One promising and ever-evolving technology is photovoltaic systems that can generate electricity, drawing on solar energy like solar systems. Solar cells, commonly called photovoltaic cells (semiconductors), are "devices" that convert solar energy directly into electricity through the photovoltaic effect. The operation of photovoltaic systems is based on the fact that solar radiation can change the properties of certain materials (semiconductors) by generating electricity through the "photovoltaic effect". In the photovoltaic effect, the sunlight falling on a semiconductor of two layers creates electrical potential between them. This voltage can actuate a voltage and power proportional device or be distributed to the electrical system. The set of photovoltaic elements connected electronically to each other is called a photovoltaic generator and the set of photovoltaic generators connected to each other is called a photovoltaic array. The photovoltaic array is the most important part of the photovoltaic system and is accompanied by appropriate electronic circuits for controlling and managing the energy produced, as well as a storage system (batteries). The electricity produced is continuous voltage and depending on the application can be converted to alternator with the help of a voltage inverter. The efficiency of photovoltaic systems is increased by the use of frame rotation systems that follow the sun, however the installation of such systems can significantly increase the cost of investment. Ongoing technological developments in the field aim to maximize the efficiency of these systems and at the same time reduce the cost of the generated kilowatt-hour in order to make photovoltaic systems one of the most important technologies for solar energy exploitation in the near future.
In the last decade, the majority of photovoltaic stations in Greece are feed in tariffs. This is due to the very encouraging subsidies provided to date by the state and the EU. either by subsidizing the initial capital or the price of electricity sold by the individual. Consequently, the installation of a solar power station, in addition to its significant environmental benefits, as it exploits a renewable energy source (solar), is a guaranteed and efficient investment.
In these systems we have a set-off of energy accounting (the indications of the two meters are converted into money and deducted from each other, the difference being credited to the consumer). Photovoltaic systems are mainly installed in domestic consumers, in craft industries or in parcels. In the past decade, the vast majority of photovoltaic systems installed in Greece were in plots. However, in recent years, mainly after July 2009, when the Ministerial Decision on Home Photovoltaics on Roofs and Roofs was adopted, more and more home consumers are installing them in their homes.
This shift in home systems is due, on the one hand, to the subsidy on the price of electricity produced, and to the fact that income is tax-free and guaranteed for 25 years, and on the other to the fall in the price of photovoltaic panels which has made the investment particularly attractive and affordable. . Suffice it to say that with a capital of around € 13,000 a household can secure up to € 2,000 annually tax-free income guaranteed for 25 years. The maximum limit for a home system is 10kWp and set off at a rate of 0.12 € / kWh (Fall 2014). Larger parcel systems have enjoyed lower tariffs but due to economies of scale the return on investment is excellent. Even with the new reduced tariffs, the return on a photovoltaic roof investment yields less than 7 years of initial capital.
Since September 2023, the net billing system (synchronous energy netting) has replaced the net metering system (energy netting).
With net billing, the generated energy is consumed directly. The excess energy is used to charge the battery. Once the battery is charged, the excess energy is fed into the grid, which buys this energy at the wholesale price that applies at that time.
If the consumption needs are greater than the energy produced at that time (e.g. at night when there is no sun), the energy stored in the battery is used. If the stored energy is not sufficient, energy is absorbed from the grid.
❌Net Metering: The excess energy was stored in the grid for future use. However, it was subject to a double transmission grid charge (€0.06/kWh when channeled and €0.06/kWh when absorbed), totaling €0.12/kWh.
👉Net Billing: Surplus energy is sold to the grid at a wholesale price (average ~0.075€/kWh).
🎯Instead of being charged for using the grid as a “storage”, you are paid for the energy you pump in. Note that the energy you absorb from the grid is now charged at the retail price, plus the cost of transmission.
❌Net Metering: There was no technical possibility of exporting the stored energy from the battery to the grid.
👉Net Billing: The possibility of channeling energy from the batteries to the grid is now provided.
🎯This is a strategic advantage, as the wholesale price of a kilowatt-hour during the night can be up to 3 times higher than during the day. Storing energy during the day and selling it at night creates significant surplus value.
❌ Net Metering: There was only the possibility of offsetting with one utility, which had to be physically connected to the system
👉 Net Billing: The possibility of offsetting with multiple utilities is provided, as long as they are in the same network, anywhere in the country.
🎯Virtual net billing: The system is not physically connected to any utility but channels all the generated and stored energy into the grid. The grid performs simultaneous offsetting, i.e. it offsets the energy consumed by all connected utilities with the simultaneous production from the system.
This gives a great advantage for offsetting with utilities that do not have the ability to install a PV system to exploit the production of a system installed in another location (e.g. in a country house).
✅Investing in Batteries: With Net Billing, the strategy shifts. Investing in battery capacity is now more cost-effective than simply adding photovoltaic panels.
⏳Payback: With proper system sizing, you achieve a payback on your investment in just 5 - 6 years.
🚀Profit strategy: By taking advantage of the price difference between day (charging) and night (selling), the system is self-financing much faster than traditional systems, ensuring higher net profitability over time.
🏠 Space: Just 25 sq m of roof or pergola is enough to fully cover the needs of a typical household.
💰Cost: The cost of a complete PV system that meets your needs is less than the cost of a used car.
Stand-alone systems provide electricity without interconnection with the electricity grid. They receive the energy from the sun with the help of photovoltaic panels (or wind turbine - wind) and pass it on to the batteries. From there the energy is distributed to the electrical loads after being converted into a suitable form by a voltage inverter (DC to AC). Autonomous systems are mainly used in buildings that do not have PPC such as cottages, caravans, mobile homes, cottages that are either illegally constructed or are away from the public network.
Many times depending on location and wind power there is a power generator and the system is called a hybrid, and very often a battery charger is added to charge with the help of a liquid fuel generator. In addition to the panels, an important part of such a system is the charge controller that controls the charge and discharge of batteries and batteries.
The design and installation of a standalone system is extremely demanding and it is suggested that an experienced engineer be selected for their development. The calculation of a system of autonomy consists mainly of a good record of the user 's consumption with particular attention to the seasonal period of maximum use and how the building operates. Battery selection is perhaps the most critical part of designing a standalone system as they have a finite life span which varies considerably depending on the type and quality of the battery. So there are two major categories of closed and open type batteries. The former have shorter life spans (3-5 years) but do not require maintenance while the latter longer life spans (5-15 years) are more demanding in maintenance.
Depreciation of a stand-alone photovoltaic can be done even from the first day of operation, in cases where the cost of interconnection with PPC for example exceeds 50,000 € and a stand-alone photovoltaic system costs 40,000 € not only the user wins the fixed assets but also the original interconnection costs.
234 Petrou Rally Ave. Nikea, Greece
Email: info@hellasnrg.gr Telephone: (+30) 210 4910550
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