Solar energy is green energy that directly generates electricity from sunlight. So, it’s pretty evident that the amount of power generated dramatically depends on the amount of sunlight, which varies in different weather and times of the day.
Sometimes the supply is somehow less than the demand, and the other days the supply exceeds the demand. So, to feed the demand continuously (and also keep an eye that the excess energy doesn’t get wasted), we have to maintain some procedures.
We need to save the extra energy generated on a hot sunny morning and get energy compensation when the PV system doesn’t generate power according to the need. Let’s see how we can save the excess energy while maintaining the demand-supply chain intact.
Do Residential Solar Panels Send Power Back?
For domestic usage, solar panels are installed on the rooftop of every house. Most of the systems are now grid-tied, which means it’s always a locality that uses solar panels to power the households.
The inverters in the grid-connected systems typically put the solar energy onto the grid at a slightly high voltage. It becomes easier for the grid to “sense” the surplus energy. The excess current flows out from the house to the local central network.
But one thing we need to keep in mind is that the transmission of solar electricity is not as efficient as the transmission of the convenient kind of electricity. This can only be transmitted locally.
So, your PV system’s excess energy is going nowhere but to your neighbor. There is generally one local electricity distribution network. The surplus power is sent back to the distribution network, and then it is supplied to the same neighborhood where it is needed. There isn’t any high-voltage transmission network, so it can’t be supplied to faraway places.
But not all PV systems are grid-connected, and some are stand-alone systems.
These systems don’t send power to any grid, and they store the surplus energy in the batteries to use later when the amount of power generated can’t power up the whole household (demand is more than the supply).
What is an On-Grid System?
The on-grid system is a system in which the solar panels installed in a house is connected to the utility power grid. There are off-grid systems, too, that are often called stand-alone systems, and they aren’t connected to grids.
Off-grid systems need expensive solar batteries to store surplus energy. But in on-grid systems, the surplus energy flows back to the grid, and the consumer gets compensated.
The consumer can even sell the excess energy to their neighborhood. They don’t need any battery backup. On-grid systems are getting popular as it’s more economical than off-grid ones as they are more economical.
The requirement of battery, grid box, inverter, charge controllers, and many other components makes the off-grid system much more expensive. But for “live” electricity generation and supply, on-grid systems are undoubtedly better options.
How do we Send Power Back to the Grid?
As we all know, solar modules are illuminated by sunlight, converting them into electricity, and it generates DC, which is later converted to AC. A solar inverter does this task.
Then it is supplied to electrical equipment and gadgets to power up them. Now here, the path is being divided. One path is connecting the inverter and the electrical equipment that needs to be powered up (In general, the main switchboard of the household).
The other path connects the net meter to the inverter, and the net meter is directly connected to the grid. The electricity is then routed to the grid, and the surplus electricity is supplied there for day-to-day use. One “net meter” is attached to it, which records the energy supplied to the grid and the energy consumed by the consumer.
It also calculates a bill that a consumer should pay for drawing electricity from the grid. So, the consumer has only to pay for the surplus electricity they consume.
If they haven’t drawn any extra current their system has produced, they don’t have to pay. Also, if the consumer’s system has produced any excess electricity, they can charge for that. That means the consumer can have cost benefits too.
For example, suppose your PV system can generate a maximum of 20kW power, and you need 10kW to light up your whole household. On a sunny clear day, it generates no less than 20kW.
The household uses 10kW. The extra 10kW flows through the second path (inverter to the grid via net meter). This excess power is fed back to the grid. But suppose on a cloudy or rainy day, your PV system cannot generate that much, and it’s just able to generate 7kW.
But your household’s need is the same (10kW). So your household draws 3kW from the grid to keep the supply consistent. The net meter keeps track of the power drawn and power fed back for a whole month. And then, the power provider generates a bill according to that.
What Equipment do we need for On-grid Solar System?
For safe electricity transmission and to comply with the power provider’s grid connection requirements, we may need additional equipment like power conditioning equipment, safety equipment, meters, and instrumentation.
Power conditioning equipment consists of four essential elements, i.e., conversion of DC to AC, frequency of AC 60 cycles per second, voltage consistency, and quality of AC sine curve (preferred smooth). Simple electric devices can run on low-quality electricity, i.e., jagged sine curve of AC and even fluctuating voltage.
But when it comes to heavy load electric devices, it’s crucial to maintain voltage consistency and a smooth AC curve as they are more sensitive. For sensitive gadgets/devices, low-quality electricity can damage them or shorten their lifetime. Like, computers, televisions can’t bear much power distortion, but gadgets like light bulbs, fans, and hairdryers run fairly with low-quality electricity.
One needs an inverter for the generated/supplied electricity to match the requirements of the load. It conditions the quality of electricity for the well-being of your electrical devices.
It should match the voltage, phase, frequency, and wave profile of the AC curve generated by the system to that flowing through the grid. So, one should plan about all future requirements of devices (additional loads to the system) while fitting an inverter to the system (well, it’s cheaper to purchase an inverter of larger input and output rating than to have several small input ones).
Safety equipment is needed to protect the system and the loads connected from being damaged and creating any mishap during lightning, power surges, or any malfunction of any part of the system. It includes safety disconnect, grounding equipment, surge protection, etc. Safety disconnect ensures the PV system is isolated from the grid while people work on the grid for maintenance and repair, ensuring the safety of the people working.
Grounding equipment provides safety for the devices while they are malfunctioning or in the case of a short circuit in the wiring. This well-defined, low resistance path (lower than usual wiring) passes the extra harmful amount of electricity to the ground/earth. It also provides safety from lightning strikes. Every exposed metal body of electric devices or maybe any part of the whole system that any person can touch should be grounded.
Meters and other instruments help to monitor the usage of the system, i.e., the power consumption and the supply voltage, etc. For a grid-tied system, the consumer has to keep track of both electricity consumed and the power that is fed back to the grid. One can use two separate meters for these two purposes (If the power provider doesn’t allow a net-metering arrangement).
But if the power provider allows keeping a net meter, it’s the best option to track. It’s a single bi-directional meter to track both usage and production. The net meter spins forward when the consumer draws electricity from the grid and spins backward when the consumer’s system feeds back to the grid.
Other Requirements for On-grid Solar System
Power providers sometimes face very common problems while connecting small solar PV systems to the grid. So safety and power quality regulations are needed. There are some very specific requirements. Power provider individuals or state utilities commission deal with grid connection requests, and they make clear the system-specific requirements to the consumer.
Also, the consumer needs to sign an interconnection agreement with the power provider. The deal includes carrying liability insurance. The insurance protects the grid from any accident caused by the consumer’s system.
Also, some providers require indemnification for any potential damage, loss, or injury caused by a consumer’s PV system, and it can be suspiciously expensive. There can be permitting fees, inspection fees, metering charges, etc.
There’s no doubt that solar energy can be a great financial investment, and it’s more about the savings rather than making money from it. Some large solar developing companies make money by installing solar panels in some leased properties and selling the power generated back to the property owner. But for an average solar investor, this is not the way.
But, there are policies for the utility companies to compensate for the surplus energy your PV system generates, in the case of a grid-tied solar system. Using the on-grid solar system to generate electricity, the consumer can reduce the electricity bill and sell it to the grid.
When you send power back to the grid, it is saved as “credits.” One can sell “credits” to get free “credits” when they need them. It’s more like a free way to store your surplus energy. And also you can sell it in exchange for money. The utility companies will pay a nominal or wholesale price.
As I previously said, “net-metering” tracks it all. So first, you need to know your requirements for energy in your house. Then you need to install a PV system that typically generates more than your requirement. After installing, you need to make one “net metering agreement” with the utility company.
The rules and rates of selling electricity to the grid vary from state to state, country to country. There are regulations on how much a consumer can sell to prevent people from fleecing the utility companies.
But, not all the states have the facility of net metering. Some states don’t require net metering policies, and some of those states have their implementations or programs that are somehow similar to the functioning of a net meter.
Here the compensation may not be a kWh for a kWh, and the power generation charge maybe (The energy fed back to the grid by the consumer is worth less than that in a state with net metering policies).
Besides all these, there are tax benefits too. Various incentives and tax credits accelerated depreciation for business, regional grants, and credits. Sometimes the installation cost can be cut down to a considerable amount too.
So, in conclusion, we can send the excess power back to the grid. It doesn’t take much, but it has so many benefits. Nowadays, the on-grid solar system is more popular than the off-grid one.
Though the off-grid systems are stand-alone units and need no power provider, grids are always better if you talk about cost benefits. Also, off-grid systems require much more equipment to be completely self-supported.
Anyway, in the case of on-grid systems, it’s not always about the money you can make. But the facility of sending the excess power back ensures free storage of surplus energy, just like a battery. But in this case, it’s not a “physical” battery, and that’s why it needs no maintenance. The whole on-grid solar system runs on a shallow need of maintenance.