Inverters are a crucial part of any solar system installation – be it off-grid or on-grid. But there are many questions which surround them – how does solar inverter work, why is it important, what types of solar inverters are there in the market and how much do they cost. This blog answers all these questions.
1) How does a Solar Inverter Work?
The job of an inverter is to invert – it takes DC (Direct Current) and converts it into AC (Alternating Current). Solar inverter also does that. When sunlight falls on solar panels, they generate DC electricity. However we can’t use this DC electricity directly to power our electrical equipment and appliances like fans, lights, refrigerators, AC, heaters, etc. because all these appliances are designed to run on AC. The solar inverter takes DC from solar panels and converts it into AC so that you can run your electrical load.
This example explains the importance of solar inverter very well: We all know that we need minerals like Iron, potassium, calcium etc. These minerals are in the soil in good quantities but can you eat soil? No! Our bodies can’t digest soil. Plants take these nutrients from the soil (besides air, water and sunlight) and convert them into fruit which can eat and enjoy. Similarly solar inverters take DC and convert it into AC because our electrical appliances can’t run directly on DC – they need AC.
Now you must be wondering why not DC, why AC? The Alternating Current (AC) is much safer compared to Direct Current (DC) and the loss of energy in transmitting this current to far off areas is also lesser in case of AC.
3) What types of solar inverters are available in India?
Solar Power Conditioning Unit: Solar PCUs are usually installed with off-grid solar installations. It is an all-in-one unit which has in-built solar charge-controller, inverter and charger, and is connected to a battery bank. It converts the DC electricity generated by panels in to AC and feeds it to the main electrical outlet of the house to run connected load. The extra energy gets stored in batteries to power the load in absence of sun. It also comes with an advanced monitoring software which allows you to measure its performance i.e. units of electricity generated, output waveform, charging current etc.
Solar Grid-tie Inverter: As the name suggests, these inverters are connected to grid and are used for on-grid installations. They convert DC from solar into AC and power the connected load. The surplus energy generated can be fed back to the grid if the state has provision for this. States where net-metering has been implemented, you can get paid for feeding the grid depending on back-back tariff set by the state Government. While grid-tie system are easy to install and maintain because they are battery-less, they cannot operate in absence of grid.
Solar Hybrid Inverter: This is the latest offering in India’s solar market. Solar hybrid inverters can function both as ordinary inverters and solar inverters because they can operate on grid as well as solar power. When sun is up and panels generate DC electricity, it charges the batteries through solar power and when the batteries are fully charged, it disconnects itself from the main grid to power the house with solar energy stored in batteries. If the panels are not making enough power to charge the batteries then it takes remaining voltage and current from the grid to make sure that the batteries get charged. During evenings and period of no sunshine, it functions like an ordinary inverter and charges batteries through grid.
4) How Much Do Solar Inverters Cost in India?
The price of solar inverter depends on its type and size. A solar PCU of 1000 VA may cost up to Rs.10,000. A 1 kva on-grid inverter could be prized between Rs. 15,000 and Rs. 20,000. A solar hybrid inverter for home is more economical and costs only Rs. 2,000 more than ordinary home inverter.
5) How Long Do Solar Inverters Last?
The life of solar inverters is usually very long. A good branded solar inverter if maintained properly can last more than 10 years.
6) How to Decide the Size of Solar Inverter to match Solar Panels?
Size of the solar inverters depends on the connected load. It is better to keep at least 25% higher capacity of inverter than that of the total power ratings of connected load. Battery sizing depends on the depth of discharge and backup time required to run the connected load in absence of the solar energy or other source of energy (Grid/DG).
If the total wattage from solar panels is 1000W or 1kw then you need an inverter of typical ratings of 1000W/1250VA (0.8pf) and a battery bank of 300Ah/24V (7200VAh) capacity.