In accordance with the assessments of the EU, about several billion people worldwide have no access to the public grid and half of them live in areas completely without electricity. High prices for investments, combined with low energy requirements (less than 1 kWh per day) make ineffective the development of the grid to cover so sparsely populated areas in inland areas. Even in Europe, the EU recognizes that 300,000 farms and homes are not connected to the grid (about 70,000 of them in Italy and 20,000 in France). In these cases is mainly consumed from 3 to 20 kWh each day. The requirements for comfort, safety and performance level of the power supply vary among regions, economic conditions and experience with the consumption of electricity. Thus in planning and dimensioning of power grids beyond the basic need to be taken into account certain factors.
Photovoltaics are one of the most interesting technical solutions to solve this energy problem. But the painful experience of many pilot projects has shown that it is necessary to take into account all the circumstances when planning such equipment. In addition to the technical conditions there are cultural, social, economic and financial aspects. At the same time by using photovoltaics can be improved other crucial elements of people’s lives as loading food and water or health and educational infrastructure in addition to clean energy supply so that the living standard of the population without access to the grid to be significantly improved.
The replacement of “only” 100 million from kerosene lamps with solar lighting systems (solar generator with a capacity of about 5 W is needed to replace a lamp) will generate income of about 2 to 3 million Euro only from photovoltaics compared with the consumption of petroleum which is expensive, environmentally harmful and sometimes difficult to achieve.
For supplying electricity to remote areas through photovoltaics there are four key concepts:
- Small, portable solar lamps;
- photovoltaic station for charging batteries which provide individual homes (used only in developing countries);
- independent power systems for individual homes – autonomous photovoltaic systems to provide main power supply;
- power systems for a large number of houses or local mini-grid (“urban grid”) and a district energy supply system with photovoltaic generator and a hybrid concept of supply;
Currently, there are specialized programs anywhere in the world, including Bolivia, China, India, South Africa and Morocco in order to represent the spread of these technologies. The ease of use of autonomous photovoltaic systems in sparsely populated areas without grid access is considered particularly their advantage. Unlike centralized systems, the families themselves can manage their individual autonomous systems. For the households this makes easier the access to electricity compared with the concept of centralized power.
A simple autonomous photovoltaic system for electricity consists the following components: photovoltaic generator, battery, charge controller and directly related constant-current consumers.
The charge regulator connects the photovoltaic module to the battery and power consumers. It protects the battery from overcharging and excessive discharge – two conditions that reduce its life cycle. When working the charge regulator affects the functions of the autonomic system when it reach the limit. The high requirements placed on all components of the system means that the regulator and the charge should be of very high quality too.
The size of the photovoltaic module and battery is based on the calculated energy consumption. A new battery must have sufficient capacity to cover the needs of at least 5 days of average consumption of electricity.
The size of the photovoltaic module must be pursuant with the energy consumption and solar irradiation in the last favorable month of the year.
The dimensioning of the system must be based on accurate determination of previous and actual energy consumption. This is how need to be determine the connected load of all used devices, the average time of operation and frequency of their use. Manufacturers of electrical appliances are required to use euro tags – classes from A to G to show the energy consumption of their products. Such with an indication A are very effective while G consume more energy.
Each technical system requires regular maintenance and photovoltaics are no exception. The check may be carried out by trained personnel with professional qualification for photovoltaic systems mechanic. In addition, there are maintenance costs of electro-mechanical generators, engines (e.g oil change every 100-200 hours of operation). These costs are higher compared to the maintenance costs of the photovoltaic system.