Serbia: Standalone photovoltaic system with energy storage

8. July 2016. / News Serbia Energy

In rural areas without a power network and adequate infrastructure, photovoltaic systems are more cost-effective solution than bringing the network to the consumer. Standalone photovoltaic systems can be very cost effective in remote places where the only alternative is to use generators creating high noise levels, requiring maintenance, characterised by a relatively high and expensive fuel consumption, coupled with adverse environmental impacts. With the progress of technology, photovoltaic panels are more efficient and cheaper, and their use more profitable.

Standalone photovoltaic systems are not connected to the power network, wherefore they need to store energy to make it available at times when there is not enough sunlight. The priority of such a system is a safe and reliable delivery of electricity to the consumer. The paper entitled Standalone Photovoltaic System with Energy Storage based on Potential Water Energy by I. Mitic and J. Mikulovic, examines the sizing of a standalone photovoltaic system with energy storage used to supply a household far from the distribution network. Photovoltaic systems generate energy when there is solar radiation, i.e. in periods with favourable insolation. Water can be used to store energy. Surplus energy during periods of the day with higher insolation can be stored and used to raise water to a higher level, while during the night when insolation conditions are adverse water pumped in the top tank is released through the turbine, thus generating electricity. The aim of this study is to compare a standalone photovoltaic system using batteries to store energy and a system storing energy in water tanks. The paper deals also with the demand management aspects. In an isolated system, consumption should be adapted to electricity generation levels, i.e. to solar radiation levels during the day.

It was concluded that for a standalone photovoltaic system with lead storage batteries and without demand management, substantially more modules – 34 are required instead of 13 which are required for a photovoltaic system with a water tank used for energy storage and demand management, projected on the basis of mean consumption diagrams. A significant difference in the number of modules was established, as well as in the volume of the storage tank in the case of a photovoltaic system with a water tank used to store energy and without demand management. Without demand management, 21 module is required while the tank volume is almost two times higher. The good aspects of demand management are that energy is used when it is gradual, and at night and under adverse insolation conditions only the necessary amounts are consumed, while generation is adjusted accordingly.

The downside of the system using energy storage based on water potential is that it requires major water tank investments. However, the cost of batteries is significant, since it was established that a standalone photovoltaic system needs 52 batteries which need to be replaced after 10 years.

By employing an energy storage system based on the potential water energy disadvantages of existing systems with rechargeable batteries are eliminated, as there is no need for replacements. However, it should be noted that energy storage systems based on potential water energy contain moving parts prone to failure, and that the initial investment into the system is higher, transmits

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