By Siddharth Gangal and Aarushi Dave
What is Solar Energy really?
Simply speaking, it is energy from the sun. This energy is, in the form of photons and can be used to generate electricity using photovoltaic cells.
Using a solar system installation, this energy can be harnessed and used to power your home, office or just any place that needs it! With dropping costs and innovative technologies being developed, solar power will soon account for satisfying a large percentage of energy demands of India.
So what’s a solar energy system made of?
A solar energy system is installed in a premise to generate power using solar irradiance. You might know primarily of photovoltaic panels, popularly known as ‘solar panels’. But that’s not all! Here’s a complete list of the components of a solar system that you need to be familiar with before installation:
- Solar Panels: These are also called photovoltaic panels; they convert solar radiation into usable electricity. The most prominent part of the solar system, they are present on the roof of the building.
To further understand how panels function, here are the details:
1.Material: The major component of the panels is silicon. N-type or P-type silicon is created using a process called ‘doping’. These two types of charged silicon are placed together to form a photovoltaic cell and several such cells are connected in series to form a panel.
Most panels are two kinds: polycrystalline or monocrystalline.
2. Power Generation: The silicon cells in panels absorb energy in the form of photons from solar radiation. Electricity is generated as DC current when these electrons travel through the circuits in the solar cells.
3. DC to AC difference: Electrons traveling through the solar cell generate DC or direct current. However, for household and office use AC or alternate current is needed. Hence, inverters are needed to convert this produced DC power to AC power.
Solar panels are the lifeline of a solar photovoltaic system. They convert sunlight into electrical energy. It is important to make sure you install good quality solar panels. Not all panels are built the same. Make sure that the solar panels you purchase follow the IEC 61215 test.
- Arrays and Array DC Disconnect:
Arrays are a group of panels connected to each other in a series configuration. The size of the array may range from 5 to 100 depending on the size of the solar system being installed.
An Array DC Disconnect is installed. It disconnects the array from the inverter for any maintenance, replacement or upkeep work.
- Inverters: When solar panels generate energy from the sun’s rays, it is in the form of DC (Direct Current) electricity. However, homes and offices run on AC (Alternate Current) electricity. Inverters are used to change the DC power produced in the panels to AC power, that’s actually useful.
Inverters are of the following types:
1.String (or centralized) inverter: The entire array of solar panels is connected by ‘strings’, which is connected to a single inverter. This is the most cost efficient. However, poor performance by even one panel in the entire string affects the overall performance of the entire system. This may even happen due to temporary shading on even one panel. Hence it is imperative to make sure a proper shading analysis is done by the solar installer. Typically, string inverters can be used for any roof.
2. Micro-inverters: One of each of these is installed at each solar panel. This enables them to maximise production, because even if a particular panel is in a different direction or experiencing shading, the performance of the whole string is not affected. Cost of micro-inverters however is much higher than that of string inverter.
3. Power optimizers: Cross between string inverter and micro-inverter systems. Similar to micro-inverters, power optimizers are installed at each panel. However, instead of converting the DC electricity from the solar panels into AC electricity, the optimizers “condition” the DC electricity before sending it to a centralized inverter. Like micro-inverters, they help when problems such as shading or facing different directions occurs in individual panels. While this system is cheaper than micro inverters, it is also costlier than string inverter.
Batteries – yes or no?
Normally, batteries are not required in solar systems connected to the electricity grid due to net metering policies by the government. However, if you live in an area of frequent power cuts, you will need to have batteries. Let us see how:
- Batteries: Solar power is generated in the day but homes and workplaces consume maximum energy at night. This shortfall is overcome by storing the excess generated power into batteries, which is used on-site when the panels are not producing power, such as night time. Batteries have their disadvantages as they can be expensive, and problematic with maintaining and disposal.
- Net metering: An alternative to batteries is net metering. Net metering relies on a special type of meter called a ‘net meter’ which runs backwards when excess solar electricity is fed into the grid and forward (normally) when electricity is drawn from the grid. Electricity is billed on net units consumed, and not the time electricity is consumed at. Hence, you can consider the electricity grid an infinite personal battery where you can put and take solar energy at your convenience!
India has some of the most favourable net metering policies in the world. Electricity is metered on the total number of units consumed and not the time energy is consumed. Hence, even if you do not consume solar energy generated during the day, it will be transferred into the grid and will offset your evening and night consumption.
- Racking mounting systems: Panels can be mounted into arrays in 3 ways:
1. On roof: Most common, an approach which is aesthetic and efficient. While the panels might not much maintenance, mounting it on the roof, especially a high one, might make access for cleaning or repairing systems can be a challenge. It may be needed according zoning ordinances.
2. On poles in free standing arrays: Compared to roof arrays maintenance is easier due to suitable height. However, these take up extra space.
3.Ground mounting: Simpler and easier to access as they’re lower in height. But space might be a concern for directly mounting arrays on the ground. Should not be used for arrays with regular accumulation of snow.
In all of the following mounting systems, the arrays mounts could be of two types:
1.Fixed: The panels are stationary and are pre-set for a particular height and angle. Fixed mounting system is mandatory if the array is attached to the rooftop. While they may not give the optimum angles for output, they’re cheaper and less complicated to install.
2. Moving or Tracking: These arrays literally move with the sun and set their angle according to the movements of the sun i.e. they track the sun. They adjust themselves to move from east to west (single axis mounts), through changing seasons (dual axis mounts). They are more expensive but slightly more efficient. These are not used for rooftop solar and are more suitable for large ground mounted solar plants due to higher maintenance requirements.
- Performance monitoring systems: They give you information on your installed solar system’s performance. Monitoring systems can help you and your solar installer identify any unexpected problem affecting the performance of your system and fix them. Hence, it is beneficial for obtaining expected energy output and hence, a strong financial return.
Types of Monitoring Systems:
1.On-site monitoring: Electricity generation recorded from monitoring device which is actually present in your site of installation. Most inverters have a screen where basic data is available.
2.Remote monitoring: Electricity generation data recorded and transmitted to a monitoring service that you can access remotely. This is required to get much more insights on what problems might occur. Remote monitoring makes automatic diagnostics possible using latest data analytics techniques.
- Charge Controller/Regulator: Prevents batteries from being over charged.
Solar panels have a manufacturer’s warranty of 25 years. Inverters have manufacturer warranties of 5-10 years, depending on the brand of inverter. Other components are typically not covered by warranty and the solar company is in charge of making sure of replacements in case things go wrong.