Energy Transfer In Grid-tied PV Systems

Energy Transfer In Grid Connected PV Systems

Solar photovoltaic systems, often called solar PV for short, are made up of several components, the most important being the solar panels, solar inverters, electric meter and cabling infrastructure. Combined, these components harness radiant light from the sun, convert it into electricity and transmit it into homes and businesses to power electrical devices, like lights and appliances, and provide heating and cooling via the electrical currents they create. Here is a general overview of how the energy transfer in solar PV systems work.

  • The sun shines on the solar panels generating DC electricity.
  • The DC electricity is fed into a solar inverter that converts it to AC electricity.
  • The AC electricity is used to power appliances in your home.
  • The bi-directional meter measures electricity moving into and out of the home.
  • Surplus electricity is fed back into the main grid.

Whenever the sun shines (and even in overcast weather), the solar cells generate electricity. The grid connect inverter converts the DC electricity produced by the solar panels into 240V AC electricity, which can then be used by the property/household.

If a grid connect system is producing more power than is being consumed, the surplus is fed into the mains power grid. Some electricity companies will meter the electricity fed into the grid by your system and provide a credit on your bill. How much you are paid is determined by the feed-in tariff.

When the solar cells are not producing power, for example at night, your power is supplied by the mains power grid as usual. The energy retailer charges the usual rate for the power used.


How do solar panels generate electricity ?


A standard solar panel consists of a layer of silicon cells, a metal frame, a glass casing and various wiring to allow current to flow from the silicon cells. Silicon is a nonmetal with conductive properties that allow it to absorb and convert sunlight into electricity. When light interacts with a silicon cell, it causes electrons to be set into motion, which initiates a flow of electric current. This is known as the “photovoltaic effect,” and it describes the general functionality of solar panel technology.

In addition to silicon solar cells, a typical solar panel includes a glass casing that offers durability and protection for the silicon PV cells. Under the glass exterior, the panel has a layer for insulation and a protective back sheet, which protects against heat dissipation and humidity inside the panel. The insulation is important because increases in temperature will lead to a decrease in efficiency, resulting in a lower solar panel performance.

Solar panels have an anti-reflective coating that increases sunlight absorption and allows the silicon cells to receive maximum sunlight exposure. Silicon solar cells are generally manufactured in two cell formations: monocrystalline or polycrystalline. Monocrystalline cells are made up of a single silicon crystal, whereas polycrystalline cells are made up of fragments or shards of silicon. Mono formats provide more room for electrons to move around and thus offer a higher efficiency solar technology than polycrystalline, though they are typically more expensive.


Metering and Rate Arrangements for Grid-Connected Systems 


With a grid-connected system, when your renewable energy system generates more electricity than you can use at that moment, the electricity goes onto the electric grid for your utility to use elsewhere. The Public Utility Regulatory Policy Act of 1978 (PURPA) requires power providers to purchase excess power from grid-connected small renewable energy systems at a rate equal to what it costs the power provider to produce the power itself. Power providers generally implement this requirement through various metering arrangements. Here are the metering arrangements you are likely to encounter:

  • Net purchase and sale — Under this arrangement, two uni-directional meters are installed: one records electricity drawn from the grid, and the other records excess electricity generated and fed back into the grid. You pay retail rate for the electricity you use, and the power provider purchases your excess generation at its avoided cost (wholesale rate). There may be a significant difference between the retail rate you pay and the power provider’s avoided cost.

Understanding Net Metering

  • Net metering — Net metering provides the greatest benefit to you as a consumer. Under this arrangement, a single, bi-directional meter is used to record both electricity you draw from the grid and the excess electricity your system feeds back into the grid. The meter spins forward as you draw electricity, and it spins backward as the excess is fed into the grid. If, at the end of the month, you’ve used more electricity than your system has produced, you pay retail price for that extra electricity. If you’ve produced more than you’ve used, the power provider generally pays you for the extra electricity at its avoided cost. The real benefit of net metering is that the power provider essentially pays you retail price for the electricity you feed back into the grid.


About Green Brilliance


GreenBrilliance is established with the mission to provide solar energy solutions in the DC, MD & VA areas. GreenBrilliance is a vertically integrated; end-to-end Solar Energy Services Company headquartered in the DC metro area delivering turnkey solar EPC solutions to homes, businesses & utility large scale projects at very competitive prices.

As a top-quality EPC provider, we have in-house engineering & design teams, our vertical integration across the value-chain enables us to achieve operational efficiencies leading to cost & time savings for our customers & ensures delivery of superior products at an unmatched value. At GreenBrilliance we realize & appreciate the significance of our role in educating & delivering PV systems to our customers. “An educated customer is the best customer.” We believe in excellent customer service both pre-&-post installation.

GreenBrilliance recently ranked 33rd in the top hundred installers in the world by the list published by the renowned ‘Solar World Online’ with a fantastic portfolio including the prestigious “Ronald Reagan International Airport” in Washington DC.


Core Capabilities & Services:

  • Solar Consultation
  • PV Design & Engineering
  • Permits & Utility Interconnection
  • Operations & Maintenance

Our Expertise :

  • Design & engineering
  • Grid-tied Distributed Solar Systems
  • Off-Grid/Micro Grid Systems
  • Commercial/Utility Scale Systems
  • Solar Storage Systems

Compiled By : Nishanth Mahankali – Solar Design Engineer – GreenBrilliance LLC


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