonomous Photovoltaic Systems
For installations that do not have direct access to the PPC network, there is the solution of autonomous and hybrid systems.
Stand-alone photovoltaic systems (or off-grid systems) are designed to provide energy autonomy to an installation. There are several categories of off-grid PV systems. Some of them are:
- Houses remote from the grid at such a distance that the cost of interconnection with the PPC network is prohibitively high.
- Houses that for some reasons cannot be electrified
- Livestock or agricultural units remote from the PPC network
- Telecommunications facilities
- Water supply pumping systems
- Mobile facilities (caravans, floating etc.)
- Installations requiring high availability (defence applications, space applications)
The methodology for electrifying such an installation is as follows:
Analysis of the area (radiation, shading, etc.)
First of all, the solar radiation in the area should be calculated for the whole year and in some cases by month of the year. In contrast to interconnected systems where the objective is the maximum annual energy gain, in isolated systems there are applications where the energy needs are higher in some specific months of the year or even at some specific times of the day.
For example, in the region of Kavala, the optimal inclination of the photovoltaic panels in relation to the horizontal plane for a system based on maximum annual electricity production is 31o. However, if we want to electrify a holiday home only for the summer months the optimal inclination is from 5 to 20 degrees depending on the month of maximum energy demand. Another issue is also the place where the photovoltaic panels will be placed.
Recording of energy requirements
Each installation has different loads (devices, machines, etc.). In order to make a proper design, all loads should be recorded, as well as a detailed description of the duration of use of each device and the desired autonomy time.
The autonomy duration will also determine the sizing of the batteries to be used. Also very important is the type of devices used, whether they consume AC or DC power. In most cases, low energy consumption devices are recommended, which have a higher purchase cost but are certainly more advantageous in the long run.
In addition, there is the possibility of combining photovoltaics with another energy source, such as wind turbines or diesel engines. In this case, various combinations can be made in the resulting hybrid system in terms of the participation of each energy source and their sizing.
Economic and technical study
After the analysis of the above technical characteristics, the economic and technical study of the installation follows. This study is the combination of the above technical requirements, the economic feasibility and possible subsidies. The aim is ultimately to achieve the optimum technical and economic solution.